The thesis primarily focuses on the pressure influence on the reaction rate of char gasification using laboratory thermogravimetric analysis (TGA). It discusses also the gasification of char with a mixture of gasifying agents (CO2 + steam) under a pressure of 40 bar and temperatures up to 1100°C, which has not been reported in the literature to the best of found knowledge. The first section investigates the pressure impact on char gasification kinetics by varying the total and partial pressure of the gasifying agent. The second section investigates the effect of gasifying agent at 40 bar and combining the pyrolysis step in the investigation, which was done in-situ under inert atmosphere. Then, mixtures of the two gasifying agents were used for the gasification in separate experiments. The third section uses raw coal as material and gives attention to the char structure formed after the pyrolysis under the high pressure. The fourth section includes measurements for char characteristics during the gasification reaction and compares them with the reference char data performed previously in this research group under atmospheric pressure.:Abstract 1. Introduction 1 1.1 Scope of the thesis 1 1.2 Layout of the thesis 2 2. Literature Review 4 2.1 Background 4 2.2 Coal and gasification 5 2.2.1 Coal classification and characteristics 5 2.2.2 Introduction to gasification process 7 2.2.3 Coal Analysis 10 2.2.4 Pyrolysis 13 2.2.5 Gasification reactions 13 2.2.6 Mechanism of solid-gas reaction and Thermodynamic background 14 2.2.7 Regimes of gas-Solid Reactions 17 2.2.8 Summary 19 2.3 Effect of Pressure on gasification process 20 2.3.1 Advantages of high-pressure operation 20 2.3.2 Influence on the pyrolysis step 20 2.3.3 Effect of Pressure on coal swelling 21 2.3.4 Pressure influence on char morphology 23 2.3.5 Effect of pyrolysis pressure on char surface area 23 2.3.6 Effect on reaction order n 24 2.3.7 Summary 24 2.4 Pressure influence on char gasification reaction kinetics 24 2.4.1 Pressure influence on gasification reaction kinetics 25 2.4.2 Summary 27 2.5 Char gasification using gasifying agent mixtures 27 2.5.1 Mechanism 29 2.5.2 The role of the inhibition and the catalytic effect 29 2.5.3 Summary 32 2.6 Thermodynamic aspects and the estimation of the reaction rate 32 2.6.1 Background 32 2.6.2 Basic definitions of reaction rate 34 2.6.3 Intrinsic kinetic models 35 2.6.4 Theoretical models 36 2.6.5 Empiric Models 39 2.6.6 Intrinsic kinetic models expressed by CO2 concentration 40 2.6.7 Arrhenius Activation Energy 40 2.6.8 Differentiation of a polynomial fit data (Differential method): 41 2.6.9 Summary 43 3. Experimental Analysis 44 3.1 Thermogravimetry 44 3.2 Testing of the gas volume fraction and the total pressure influence on char gasification 45 3.2.1 Testing of the gas volume fraction influence 45 3.2.2 Testing of system pressure influence on char gasification 56 3.2.3 Discussion 65 3.3 Coal gasification at 40 bar with pure CO2, H2O and their mixtures 65 3.3.1 Gasification with pure CO2 and H2O 66 3.3.2 Coal gasification using CO2 / H2O mixtures at high system pressure 87 3.3.3 Discussion 96 3.4 Pressure influence on coal gasification 100 3.4.1 Coal gasification under different system pressures 100 3.4.2 The effect of increasing pressure on coal morphology 104 3.4.3 Discussion 117 3.5 Influence of the pressure on the char properties during gasification 118 3.5.1 Discussion 129 4. General discussion 134 5. Conclusions 139 5.1 Significance of the findings 143 5.2 Recommendations 144 6. Appendix 146 6.1 Literature and Results 146 6.1.1 Conditions influence on gasification of the (a) temperature, (b) partial pressure 146 6.1.2 TGA-DMT 147 6.1.3 Testing of the gas volume fraction influence on coal gasification 148 6.1.4 Testing of system pressure influence on char gasification 150 6.1.5 Coal gasification at 40 bar with pure CO2, H2O and their mixtures 152 6.1.6 Coal gasification under different pressures 162 6.1.7 Summary of gas mixture gasification studies 167 6.2 Figures Index 169 6.3 Tables Index 175 6.4 References 177

This thesis focuses on the synthesis and characterisation of organoclays. X-ray diffraction has been used to study the changes in the basal spacings of montmorillonite clay and surfactant-intercalated organoclays. Variation in the d-spacing was found to be a step function of the surfactant concentration. Three different molecular environments for surfactant octadecyltrimethylammonium bromide (ODTMA) within the surface-modified montmorillonite are proposed upon the basis of their different decomposition temperatures. High-resolution thermogravimetric analysis (HRTG) shows that the thermal decomposition of montmorillonite modified with ODTMA takes place in four steps attributing to dehydration of adsorbed water, dehydration of water hydrating metal cations, loss of surfactant and the loss of OH units respectively. In addition, it has shown that the decomposition procedure of DODMA and TOMA modified clays are very different from that of ODTMA modified ones. The surfactant decomposition takes place in several steps in the DODMA and TOMA modified clays while for ODTMA modified clays, it shows only one step for the decomposition of surfactant. Also TG was proved to be a useful tool to estimate the amount of surfactant within the organoclays. A model is proposed in which, up to 0.4 CEC, a surfactant monolayer is formed between the montmorillonite clay layers; up to 0.8 CEC, a lateral-bilayer arrangement is formed; and above 1.5 CEC, a pseudotrimolecular layer is formed, with excess surfactant adsorbed on the clay surface. While for dimethyldioctadecylammonium bromide (DODMA) and trioctadecylmethylammonium bromide (TOMA) modified clays, since the larger sizes of the surfactants, some layers of montmorillonite are kept unaltered because of steric effects. The configurations of surfactant within these organoclays usually take paraffin type layers. Thermal analysis also provides an indication of the thermal stability of the organoclay as shown by different starting decomposition temperatures. FTIR was used as a guide to determine the phase state of the organoclay interlayers as determined from the CH asymmetric stretching vibration of the surfactants to provide more information on surfactant configurations. It was used to study the changes in the spectra of the surfactant ODTMA upon intercalation into a sodium montmorillonite. Surfaces of montmorillonites were modified using ultrasonic and hydrothermal methods through the intercalation and adsorption of the cationic surfactant ODTMA. Changes in the surfaces and structure were characterized using electron microscopy. The ultrasonic preparation method results in a higher surfactant concentration within the montmorillonite interlayer when compared with that from the hydrothermal method. Both XRD patterns and TEM images demonstrate that SWy-2-Namontmorillonite contains superlayers. TEM images of organoclays prepared at high surfactant concentrations show alternate basal spacings between neighboring layers. SEM images show that modification with surfactant will reduce the clay particle aggregation. Organoclays prepared at low surfactant concentration display curved flakes, whereas they become flat with increasing intercalated surfactant. Fundamentally this thesis has increased the knowledge base of the structural and morphological properties of organo-montmorillonite clays. The configurations of surfactant in the organoclays have been further investigated and three different molecular environments for surfactant ODTMA within the surface-modified montmorillonite are proposed upon the basis of their different decomposition temperatures. Changes in the spectra of the surfactant upon intercalation into clay have been investigated in details. Novel surfactant-modified montmorillonite results in the formation of new nanophases with the potential for the removal of organic contaminants from aqueous media and for the removal of hydrocarbon spills on roads.

New complex silicon-containing molecules were made by B(C6F5)3-catalyzed hydrosilation, dehydrocoupling, and dealkylative coupling reactions starting from Si-H reagents. The scope of reactions starting from disilane was expanded to include the formation of silicon-sulfur1, silicon-oxygen and silicon-alkyl side-chains. Reaction inhibition was found with some heteroatom substrates, such as phenols and imines, that strongly bound to B(C6F5)3, and was consistent with the proposed mechanism (Chapter 2). B(C6F5)3 was found to be selective for Si-H activation in reactions of disilane and no competing Si-Si bond cleavage side-reactions were observed. This result will guide future studies and application of B(C6F5)3-catalyzed reactions with polysilanes. A different type of selectivity, the competing B(C6F5)3-catalyzed over-reduction, is evaluated and discussed in Chapter 3. This over-reduction reaction was classified into two distinct cases: alkyl groups for which over-reduction reaction was dependent on the steric bulk of the alkyl group and benzylic groups for which over-reduction was dependent on having an alpha-aryl group. These reactions are consistent with the proposed Piers-Oestreich mechanism (see Chapter 3) and suggest the rate-determining step for over-reduction is the nucleophilic attack of the alkoxysilane (R -O-SiR3) to the R3Si•••H•••B(C6F5)3 complex. Benzylic side-chains were over-reduced regardless of the steric bulk of the aryl groups. Literature precedents suggest that benzyl over-reductions must undergo an alternative mechanism to the Piers-Oestreich mechanism. A number of mechanisms have been proposed in the literature and in Chapter 3, suggesting conventional heteroatom substrate borane or silane-borane complexation. Furthermore, over-reduction of benzylic sulfur containing side-chains was found and this reaction was exploited in the B(C6F5)3-catalyzed synthesis of unique silicon-sulfur silicon-containing products. These over-reduction reactions highlighted the role of the silane for over-reduction and the challenges associated with the post-polymerization modification of poly(phenylsilane). The advances in B(C6F5)3-catalyzed synthesis of small silane molecules suggested reaction conditions and gave spectroscopic benchmarks that were applied to the post polymerization modification of poly(phenylsilane) (Chapter 4). New X-modified poly(phenylsilane) derivatives with thiolato (sulfur), alkoxy/aryloxy (oxygen), amido (nitrogen) and alkyl(carbon) side-chains were prepared with 10-40% incorporation of the ‘X’ group into poly(phenylsilane). These new polysilanes were characterized by the following methods: 1H/13C/29Si NMR, IR, MALS-GPC, EA, and UV-vis absorption spectroscopy. Together, these characterization methods showed that the polysilane had not undergone Si-Si cleavage and thus demonstrated the utility of B(C6F5)3 for the selective activation of Si-H bonds. Thermal decomposition of X-modified poly(phenylsilane) derivatives and parent poly(phenylsilane) showed interesting redistribution pathways (Chapter 5). The thermal decomposition products of poly(phenylsilane) were identified: volatile monosilanes, a structurally complex not-yet-identified phenylsilicon-containing material generated at 500 °C, and a mixture of silicon carbide (SiC) and elemental carbon generated at 800 °C. The B(C6F5)3-catalyzed post-polymerization method (Chapter 4) was evaluated based on the substitution percentage for X-functionalized poly(phenylsilane) derivatives. Reactions of highly electron-donating substrates gave a low amount of X incorporation (10%, e.g. aryloxy side-chains derived from phenol). Aryloxy groups were alternatively introduced via demethanative coupling, which gave a polymer with a greater substitution percentage (25%). The overall impact of the H-to-X substitution reactions was gauged by UV-vis absorption spectra and desirable UV absorption properties would require the modified poly(phenylsilane) to have a high degree of substitution. / Graduate / 2017-09-02

Le LiFePO4 est un matériau prometteur pour les cathodes des batteries au lithium. Il possède une bonne stabilité à haute température et les précurseurs utilisés pour la synthèse sont peu couteux. Malheureusement, sa faible conductivité nuit aux performances électrochimiques. Le fait de diminuer la taille des particules ou d’enrober les particules d’une couche de carbone permet d’augmenter la conductivité. Nous avons utilisé une nouvelle méthode appelée « synthèse par voie fondue » pour synthétiser le LiFePO4. Cette synthèse donne des gros cristaux et aucune impureté n’est détectée par analyse Rayon-X. En revanche, la synthèse de LiXFePO4 donne un mélange de LiFePO4 pur et d’impureté à base de lithium ou de fer selon l’excès de fer ou de lithium utilisé. La taille des particules de LiFePO4 est réduite à l’aide d’un broyeur planétaire et plusieurs paramètres de broyage sont étudiés. Une couche de carbone est ensuite déposée sur la surface des particules broyées par un traitement thermique sur le LiFePO4 avec du -lactose. L’influence de plusieurs paramètres comme la température du traitement thermique ou la durée du chauffage sont étudiés. Ces expériences sont réalisées avec un appareil d’analyse thermogravimétrique (ATG) qui donne la quantité de chaleur ainsi que la variation de masse durant le chauffage de l’échantillon. Ce nouveau chauffage pour la couche de carbone donne des échantillons dont les performances électrochimiques sont similaires à celles obtenues précédemment avec la méthode de chauffage pour la couche de carbone utilisant le four tubulaire. / LiFePO4 is a promising cathode material for Lithium-ion batteries. It provides high thermal stability and is synthesized using low cost materials. Unfortunately LiFePO4 suffers from a low electrical conductivity, which is harmful to its electrochemical performance. Decreasing the particle size or coating the particles with carbon increases the conductivity of the material. We have used a new synthetic method called molten synthesis to synthesize LiFePO4. The molten synthesis produces large crystals of LiFePO4 with no impurity detected via X-ray diffraction analysis. Moreover, the synthesis of LiXFePO4 gives a mixture of pure LiFePO4 and Li-based impurities or LiFePO4 and Fe-based impurities whenever there is an excess of lithium or iron used. The particle size of the synthesized material is reduced via a Planetary Mill and numerous milling parameters were investigated. A carbon coating was then deposited on the surface of the milled material by thermally treating LiFePO4 with β-lactose. The influences of several parameters such as heat treatment temperature and/or heating duration were studied. These experiments were performed using a thermogravimetric analysis (TGA), which provides the amount of heat and weight change during the heating of the sample. This new heating method for carbon coating gave rise to samples with similar electrochemical performance data as to the previously established heating method involving a tubular furnace.

This project considers the co-rotating twin screw extrusion of a confectionery paste comprising powdered proteins, sugars, water and fats. As is the case with many food industry products, this process has been developed experimentally with little quantitative understanding of how variations in processing conditions influence the formation of the extrudate. A variety of techniques have therefore been developed to characterise and quantify the dispersive mixing, distributive mixing and rheological flow properties of this complex, multiphase, viscoelastic, unstable material. These techniques have then been utilised in a pilot plant extruder study of the mechanics of mixing and paste formation during extrusion, considering the influence of both processing conditions and screw profile. The internal evolution of paste microstructure has been successfully tracked along the length of screw profile using dead-stop extractions of the screws. A rigorous off-line assessment of shear yield strength behaviour using cone penetrometry has shown the use of conventional off-line rheometers to be unviable due to rapid post extrusion hardening. This highlighted the need for an in-line rheological measurement technique for continuous extrusion analysis where the extruded material is severely time dependent and not extractable. In pursuit of this, a novel arrangement of bender elements is proposed and trialled, to rapidly characterise material parameters of viscoelastic pastes. A second technique looking to extend the application of shear wave interface reflection to multiphase pastes is also trialled. A novel analysis of thermogravimetric data (TGA) has generated a viable index of distributive mixing, suitable for use on complex multi-component materials where thermal decomposition temperatures of the components are not well defined. Quantitative image analysis of pastes using scanning electron microscopy (SEM), optical microscopy protein staining and a novel application of multiphoton microscopy (MPM) have been used to visualise paste microstructure and quantify dispersive mixing. From the pilot plant extruder study, the application of these techniques was successful in mapping the evolution of paste mixing and the resulting microstructure, as well as identifying key differences between pastes mixed by twin screw extrusion and batch mixing.

Les gaines de zircaloy-4, assurent la première barrière de confinement des combustibles des Réacteurs à Eau Pressurisée. Plusieurs situations accidentelles au cours desquelles les gaines de crayons combustibles sont exposées l’air à haute température ont été envisagées. L’azote généralement utilisé en tant que gaz inerte, joue un rôle primordial lorsqu’il est combiné à l’oxygène à haute température. Les courbes cinétiques obtenues par la technique de thermogravimétrie révèlent la présence de deux domaines cinétiques : le domaine pré-transitoire et le domaine post-transitoire. Durant le domaine post-transitoire, la vitesse de corrosion augmente. Les images obtenues en microscopie optique révèlent l’existence de régions corrodées caractérisées par une couche de zircone poreuse et par la présence de précipités de nitrure de zirconium (ZrN) à l’interface métal - oxyde. La corrosion des plaquettes de Zy4 à 850°C sous mélanges oxygène - azote a été étudiée durant le domaine post-transitoire. Trois réactions successives permettent d’expliquer la présence des différentes phases. Ainsi, la dégradation catastrophique du métal est due à la progression auto-catalysée par ZrN du front de croissance des zones attaquées.Les hypothèses de modélisation ont été validées durant le domaine post-transitoire. L’étape déterminante a été identifiée. La réaction d’interface externe du mécanisme d’oxydation des précipités de ZrN impose sa vitesse aux autres étapes du mécanisme de croissance des régions corrodées. Par analogie avec les modèles de germination - croissance utilisés dans le cadre de la transformation thermique des poudres, nous avons pu décrire l’évolution des zones attaquées. / Zircaloy-4 claddings provide the first containment of UO2 fuel in Pressurised Water Reactors. It has been demonstrated that the fuel assemblies cladding could be exposed to air at high temperature in several accidental situations. When mixed to oxygen at high temperature, the nitrogen, usually used as an inert gas, causes the accelerated corrosion of the cladding.The kinetic curves obtained by thermogravimetry reveal two stages: a pre-transition and a post-transition one. In the post-transition stage, the kinetic rate increases with time. Images obtained by optical microscopy of a sample in the post-transition stage reveal the presence of corroded zones characterized by a porous scale with zirconium nitride precipitates at metal - oxide interface. Corrosion of Zy4 plates at 850°C under mixed oxygen - nitrogen atmospheres has been studied during the post-transition stage. A sequence of three reactions is proposed to explain the mechanism of nitrogen-enhanced corrosion. The accelerating effect of nitrogen in the corrosion scale can therefore be described on the basis of an autocatalytic effect of the zirconium nitride precipitates. Then, it is demonstrated that the steady-state approximation as well as the existence of an elementary step controlling the growth process are valid during the post-transition stage. The rate-determining step is identified as the external interface reaction step of the oxidation of the zirconium nitride precipitates. Finally, a nucleation and growth model used for thermal reactions in powders is used to describe both the nucleation and the growth of the attacked regions.

For the automotive sector, plastics play the most important role when designing interior and exterior parts for cars. Currently, most parts are made from petroleum-based plastics but alternatives are needed to replace environmentally harmful materials while providing the appropriate mechanical performance and preferably reduce the cost for the final product. The objective of this work was to explore the use of soy flakes as natural filler in a composite with polypropylene and to investigate the mechanical properties, water absorption and thermal behaviour. For a better understanding of the filler, the soy flakes were characterized extensively with analytical and microscopic methods. Two types of soy fillers were investigated, soy flakes, provided by Bunge Inc., with a 48 wt-% protein content and an industrial soy based filler with 44 wt-% protein content and provided by Ford. The size of the soy flakes after milling was mainly between 50 and 200 µm and below 50 µm for the industrial filler. The aspect ratio for all filler was below 5. The soy flakes were used after milling and subjected to two pre-treatment methods: (1) one hour in a 50 °C pH 9 water solution in a 1 : 9 solid-liquid ratio; (2) one hour in a 50 °C pH 9 1M NaCl solution in a 1 : 9 solid-liquid ratio. A control filler, without pre-treatment was considered. The soy flakes were also compared to an industrial soy based filler provided by Ford (soy flour (Ford)). The thermogravimetric analysis showed an onset of degradation at 170 °C for the treated filler (ISH2O and ISNaCl) and 160 °C for the untreated filler. The biocomposites formulation consisted of 30 wt-% filler, and polypropylene with/without 0.35 wt-% anti-oxidant Irganox 1010 and with/without the addition of MA-PP as coupling agent. All biocomposites were compounded in a mini-extruder, pressed into bars by injection moulding and tested subsequently. The mechanical properties of the biocomposites are promising. An increase of the E-modulus was observed when compared to pure polypropylene. The addition of MA-PP as coupling agent increased the yield strength of the biocomposites. When pure polypropylene and the biocomposites were compared no difference could be seen for their yield strength. The thermal behaviour deduced from differential scanning calorimetry, revealed a similar behaviour for the biocomposites and the pure polypropylene. Only the samples treated in the presence of NaCl and without a coupling agent, appear to have a slightly higher degree of crystallinity. The melt flow index was slightly increased for the biocomposites containing soy flakes pre-treated with NaCl and decreased for biocomposites containing the soy flour. The water absorption behaviour of the biocomposites was quite similar at the beginning with a slightly lower absorption for the materials with coupling agent. After three months, all samples except the ones treated with water showed a weight loss that can be due to the leaching of the water soluble components in the untreated filler and the NaCl treated filler. In conclusion, soy flakes represent an attractive filler when used in a polypropylene matrix if an aqueous alkaline pre-treatment is performed. The aqueous alkaline extraction also leads to the recovery of the proteins that can be used in food products while the remaining insoluble material is used for the biocomposites, avoiding the competition with the use of soy for food products...

For the automotive sector, plastics play the most important role when designing interior and exterior parts for cars. Currently, most parts are made from petroleum-based plastics but alternatives are needed to replace environmentally harmful materials while providing the appropriate mechanical performance and preferably reduce the cost for the final product. The objective of this work was to explore the use of soy flakes as natural filler in a composite with polypropylene and to investigate the mechanical properties, water absorption and thermal behaviour. For a better understanding of the filler, the soy flakes were characterized extensively with analytical and microscopic methods. Two types of soy fillers were investigated, soy flakes, provided by Bunge Inc., with a 48 wt-% protein content and an industrial soy based filler with 44 wt-% protein content and provided by Ford. The size of the soy flakes after milling was mainly between 50 and 200 µm and below 50 µm for the industrial filler. The aspect ratio for all filler was below 5. The soy flakes were used after milling and subjected to two pre-treatment methods: (1) one hour in a 50 °C pH 9 water solution in a 1 : 9 solid-liquid ratio; (2) one hour in a 50 °C pH 9 1M NaCl solution in a 1 : 9 solid-liquid ratio. A control filler, without pre-treatment was considered. The soy flakes were also compared to an industrial soy based filler provided by Ford (soy flour (Ford)). The thermogravimetric analysis showed an onset of degradation at 170 °C for the treated filler (ISH2O and ISNaCl) and 160 °C for the untreated filler. The biocomposites formulation consisted of 30 wt-% filler, and polypropylene with/without 0.35 wt-% anti-oxidant Irganox 1010 and with/without the addition of MA-PP as coupling agent. All biocomposites were compounded in a mini-extruder, pressed into bars by injection moulding and tested subsequently. The mechanical properties of the biocomposites are promising. An increase of the E-modulus was observed when compared to pure polypropylene. The addition of MA-PP as coupling agent increased the yield strength of the biocomposites. When pure polypropylene and the biocomposites were compared no difference could be seen for their yield strength. The thermal behaviour deduced from differential scanning calorimetry, revealed a similar behaviour for the biocomposites and the pure polypropylene. Only the samples treated in the presence of NaCl and without a coupling agent, appear to have a slightly higher degree of crystallinity. The melt flow index was slightly increased for the biocomposites containing soy flakes pre-treated with NaCl and decreased for biocomposites containing the soy flour. The water absorption behaviour of the biocomposites was quite similar at the beginning with a slightly lower absorption for the materials with coupling agent. After three months, all samples except the ones treated with water showed a weight loss that can be due to the leaching of the water soluble components in the untreated filler and the NaCl treated filler. In conclusion, soy flakes represent an attractive filler when used in a polypropylene matrix if an aqueous alkaline pre-treatment is performed. The aqueous alkaline extraction also leads to the recovery of the proteins that can be used in food products while the remaining insoluble material is used for the biocomposites, avoiding the competition with the use of soy for food products...

Thermo-stabilized lignin fibers from pH-fractionated softwood kraft lignin were carbonized to various temperatures during thermomechanical analysis (TMA) under static and increasing load and different rates of heating. The aim was to optimize the carbonization process to obtain suitable carbon fiber material with good mechanical strength potential (high tensile strength and high E-modulus). The carbon fibers were therefore mainly evaluated of mechanical strength in Dia-Stron uniaxial tensile testing. In addition, chemical composition, in terms of functional groups, and elemental (atomic) composition was studied in Fourier transform infrared spectroscopy (FTIR) and in energy-dispersive X-ray spectroscopy (EDS), respectively. The structure of carbon fibers was imaged in scanning electron microscope (SEM) and light microscopy. Thermogravimetrical analysis was performed on thermo-stabilized lignin fibers to evaluate the loss of mass and to calculate the stress-changes and diameter-changes that occur during carbonization. The TMA-analysis of the deformation showed, for thermo-stabilized lignin fibers, a characteristic behavior of contraction during carbonization. Carbonization temperatures above 1000°C seemed most efficient in terms of E-modulus and tensile strength whereas rate of heating did not matter considerably. The E-modulus for the fibers was improved significantly by slowly increasing the load during the carbonization. The tensile strength remained however unchanged. The FTIR-analysis indicated that many functional groups, mainly oxygen containing, dissociate from the lignin polymers during carbonization. The EDS supported this by showing that the oxygen content decreased. Accordingly, the relative carbon content increased passively to around 90% at 1000°C. Aromatic structures in the carbon fibers are thought to contribute to the mechanical strength and are likely formed during the carbonization. However, the FTIR result showed no evident signs that aromatic structures had been formed, possible due to some difficulties with the KBr-method. In the SEM and light microscopy imaging one could observe that porous formations on the surface of the fibers increased as the temperature increased in the carbonization. These formations may have affected the mechanical strength of the carbon fibers, mainly tensile strength. The carbonization process was optimized in the sense that any heating rate can be used. No restriction in production speed exists. The carbonization should be run to at least 1000°C to achieve maximum mechanical strength, both in E-modulus and tensile strength. To improve the E-modulus further, a slowly increasing load can be applied to the lignin fibers during carbonization. The earlier the force is applied, to counteract the lignin fiber contraction that occurs (namely around 300°C), the better. However, in terms of mechanical performance, the lignin carbon fibers are still far from practical use in the industry.

科学研究費補助金 研究種目:基盤研究(A)(1) 課題番号:07555545 研究代表者:松田 仁樹 研究期間:1995-1996年度