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  • 51.
    Carlson, Annika
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Tillämpad elektrokemi.
    Shapturenka, Pavel
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Tillämpad elektrokemi.
    Eriksson, Björn
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Tillämpad elektrokemi.
    Lagergren, Carina
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Tillämpad elektrokemi.
    Wreland Lindström, Rakel
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Tillämpad elektrokemi.
    Electrode parameters and operating conditions influencing the performance of anion exchange membrane fuel cells2018Inngår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 277, s. 151-160Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A deeper understanding of porous electrode preparation and performance losses is necessary to advance the anion exchange membrane fuel cell (AEMFC) technology. This study has investigated the performance losses at 50 °C for varied: Tokuyama AS-4 ionomer content in the catalyst layer, Pt/C loading and catalyst layer thickness at the anode and cathode, relative humidity, and anode catalyst. The prepared gas diffusion electrodes in the interval of ionomer-to-Pt/C weight ratio of 0.4–0.8 or 29–44 wt% ionomer content show the highest performance. Varying the loading and catalyst layer thickness simultaneously shows that both the cathode and the anode influence the cell performance. The effects of the two electrodes are shown to vary with current density and this is assumed to be due to non-uniform current distribution throughout the electrodes. Further, lowering the relative humidity at the anode and cathode separately shows small performance losses for both electrodes that could be related to lowered ionomer conductivity. Continued studies are needed to optimize, and understand limitations of, each of the two electrodes to obtain improved cell performance.

  • 52. Castro, A.
    et al.
    Vilaplana, Francisco
    KTH, Skolan för bioteknologi (BIO), Glykovetenskap.
    Nilsson, L.
    Characterization of a water soluble, hyperbranched arabinogalactan from yacon (Smallanthus sonchifolius) roots2017Inngår i: Food Chemistry, ISSN 0308-8146, E-ISSN 1873-7072, Vol. 223, s. 76-81Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Yacon (Smallanthus sonchifolius Poepp. & Endl.) roots are largely grown in Andean countries and have attracted recent interest due to their antioxidant and prebiotic effects. Yacon is typically consumed as a fruit due to its sweet taste and juiciness. The macromolecular properties of an aqueous extract of yacon are investigated using asymmetric flow field-flow fractionation (AF4) coupled to UV, multiangle light scattering (MALS) and differential refractive index (dRI) detection. The method allows for determination of molar mass and size over the size distribution. Three major populations were found of which one strongly dominates in concentration. Through collection of fractions from AF4, carbohydrate composition and glycosidic linkage analysis for the dominating population was performed. The results show that the dominating population consists of a highly branched arabinogalactan (type 2) with a molar mass of approximately 1–2 · 105 g/mol, a hydrodynamic radius of approximately 6–10 nm and a relatively high apparent density (approx. 70–150 kg/m3).

  • 53.
    Cedervall, Johan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström.
    Synthesis and characterizationof rare earth free magnetic materialsfor permanent magnet applications2013Independent thesis Basic level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    In this thesis the compounds Fe5SiB2 and Fe5PB2 have beensynthesized via high temperature synthesis, including arc melting anddrop synthesis. The structure for both compounds are of Cr5B3 typewith the space group I4/mcm. The cell parameters were refined toa = 5.5533 Å and c = 10.3405 Å for Fe5SiB2 and a = 5.4903 Å andc = 10.3527 Å for Fe5PB2. The saturation magnetization at roomtemperature for Fe5SiB2 has been measured to 138.8 Am2/kg and theanisotropy constant has been estimated to 79 kJ/m3. Theferromagnetic properties and the high anisotropy constant makesthese materials promising as permanent magnet materials, but moreinvestigations are necessary.

  • 54.
    Chamoun, Ninus
    et al.
    KTH, Skolan för kemivetenskap (CHE).
    Kjellvertz, Viktor
    KTH, Skolan för kemivetenskap (CHE).
    Mahajan, William
    KTH, Skolan för kemivetenskap (CHE).
    Song, Yuanchao
    KTH, Skolan för kemivetenskap (CHE).
    Fate of Heavy Metals in Waste to Energy (WtE) Processes2016Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    This study was made to increase the understanding of how heavy metals in the aqueous phase are removed at low initial concentrations in different pH and Eh values. The reaction that has been studied is mainly hydroxide precipitation and adsorption in a condensate treatment. In the study, data from one of Vattenfalls waste incinerators was analysed and the results from the data were then compared to previous studies. To increase the understanding, modelling of the heavy metals behaviour in the given concentrations was then made with Medusa and PHREEQC. The heavy metals that were analysed were Sb, As, Pb, Zn, Cr, and Cd. The low initial concentration that vary between 36.1-23600 μg/l complicates the removal process because it corresponds in a low driving force and the results are hard to compare to other studies since the initial concentrations vary between 10-100 mg/l.

    From the modelling and the measurement data it can be seen that Pb, Zn, Cr, and Cd was removed by hydroxide precipitation at pH 10. According to the speciation calculations, the dominant species at this pH are Pb(OH)

    2 , Cd(OH)2, Zn(OH)2 and Cr(OH)3. For arsenic a clear conclusion could not be drawn from the modelling and the measurement data because of low precision. Due to the limited thermodynamic parameters of antimony in comparison with other heavy metals in the database of Medusa and PHREEQC, the modelling of antimony behaviour in condensate treatment has relatively larger uncertainty is low. The modelling results show that the main species in acidic solutions for antimony is Sb(OH)3 and in basic solutions Sb(OH)-6. Further investigation for antimony in needed for a clear conclusions to be drawn

  • 55.
    Cho, Sung-Woo
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Protein-based Packaging Films, Sheets and Composites: Process Development and Functional Properties2009Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The depletion of the petroleum resources and a number of environmental concerns led to considerable research efforts in the field of biodegradable materials over the last few decades. Of the diverse range of biopolymers, wheat gluten (WG) stands out as an alternative to synthetic plastics in packaging applications due to its attractive combination of flexibility and strength, high gas barrier properties under low humidity conditions and renewability. The availability of raw materials has also been largely increased with an increase in the production of WG as a low-cost surplus material due to increasing demand for ethanol as fuel. In this study, WG was processed into films, sheets and composites using some of the most widely used techniques including solution casting, compression molding, extrusion and injection molding, accompanying process optimizations and characterization of their functional properties. This thesis consists mainly of six parts based on the purpose of the study. The first part addresses the aging and optical properties of the cast film in order to understand the mechanisms and reasons for the time-dependant physical and chemical changes. The films plasticized with glycerol were cast from acidic (pH 4) and basic (pH11) solutions. The film prepared from the pH 11 solution was mechanically more stable upon aging than the pH 4 film, which was initially very ductile but became brittle with time. It was revealed that the protein structure of the pH 4 film was initially less polymerized/aggregated and the polymerization increased during storage but it did not reach the degree of aggregation of the pH 11 film. During aging, the pH 4 film lost more mass than the pH 11 film mainly due to migration of glycerol but also due to some loss of volatile mass. In addition the greater plasticizer loss of the pH 4 film was presumably due to its initial lower degree of protein aggregation/polymerization. Glycerol content did not significantly change the opacity and pH 4 films showed good contact clarity because of less Maillard reaction. In the second part, the heat-sealability of WG films was investigated, using an impulse-heat sealer, as the sealability is one of the most important properties in the use of flexible packaging materials. It was observed that the WG films were readily sealable while preserving their mechanical integrity. The sealing temperature had a negligible effect on the lap-shear strength, but the peel strength increased with sealing temperature. The lap-shear strength increased with increasing mold temperature and the failure mode changed. The third part describes the possibility of using industrial hemp fibers to reinforce wheat gluten sheets based on evaluation of the fiber contents, fiber distribution and bonding between the fibers and matrix. It was found that the hemp fibers enhanced the mechanical properties, in which the fiber contents played a significant role in the strength. The fiber bonding was improved by addition of diamine as a cross-linker, while the fiber distribution needed to be improved. The fourth part presents a novel approach to improve the barrier and mechanical properties of extruded WG sheets with a single screw extruder at alkaline conditions using 3-5wt.% NaOH with or without 1 wt.% salicylic acid. The oxygen barrier, at dry conditions, was improved significantly with the addition of NaOH, while the addition of salicylic acid yielded poorer barrier properties. It was also observed that the WG sheets with 3 wt.% NaOH had the most suitable combination of low oxygen permeability and relatively small time-dependant changes in mechanical properties, probably due to low plasticizer migration and an optimal protein aggregation/polymerization. In the fifth part WG/PLA laminates were characterized for the purpose of improving the water barrier properties. The lamination was performed at 110°C and scanning electron microscopy showed that the laminated films were uniform in thickness. The laminates significantly suppressed the mass loss and showed promising water vapor barrier properties in humid conditions indicating possible applications in packaging. The final part addresses the development of injection molding processes for WG. Injection-molded nanocomposites of WG/MMT were also characterized. WG sheets were successively processed using injection molding and the process temperatures were found to preferably be in a range of 170-200°C, which was varied depending on the sample compositions. The clay was found to enhance the processability, being well dispersed in the matrix. The natural clay increased the tensile stiffness, whereas the modified clay increased the surface hydrophobicity. Both clays decreased the Tg and increased the thermal stability of the nanocomposites. The overall conclusion was that injection molding is a promising method for producing WG items of simple shapes. Further studies will reveal if gluten can also be used for making more complex shapes.

  • 56.
    Chondrogiannis, Georgios
    KTH, Skolan för kemivetenskap (CHE).
    Pretreatmenteffect on induction time and polymorphic outcome of tolbutamide crystallizationin 1-propanol2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    In this project, the effect of solution thermal and structural history on nucleation was investigated. Many researchers have shown that temperature and duration of pretreatment has an influence on induction time, polymorphic outcome and metastable zone width. Here, solution of tolbutamide in 1-propanol was first prepared with same conditions, to “standardize” and control the initial solution history. Next, pretreatment of varied duration and temperature was applied to introduce different solution history. Then, nucleation began in 9℃, and induction time and polymorphic outcome were measured. Two batches of 30 isolated nucleation experiments each, were done per set of conditions. The results showed an impact on induction time and polymorphic outcome. However, this change cannot be clearly correlated with the conditions of pretreatment. Furthermore, the deviation between series of experiments that were performed under the same set of conditions, showed that the parameters affecting induction time and polymorphism were not controlled sufficiently to reach a safe conclusion.

    Moreover, the effect of solution filtration right before nucleation was investigated. This filtration step decreased experimental induction time from 160 minutes to less than 5. It is possible that this filtration step removed the solution’s structural memory, which accelerated nucleation. However, the effect of evaporation on concentration for example, or other parameters was not investigated.

    Furthermore, the effect of using filtration with 0.1 and 0.2 μm filters was examined. It was found that using 0.1 filter results in decreased median induction time by a factor of 4. Finally, filtration before standardization resulted in a 1.5% increase in concentration compared to solution that was not filtered. Filtration with 0.1 μm filter before standardization decreased median induction time by a factor of 4, as compared to using a 0.2 μm filter.

  • 57. Cracknell, R. F.
    et al.
    Head, R. A.
    McAllister, L. J.
    Andrae, Johan
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    Octane sensitivity in gasoline fuels containing nitro-alkanes: A possible means of controlling combustion phasing for HCCI2009Inngår i: SAE technical paper series, ISSN 0148-7191Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Addition of nitroalkanes to gasoline is shown to reduce the octane quality. The reduction in the Motor Octane Number (MON) is greater than the reduction in the Research Octane Number (RON). In other words addition of nitroalkanes causes an increase in octane sensitivity. The temperature of the compressed air/fuel mixture in the MON test is higher then in the RON test. Through chemical kinetic modelling, we are able to show how the temperature dependence of the reactions responsible for break-up of the nitroalkane molecule can lead to an increase in octane sensitivity. Results are presented from an Homogenous Charge Compression Ignition (HCCI) engine with a homogeneous charge in which the air intake temperature was varied. When the engine was operated on gasoline-like fuels containing nitroalkanes, it was observed that the combustion phasing was much more sensitive to the air intake temperature. This suggests a possible means of controlling combustion phasing for HCCI.

  • 58.
    Cunha, Gisera
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Biokompositer. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center. INRA, Biopolymeres Interact & Assemblages, France.
    Mougel, Jean-Bruno
    Cathala, Bernard
    Berglund, Lars A.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Biokompositer. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Capron, Isabelle
    Preparation of Double Pickering Emulsions Stabilized by Chemically Tailored Nanocelluloses2014Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 30, nr 31, s. 9327-9335Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Nanocelluloses are bio-based nanoparticles of interest as stabilizers for oil-in-water (o/w) Pickering emulsions. In this work, the surface chemistry of nanocelluloses of different length, nanofibrillated cellulose (NFC, long) and cellulose nanocrystals (CNC, short), was successfully tailored by chemical modification with lauroyl chloride (C12). The resulting nanofibers were less hydrophilic than the original and able to stabilize water-in-oil (w/o) emulsions. The combination of the two types of nanocelluloses (C12-modified and native) led to new surfactant-free oil-in-water-in-oil (o/w/o) double emulsions stabilized by nanocellulose at both interfaces. Characterization was performed with respect to droplet size distribution, droplet stability over time, and stability after centrifugation. Nanocellulose-based Pickering emulsions can be designed with a substantial degree of control, as demonstrated by the stability of the chemically tailored NFC double emulsions. Furthermore, it was demonstrated that increased nanofiber length leads to increased stability.

  • 59.
    DAmico, A.
    et al.
    University of Roma Tor Vergata, Italy.
    Di Natale, C.
    University of Roma Tor Vergata, Italy; IDASC CNR, Italy.
    Falconi, C.
    University of Roma Tor Vergata, Italy; IDASC CNR, Italy.
    Pennazza, G.
    University of Campus Biomed Roma, Italy.
    Santonico, M.
    University of Campus Biomed Roma, Italy.
    Lundström, Ingemar
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biosensorer och bioelektronik. Linköpings universitet, Tekniska fakulteten.
    Equivalent electric circuits for chemical sensors in the Langmuir regime2017Inngår i: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 238, s. 214-220Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper presents an equivalent electric circuit model that describes adsorption-desorption processes occurring on bio and chemical sensor surfaces under the Langmuir hypothesis and considers the following practical case: the pressure or concentration of the particles in the test chamber is not perturbed by these processes and keeps its initial value, as in the cases of relatively high pressure or concentration values with zero molecular flow, or in the presence of a molecular flow at any pressure or concentration value. It is also pointed out that the equivalent circuit for Langmuir adsorption is similar to the circuit proposed for enzymatic reactions. Even if this work essentially covers theoretic aspects, a way is suggested for the possible experimental determination of both adsorption-desorption parameters and adsorption-desorption site density. (C) 2016 Elsevier B.V. All rights reserved.

  • 60.
    Darmastuti, Zhafira
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad sensorvetenskap. Linköpings universitet, Tekniska högskolan.
    Bhattacharyya, Partha
    Bengal Engineering and Science University, India.
    Basu, Sukumar
    Jadavpur University, India.
    Käll, Per-Olov
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Kemi. Linköpings universitet, Tekniska högskolan.
    Ojamäe, Lars
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Kemi. Linköpings universitet, Tekniska högskolan.
    Lloyd Spetz, Anita
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad sensorvetenskap. Linköpings universitet, Tekniska högskolan.
    SiC - FET Sensors for methanol leakage detection2012Inngår i: Proceeding of the 14th International Meeting on Chemical Sensors (IMCS 2012), 2012, s. 1579-1582Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Pt and Ir SiC based Field Effect Transistor sensors were tested to detect low concentration of methanol (<200 ppm) for both process control and leak detection applications. Pt sensors gave good and very fast response at 200°C, while Ir sensors gave larger but much slower response. The presence of oxygen improved the response of the sensor which was favorable for the leak detection application. The influence of hydrogen and propene to the sensor response was also studied. Beside the experimental work, the detection mechanism and different sensing behavior of Pt and Ir were studied by quantum chemical calculations.

  • 61.
    Davidsson, Åsa
    et al.
    Lund University, Sweden.
    Kjerstadius, Hamse
    Lund University, Sweden.
    Haghighatafshar, Salar
    Lund University, Sweden.
    Fick, Jerker
    Umeå University, Sweden.
    Eriksson, Eva
    Technical University of Denmark, Denmark.
    Olsson, Mikael Emil
    Technical University of Denmark, Denmark.
    Wachtmeister, Hilla
    Technical University of Denmark, Denmark.
    Cour Jansen, Jes la
    Lund University, Sweden.
    Effect of anaerobic digestion at 35, 55 and 60 °C ON pharmaceuticals and organic pollutants2013Inngår i: Presented at the 1st International IWA Conference on Holistic Sludge Management, Västerås, Sweden, May 6-8, 2013, 2013, s. 1-8Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The application of treated sewage sludge on farmland is a suggested method for recycling nutrients and reducing demand for commercial fertilizer. However sludge needs to be rendered safe from possible contaminants which can cause acute and long-term health and environmental problems. Residual pharmaceuticals and organic contaminants in sludge are mentioned as emerging threats since wastewater treatment plants are not designed to degrade these substances thus yielding an accumulation in sludge. The aim of this study was to evaluate the presence, and reduction, of pharmaceuticals and polycyclic aromatic hydrocarbons (PAHs) during anaerobic digestion at 35, 55 and 60ºC and during pasteurization at 70°C. The substrate used was mixed primary and secondary sludge from a 300 000 person-equivalents municipal wastewater treatment plant in southern Sweden. In general no reduction of pharmaceuticals could be observed at any temperature or minimum exposure time, except for the beta-blocker Irbesartan and the antibiotic Trimethoprim. The results from pharmaceuticals in mesophilic sludge agreed with results in recent Swedish studies. Also, no reduction of PAHs during digestion or pasteurization (70°C – 1 hour) was seen, but for single PAHs digestion could lead to reduction.

  • 62.
    Deshpande, Raghu
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper.
    The initial phase of the sodium bisulfite pulping of softwood dissolving pulp2015Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The sulfite pulping process is today practised in only a small number of pulp mills around the globe and the number of sulfite mills that use sodium as the base (cation) is less than five. However, due to the increasing interest in the wood based biorefinery concept, the benefits of sulfite pulping and especially the sodium based variety, has recently gained a lot of interest. It was therefore considered to be of high importance to further study the sodium based sulfite process to investigate if its benefits could be better utilized in the future in the production of dissolving pulps. Of specific interest was to investigate how the pulping conditions in the initial part of the cook (≥ 60 % pulp yield) should be performed in the best way.

    Thus, this thesis is focused on the initial phase of single stage sodium bisulfite cooking of either 100 % spruce or 100 % pine wood chips. The cooking experiments were carried out with either a lab prepared or a mill prepared cooking acid and the temperature and cooking time were varied. Activation energies for different wood components were investigated as well as side reactions concerning the formation of thiosulfate and sulfate.

  • 63.
    Done, Victoria
    KTH, Skolan för kemivetenskap (CHE).
    General description of measures for environmental compliance of substations owned by Svenska kraftnät in protected areas with focus on oil spill2014Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    Svenska kraftnät is the Swedish transmission system operator, responsible for the national electrical grid with power lines of 220 kV and 400 kV, and the electrical substations of the grid. In this master thesis an old substation located in a sensitive environmental area is inspected and its environmental risks defined and assessed. From this “worst case scenario” measures are recommended, that should be applicable on other existing substations, and for new constructed substations. This thesis is limited to a more detailed analysis on how oil spill can be handled. The insulating oil is used in different machines and equipment on the substation to avoid electrical charges.

    The inspected substation has a special feature; a pipe system that connects wells on the substation area, water pipes from the substation house, and transformer pits to an oil-water separation house. The oil pits are made of concrete and placed under machines with large amounts of oil to capture the oil in case of a breakdown or leakage. In the oil-water separation house oil is separated from water and the clean water is sent to a lake in the vicinity. The most severe environmental risks found are the filter in the oil-water separation house and the risk of oil leakage from the open water-cooling system of the synchronous generator. In addition, there is no way to catch oil spill from current and voltage transformers and it is not known if the pipe system that transports water and oil spills is completely sealed. Finally, there is no permanent installation to catch spills from tank filling areas and Svenska kraftnät does rarely follow up the environmental work of the entrepreneurs.

    Svenska kraftnät is recommended to use the products and services from the companies Qlean Scandinavia AB and TTL Miljöteknik AB to attend to the noted environmental risks. Qlean Scandinavia AB offers an environmental friendly cleaning procedure with ultraclean water and sealing of concrete, which can be used for the transformer pits and oil-water separation house. They also sell profile planks as a fire-extinguishing layer for transformer pits. These are considered better and safer than the conventional stones used. The price is almost the same, however the maintenance costs are lower for the profile planks, since they are easier to clean and do not require heavy transports to landfill. They also require less space than the stones, therefore a smaller transformer pit can be built, and cost savings can be made on concrete.

    TTL Miljöteknik AB has products based on environmental friendly oil solidifying polymers placed in different textiles and filters. They let water and other substances pass, but react with hydrocarbons, like oil, forming a tight rubberlike mass. These installations are new to Europe, but more than 12 000 installations have been made, mainly in the United States and Australia. For the inspected substation in this thesis it is recommended to manage oil spill at each machine and to clean the pipe system. An HFF-filter should be installed in cleaned and sealed transformer pits. The filter lets water from precipitation pass, but binds oil, thanks to the solidifying polymers. The clean water is further transported through the pipe system to the oil-water separation house and from there water is pumped to the lake. Wells must be sealed and the pipes from the substation house led to a septic tank. Agent X, a type of filter mat, should be placed on the substation area to catch oil spills from current and voltage transformers, since previous breakdowns show that oil can be spread over a large area.

    For plants without a pipe system the water will be released outside the transformer pits. For new constructions it is suggested that transformer pits are built with a polyvinyl mat in the bottom and a filter on the sides, which will capture the oil. A concrete fundament still needs to be built to support the machine; therefore the price will almost be the same as for the conventional transformer pit in concrete, although less concrete is needed. However, with this technique the transformer pit will not require any maintenance.

  • 64.
    Du, Jian
    et al.
    Dalian Univ Technol, State Key Lab Fine Chem, DUT KTH Joint Educ & Res Ctr Mol Devices, Dalian 116024, Peoples R China..
    Li, Fei
    Dalian Univ Technol, State Key Lab Fine Chem, DUT KTH Joint Educ & Res Ctr Mol Devices, Dalian 116024, Peoples R China..
    Wang, Yong
    Dalian Univ Technol, State Key Lab Fine Chem, DUT KTH Joint Educ & Res Ctr Mol Devices, Dalian 116024, Peoples R China..
    Zhu, Yong
    Dalian Univ Technol, State Key Lab Fine Chem, DUT KTH Joint Educ & Res Ctr Mol Devices, Dalian 116024, Peoples R China..
    Sun, Licheng
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Organisk kemi. Dalian Univ Technol, State Key Lab Fine Chem, DUT KTH Joint Educ & Res Ctr Mol Devices, Dalian 116024, Peoples R China..
    Cu3P/CuO Core-Shell Nanorod Arrays as High-Performance Electrocatalysts for Water Oxidation2018Inngår i: Chemelectrochem, ISSN 2196-0216, Vol. 5, nr 15, s. 2064-2068Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Earth-abundant transition-metal-based oxides are potential candidates to replace the state-of-the-art noble-metal-based oxygen evolution catalysts (OECs) such as IrO2 and RuO2. Despite the low cost and large abundance, copper-based OER catalysts have been less frequently studied, mainly owing to the low electrical conductivity of copper oxides that results in large overpotential and sluggish kinetics for oxygen evolution. We report here the insitu fabrication of semi-metallic Cu3P nanorod arrays on commercial copper foam via a template approach; the resulting self-supported core-shell Cu-Cu3P/CuO electrode has the merits of high electrical conductivity, large active area, and short diffusion paths for electrolyte and evolved oxygen, exhibiting a low overpotential of 315mV and high durability over 50h at a current density of 10mAcm(-2) for OER in 1.0 M KOH. The remarkable OER performance reported here is not only superior to that of analogous Cu-CuO foam electrode, but also outperforms those of copper-based OER electrocatalysts in the literature.

  • 65.
    EDRISI, KEYVAN
    KTH, Skolan för kemivetenskap (CHE).
    Fastställande av PGM-tillgänglighet för dieseloxidationskatalysator med hjälp av kemisorption2015Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The Diesel Oxidation Catalyst (DOC) is subjected to harsh conditions, causing its performance to

    diminish over time as the result of different aging mechanisms, which either decreases or lowers the

    accessibility to the catalyst’s active sites. Previous work using chemisorption to quantify aging progression

    has resulted in a reproducibility of 17%. In this study it has been attempted to lower this, while

    also performing performance evaluations to see if correlations exist between dispersion and Light-Off

    Temperature (LOT).

    Two catalysts have been investigated, LLC (Low Loading Catalyst) and HLC (High Loading Catalyst).

    These were hydrothermally aged at 600 C, 700 C and 800 C. In addition to these, two HLC engine cell

    samples were also investigated.

    To ensure sample homogeneity, different sample preparation methods were investigated. Catalyst samples

    were crushed, or had their washcoat layer removed, or were milled and then sieved. A total of 5 runs were

    done using fresh catalysts of LLC and HLC to calculate the standard deviation. Evaluation of performance

    was done on all samples using Synthetic Catalyst Activity Testing (SCAT).

    It was deemed that the only viable sample preparation method was to mill and sieve as other methods

    would be hard to reproduce. The results showed that the reproducibility for LLC was %STD = 4% and

    for HLC %STD = 2%. For LLC, a correlation between catalytic activity and dispersion was found. The

    activity dropped with respect to the dispersion in a close to linear fashion without a large effect on BET

    surface area. For HLC the dispersion decreased largely upon hydrothermal aging, however no correlation

    was found with the activity; only when aged at 800 C a significant change in LOT was noted. The BET

    surface area measurements were inconsistent. Lower dispersion sometimes resulted in higher surface area.

    Engine cell samples exhibited notable decrease in dispersion, but not in surface area, and did not correlate

    to the hydrothermally aged catalysts, which might be due to other effects inhibiting CO chemisorption

    during measurements.

  • 66.
    Edström, Evelina
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik, Innovation och produktrealisering.
    Hillström, Martin
    Mälardalens högskola, Akademin för innovation, design och teknik, Innovation och produktrealisering.
    Produktutveckling miljöteknik: Framtagning av produkt som varnar vid förskämning av mjölk2017Independent thesis Basic level (university diploma), 10 poäng / 15 hpOppgave
    Abstract [en]

    The aim of the thesis, industrial product design PPU304, is to develop a new product that will reduce food waste of dairy products in households. The main objective is that the product will be able to measure and signal when the milk has expired.The thesis is a start to find the solution to some of the food waste in households which is a major environmental issue in today's society. The goal is to develop a flexible expiration date that can reduce food wastage. With today's sensor technology bacterial levels can be calculated from the milk and that can increase the time a pack of milk can be used. The greater knowledge and awareness humanity have for environmental issues the better world we will live in. To understand the question, “what is it that makes the milk unfit for consumption?” A part of the work has gone into researching the technological aspect. In consumer ready milk there is different bacteria that will grow over time and eventually spoil the milk, how this process works varies depending on what or which bacteria manage to grow the most. Therefore, the most appropriate technique is to measure bacteria in the milk and identify at which level the milk passes its actual expiration date.The design of the product has been guided by two major factors, the predetermined dimensions of the circuit board and the adaptation to the size of the milk carton. The shape of the product is an oblong rear part with a spherical body at the front. The edges are rounded to give a pleasantand smooth feeling to the hand using the product.The thesis in industrial product design resulted in a final concept. The product analyses the amount of bacteria in the milk through sensors that measure bacterial metabolism. The data gets interpreted and displayed through the use of LEDs. To save energy the concept is equipped with a photo resistor that deactivates the LEDs when the fridge is closed and dark. The conclusion of the thesis, performed at Millcroft AB is at a conceptual level. To go from idea to product, is a process that takes a long time to complete and often involves many different moments. The timeframe during this study is considered too short to cover all parts of the product and therefore the boundaries set and the focus has been on constructing a design that fits the estimated technology as well as consumer needs. Some suggestions are that more research in the technical aspect of the product should be concluded. Further testing of dairy sustainability should be conducted on a larger scale and further development of the technology to send data.

  • 67.
    Eita, Mohamed
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Fiberteknologi.
    In situ study of the adsorption of humic acid on the surface of aluminium oxide by QCM-D reveals novel features2011Inngår i: SOFT MATTER, ISSN 1744-683X, Vol. 7, nr 2, s. 709-715Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Novel features of the adsorption of humic acid on the surface of aluminium oxide were revealed by means of an in situ study by quartz crystal microbalance with dissipation (QCM-D). The adsorption of humic acid on the surface of aluminium oxide shows a special case at pH 3 where the adsorption takes place in two steps. Each step has characteristic thickness, kinetics and viscoelasticity. While the first step shows low thickness, fast kinetics and almost no viscoelastic character, indicating a rigidly adsorbed humic acid monolayer, the second step is of much higher thickness, slower kinetics and with significant viscoelastic character, indicating a large diffuse layer with significant bulk contributions. In contrast, adsorption at pH 5 and 6.8 was found to be limited to a monolayer which is more rigid at pH 5 than at pH 6.8. Ellipsometry and X-ray photoelectron spectroscopy (XPS) were used to prove and quantify the adsorption in the dry state. The monolayer thickness measured by ellipsometry is close to the Sauerbrey thickness obtained by QCM-D. Adsorption takes place at a dilute concentration of 1 mg L-1, followed by saturation at a concentration of 10-20 mg L-1. XPS spectra of the carbon 1s peak indicated almost no desorption of the adsorbed humic acid layer after immersion in water for 48 hours, implying irreversible adsorption based on a strong binding between humic acid and aluminium oxide.

  • 68.
    Eivazihollagh, Alireza
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Metal-Chelate Complexes in Alkaline Solution: On Recovery Techniques and Cellulose-based Hybrid Material Synthesis2018Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    For decades, aminopolycarboxylate chelating agents have been extensively used in various industrial applications. The ability of chelating agents to form stable metal-chelate complexes is the main reason for using them to manage metal ions within water-based industrial processes. Considerable quantities of industrial effluent containing chelating agents and heavy metals are produced and often discharged into the environment. The toxicity of heavy metals and the non-biodegradability of the chelating agents, as well as their accumulation in the environment, has become cause for concern. The main purpose of this thesis was to evaluate and develop processes for recovery of chelated metal complexes from aqueous solution. In this regard, the membrane electrolysis technique was evaluated for recovery of copper and aminopolycarboxylic chelating ligands such as ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), diethylenetriaminepentaacetic acid (DTPA), and a surface-active derivative of DTPA, 2-dodecyldiethylenetriaminepentaacetic acid (C12-DTPA) from aqueous solution. By using this method, it was possible to simultaneously recover the chelating ligand for further reuse and collect the metals by electrodeposition, making the process more cost-effective and hindering the discharge of copper ions and chelating ligands as pollutants into the environment. In addition, the ion flotation technique with the chelating surfactant C12-DTPA could be employed to separate metal ions, especially from their dilute solutions, and concentrate them in a foam phase. This is because C12-DTPA has a purpose-built functionality; besides forming strong coordination complexes with metal ions, it is also surface-active and will readily adsorb at air-water interfaces. In this study, C12-DTPA was effectively used in combination with foaming agents for the removal of toxic metal ions such as Cd2+, Zn2+, and Sr2+ from aqueous solution using ion flotation. From an economical perspective, this method could be combined with the membrane electrolysis technique to recover metal and regenerate chelating surfactant so that it can be reused.

    The present work also shows the synthesis of metal and metal oxide(s) nanoparticles (NPs) in alkaline aqueous solution containing chelated metal ions, in order to fabricate metal NPs–cellulose hybrid materials. Cellulose is the most abundant renewable material, with good mechanical performance and chemical resistivity in a wide range of solvents, which makes it a promising material to support metal NPs. In this respect, we developed a rapid and inexpensive one-pot synthesis of spherical copper NPs in a cellulose matrix. The hybrid material displayed antibacterial properties for both the gram-negative and gram-positive bacteria. The synthesis was further developed by studying the influence of various chelating ligands and surfactants on the NPs’ morphology and chemical composition. According to the results, DDAO, a zwitterionic surfactant, was found to mediate the formation of pure octahedral Cu2O NPs. In addition, a hybrid material film composed of regenerated cellulose and synthesized Cu2O nano-octahedrons was fabricated by spin-coating.

  • 69.
    Eivazihollagh, Alireza
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för kemiteknik.
    Svanedal, Ida
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för kemiteknik.
    Edlund, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för kemiteknik.
    Norgren, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för kemiteknik.
    On chelating surfactants: Molecular perspectives and application prospects2019Inngår i: Journal of Molecular Liquids, ISSN 0167-7322, E-ISSN 1873-3166, Vol. 278, s. 688-705Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Chelating agents, molecules that very strongly coordinates certain metal ions, are used industrially as well as in consumer products to minimize disturbances and increase performance of reactions and applications. The widely used sequestering agents, nitrilotriacetic acid (NTA), ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (DTPA) belong to this branch of readily water-soluble compounds. When these chemical structures also have hydrophobic parts, they are prone to adsorb at air-water interfaces and to self-assemble. Such bifunctional molecules can be called chelating surfactants and will have more extended utilization prospects than common chelating agents or ordinary ionic surfactants. The present review attempts to highlight the fundamental behavior of chelating surfactants in solution and at interfaces, and their very specific interactions with metal ions. Methods to recover chelating surfactants from metal chelates are also described. Moreover, utilization of chelating surfactants in applications for metal removal in environmental engineering and mineral processing, as well as for metal control in the fields of biology, chemistry and physics, is exemplified and discussed.

  • 70.
    Eklund, Patrik
    et al.
    Department of Computer Science, Åbo Akademi, Åbo, Finland.
    Forsström, Jari
    University of Turku, Department of Clinical Chemistry, Central Laboratory, Turku University Central Hospital, SF-20520 Turku, Finland.
    Diagnosis of nephropathia epidemica by adaptation through Lukasiewicz inference1990Inngår i: Computational Intelligence, III: Proceedings of the International Symposium "Computational Intelligence 90", Milan, Italy, 24-28 September, 1990. / [ed] Nick Cerone, Francesco Gardin, co-editor, George Valle, Amsterdam, The Netherlands: Elsevier, 1990, s. 237-246Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

    This paper describes a method how to arrive at a medical expert system (as a knowledge based system) to support physicians in classifying patients in diagnosis of Nephropathia epidemica (NE). We thereby present a link between Lukasiewicz inference and learning in neural nets, as a formal connection between uncertainty in logical implication and synaptic weights. The system presented uses clinical findings and laboratory investigations to arrive at predictions whether or not patients suffer from NE. Although we are willing to call our system a medical expert system, it could equally well be called a decision support system, this being more in spirit to what such a system really offers a physician.

  • 71.
    Ekspong, Joakim
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Sharifi, Tiva
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Klechikov, Alexey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Gracia-Espino, Eduardo
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Stabilizing Active Edge Sites in Semicrystalline Molybdenum Sulfide by Anchorage on Nitrogen-Doped Carbon Nanotubes for Hydrogen Evolution Reaction2016Inngår i: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 26, nr 37, s. 6766-6776Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Finding an abundant and cost-effective electrocatalyst for the hydrogen evolu-tion reaction (HER) is crucial for a global production of hydrogen from water electrolysis. This work reports an exceptionally large surface area hybrid catalyst electrode comprising semicrystalline molybdenum sulfi de (MoS 2+ x) catalystattached on a substrate based on nitrogen-doped carbon nanotubes (N-CNTs), which are directly grown on carbon fiber paper (CP). It is shown here that nitrogen-doping of the carbon nanotubes improves the anchoring of MoS 2+ xcatalyst compared to undoped carbon nanotubes and concurrently stabilizes a semicrystalline structure of MoS 2+ x with a high exposure of active sites for HER. The well-connected constituents of the hybrid catalyst are shown to facilitate electron transport and as a result of the good attributes, the MoS 2+ x/N-CNT/CPelectrode exhibits an onset potential of −135 mV for HER in 0.5 M H2SO4, a Tafel slope of 36 mV dec −1, and high stability at a current density of −10 mA cm −2.

  • 72.
    Ekspong, Joakim
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Stainless Steel as A Bi-Functional Electrocatalyst – A Top-Down Approach2019Inngår i: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, nr 13, artikkel-id 2128Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    For a hydrogen economy to be viable, clean and economical hydrogen production methods are vital. Electrolysis of water is a promising hydrogen production technique with zero emissions, but suffer from relatively high production costs. In order to make electrolysis of water sustainable, abundant, and efficient materials has to replace expensive and scarce noble metals as electrocatalysts in the reaction cells. Herein, we study activated stainless steel as a bi-functional electrocatalyst for the full water splitting reaction by taking advantage of nickel and iron suppressed within the bulk. The final electrocatalyst consists of a stainless steel mesh with a modified surface of layered NiFe nanosheets. By using a top down approach, the nanosheets stay well anchored to the surface and maintain an excellent electrical connection to the bulk structure. At ambient temperature, the activated stainless steel electrodes produce 10 mA/cm(2) at a cell voltage of 1.78 V and display an onset for water splitting at 1.68 V in 1M KOH, which is close to benchmarking nanosized catalysts. Furthermore, we use a scalable activation method using no externally added electrocatalyst, which could be a practical and cheap alternative to traditionally catalyst-coated electrodes.

  • 73.
    Ekstrand, Eva-Maria
    et al.
    Linköpings universitet, Institutionen för tema, Tema Miljöförändring. Linköpings universitet, Filosofiska fakulteten.
    Karlsson, Marielle
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Truong, Xu-Bin
    Scandinavian Biogas.
    Björn, Annika
    Linköpings universitet, Institutionen för tema, Tema Miljöförändring. Linköpings universitet, Filosofiska fakulteten.
    Karlsson, Anna
    Scandinavian Biogas.
    Svensson, Bo H.
    Linköpings universitet, Institutionen för tema, Tema Miljöförändring. Linköpings universitet, Filosofiska fakulteten.
    Ejlertsson, Jörgen
    Scandinavian Biogas.
    The route towards stable and efficient anaerobic digestion of fibrous wastewater from pulp and paper mills in high-rate CSTRs with sludge recirculation2015Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    The pulp and paper industry carries high costs in wastewater treatment. By combining present techniques with anaerobic digestion (AD), expenses for electricity use and sludge disposal can be reduced. The large wastewater volumes require high-rate systems sensitive to suspended solids, and this has so far excluded treatment of the energy-rich wood fibres. In this study, AD of fibrous wastewater was examined in high-rate CSTRs with sludge recirculation. Two lab-scale reactors (4L) were run for 780 days. Once a day, reactor sludge was withdrawn and centrifuged. The main part of the supernatant was discarded, while the pellet was suspended with the substrate and returned to the reactor. This gave a sludge retention time of 10-16 days and a hydraulic retention time of 4-8 days. One reactor (denoted R1) was fed with fibre sludge, and the second reactor (denoted R2) was co-digesting fibre sludge and activated sludge. Both substrates were taken from a Kraft mill in Sweden. Initially, both reactors experienced frequent drops in pH, and continuous alkali supplements were necessary for process stability. Additions of magnesium and potassium were also needed to obtain stable process performance at an OLR of 3 g VS L-1·day-1. R1 and R2 behaved similarly, but R2 (co-digestion) was more robust with less or no fluctuations in VFA and pH. Addition of activated sludge also to R1 allowed an increase in OLR to 4 g VS L-1·day-1. In summary, stable and efficient operation of a high-rate CSTR with sludge recirculation digesting fibre sludge was achieved at an OLR of 4 g VS L-1·day-1, a HRT of 4 days and a methane production of 260±20 Nml. In addition, co-digestion with activated sludge stabilized the performance at increased OLR and thus gave more methane produced per reactor volume.

  • 74.
    Elhag, Sami
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska fakulteten.
    Chemically Modified Metal Oxide Nanostructures Electrodes for Sensing and Energy Conversion2017Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The goal of this thesis is the development of scalable, low cost synthesis of metal oxide nanostructures based electrodes and to correlate the chemical modifications with their energy conversion performance. Methods in energy conversion in this thesis have focused on two aspects; a potentiometric chemical sensor was used to determine the analytical concentration of some components of the analyte solution such as dopamine, glucose and glutamate molecules. The second aspect is to fabricate a photo-electrochemical (PEC) cell. The biocompatibility, excellent electro-catalytic activities and fast electron transfer kinetics accompanied with a high surface area to volume ratio; are properties of some metal oxide nanostructures that of a potential for their use in energy conversion. Furthermore, metal oxide nanostructures based electrode can effectively be improved by the physical or a chemical modification of electrode surface. Among these metal oxide nanostructures are cobalt oxide (Co3O4), zinc oxide (ZnO), and bismuth-zincvanadate (BiZn2VO6) have all been studied in this thesis. Metal oxide nanostructures based electrodes are fabricated on gold-coated glass substrate by low temperature (< 100 0C) wet chemicalapproach. X-ray diffraction, x-ray photoelectron spectroscopy and scanning electron microscopy were used to characterize the electrodes while ultraviolet-visible absorption and photoluminescence were used to investigate the optical properties of the nanostructures. The resultant modified electrodes were tested for their performance as chemical sensors and for their efficiency in PEC activities. Efficient chemically modified electrodes were demonstrated through doping with organic additives like anionic, nonionic or cationic surfactants. The organic additives are showing a crucial role in the growth process of metal oxide nanocrystals and hence can beused to control the morphology. These organic additives act also as impurities that would significantly change the conductivity of the electrodes. However, no organic compounds dependence was observed to modify the crystallographic structure. The findings in this thesis indicate the importance of the use of controlled nanostructures morphology for developing efficient functional materials.

  • 75.
    Eliasson, Anna
    Högskolan i Borås, Akademin för textil, teknik och ekonomi.
    En studie av egenskaperna hos biokol som adsorberande agent i o‐DGTanordningar2017Independent thesis Basic level (university diploma), 10 poäng / 15 hpOppgave
    Abstract [sv]

    En ny komplex aspekt i frågan om vattenkvalité är ackumuleringen av organiska föroreningar.Den begränsade utbredningen av vattenrening i Brasilien såväl som i andra utvecklingsländervisar på ett tydligt behov av utveckling av billiga och effektiva metoder för provtagning ivatten. Bristen på den här typen av metoder försvårar idag möjligheterna att kontrolleravattenkvalitén och på så vis även arbetet med att säkerställa de sanitära förhållandena ivattentillgångar. Det här examensarbetet innehåller en sammanfattande genomgång avprinciperna för den passiva provtagningsmetoden med namnet ”Diffusive Gradients in Thin‐Films (DGT)”, som direktöversatt får det svenska namnet ”Diffusiva gradienter i tunnfilmer”.När metoden används för provtagning för att upptäcka olika organiska ämnen i vattnetbenämns den som o‐DGT.Målet med detta arbete är att ta fram en metod med målet att specifikt upptäcka olika typerav nya framväxande organiska föroreningar som i de flesta fall förekommer bara i väldigt lågakoncentrationer i vår miljö. Grundliga undersökningar genomfördes för att få svar på huruvidabiokol kan fungera som den bindande agenten i DGT apparatur och verka för att kunnaupptäcka och identifiera dessa ämnen på ett effektivt sätt.Resultaten från de undersökningar som genomförts hittills visar på att biokol har godpotential att tillämpas som bindande agent i filter för bruk i o‐DGT apparatur. De organiskaföreningarna av intresse i denna studie kunde alla detekteras, kvantifieras och identifieras.För optimering av provtagningsmetoden bör vidare studier vid varierande förhållanden medhänsyn till pH, temperatur och jonkoncentration genomföras, såväl som studier av detbindande lagrets egenskaper i förhållande till koncentration av biokol och lagrets tjocklek.Detta för att kunna optimera tekniken, och förhoppningsvis bidra till ett konventionelltanvändande av biokol på adsorberande agent i o‐DGT anordningar i framtiden.

  • 76.
    Emera, Flory
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Strukturkemi.
    Method development for copper dispersion evaluation and copper-based catalysts characterization2013Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    N2O chemisorption technique for copper dispersion determination was developed and optimized for accurate and reproducible results. With this technique, the bulk oxidation of pre-reduced catalyst can be prevented by N2O decomposition at low temperature (30oC). Only surface copper atoms are oxidized. The amount of freshly oxidized surface coppers is determined from H2-back-titration of fixed oxygen.The impact of temperature and time of exposure during oxidation was studied. Measurements made at higher temperature (60oC) resulted in overestimation of copper dispersion due to oxygen diffusion into the bulk and sub-layers. Much longer exposure time may also have an impact on copper dispersion estimation.For accurate results and good precision, it is recommended to work under mild conditions (isothermal oxidation at 30oC for 45 min.The developed method was successfully applied to fresh and spent catalyst. As expected, the copper dispersion for fresh catalyst was significantly higher than copper dispersion for spent catalyst.

  • 77.
    Endrodi, Balazs
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Tillämpad elektrokemi.
    Smulders, Vera
    Univ Twente, Fac Sci & Technol, MESA Inst Nanotechnol, PhotoCatalyt Synth Grp, Meander 229,POB 217, NL-7500 AE Enschede, Netherlands..
    Simic, Nina
    Nouryon, SE-44580 Bohus, Sweden..
    Wildlock, Mats
    Nouryon, SE-44580 Bohus, Sweden..
    Mul, Guido
    Univ Twente, Fac Sci & Technol, MESA Inst Nanotechnol, PhotoCatalyt Synth Grp, Meander 229,POB 217, NL-7500 AE Enschede, Netherlands..
    Mei, Bastian
    Univ Twente, Fac Sci & Technol, MESA Inst Nanotechnol, PhotoCatalyt Synth Grp, Meander 229,POB 217, NL-7500 AE Enschede, Netherlands..
    Cornell, Ann M.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Tillämpad elektrokemi.
    In situ formed vanadium-oxide cathode coatings for selective hydrogen production2019Inngår i: Applied Catalysis B: Environmental, ISSN 0926-3373, E-ISSN 1873-3883, Vol. 244, s. 233-239Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Electrode selectivity towards hydrogen production is essential in various conversion technologies for renewable energy, as well as in different industrial processes, such as the electrochemical production of sodium chlorate. In this study we present sodium metavanadate as a solution additive, inducing selective cathodic formation of hydrogen in the presence of various other reducible species such as hypochlorite, chlorate, oxygen, nitrate, hydrogen-peroxide and ferricyanide. During electrolysis a vanadium-oxide coating forms from the reduction of sodium metavanadate, explaining the observed enhanced selectivity. The hydrogen evolution reaction proceeds without significantly altered kinetics on such in situ modified electrode surfaces. This suggests that the reaction takes place at the interface between the electrode surface and the protective film, which acts as a diffusion barrier preventing the unwanted species to reach the electrode surface.

  • 78.
    Endrodi, Balázs
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Tillämpad elektrokemi. Department of Physical Chemistry and Materials Science, University of Szeged, Szeged, Hungary.
    Sandin, Staffan
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Tillämpad elektrokemi.
    Wildlock, Mats
    Simic, Nina
    Cornell, Ann M.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Tillämpad elektrokemi.
    Suppressed oxygen evolution during chlorateformation from hypochlorite in the presenceof chromium(VI)2019Inngår i: Journal of chemical technology and biotechnology (1986), ISSN 0268-2575, E-ISSN 1097-4660, Vol. 94, nr 5, s. 1520-1527Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    BACKGROUND: Chromium(VI) is a crucial electrolyte component in industrial chlorate production. Due to its toxicity, iturgently needs to be abandoned and its functions fulfilled by new solutions. In the industrial production of sodium chlorate,homogeneous decomposition of the hypochlorite intermediate to chlorate is a key step. As a competing loss reaction,hypochlorite can decompose to oxygen. How chromium(VI) affects these reactions is not well understood.

    RESULTS: This work shows, for the first time, that chromium(VI) selectively accelerates the chlorate formation from hypochloriteboth in dilute and concentrated, industrially relevant solutions. The effect of the ionic strength and the specific contributionof different electrolyte components were systematically studied. By simultaneously measuring the concentration decayof hypochlorite (UV–vis spectroscopy) and the oxygen formation (mass spectrometry), both the rate and the selectivity of thereactions were evaluated.

    CONCLUSION: In the presence of chromium(VI) the hypochlorite decomposition is described by the sum of an uncatalyzedand a parallel catalyzed reaction, where oxygen only forms in the uncatalyzed reaction. When removing chromium(VI),the homogeneous oxygen formation increases, causing economic and safety concerns. The need for a catalyst selectivefor chlorate formation is emphasized.

  • 79.
    Endrődi, Balázs
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Tillämpad elektrokemi.
    Sandin, Staffan
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Tillämpad elektrokemi.
    Smulders, V.
    Simic, N.
    Wildlock, M.
    Mul, G.
    Mei, B. T.
    Cornell, Ann
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Tillämpad elektrokemi.
    Towards sustainable chlorate production: The effect of permanganate addition on current efficiency2018Inngår i: Journal of Cleaner Production, ISSN 0959-6526, E-ISSN 1879-1786, Vol. 182, s. 529-537Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Sodium dichromate is an essential solution additive for the electrocatalytic production of sodium chlorate, assuring selective hydrogen evolution. Unfortunately, the serious environmental and health concerns related to hexavalent chromium mean there is an urgent need to find an alternative solution to achieve the required selectivity. In this study sodium permanganate is evaluated as a possible alternative to chromate, with positive results. The permanganate additive is stable in hypochlorite-containing solutions, and during electrolysis a thin film is reductively deposited on the cathode. The deposit is identified as amorphous manganese oxide by Raman spectroscopic and X-ray diffraction studies. Using different electrochemical techniques (potentiodynamic measurements, galvanostatic polarization curves) we demonstrate that the reduction of hypochlorite is suppressed, while the hydrogen evolution reaction can still proceed. In addition, the formed manganese oxide film acts as a barrier for the reduction of dissolved oxygen. The extent of hydrogen evolution selectivity in hypochlorite solutions was quantified in an undivided electrochemical cell using mass spectrometry. The cathodic current efficiency is significantly enhanced after the addition of permanganate, while the effect on the anodic selectivity and the decomposition of hypochlorite in solution is negligible. Importantly, similar results were obtained using electrodes with manganese oxide films formed ex situ. In conclusion, manganese oxides show great promise in inducing selective hydrogen evolution, and may open new research avenues to the rational design of selective cathodes, both for the chlorate process and for related processes such as photocatalytic water splitting.

  • 80.
    Englund, Sven
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Oorganisk kemi.
    Controlling Co-capping in sintering of cermets2013Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    This master thesis includes a literature study and experimental work to understandthe conditions where a binder phase layer, Co-capping, could be produced orinhibited, for three different cermet grades in order to suggest changes in thesintering processes and two production units. The effect of C activity and sinteringatmosphere, e.g. flow rate, pressure were investigated. The results show that the Co-capping occurs on the cooling stage, when the binder phase, Co, solidifies. Co-capping could be inhibited by using a high C activity and high pressure (50 bar). Itwas further found that Co-capping could be evaporated using low pressure, i.e. vacuum, which has not been discussed in earlier studies on Co-capping. Evaporation was also found to have a relation with the solidification temperature of the grades,since grades with higher solidification temperature get Co-capping at a highertemperature, which consequently will be exposed to higher temperatures.

  • 81.
    Erdtman, Edvin
    et al.
    Högskolan i Borås, Institutionen Ingenjörshögskolan.
    Gebäck, Tobias
    Högskolan i Borås, Institutionen Ingenjörshögskolan.
    Ahlström, Peter
    Högskolan i Borås, Institutionen Ingenjörshögskolan.
    Atomistic Modelling of Protein Superabsorbents2012Konferansepaper (Annet vitenskapelig)
  • 82.
    Eriksson, Adam
    et al.
    KTH, Skolan för kemivetenskap (CHE).
    Kürten, Charlotte
    KTH, Skolan för bioteknologi (BIO), Proteomik och nanobioteknologi. KTH, Centra, Science for Life Laboratory, SciLifeLab.
    Syrén, Per-Olof
    KTH, Skolan för bioteknologi (BIO), Proteomik och nanobioteknologi. KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi. KTH, Centra, Science for Life Laboratory, SciLifeLab.
    Protonation-Initiated Cyclization by a ClassII Terpene Cyclase Assisted by Tunneling2017Inngår i: ChemBioChem (Print), ISSN 1439-4227, E-ISSN 1439-7633, Vol. 18, nr 23, s. 2301-2305Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Terpenes represent one of the most diversified classes of natural products with potent biological activities. The key to the myriad of polycyclic terpene skeletons with crucial functions in organisms from all kingdoms of life are terpene cyclase enzymes. These biocatalysts enable stereospecific cyclization of relatively simple, linear, prefolded polyisoprenes by highly complex, partially concerted, electrophilic cyclization cascades that remain incompletely understood. Herein, additional mechanistic light is shed on terpene biosynthesis by kinetic studies in mixed H2O/D2O buffers of a classII bacterial ent-copalyl diphosphate synthase. Mass spectrometry determination of the extent of deuterium incorporation in the bicyclic product, reminiscent of initial carbocation formation by protonation, resulted in a large kinetic isotope effect of up to seven. Kinetic analysis at different temperatures confirmed that the isotope effect was independent of temperature, which is consistent with hydrogen tunneling.

  • 83.
    Eriksson, Louise
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Analytisk kemi.
    Method development and optimization for determination of lipid oxidation in emulsions2016Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    Lipid emulsions in parenteral nutrition’s consist of two immiscible liquids described as oil in water phase. The oils in the emulsions can start to oxidize and make it become rancid. The oxidation can be measured for peroxide value, anisidine value and for free fatty acids (FFAs) as primary- and secondary oxidation products.

    This master thesis presents an analytical method used for analysis of oxidation products. The aim of this project was to come up with a method to separate the oil from the water-phase, to a sufficient yield and as pure as possible for analysis in a spectrophotometer called FoodLab fat. During the way experiments regarding stability of oils and finally a stability study on emulsions were done.

    Starting the separation experiments with ethanol to break the emulsion, this turned out to be the best way to go. Further investigation through extractions with 2- propanol/isooctane and ethanol/heptane were tested. The method needed to be simple, easy to use and not too time-consuming but still be repeatable and reliable.

    To optimize the separation, different centrifugation volumes, forces and times were tested. The results showed that in order to get the best separation the centrifugation volume and force cannot be too large or too small.

    The final method proved to be successful for the use as research method and to be able to see trends of oxidation for the products. Further research and validation of the instrument and the method needs to be done before it can be used as a quality control method. 

  • 84.
    Erlandsson, Per
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Ytors Fysik och Kemi. Linköpings universitet, Tekniska fakulteten.
    Electroosmotic pumps with electrochemically active electrodes2018Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Electrokinetic phenomena, motion caused by an applied electric field, can be used to separate molecules based on charge as in capillary electrophoresis, or pump liquids with electroosmosis. As microfluidic devices are becoming more advanced, involving multiple stages (sequential reactions) and requiring smaller amounts of reagent, the demand for precise fluid control and integrated electrodes increases. One of the main reasons for developing lab-on-a-chip devices is the realization of decentralized diagnostics, allowing patients to be monitored without going to a hospital or diagnosed in situations where healthcare infrastructure is not available.

    The first paper of this thesis investigates the differences in characteristics between an electroosmotic pump with metal electrodes and one using electrochemically active polymer electrodes. With metal electrodes reactions normally take place at the metal/electrolyte interface where the electrolyte or species therein are either reduced or oxidized to maintain an electric current. For water-based electrolytes the electrolysis of water produces pH altering species and gas, which can interfere with microfluidic systems. As electrochemically active electrodes can themselves be reduced or oxidized, the amount of undesired reactions at the polymer/electrolyte interface can be significantly decreased. The second and third papers investigate the use of porous potassium monoliths as electroosmotic pumps in microfluidic devices using electrochemically active electrodes. Porous potassium silicate monoliths were created inside fused silica capillaries in order to increase the pumps resistance to pressure driven flow. Potassium silicate structures without a fused silica capillary as a scaffold were produced in molds of polydimethylsiloxane. Asymmetric pumping properties of these stand-alone monolith was sometimes observed. Monoliths were produced in conical molds in an attempt to increase the asymmetric behavior.

  • 85.
    Ersson, Nils Olov
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Oorganisk kemi.
    Förrådet av äldre instrument hos avdelningen för Oorganisk kemi, Uppsala Universitet: Beskrivning utgående från en dokumentation utförd 20082018Annet (Annet (populærvitenskap, debatt, mm))
    Abstract [sv]

    Som del i masterexamen i museologi fick Hedda Gottberg och Rebecca Flodin 2008 i uppgift att dokumentera den samling av instrument som tillhörde avdelningen för Oorganisk kemi vid Uppsala Uni-versitet. Samlingen hade några år tidigare flyttats till en källarlokal i det nya Ångströmlaboratoriet i Uppsala. Denna dokumentation skedde under ledning av avdelningens prefekt Yvonne Brandt Anders-son och Nils Olov Ersson, pensionerad forskningsingenjör. Fotograferingen av alla föremålen, ofta från flera vinklar och alltid med angivande av föremålens angivna data, gav till resultat ett stort antal digitala filer. Ett urval av dessa fotografier med korta beskrivningar presenteras i denna skrift.

  • 86.
    Farzaneh, Amirfarrokh
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Zhou, Ming
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Antzutkin, Oleg
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Bacsik, Zoltan
    Department of Materials and Environmental Chemistry, Stockholm University.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Holmgren, Allan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Grahn, Mattias
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Adsorption of Butanol and Water Vapors in Silicalite‑1 Films with a Low Defect Density2016Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 32, s. 11789-11798Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Pure silica zeolites are potentially hydrophobic and have therefore been considered to be interesting candidates for separating alcohols, e.g., 1-butanol, from water. Zeolites are traditionally synthesized at high pH, leading to the formation of intracrystalline defects in the form of silanol defects in the framework. These silanol groups introduce polar adsorption sites into the framework, potentially reducing the adsorption selectivity toward alcohols in alcohol/water mixtures. In contrast, zeolites prepared at neutral pH using the fluoride route contain significantly fewer defects. Such crystals should show a much higher butanol/water selectivity than crystals prepared in traditional hydroxide (OH−) media. Moreover, silanol groups are present at the external surface of the zeolite crystals; therefore, minimizing the external surface of the studied adsorbent is important. In this work, we determine adsorption isotherms of 1-butanol and water in silicalite-1 films prepared in a fluoride (F−) medium using in situ attenuated total reflectance−Fourier transform infrared (ATR−FTIR) spectroscopy. This film was composed of well intergrown, plate-shaped b-oriented crystals, resulting in a low external area. Single-component adsorption isotherms of 1-butanol and water were determined in the temperature range of 35− 80 °C. The 1-butanol isotherms were typical for an adsorbate showing a high affinity for a microporous material and a large increase in the amount adsorbed at low partial pressures of 1-butanol. The Langmuir−Freundlich model was successfully fitted to the 1-butanol isotherms, and the heat of adsorption was determined. Water showed a very low affinity for the adsorbent, and the amounts adsorbed were very similar to previous reports for large silicalite-1 crystals prepared in a fluoride medium. The sample also adsorbed much less water than did a reference silicalite-1(OH−) film containing a high density of internal defects.The results show that silicalite-1 films prepared in a F− medium with a low density of defects and external area are very promising for the selective recovery of 1-butanol from aqueous solutions.

  • 87.
    Fashandi, Hossein
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad sensorvetenskap. Linköpings universitet, Tekniska fakulteten.
    Novel Layered and 2D Materials for Functionality Enhancement of Contacts and Gas Sensors2016Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Chemical gas sensors are widely-used electronic devices for detecting or measuring the density levels of desired gas species. In this study, materials with established or potential applications for gas sensors are treated. For the case of high-temperature applications (≈ 600 °C), semiconductor-based gas sensors suffer from rapid oxidation of the metallic ohmic contacts, the same cause-of-failure as for the general case of high-temperature semiconductor electronics. 4H-SiC is an ideal semiconductor for high-temperature applications. Ti3SiC2 is a known ohmic contact to 4H-SiC with the known two-step synthesis process of post-annealing of pre-deposited Ti/Al multilayers or sputter-deposition of Ti3SiC2 films at > 900 °C. Here, sputter-deposition of Ti on 4H-SiC at > 900 °C is presented as a novel single-step method for the synthesis of Ti3SiC2 ohmic contacts, based on a concurrent reaction between sputter-deposited Ti and 4HSiC. Ti3SiC2, similar to any other known ohmic contact, degrade rapidly in high-temperature oxidizing ambient. To try to overcome this obstacle, noble metal diffusion into Ti3SiC2 has been s studied with the goal to retain ohmic properties of Ti3SiC2 and harnessing oxidation resistivity of noble metals. A novel exchange intercalation between Ti3SiC2 and Au is discovered which results in the almost complete exchange of Si with Au giving rise to novel Ti3AuC2 and Ti3Au2C2. Ti3IrC2 is also synthesized through exchange intercalation of Ir into Ti3Au2C2. All the aforementioned phases showed ohmic properties to 4H-SiC. This technique is also studied based on Ti2AlC and Ti3AlC2 resulting in the synthesis of novel Ti2Au2C and Ti3Au2C2, respectively. Using Ti3AuC2 and an Au/IrOx capping layer, an ohmic contact was manufactured, which maintained ohmic properties and showed no structural defects after 1000 h of aging at 600 °C air.

    Ti3SiC2 is a member of a large family of materials known as Mn+1AXn phases. While exchange reactions of Si (or Al) planes in Ti3SiC2 (Ti2AlC and Ti3AlC2) is presented here, a world-wide research already exists on chemical removal of the same atomic planes from different Mn+1AXn phases and the synthesis of Mn+1Xn sheets known as MXenes. I performed a theoretical study regarding simulation of electronic and structural properties of more than120 different possible MXene phases. The results show that some MXene phases, when terminated by particular gas species, turn into Dirac materials. That is, they possess massless Dirac fermions with different properties compared to graphene such as higher number of Dirac points at the Fermi level, giant spin orbit splitting, and preserved 2D-type electronic properties by extending the dimensionality. The general substantial change of the electronic properties of MXenes under different gas adsorption configurations stands out and can thus be harnessed for sensing applications.

    Growth of monolayer iron oxide on porous Pt sensing layers is another novel approach used in this study for applying the unique properties of 2D materials for gas sensors. A low temperature shift in CO oxidation characteristics is presented. The approach is similar to that previously reported using bulk single crystal Pt substrate, the latter being an unrealistic model for sensors and catalysts. Monolayer-coated Pt sensing layers were fabricated as the metal component of a metal oxide semiconductor (MOS) capacitor device, whereby the electrical response of the MOS device could be used to map out the catalytic properties of the sensing layer. The monolayer-coated Pt surface showed to be stable with retained improved catalytic properties for > 200 h. The MOS device measurements are here utilized as a handy method for in-situ monitoring of the surface chemical properties of the monolayer-coated Pt and the approach is highly functional for use and characterization of monolayer coatings of widely used sensingor catalytic layers.

  • 88.
    Fjellgaard Mikalsen, Ragni
    RISE - Research Institutes of Sweden, Säkerhet och transport, Fire Research Norge. Western Norway University of Applied Sciences, Norway; Otto von Guericke University Magdeburg, Germany.
    Fighting flameless fires: Initiating and extinguishing self-sustainedsmoldering fires in wood pellets2018Doktoravhandling, monografi (Annet vitenskapelig)
    Abstract [en]

    Smoldering fires represent domestic, environmental and industrial hazards. This flameless form of combustion is more easily initiated than flaming, and is also more persistent and difficult to extinguish. The growing demand for non-fossil fuels has increased the use of solid biofuels such as biomass. This represents a safety challenge, as biomass self-ignition can cause smoldering fires, flaming fires or explosions.

    Smoldering and extinguishment in granular biomass was studied experimentally. The set-up consisted of a cylindrical fuel container of steel with thermally insulated side walls. The container was closed at the bottom, open at the top and heated from below by a hot surface. Two types of wood pellets were used as fuel, with 0.75-1.5 kg samples.

    Logistic regression was used to determine the transition region between non-smoldering and self-sustained smoldering experiments, and to determine the influence of parameters. Duration of external heating was most important for initiation of smoldering. Sample height was also significant, while the type of wood pellet was near-significant and fuel container height was not.

    The susceptibility of smoldering to changes in air supply was studied. With a small gap at the bottom of the fuel bed, the increased air flow in the same direction as the initial smoldering front (forward air flow) caused a significantly more intense combustion compared to the normal set-up with opposed air flow.

    Heat extraction from the combustion was studied using a water-cooled copper pipe. Challenges with direct fuel-water contact (fuel swelling, water channeling and runoff) were thus avoided. Smoldering was extinguished in 7 of 15 cases where heat extraction was in the same range as the heat production from combustion. This is the first experimental proof-of-concept of cooling as an extinguishment method for smoldering fires.

    Marginal differences in heating and cooling separated smoldering from extinguished cases; the fuel bed was at a heating-cooling balance point. Lower cooling levels did not lead to extinguishment, but cooling caused more predictable smoldering, possibly delaying the most intense combustion. Also observed at the balance point were pulsating temperatures; a form of long-lived (hours), macroscopic synchronization not previously observed in smoldering fires.

    For practical applications, cooling could be feasible for prevention of temperature escalation from self-heating in industrial storage units. This study provides a first step towards improved fuel storage safety for biomass. 

  • 89.
    Gara Ramos, Rodriguez
    KTH, Skolan för kemivetenskap (CHE).
    Nitrate and phosphate removal from aqueous solution by biochar and agroforestry residues2012Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
  • 90.
    Garemark, Jonas
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH).
    Studies of the Impregnation Stagein Kraft Pulping of Hardwood2018Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    In kraft pulping, one of the main issues is the extensive wood losses. With increasing prices ofwoody biomass an incentive towards minimizing the wood losses exists. Amongst the variousprocess steps, the impregnation of wood chips has shown to enhance the cooking by providinga homogeneous distribution of chemicals inside the chips. It is proven that a more proficientimpregnation phase can improve the overall yield in kraft pulping. However, there is a lack ofscientific research comparing different impregnation techniques for hardwood. Hence, thisthesis will attempt to clarify the impregnation of hardwood.The impregnation efficiency was studied by comparing three different impregnation methods:High Alkali Impregnation (HAI), Extended Impregnation (EI) using a low alkali level and aReference Impregnation (REF) to enable a comparison to the industrially establishedconditions. The cases were compared by analysing the yield, selectivity and homogeneity. Thecomparison was also made under cooking conditions with the objective to understand theimpact of impregnation on the subsequent cooking phase. The cooking procedure was assessedby analysing the degree of delignification, yield and reject content.In impregnation, most chemical consuming reactions occurred within the first 10-30 minutes,mainly contributed by deacetylation. HAI obtained the fastest homogeneous distribution of OH-(~60 min), but the fastest dissolution of wood. The effect was contributed by the high [OH-],providing fast diffusion of ions and rapid dissolution of xylan. In the contrary, EI attained thehighest impregnation yield after a given impregnation time but required a prolonged durationto obtain a chemical equilibrium between the free and bound liquor (~120 min). REF showeda higher yield than HAI and similar chemical equilibrium as EI. The hydrosulphide sorption inimpregnation was highest for EI due to the high initial sulphidity charge and similar for REFand HAI. For impregnations at 115°C, the HS- sorption was significantly increased for all cases,resulting from delignification. In the subsequent cooking phase, it was prevalent that impregnation of chips under EIconditions were easier delignified, leading to a reduced cooking time to reach the defibrationpoint. Birch was more prone to delignification than eucalyptus. In turn, eucalyptus also obtaineda higher defibration point. Highest total cooking yield at similar kappa numbers was achievedwith REF conditions, followed by HAI and lastly the EI conditions. The high yield of REF incontrast to HAI could be explained by an improved xylan yield due to an alleviated hydroxidelevel. The low yield of EI can be assigned to continues peeling due to the prolongedimpregnation and loss of xylan when removing black liquor after impregnation. In terms ofproduction rate, yield, energy and chemical consumption the REF is the most efficientimpregnation condition for birch kraft cooking in this batchwise laboratory kraft cookingprocedure.

  • 91. George, Gejo
    et al.
    Tomlal Jose, E.
    Åkesson, Dan
    Högskolan i Borås, Institutionen Ingenjörshögskolan.
    Skrifvars, Mikael
    Högskolan i Borås, Institutionen Ingenjörshögskolan.
    Nagarajan, E.R.
    Kuruvilla, Joseph
    Viscoelastic behaviour of novel commingled biocomposites based on polypropylene/jute yarns2012Inngår i: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 43, nr 6, s. 893-902Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Jute yarn reinforced polypropylene commingled composites were prepared by an environmentally benign technique called commingling method in which the matrix fibres and reinforcing fibres are intermingled together with good alignment. The dynamic mechanical properties or viscoelastic behaviour of these commingled composites were studied with reference to fibre content and various chemical treatments. The storage and loss modulus increased with fibre content where as tan δ decreased. KMnO4 and MAPP treated composites showed much higher storage and loss modulus values at all temperatures compared to untreated one. The glass transition temperature showed a marginal increasing tendency with fibre content and chemical treatments. The surface treatment mechanisms were supported by FT-IR spectra and the increase in interfacial adhesion after chemical treatments were supported by SEM images. Theoretical modelling was used to predict the values of storage modulus and tan δ and was found to be comparable with that of experimentally obtained results.

  • 92.
    Gerasimov, Jennifer
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Karlsson, Roger H
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Laboratoriet för organisk elektronik. Linköpings universitet, Tekniska fakulteten.
    Forchheimer, Robert
    Linköpings universitet, Institutionen för systemteknik, Informationskodning. Linköpings universitet, Tekniska fakulteten.
    Stavrinidou, Eleni
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Simon, Daniel T
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Laboratoriet för organisk elektronik. Linköpings universitet, Tekniska fakulteten.
    Berggren, Magnus
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Laboratoriet för organisk elektronik. Linköpings universitet, Tekniska fakulteten.
    Fabiano, Simone
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    An Evolvable Organic Electrochemical Transistor for Neuromorphic Applications2019Inngår i: ADVANCED SCIENCE, ISSN 2198-3844, Vol. 6, nr 7, artikkel-id 1801339Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An evolvable organic electrochemical transistor (OECT), operating in the hybrid accumulation-depletion mode is reported, which exhibits short-term and long-term memory functionalities. The transistor channel, formed by an electropolymerized conducting polymer, can be formed, modulated, and obliterated in situ and under operation. Enduring changes in channel conductance, analogous to long-term potentiation and depression, are attained by electropolymerization and electrochemical overoxidation of the channel material, respectively. Transient changes in channel conductance, analogous to short-term potentiation and depression, are accomplished by inducing nonequilibrium doping states within the transistor channel. By manipulating the input signal, the strength of the transistor response to a given stimulus can be modulated within a range that spans several orders of magnitude, producing behavior that is directly comparable to short- and long-term neuroplasticity. The evolvable transistor is further incorporated into a simple circuit that mimics classical conditioning. It is forecasted that OECTs that can be physically and electronically modulated under operation will bring about a new paradigm of machine learning based on evolvable organic electronics.

  • 93.
    Ghadami Yazdi, Milad
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Materialfysik, MF.
    H. Moud, Pouya
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik. KTH.
    Marks, Kess
    Piskorz, Witold
    Öström, Henrik
    Hansson, Tony
    Kotarba, Andrzej
    Engvall, Klas
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    Göthelid, Mats
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Materialfysik, MF.
    Naphthalene on Ni(111): experimental and theoretical insights into adsorption, dehydrogenation and carbon passivationManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    An attractive solution to mitigate tars and also to decompose lighter hydrocarbons in biomass gasification is secondary catalytic reforming, converting hydrocarbons to useful permanent gases. Albeit in use for long time in fossil feedstock catalytic steam reforming, the understanding of the catalytic processes is still limited. Naphthalene is typically present in the biomass gasification gas and to further understand the elementary steps of naphthalene transformation, we investigated the temperature dependent naphthalene adsorption, dehydrogenation and passivation on Ni(111). TPD (temperature programmed desorption) and STM (scanning tunneling microscopy) in ultra-high vacuum environment from 110 K up to 780 K, combined with DFT (density functional theory) were used in the study. Room temperature adsorption results in a flat naphthalene monolayer. DFT favors the di-bridge[7] geometry but the potential energy surface is rather smooth. DFT also reveals a pronounced dearomatization and charge transfer from the adsorbed molecule into the nickel surface. Dehydrogenation occurs in two steps, with two desorption peaks at approximately 450 K and 600 K. The first step is due to partial dehydrogenation generating active hydrocarbon species that at higher temperatures migrates over the surface forming graphene. The graphene formation is accompanied by desorption of hydrogen in the high temperature TPD peak. The formation of graphene effectively passivates the surface both for hydrogen adsorption and naphthalene dissociation. In conclusion, the obtained results on the model naphthalene and Ni(111) system, provides insight into elementary steps of naphthalene adsorption, dehydrogenation and carbon passivation, which may serve as a good starting point for rational design, development and optimization of the Ni catalyst surface, as well as process conditions, for the aromatic hydrocarbon reforming process.

  • 94.
    Ghanavi, Saman
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Organic-inorganic hybrid perovskites as light absorbing/hole conducting material in solar cells2013Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    Solar cells involving two different perovskites were manufactured and analyzed. The

    perovskites were (CH3NH3)PbI3 and (CH3NH3)SnI3. Both perovskites have a

    shared methyl ammonium group (MA) and are used as both light absorbing material

    and hole conducting material (HTM) in this project. The preparation procedures for

    the complete device were according to previous attempts to make stable

    organic-inorganic hybrid perovskites and involved different layers and procedures.

    Both perovskites were manufactured by mixing methyl ammonium iodide with either

    lead iodide or tin iodide in different concentrations. This was then deposited on a

    600nm thick mesoporous TiO2 layer. Deposition of the hole-transporting material

    (HTM) was done by spin-coating 2,2´,7,7´-tetrakis-(N,N-dip-methoxyphenylamine)

    9,9´-spirobifluorene, also called spiro-OMeTAD. Lastly thermal evaporation was used

    to deposit a silver electrode.

    Different measurements were done on the light absorbing materials. The lead

    perovskite solar cell device was subjected to illumination with Air Mass 1.5 sunlight

    (100mW/cm2) which produced an open circuit voltage Voc of 0.645 V, a short circuit

    photocurrent Jsc of about 7 mA/cm2, and a fill factor FF of 0.445. This resulted in a

    power conversion efficiency (PCE) of about 2% and an incident photon to current

    efficiency (IPCE) of up to 60%.

    The tin perovskite has not been used in solar cells before and the initial results

    presented here shows low performance using the same device construction as for the

    lead perovskite. However, the incident photon to electron conversion affirms that

    there is a current in the visible region, and IPCE of 12.5 % was observed at 375nm.

    UV-visible NIR measurement was used to analyze the light absorption of the

    perovskite structures and a broader light absorption was observed for the lead

    perovskite compared to the tin perovskite.

    X-ray diffraction (XRD) analyzing was done on both perovskite materials using

    different concentrations and both with and without nanoporous TiO2 film. Both

    perovskites demonstrate very similar peaks with some exceptions.

    Photo-induced absorption (PIA) measurement was used for the purpose of showing

    the magnitude of charge separation or hole transfer in the light absorbing material,

    both when using the perovskites as a light absorber and a hole conductor. This is

    measured by analyzing the hole injection from the excited light absorber into the

    HTM. Hole transfer was observed for the lead perovskite (when used as light

    absorber) and tin perovskite (when used as hole conductor).

  • 95.
    Gomez, Yasna Acevedo
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Tillämpad elektrokemi.
    Oyarce, Alejandro
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Tillämpad elektrokemi.
    Lagergren, Carina
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Tillämpad elektrokemi.
    Ammonia contamination of a proton exchange membrane fuel cell2018Inngår i: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 165, nr 3, s. F189-F197Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Reformate hydrogen from biogas is an attractive fuel alternative for energy conversion in PEM fuel cells. However, in the reformate traces of ammonia may be found, e.g. if the biogas is produced from agricultural resources. In this investigation the effect of ammonia in the fuel gas, on each part of the fuel cell, is studied by cyclic voltammetry, electrochemical impedance spectroscopy (EIS), symmetrical hydrogen cell (H2|H2)- and real fuel cell operation. A considerable degradation in performance is observed by introducing 200 ppm ammonia. The results show that ammonia not only affects the polymer electrolyte membrane but also the oxygen reduction reaction (ORR) and catalyst ionomer in both electrodes, whereas the hydrogen oxidation reaction (HOR) is the worst affected. In the short-term, the performance is reversible if running the cell on neat hydrogen after ammonia exposure, but this does not apply for long-term exposure. A mitigation method with air bleed is tested but gives no improvement of the performance.

  • 96.
    GONZALEZ NOVOA, NIKLAS
    KTH, Skolan för kemivetenskap (CHE).
    Katalytisk framställning av syntetisk naturgas (SNG)2015Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The aim of the  study  was to study  the  performance of nickel-based  catalysts  in the  production  of synthetic  natural  gas from synthesis gas (CO and H,). Nickel-based catalysts are preeminent catalysts in  this  reaction   due  to  their   high activity  and  selectivity  to  methane.  Nevertheless,   these   are threatened by severe  intrinsic deactivation  phenomena. In  more  detail, the goal of this work is to study   the   influence   of  different   catalyst   properties  on   the   three    most  severe   deactivation mechanisms  (nickel carbonyl formation,  carbon formation  and thermal  sintering). For that  purpose,  alumina-supported nickel catalysts containing  30 wt% Ni and promoted with Zr02, MgO, CaO and BaO were  prepared  and tested  in a high pressure  catalytic reactor.   The experimental work was divided in 3 parts according to specific study goals.

    The first  part of the  work consisted  in the  study  of the  catalyst  pellet size on deactivation due  to nickel carbonyl  formation. For that  purpose,  the  non-promoted  alumina-supported  nickel catalyst

    was tested  at 20 bar and 310 oc using three  different  pellet sizes. It was found  and  proved that  the

    use of large catalyst  pellet sizes significantly suppresses this  kind of deactivation. The results  were scientifically explained  by the influence of internal mass transfer phenomena. In order  to support this conclusion,  COMSOL multihpysics computations were  performed  to estimate internal  temperature and concentration profiles for the different  pellet sizes.

    The second  part of the  work was focused  on the effect of the selected  promoters on the  resistance towards  carbon  formation. For that  purpose, the different  catalysts  were tested  at 310 oc, 1 bar and

    a H,/C0=3; conditions  at which the carbon formation  is favorable. The spent  samples  were analyzed by means  of temperature-programmed hydrogenation  analyses  in order  to quantify the  amount  of carbon  formed. It was found  that  the  use of Zr02,  in particular,  significantly reduces  the  rate  of carbon formation.

    The third  part  of  the  work  consisted  in studying  the  effect  of these   promoters on  the  catalyst resistance  towards thermal  sintering.  For that  purpose,  the  different  catalysts  were  exposed  to an

    accelerated aging  procedure (690 oc and  H20/H2=2). The intrinsic catalytic activity of the  catalysts

    was  then  determined for  both  the  fresh  and  aged  samples   by testing  these  at  non-deactivating conditions  (300 oc, 1 bar and  H,jC0=9).  No clear  improvement neither  decline  in catalyst  stability

    was observed for any of the promoted  catalyst samples.

  • 97.
    González, María del Carmen
    et al.
    Universidad Autónoma Metropolitana, Unidad Azcapotzalco.
    Ramírez, Andrés
    KTH, Skolan för industriell teknik och management (ITM), Industriell ekonomi och organisation (Inst.).
    Portilla, Margarita
    Universidad Autónoma Metropolitana, Unidad Azcapotzalco.
    Ramírez, Javier
    Universidad Autónoma Metropolitana, Unidad Azcapotzalco.
    APPLYING THE CASE METHOD AND COMMUNITY – BASED LEARNING FINAL PROJECT IN A CHEMICAL ENGINEERING COURSE AT A PUBLIC UNIVERSITY IN MEXICO2012Inngår i: International Journal of Case Method Research & Application, ISSN 1554-7752, Vol. 24, nr 3, s. 187-191Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The case describes the use of the case method in a capstone course called ‘Terminal Project’ in the Chemical Engineering Department at the Autonomous Metropolitan University (UAM), Campus Azcapotzalco, in Mexico City.

    The purpose of applying the case method in the course was to make use of the students’ previously acquired knowledge in solving a real problem. The project also takes into account one of UAM’s general objectives, to provide community support for sustainable development [Universidad Autonoma Metropolitana, 2011]. Furthermore, the application exemplifies the case method as a useful integrating technique suitable for different types of teaching environments in Mexico, reaching beyond the prevailing practice of using cases to learn about managerial issues in private business schools.

    Through the methodology described. The students were able to retrieve the information that they felt was missing to find a proper solution to the vanilla harvest problem. Based on the answers from the people interviewed, the four students had the opportunity to go a step further in analyzing the case setting.

  • 98.
    Gryszel, Maciej
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Markov, Aleksandr
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Vagin, Mikhail
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Glowacki, Eric
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Organic heterojunction photocathodes for optimized photoelectrochemical hydrogen peroxide production2018Inngår i: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 6, nr 48, s. 24709-24716Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Solar-to-chemical conversion of sunlight into hydrogen peroxide as a chemical fuel is an emerging carbon-free sustainable energy strategy. The process is based on the reduction of dissolved oxygen to hydrogen peroxide. Only limited amounts of photoelectrode materials have been successfully explored for photoelectrochemical production of hydrogen peroxide. Herein we detail approaches to produce robust organic semiconductor photocathodes for peroxide evolution. They are based on evaporated donor-acceptor heterojunctions between phthalocyanine and tetracarboxylic perylenediimide, respectively. These small molecules form nanocrystalline films with good operational stability and high surface area. We discuss critical parameters which allow fabrication of efficient devices. These photocathodes can support continuous generation of high concentrations of peroxide with faradaic efficiency remaining at around 70%. We find that an advantage of the evaporated heterojunctions is that they can be readily vertically stacked to produce tandem cells which produce higher voltages. This feature is desirable for fabricating two-electrode photoelectrochemical cells. Overall, the photocathodes presented here have the highest performance reported to date in terms of photocurrent for peroxide production. These results offer a viable method for peroxide photosynthesis and provide a roadmap of strategies that can be used to produce photoelectrodes with even higher efficiency and productivity.

  • 99.
    Gunnarsson, Rickard
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska fakulteten.
    Controlling the growth of nanoparticles produced in a high power pulsed plasma2017Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Nanotechnology can profoundly benefit our health, environment and everyday life. In order to make this a reality, both technological and theoretical advancements of the nanomaterial synthesis methods are needed. A nanoparticle is one of the fundamental building blocks in nanotechnology and this thesis describes the control of the nucleation, growth and oxidation of titanium particles produced in a pulsed plasma. It will be shown that by controlling the process conditions both the composition (oxidationstate) and size of the particles can be varied. The experimental results are supported by theoretical modeling.

    If processing conditions are chosen which give a high temperature in the nanoparticle growth environment, oxygen was found to be necessary in order to nucleate the nanoparticles. The two reasons for this are 1: the lower vapor pressure of a titanium oxide cluster compared to a titanium cluster, meaning a lower probability of evaporation, and 2: the ability of a cluster to cool down by ejecting an oxygen atom when an oxygen molecule condenses on its surface. When the oxygen gas flow was slightly increased, the nanoparticle yield and oxidation state increased. A further increase caused a decrease in particle yield which is attributed to a slight oxidation ofthe cathode. By varying the oxygen flow, it was possible to control the oxidation state of the nanoparticles without fully oxidizing the cathode. Pure titanium nanoparticles could not be produced in a high vacuum system because oxygen containing gases such as residual water vapour have a profound influence on nanoparticle yield and composition. In an ultrahigh vacuum system titanium nanoparticles without significantoxygen contamination were produced by reducing the temperature of the growth environment and increasing the pressure of an argon-helium gas mixture within whichthe nanoparticles grew. The dimer formation rate necessary for this is only achievable at higher pressures. After a dimer has formed, it needs to grow by colliding with a titanium atom followed by cooling by collisions with multiple buffer gas atoms. The condensation event heats up the cluster to a temperature much higher than the gas temperature, where it is during a short time susceptible to evaporation. When the clusters’ internal energy has decreased by collisions with the gas to less than the energy required to evaporate a titanium atom, it is temporarily stable until the next condensation event occurs. The temperature difference by which the cluster has to cool down before it is temporarily stable is exactly as many kelvins as the gas temperature.The addition of helium was found to decrease the temperature of the gas, making it possible for nanoparticles of pure titanium to grow. The process window where this is possible was determined and the results presented opens up new possibilities to synthesize particles with a controlled contamination level and deposition rate.The size of the nanoparticles has been controlled by three means. The first is to change the electrical potential around the growth zone, which allows for size (diameter) control in the order of 25 to 75 nm without influencing the oxygen content of the particles. The second means is by increasing the pressure which decreases the ambipolar diffusion rate of the ions resulting in a higher growth material density. By doing this, the particle size can be increased from 50 to 250 nm, however the oxygen content also increases with increasing pressure when this is done in a high vacuum system. The last means of size control was by adding a helium flow to the process where higher flows resulted in smaller nanoparticle sizes.

    When changing the pressure in high vacuum, the morphology of the nanoparticles could be controlled. At low pressures, highly faceted near spherical particles were produced. Increasing the pressure caused the formation of cubic particles which appear to ‘fracture’ at higher pressures. At the highest pressure investigated, the particles became poly-crystalline with a cauliflower shape and this morphology was attributed to a lowad atom mobility.

    The ability to control the size, morphology and composition of the nanoparticles determines the success of applying the process to manufacture devices. In related work presented in this thesis it is shown that 150-200 nm molybdenum particles with cauliflower morphology were found to scatter light in which made them useful in photovoltaic applications, and the size of titanium dioxide nanoparticles were found to influence the selectivity of graphene based gas sensors.

  • 100.
    Gunnarsson, Rickard
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska fakulteten.
    Titanium oxide nanoparticle production using high power pulsed plasmas2016Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    This thesis covers fundamental aspects of process control when growing titanium oxide nanoparticles in a reactive sputtering process. It covers the influence of oxygen containing gas on the oxidation state of the cathode from which the growth material is ejected, as well as its influence on the particles oxidation state and their nucleation. It was found that a low degree of reactive gases was necessary for nanoparticles of titanium to nucleate. When the oxygen gas was slightly increased, the nanoparticle yield and particle oxygen content increased. A further increase caused a decrease in particle yield which was attributed to a slight oxidation of the cathode. By varying the oxygen flow to the process, it was possible to control the oxygen content of the nanoparticles without fully oxidizing the cathode. Because oxygen containing gases such as residual water vapour has a profound influence on nanoparticle yield and composition, the deposition source was re-engineered to allow for cleaner and thus more stable synthesis conditions.

    The size of the nanoparticles has been controlled by two means. The first is to change electrical potentials around the growth zone, which allows for nanoparticle size control in the order of 25-75 nm. This size control does not influence the oxygen content of the nanoparticles. The second means of size control investigated was by increasing the pressure. By doing this, the particle size can be increased from 50 – 250 nm, however the oxygen content also increases with pressure. Different particle morphologies were found by changing the pressure. At low pressures, mostly spherical particles with weak facets were produced. As the pressure increased, the particles got a cubic shape. At higher pressures the cubic particles started to get a fractured surface. At the highest pressure investigated, the fractured surface became poly-crystalline, giving a cauliflower shaped morphology.

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