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  • 4301. Wallström, Alexandra
    et al.
    Järnström, Lars
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Paper Surface Centre. Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Peltonen, J.
    The Influence of Thickeners on the Surface Structure and the Rheological Properties of PCC Suspensions2007In: Nordic Pulp and Paper Research Journal 22(1), 102-110 (2007)Article in journal (Refereed)
  • 4302. Wallström, Alexandra
    et al.
    Järnström, Lars
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Paper Surface Centre. Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Peltonen, J.
    The Influence of Water-Soluble Polymers on Surface Structure2006Conference paper (Other (popular science, discussion, etc.))
  • 4303. Wallström, Alexandra
    et al.
    Olsson, Martin
    Järnström, Lars
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering. Karlstad University, Faculty of Technology and Science, Paper Surface Centre. Karlstad University, Faculty of Technology and Science, Materials Science.
    Koschella, A.
    Fenn, D.
    Heinze, T.
    Influence of the functionalization pattern of ethyl cellulose on the interactions with polystyrene latex particles in aqueous mixtures2008In: Journal of Colloid and Interface Science, ISSN 0021-9797, Vol. 327, no 1, p. 51-57Article in journal (Refereed)
  • 4304. Wallström, Alexandra
    et al.
    Olsson, Martin
    Järnström, Lars
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Paper Surface Centre. Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Koschella, A.
    Fenn, D.
    Heinze, T.
    Influence of the functionalization pattern of ethyl cellulose on the interactions with polystyrene latex particles in aqueous mixtures2007Conference paper (Other (popular science, discussion, etc.))
  • 4305.
    Wallström, Stina
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Biofilms on silicone rubber for outdoor high voltage insulation2005Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Silicone rubber high voltage insulators are sometimes colonised by microorganisms which form a biofilm on the surface of the infected unit. In this work insulators exposed to the outdoor environment in Sweden, Sri Lanka and Tanzania respectively have been studied. The biofilms colonising the insulators were shown to be of roughly the same composition regardless of their origin. Algae in association with bacteria dominated the biofilms and provided nutrition to mold growth. The isolated microorganisms were further used to study the effect of a biofilm on different silicone rubber materials. New tools for diagnosing biological growth on polymeric materials were developed and used to analyse the silicone rubber samples.

    No evidence of biodegradation of the polydimethylsiloxane (PDMS) molecule has been found in this work. However, this does not mean that PDMS rubbers used in high voltage insulators can be called bioresistant. Silicone insulating materials always contain additives and these may promote or hinder growth. For this reason, an extensive test program was developed, in order to evaluate the effect of different additives on the degree of biological growth. The program spanned from fast and easy methods, useful for screening large amount of samples, to the construction of specially designed microenvironment chambers in which mixed biofilms, similar to those formed on the surface of silicone rubber insulators in the field, were successfully grown.

    The test program showed that the flame retardant zinc borate protected the materials, whereas alumina trihydrate (ATH) did not hinder biological growth. On the contrary, environmental scanning microscopy (ESEM) in combination with X-ray energy dispersive spectroscopy (EDS) showed that the surface roughening caused by the addition of ATH to the silicone rubber matrix made the materials more difficult to clean.

    Furthermore when the hydrophobic surface of a silicone rubber insulator is covered by a hydrophilic biofilm this leads to a reduction of the surface hydrophobicity of the material. This may alter the electrical properties of the insulator. It is therefore important to develop methods to identify biofouled units. In this work, laser-induced fluorescence (LIF) spectroscopy was explored as a tool for the detection of biofilms on silicone rubbers. The experiments revealed that weak traces of algae or fungal growth, even those not visible to the naked eye, could be detected by this technique. In addition, it was shown that photography and subsequent digital image analysis could be utilised to estimate the area covered by biofilm growth. The results obtained indicate that LIF spectroscopy in combination with image analysis could be used for field diagnostics of biological growth on insulators in service.

  • 4306.
    Wallström, Stina
    et al.
    KTH, Superseded Departments, Polymer Technology.
    Dowling, K.
    Karlsson, Sigbritt
    KTH, Superseded Departments, Polymer Technology.
    Development and comparison of test methods for evaluating formation of biofilms on silicones2002In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 78, no 2, p. 257-262Article in journal (Refereed)
    Abstract [en]

    Silicone rubber formulations used for outdoor high voltage insulation are sometimes reported to be colonized by microorganisms. Different formulations show different sensitivity towards biological growth. In this study five rubbers were tested. Two standard practices were used, ASTM G21-90 and IEC 68-2-10. In addition a new method was developed to measure the rate of colonisation of a sample by biological growth. Results showed that the tested rubbers supported fungal growth when an external carbon source was available. Thus none of the silicones can be called bio-resistant. However the materials are not biodegradable either. This was clearly shown when mould spores were added to the samples in clean water, when none of the rubbers was contaminated. Some of the materials did, however, support growth when only nutrient salts, no carbon source, was added. The most bioresistant formulations contained the flame retardant zinc borate, indicating that this additive suppresses fungal growth. Further investigation with the new method supported that theory.

  • 4307.
    Wallström, Stina
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Karlsson, Sigbritt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Image analysis and laser induced fluorescence combined to determine biological growth on silicone rubber insulators2005In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 88, no 3, p. 394-400Article in journal (Refereed)
    Abstract [en]

    High-voltage outdoor insulators made from silicone rubber are sometimes reported to be colonised by microorganisms. When the hydrophobic polymeric surface is covered by a hydrophilic biofilm, the electrical properties of the insulator are altered. In this work, mixed biofilms, similar to those formed on the surfaces of polymeric insulators in the field, were successfully grown on five types of silicone rubber substrates in the laboratory, using specially designed microenvironment chambers. Photography and digital image analysis were utilized to estimate the areas covered by the growth. It was found that direct UV-light exposure hindered growth of the biofilms. Further, growth was also hindered on samples where zinc borate had been added as flame retardant. In contrast, addition of ATH did not influence the growth. In parallel, LIF spectroscopy was explored as a tool for detection of biofilms on silicon rubber samples. Experiments revealed that even weak traces of growth, not visible to the naked eye, could be detected. Finally, it is believed that LIF spectroscopy in combination with image analysis can be used for field diagnostics of biological growth on insulators in service.

  • 4308.
    Walter, K.
    et al.
    AkzoNobel Pulp and Performance Chemicals, Bohus, Sweden.
    Paulsson, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering. AkzoNobel Pulp and Performance Chemicals, Bohus, Sweden.
    Engstrand, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Acid hydrogen peroxide treatment of Norway spruce TMP: The effect of chelated ferric ions2014In: International Mechanical Pulping Conference, IMPC 2014, Paper Engineer's Association (PI) , 2014Conference paper (Refereed)
    Abstract [en]

    The effect of treating thermomechanical pulp with Fenton chemistry was evaluated in a model study. Ferrous ions and chelated ferric ions were compared as catalysts while initial pH was varied. The results showed that a catalyst of ferrous sulphate had a greater impact on the pulp (increased total fibre charge and carbonyl groups, more dissolved organic material in filtrate) than ferric ions chelated with EDTA. If using ferric-EDG as catalyst, the hydrogen peroxide consumption was higher and more hydroxyl radicals were detected compared to if using ferrous sulphate. Ferric-EDG, however, gave similar or less effect on the pulp.

  • 4309.
    Walter, Karin
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    The use of Fenton chemistry for reducing the refining energy during TMP production: the effect of free ferrous and free or chelated ferric ions2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The potential of using acid hydrogen peroxide under Fenton conditions to lowerthe electrical energy consumed during the production of Black spruce (Piceamariana) thermomechanical pulp (TMP) was investigated in pilot scale. Thechemical system, which consisted of ferrous sulphate, hydrogen peroxide andoptionally an enhancer (such as a chelating agent), was evaluated as an inter-stagetreatment. The produced TMPs were thoroughly characterised in order to explainthe effect of the chemical system on fibre development and to be able to propose amechanism for the impact on refining energy reduction. The possibility to improvethe optical properties by washing, chelating and sodium dithionite or hydrogenperoxide bleaching the treated pulps was evaluated. The system of lignocellulosicmaterial, a Norway spruce (Picea abies) TMP, and Fenton chemistry was alsoevaluated in a model study to understand more about how conditions such as e.g.initial pH, dissolved organic material and reaction time affect the reactions.Ferrous and ferric ions (free and chelated) and different anions were evaluated.Moreover, it was examined whether hydroxyl radicals could be detected andmonitored.The results obtained in pilot scale showed that it is possible to significantly reducethe specific energy consumption by approximately 20% and 35% at a freenessvalue of 100 ml CSF or a tensile index of 45 Nm/g by using 1% and 2% hydrogenperoxide respectively. The energy reduction was obtained without any substantialchange to the fractional composition of the pulp, although tear strength wasslightly reduced, as were brightness and pulp yield. No major differences betweenthe reference pulp and the chemically treated pulps were found with respect tofibre length, width or cross-sectional dimensions. However, the acid hydrogenperoxide-treated pulps tended to have more collapsed fibres, higher flexibility, alarger specific surface area and a lower coarseness value. The yield lossiiiaccompanying the treatment was mainly a consequence of degradedhemicelluloses. It was also found that the total charge of the chemically treatedpulps was higher compared to the reference pulps; something that may haveinfluenced the softening behaviour of the fibre wall.A washing or chelating procedure could significantly reduce the metal ion contentof the chemically treated TMPs. The amount of iron could be further reduced to alevel similar to that of untreated pulps by performing a reducing agent-assistedchelating stage with dithionite. The discoloration could not, however, becompletely eliminated. The brightness decrease of the treated pulps was thereforenot only caused by the greater iron content in the pulp, but was also dependent onthe type of iron compound and/or other coloured compounds connected with theacid hydrogen peroxide treatment. Oxidative bleaching using hydrogen peroxidewas more effective than reductive bleaching using sodium dithionite in regainingthe brightness that was lost during the energy reductive treatment.From the model study and by using a chemiluminescence method, it could beconcluded that hydroxyl radicals were present in the system of Fenton chemicalsand lignocellulosic material (TMP). Initial pH, retention time, pulp consistency,type of catalyst (free or chelated) and dissolved organic material had an impact onthe reactions between TMP and acid hydrogen peroxide. Different anions(sulphate, nitrate and chloride) of ferric ion salt gave a similar catalytic effect.There appeared to be more reactions with the TMP when there was less dissolvedorganic material in the liquid phase from the start. A catalyst of ferrous sulphatehad a greater impact on the pulp (increased total fibre charge and carbonyl groups,more dissolved organic material in filtrate) than ferric ions chelated withethylenediaminetetraacetic acid at an initial pH of about 3-7. If using ferric-EDG(ethanol diglycinic acid) as catalyst, the measured effect on the pulp was similar orless compared to using ferrous sulphate. Ferric-EDG, however, gave higherhydrogen peroxide consumption and more detectable hydroxyl radicals than usingferrous sulphate (initial pH 5-8). It is likely that the iron catalyst must bind to theTMP, or be in close proximity to it, for the hydroxyl radicals to be able to react withthe material.A mechanism was proposed: the hydroxyl radicals generated in the Fentonreaction will probably attack and oxidise the available outer fibre surfaces,weakening these layers, and simultaneously dissolve some of the organic material.This can facilitate fibre development, give a better bonding pulp and reduce theelectrical energy required during refining.

  • 4310.
    Walter, Karin
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering. AkzoNobel Pulp & Performance Chem, SE-44580 Bohus, Sweden.
    Paulsson, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering. AkzoNobel Pulp & Performance Chem, SE-44580 Bohus, Sweden.
    Engstrand, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Acid Hydrogen Peroxide Treatment of Norway Spruce TMP: The Effect of an Extended pH Range when Catalyzed by Free Ferrous and Free or EDG/EDTA-Chelated Ferric Ions2014In: Journal of wood chemistry and technology, ISSN 0277-3813, E-ISSN 1532-2319, Vol. 34, no 2, p. 135-155Article in journal (Refereed)
    Abstract [en]

    The influence of different types of iron salts (i.e., ferrous or ferric cations with sulphate, nitrate or chloride anions) on the reaction between coarse thermomechanical pulp and acid hydrogen peroxide (Fenton chemistry) was studied when the initial pH was 3.2 and 5.3. Also, ferric ions chelated with EDTA or EDG at different molar ratios were compared with ferrous sulphate when the initial pH was extended from about 3 to 8. Different anions of ferric ion salt gave a similar catalytic effect. At an initial pH of 7–8, the ferric-EDTA catalyzed reaction resulted in similar or higher hydrogen peroxide consumption and more detectable hydroxyl radicals than the ferrous sulphate catalyzed reaction, but less reaction with the pulp was indicated. Between pH 5–8, using Fe-EDG as a catalyst gave higher hydrogen peroxide consumption and more detectable hydroxyl radicals than if using ferrous sulphate; however, the measured effect on the pulp was similar or less.

  • 4311.
    Walter, Karin
    et al.
    AkzoNobel Pulp & Performance Chemistry, Sweden.
    Paulsson, Magnus
    AkzoNobel Pulp & Performance Chemistry, Sweden.
    Hellstrom, Pia
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences. AkzoNobel Pulp & Performance Chemistry, Sweden.
    Acid Hydrogen Peroxide Treatment of Norway Spruce TMP: A Model Study Using Free Ferrous Ions and Ferric Ions Chelated with EDTA as Catalysts2013In: Journal of wood chemistry and technology, ISSN 0277-3813, E-ISSN 1532-2319, Vol. 33, no 4, p. 267-285Article in journal (Refereed)
    Abstract [en]

    The acid hydrogen peroxide system has been evaluated in more detail in the presence of a coarse Norway spruce thermomechanical pulp (TMP). The effects of parameters on the reactions involved were determined, such as pH, retention time, pulp consistency, type of iron catalyst, and the amount of dissolved organic material. Residual hydrogen peroxide, chemical oxygen demand, dissolved iron, and total fiber charge were quantified and the hydroxyl radical activity was monitored. The results showed that a catalyst of free ferrous ions (Fe2+) gave more reactions with the lignocellulosic material than ferric ions (Fe3+) chelated with EDTA. Furthermore, there were somewhat more reactions with the TMP when there was less dissolved organic material in the liquid phase from the start. Hydroxyl radicals were detected in all cases, but the level differed depending on the conditions used. It is likely that the iron must bind with the TMP or be in close proximity for the hydroxyl radicals to react with the pulp.

  • 4312.
    Walter, Karin
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics. AkzoNobel Pulp and Performance Chemicals , Bohus , Sweden.
    Paulsson, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics. AkzoNobel Pulp and Performance Chemicals , Bohus , Sweden.
    Hellström, Pia
    AkzoNobel Pulp and Performance Chemicals , Bohus , Sweden.
    Acid hydrogen peroxide treatment of Norway Spruce TMP: A model study using free ferrous ions and ferric ions chelated with EDTA as catalysts2013In: Journal of wood chemistry and technology, ISSN 0277-3813, E-ISSN 1532-2319, Vol. 33, no 4, p. 267-285Article in journal (Refereed)
    Abstract [en]

    The acid hydrogen peroxide system has been evaluated in more detail in the presence of a coarse Norway spruce thermomechanical pulp (TMP). The effects of parameters on the reactions involved were determined, such as pH, retention time, pulp consistency, type of iron catalyst, and the amount of dissolved organic material. Residual hydrogen peroxide, chemical oxygen demand, dissolved iron, and total fiber charge were quantified and the hydroxyl radical activity was monitored. The results showed that a catalyst of free ferrous ions (Fe2+) gave more reactions with the lignocellulosic material than ferric ions (Fe3+) chelated with EDTA. Furthermore, there were somewhat more reactions with the TMP when there was less dissolved organic material in the liquid phase from the start. Hydroxyl radicals were detected in all cases, but the level differed depending on the conditions used. It is likely that the iron must bind with the TMP or be in close proximity for the hydroxyl radicals to react with the pulp.

  • 4313.
    Walter, Marie V.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Novel Porous Films from Functional and Biocompatible Linear-Dendritic Hybrids2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In the last decades, the fabrication of ordered nano- and microporous structures has attracted increasing interest due to their specific properties and multiple possible applications in electronics, as templates or in the biological field. The development of such materials has been favored by the introduction of the simple breath-figure templating method in the 1990’s. In order to fully exploit the potential of these porous materials, the use of advanced functional molecules as precursors is essential. One suitable class of molecules is the well-defined linear-dendritic hybrids (LD hybrids) family. The structural variations, multiple end-groups and possible amphiphilicity of these molecules are significant advantages that could lead to highly sophisticated functional materials with potential usage in biology. Therefore, this project was directed towards the synthesis of advanced LD hybrids and the evaluation of their ability to form ordered functional porous films.

    A degradation and toxicity study was initially conducted on polyester-based 2,2-bis(methylol)propionic acid (bis-MPA) dendrimers under physiological conditions to support the potential usage of these molecules for biological purposes. The materials were found to undergo a relatively fast depolymerization process at pH 7.5. Moreover, the initial dendrimer and its decomposition products were proven to be non-toxic for immune competent cells, allowing for the utilization of these molecules for biological applications.

    A linear-dendritic-linear hybrid library was successfully synthesized from biocompatible poly(ethylene glycol) (PEG), poly(ε-caprolactone) (PCL) and bis-MPA building blocks using a combination of ring-opening polymerization (ROP)and copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC). The materials, consisting of one long PEG block connected to the focal point of the dendron and several PCL arms attached at its periphery, were used to construct ordered porous films using the breath figure method. The polymeric architecture strongly affected the ordering of the films with a more regular morphology obtained from a more flexible polymer. Changing the semi-crystalline PCL to amorphous polylactide (PLA) also permitted the formation of porous arrays. Interestingly, films obtained from inverted structures possessing one long PCL block and several short PEG chains, also presented a regular morphology. Moreover they could be activated to exhibit multiple surface hydroxyl groups.

    To increase the number of orthogonal synthetic methodologies available for the preparation of advanced macromolecules, high molecular weight dendritic macrothiols were synthesized. These molecules were efficiently coupled to a number of core molecules via thiol-ene coupling, generating a comprehensive library of dendritic materials. This approach represents an attractive alternative to the commonly used, but potentially toxic, CuAAC.

    Exploiting the obtained results, a final LD hybrid was synthesized from atom transfer radical polymerization (ATRP) of 2-hydroxyethyl methacrylate (HEMA) derivatives and thiol-ene coupling (TEC) with macrothiols. This macromolecule was successfully utilized to form functional ordered porous arrays and the availability of peripheral alkyne functional groups was demonstrated by efficient coupling with fluorescent Rhodamine-B. The HEMA-backbone allowed for the introduction of cross-linkable azide groups that were used to significantly improve the thermal stability of the films from 50 °C to 200 °C. These materials have the potential to be used in applications such as catalysis, in medicine and as sensors.

  • 4314.
    Walter, Marie V.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Malkoch, Michael
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Simplifying the synthesis of dendrimers: accelerated approaches2012In: Chemical Society Reviews, ISSN 0306-0012, E-ISSN 1460-4744, Vol. 41, no 13, p. 4593-4609Article, review/survey (Refereed)
    Abstract [en]

    Dendrimers are highly branched and monodisperse macromolecules that display an exact and large number of functional groups distributed with unprecedented control on the dendritic framework. Based on their globular structure, compared to linear polymers of the same molecular weight, dendrimers are foreseen to deliver extraordinary features for applications in areas such as cancer therapy, biosensors for diagnostics and light harvesting scaffolds. Of the large number of reports on dendrimer synthesis only a few have reached commercial availability. This limitation can be traced back to challenges in the synthetic paths including a large number of reaction steps required to obtain dendritic structures with desired features. Along with an increased number of reaction steps come not only increased waste of chemical and valuable starting materials but also an increased probability to introduce structural defects in the dendritic framework. This tutorial review briefly covers traditional growth approaches to dendrimers and mainly highlights accelerated approaches to dendrimers. A special focus capitalizes on the impact of the click chemistry concept on dendrimer synthesis and the promise it has to successfully accomplish highly sophisticated dendrimers, both traditional as well as heterofunctional, in a minimum number of chemical steps. It is clear that accelerated synthetic approaches are of greatest importance as these will encourage the scientific community to synthesize and access dendrimers for specific applications. The final goal of accelerated synthesis is to deliver economically justified dendritic materials for future applications without compromising the environmental perspective.

  • 4315.
    Walter, Marie Valérie
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Pontus, Lundberg
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Hult, Daniel
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Hult, Anders
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Malkoch, Michael
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Honeycomb films from amphiphilic linear-dendritic-linear hybrids: effect of branching and of the block lengthManuscript (preprint) (Other academic)
  • 4316.
    Waltersson, Evelina
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Optimization of Expancel Product and Process: Through the use of Multivariate Planning, Data Analysis and Evaluation.2012Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The company Expancel produces expandable microspheres. The microspheres are microscopic spherical particles that consist of a polymer shell encapsulating a gas (the blowing agent). Heat causes the particles to expand. The microspheres have many application areas; they are used as additives in for example thermoplastics, coatings, civil explosives, paper and board. The microspheres are produced through a method called suspension polymerization. In suspension polymerization the starting material for the spheres (monomers, initiator and blowing agent) is through vigorous stirring split into small droplets in a surrounding water phase. Polymerization (initiated by heating the emulsion) occurs inside the microscopic droplets, the monomers react to form the polymer shell with the blowing agent captured inside. After the polymerization the product can be filtered and dried.

    This degree project consisted of two parts. In the first (and major) part the consequences of replacing a chemical used in the production of the microspheres with a more environmentally friendly alternative was examined. The goal was to produce microspheres with an alternative chemical without changing the properties of the microspheres. First five different alternative chemicals were examined in a selected production recipe in 50 ml scale. The software MODDE was used for design of these experiments and analysis of results. Then the best alternative of the five was examined in three other recipes in 50 ml scale. One of the recipes was also examined in 1 liter scale. Several of the alternative chemicals showed good results in the first recipe, but one of them showed more stable results than the others and was selected to proceed with in the other recipes. The conclusion from the experiments with this chemical was that the amount added affected the particle size, and that best results were achieved when adding the chemical before the flocculation step in the process.

    The objective of the second part was to study and evaluate a production process in order to find optimization possibilities. The chosen process was the filtering of the produced microsphere slurry for a specific recipe. Data were collected from the polymerization process, the dewatering process and the characterization analyses performed on the produced microsphere slurry. Production rate was used as response variable. The multivariate analysis software package SIMCA-P+12.0.1 was then used to analyze the data. The conclusion of the multivariate data analysis was that two factors were the most important for explaining the variation in the response variable; the particle size and a polymerization parameter called level.

  • 4317. Walther, A.
    et al.
    Berglund, Lars A.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Biocomposites. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Ikkala, O.
    Biomimetic, large-area, layered composites with superior properties2010In: European Cells and Materials, ISSN 1473-2262, E-ISSN 1473-2262, Vol. 20, no Suppl.3, p. 267-Article in journal (Refereed)
  • 4318.
    Wan, Wei
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Process Technology.
    Engvall, Klas
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Process Technology.
    Weihong, Yang
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Energy and Furnace Technology.
    Novel Model for the Release and Condensation of Inorganics for a Pressurized Fluidized-Bed Gasification Process: Effects of Gasification Temperature2018In: ACS OMEGA, ISSN 2470-1343, Vol. 3, no 6, p. 6321-6329Article in journal (Refereed)
    Abstract [en]

    A model is established to investigate the release and condensation of inorganics for a wood steam/oxygen-blown fluidized-bed gasification process. In the established model, fates of major elements (C, H, O, N, S, and Cl) and minor elements (Al, Ca, Fe, K, Mg, Mn, Na, P, Si, Ti, and Zn) are modeled separately. The composition of gaseous species involving major elements is predicted using Aspen Plus based on a semiempirical model. The release of minor elements and the condensation of inorganics are predicted using software SimuSage. The combination of Aspen Plus with SimuSage is achieved by manually inputting the stream parameters calculated from Aspen Plus into SimuSage. On the basis of this developed model, effects of gasification temperature on the condensation of Na-, K-, and Cl-containing species during gas cooling are studied. Results show that the process model established by combining Aspen Plus and SimuSage is valid and can be used to investigate the release of inorganics during gasification and condensation of inorganics during gas cooling. Under the investigated gasification conditions, regardless of the bed material, there are two temperature ranges within which no salt melt is formed during gas cooling. As the gasification temperature increases, the high-temperature range without salt melt formation becomes successively wider.

  • 4319. Wan, Wei
    et al.
    Engvall, Klas
    Yang, Weihong
    Fredriksson Möller, Björn
    Experimental and modelling studies on condensation of inorganic species during cooling of product gas from pressurized biomass fluidized bed gasification2018In: Energy, Vol. 153, p. 35-44Article in journal (Refereed)
  • 4320. Wang, Baoyuan
    et al.
    Cai, Yixiao
    Xia, Chen
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Kim, Jung-Sik
    Liu, Yanyan
    Dong, Wenjing
    Wang, Hao
    Afzal, Muhammad
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Li, Junjiao
    Raza, Rizwan
    Zhu, Bin
    KTH, School of Computer Science and Communication (CSC), Media Technology and Interaction Design, MID.
    Semiconductor-ionic Membrane of LaSrCoFe-oxide-doped Ceria Solid Oxide Fuel Cells2017In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 248, p. 496-504Article in journal (Refereed)
    Abstract [en]

    A novel semiconductor-ionic La0.6Sr0.4Co0.2Fe0.8O3-delta (LSCF)-Sm/Ca co-doped CeO2 (SCDC) nanocomposite has been developed as a membrane, which is sandwiched between two layers of Ni0.8Co0.15Al0.05Li-oxide (NCAL) to construct semiconductor-ion membrane fuel cell (SIMFC). Such a device presented an open circuit voltage (OCV) above 1.0 V and maximum power density of 814 mW cm(-2) at 550 degrees C, which is much higher than 0.84 V and 300 mW cm(-2) for the fuel cell using the SCDC membrane. Moreover, the SIMFC has a relatively promising long-term stability, the voltage can maintain at 0.966 V for 60 hours without degradation during the fuel cells operation and the open-circuit voltage (OCV) can return to 1.06 V after long-term fuel cell operation. The introduction of LSCF electronic conductor into the membrane did not cause any short circuit but brought significant enhancement of fuel cell performances. The Schottky junction is proposed to prevent the internal electrons passing thus avoiding the device short circuiting problem.

  • 4321.
    Wang, Baoyuan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology. Hubei University, China.
    Cai, Yixiao
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology. Uppsala University, Sweden.
    Xia, Chen
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Liu, Yanyan
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Muhammad, Afzal
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Wang, Hao
    Zhu, Bin
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology. Hubei University, China.
    CoFeZrAl-oxide based composite for advanced solid oxide fuel cells2016In: Electrochemistry communications, ISSN 1388-2481, E-ISSN 1873-1902, Vol. 73, p. 15-19Article in journal (Refereed)
    Abstract [en]

    A novel CoFeZrAl-oxide (CFZA) consisted of FeAl2O4, Co3O4 and ZrO2 was prepared by an auto ignition process, displaying a typical morphology of nanorods. The corresponding fuel cell was constructed by using CFZA as the ion-conducting membrane, incorporated between two layers of Ni0.8Co0.15Al0.05Li-oxide pasted on nickel foam (Ni-NCAL), which was used as both electrodes and current collectors. The fuel cell presented an open circuit voltage of 1.07 V and maximum power density of 631 mW/cm(2) at 600 degrees C. The reduction of FeAl2O4 to oxygen-deficient FeAl2O4 (delta) under H-2 condition contributed to the ionic conduction, then the ionic conductor FeAl2O4 (-) (delta) composited with insulator ZrO2 to further enhance the ionic conductivity due to composite effect.

  • 4322.
    Wang, Baoyuan
    et al.
    Hubei Univ, Fac Phys & Elect Sci, Hubei Collaborat Innovat Ctr Adv Organ Chem Mat, Wuhan 430062, Hubei, Peoples R China.;Royal Inst Technol, Dept Energy Technol, SE-10044 Stockholm, Sweden..
    Cai, Yixiao
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. Royal Inst Technol, Dept Energy Technol, SE-10044 Stockholm, Sweden..
    Xia, Chen
    Royal Inst Technol, Dept Energy Technol, SE-10044 Stockholm, Sweden..
    Liu, Yanyan
    Royal Inst Technol, Dept Energy Technol, SE-10044 Stockholm, Sweden..
    Muhammad, Afzal
    Royal Inst Technol, Dept Energy Technol, SE-10044 Stockholm, Sweden..
    Wang, Hao
    Hubei Univ, Fac Phys & Elect Sci, Hubei Collaborat Innovat Ctr Adv Organ Chem Mat, Wuhan 430062, Hubei, Peoples R China..
    Zhu, Bin
    Hubei Univ, Fac Phys & Elect Sci, Hubei Collaborat Innovat Ctr Adv Organ Chem Mat, Wuhan 430062, Hubei, Peoples R China.;Royal Inst Technol, Dept Energy Technol, SE-10044 Stockholm, Sweden..
    CoFeZrAl-oxide based composite for advanced solid oxide fuel cells2016In: Electrochemistry communications, ISSN 1388-2481, E-ISSN 1873-1902, Vol. 73, p. 15-19Article in journal (Refereed)
    Abstract [en]

    A novel CoFeZrAl-oxide (CFZA) consisted of FeAl2O4, Co3O4 and ZrO2 was prepared by an auto ignition process, displaying a typical morphology of nanorods. The corresponding fuel cell was constructed by using CFZA as the ion-conducting membrane, incorporated between two layers of Ni0.8Co0.15Al0.05Li-oxide pasted on nickel foam (Ni-NCAL), which was used as both electrodes and current collectors. The fuel cell presented an open circuit voltage of 1.07 V and maximum power density of 631 mW/cm(2) at 600 degrees C. The reduction of FeAl2O4 to oxygen-deficient FeAl2O4 (delta) under H-2 condition contributed to the ionic conduction, then the ionic conductor FeAl2O4 (-) (delta) composited with insulator ZrO2 to further enhance the ionic conductivity due to composite effect.

  • 4323. Wang, Cheng
    et al.
    Qian, Chengeng
    Liu, JianNan
    Liberman, Mikhail A.
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
    Influence of chemical kinetics on detonation initiating by temperature gradients in methane/air2018In: Combustion and Flame, ISSN 0010-2180, E-ISSN 1556-2921, Vol. 197, p. 400-415Article in journal (Refereed)
    Abstract [en]

    Different simplified and detailed chemical models and their impact on simulations of combustion regimes initiating by the initial temperature gradient in methane/air mixtures are studied. The limits of the regimes of reaction wave propagation depend upon the spontaneous wave speed and the characteristic velocities of the problem. The present study mainly focus to identify conditions required for the development a detonation and to compare the difference between simplified chemical models and detailed chemistry. It is shown that a widely used simplified chemical schemes, such as one-step, two-step and other simplified models, do not reproduce correctly the ignition process in methane/air mixtures. The ignition delay times calculated using simplified models are in orders of magnitude shorter than the ignition delay times calculated using detailed chemical models and measured experimentally. This results in considerably different times when the exothermic reaction affects significantly the ignition, evolution, and coupling of the spontaneous reaction wave and pressure waves. We show that the temperature gradient capable to trigger detonation calculated using detailed chemical models is much shallower (the size of the hot spot is much larger) than that, predicted by simulations with simplified chemical models. These findings suggest that the scenario leading to the deflagration to detonation transition (DDT) may depend greatly on the chemical model used in simulations and that the Zel'dovich gradient mechanism is not necessary a universal mechanism triggering DDT. The obtained results indicate that the conclusions derived from the simulations of DDT with simplified chemical models should be viewed with great caution.

  • 4324.
    Wang, Da
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Servin, Martin
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Berglund, Tomas
    Algoryx Simulation AB, Umeå, Sweden.
    Mickelsson, Kjell-Ove
    LKAB R&D, Malmberget, Sweden.
    Rönnbäck, Stefan
    Optimation AB, Luleå, Sweden.
    Parametrization and validation of a nonsmooth discrete element method for simulating flows of iron ore green pellets2015In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 283, p. 475-487Article in journal (Refereed)
    Abstract [en]

    The nonsmooth discrete element method (NDEM) has the potential of high computational efficiency for rapid exploration of large design space of systems for processing and transportation of mineral ore. We present parametrization, verification and validation of a simulation model based on NDEM for iron ore green pellet flow in balling circuits. Simulations are compared with camera based measurements of individual pellet motion as well as bulk behavior of pellets on conveyors and in rotating balling drum. It is shown that the NDEM simulation model is applicable for the purpose of analysis, design and control of iron ore pelletizing systems. The sensitivity to model and simulation parameters is investigated. It is found that: the errors associated with large time-step integration do not cause statistically significant errors to the bulk behavior; rolling resistance is a necessary model component; and the outlet flow from the drum is sensitive to fine material adhering to the outlet creating a thick coating that narrows the outlet gaps.

  • 4325. Wang, F.
    et al.
    Deng, S.
    Zhao, J.
    Wang, J.
    Sun, T.
    Yan, Jinyue
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Energy Processes.
    Performance and economic assessments of integrating geothermal energy into coal-fired power plant with CO2 capture2017In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 119, p. 278-287Article in journal (Refereed)
    Abstract [en]

    A novel carbon capture and storage system integrated with geothermal energy was proposed to reduce energy consumption in the post-combustion CO2 capture (PCC) process. Geothermal energy at medium temperature was used to provide the heat required for solvent regeneration. A technical and economic assessment was conducted based on a 300 MWe coal-fired power plant. Additionally, the integrated system was also compared with a stand-alone geothermal power (GP) plant to evaluate individual advantages. Both an enhanced geothermal system (EGS) and a hot sedimentary aquifer (HSA) reservoir were selected to identify the effect of geological properties and heat characteristics on system performance. The results indicated that the geothermal-assisted post-combustion CO2 capture (GPCC) plant exhibited better performance than the PCC plant. The net plant average efficiency increased 5.56% and 4.42% in the EGS scenario and HSA scenario, respectively. Furthermore, the net incremental geothermal efficiency obtained corresponded to 21.34% and 20.35% in the EGS scenario and HSA scenario, respectively. The economic assessment indicated that the GPCC systems in both the EGS scenario and HSA scenario had lower marginal cost of electricity (70.84 $/MWh and 101.06 $/MWh) when compared with that of the stand-alone GP systems (151.09 $/MWh and 101.95 $/MWh). 

  • 4326. Wang, F.
    et al.
    Deng, S.
    Zhao, J.
    Yan, Jinyue
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Energy Processes.
    A novel ammonia-based CO2 capture process hybrid ammonia absorption refrigeration2017In: Proceedings of the 9th International Conference on Applied Energy, Elsevier, 2017, Vol. 142, p. 3734-3740Conference paper (Refereed)
    Abstract [en]

    This paper proposed a novel ammonia-based CO2 capture process hybrid ammonia absorption refrigeration to recovery escaped ammonia in the desorption process. The evaporated ammonia was separated with CO2 via gas-liquid phase, and throttled to produce cooling load. The phase envelope of the CO2 and NH3 mixture was investigated to guide the design of the parameters. A preliminary thermodynamic performance was presented to evaluated the performance. The results showed that the regenerator can regenerate CO2 with a ratio of 90% and this process can produce a cooling load of 113.3 MW. The parameter study indicated that it is competitive with the chilled ammonia process.

  • 4327.
    Wang, Haijuan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Viswanathan, Nurni N.
    Ballal, N. B.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Modelling of Physico-Chemical Phenomena between Gas inside a Bubble and Liquid Metal during Injection of Oxidant Gas2010In: INT J CHEM REACT ENG, ISSN 1542-6580, Vol. 8Article in journal (Refereed)
    Abstract [en]

    Gas liquid reactors are extensively used in many metallurgical processes involving the refining of liquid metals. In these processes, reactions leading to the oxidation of various solutes in liquid metal often compete with each other, which ultimately determine the liquid metal composition. In the present paper, a model has been proposed to simulate the evolution of solute contents in a metallic melt considering mass transfer of solutes in the melt in the vicinity of the bubble, equilibrium at the gas-metal interface and gas composition evolution in the bubble during its ascent through the melt. The composition of solutes at the metal-gas interface in principle can be altered by changing the injected gas composition.

    The model was applied to the case of oxygen injection through a lance into liquid steel-containing C and Cr, aiming sufficient decarburization without much oxidation of Cr to the slag. The Cr loss to the slag by oxidation is generally much more than that expected based on equilibrium thermodynamics applied to the bulk metal and gas. The actual Cr loss, as shown by the present model, is determined by the composition of solutes at the metal-gas interface rather than in the bulk. The effect of change of the partial pressure of oxygen in the bubble by replacing oxygen by carbon dioxide in the injected gas and the corresponding evolution of C and Cr contents in the melt was simulated. Some preliminary experiments were conducted to validate the model predictions. The frame work of the model is generic and can be extended to many gas-liquid metal reactors in liquid metal processing.

  • 4328. Wang, K.
    et al.
    Bai, B.
    Ma, Weimin
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Power Safety.
    A model for droplet entrainment in churn flow2013In: Chemical Engineering Science, ISSN 0009-2509, E-ISSN 1873-4405, Vol. 104, p. 1045-1055Article in journal (Refereed)
    Abstract [en]

    Understanding the mechanism of droplet entrainment is of great importance for the churn flow. So far, the droplet entrainment mechanism has been experimentally studied; however, no detailed model is available for this particular flow pattern. To address this, the author established an analytical model to better understand the drop entrainment in churn flow. In this model, only the entrainment mechanism named shear-off in equilibrium state is considered and detailed analysis performed for the interface stability based on the Kelvin-Helmholtz instability and force balance acting on the wave crest. The model has been verified using experimental data and different parameters (e.g., pipe diameter, gas and liquid flowrate and pressure) influencing the entrainment is presented. The author proposed a more accurate and reasonable formula for the entrained rate in churn flow based on the existing formula for annular flow. The model developed in this paper predicts the entrainment mechanism under churn flow condition to an accuracy of 30% which is essential for the development of mechanistic models to predict the dryout condition in the future.

  • 4329. Wang, K.
    et al.
    Bai, B.
    Ma, Weimin
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Power Safety.
    Huge wave and drop entrainment mechanism in gas-liquid churn flow2013In: Chemical Engineering Science, ISSN 0009-2509, E-ISSN 1873-4405, Vol. 104, p. 638-646Article in journal (Refereed)
    Abstract [en]

    A profound knowledge of huge wave and droplet entrainment mechanism is crucial for the thorough study on the gas-liquid churn flow. Although studies have shown that the entrained fraction is high in churn flow and reaches the minimum around the churn-annular transition, the underlying mechanism of the drop entrainment in churn flow is still not well explored. To address this, we investigated the properties of the huge waves and the droplet entrainment in two vertical pipes with the inner diameter of 19. mm and 34. mm under churn flow conditions. We found that the flooding of the film was a characteristic of the churn flow throughout the regime. In addition, increasing the gas or liquid flow rate could lead to the transition from churn flow to annular flow or reverse to slug flow, providing the insight into the differences among slug, churn and annular flow. We also discussed the film instability under different flow conditions and tried to reveal the physical mechanism based on the instability analysis. In our study, the bag breakup and the ligament breakup were observed to coexist. The analysis of the liquid distribution in the cross-section of the pipes not only revealed the variations of the entrained fraction of churn flow from that of annular flow, but also indirectly illustrated the differences between their breakup mechanisms. Moreover, the wave properties (amplitude and frequency) were also analyzed in detail.

  • 4330. Wang, Ke
    et al.
    Bai, Bofeng
    Cui, Jiahuan
    Ma, Weimin
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Power Safety.
    A physical model for huge wave movement in gas-liquid churn flow2012In: Chemical Engineering Science, ISSN 0009-2509, E-ISSN 1873-4405, Vol. 79, p. 19-28Article, review/survey (Refereed)
    Abstract [en]

    A complete knowledge of the huge wave in churn flow is of great importance for the characterization of its entrainment. Huge wave in churn flow is experimentally identified as a highly disturbed wave; however, no specific model is available for this particular wave. Based on the force balance over the wave, we established an analytical model to study its growth and levitation and analyzed the effects of the parameters (including gravity, pressure force of gas and liquid, wall shear stress and interfacial shear stress) on the wave and the gas and liquid flow field. We proposed that the boundary layer in liquid film is more likely to be turbulent rather than laminar and the gas pressure force is the most influential factor. The proposed model was verified qualitatively and quantitatively. We hence theoretically concluded that the churn flow is characterized by the flooding of the film, the flow reversal is attributed to the transition to the annular flow and the pressure gradient decreases with the increase of the gas flow rate. These findings provided insight into the distinction between the churn flow and the annular flow. The wave properties (amplitude and velocity) were analyzed in detail and the churn/annular transition occurred at U* = 1.12. The model helps understand the droplet entrainment in churn flow which is essential for the development of mechanistic models to predict the dryout condition.

  • 4331. Wang, Lei
    et al.
    Duan, Lele
    Ambre, Ram B.
    Daniel, Quentin
    Chen, Hong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Sun, Junliang
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Das, Biswanath
    Thapper, Anders
    Uhlig, Jens
    Diner, Peter
    Sun, Licheng
    A nickel (II) PY5 complex as an electrocatalyst for water oxidation2016In: Journal of Catalysis, ISSN 0021-9517, E-ISSN 1090-2694, Vol. 335, p. 72-78Article in journal (Refereed)
    Abstract [en]

    A Ni-PY5 [PY5 = 2,6-bis(1,1-bis(2-pyridyl)ethyl)pyridine)] complex has been found to act as an electrocatalyst for oxidizing water to dioxygen in aqueous phosphate buffer solutions. The rate of water oxidation catalyzed by the Ni-PY5 is remarkably enhanced by the proton acceptor base HPO42-, with rate constant of 1820 M-1 s(-1). Controlled potential bulk electrolysis with Ni-PY5 at pH 10.8 under an applied potential of 1.5 V vs. normal hydrogen electrode (NHE) resulted in dioxygen formation with a high faradaic efficiency over 90%. A detailed mechanistic study identifies the water nucleophilic attack pathway for water oxidation catalysis.

  • 4332.
    Wang, Lei
    et al.
    KTH Royal Institute of Technology, Department of Chemistry.
    Fan, Ke
    KTH Royal Institute of Technology, Department of Chemistry.
    Chen, Hong
    KTH Royal Institute of Technology, Department of Chemistry.
    Daniel, Quentin
    KTH Royal Institute of Technology, Department of Chemistry.
    Philippe, Bertrand
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Sun, Licheng
    KTH Royal Institute of Technology, Department of Chemistry; Dalian University of Technology (DUT), DUT-KTH Joint Education and Research Center on Molecular Devices, State Key Laboratory of Fine Chemicals.
    Towards efficient and robust anodes for water splitting: Immobilization of Ru catalysts on carbon electrode and hematite by in situ polymerization2017In: Catalysis Today, ISSN 0920-5861, E-ISSN 1873-4308, Vol. 290, p. 73-77Article in journal (Refereed)
    Abstract [en]

    Ru-bda based molecular water oxidation catalysts 1 and 2 (H2bda = 2,2′–bipyridine–6,6′–dicarboxylic acid) containing a thiophene group are attached to the surfaces of electrodes by the method of electropolymerization. The Ru-bda molecular catalyst functionalized graphite carbon electrode can catalyze water oxidation efficiently under a overpotential of ca 500 mV to obtain current density of 5 mA cm−2; and the similarly functionalized photoelectrode based on α-Fe2O3 (hematite) film can work as an photoanode for light driven water splitting.

  • 4333.
    Wang, Liwei
    et al.
    State Key Laboratory of Materials-Oriented Chemical Engineering and College of Chemical Engineering , Nanjing Tech University , Nanjing, P. R. China.
    Yu, Liang
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Zeng, Changfeng
    College of Mechanical and Power Engineering , Nanjing Tech University , Nanjing , P. R. China. .
    Wang, Chongqing
    State Key Laboratory of Materials-Oriented Chemical Engineering and College of Chemical Engineering , Nanjing Tech University , Nanjing, P. R. China.
    Zhang, Lixiong
    State Key Laboratory of Materials-Oriented Chemical Engineering and College of Chemical Engineering , Nanjing Tech University , Nanjing, P. R. China.
    Fabrication of PAA-PETPTA Janus Microspheres with Respiratory Function for Controlled Release of Guests with Different Sizes2018In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 34, no 24, p. 7106-7116Article in journal (Refereed)
    Abstract [en]

    Poly(acrylic acid)–poly(ethoxylated trimethylolpropane triacrylate) (PAA–PETPTA) Janus microspheres with “respiratory” function for controlled release were prepared by polymerization of acrylic acid–ethoxylated trimethylolpropane triacrylate (AA–ETPTA) Janus microdroplets in a continuous oil phase in a simple capillary-based microfluidic device with the assistance of UV radiation. The flow rate ratios of AA and ETPTA phases and surfactant content in the continuous oil phase have a significant effect on the structure of the Janus microspheres. PAA part in the Janus microspheres has respiratory function for loading and release due to the different stimuli responses to different pHs. The hollow structure of PETPTA part with different sizes of opening serves as the host materials for PAA and could control release rate further due to the different opening sizes. The obtained PAA–PETPTA Janus microspheres showed high rhodamine B (RhB) loading of 860 mg g–1 and different controlled-release behavior in water with different pHs. The release rate increases with the increase of pH and the contact area of PAA part with water. The maximum controlled-release time for RhB was about 3 h in water with pH of 5. In addition, the Janus microspheres also showed controlled-release behavior for larger size guests, e.g., 150 nm polystyrene beads, which indicated a wide range of application. The loading and release behaviors for guests, for instance, for RhB, have almost no change even after six times of reuse, which indicated a high stability.

  • 4334.
    Wang, Miao
    et al.
    RISE, Innventia.
    Sjöholm, Elisabeth
    RISE, Innventia.
    Li, Jiebing
    RISE, Innventia.
    On lignin reactivity quantification for lignin substitution of phenol in preparation of phenol-formaldehyde polymer2014Conference paper (Refereed)
  • 4335. Wang, Shuai
    et al.
    Wang, Jie
    Zhu, Xiaojuan
    Wang, Jianqiang
    Terasaki, Osamu
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Wan, Ying
    Size-control growth of thermally stable Au nanoparticles encapsulated within ordered mesoporous carbon framework2016In: Cuihuà xuébào, ISSN 0253-9837, E-ISSN 1872-2067, Vol. 37, no 1, p. 61-72Article in journal (Refereed)
    Abstract [en]

    Simultaneously controlling the size of Au nanoparticles and immobilizing their location to specific active sites while hindering migration and sintering at elevated temperatures is a current challenge within materials chemistry. Typical methods require the use of protecting agents to control the properties of Au nanoparticles and therefore it is difficult to decouple the influence of the protecting agent and the support material. By functionalizing the internal surface area of mesoporous carbon supports with thiol groups and implementing a simple acid extraction step, we are able to design the resulting materials with precise control over the Au nanoparticle size without the need for the presence of any protecting group, whilst simultaneously confining the nanoparticles to within the internal porous network. Monodispersed Au nanoparticles in the absence of protecting agents were encapsulated into ordered mesoporous carbon at various loading levels via a coordination-assisted self-assembly approach. The X-ray diffractograms and transmission electron microscopy micrographs show that the particles have controlled and well-defined diameters between 3 and 18 nm at concentrations between 1.1 and 9.0 wt%. The Au nanoparticles are intercalated into the pore matrix to different degrees depending on the synthesis conditions and are stable after high temperature treatment at 600 degrees C. N-2 adsorption-desorption isotherms show that the Au functionalized mesoporous carbon catalysts possess high surface areas (1269-1743 m(2)/g), large pore volumes (0.78-1.38 cm(3)/g) and interpenetrated, uniform bimodal mesopores with the primary larger mesopore lying in the range of 3.4-5.7 nm and the smaller secondary mesopore having a diameter close to 2 nm. X-ray absorption near extended spectroscopy analysis reveals changes to the electronic properties of the Au nanoparticles as a function of reduced particle size. The predominant factors that significantly determine the end Au nanoparticle size is both the thiol group concentration and subjecting the as-made materials to an additional concentrated sulfuric acid extraction step.

  • 4336.
    Wang, Shule
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Energy and Furnace Technology.
    Persson, Henry
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Energy and Furnace Technology.
    Weihong, Yang
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Energy and Furnace Technology.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Energy and Furnace Technology.
    Effect of H2 as Pyrolytic Agent on the Product Distribution during Catalytic Fast Pyrolysis of Biomass Using Zeolites2018In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029Article in journal (Refereed)
    Abstract [en]

    Bio-oil generated from catalytic fast pyrolysis or hydrotreating processes represents one of the most promising alternatives to liquid fossil fuels. The use of H2 as carrier gas in the pyrolysis of biomass requires further research to study the catalytic fast pyrolysis reactions in the case of using reactive atmosphere. In this work, pyrolysis experiments with lignocellulosic biomass have been performed in a fixed bed reactor in H2 and N2 atmospheres with/without HZSM-5 additions to investigate the influence of the pyrolytic agents during fast pyrolysis of biomass and upgrading of pyrolytic vapors over a zeolitic catalyst. It was found that in a H2 atmosphere, H2 was consumed in both noncatalytic and catalytic pyrolysis processes, respectively. Higher yields of nonaqueous liquids and permanent gases are obtained in a H2 atmosphere compared to a N2 atmosphere. A catalytic pyrolysis process using HZSM-5 in a H2 atmosphere increased the production of polymer aromatic hydrocarbons and suppressed the production of monomer aromatic hydrocarbons compared to similar tests performed in a N2 atmosphere. The results show an overall increased activity of HZSM-5 in the reactive H2 atmosphere compared to a N2 atmosphere.

    The full text will be freely available from 2019-07-31 11:49
  • 4337.
    Wang, Xin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Protein Interactions with Metal Surfaces: Adsorption and Metal Release2015Doctoral thesis, comprehensive summary (Other academic)
  • 4338.
    Wang, Yan
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Pretreatment and Enzymatic Treatment of Spruce: A functional designed wood components separation for a future biorefinery2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The three main components of wood, namely, cellulose, hemicellulose, and lignin, can be used in various areas. However, since lignin covalently crosslinks with wood polysaccharides creating networks that is an obstacle for extraction, direct extraction of different wood components in high yield is not an easy matter. One potential approach to overcome such obstacles is to treat the wood with specific enzymes that degrade the networks by specific catalysis. However, the structure of wood is so compact that the penetration of the wood fibers by large enzyme molecules is hindered. Thus, the pretreatment of wood prior to the application of enzymes is necessary, for “opening” the structure.

    One pretreatment method that was performed in this thesis is based on kraft pulping, which is a well-established and industrialized technique. For untreated wood, the wood fibers cannot be attacked by the enzymes. A relatively mild pretreatment was sufficient for wood polysaccharides hydrolyzed by a culture filtrate. A methanol-alkali mixture extraction was subsequently applied to the samples that were pretreated with two types of hemicellulases, Gamanase and Pulpzyme HC, respectively. The extraction yield increased after enzymatic treatment, and the polymers that were extracted from monocomponent enzyme-treated wood had a higher degree of polymerization. Experiments with in vitro prepared lignin polysaccharide networks suggested that the increased extraction was due to the enzymatic untying. However, the relatively large loss of hemicellulose, particularly including (galacto)glucomannan (GGM), represents a problem with this technique. To improve the carbohydrate yield, sodium borohydride (NaBH4), polysulfide and anthraquinone were used, which increased the yields from 76.6% to 89.6%, 81.3% and 80.0%, respectively, after extended impregnation (EI). The additives also increased the extraction yield from approximately 9 to 12% w/w wood. Gamanase treatment prior to the extraction increased the extraction yield to 14% w/w wood.

    Sodium dithionite (Na2S2O4) is an alternative reducing agent for the preservation of hemicelluloses because it is less expensive than metal hydrides and only contains sodium and sulfur, which will not introduce new elements to the recovery system. Moreover, Na2S2O4has the potential to be generated from black liquor. Na2S2O4 has some preservation effect on hemicelluloses, and the presence of Na2S2O4 also contributed to delignification. The extraction yield increased to approximately 15% w/w wood. Furthermore, Na2S2O4 has been applied in the kraft pulping process of spruce. The yield and viscosity increased, while the Klason lignin content and kappa number decreased, which represents a beneficial characteristic for kraft pulp. The brightness and tensile strength of the resulting sheets also improved. However, the direct addition of Na2S2O4 to white liquor led to greater reject content. This problem was solved by pre-impregnation with Na2S2O4 and/or mild steam explosion (STEX) prior to the kraft pulping process. Following Na2S2O4 pre-impregnation and mild STEX, the obtained kraft pulp had substantially better properties compared with the properties exhibited after direct addition of Na2S2O4 to the white liquor.

    The wood structure opening efficiency of mild STEX alone was also tested. The accessibility of the wood structure to enzymes was obtained even at very modest STEX conditions, according to a reducing sugar analysis, and was not observed in untreated wood chips, which were used as a reference. The mechanical effect of STEX appears to be of great importance at lower temperatures, and both chemical and mechanical effects occur at higher STEX temperatures. 

  • 4339.
    Wang, Yan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Azhar, Shoaib
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Lindström, Mikael E.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Henriksson, Gunnar
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Stabilisation of polysaccharides during alkaline pretreatment of wood combined with enzyme-supported extractions in a biorefinery2015In: Journal of wood chemistry and technology, ISSN 0277-3813, E-ISSN 1532-2319, Vol. 35, no 2, p. 91-101Article in journal (Refereed)
    Abstract [en]

    Specific enzymes have been demonstrated to increase the possibilities for extracting wood polymers. Enzymatic treatment requires an open wood structure, which was achieved by extended impregnation of the wood. However, some of the hemicelluloses, primarily glucomannan, and lignin were lost during the impregnation. To improve the carbohydrate yield, three glucomannan modification agents: sodium borohydride, polysulphide and anthraquinone, were used, which increased the yields of the impregnated materials from 76.6% to 89.6%, 81.3% and 80.0%, respectively. Through the use of additives, most of the glucomannan could be retained in the wood while still allowing the enzymes to penetrate the wood and attack the polymers. The additives also increased the extraction yield from 9 to 12% w/w wood. Gamanase treatment prior to the extraction increased the extraction yield to 14%. Of the three stabilising agents, sodium borohydride was the most efficient, providing the highest extraction yields.

  • 4340.
    Wang, Yan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Jedvert, Kerstin
    Chalmers University of Technology.
    Lindström, Mikael E.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Theliander, Hans
    Chalmers University of Technology.
    Henriksson, Gunnar
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Dithionite impregnation combined with mild steam explosion of spruce wood – an improved version of kraft pulpingManuscript (preprint) (Other (popular science, discussion, etc.))
    Abstract [en]

    Norway spruce (Picea abies) wood chips were impregnated with water or sodium dithionite (Na2S2O4) and were subsequently subjected to a mild steam explosion (STEX) treatment at four or seven bar for ten minutes. In order to evaluate the combined effect of Na2S2O4 and STEX, kraft cooking was performed on samples pre-treated with different combinations of impregnation and STEX. Carbohydrate composition, Klason lignin content, kappa number, intrinsic viscosity, pulp yield, brightness and tensile strength (on pulp sheets) were tested and compared. The results showed that an impregnation with Na2S2O4 combined with mild STEX had a good effect on the delignification during kraft pulping, shown by lower kappa numbers and lower Klason lignin content. The viscosity of the pulp samples of Na2S2O4 plus STEX was lower than the water impregnated and non-STEX pulps. However, the lower viscosity did not influence the strength of the pulp since the tensile index was still high. The Na2S2O4 plus STEX pulp sheets also showed the highest brightness value.

  • 4341.
    Wang, Yan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Lindström, Mikael E.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Lawoko, Martin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Theliander, Hans
    Chalmers University of Technology.
    Henriksson, Gunnar
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Improved yield and pulp properties by adding sodium dithionite in kraft pulping of spruceManuscript (preprint) (Other academic)
    Abstract [en]

    The reductive effect of sodium dithionite (Na2S2O4) on sugar model compounds was investigated. Results revealed that parts of open aldehyde forms in the sugars were reduced to the corresponding alditols by Na2S2O4. The possibilities to improve yield and other properties of spruce kraft pulp by addition of Na2S2O4 were also investigated. The yield, carbohydrate compositions, Klason lignin, intrinsic viscosity, kappa number of pulp, tensile strength and optical properties of resultant paper sheets were analysed. Compare with the normal kraft pulp without Na2S2O4 addition, yield together with viscosity were increased, while Klason lignin and kappa number were decreased. The brightness and tensile strength of paper sheet were also improved. The only drawback for adding sodium dithionite to white liquor was higher reject content. This could be overcome by pre-impregnation with Na2S2O4 before kraft pulping process. The possibility of applying Na2S2O4 in industrial kraft pulp mill was discussed, including how to generate Na2S2O4 from black liquor thereby closing the process.

  • 4342.
    Wang, Yan
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Wohlert, Jakob
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Bergenstråhle-Wohlert, Malin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Kochumalayil, Joby J.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Berglund, Lars A.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Tu, Yaoquan
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Molecular Adhesion at Clay Nanocomposite Interfaces Depends on Counterion Hydration-Molecular Dynamics Simulation of Montmorillonite/Xyloglucan2015In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 16, no 1, p. 257-265Article in journal (Refereed)
    Abstract [en]

    Nacre-mimetic clay/polymer nanocomposites with clay platelet orientation parallel to the film surface show interesting gas barrier and mechanical properties. In moist conditions, interfacial adhesion is lowered and mechanical properties are reduced. Molecular dynamic simulations (MD) have been performed to investigate the effects of counterions on molecular adhesion at montmorillonite clay (Mnt)-xyloglucan (XG) interfaces. We focus on the role of monovalent cations K+, Na+, and Li+ and the divalent cation Ca2+ for mediating and stabilizing the Mnt/XG complex formation. The conformation of adsorbed XG is strongly influenced by the choice of counterion and so is the simulated work of adhesion. Free energy profiles that are used to estimate molecular adhesion show stronger interaction between XG and clay in the monovalent cation system than in divalent cation system, following a decreasing order of K-Mnt, Na-Mnt, Li-Mnt, and Ca-Mnt. The Mnt clay hydrates differently in the presence of different counterions, leading to a chemical potential of water that is highest in the case of K-Mnt, followed by Na-Mnt and Li-Mnt, and lowest in the case of Ca-Mnt. This means that water is most easily displaced from the interface in the case of K-Mnt, which contributes to the relatively high work of adhesion. In all systems, the penalty of replacing polymer with water at the interface gives a positive contribution to the work of adhesion of between 19 and 35%. Our work confirms the important role of counterions in mediating the adsorption of biopolymer XG to Mnt clays and predicts potassium or sodium as the best choice of counterions for a Mnt-based biocomposite design.

  • 4343.
    Wang, Yuming
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering. Nanjing Tech Univ, Peoples R China.
    Jafari, Mohammad Javad
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Wang, Nana
    Nanjing Tech Univ, Peoples R China.
    Qian, Deping
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Zhang, Fengling
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Ederth, Thomas
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Moons, Ellen
    Karlstad Univ, Sweden.
    Wang, Jianpu
    Nanjing Tech Univ, Peoples R China.
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Huang, Wei
    Nanjing Tech Univ, Peoples R China.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Light-induced degradation of fullerenes in organic solar cells: a case study on TQ1:PC71BM2018In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 6, no 25, p. 11884-11889Article in journal (Refereed)
    Abstract [en]

    The stability of organic solar cells (OSCs) is critical for practical applications of this emerging technology. Unfortunately, in spite of intensive investigations, the degradation mechanisms in OSCs have not been clearly understood yet. In this report, we employ a range of spectroscopic and transport measurements, coupled with drift-diffusion modelling, to investigate the light-induced degradation mechanisms of fullerene-based OSCs. We find that trap states formed in the fullerene phase under illumination play a critical role in the degradation of the open-circuit voltage (V-OC) in OSCs. Our results indicate that the degradation is intrinsic to the fullerenes in OSCs and that alternative acceptor materials are desired for the development of stable OSCs.

  • 4344.
    Wang, Zeng
    et al.
    Luleå tekniska universitet.
    Lidström-Larsson, Margareta
    Grahn, Mattias
    Holmgren, Allan
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Zeolite coated ATR crystals for new applications in FTIR-ATR spectroscopy2004In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, no 24, p. 2888-2889Article in journal (Refereed)
  • 4345.
    Wang, Zhao
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    A weighted correlation approach of the density functional theory for an inhomogeneous fluid at an interface2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This doctoral thesis presents a newly developed density functional theory (DFT), i.e., the weighted correlation approach (WCA), to study the structural and thermodynamic properties of an inhomogeneous fluid at an interface. The WCA approach provides a generic formulation to evaluate the change of the single-particle direct correlation function in terms of a series of pair direct correlation functions weighted by different correlation-weight functions with adjustable correlation-weight factors. When applied practically, however, an approximation of the pair direct correlation function has to be made, together with appropriate definitions of the weighted densities and the choices of the correlation-weight functions. Despite this seeming complexity, it is shown that the WCA approach can be regarded as a generalization of the classic density functional approaches and this enables us to develop and apply DFT methods in different ways. For demonstration purposes, several implementations of the WCA approach are proposed and applied to predict the density distribution of an inhomogeneous fluid at an interface. The WCA approach is also employed with a novel pressure expression to investigate the inhomogeneous fluid-mediated interaction pressure for different cases. The WCA calculations from the above applications suggest that it is a successful approach for describing the structural and thermodynamic properties of an inhomogeneous fluid at an interface, as compared to the published results of the Monte Carlo simulations, density functional methods and experimental data.

  • 4346.
    Wang, Zhao
    KTH.
    A weighted correlation approach of the density functional theory for an inhomogeneous fluid at an interface2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This doctoral thesis presents a newly developed density functional theory (DFT), i.e., the weighted correlation approach (WCA), to study the structural and thermodynamic properties of an inhomogeneous fluid at an interface. The WCA approach provides a generic formulation to evaluate the change of the single-particle direct correlation function in terms of a series of pair direct correlation functions weighted by different correlation-weight functions with adjustable correlation-weight factors. When applied practically, however, an approximation of the pair direct correlation function has to be made, together with appropriate definitions of the weighted densities and the choices of the correlation-weight functions. Despite this seeming complexity, it is shown that the WCA approach can be regarded as a generalization of the classic density functional approaches and this enables us to develop and apply DFT methods in different ways. For demonstration purposes, several implementations of the WCA approach are proposed and applied to predict the density distribution of an inhomogeneous fluid at an interface. The WCA approach is also employed with a novel pressure expression to investigate the inhomogeneous fluid-mediated interaction pressure for different cases. The WCA calculations from the above applications suggest that it is a successful approach for describing the structural and thermodynamic properties of an inhomogeneous fluid at an interface, as compared to the published results of the Monte Carlo simulations, density functional methods and experimental data.

  • 4347.
    Wang, Zhao
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Liu, Longcheng
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Neretnieks, Ivars
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    The weighted correlation approach for density functional theory: a study on the structure of the electric double layer2011In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 23, no 17, p. 175002-Article in journal (Refereed)
    Abstract [en]

    Within the framework of density functional theory, a weighted correlation approach is developed in order to obtain the density distributions of an inhomogeneous fluid. It results in a formally exact expression, by means of the concept of a weighted pair correlation function, used to evaluate the change of the single-particle direct correlation function of the system relative to that of a reference state. When applying the approach for practical use, however, an approximation of the pair correlation function has to be made, along with an appropriate definition of a weight function. Noticeably, combining this approach with fundamental measure theory gives rise to a new method, which we call the FMT/WCA-k(2) approach, for studying the structural and thermodynamic properties of a charged hard-sphere fluid subjected to a spatially varying external potential. Application of the FMT/WCA-k(2) approach in a range of electrolyte concentrations and surface charge densities, against the Monte Carlo simulations, shows that it is superior to the typical approaches of density functional theory in predicting the ionic density profiles of both counter-ions and co-ions near a highly charged surface. It is capable of capturing the fine features of the structural properties of the electric double layers, to well reproduce the layering effect and the charge inversion phenomenon, also in strongly coupled cases where divalent counter-ions are involved. In addition, it is found that the FMT/WCA-k(2) approach even has an advantage over the anisotropic, hyper-netted chain approaches in giving better agreement with the Monte Carlo results.

  • 4348.
    Wang, Zhao
    et al.
    KTH.
    Liu, Longcheng
    KTH, Kemisk apparatteknik.
    Neretnieks, Ivars
    KTH, Kemisk apparatteknik.
    The weighted correlation approach for density functional theory: a study on the structure of the electric double layer2011In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 23, no 17, article id 175002Article in journal (Refereed)
    Abstract [en]

    Within the framework of density functional theory, a weighted correlation approach is developed in order to obtain the density distributions of an inhomogeneous fluid. It results in a formally exact expression, by means of the concept of a weighted pair correlation function, used to evaluate the change of the single-particle direct correlation function of the system relative to that of a reference state. When applying the approach for practical use, however, an approximation of the pair correlation function has to be made, along with an appropriate definition of a weight function. Noticeably, combining this approach with fundamental measure theory gives rise to a new method, which we call the FMT/WCA-k(2) approach, for studying the structural and thermodynamic properties of a charged hard-sphere fluid subjected to a spatially varying external potential. Application of the FMT/WCA-k(2) approach in a range of electrolyte concentrations and surface charge densities, against the Monte Carlo simulations, shows that it is superior to the typical approaches of density functional theory in predicting the ionic density profiles of both counter-ions and co-ions near a highly charged surface. It is capable of capturing the fine features of the structural properties of the electric double layers, to well reproduce the layering effect and the charge inversion phenomenon, also in strongly coupled cases where divalent counter-ions are involved. In addition, it is found that the FMT/WCA-k(2) approach even has an advantage over the anisotropic, hyper-netted chain approaches in giving better agreement with the Monte Carlo results.

  • 4349.
    Wang, Zhao
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Wu, Guochao
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Jönsson, Leif J.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Effects of impregnation of softwood with sulfuric acid and sulfur dioxide on chemical and physical characteristics, enzymatic digestibility, and fermentability2018In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 247, p. 200-208Article in journal (Refereed)
    Abstract [en]

    Hydrothermal pretreatment improves bioconversion of lignocellulose, but the effects of different acid catalysts are poorly understood. The effects of sulfuric acid (SA) and sulfur dioxide (SD) in continuous steam pretreatment of wood of Norway spruce were compared in the temperature range 195 degrees C-215 degrees C. The inhibitory effects of the pretreatment liquid on cellulolytic enzymes and Saccharomyces cerevisiae yeast were higher for SD-than for SApretreated material, and the inhibitory effects increased with increasing pretreatment temperature. However, the susceptibility to cellulolytic enzymes of wood pretreated with SD was 2.0-2.9 times higher than that of wood pretreated with SA at the same temperature. Data conclusively show that the superior convertibility of SDpretreated material was not due to inhibition phenomena but rather to the greater capability of the SD pretreatment to reduce the particle size through partial delignification and cellulose degradation. Particle size was shown to be correlated with enzymatic digestibility (R-2 0.97-0.98).

  • 4350.
    Wang, Zheng
    Luleå tekniska universitet.
    Molecular sieve films and zoned materials2003Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Molecular sieve films and colloidal particles may have great potential for further utilization in novel technological sophisticated applications such as structured catalysts, sensors and membranes. The work presented in this thesis concerns the synthesis molecular sieve films and the crystallization of zoned MFI materials for novel catalyst and sensor applications. The seeding method developed at the division has been modified for the preparation of MFI and FAU type films on a variety of steel substrates ranging from ordinary carbon steel to highly corrosion resistant stainless steel. The films were characterized by SEM, XRD and gas adsorption techniques. The results revealed that the type of steel did not affect the film morphology, the thickness or the preferred orientation of the crystals, whereas the thermal stability was dependent on the steel. Films on various stainless steel supports were stable during calcination, whereas films on carbon steel supports peeled off upon rinsing after calcination because a relatively thick magnetite/hematite film formed. Pre-calination of carbon steel improved the zeolite film stability upon calcination. Zoned MFI materials (colloidal zoned MFI crystals and zoned films) were synthesized in this work in order to improve the catalytic performance of MFI. A two-step crystallization method was developed to prepare zoned MFI materials, in which precursor ZSM-5 colloidal particles or film were grown in a silicalite-1 synthesis solution directly or after acid treatment. It was shown that zoned MFI materials did not form when the ZSM-5 surface had a high aluminum content. In this case, polycrystalline aggregates or a sandwich film formed due to secondary nucleation. After reducing the aluminum content to half by acid treatment of ZSM-5, secondary nucleation of new silicalite-1 crystals was inhibited and zoned MFI material was obtained.

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