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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
181

Avaliação da resistência de união da interface cerâmica Y-TZP/dentina humana utilizando diferentes agentes de cimentação e tratamentos de superfície / Evaluation of bond strength of Y-TZP / dentin ceramic interface using different cementing agents and surface treatments

Isabela da Rocha Silva 25 November 2015 (has links)
Hipótese do estudo: A hipótese do presente estudo é de que o cimento resinoso autoadesivo U200 apresente melhores valores de resistência adesiva entre os substratos zircônia Y-TZP/dentina humana, em comparação com o cimento resinoso convencional C&B Cement, utilizando dois tratamentos de superfície distintos (jateamento com óxido de alumínio e silicatização (Rocatec) na superfície da zircônia; e que o tratamento de superfície influencie positivamente os resultados de resistência adesiva. Objetivos: Avaliar por meio de teste de microcisalhamento a resistência adesiva da zircônia Y-TZP cimentada à dentina humana utilizando diferentes agentes de cimentação e tratamentos de superfície. Método: Foram utilizados 42 molares humanos recém extraídos, incluídos 2/3 de suas raízes em resina acrílica. A superfície oclusal foi desgastada até exposição da dentina média, tratada de acordo com as recomendações dos fabricantes dos cimentos. Quarenta e dois blocos de zircônia Y-TZP (10x10x3mm) foram divididos aleatoriamente em três grupos de acordo com o tratamento de superfície (sem tratamento-controle, jateamento com óxido de alumínio-Al2O3 ou silicatização-Rocatec). Todos os blocos de zircônia foram cimentados seguindo as recomendações dos fabricantes e divididos em seis grupos combinando os diferentes tratamentos de superfície e agentes de cimentação. Os espécimes foram armazenados em água destilada 37C por 24h e após este período foram submetidos ao teste de microcisalhamento em máquina de ensaios universal (Shimadzu AGX) com velocidade constante de 0,5mm/min até ocorrer fratura da interface. Os valores foram obtidos em Mpa e as superfícies de fraturas avaliadas e classificadas em: adesiva, coesiva e mista. As médias dos valores de resistência de união e a porcentagem das fraturas foram calculadas, e os valores submetidos à análise estatística, utilizando os testes Análise de Variância (two way) e pos-hoc teste T de Student, adotando p<0,05. Resultados: Quanto ao agente de cimentação os resultados obtidos para os grupos sem tratamento de superfície o cimento autoadesivo U200 apresentou melhor performance quando comparado ao cimento convencional C&B Cement; os grupos submetidos ao jateamento com Al2O3 e Rocatec não apresentaram diferença estatística entre os cimentos U200 e C&B Cement. Quanto à analise de superfície, os grupos cimentados com C&B e U200 apresentaram predominantemente falhas de natureza mista. Conclusão: Com base nos resultados encontrados no presente estudo foi possível concluir que o tratamento de superfície que melhor influenciou a resistência adesiva foi o jateamento com Al2O3, atendendo melhor os dois agentes de cimentação. Quanto ao agente de cimentação o U200 apresentou os melhores resultados sem tratamento de superfície. O C&B Cement e U200 apresentaram valores semelhantes com a superfície jateada com Al2O3. Para o Rocatec, os cimentos U200 e C&B Cement apresentaram valores semelhantes, entretanto menores do que os valores conseguidos para o Al2O3. / Study hypothesis: The hypothesis of this study is that the resin cement Self Adhesive U200 present best values of bond strength between zirconia substrates Y-TZP / dentin compared to conventional resin cement C & B Cement, using two surface treatments distinct (sandblasting with aluminum and silica coating (Rocatec) oxide on the surface of zirconia, and the surface treatment positively influence the bond strength. Objectives: To assess via microshear test the bond strength of zirconia Y-TZP cemented to dentin human using different cementing agents and surface treatments. Method:. freshly extracted human molars 42, including two thirds of its roots in acrylic resin were used the occlusal surface was worn until the middle dentin exposure, treated according to the recommendations of the cement manufacturers. Forty-two blocks of Y-TZP zirconia (10x10x3mm) were randomly divided into three groups according to the surface treatment (untreated control, blasting with aluminum oxide or silica coating-Al2O3-Rocatec). All zirconia blocks were cemented following the manufacturers recommendations and divided into six groups combining different surface treatments and cementing agents. The specimens were stored in distilled water 37 C for 24 h and after this period underwent microshear test in a universal testing (Shimadzu AGX) machine with constant speed of 0.5 mm / min until fracture occurs interface. The values were obtained in MPa and the fracture surfaces evaluated and classified as: adhesive, cohesive and mixed. The average values of union strength and the percentage of fractures were calculated, and values subjected to statistical analysis using analysis of variance tests (two way) and post-hoc Students t test, considering p <0.05. Results: Regarding the cementing agent the results for the groups without surface treatment U200 self-adhesive cement showed better performance when compared to conventional cement C & B Cement; groups subjected to blasting with Al2O3 and Rocatec showed no statistical difference between the U200 and cements C & B Cement. As for the analysis of surface groups cemented with C & B and U200 were mostly mixed nature of failures. Conclusion: Based on results of this study it was concluded that the surface treatment that best influenced the bond strength was blasting with Al2O3 to better serve the two cementing agents. As the cementing agent U200 showed the best results without surface treatment. The C & B Cement and U200 showed similar values with the surface sandblasted with Al2O3. Rocatec to the U200 and cement Cement B & C showed similar, though lower than the values obtained for Al2O3 values.
182

Inlays/onlays usinés par CFAO : critères d’évaluation in vitro des assemblages collés, complémentarité des études expérimentales / CAD-CAM inlays/onlays restorations : in vitro evaluation criteria of bonding assemblies, complementarity of experimental studies

Goujat, Alexis 08 January 2019 (has links)
De nombreux paramètres interviennent dans la longévité des inlays/onlays réalisés par CFAO tels que l’usinabilité et les propriétés mécaniques des matériaux utilisés, l’adaptation de la restauration ainsi que la qualité de l’interface entre le matériau de restauration en céramique ou en composite et le matériau d’assemblage. Dans un premier temps, au travers d’une revue systématique de la littérature, nous avons sélectionné les méthodes expérimentales et les paramètres permettant d’évaluer l’adaptation de ces restaurations. Il existe des techniques en 2D qui mesurent l’espace dent-matériau à des points de référence présélectionnées et des techniques en 3D (Triple-scan, micro-CT) qui mesurent l'ensemble de l'interface. Cette revue de la littérature nous a permis de mettre en évidence que : le matériau de restauration, le type de préparation, le vieillissement, le collage ou non de la restauration et des paramètres propres à la CFAO ont une influence sur l’adaptation. Dans un deuxième temps, nous avons étudié les propriétés mécaniques de blocs en céramique et en composite et l’adaptation interne in vitro d’inlays usinés à partir de ces mêmes matériaux. L’influence de la nature du matériau de restauration et de son usinabilité sur l’adaptation a été mise en évidence. La troisième partie de notre travail a porté sur la qualité de cette interface par un test de résistance en microtraction et une analyse du type de fracture. Une relation étroite a été démontrée entre la microstructure du bloc testé et le type de traitement de surface utilisé. Ce travail a souligné l’importance d’utiliser plusieurs méthodologies et de les croiser entre elles afin de mieux corréler nos résultats. L’étude du vieillissement de ce joint dento-prothétique constitue un travail à part entière dans laquelle certaines méthodologies utilisées dans cette thèse (profils de rupture, essais mécaniques) peuvent être transposées / Several parameters are involved in the longevity of CAD-CAM inlays/onlays restorations such as the machinability and mechanical properties of the materials used, the adaptation of the restoration and the quality of the resin cement-ceramic or composite interface. Initially, through a systematic review of the literature, the experimental methodologies and parameters to evaluate the adaptation of these restorations were selected. The gap between the tooth and the material, at preselected reference points, is measured by 2D techniques. 3D techniques (Triple-scan, micro-CT) are able to measure the entire interface. This review of the literature allowed us to highlight that: the restorative material, the preparation design, aging, the use of a bonding-system and parameters regarding the CAD-CAM technology have an influence on the marginal adaptation. Afterwards, we assessed the mechanical properties of CAD-CAM ceramic and composite blocks and the internal adaptation in vitro of inlays milled with these same materials. The influence of the nature of the restorative material and its machinability on adaptation was put forward. The third part of our work focused on the quality of this interface using a microtensile bond strength test and a fracture type analysis. A tight association has been shown between the microstructure of the tested blocks and the type of surface treatment applied. This work underlined the importance of using several methodologies and crossing them to better correlate our results. Studying the aging of this dento-prosthetic joint constitutes a whole work in which some approaches used in this thesis (fracture profiles, mechanical tests) can be implemented and transposed
183

Study of particle-current-electrocrystallization interactions in electroplating of Ni/SiC coatings

Pinate, Santiago January 2019 (has links)
Composite coatings have great potential due to the possibility to combine properties of two different materials in one coating. This way, new surface properties can be tailored and applied to any material's surface. Among different manufacturing routes, electrodeposition has the biggest potential in creating composite metal matrix coatings, especially nanocomposites. Nevertheless, there is a knowledge gap between the deposition of composite coatings in laboratory conditions, described in the literature, and those that are now in place on an industrial level. While micro-composites have been industrialised for about ten years, the production of Ni/SiC nanocomposite coatings by electroplating is still far from an industrial manufacturing floor. This is due to the lack of understanding of the mechanisms of nanoparticles codeposition leading to scattering results. The production of nanocomposite coatings is much more sensitive to the process parameters compared to microcomposite. The correlation between parameters and their influence on the codeposition are still not fully identified and understood. The codeposition models proposed in the literature are only valid in specific conditions, but composite depositions behave differently, or even opposite if some of the variables are modified. The main objective of this work is to identify the particle-current-electrocrystallization interactions in the production of Ni/SiC nanocomposites. A series of experiments are designed to isolate single variables and identify the controlling parameters of these interactions and their impact on the final properties. In this thesis, the effect of current density, type of current and particles size are identified as primary variables controlling the metal crystallisation and coatings properties. Among many parameters, a specific current waveform in pulse reverse mode proved to increase the codeposition rate effectively, doubling the content of nanoparticles compared to other techniques. Ultrasound assistance is also considered as stirring method when particles are suspended in the deposition bath to increase their stability and dispersion. The effect of Ultrasound on the particles codeposition and metal crystallisation is studied and compared to silent condition. Moreover, a surface treatment for the particle has been proven successful in making any particle to behave similarly in the Ni deposition bath. Furthermore, the codeposition rate doubled or tripled compared to untreated ones thanks to this treatment. Both ultrasonic agitation and surface treatment reduce the formation of aggregates, improving the particle dispersion and metal microstructure thus increasing the final hardness. The work proved the synergistic effect between particle and metal microstructure which affected the final properties of the coating. Therefore, when tailoring the composite coating to improve hardness, it is not only the amount of the particles that should be considered but also their influence on the electrocrystallisation process. / Kompositbeläggning har stort potential tack vare möjligheten att kombinera två material i samma ytskikt. På detta sätt kan nya ytegenskaper skräddarsys och appliceras på ett materials yta. Elektrodeposition är den tillverkningsmetod som har störst potential att uppnå kompositbeläggningar, i synnerhet nanokompositer. Ett kunskapsgap existerar mellan elektrodeposition under laboratorieförhållanden, som beskrivet i vetenskaplig litteratur, och hur processen går till i industriell miljö. Medan industriell tillämpning av mikrokompositer pågått ungefär tio år, så har produktion av Ni/SiC nanokompositbeläggningar fortfarande inte nått fabriksgolvet. Detta är en konsekvens av bristande förståelse kring mekanismer för samdeposition av nanopartiklar som leder till varierande resultat. Produktion av nanokompositbeläggningar är mycket mer känslig för processparametrar jämfört med mikrokompositer. Korrelationer mellan parametrar och dess inverkan på samdeposition är fortfarande inte fullt identifierade och förstådda. Modeller för samdeposition som föreslås i vetenskaplig litteratur är endast giltiga under särskilda förhållanden. Kompositdeposition kan uppvisa avvikande eller till och med motsatt beteende om variabler förändras. Huvudmålet med detta arbete är att identifiera interaktioner mellan partikel, ström och elektrokristallisering under tillverkning av Ni/SiC nanokompositer. En serie av experiment är utvecklade för att isolera variabler och identifiera de parametrarna som kontrollerar dessa interaktioner och dess inverkan på ytans egenskaper. I denna avhandling identifieras strömtäthet, typ av ström, och partiklars storlek som primära variabler som kontrollerar metallkristallisering och beläggningens egenskaper. Bland många parametrar, visades en specifik vågform på strömmen i omvänd pulsläge öka samdepositionen effektivt, ledande till en fördubbling av andelen nanopartiklar jämfört med andra tekniker. Ultraljud tillämpades som metod för omrörning av depositionsbadet för förbättrad stabilitet och fördelning. Effekten av ultraljud på samdepositionen av metallkristallisering studeras och jämfört med tyst tillstånd. Dessutom har en ytbehandling för partiklarna visats framgångsrik för att få godtyckliga partiklar att bete sig likt Ni i depositionsbadet. Detta ledde till att samdepositionens takt ökade med en faktor av två till tre jämfört med obehandlade partiklar. Både ultraljud och ytbehandling av partiklarna ledde till minskad aggregation vilket förbättrade fördelningen av partiklar och metallstruktur och därigenom ökad hårdhet. Arbetet bevisar synergieffekten mellan partiklar och metallstruktur vilket påverkar beläggningens slutliga egenskaper. Vid utveckling av nya ytbeläggningar ska därför inte bara mängden partiklar beaktas utan även dess interaktion med elektrokristalliseringsprocessen.
184

Podnikatelský záměr – rozšíření výrobních kapacit společnosti Industrial Engineering s. r. o. / Business Plan – Expansion of Production Capacities of Industrial Engineering s.r.o.

Valová, Zuzana January 2017 (has links)
The subject of this thesis is to assemble a business plan for expansion of production capacities of Industrial Engineering company s.r.o. by acquisition of new technologies. The theoretical part describes the importance of the business plan, the importance of business and basic legal forms of business. The part of it is also a description of the stucture and assembly of the business plan. In the practical parts there is an analysis of the current situation and marketing analysis, alon with the processing of the business plan assessed the feasibility of the project with a positive result.
185

Modifikace povrchu kovových materiálů s využitím elektronového svazku / Surface Treatment Technology of Metallic Materials and its Applications using Electron Beam

Matlák, Jiří January 2019 (has links)
Fast deflection is one of the great advantages of an electron beam, making it possible to process a relatively large area at once and also to modify the distribution of the supplied energy. The dissertation deals with surface heat treatment with a focus on the effect of beam deflection on the process. Furthermore, the influence of processing speed and defocusing of the electron beam is studied. The principles of electron beam technology and the summary of surface heat treatment of various materials are presented in the literary part of the thesis. The experimental part is focused on the influence of process parameters on processing in the solid phase, carried out on steel 42CrMo4, and in in the liquid phase, carried out on alloy NiCrBSi. Especially changes in structure, hardness, shape of the processed area and wear resistance are evaluated on processed samples. The results are also evaluated from an energy perspective. Furthermore, an optimum combination of technological parameters is recommended for solid and liquid phase surface heat treatment.
186

Studium odolnosti povrchových úprav ETICS vůči biotickému napadení / Study of the ETICS surface resistance to biotic attack

Těžká, Adéla January 2020 (has links)
This diploma thesis deals with the study of resistance of ETICS surface treatments to biotic attack. The theoretical part elaborates a research focused on biotic attack of facades of buildings insulated by contact insulation systems ETICS. Based on the information obtained during the elaboration of the bachelor thesis and further study, the optimization methodology of ETICS surface treatment resistance to biotic attack proposed in 2018 is elaborated. In the practical part, the proposed methodology is verified, evaluated and recommendations concerning the suitability of using the proposed methodology in construction practice are implemented.
187

Cílená příprava kompozitu na bázi PP + anorganické mikro resp. nano anorganické plnivo s různou adhezní mezivrstvou. / Targeted Preparation of Composite Based on PP with Inorganic Micro-, or Nanofiller with Different Adhesive Interlayer

Dombková, Julie January 2012 (has links)
The diploma thesis studies composite of PP and filler particle. As a particle filler was used commercially available CaCO3 (SOCAL 31). The submitted thesis had a goal to find new approaches and technologies of filler surface treatment in order to improve properties of composite materials. The plasma discharge behind static pressure was used for the surface treatment of the fillers. These fillers were afterwards analyzed by using of sedimentation analysis, turbidimetry, infra-red spectroscopy (FT-IR), X-ray diffraction analysis (XRD), scan electron microscopy (SEM), transmission electron microscopy and particle size distribution by laser diffraction. The composites with various volume parts of the fillers were prepared in PIB and studied by short-time tests. Furthermore, the influence of an adhesive layer on fracture mechanical properties of prepared composite was study. Regarding to experimental demand, there was not possible to realize long-term mechanical properties.
188

Korozní a chemická odolnost konverzních povlaků / Corrosion and Chemical Resistance of Conversion Coatings

Palková, Michaela January 2013 (has links)
The purpose of the thesis was to study chemical and corrosion resistance of selected conversion coatings. The corrosion and the possibilities of corrosion protection with focus on conversion coatings on aluminum and steel surface were described in the theoretical part. In the experimental part corrosion and chemical resistance of samples without the next treatment and samples with polyester powder coating and synthetic coating were tested.
189

Vliv fyzikální úpravy sráženého CaCO3 na vlastnosti kompozitu na bázi PP / Influence of physical treatment of precipitated CaCO3 on the properties of PP composites

Huczala, Vít January 2014 (has links)
The diploma thesis deals with study of system of polypropylene and inorganic filler. As filler was used commercially available particulate filler CaCO3 termed NPCC 201. The objective of the study was a surface plasma treatment of filler in order to obtain composite based on polypropylene. Mechanical properties of this composite will show significantly greater value than basic matrix. The filler was treated in dielectric barrier plasma discharge by atmospheric pressure. The characterization of filler was performed before and after plasma treatment by x-ray photoelectron spectroscopy (XPS), electron microscope (SEM) and sedimentation analysis. The distribution of particle size was measured by laser diffraction and by dynamic light scattering. The composite materials with various weight concentration of filler were prepared in POLYMER INSTITUTE BRNO by using the twin-screw extruder and the test specimens were prepared by the injection molding technology. Their mechanical properties was studied by using of short and long-term tests. The uniaxial creep testing in tension was used for study of long-term behavior of composites.
190

Analýza cen zámečnických konstrukcí v ceně objektu / Prices analysis of locksmith constructions included in the price of the construction object

Konečný, Jan January 2014 (has links)
The first part of this master’s thesis, which is more theoretical, contains information relating to prices in general, construction budgets, cost calculation of construction works and materials and costs. In the second part describes the use of materials and their properties, surface treatment and analysis of selected locksmith constructions.

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