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The focus of this thesis has been to determine the usable voltage range of carbon-based supercapacitors (SC). Supercapacitors are a relatively new type of capacitors with a vast increase in capacitance compared to capacitors which utilize a dielectric as charge separator. A SC consists of two electrodes and an electrolyte separating the electrodes. The charges are stored by electrostatic forces in the interface between the electrode and the electrolyte, forming the so called electrochemical double-layer (EDL). With porous electrodes the effective surface area of the interfacial zone can be made very large, giving SCs a large storage capacity. The limiting factors of a SC is the decomposition potential of the electrolyte and the decomposition of the electrodes. For commercially manufactured SCs the electrolyte is usually an organic solvent, which has a decomposition potential of up to 2.7-2.8 V. Compared to aqueous electrolytes with a thermodynamic limit of 1.23 V. The drawback of using non-aqueous electrolytes is that they are not environmentally friendly, and they increase the production cost. It is claimed that the voltage range can be up to 1.9 V using aqueous electrolytes. Some researchers have focused on aqueous electrolytes for these reasons. In this thesis two different electrolytes were tested to determine if the voltage range could be extended. The experiments were conducted using a three electrode cell and performing cyclic voltammogram measurements (CV). The carbon electrodes were made of  two different sources of grahite, battery graphite or exfoliated graphite, and nano fibrilated cellulose was added to increase the mechanical stability. The results show that the oxidation potential of the carbon electrode was the positive limit. A usable potential of about 1 V was shown. However, when cycling the electrodes to potentials below the decomposition limit, for hydrogen evolution, interesting effects were seen. A decrease in reaction kinetics, indicating a type of conditioning of the electrode was observed. An increase in charge storage capacitance was also observed when comparing the initial measurements with the final, probably corresponding to an increase in porosity. / KEPS projekt Sundsvall Mitt Universitet

Les sulfates de sodium sont admis comme étant les sels les plus destructeurs pour les pierres naturelles et autre matériaux poreux. Les processus de cristallisation de ces sels demeurent encore mal compris, plus particulièrement les relations entre l'heptahydrate (SS7, Na2SO4-7H2O) et la mirabilite (SS10, Na2SO4-10H2O). L'heptahydrate, métastable, a longtemps été négligée dans les travaux scientifiques portant sur l'altération saline jusqu'à récemment, et son rôle dans l'altération des roches n'est toujours pas établi à ce jour. Afin de mieux comprendre le rôle des différentes phases dans l'altération, il est important de pouvoir identifier quelle phase cristallise sous des conditions environnementales spécifiques. La cristallisation du sel se produit le plus souvent dans les matériaux poreux où les processus de cristallisation ne peuvent pas être observés directement in situ. Dans cette étude, nous utilisons le suivi de la température pour détecter et identifier la cristallisation des hydrates au cours de cycles de refroidissement/chauffage d'une solution de sulfate de sodium et de l'échantillon de calcaire saturé de cette même solution. En parallèle, d'autres approches expérimentales consistent à mesurer la réponse électrique et élastique des processus de cristallisation / dissolution se produisant dans le milieu poreux. Ces méthodes permettent d'identifier les différentes transitions de phases se produisant au cours de cycles de température et peuvent être utilisées dans des études expérimentales de vieillissement accéléré, afin d'estimer le rôle respectif des différents hydrates de sulfate de sodium dans l'altération des pierres par les sels. / Sodium sulfates are well known to be the most damaging salts in building materials and rocks. The crystallization processes of sodium sulfates are not completely understood, and more specifically the transition between the heptahydrate (SS7, Na2SO4-7H2O) and the mirabilite (SS10, Na2SO4-10H2O). The metastable heptahydrate has long been neglected in scientific works on salt damage until recently, and its role in rock weathering has not been established so far. In order to better understand the role of the different phases in damaging process, it is important to be able to identify which phase crystallizes under specific environmental conditions. Unfortunately, salt crystallization occurs very often within porous material and crystallization processes cannot be observed directly in situ. In this study, we use temperature monitoring to detect and identify the hydrates crystallization during cooling/heating cycles a sodium sulfate solution and limestone samples saturated with the same solution. In parallel, other experimental approaches consist to measure the electrical and elastic responses of the crystallization/dissolution processes occurring in the porous media. These methods enable to characterize the different phases occurring during temperature cycle and can be used in further experimental studies about ageing test in order to estimate the role of the different sodium sulfate hydrates involved in the salt weathering of rocks.

Although the etiology and pathogenesis of inflammatory bowel disease (IBD) is not fully understood, it is generally accepted that the inflammation results from aberrant immune responses to antigens of gut microbiota in genetically susceptible individuals (Sartor et al., 2006). Alteration in intestinal microbiota has been found in IBD patients with increased abundance of certain bacteria and decreased abundance of others. Due to the complexity of the disease, multifaceted interactions between genetic factors, host immune response, gut microbiota and environment factors need to be taken into account. In this thesis, the pathogenesis of IBD was first reviewed in respect with the four factors mentioned above. Then we concentrated on the interaction between IBD-associated bacteria and mucosal immune system. We investigated the ability of mucosal-associated bacteria (MAB) from IBD patients to induce spontaneous colitis in germ-free (GF) mice and the impact of those bacteria on the development of dextran sulfate sodium (DSS)-colitis. Together with the analysis of the composition of gut microbiota of MAB colonized mice, we demonstrated the potential deleterious microbes were able to increase the susceptibility to DSS-colitis once they found a suitable niche. We revealed the mechanism of an E.coli strain...

The exact mechanism of the discharge in liquids ignition is not sufficiently known up to now. Although during the last years was achieved the great progress and overloading which some of them are written in this theoretical part of thesis. This thesis is divided into two experimental parts. When the first part deals with diagnostics of diaphragm discharge in electrolyte solutions and the second part is focused on its use for uncoiling (higher homogenization) of carbon nanotubes in solutions. In experiment 1, three different sized (4 l, 100 ml, 50 ml) diaphragm discharge configurations were used to diagnose diaphragm discharge in electrolyte solutions. Diagnostics is done through current and voltage waveforms with the addition of synchronized ICCD camera images that have been connected to a four-channel oscilloscope. The V-A characteristic can be described by three events occurring in the electrolyte solution with a gradual increase in voltage. Slowly increasing of the voltage in the solution leads first to electrolysis. The next phase is the formation of microbubbles or bubbles, which is characteristic of the curve by a slight decrease in the increase of the current passing between electrodes. The sudden increase in the current flow is characteristic of the last phase, namely the discharge phase. The distance of the electrodes from the diaphragm does not significantly affect the V-A characteristic. The higher diameter of the pin hole, therefore, has a higher voltage, but this does not affect the origin of bubble generation or breakdown. The higher thickness of diaphragm, the higher voltage is needed to the beginning of the bubbles generation, and consequently the discharge breakdown. Comparison of the voltage of the start generation of the bubbles and breakdown for PET diaphragms and diaphragms from the ceramic there was no mark able difference. One of the most important parameters is the conductivity of the electrolyte solution. The lower voltage is needed for the start generation of the bubbles at the higher solution conductivity, and also the discharge generation is observed at a lower breakdown voltage. The second experimental part is focused on the study of the diaphragm discharge effect on carbon nanotubes. A specially designed U-shaped reactor is used to modify carbon nanoparticles. Tap water and aqueous solutions of organic compounds are used as the electrolytic solutions. The discharge is generated by a non-pulsed DC high source with a voltage in the range of 0-2.8 kV supplied to platinum electrodes located in the electrolyte solution. The experimental results have shown that the diaphragm discharge has positive effects on the disintegration of clusters and agglomerates of carbon nanotubes. The primary effect on disintegration is probably the shock waves generated by the discharge. It turned out that it depends on the electrode configuration, where the treatment in anode space has far greater effects than the treatment in cathode half of the reactor. Effects of carbon nanotubes disintegration in solution are long-lasting and the treatment effect is not loosed after several months. There were detected no significant changes in the structure of plasma-treated nanotubes by Infra-red spectroscopy.