Este trabalho avaliou in vitro a dureza e módulo de elasticidade de uma resina composta nanohíbrida (Tetric N-Ceram/Ivoclair-Vivadent) com diferentes cores, fotoativada por duas unidades com diferentes comprimentos de onda em 3 espessuras (1, 2 e 3mm) comparadas à partir da superfície irradiada (0mm). Os espécimes foram divididos em grupos (n=5): microdureza Knoop-KHN, ultramicrodureza-DUH e módulo de elasticidade-ME, cor (A2 e Bleach-M(BM), fotoativador LEDazul (Elipar Freeligth2/3M(750mW/25s/430-480nm(FL) e LEDazul/violeta Bluephase/Ivoclar/Vivadent (1200mW/cm²/15s/380-515nm(B15) e 30s(B30). Os espécimes foram armazenados por 24h/37ºC. Os ensaios de KHN foram realizados no HMV-2000/Shimadzu, com carga de 25gf/40s, e de DUH e ME no DUH 211S/Shimadzu com força de 10mN e tempo de espera de 0s. Foram realizadas 5 endentações na superfície irradiada (0mm) e na base das amostras (1, 2 e 3mm). A análise estatística foi realizada por ANOVA, Tukey e correlação de Pearson (p<0,01%). O teste de Pearson mostrou haver correlação direta entre a KHN e a DUH. A fonte FL promoveu maiores valores de KHN e de DUH para as duas resinas testadas; enquanto que a fonte B15, promoveu o maior valor de ME. Quanto às espessuras, 0 e 1mm apresentaram maiores valores de KHN e de DUH, e menores de ME que as espessuras de 2 e 3mm. A cor A2 apresentou maior valor de KHN e DUH e menor ME que a cor Bleach-M. Assim, de acordo com a metodologia proposta e os resultados apresentados pode-se concluir que apesar de a luz LEDazul/violeta propor uma maior eficácia na polimerização de resinas de cor clara, no tocante às propriedades avaliadas isso não foi verificado. / This study evaluated in vitro the hardness (micro and ultramicro) and elastic modulus of a nanohybrid composite resin (Tetric N-Ceram/Ivoclar-Vivadent) with different colors, light sources and thickness. The specimens were divided into groups (n=5): KHN-Knoop microhardness, DUH-nanohardness and ME-elastic modulus; colors: A2 and Bleach-M (BM); light sources: LEDblue Elipar Free light 2/3M-ESPE (750mW/cm²/ 25s/430-480nm- (FL)), LEDblue/violet Bluephase/Ivoclar-Vivadent (1.200mw/cm²/15s/380-515nm) (B15) and 30s (B30); thickness: 1mm, 2mm and 3mm, compared to the irradiated surface (0mm). Specimens were stored dry for 24hours at 37ºC after photo curing. Assays were performed at KHN in HMV-2000/ Shimadzu with load of 25gf at 40s and DUH/ME in DUH 211S/Shimadzu with force of 10mN and no hold time (0s). 5 indentations of each test were made in the surfaces opposites to the photo curing. A statistical analysis was performed by ANOVA, Tukey and Pearson correlation (p<0.01%). Pearsons Test showed a direct correlation between KHN and DUH. Comparison between KHN and ME in the studied resins indicated that the light source FL promoted higher values of KHN and DUH to both resins tested, whereas the B15 light source promoted the higher ME value. Regarding thickness 0mm and 1mm showed higher KHN and DUH and lower ME than 2 and 3mm thickness. A2 color showed higher KHN and DUH and lower ME than BM. Thus, according to the proposed methods and the presented results, the LEDblue/violet was not better for curing the light color of the nanohybrid resin, than LEDblue.

O módulo de elasticidade do concreto é uma propriedade muito importante para o projeto estrutural. Apesar do comportamento tensão-deformação não linear do concreto, uma estimativa adequada desta propriedade é fundamental para a análise estrutural, avaliação de efeitos de segunda ordem e verificações de deslocamentos. Em especial, o módulo de elasticidade dinâmico é uma propriedade muito importante na análise de vibrações excessivas. Todavia, sua determinação é tipicamente feita a partir do módulo de elasticidade estático. Os códigos normativos usualmente apresentam equações para estimativas do módulo de elasticidade estático a partir da resistência do concreto à compressão, densidade e tipo de agregado utilizado. Logo, outra limitação de tais estimativas é a não consideração de características da zona de transição além do tipo, fração volumétrica e dimensão dos agregados empregados na mistura. Por outro lado, a teoria dos materiais compósitos multifásicos permitiu, nos últimos tempos, o avanço dos modelos de previsão das propriedades do material. Portanto, o entendimento isolado do comportamento da pasta, areia, brita, argamassa e zona de transição é importante para a previsão do comportamento do compósito concreto. Desta forma, utilizou-se do ensaio acústico para a caracterização de variadas dosagens de pasta, argamassa, rocha e concreto. Assim, foi possível investigar a correlação entre as propriedades dinâmicas do compósito concreto e sua microestrutura. Variações de parâmetros como o fator água-cimento, maturidade, presença de superplastificante e tipo de agregado graúdo utilizado na mistura impuseram variados padrões microestruturais, e estes foram avaliados frente às propriedades dinâmicas do material, em especial, ao módulo de elasticidade dinâmico. Também foi possível a constatação da interdependência microestrutural entre o módulo de elasticidade dinâmico, módulo de cisalhamento e coeficiente de amortecimento. Já o coeficiente de Poisson apresentou pouca correlação com as outras propriedades supracitadas. Finalmente fez-se a inferência sobre a precisão das estimativas para módulo de elasticidade dinâmico através das equações empíricas contidas em normas e dos modelos teóricos obtidos via formulação para materiais bifásicos. Uma curva que correlaciona o módulo de elasticidade dinâmico e estático foi proposta para a maturidade referente aos 28 dias. / The modulus of elasticity of concrete is a very important property for structural design. Despite the nonlinear stress-strain behavior of concrete, an appropriate estimate of this property is essential for structural analysis, evaluation of second-order effects and excessive deflexions. In particular, the dynamic modulus of elasticity is an important property in analysis of excessive vibration. However, this value is often estimated from the static modulus. Design codes usually contain equations estimating the static modulus based on compressive strength of concrete, density and type of aggregate used. Another limitation of such estimates is neglecting the characteristics of the transition zone, and the type, size and volume fraction of the aggregates used in the mixture. On the other hand, the theory of multiphase composites materials has allowed in recent times, advances of predictive models of material properties. Therefore, the isolated understanding of paste behavior, sand, gravel, mortar and transition zone is important for predicting concrete composite behavior. In this way, the acoustic test it was utilized for characterization of the various mixes of the paste, mortar, rock and concrete. Thus, it was possible to investigate the correlation between the dynamic properties of the composite concrete and its microstructure. Variations in parameters such as the water-cement ratio, maturity, presence of superplasticizer and type of coarse aggregate used in the mix, imposed various microstructural patterns, and these were evaluated face to the material dynamic properties, in particular to the dynamic modulus of elasticity. Detected a microstructural interdependence between the dynamic modulus of elasticity, shear modulus and damping coefficient It was also. On the other hand, the Poisson ratio, presented low correlation with the other properties mentioned. Finally an inference about the accuracy of estimates for dynamic modulus of elasticity through empirical equations contained in standards and theoretical models obtained by the formulation for biphasic materials was made. A curve that correlates the dynamic and static modulus of elasticity was proposed for the age of 28 days.

Submitted by Eunice Novais (enovais@uepg.br) on 2018-09-06T21:57:41Z No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) EVELYN PATRICIA SANTOS ARIAS.pdf: 1455330 bytes, checksum: 8883f664c636c5ec3e0625c691880784 (MD5) / Made available in DSpace on 2018-09-06T21:57:41Z (GMT). No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) EVELYN PATRICIA SANTOS ARIAS.pdf: 1455330 bytes, checksum: 8883f664c636c5ec3e0625c691880784 (MD5) Previous issue date: 2018-04-24 / O objetivo deste estudo foi avaliar o grau de conversão, dureza e o módulo de elasticidade de três resinas Bulk Fill e duas resinas convencionais. Foram testadas as resinas Bulk Fill: Filtek™ Bulk Fill (FBP), Tetric N-Ceram Bulk Fill (TBF), Filtek™ Bulk Fill Flow (FBF); e adicionalmente duas resinas compostas convencionais: Empress Direct (ED) e Filtek™ Z350XT (Z350). Quarenta e cinco amostras cilíndricas (5 × 4 mm) foram confeccionadas a partir de cada um dos materiais por meio de uma matriz metálica. As matrizes foram preenchidas em incremento único para as resinas compostas Bulk Fill e em dois incrementos para as resinas compostas incrementais. As amostras foram armazenadas à seco no escuro à temperatura ambiente por 24 h antes da realização dos testes. O grau de conversão (GC) foi determinado utilizando a Espectroscopia de Infravermelho com Transformada de Fourier (FTIR). O teste de nanoindentação foi realizado nas superfícies de cada espécime, para obtenção da dureza (H) e módulo de elasticidade (E). Os dados foram submetidos a ANOVA 1 fator e teste de Tukey (α=0.05). Quanto o GC%, o maior foi obtido pelo grupo Z350 (69,92  3,5), e o grupo FBF (60,68  2,1) apresentou o valor significativamente inferior quando comparado com os outros grupos. Quanto os valores da nanodureza (GPa), os grupos FBF (0,3  0,02) e ED (0,3  0,01) apresentaram os menores valores de nanodureza e os grupos Z350 (0,9  0,04 ) e FBP (0,8  0,05 ) apresentaram os maiores valores de nanodureza. Quanto os valores do módulo de elasticidade (GPa), o grupo FBP apresentou os maiores valores de módulo de elasticidade (17,7  0,5) e o grupo FBF apresentou os menores valores de módulo de elasticidade (8,6  0,4). Conclui-se assim, que o compósito incremental (Filtek™ Z350XT) apresentou o maior desempenho do GC e o compósito Bulk Fill (Filtek™ Bulk Fill Flow) exibiu os menores valores de módulo de elasticidade e nanodureza. / The aim of this study was to evaluate the degree of conversion, hardness and elastic modulus of three Bulk Fill composites and two incremental-fill composites. The resin-composites: Filtek™ Bulk Fill (FBP), Tetric N-Ceram Bulk Fill (TBF), Filtek™ Bulk Fill Flow (FBF); and two incremental-fill composites: Empress Direct (ED), Filtek ™ Z350XT (Z350) were tested. Forty-five cylindrical specimens (5 × 4 mm) were made from each material in a metallic mold. Mold was filled in one increment for the Bulk Fill composites and in two increments for the incremental-fill composites. Specimens were stored dry in dark at room temperature for 24 h before testing. Degree of conversion (DC) was determined using Fourier transform infrared spectroscopy (FTIR). Nanoindentation was performed on the surfaces of each specimen, to obtain the hardness (H) and elastic modulus (E). Data for DC and H and E were analyzed by one-way ANOVA, Tukey's test (all at p<0,05). Z350 group (69.92  3.5) showed the highest DC% and FBF group (60,68  2,1) showed the lowest values when compared with the other groups. FBF (0.3  0.02) and ED (0,3  0,01) groups showed the lowest values for nanohardness (GPa) and Z350 (0,9  0,04 ) and FBP (0,8  0,05) groups showed the highest values for nanohardness. FBP group (17,7  0,5) showed the highest values for elastic modulus and FBF group (8.6  0.4) showed the lowest values for elastic modulus (GPa). It was concluded that incremental-fill composite (Filtek™ Z350XT) showed the highest performance DC and Bulk Fill composite (Filtek™ Bulk Fill Flow) showed the lowest values for elastic modulus and nanohardness.

Porous materials are essential to our everyday lives, for example as an effective catalyst in the cracking of crude oil, or as water softeners in washing powder. When developing novel functional porous materials, it is necessary to fully understand their structure-property relationships to maximise their ability to be used in industrially relevant settings. This thesis aims to understand the mechanical and adsorption properties of a class of porous solids metal-organic frameworks (or MOFs), which have many potential applications owing to their tuneable structures. Due to the inherent 3-D crystalline structure of MOFs, a wide range crystallographic techniques were used to determine structure-property relationships. To achieve maximum in-depth structural knowledge, both classical and quantum theoretical approaches were also applied to complement the understanding of both the energetics and structural details. Chapters One and Two begin with an overview of the state of the art studies carried out on MOFs, focusing on the use of high-pressure crystallography to understand their properties. In addition, there is emphasise on the importance of complementary computational methods that are used in the characterisation of MOFs. In Chapter Three, an isostructural series of MOFs (zeolitic imidazolate frameworks, or ZIFs) were studied for methanol adsorption by employing both experimental and molecular simulation techniques. These frameworks are gating materials, where the imidazole linker rotates upon adsorption of guest, and it was found that through ligand substitution the gate opening angle and onset pressure to gating could be tuned. By using high-pressure Xray crystallography the structure of the ZIFs were studied upon the uptake of guest and the degree of ring rotation quantified. In combination with periodic DFT and grand canonical Monte Carlo simulations the energy barrier to rotation and energies of adsorption could be calculated, respectively. Chapter Four focuses on one ZIF in particular, ZIF-8 ((Zn6(MeIm)12, MeIm = 2- methylimidazole) and details the adsorption of a selection of gases into the pores. The experimental method of cryogenic gas loading into a diamond anvil cell in this chapter is novel to MOFs. This method, in combination with molecular crystallography, is used to determine the structural response of the framework to guest-uptake as well as the crystallographic positions of the adsorption sites. In combination with in silico methods, the adsorption energies of guest-sites could be calculated, detailing which interactions drive the gating behaviour. The method of cryogenic loading highlighted how extreme conditions can be used to extract useful information about structural behaviour of MOFs on uptake of gas molecules into the pores, and when used in combination with computational methods, we have a powerful tool to analyse both positions and energies of adsorption sites. With this information, progress can be made in developing MOFs to maximize favourable interactions and lead to the development of MOFs with better selective gas storage properties. Chapter Five focuses on the synthesis and characterisation of the physical properties of a series of Zr-containing MOFs, called UiO-MOFs. The high valency of Zr(IV) and 12-fold coordination of the metal cluster in these materials, are associated with high shear and bulk moduli, which surpass those of other MOFs. A combination of single-crystal nano-indentation, high-pressure X-ray diffraction studies, density functional theory (DFT) calculations, and first-principles molecular dynamics (MD) simulations were used to determine the compressibility, elasticity and hardness of these materials, whose mechanical robustness was correlated to their different structural features, in-particular, how using non-linear linkers between the metal clusters stabilises the framework to compression. Chapter Six expands upon the series of Zr-MOFs in Chapter Five, and looks at how the mechanical properties of these MOFs are affected upon increasing the linker length. The experimentally determined elastics modulus of one of the frameworks, UiO-sdc (Zr6O4(OH)4(sdc)6 where sdc =4,4’-stillbene dicarboxylate), was found to lie above those of other highly porous MOFs. In addition, the elastic modulus was found to decrease linearly as a function of increasing the linker length, extending the structure-property relationships determined in Chapter Five.

Neste trabalho determinamos o módulo elástico de filmes finos metálicos nanoestruturados. Os metais estudados, platina, ouro e paládio foram depositados utilizando a técnica de Metal Plasma Immersion Ion Implantation and Deposition. Um novo método foi utilizado para as medidas de módulo elástico, no qual cantiléveres de microscopia de força atômica são uniformemente recobertos com os filmes finos metálicos. Medidas das frequências de ressonância dos cantiléveres foram realizadas antes e depois dos recobrimentos com os filmes. Usando a teoria de vibração de barras, determinamos os valores dos módulos elásticos desses filmes. Obtivemos valores que estão entre 7 e 12% menores do que os respectivos módulos elásticos dos metais na forma de bulk. Um modelo simples em conta o caráter nanoestruturado dos materiais. Caracterizações complementares foram realizadas como : microscopia de tunelamento, difração de raios X e RBS (Rutherfor Backscattering Spectrometry). / In this work we have determined the elastic moduli of nanostructured metallic thin films. The analyzed metals, platinum, gold and palladium, have been deposited using the technique Metal Plasma Immersion Ion Implantation and Deposition. A new method was adopted to determine the elastic moduli, where cantilevers of atomic force microscopy were uniformly coated with thin films. The resonance frequencies of the cantilevers have been measured before and after the films coating. The elastic moduli were finally obtained using the vibration beam theory. The determined elastic constants are smaller than the respective bulk moduli: about 12% for Pt and Au and about 7% for Pd. A simple model is proposed to explain the softening of the elastic moduli taking into account the nanostructured character of the films. Additional characterizations have been done like: scanning tunneling microscopy, X-ray diffraction and RBS (Rutherford Backscattering Spectrometry).

O presente estudo teve como objetivo avaliar o desempenho de quatro resinas bulk fill (Filtek Bulk Fill (FBF), Opus Bulk Fill (OBF), Sonicfill (SF) e Tetric N-Ceram Bulk Fill (TNBF)) e uma resina convencional (Charisma Diamond (CD)) quanto às seguintes propriedades: resistência à flexão (RF), módulo de elasticidade (ME) e dureza Knoop (KHN) em função da profundidade e após a realização de um envelhecimento acelerado. Corpos de prova em formato de barra foram confeccionados simultaneamente em diferentes profundidades (1, 2, 3, 4 e 5 mm) para realização dos testes de resistência à flexão (n=10), módulo de elasticidade (n=10) e dureza Knoop (n=3). Os testes foram realizados em dois momentos, previamente e após a realização de um envelhecimento acelerado, que consistiu na realização de uma termociclagem com banhos alternados em água a 5 e 55ºC, com 1 min de imersão em cada, por 2000 ciclos. Os resultados para o teste de RF e ME mostraram que os valores para estas duas propriedades diminuíram em função da profundidade e após a realização da termociclagem para todas as resinas estudadas. Apenas a resina TNBF não apresentou diferença estatística para valores de ME após o envelhecimento acelerado. Quanto à dureza, os valores também diminuíram em função da profundidade, porém aumentaram após a realização do envelhecimento acelerado. Apenas a resina SF não apresentou diferença estatística entre os valores de dureza antes e após o envelhecimento. A resina convencional CD após a ciclagem térmica foi a única que apresentou relação base/topo (2 mm) acima de 80%. Nenhuma das resinas do tipo bulk fill apresentou uma relação base/topo acima de 80% para a dureza quando avaliadas na espessura máxima recomendada. Com base nos resultados obtidos, pode-se afirmar que, quando fotoativadas na espessura máxima recomendada, apenas a resina convencional CD apresentou resultados condizentes com a homogeneidade esperada em todas as condições deste estudo. Entretanto, para as resinas do tipo bulk fill, pode-se observar que as propriedades estudadas, de modo geral, sofreram uma diminuição significativa em função da profundidade. Para o envelhecimento, a dureza, diferentemente dos outros parâmetros, mostrou uma tendência de aumento. / The purpose of this study was to evaluate the performance of four bulk fill resins (Filtek Bulk Fill (FBF), Opus Bulk Fill (OBF), Sonicfill (SF) and Tetric N-Ceram Bulk Fill (TNBF)) and a conventional resin (Charisma Diamond (CD)) for the following properties: flexural strength (FS), flexural modulus (FM) and Knoop hardness (KHN) as a function of depth and after accelerated aging. Specimens were made simultaneously with different depths (1, 2, 3, 4 and 5 mm) for flexural strength tests (n = 10), flexural modulus (n = 10) and Knoop hardness (n = 3). The tests were carried out in two moments, before and after the accelerated aging process, which consisted of thermocycling with alternating baths in water at 5 and 55ºC, with 1 min immersion in each, for 2000 cycles. The results for the FS and FM tests showed that the values for these two properties decreased as a function of depth and after the thermocycling for all the studied resins. Only TNBF resin showed no statistical significant differences in FM values after accelerated aging. For the hardness test, values also decreased as a function of depth, but increased after accelerated aging. SF resin was the only one that showed no statistical significant differences between hardness values before and after aging. CD, after thermal cycling, was the exclusive resin to show a bottom/top ratio above 80%. None of the bulk fill resins had a bottom/top ratio above 80% for hardness when evaluated at the maximum recommended thickness. Based on the results obtained, it can be stated that, when photoactivated at the maximum recommended thickness, only the conventional resin CD presented results consistent with the expected homogeneity in all the conditions of this study. However, for bulk fill resins, it can be observed that the studied properties, in general, suffered a significant decrease as a function of depth. For aging, the hardness, unlike the other parameters, showed a tendency to increase.

A comparison of concrete containing recycled concrete coarse aggregates and natural coarse aggregates subjected to high strain, low cycle compressive fatigue is presented. Using a strain based feedback control loop, concrete cylinders are compressed at 15µε/s to a specified strain then unloaded to zero stress for 10 cycles. After cycling, all samples are loaded to a strain of 0.008. Direct concrete material variables are the water to cement (w/c) ratio, taken as 0.60, 0.45, and 0.39, and percent coarse recycled concrete aggregate content, varied from zero to 100 percent. The primary testing variable is the specified unloading strain. Unloading strains include 60, 75, 90, 100, and 120 percent of the strain at peak stress. Ten batches of concrete were made, generating a total of 224 samples for testing. Findings confirm previous research showing a reduction in strength with increasing recycled concrete coarse aggregate content, an equivalent concrete with only 25 percent replacement of natural coarse aggregates and an equivalent strength concrete with a decrease in the w/c ratio and 100 percent recycled concrete coarse aggregates. Fatigue testing indicates that each cycle’s maximum stress remains unchanged, but the stiffness degrades more rapidly with increasing recycled aggregate content and a constant w/c ratio.

The bottom-up processing techniques used for making Microelectromechanical systems (MEMS) devices can produce material properties different from bulk processing. The material properties must be evaluated with the process parameters used and for changes in the process parameters. The mechanical properties are needed to design MEMS devices. A material of interest for MEMS devices is nickel titanium (NiTi) shape memory alloy (SMA) because of the high work output (~107 J/m3). This thesis will focus on the fabrication of thin film NiTi by DC magnetron sputtering deposition and testing mechanical properties of the fabricated films by nanoindentation. Thin film NiTi SMA was successfully created by DC magnetron sputtering deposition and high vacuum annealing in the Microfabrication Laboratory at California Polytechnic State University – San Luis Obispo. Characterization of the thin film by nanoindentation produced an elastic modulus of the thin film NiTi SMA with the developed processing parameters was 67.9 GPa with a hardness of 2.1 GPa. The measured thin film NiTi elastic modulus was greater than bulk NiTi of 40 GPa because of the residual stress from the deposition process. The shape memory effect was evaluated at the nanometer scale by measuring the nanoindents before and after thermally inducing a phase transformation. A maximum indentation depth recovery of 58% was measured upon the heat induced martensitic phase transformation. The low recovery was attributed to the high strain of 8% induced by the Berkovich tip. The effects of deposition power on the NiTi as-sputtered film stress, elastic modulus, hardness, and electrical conductivity were evaluated. At the highest sputtering deposition power of 450 Watts, an elastic modulus of 186 GPa with a hardness of 8.3 GPa was measured by nanoindentation. An increase in deposition power increased the residual film compressive stress, elastic modulus, and hardness while the electrical resistivity increased. The mechanisms for the measured properties are discussed in this thesis.

Orientador: Aldiéris Alves Pesqueira / Coorientador: Daniela Micheline dos Santos / Banca: Daniel Galera Bernabé / Banca: Aline Satie Takamiya / Resumo: O melhor método para atingir uma superfície lisa das cerâmicas odontológicas é uma questão de controvérsia, devido à falta de um protocolo estabelecido na literatura. Atualmente, há o questionamento se os kits de polimento para consultório resultam em um acabamento e polimento superior ou semelhante ao obtido com o glaze, sendo esta questão de suma importância. Dessa forma, o presente estudo teve como objetivo avaliar as características físicas, químicas e mecânicas da cerâmica de dissilicato de lítio para o sistema CAD/CAM, submetida a diferentes protocolos de polimento e após diferentes ciclos de envelhecimento térmico, com e sem repolimento. Foram confeccionados 204 espécimes (14x4x1,2 mm) divididos em 07 grupos, de acordo com os polimentos realizados em suas superfícies e ciclos de ciclagem térmica (CT). Três sistemas de polimento foram avaliados: Glaze, Kit de polimento Ceramisté (Shofu) e Kit de polimento OptraFine (Ivoclar). O envelhecimento ocorreu por meio de diferentes testes: T1 - armazenamento em água destilada por 24 horas (controle); T2 - após 21.900 ciclos de 5 e 55oC por 30 segundos de CT (CT1); T3 - após 43.800 ciclos de CT (CT2); e após 21.900 ciclos de CT + repolimento dos espécimes + 21.900 ciclos de CT. Foram consideradas 5 variáveis de resposta: (1) rugosidade superficial (Ra), (2) energia de superfície (ES), (3) microscopia eletrônica de varredura (MEV) associada a espectroscopia de energia dispersiva (EED), (4) resistência à flexão (RF) e (5) módulo de... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The best method to achieve a smooth surface of dental ceramics is a controversy, due to the lack of a protocol established in the literature. Nowadays, the question is whether office polishing kits result in superior finishing and polishing or similar to that obtained with glaze, being this issue of utmost importance. In this way, the present study aimed to evaluate the physical, chemical and mechanical of lithium disilicate ceramics for the CAD / CAM system, submitted to different clinical polishing protocols and after cycles of thermal fatigue with and without repolishing. A total of 204 specimens of 14x4x1.2mm dimensions was prepared and divided into 07 groups according to the polishes performed on their surfaces and thermal cycling cycles (TC). Three polishing systems will be evaluated: Glaze, Ceramisté Polishing Kit (Shofu) and OptraFine Polishing Kit (Ivoclar). The aging was perfomed by different tests: T1- storage in distilled water for 24 hours (Control); T2 - after 21,900 cycles of 5 and 55oC for 30 seconds of TC (TC1); T3 - after 43.800 cycles of TC (TC2) and after 21.900 cycles of TC + repolishing of the specimens + 21.900 cycles of TC. Five response variables were considered: (1) surface roughness (Ra), (2) surface energy (SE), (3) scanning electron microscopy (SEM) associated with energy dispersive spectroscopy (EDS), (4) flexural strength (FS), and (5) modulus of elasticity (ME). The quantitative data were submitted to ANOVA (two way) and Tukey test with signifi... (Complete abstract click electronic access below) / Mestre

Foundries today use temporary molds made from silica sand with a resin bonding agent to hold a form until the metal is poured. With the aid of computer simulations, the molds are designed to produce good castings with minimal pattern iterations by calculating cooling and porosity. Stress analysis simulations are being developed using the current software, but the known mechanical properties for the sand mold are minimal and incomplete. This study measures the elastic modulus of bonded sand as a function of temperature to obtain baseline data for the model. Following ASTM standards, a three point bend test is used to measure the elastic modulus of chemically bonded sand as a function of temperature to better understand the complex nature of the mold as it undergoes heating and cooling. Multiple measurements of the elastic modulus of PUNB bonded silica sand are performed from room temperature to 500°C in a nitrogen atmosphere to capture the changes in the elastic modulus under heating. It is found that for an intermediate heating rate of 8°C/min, the elastic modulus decreases steeply from a room temperature value of about 3,600 MPa to 600 MPa at 125°C. Between 125°C and 250°C, the elastic modulus is relatively constant. Above 250°C, it increases to 1,200 MPa at 280°C and then decreases again to 800 MPa at 350°C. Above 350°C, the elastic modulus increases linearly with temperature until it reaches 2,200 MPa at 500°C. At approximately 500°C, the strength of the bonded sand vanishes. At a given temperature above 125°C, the elastic modulus can vary by more than a factor of two depending on the heating rate. Furthermore, the elastic modulus agrees with previous steady state temperature measurement literature when specimens are held at a constant temperature until the elastic modulus reach steady. It is also found that the addition of black iron oxide has no effect on the elastic modulus, whereas solvent removal before a test increases the stiffness of the bonded sand at temperatures below 150°C.