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Influence of cellulose ethers on rheological properties of lime
Hegrová, Michaela ; Rovnaník, Pavel (referee) ; Vyšvařil, Martin (advisor)
The subject of this diploma thesis is a study of the influence of cellulose ethers on the rheological properties of lime. The theoretical part focuses on rheological parameters, techniques and test equipment used in rheology measurements. Various types of cellulose ethers and their influence on the rheological properties of fresh mortars are described. The practical part deals with the study of the influence of different types and quantities of cellulose ethers on the properties of fresh lime pastes and mortars. The results were obtained from measurements on a rotational rheometer with a special geometry for building materials. Measuring methods used were flow and oscillatory tests. Yield stress, viscosity and flow index were determined by the flow measurement. The stability and stiffness of fresh materials were determined during the oscillation measurements. The measured results are then evaluated and compared.
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Empirical relationships for the assessment of the small punch test
Venský, Jiří ; Kubík, Petr (referee) ; Šebek, František (advisor)
This thesis aims at describing the small punch test, considering its limitations and its applications. Research of empirical equations, by which the value of yield stress and ultimate tensile stress is determined, was carried out. Furthermore, four calculation models were introduced. These models served to establish the yield stress of two materials using analytical solution based on Kirchhoff´s theory of plates. Calculated values of the yield stress were compared to the values obtained by the normalized tensile test. Calculated values were compared to the values of yield stress from the empirical equations found in literature as well. Yield stress values obtained by empirical relations were more accurate than those obtained from analytical solutions stated in this thesis.
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Estimation of mechanical properties of thin films using numerical modelling of experimental tests
Tinoco Navarro, Hector Andres ; Jančo,, Roland (referee) ; Klusák,, Jan (referee) ; Hutař, Pavel (advisor)
Testování tenkých filmů pomocí "Bulge testu" je experimentální technika která zahrnuje použití numerických a analytických přístupů k charakterizaci mechanických vlastností tenkých vrstev. Tato práce se zabývá některými omezeními nalezenými v klasických modelech, které popisují chování tenkých vrstev podrobených tomuto testu. Za tímto účelem byly vyvinuty nové modely a numerické strategie pro stanovení různých mechanických vlastností jednovrstvých a dvouvrstvých tenkých vrstev za odlišných strukturních podmínek, jako je elasticita, plasticita a lom. Kombinací metody konečných prvků a klasických analytických řešení byly navrženy a ověřeny různé metodiky pro výpočet elastických vlastností (E a v), zbytkových napětí, meze kluzu a lomové houževnatosti. Mechanické vlastnosti filmů z nitridu křemíku, hliníku a zlata byly charakterizovány pomocí experimentálních dat o zatížení-průhybu získaných z měření. Stanovené vlastnosti vykazovaly uspokojivou shodu s což potvrdilo, že metody navržené v této práci mohou být užitečné pro odhad mechanických vlastností se známými materiálovými vlastnostmi tenkých vrstev.
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Adhesive and rheological properties of chitosan-based mixtures in media of different pH
Omar, Alaa Abdel Gawad Ahmed Osman ; Šnejdrová, Eva (advisor) ; Mužíková, Jitka (referee)
Title of thesis: Adhesive and rheological properties of chitosan-based mixtures in media of different pH Author: Alaa Omar Supervisor: PharmDr. Eva Šnejdrová, Ph.D. Consultant: Mgr. Juraj Martiška The aim of the diploma thesis is the study of rheological and adhesive properties of tableting materials for matrix tablets based on chitosan. The theoretical part describes in detail the materials used to prepare the matrix tablets, which were chitosan, sodium alginate and hypromellose. The experimental section was focused on the flow and adhesive properties of the chitosan-based mixtures after exposing them to a media of different pH. The flow tests were done on an absolute rotational rheometer. Obtained viscosity curves were analysed by Power law model. Viscosity at 10 s-1 and Power Law model coefficients were used to evaluate and compare the flow behaviour of dispersions with different concentrations of retarding component in different media. The test of adhesion was carried out using a pull away test on a rotational rheometer and evaluated as maximal detachment force. The remarkably high viscosity of 5% dispersions at pH 1.2 is due to the dissolution of chitosan, as sodium alginate is not soluble in acidic media. The increase in viscosity with the concentration of the retarding component is insured...
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Oxygen-strengthened biomedical beta titanium alloys
Preisler, Dalibor ; Stráský, Josef (advisor)
Oxygen strengthened biomedical beta titanium alloys Beta titanium alloy Ti-35Nb-6Ta-7Zr-0.7O (wt. %) exhibits a low Young's modulus and high strength thanks to interstitial strengthening effect of oxygen. These mechanical properties are promising for implant production. In this thesis, the aforementioned alloy is thoroughly studied in conditions prepared by various thermomechanical treatments, namely: material after casting, hot compression testing, die-forging, hot rolling and finally, cold-swaged and annealed condition. Mechanical properties and microstructure of prepared conditions are studied with special interest of enhancing the fatigue performance that is poor after casting due to porosity and large grains. The hot rolling was shown to improve the fatigue performance significantly, mainly through grain refinement. It is shown that by combining the effects of cold-swaging and recrystallization annealing, extensive refinement of grain structure can be achieved. Industrial aspects of implant production by the studied methods were discussed. In the second part of the thesis, the possibility of lowering the Young's modulus by reducing the beta phase stability (by reducing of Nb and Ta content), while retaining high strength caused by high interstitial oxyen content is explored. Several alloys were...
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Oxygen-strengthened biomedical beta titanium alloys
Preisler, Dalibor ; Stráský, Josef (advisor)
Oxygen strengthened biomedical beta titanium alloys Beta titanium alloy Ti-35Nb-6Ta-7Zr-0.7O (wt. %) exhibits a low Young's modulus and high strength thanks to interstitial strengthening effect of oxygen. These mechanical properties are promising for implant production. In this thesis, the aforementioned alloy is thoroughly studied in conditions prepared by various thermomechanical treatments, namely: material after casting, hot compression testing, die-forging, hot rolling and finally, cold-swaged and annealed condition. Mechanical properties and microstructure of prepared conditions are studied with special interest of enhancing the fatigue performance that is poor after casting due to porosity and large grains. The hot rolling was shown to improve the fatigue performance significantly, mainly through grain refinement. It is shown that by combining the effects of cold-swaging and recrystallization annealing, extensive refinement of grain structure can be achieved. Industrial aspects of implant production by the studied methods were discussed. In the second part of the thesis, the possibility of lowering the Young's modulus by reducing the beta phase stability (by reducing of Nb and Ta content), while retaining high strength caused by high interstitial oxyen content is explored. Several alloys were...
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Adhesive and rheological properties of chitosan-based mixtures in media of different pH
Omar, Alaa Abdel Gawad Ahmed Osman ; Šnejdrová, Eva (advisor) ; Mužíková, Jitka (referee)
Title of thesis: Adhesive and rheological properties of chitosan-based mixtures in media of different pH Author: Alaa Omar Supervisor: PharmDr. Eva Šnejdrová, Ph.D. Consultant: Mgr. Juraj Martiška The aim of the diploma thesis is the study of rheological and adhesive properties of tableting materials for matrix tablets based on chitosan. The theoretical part describes in detail the materials used to prepare the matrix tablets, which were chitosan, sodium alginate and hypromellose. The experimental section was focused on the flow and adhesive properties of the chitosan-based mixtures after exposing them to a media of different pH. The flow tests were done on an absolute rotational rheometer. Obtained viscosity curves were analysed by Power law model. Viscosity at 10 s-1 and Power Law model coefficients were used to evaluate and compare the flow behaviour of dispersions with different concentrations of retarding component in different media. The test of adhesion was carried out using a pull away test on a rotational rheometer and evaluated as maximal detachment force. The remarkably high viscosity of 5% dispersions at pH 1.2 is due to the dissolution of chitosan, as sodium alginate is not soluble in acidic media. The increase in viscosity with the concentration of the retarding component is insured...
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Influence of particle size of cosmetic pigments on final properties product
Obručová, Kateřina ; Hurčíková, Andrea (referee) ; Zemanová, Jana (advisor)
This diploma thesis is focused on the study of the influence of the of size cosmetics pigments on the properties of the final product. This effect was studied on samples of make-up given by industry partner. Make-up samples were measured by the rheology method and the yield stress of all samples was determined. Scanning electron microscopy was used to determine the size and shape of the pigment particles. Particle size was also measured by dynamic light scattering, but the results were influenced by forming aggregates. To easier determination of the types of pigments in the sample was determined elemental composition of the pigments (Ti, Fe, O, Al) by EDS detector. Due to the unknown composition of make-up, the information was supplemented by X-ray powder diffraction (XRD) analysis, and it was possible to determine the compounds TiO2 (anatase and rutile), FeOOH and Fe2O3. The results obtained by these methods showed what pigments can be found in make-up samples, what their sizes and shapes are. It has been shown that the smaller the pigments are, the higher the viscosity and yield stress of the final product. The higher these quantities, the harder it is to handle the product.
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Empirical relationships for the assessment of the small punch test
Venský, Jiří ; Kubík, Petr (referee) ; Šebek, František (advisor)
This thesis aims at describing the small punch test, considering its limitations and its applications. Research of empirical equations, by which the value of yield stress and ultimate tensile stress is determined, was carried out. Furthermore, four calculation models were introduced. These models served to establish the yield stress of two materials using analytical solution based on Kirchhoff´s theory of plates. Calculated values of the yield stress were compared to the values obtained by the normalized tensile test. Calculated values were compared to the values of yield stress from the empirical equations found in literature as well. Yield stress values obtained by empirical relations were more accurate than those obtained from analytical solutions stated in this thesis.
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Effect of aggregate type on lime mortar rheology
Vozák, Rastislav ; Rovnaník, Pavel (referee) ; Vyšvařil, Martin (advisor)
The subject of this bachelor thesis is examining the effect of aggregate type on lime mortar rheology. In the theoretical part, the thesis describes types of liquids and basic rheological quantities. Afterwards there are described some of the rheological behaviour models of non-Newtonian fluids. Furthermore, the theoretical part characterizes measurement of the flow, devices used for the measurement including the oscillatory measurement and its individual modes. Scientific literature was used to describe the rheology of the lime mortars and it covers the effect of different additives on the rheological behaviour. There is also characterized the effect of aggregate on the properties of lime mortars. The experimental part talks about the effect of three various kinds of aggregate on rheological prop-erties of the fresh lime mortar. The chemical composition of aggregates and their granulometry was determined. Subsequently, flow measurements were carried out and evaluated into flow curves. The yield stress, coefficient of consistency and flow index were assayed. In the oscillatory measurement there were measured complex, elastic and viscous modulus and loss factor.
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