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Diagnostics of Diaphragm Discharge in Water Solutions and its Application for the Nanomaterials Surface Treatment
Dřímalková, Lucie ; Brablec, Antonín (referee) ; Janda,, Mário (referee) ; Krčma, František (advisor)
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.
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Health aspects of salt in food
Wűrzová, Anna ; Bušová, Milena (advisor) ; Králíková, Eva (referee)
Sodium chloride is an integral part of our nutrition and has an important function in the metabolism of the human organism. It contains sodium which is one of the basic minerals of the body. Although the salt is necessary for our body, its excess intake leads to a number of negative health effects. The theoretical part of the thesis describes the physiological importance of sodium chloride and the negative effect of salt on the body. It also deals with legislative requirements for salt, the recommended daily doses and trends in the consumption of salt. Last but not least, inform about therapeutic nutrition and the prevention of diseases associated with excess salt intake. The aim of the work is to make an overview of the importance and use of salts and the negative health effects of excess salt in human nutrition and further laboratory verification of the salt content in selected food and compared the measured results with the data on the salt content listed on the packaging. Part of the work is sample menus with different content of salt. The assembled full-day menus using the program Nutriservis represent, how to eat properly and to follow the health recommendations for salt intake according to the WHO and at the same time contain examples of bad menus with overdue daily amount of salt. For...
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Crystallization force of sodium chloride
Koudelková, Veronika ; Wolf, Benjamin
Soluble salts are one of the most deteriorating factor causing damage of historical building materials due to generation of crystallization pressure inside pore space. Direct measurement of crystallization force is quite challenging, hence we developed at our institute a novel device able to detect the force of growing crystal. The device is based on the monitoring of force developed with upper microscopic glass on the growing crystal to maintain constant position. The crystal could generate force because of the existence of thin liquid layer of solution between both surfaces come into contact. The driving force for the subsequent growth of crystal against obstacle is supersaturation, which is mainly induced by evaporation of the salt solution. In this experiment, the crystal of sodium chloride generated force 16.8 mN and the corresponding crystallization pressure was equal to the value 0.48 MPa.
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Knowledge of substitutes of salt in food
Vaňková, Marie ; Váchová, Alena (advisor) ; Hanušová, Jaroslava (referee)
The diploma thesis deals with the issue of salt and possibility of its replacement in food. The chosen is topical because healthy nutrition is one of current modern trends. Table salt is an entire part of a diet of every person. As the compound of two biogenic elements - sodium and chlorine - it has unsubstitutable function in human body. However, an increased intake of sodium can be associated with health risks, especially hypertension. The World Health Organization recommends a maximum daily intake of salt 5 g. According to current statistics, nevertheless the salt intake in the Czech republic is up to three times higher. Therefore, it is appropriate to reduce the consumption of salt and attempt to its replacement without cutting down the taste of food. One of the goals of this thesis was find out possibilities of replacing the salt and what is their availability. The practical part deals with the results of survey, within these was examined the awareness of salt and the posibility of its replacement among different group of our population (students, pedagogical workers, heads of school canteens). In terms of established facts there was suggested a project called The salt is beneficial and dangerous which aids to raise awareness of students about this topic. These outputs can be put into the...
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Use of energetic by-products and other secondary raw materials for the alpha gypsum production
Moldrzyk, Jan ; Jiroušková, Kateřina (referee) ; Dvořák, Karel (advisor)
Thesis focus on the longterm research in an area of alpha gypsum production by non pressure method in chloride salt solutions production, which is researched by Institute od technology of building materials and components, Faculty of civil engineering for many years. The result of given research is non pressure equipment for alpha gypsum production. The scope of this research was to make a production of alpha gypsum more efficient through modification of the facility itself and through an optimalization of dehydration process. The scientific aim of this process was to compare an influence of dehydratation solutions of CaCl2, NaCl and KCl on the final product provided that molarity of solutions was at the same level.
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The development of composites based on inorganic binders designed for the extreme applications
Janoušek, Petr ; Šácha, Libor (referee) ; Dufka, Amos (advisor)
The topic of this master's thesis is the development of composite materials based on inorganic binders for use in extreme conditions. It means especially geopolymeric or alkali activated materials (AAM) based composites. The theoretical part of this thesis summarizes knowledges about the development and use of alkali-activated materials, their structure and mechanisms of their formation. It also deals with the applicable raw materials for AAM and their exciters, which are in particular water glass and sodium hydroxide. There also have been a summary of the effects of high temperatures and chemicals on the mechanical properties of AAM and the requirements of standard EN 1504-3 for repairing materials. The task of the practical part was to develop a repair mortar for concrete structures based on AAM so that its production was as simple as possible, ie one-component materials. Gradually six recipes have been develeoped. Test specimens made from these recipes have been putted to selected tests according to the requirements of ČSN EN 1504-3.
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Plasma diagnostics of electric discharges generated in selected configurations in liquids
Vašíček, Michal ; Bartlová, Milada (referee) ; Kozáková, Zdenka (advisor)
My diploma thesis is focused on a comparison of direct-current and high frequency (15-80 kHz) electric discharge, which generates non-thermal plasma in water solution of sodium chloride. Mainly current-voltage and Lissajous charts are discussed in the first part of this thesis. These charts describe different discharge phases: electrolysis, bubble formation, discharge breakdown and discharge regular operation in a pin-hole of a dielectric barrier. Influence of frequency, electrolyte conductivity, thickness of the diaphragm (or length of the capillary) and pin-hole diameter on discharge breakdown and bubble generation was studied, too. Measurements were realized in a polycarbonate reactor with total volume of 110 ml, which was divided by a changeable polyacetal insulating wall. This wall divided the reactor into two approximately equal spaces with one stainless steel planar electrode in each part. The Shapal-MTM ceramic discs (thickness of 0.3–1.5 mm and diameter of the central pin-hole of 0.3-0.9 mm) were mounted in the centre of the insulating wall. Initial conductivity of sodium chloride solution was chosen within the interval of 100900 S/cm. The second part of my thesis compares an influence of the direct-current (DC) and high frequency (HF) power sources on physical solution properties (conductivity, pH and temperature) and generation of hydrogen peroxide. A plasma reactor with total volume of 4 l and with mixing set up was divided into two equal spaces with one planar platinum electrode in each part. Diaphragm with thickness of 0.6 mm and pin-hole diameter of 0.6 mm was installed in the middle of the separating wall. Experiment was held at discharge operation of 45 W for 40 minutes with both power sources. Detection of hydrogen peroxide was realised by using a titanium reagent forming a yellow complex, which was analysed by absorption spectroscopy. If HF discharge power is plotted as a function of applied frequency, exponential decrease of frequency with increasing power can be observed. Higher breakdown voltage is necessary for thicker dielectric barriers, on the other hand for bigger diameter of the pin-hole lower breakdown voltage and higher power is needed in DC as well as in HF regime. Breakdown voltage is decreased by the increasing conductivity in both regimes; due to more charge carriers in the higher conductivity lower breakdown voltage is needed. However frequency in HF regime and DC discharge power increases. HF discharge power is decreased by the increasing conductivity. Solution conductivity and temperature are increased by initial conductivity value in both discharge regimes. Solution pH drops to acidic conditions when HF or DC positive regime is applied due to the generation of reactive species and electrolysis (in DC regime). However solution becomes alkaline when DC negative regime is applied. Concentration of hydrogen peroxide is produced linearly when HF or DC negative regime is applied and it depends on initial solution conductivity.
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Preparation of high performance sulphate binder by nonpressure method
Urban, Karel ; Novák, Jan (referee) ; Dvořák, Karel (advisor)
Institut of Technology building materials and components in FAST VUT Brno is for several years engageding by research of unpressurized production of high sulphate binders and also by developing a dehydrating apparatus. This work follows on this research. The main aim of this work is to prepare the alpha calcium sulfate hemihydrate by method of dehydration in the various solutions the chloride salts of the same molal concentration in an innovative dehydration apparatus. Another aim is monitoring the influence dehydrating solutions on the basis of KCl, NaCl and CaCl2 on the properities of made gypsum.
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