L'objectif de cette thèse est la préparation d’aérogels biosourcés ayant des propriétés de super-isolation thermique. Pour cela, nous avons choisi de développer de nouveaux aérogels à base de nanofibres de cellulose (NFC). Les aérogels ont été préparés par lyophilisation. Dans un premier temps, une analyse des paramètres expérimentaux jouant un rôle sur la morphologie et les propriétés physico-chimiques des aérogels a été réalisée afin d’obtenir les meilleures propriétés d’isolation thermique. Avec une suspension de NFC à 2% en masse, sans ajout de sels et sans faire varier le pH, une lyophilisation réalisée dans des moules d’aluminium à une température de -80°C a permis d’obtenir des aérogels ayant une conductivité thermique de 0,024 W/m.K. Afin de diminuer cette conductivité thermique, nous avons choisi de réduire la taille des pores pour obtenir un effet Knudsen. Pour cela, une nouvelle technique de séchage a été proposée : la lyophilisation par pulvérisation. Les aérogels préparés dans les mêmes conditions expérimentales que précédemment avec cette technique ont des propriétés thermiques super-isolantes (0,018 W/m.K) grâce à la nano-structuration du réseau poreux. Finalement, un nouveau dispositif expérimental a été développé pour caractériser plus finement les propriétés thermiques des aérogels. C’est un dispositif transitoire impulsionnel qui permet d'estimer simultanément la contribution de la conduction solide et gazeuse, l'effet radiatif et la diffusivité thermique grâce à un modèle théorique simple. Ce dispositif permettra d’approfondir l’étude complexe du transfert thermique à travers des matériaux poreux semi-transparents tels que les aérogels. / The objective of this thesis is the preparation of renewable aerogels having thermal super-insulating properties. To do it, we designed new aerogels from nanofibrillated cellulose (NFC) by freeze-drying. This technique is simple and has the advantage of not using organic solvents. First of all, the parameters playing a role on the aerogel morphology and physico-chemical properties of the aerogels were analyzed to get the best thermal insulating properties. Using 2 wt% NFC suspensions, without addition of salts, keeping the initial pH, the obtained freeze-dried aerogels in alumina molds at -80 °C have a thermal conductivity of 0.024 W/m.K. In order to reduce the pore size and to improve the thermal insulating properties by Knudsen effect, a new drying technique was proposed: the spray freeze-drying. Aerogels prepared in the same experimental conditions with this technique have thermal super-insulating properties (0.018 W/m.K) thanks to the nanostructuration of the porous network. Finally, a new device was designed to characterize more precisely the thermal properties of aerogels. This is an impulsive transient device, which can estimate simultaneously the contribution of solid and gas conduction, the radiative effect and thermal diffusivity using a simple theoretical model. This device will allow studying complex heat transfer through porous semi-transparent materials such as aerogels

This work deals with issues of elecroinsulating varnish and composite materials. The general aim is to observe impact of fulfilment and size of particle against measured values.

This graduation theses in introduction deals with principle and problems of electron signal detection in scanning electron microscopy and charging of insulating specimens in SEM. The experimental part of the thesis describe the methods of qualification and quantification of insulating specimen charging effect observed in environmental scanning electron microscope through the use of ionisation and scintillation detector in dependence on water vapour pressure in specimen chamber. The goal of the thesis is formation of the methodics useful to evaluate charging effect at insulating specimens observing and on the basis of measuring, determine optimal conditions for insulating specimen observation with ionisation and scintillation detector.

This work deals with issues of dielectric composite materials. The general aim is to observe how the amout of nanofilling influence dielectric spectrum in dependence on relative humidity and temperature which is measured on prepared samples. For this purpose had been created variety of a samples of electroinsulating varnish with different percentage of filling with nanoparticles. Experimental material is epoxy resin NH91 LV filled by Al2O3 nanoparticles.

This work deals with issues of composite materials. The general aim is to observe how the amout of filling infuence dielectric spectrum which is measured on prepared samples. For this purpose had been created variety of a samples with different percentage of filling with mica. Measured values had been compared with theoretically values, determinated using mixture formulas.

This thesis deals with improving thermal properties of contemporary ceramic fittings for external walls using built-in thermal insulation. In the practical part, PUR foam and PUR granulate waste mixes were designed. Based on insulation, mechanical and physical properties and estimated price, the best mix was chosen. Using the chosen mix as integrated isolation, the resulting ceramic block was simulated.

This thesis deals with alternative thermal degradation of electrical insulating liquids. The theoretical part describes the current state of the problem, electrical insulating liquids, their classification and types. There are described properties of electrical insulating liquids, their models of aging and diagnostic methods in accordance with the appropriate standards. In the practical part are chosen by representatives of alternative electrical insulating liquids and there are determined their dielectric characteristics in the initial state. According to the measured values is chosen five candidates for which it is designed and implemented an accelerated degradation test. During the test are measured dielectric parameters of the selected oils. Measured dependencies are mathematically approximated. In conclusion, the results are compared and physically interpreted in view of oxidation stability.

This master thesis deals with clasification of electrical insulating liquids and analysis their reological properties. Theoretical part describes viscosity and possibilities of its measurement, electrical and non-electricl properties of electrical insulating liquids and themselves electrical insulating liquids. Practical part describes measurement of viscosity and density of chosen vegetable oils, their components and transformer oils in wide temperature range. At the conclusion of the thesis, analysis of measurement results is done.

Dans ce travail de thèse, nous proposons dans une première partie l’usage de fibres de la plante marine Posidonia-Oceanica pour la fabrication de matériaux d’isolation thermique de bâtiments. Les caractérisations thermiques effectuées ont permis de mettre en évidence l’effet de la densité des fibres et de traitements chimiques. Il apparaît que ce type de fibres possède une conductivité équivalente à celle d’autres isolants courants et une capacité thermique massique plus élevée. La conductivité thermique en fonction de la masse volumique est comprise entre 0.04 et 0.07 W.m-1.K-1. La capacité thermique massique atteint environ 2500J.kg-1.K-1. Il apparaît également que l’influence du traitement chimique sur les propriétés thermiques n’est pas significative. Les résultats obtenus font de ces fibres un bon candidat pour une utilisation comme isolant thermique dans le domaine du bâtiment. Dans une seconde partie, ces fibres sont utilisées pour le renforcement d’une pâte de ciment. Une gamme de composites a été formulée pour des fractions volumiques en fibres allant de 0 à 20%. Une étude des propriétés hydriques de ces composites a été menée et complétée par des analyses par spectroscopie infrarouge à transformée de Fourier (FTIR) et des mesures des propriétés thermophysiques par la méthode du Hot-Disk durant le cycle de séchage. D’autre part, la quantification de la sensibilité de ces matériaux à l’humidité relative a été réalisée par la mesure de la variation de la teneur en eau dans les échantillons dans des environnements à humidité contrôlée. Ces mesures permettent de déterminer le coefficient de diffusion de l’eau. Celui-ci augmente légèrement avec l’augmentation du taux de fibres dans le composite. Du point de vue thermique, l’ajout de fibres améliore les propriétés isolantes des matériaux. En effet, une diminution de 22% sur la valeur de la conductivité thermique est notée avec l’introduction de 20% de fibres, par comparaison à l’échantillon de ciment témoin. L’influence sur la diffusivité thermique et sur la capacité thermique massique n’est pas significative. Du point de vue mécanique, la résistance à la traction par flexion et la compression augmentent légèrement jusqu’à 5 à 10% en volume de fibres puis diminuent. En revanche, une augmentation notable des valeurs de ténacité a été observée avec l’augmentation du dosage en fibres. Une augmentation de 65% est observée avec l’ajout de 20% de fibres. En s'appuyant sur les observations expérimentales, une modélisation analytique simplifiée a été réalisée. Celle-ci permet d'obtenir des modèles de prédiction des valeurs de la conductivité thermique, de la résistance à la traction par flexion, de la résistance à la compression et de la ténacité en fonction de la quantité de fibres dans le matériau / In this work, we have firstly studied the use of fibers extracted from the marine plant Posidonia-Oceanica as loose-fill thermal insulation material for buildings. Measurements were conducted and allowed the determination of the effect of fibers density and chemical treatments on thermal properties. Thermal conductivities were lying between 0.04 and 0.07 W.m-1.K-1, whereas the heat capacity is about 2500 J.kg-1.K-1. Thus, it was found that fibers thermal conductivity is close to the one of commonly used thermal insulation materials and that their heat capacity is significantly higher. It was also found that the influence of chemical treatment on the thermal properties is not significant. Measurement results showed that these fibers could be a promising ecological loose-fill insulation material in the construction field. Secondly, fibers were used as reinforcement for cement paste. A set of composite samples were formulated by varying fibers volume fractions from 0 to 20%. Their hygroscopic, thermal and mechanical properties were evaluated. Composites were analyzed by Fourier transform infrared spectroscopy (FTIR) and their thermophysical properties were measured with a Hot Disk thermal constants analyzer during the drying cycle. Sensitivity of these materials to relative humidity was examined by measuring the water content variation in controlled humidity environments. These measurements allowed the quantification of the water diffusion coefficient. This coefficient increased slightly with the increase of fibers content in composite samples. Concerning thermal properties, the addition of Posidonia-Oceanica fibers improved the material insulating properties. In fact, a decrease of about 22% on thermal conductivity values was found with the introduction of 20% of fibers compared to the unfilled cement paste. For Posidonia-Oceanica fibers volume fractions considered in this study (0 to 20 Vol.%), the effect of the presence of fibers on thermal diffusivity and on heat capacity is not significant, regarding the measurement uncertainties. Concerning mechanical properties, flexural and compressive strengths increased for about fiber volume fractions in the range of 5 to 10%. Moreover, a noticeable increase of toughness was observed with increasing fibers amount: for instance, an increase of about 65% was observed with the introduction of 20% of fibers in the composite. Based on the experimental observations, simplified analytical models were developed to predict thermal conductivity, flexural strength, compressive strength and toughness as a function of fibers volume fraction in the material

The subject of this diploma thesis is a proposal of a warehouse hall and an operation hall in Sokolnice. A land of the investor is located on Kobylnická street. Designed building is devided into two buildings which are a warehouse hall and an administrative building. The warehouse hall is designed as three-ship and has one floor above the ground. This building is designed for feed storage and breeding needs. The administrative building has got two floors above the ground. There is an office space for administrative company activity, facilities for employees and a company store. The support system of both buildings is made of steel structure, which is clad with insulating sandwich panels. A ceiling construction in the administrative building is also designed of steel support elements and trapezoidal sheet metal which is covered with a concrete layer. A roof construction of both buildings is flat, single skin and drained by means of a vacuum pipe. A roof composition consists of trapezoidal sheet metal, vapor barriers, dropped thermal insulator and from coating waterproofing. Internal layout is designed from plasterboard partitions. Thermal insulation in the plinth area at the warehouse is solved by using ETICS system. Foundation structures are designed as monolithic. Diploma thesis, according to the assignment, contain the creating of project documentation for the construction.