Corrosion is a mechanism that highly reduces the lifetime of metals in different environments, especially in water or moisture environment. The worldwide maintenance cost due to corrosion is estimated in billions of dollars per year, and actual solutions in terms of coating usually contains toxic or environmentally harmful species. With an always increasing restriction by environmental restraints and regulations, a sustainable solution is urgently needed.

Chitosan, easily obtained from chitin, the second most abundant biopolymer on earth, can be the solution to many problems. Crustacean shell waste is one of the major sources of chitin. Its resource efficiency, biocompatibility, and versatile physicochemical properties for chelation and crosslinking make chitosan a promising candidate as matrix material for biobased anticorrosive application.

The purpose of the Master Thesis is to combine the properties of chitosan with the high porosity of bee pollen as anticorrosive agent carrier to obtain a fully sustainable solution for anticorrosive protection. The objective of this very ambitious project is to produce a composite material with a triple action: anticorrosive protection of metal surfaces, self-healing property of the coating and anti- biofouling activity.

Results show that a biopolymer composite in forms of suspension or coatings with all desired components could be achieve. Specifically, a biopolymer nanocomposite composed of chitosan matrix, embedded with pollen grains that were loaded with anticorrosion agent 2- mercatobenzothiazole (MBT) in advance, and with zinc oxide nanoparticles have been produced.

The physicochemical characterization of the biopolymer composite and its coatings, as well as electrochemical impedance spectroscopy (EIS) measurements on stainless steel plate with such coatings, suggest that a uniform and compact coating is obtained. Despite its good hydrophobicity with maximum contact angle 134.32 ± 3.84° with top coating, the chitosan nanocomposite coating is still permeable to water, partially because of the relatively big size of pollen (ca. 20 μm) that introduces gaps and interferes integrity of the coating. Therefore, a full immersion corrosion resistance is not achieved. In conclusion, phase transfer of hydrophobic pollen into hydrophilic chitosan matrix, MBT loading in pollen, ZnO encapsulation in chitosan, as well as crosslinking of chitosan, were successfully carried out. A coating based on such biopolymer nanocomposite is prepared on stainless steel and investigated on its anti-corrosion property. Future work will be choosing a proper sized pollen as a microcontainer to enhance the integrity of the coating, and eventually endow the coating with the three-in-one function, i.e., anticorrosion, antimicrobial, and self-healing.

Aluminum coatings can provide galvanic cathodic protection for several metals and alloys. In order to be a suitable protective solution on structural components, the mechanical integrity must be preserved. In particular, the fatigue properties are a challenge for thermal spray protective coatings on mechanical structures. To address the issue of the fatigue integrity of 7075 aluminum alloy with an arc sprayed protective coating, different surface preparations prior to arc spraying were considered. In the present work, a feasibility study was performed using laser ablation as a surface preparation technique before or during arc spraying of coatings through collaboration between the LERMPS laboratory in France, the National Research Council of Canada and the Royal Military College of Canada. Both fatigue and adhesive properties of aluminum coatings were evaluated in relation to substrate surface preparation techniques including laser ablation (PROTAL® process), grit blasting and shot peening. Results indicate that a combination of key conditions including using nitrogen as the arc spray gas, shot peening and proper laser energy density for ablation provides high fatigue resistance of metallic coated 7075 alloy substrates. Specimens prepared under these conditions show a similar fatigue resistance to uncoated substrates. © Canadian Institute of Mining, Metallurgy and Petroleum.

For the purpose of modeling internal corrosion of the stainless steel fuel pins in fast nuclear reactors, the present work presents a thermodynamic description of the Fe–Ni–Te system modeled via the Calphad method. The liquid phase was modeled using the ionic 2-sublattice liquid model. Only binary parameters were optimized in the β2, δ and τ solid phases, to fit the isothermal section at 600 °C. The liquid did not require much adjustment from the extrapolation from the binary Fe–Te, Ni–Te and Fe–Ni systems. The paper presents a re-optimization of the Fe–Te liquid description in order to remove inverted liquid miscibility gaps at high temperatures. The resulting phase diagrams reproduce experimental isothermal sections well, and fits liquidus and solidus data very well. The description will be incorporated into the Thermodynamics of Advanced Fuels - International Database (TAF-ID). This will then be coupled with the Germinal system code to model the fission-product induced corrosion in nuclear fuel pins.

In the pursuit of safer, more environmentally friendly and sustainable forms of energy production for our ever growing demands, a type of nuclear reactor cooled by liquid metal instead of water is under development. Specific to this type of reactor are special forms of corrosion of the material that encapsulates the fuel pins in the reactor core, called Fuel-Clad Chemical Interaction (FCCI) or Fission Product-induced Liquid Metal Embrittlement (FPLME). This is a complicated chemical process which has been observed in the fuel pins of Sodium-cooled Fast neutron Reactors (SFR). In order to predict the consequences and impact of this corrosion, it must be simulated, which requires a description of the thermodynamics of the elements involved, i.e. Cr--Cs--Fe--Ni--Te--O. This thesis covers the development of a thermodynamic description of the Cr--Fe--Ni--Te system by model parameter optimizations supported by first-principles calculations and experimental investigations.

Grenrören i en motor utsätts för stora termiska och mekaniska belastningar, vilka gör att grenrören ofta spricker. Idag kan inte sprickbildningen fullständigt uttydas ur beräkningarna, syftet med arbetet är därför att se om dessa kan förbättras genom att använda en mer avancerad krypmodell än den som används idag.

Ett förslag till krypmodell har tagits genom att studera ett antal i litteraturen funna modeller. De som valts ut är modeller enligt Norton, Bailey-Norton, Marin-Pao, Picket och Findley. Parametrarna i de olika modellerna har bestämts genom kurvanpassning av enaxliga prov på de aktuella grenrörsmaterialen. Resultaten visar att modellerna enligt Marin-Pao, Picket och Findley alla kan beskriva mätkurvorna nästan exakt. Problem uppstår dock med att man får parametrar som beror av både spänning och temperatur. Av dessa tre modeller anses Marin-Pao vara den bästa, då det är den av de tre som har minst antal parametrar. Utvärderingen ger vidare att Norton är den modell som är enklast, och beaktat över alla prover, den vars resultat bäst ansluter sig till mätdata. Valet görs att gå vidare med både Marin-Paos och Nortons modell.

De två aktuella modellerna har lagts in som subrutiner till FE-programmet ABAQUS. Tester av modellerna görs först på ett litet kubiskt element och sedan på hela grenröret. Jämförelser görs mellan Norton, Marin-Pao och den modell som används idag – ”Two-layer viscoplasticity model”. Såväl Marin-Paos modell som Nortons beskriver verkligheten bättre än den idag använda modellen och av de båda är Nortons modell den som mest tillfredställande speglar verkligheten. Det är dessutom den modell som är mest stabil och beräkningsmässigt effektivast. Som en rekommendation inför fortsatt arbete föreslås därför användning av Nortons modell, samt ett utökat antal krypprover.

Test comparisons have been carried out between road material laboratories in Sweden for particle density and water absorption according to SS-EN 1097-6:2013 in 2020. The comparison was made with four materials, two with the grading 11/16 mm and two with the grading 0/4 mm. Each participant performed double tests of each material. There were 49 laboratories participating.

Generally, are there small variations for particle density between the participants. The coefficient of variation1 is less than 1%. For the water absorption, the variations between the participating laboratories are relatively large. However, this can partly be explained with that the results consists of low values and the "natural" variation is almost as great as the results, about 0.3%. Water absorption has just under 30% in variation coefficient1for the coarser materials in grading 11/16 mm and about 60–70% for the finer ones in grading 0/4 mm.

Clearly anomalous participants for particle density for the finer materials is laboratory number 20 with very low results, where even laboratory No. 6 is located low. For water absorption, is it mainly laboratories 33, 12 and 50 that most clearly stand out in a negative way. In general, are the repeatability and the reproducibility, in this comparing analysis better or equal with SS-EN 1097-6:2013.

To study the correlation between the degradation of unbound base layer and mechanical properties (primarily Los Angeles test but also micro Deval test) a number of materials has been exposed by wheel load of VTI’s Heavy Vehicle Simulator (HVS). The first round was performed during the winter 2010–2011 and the second round during the following winter. In each round there were five materials tested. In the second round there were four new materials and one “old” as reference material. In this report results from round II will be presented, as well as some common results from both of the rounds, I and II. The results from round 1 are presented in VTI notat 4-2011. (Håkan Arvidsson: Comparison between the Los Angeles value and degradation from traffic load).The degradation has been defined as the difference in grain size distribution before and after HVS test. The degradation can be described in several ways. One way is as the difference in the area under the grain size distribution curve, another way is to sum the difference in percentage passing for all sieves or a few, e.g. the increase of fines by using results from the sieves 0.063–0.125 mm. The rutting has been measured by laser. The rutting is inversed proportional to the increase of fines. The increase of fines probably increases the stability in this quite coarse base layer grading. The materials with less increasing of fines have most of the hard minerals (quarts and plagioclase). The conclusion of these two tests on unbound base layer materials is that you partly can explain the degradation (change of grain size distribution) with mechanical properties (like Los Angeles and micro Deval). The correlations confirm this explanation and depend partly on an extreme material. Hellman et al (2013) show that degradation and crushing of the aggregates during compaction have a correlation with mechanical properties by studying microstructure and degree of crushing in microscope. Therefor the conclusion is that there is a degradation and crushing of aggregates in unbound base layer materials exposed by compaction and heavy traffic load.

This degree project was performed by students of the Innovation and design engineering programme on Karlstad University, Sweden. Group members have been Johan Arvidsson, Marcus Leidefeldt and Tobias Unosson. The degree project consisted of 20 weeks of work of which 5 was an individual study in literature. The project carried out during the spring of 2006.

Assigner for the project was Hedenberg Advanced Vehicle Design, HAVD, who is a development company serving the vehicle industry and specializing in interior parts and trim. Contacts were Björn Hedenberg and Ingemar Carlson, HAVD. Examiner at Karlstad University was Lennart Wihk. The project was also collaboration together with VOLVO Truck Car Corp in Gothenburg.

The task the students were given was to improve and develop a new solution for truck drivers, getting in and out of high trucks. A goal with the project was to build a functioning prototype on a VOLVO truck to be shown at the exhibit for degree projects in Karlstad, May 2006.

In this project the students participated in a project management course given by HAVD in their facilities. The group toke part of a new development method originated from the vehicle industry. This method was used as a frame for the entire project and consisted of three phases, the idea phase, research phase and the realization phase. Between each phase of the project there was a point called a gate, in which important decisions were maid in the group together with HAVD.

The project resulted in a mechanical lift, mounted onto the side of the truck transporting the driver safely up and down. The solution was named ECA, Ergonomic Cabin Access. Drawings for the concept and its mounting were completed along with an economic calculation. The final result is developed with focus on the driver ergonomics with a sensible construction using available components. The core in the construction is the so called linear motion drive. This device transforms a rotating force into a linear motion. The concept was adapted to fit a VOLVO truck by replacing the trucks previous three footsteps.

The final concept was presented at HAVD and Karlstad University at the exhibit for degree projects, 30 May 2006. The concept could not however be built into a prototype due to financial reasons. The degree project ECA resulted in drawings, renderings, animations and this academic report.

Ion trapping under charge insertion-extraction is well-known to degrade the electrochemical performance of oxides. Galvano-static treatment was recently shown capable to rejuvenate the oxide, but the detailed mechanism remained uncertain. Here we report on amorphous electrochromic (EC) WO3 thin films prepared by sputtering and electrochemically cycled in a lithium-containing electrolyte under conditions leading to severe loss of charge exchange capacity and optical modulation span. Time-of-flight elastic recoil detection analysis (ToF-ERDA) documented pronounced Li+ trapping associated with the degradation of the EC properties and, importantly, that Li+ detrapping, caused by a weak constant current drawn through the film for some time, could recover the original EC performance. Thus, ToF-ERDA provided direct and unambiguous evidence for Li+ detrapping.

The construction of mechanism maps for hot-isostatic pressing is described. Maps are constructed for a number of materials of commercial and scientific interest: a tool steel, a superalloy, Al₂O₃, and ice. They allow the processes involved in hot-isostatic pressing to be examined, and suggest ways of picking optimum combinations of pressure, temperature, and time to give maximum density.

This dissertation can be divided into two main parts. The first deals with the hot working conditions of mild steels in powder forging, the second with the deformation behaviour of powder forged products; both monolithic and compound parts are studied. Hot forging of low alloy steel powders makes it possible to produce complicated parts with properties comparable with homogeneous forged parts, whilst reducing the machining operations necessary to a minimum. This powder forging technique is a high production rate method, and can only be applied to mass produced components. It also gives the possibility of complete reconstruction of the shape of the part. Forging of porous preforms however require certain precautions to be made to prevent working faults and to optimize the densification process. These things are therefore studied with some interest. In order to compete with other high production rate methods such as hot forging, the powder forged parts must be economically advantageous. Therefore the most attractive parts to be produced are those in which substantial material is saved, where most machining operations can be excluded and in which material of substantial structure is required. A method to produce compound structural parts of high strength hardened steel and ductile mild steel from alloyed powders is presented. It involves the manufacture of compound preforms by forging and their heat treatment to produce an optimal structure. On examining the deformation behaviour of compound parts produced, a substantial rise in the fracture toughness is seen, which is associated with the interface between hard and ductile material zones.

Shape control during HIP is influenced by many variables such as container properties, powder filling method, initial density, temperature and pressure cycle, etc. Experiments have been performed using ASP30 aimed at the study of how to produce parts near net shape through the optimization of these variables. Special care was given to the powder filling and laser welded sheet metal containers of special geometry was used. The results indicate that the temperature and pressure cycles during the first stages of the HIP-process have a pronounced effect on the final shape. A HIP-cycle which will result in a close shape is also presented. Graphs

Models for analysing shape changes during the HIPping of powder compacts enclosed in preshaped containers are presented. Two limiting mechanisms are considered: homogeneous densification and the motion of a sharply defined densification front through the compact as HIPping proceeds. The shape changes and shrinkages occurring in a number of simple one, two, and three dimensional shapes are analysed and illustrated. Although some of the assumptions implicit in the model are at variance with the conditions found in practice, it is concluded that useful insights are provided into the shape changes occurring during HIPping

Densification in a HIP cycle is non-uniform because of the temperature gradient in the powder body. This gradient gives rise to a densification front, which moves from the surface inward. The densification front will, in reality, be more or less diffuse, but may be considered as extremely sharp for the purpose of modelling the shape and dimensional changes of idealized powder bodies. The geometrical considerations presented show that extreme shape change can occur in a practical HIP cycle. As an example, a square cross-section powder body acquires a star-like shape, in which the angle at the edges depends solely on the densification ratio. The results may serve as a base for an improved powder capsule design, taking into account the effects of non-uniform densification

The densification of a powder body in a HIP process is non-uniform because of an existing temperature gradient in the powder body. This gradient gives rise to a densification front, which moves from the surface inwards. This front will, in reality, be more or less diffuse, but may be considered as extremely sharp for the purpose of modelling the shape and dimensional changes of idealized powder bodies. The geometrical considerations presented show that extreme shape change can occur in a practical HIP cycle. As an example, a cubic powder body will get a star-like shape, in which the edge angles will depend solely on the densification ratio. Considered are the effects caused by uniform and non-uniform heating in the densification of various powder bodies defined by flat and/or curved body surfaces, and the results may serve as a base for an improved understanding of the effects of non-uniform densification and its importance for the powder body design.

Stress and strain are studied using the finite element method in the dimensioning of prestrained die tools for powder compaction. The die geometry has been varied and the die has also been subjected to different types of load. The study shows that the mean pressure transverse to the pressing direction is a dimensioning factor, but that the distribution itself is not very important. For a linear pressure distribution, the stress and strain within the die will differ little from results produced under the assumption of an exponential pressure distribution. Attention is also paid to the possibilities of treating the three-dimensional situation in a real die by different methods of two-dimensional FEM analysis

A new paradigm is slowly making its way into society, affecting our material practice as designers. Materials selection in design and product development has for a long time been dominated by a purely technical approach, mainly focusing on properties and performance. With the increasing evidence of climate change, waste and pollution, environmental effects, we are slowly realizing that unsustainable consumption of materials is no longer an alternative. Previous studies of material practices, both within design educations and the design profession, has primarily dealt with the development of material related methods. This thesis has focused on gaining an in-depth understanding of material practices within design processes, in order to develop a pedagogical framework that facilitates the development of reflective material practices in design education. There are four primary aims of the research presented in this licentiate thesis: (1) ascertain obstacles in the traditional ways of teaching materials to design students, (2) to bridge the differences in language, research culture and pedagogic approaches in design education, (3) to investigate current professional material practices in industrial design, and (4) to develop a new material framework for teaching reflective material practices for design students. During the project, the material framework has been tested and evaluated in two mandatory material courses with first and second year bachelor students from Product Design education over a period of four academic years. A comparative case study was conducted with five design consultancies. The qualitative interviews were transcribed and analysed using category zooming. The outcomes of this research are: (1) a new pedagogic framework for teaching materials to Product Design students in higher education, and (2) insights into professional practices of selecting and designing with materials. The pedagogic model A Material Framework for Product Design is designed to facilitate the development of reflective material practices in design education. The Framework consist of four levels: (1) a pedagogical foundation based on Experiential Learning theory that provide a framework for how to approach teaching and learning, (2) designing and structuring learning activities, (3) creating learning environments that facilitate learning activities, and (4) defining learning objectives, assessment of learning outcomes and detecting signs of learning. The main insights from the study of professional practices suggest: (1) that risk management has a major influence on the material selection process, (2) that negotiations of project boundaries in the ‘fuzzy’ pre-design phase has crucial influence on the risk management aspect of the material criteria activities, and (3) a lack of awareness, that design briefs usually outline material criteria expressed as sensorial characteristics, which are later translated by engineering into final material criteria used for the material selection process. The findings implies that design students would benefit from developing reflective material practices in design education.

Data for carbide dissolution, grain growth and martensite formation in the heat-affected zone of a weld can be assembled into a diagram showing the extent of each, for different weld cycles, and at different points in the zone. The diagrams are based on elementary kinetic models for grain growth and carbide dissolution, integrated over the weld cycle; and on experimental data. The sets of poorly-known kinetic constants which appear in such a treatment are determined by fitting the equations to data from real or simulated welds, at certain fixed points. Diagrams are presented for six steels. As well as summarising much data they allow the effect of change in weld procedure, or of preheat, to be predicted.

Crack propagation in various woods has been examined by scanning electron microscopy, and the observations related to measurements of fracture toughness. It is found that the toughness is related in a simple way to the density of the wood, which is explained by a straightforward model. The apparent fracture toughness of wood for cracks that lie normal to the grain is larger, by a factor of about 10, than that for cracks which propagate parallel to the grain. This difference can be explained in terms of the fracture mechanics of very anisotropic solids

Data for carbide dissolution and grain growth in the heat affected zone of a weld can be assembled into a diagram showing the extent of each, for different weld cycles, and at different points in the zone. The diagrams are based on elementary kinetic models for grain growth and carbide dissolution, integrated over the weld cycle. The sets of kinetic constants which appear in such a treatment are determined by fitting the equations to data from real or simulated welds, at certain fixed points. Diagrams are presented for six steels. As well as summarizing much data they allow the effect of change in weld procedure, or of preheat, to be predicted.

Surfaces can be treated with a scanning laser beam to modify their properties. The beam subjects the near-surface to a thermal cycle with an amplitude and shape which depends on the process variables: the beam size, energy, scan rate and on whether the laser is pulse or continuous, and the chemistry and metallurgy of the steel. Approximate solutions to the equations of heat flow are combined with kinetic models to predict the near-surface structure and hardness of plain carbon steels after laser treatment. The results are assembled into diagrams which show immediately the combination of process variables for a desired surface structure and the associated hardness profile

A technique for following sialon formation in situ by high temperature x-ray diffraction (HT-XRD) was developed. The composition chosen for study was an yttrium α-sialon with x = 0.4. Powder compacts containing silicon nitride, aluminum nitride and yttria powders were pre-sintered at 1350 °C and then studied by HT-XRD at temperatures between 1450 and 1580 °C and nitrogen pressures of 0.11 MPa. The furnace was made from graphite coated with porous silicon nitride/silicon carbide. The coating prevented silicon carbide formation in the sample up to 1600 °C. X-ray diffraction results show the formation of a Y₁₀Al₂Si₃O₁₈N₄ phase at 1350 °C, which dissolved to form α-sialon and other phases at higher temperatures. The amounts of α-sialon formed are similar to the amounts reported by other authors. An empirical method was used for the calculation of activation energy for the silicon nitride to α-sialon transformation and resulted in a value of 330 kJ mol^-1.

A powder mixture of α-Si3N4, AlN and Y2O3 corresponding to an yttrium α-sialon composition, Y0.4Si10.2Al1.8O0.6N15.4, was sintered both in a high temperature X-ray diffraction unit and in a regular sintering furnace. X-ray analysis was performed and it was shown that high temperature X-ray diffraction can be used to monitor the kinetics of the α-sialon phase formation during sintering at temperatures between 1450 and 1580 °C as the reactions take place. A variety of yttrium-rich intermediate and secondary phases are formed during sintering; those formed in the HT-XRD unit were not the same as those formed in the regular sintering furnace, but they do not significantly influence the overall reaction sequence or the amount of α-sialon formed. Quantitative analysis of the acquired data was used to evaluate the kinetics of the α-sialon phase formation; the estimated activation energy of the initial stage α-sialon formation was 330kJ/mol. After this initial stage of relatively rapid α-sialon formation the process became inhibited

Todays demands on silicon nitride based materials for structural applications focus on microstructures rendering high strengths and reliability at reasonable costs. This work was mainly aimed at production of sialons for these types of applications by nitridation with subsequent sintering. For this purpose both the influence of different factors on sialon formation and the effect of additives in nitriding was studied, as well as different sintering methods. Y-alfa-sialons with x=0.1 to 0.9 in the formula Yx(Sil2-4.5x,Al4.5x)(01.5x,N 16-1.5x) prepared from silicon nitride powders were sintered in different ways. The crystalline phase composition varied from alfa/beta sialon at x=0.2 to alfa sialon at x=0.4 and alfa sialon + polytypes at x=0.8. The highest alfa-sialon content and density was obtained for x=0.4 with an excess of yttria after sintering 1h at 1750°C and post HIPing 1h at 1750°C and 200 MPa. No glass encapsualtion was needed as closed porosity was obtained in the sintering step. Less residual glass was also present after this processing than when just HIPing. Sintering without pressure, however was not enough to densify the material. Sintering experiments by HT-XRD and in a conventional furnace of an x=0.4 alfa-sialon composition without excess yttria, showed that the amount of alfa-sialon formed was relatively insensitive to small changes in composition. Assuming that the formation mechanisms during the early stages of sintering (first 90-120 min) did not change with time and temperature, therefore made it possible to determine the kinetics of alfa-sialon formation. The activation energy was estimated as 330 kJ/mol. The effect of additives on nitridation was studied by adding silica or additives for sialon formation (AlN, Al2O3, Y2O3, CaO) to silicon. Formation of silicon oxynitride in the case of silica additions and sialon in the case of sialon additions was then observed after nitriding. The amounts of sialon formed depended on the liquid phase properties of the different compositions and the nitriding conditions. Fast nitridation resulted in more sialon formation. By nitriding with different schedules it was shown that this formation could be controlled and also that the nitridation could be speeded up when additives were present. Large amounts of additives made the pore size distribution insensitive to nitriding gas composition. The presence of hydrogen in the gas, however, did increase the amount of reaction at low temperatures and thereby influenced the phase composition. Densification of the materials nitrided with silica present was not possible by pressureless sintering and standard glass encapsulated HIPing. Most of the nitrided sialon compositions, on the other hand, sintered well by most sintering methods used at temperatures of 1850°C, and resulted in homogeneous microstructures. Sinter HIPing rendered unusually elongated grains in the (alfa-sialon (x=0.4), while the beta-sialon (z=2) had high grain aspect ratios for all sintering methods. HIPing at 1750°C gave the highest densities in most cases but resulted in inhomogeneities in the alfa-sialon. These looked very similar to inhomogeneities obtained when AlN additive powder with larger grain sizes was used. This work shows that nitridation with subsequent sintering of sialon compositions is a very promising way of manufacturing high performance structural ceramics based on silicon nitride.

Samples pressed from fine powders of Si, Si + SiO2, Si + kaolinite and Si + SiO2 + Al2O3 were nitrided by both the nitrogen demand method and a constant rate of heating using a graphite resistance furnace at temperatures of 1100 to 1450 °C. The nitridation rate for different compositions and input parameters were determined by continuously monitoring the time, temperature and pressure within the furnace. By comparing the different compositions, the effect of impurities, silica and particle size on nitriding rate, phase composition and percent theoretical weight gain were determined. Compositions containing high purity additives were found to nitride at higher temperatures and to be more susceptible to weight loss during nitridation. The prime cause for low weight gains was determined to be volatilization of silicon out of the samples. Si2N2O/O′ Sialon was formed in all compositions containing the as-used additives and acted to retain the oxygen within the sample.

Crack velocities as a function of KI were studied for gel-derived vitreous silica sintered from relative densities of 0.23 to full density. The gels were formed by mixtures of colloidal silica, potassium soluble silicate and formamide. Slow crack growth was studied by the constant moment double cantilever beam test. Data were analysed in terms of the log v-K plots and the equation v = (v0/A1)exp(-E*+bA2KI)/RT. Experiments showed that porosity had a major effect on the slope of these plots but only a minor effect on the log intercept. The change in log intercept was considered in terms of the pre-exponential A1, the change in slope by the term A2. A2 varied from a value of 1 at full density to a value of 6.71 at 0.23 relative density

This article reports on plasma treatment of SU-8 epoxy in order to enhance adhesive strength for metals. Its samples were fabricated on standard silicon wafers and treated with (O₂ & Ar) RF plasma at a power of 25W at a low pressure of (3×10^-3 torr) for different time spans (10 sec – 70 sec). The sample surfaces were characterized in terms of contact angle, surface (roughness and chemistry) and using a tape test. During the contact angle measurement, it was observed that the contact angle was reduced from 73° to 5° (almost wet) and 23° for (O₂ & Ar) treated samples, respectively. The RMS surface roughness was significantly increased by 21.5% and 37.2% for (O₂ & Ar) treatment, respectively. A pattern of metal squares was formed on the samples using photolithography for a tape test. An adhesive tape was applied to the samples and peeled off at 180^o. The maximum adhesion results, more than 90%, were achieved for the O₂-treated samples, whereas the Ar-treated samples showed no change. The XPS study shows the formation of new species in the O₂-treated sample compared to the Ar-treated samples. The high adhesive results were due to the formation of hydrophilic groups and new O₂ species in the O₂-treated samples, which were absent in Ar-treated samples.

Iron content can cause severe challenges through zinc production from zinc sulfide concentrate. The zinc industry extensively uses the jarosite precipitation process (JPP) to precipitate dissolved iron and remove it before transferring the solution to downstream stages. Precipitating agents (PAs) play an essential role in the JPP. However, surprisingly, no study compares the efficiency of various PAs on an industrial scale. As an innovative approach, this investigation compares the technical and economic aspects of using various sodium and ammonium compounds (hydroxides, carbonates, bicarbonates, sulfates, and bisulfates) as typical PAs for the JPP at the Bafgh Zinc Smelting Company (BZSC) plant. Experimental results revealed that ammonium hydroxide, with 90.85% iron removal efficiency, had the highest performance, and sodium bisulfate and ammonium bisulfate had the lowest efficiency (74.54 and 77.13%, respectively). However, since ammonium hydroxide is a corrosive PA, it is not a promising alternative to sodium sulfate (with both economic and safety issues). Based on technical and economic assessments, sodium carbonate (84.31% iron removal efficiency) showed the highest potential for an efficient JPP.

Titanium and Ti alloys have poor tribological properties and deposition of a well adherent diamond coating is a promising way to solve this problem. But diamond film deposition on pure titanium and Ti alloys is always difficult due to the high diffusion coefficient of carbon in Ti, the large mismatch in their thermal expansion coefficients, the complex nature of the interlayer formed during diamond deposition, and the difficulty of achieving very high nucleation density. A nano-crystalline diamond (NCD) film can resolve Ti and Ti alloys weak tribological performance due to its smooth surface. A well-adhered NCD film was successfully deposited on pure Ti substrate by using a microwave plasma assisted chemical vapor deposition (MWPCVD) system in the environment of Ar, CH4 and H2 gases at a moderate temperature. Detailed experimental results on the preparation, characterization and successful deposition of the NCD film on pure Ti are discussed

Diamond films with fine grain size and good quality were successfully deposited on pure titanium substrate using a novel two-step growth technique in microwave plasma-assisted chemical vapor deposition (MWPCVD) system. The films were grown with varying the methane (CH4) concentration at the stage of bias-enhanced nucleation (BEN) and nano-diamond film deposition. It was found that nano-diamond nuclei were formed at a relatively high methane concentration, causing a secondary nucleation at the accompanying growth step. Nano-diamond film deposition on pure titanium was always very hard due to the high diffusion coefficient of carbon in Ti, the big difference between thermal expansion coefficients of diamond and Ti, the complex nature of the interlayer created during diamond deposition, and the difficulty in achieving very high nucleation density. A smooth and well-adhered nano-diamond film was successfully obtained on pure Ti substrate. Detailed experimental results on the synthesis, characterization and successful deposition of the nano-diamond film on pure Ti are discussed

The use of titanium alloys for aerospace and biomedical applications could increase if their tribological behavior was improved. The deposition of an adherent diamond coating can resolve this issue. However, due to the different thermal expansion coefficients of the two materials, it is difficult to grow adherent thin diamond layers on Ti and its metallic alloys. In the present work microwave plasma chemical vapor deposition (MWPCVD) was used to deposit smooth nano-crystalline diamond (NCD) film on pure titanium substrate using Ar, CH4 and H2 gases at moderate deposition temperatures. Of particular interest in this study was the exceptional adhesion of approximately 2 μm-thick diamond film to the metal substrate as observed by indentation testing up to 150 kg load. The friction coefficient, which was measured with a cemented carbide ball of 10 mm diameter with 20 N load, was estimated to be around 0.04 in dry air. Morphology, surface roughness, diamond crystal orientation and quality were obtained by characterizing the sample with field emission electron microscopy (FE-SEM), atomic force microscopy (AFM), X-ray diffraction (XRD) and Raman spectroscopy, respectively.

Nanocrystalline diamond (NCD) film deposition on pure titanium and Ti alloys is extraordinarily difficult because of the high diffusion coefficient of carbon in Ti, the large mismatch in their thermal expansion coefficients, the complex nature of the interlayer formed during diamond deposition, and the difficulty to achieve very high nucleation density. In this investigation, NCD films were successfully deposited on pure Ti substrate by using a novel substrate pretreatment of ultrasonic scratching in a diamond powder-ethanol suspension and by a two-step process at moderate temperature. It was shown that by scratching with a 30-μm diamond suspension for 1 h, followed by a 10-h diamond deposition, a continuous NCD film was obtained with an average grain size of about 200 nm. Detailed experimental results on the preparation, characterization, and successful deposition of the NCD films on Ti were discussed

In this study, hydropiercing after hydroforming and prior to unloading was investigated. The primary purpose of this study was to investigate how the used hydropiercing method and the selected material and process parameters affect the hole quality. Hydropiercing inwards, hydropiercing by folding the ’scrap’ piece inwards and hydropiercing outwards were tested. The tube material was extruded AA6063-T4. The tube diameter and wall thickness were 107 mm and 2.5 mm respectively. Straight 1110-mm long tubes of this material were first hydroformed at 1300 bar and then hydropierced. Assuming that the largest (in magnitude) acceptable deflection at the hole edge is 0.2 mm, hydropiercing inwards at ≥ 1300 bar yield the best hole quality. However, the remaining scrap piece (in the tube) causes a handling problem that must be solved.

Rapportsammanställning av föredrag vid forskardagarna i Linköping 1999-01-13--14 beträffande:

• aktuell geoteknisk FoU inom infrastrukturen
• fordonssäkerhet
• väginformatik
• avståndshållning i landsvägstrafik
• geoteknisk riskvärdering
• vad hände i Vagnhärad?
• funktionshindrade och tafik

Within the field of neuroprosthetics the possibility to use implanted electrodes for communication with the nervous system is explored. Much effort is put into the material aspects of the electrode implant to increase charge injection capacity, suppress foreign body response and build micro sized electrode arrays allowing close contact with neurons. Conducting polymers, in particular poly(3,4-ethylene dioxythiophene) (PEDOT), have been suggested as materials highly interesting for such neural communication electrodes. The possibility to tailor the material both mechanically and biochemically to suit specific applications, is a substantial benefit with polymers when compared to metals. PEDOT also have hybrid charge transfer properties, including both electronic and ionic conduction, which allow for highly efficient charge injection.

Part of this thesis describes a method of tailoring PEDOT through exchanging the counter ion used in electropolymerisation process. Commonly used surfactants can thereby be excluded and instead, different biomolecules can be incorporated into the polymer. The electrochemical characteristics of the polymer film depend on the ion. PEDOT electropolymerised with heparin was here determined to have the most advantageous properties. In vitro methods were applied to confirm non-cytotoxicity of the formed PEDOT:biomolecular composites. In addition, biocompatibility was affirmed for PEDOT:heparin by evaluation of inflammatory response and neuron density when implanted in rodent cortex.

One advantage with PEDOT often stated, is its high stability compared to other conducting polymers. A battery of tests simulating the biological environment was therefore applied to investigate this stability, and especially the influence of the incorporated heparin. These tests showed that there was a decline in the electroactivity of PEDOT over time. This also applied in phosphate buffered saline at body temperature and in the absence of other stressors. The time course of degradation also differed depending on whether the counter ion was the surfactant polystyrene sulphonate or heparin, with a slightly better stability for the former.

One possibility with PEDOT, often overlooked for biological applications, is the use of its semi conducting properties in order to include logic functions in the implant. This thesis presents the concept of using PEDOT electrochemical transistors to construct textile electrode arrays with in-built multiplexing. Using the electrolyte mediated interaction between adjacent PEDOT coated fibres to switch the polymer coat between conducting and non conducting states, then transistor function can be included in the conducting textile. Analogue circuit simulations based on experimentally found transistor characteristics proved the feasibility of these textile arrays. Developments of better polymer coatings, electrolytes and encapsulation techniques for this technology, were also identified to be essential steps in order to make these devices truly useful.

In summary, this work shows the potential of PEDOT to improve neural interfaces in several ways. Some weaknesses of the polymer and the polymer electronics are presented and this, together with the epidemiological data, should point in the direction for future studies within this field.

Electrodes intended for neural communication must be designed to meet boththe electrochemical and biological requirements essential for long term functionality. Metallic electrode materials have been found inadequate to meet theserequirements and therefore conducting polymers for neural electrodes have emergedas a field of interest. One clear advantage with polymerelectrodes is the possibility to tailor the material to haveoptimal biomechanical and chemical properties for certain applications. To identifyand evaluate new materials for neural communication electrodes, three chargedbiomolecules, fibrinogen, hyaluronic acid (HA), and heparin are used ascounterions in the electrochemical polymerization of poly(3,4-ethylenedioxythiophene) (PEDOT). The resultingmaterial is evaluated electrochemically and the amount of exposed biomoleculeon the surface is quantified. PEDOT:biomolecule surfaces are also studiedwith static contact angle measurements as well as scanning electronmicroscopy and compared to surfaces of PEDOT electrochemically deposited withsurfactant counterion polystyrene sulphonate (PSS). Electrochemical measurements show that PEDOT:heparinand PEDOT:HA, both have the electrochemical properties required for neuralelectrodes, and PEDOT:heparin also compares well to PEDOT:PSS. PEDOT:fibrinogen isfound less suitable as neural electrode material.

Mathematical modelling using differential equations is an important tool to predict the behaviorof vanadium redox batteries, since it may contribute to improve the device performance and leadto a better understanding of the principles of its operation. Modelling can be complementedby asymptotic analysis as a mean to promote reductions or simplifications that make modelsless complex. Such simplifications are useful in this context, whereas these models usuallyaddresses one cell only – the smallest operating unit – while real applications demand tensor hundreds cells implying on larger computational requirements. In this research, severaloptions for asymptotic reductions were investigated and, applied to different models, were ableto speed up the processing time in 2.46× or reduce the memory requirements up to 11.39%. Thecomputational simulations were executed by COMSOL Multiphysics v.4.4, also by in-housecode developed in MATLAB. The validation of results was done by comparing it to experimentalresults available in literature. Additionally, correlating the results provided by COMSOL withthe ones arising from the implemented sub-routines allowed to validate the developed algorithm.Key-words:

Calcium phosphate cements (CPCs) have a great potential in the treatment of bone disorders due to their excellent biocompatibility. Although CPCs are promising when implanted in vivo, there is poor correlation between in vitro and in vivo studies. This could be because most conventional in vitro systems lack a 3D architecture, or dynamic conditions (i.e. a continuous refreshment stream). The aim of this work is to embed CPCs into a microfluidic system and evaluate ion and protein exchange at different flow rates.

The controlled synthesis of ordered anionic surfactant templated mesoporous silica with cubic Ia3 structure (AMS-6) is reported via prolonged periods of hydrothermal treatment (HT). The cubic Ia3 mesophase transforms to hexagonal p6mm after 8 days of HT at 100 °C. Surprisingly, the hexagonal phase is stable only for a limited period after which a reversal to the cubic Ia3 mesostructure is observed. Characterization methods such as powder X-ray diffraction (XRD), electron microscopy (SEM, TEM), N₂-isotherms, magic-angle spinning (MAS) ²⁹Si NMR spectroscopy, and thermogravimetric analysis (TGA) have been employed to follow structural and textural changes of the materials prepared. Data show that the resultant mesostructure and its textural properties are highly dependent on the period of HT with less unit-cell shrinkage on calcination after extensive HT. Furthermore, evidence of two different solid−solid phase mechanisms during HT is presented. The initial transition is consistent with a restructuring of the surfactant packing and a depletion of the organic moieties from the organo-silica wall as evident from ²⁹Si NMR spectroscopy. The return to the bicontinuous cubic phase is driven by changes in charge matching at the organic−inorganic interface as a result of increases in the polymerization of the silica wall. The textural properties, and in particular the presence or absence of surface porosity, has been controlled through variations in hydrothermal treatment. These are associated with specific growth directions of cubic AMS-6 crystals. The synthetic method described allows us to easily prepare phase pure and intermediate mesostructured nanoparticles.

The synthesis of cubic Pmn mesocaged solid templated by cetyltrimethyl ammonium bromide (C₁₆TMABr) surfactant by direct cocondensation of (3-aminopropyl)triethoxysilanes (APES) under strong alkaline conditions is reported. The novel route gives direct incorporation of amino functional groups on the porous silica wall, and the structural formation has been followed by means of in situ SAXS studies performed at a synchrotron beam line. Data shows that a molar ratio of C₁₆TMABr/APES = 0.6 favors the formation of 3D cubic mesocaged solid with Pmn symmetry which transforms to a cylindrical mesoporous phase with p6mm symmetry at higher molar ratios. Further structural evaluation has been performed by means electron crystallography (EC). Reconstructed 3D models based on EC show the presence of spherical cages (A-cages, 45 Å) and ellipsoidal cages (B-cages, 48 × 43 Å) whereby every cage in the unit cell is connected to 14 nearest cages with a window size of 18 Å. Finally, a mechanism is proposed, denoted S⁺N^oI⁻, in which penetration of the neutral aminopropyl moiety within the micellar corona is responsible for the formation of the Pmn phase, accounting for the formation of the hexagonal phase at higher molar ratios and higher temperatures. In comparison to other mesocaged materials with the same symmetry this structure possesses a more open porous network which will help assess its potential in a variety of applications discussed herein.