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Vickers indentation (IF) and single-edge-V-notched beam (SEVNB), to measure the fracture toughness (K

The objective of this work was to study the effect of different heating-up procedures and isothermal treatment times on crystallization, densification and properties of a sintered non-stoichiometric lithium silicate glass-ceramic. Glass samples containing SiO2, Li2O and K2O as main constituents, besides minor amounts of other oxides such as Al2O3, P2O5 and ZrO2, were melted at 1500 °C - 60 min and subsequently fragmented (

Fatigue is one of the most important properties to be considered in ceramic dental implants due to cyclic mechanical stresses arising from the chewing process. In this work, the fatigue behaviour of hydrothermally degraded ZrO2-based ceramics stabilized with 3mol% Y2O3 (3Y-TZP) was studied in 4-point bending tests. Samples of 3Y-TZP were compacted (100MPa), sintered at 1475 °C for 2 h, polished and hydrothermally degraded in an autoclave as described in the ISO-13356 standard. The samples were characterized by their relative density, crystalline phase composition, microstructure and surface roughness. The highly dense (>99.6%TD) sintered 3Y-TZP ceramics has only tetragonal t-ZrO2 phase, even after hydrothermal ageing. Furthermore, the ceramic materials presented a Vickers hardness of 12.7±0.2GPa, a fracture toughness of 7.1±0.3MPa•m1/2 and a 4-point bending strength of 940.1±67MPa. Based on the bending test results 5 different stress levels for the fatigue tests were selected and conducted by cyclic 4-point bending obtaining the S-N curve. Weibull statistics was used for the statistical analysis. The fatigue tests indicate that the limit of fatigue resistance of this 3Y-TZP ceramics is around 550MPa, i.e. higher than the limits established in the ISO-13356 standard for the use of Y-TZP ceramics for the manufacture of implants. The fatigue behaviour of the investigated 3Y-TZP ceramics was related to the toughening mechanisms acting in Y-TZP ceramics, such as transformation toughening related to t→m phase transformation and microcracking.

Made available in DSpace on 2021-06-25T11:09:38Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-04-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ) Fracture resistance and translucency are among the most important properties for the use of lithium silicate glass ceramics as dental prostheses, both being greatly influenced by the temperature of the crystallization heat treatment. In this work, the effect of short time heat treatments at different temperatures on the lithium metasilicate (Li2SiO3) → lithium disilicate (Li2Si2O5) phase transformation and resulting properties was investigated. Commercial Li2SiO3 samples were heat treated under vacuum for 7 min, at 820 °C, 830 °C and 840 °C, to induce the phase transformation into Li2Si2O5. The heat treated samples were characterized by their phase composition (XRD), microstructure, mechanical properties (Vickers Hardness, fracture toughness, bending strength and elastic parameters) and translucency. The results indicate that 814 °C is the onset temperature for the crystallization of lithium disilicate (Li2Si2O5). A progressive conversion of Li2SiO3 into Li2Si2O5, besides the reduction of the amorphous phase content is observed with increasing temperature. Furthermore, the increasing amount of the Li2Si2O5 phase and the concomitant reduction of the amount of amorphous phase resulted in a slight reduction of the hardness from 6.13 ± 0.22 to 5.76 ± 0.17 GPa, a slight increase in fracture toughness from 1.30 ± 0.02 to 1.60 ± 0.03 MPa m1/2 and in a significant improvement of the bending strength from 166 ± 22 to 303 ± 59 MPa. The improvement in mechanical properties is associated with the reduction of amorphous phase and increasing amount of the Li2Si2O5 phase, which is composed of elongated grains with high aspect ratio. However, translucency diminished 40% comparing samples treated at 820 °C or 840 °C, which is attributed to the reduction of the amount of intergranular amorphous phase. UNESP/FEG Universidade Estadual Paulista - Faculdade de Engenharia de Guaratinguetá, Av. Ariberto Pereira da Cunha, 333, Portal das Colinas UERJ/FAT Universidade do Estado do Rio de Janeiro Faculdade de Tecnologia, Rod. Presidente Dutra, km 298 UFF/ISNF Universidade Federal Fluminense, Av. Dr. Silvio Henrique Braune, 22, Centro UFSJ Universidade Federal de São João DeĺRei, Pça Frei Orlando 170, S. J.del Rei-MG UNESP/FEG Universidade Estadual Paulista - Faculdade de Engenharia de Guaratinguetá, Av. Ariberto Pereira da Cunha, 333, Portal das Colinas CNPq: 308684/2013-3 CNPq: 311119/2017-4 FAPERJ: E-26-201.476/2014 FAPERJ: E26-202.997/2017

The present work aims to evaluate the crystalline phases and microstructure of a TiC–Ti3SiC2 ceramic composite, obtained by mechanical alloying of Ti, C and Si powders and subsequent sintering. A mechanical alloying technique in a planetary ball mill for 1, 10, 50, 100 and 200 h using Ti, Si and C powders with molar ratios of 3:1:2 as feedstock in argon (Ar) gas was employed to prepare nano-sized Ti–Si–C powders. TiC crystallite size and lattice strain were evaluated by X-ray diffraction analysis (XRD) and the morphological characteristics and particle size distribution were examined using scanning electron microscope (SEM). After milling, a reduction of the average particle size and crystallinity is observed. Furthermore, after 10 h of milling time, TiC starts to crystallize. The powder mixture obtained after 200 h of milling was compacted and sintered at 1200 °C under controlled atmosphere, for 15 min, 2 h or 4 h with a heating rate of 5 °C/min. Almost full densification of samples sintered for 2 h and 4 h has been achieved, with relative densities close to 98.8±0.2% and TiC and Ti3SiC2 as crystalline phases with an average crystallite size of TiC near 0.7 μm. Rietveld refinement indicates that the majority TiC-cubic phase (>85 vol%) presents a unit cell volume of 8.03 nm3 after sintering at 1200 °C. Despite the maintenance of the volume of the hexagonal unit cell of Ti3SiC2, (15.05 nm3), the increase of the isothermal sintering time resulted in an increase of the lattice parameter “a”, from 0.315 nm to 0.320 nm, and a reduction of the lattice parameter “c” from 1.750 nm to 1.705 nm. The control of the changes in the residual stresses within the TiC matrix and the Ti3SiC2 precipitates, which is associated with the deformation in the lattice parameters, must be controlled to achieve high fracture toughness in the composite.

The effects of different surface finishing procedures on the translucency of yttria stabilized zirconia ceramics (ZrO2) were evaluated. ZrO2-3mol.%Y2O3 (designed Zr3) or ZrO2-5mol.%Y2O3(Zr5) specimens with thickness varying between 0.5 and 1.5 mm were obtained by sintering at 1500 °C for 2 h. Surface finishing of the sintered specimens was done in three distinct manners: polishing with diamond pastes, blasting with Al2O3 particles and blasting with Al2O3–SiO2 particles, according to the preparation protocol for dental prostheses. These sample groups were characterized by X-Ray diffraction analysis, scanning electron microscopy, surface roughness and spectrophotometry. The sintered ceramics exhibited relative densities higher than 99% and were composed of 68.5% and 31.5%of tetragonal (t)-ZrO2 and cubic(c)-ZrO2 for composition Zr3 and 25.2% and 74.8% for composition Zr5, respectively. Furthermore, 1.5 to 1.8% of monoclinic (m)-ZrO2, has been found in the blasted surfaces. The average grain size varied from 0.5 μm for Zr3 to 1.45 μm for the Zr5 samples. After polishing, all samples presented a surface roughness Raof about 0.05 μm, while blasting resulted in an increased roughness ranging between 1.24 μm and 1.49 μm.Samples rich in (c)-ZrO2 phase (Zr5) are more translucent than samples rich in (t)-ZrO2 (Zr3) because of their larger grain size and because the cubic phase is less anisotropic than (t)-ZrO2. Furthermore, the translucency of thinner samples is more affected by abrasive blasting because they also present the highly anisotropic monoclinic(m)-ZrO2 phase and, therefore, the reduction of translucency is more pronounced. Parameters such as grain size, crystalline phase composition, porosity and grain boundary density are used to explain the phenomena involved in the differences of translucency of these materials.

Ceramic composites based on (Ce, Y)-TZP/Al

This study investigates the simulation of the mechanical behavior of a bioceramic composite based on (Ce,Y)-TZP reinforced with equiaxed AlA commercial (Ce, Y)-TZP/AlThe sintered ceramic composite material presented relative density99%, high resistance to hydrothermal degradation, average hardness of 1435 ± 35 HV, fracture toughness KThe differences observed are attributed to the complex coupled toughness mechanisms of this material, not included in the finite element simulations.

The present work reports the effect of the extrusion nozzles' size and consequent residual porosity on the flexural strength of 3Y-TZP bioceramics fabricated by direct write assembly technology.A printable ink containing a volume fraction of 45% of 3Y-TZP (ZrOThe sintered samples exhibited relative densities in the range of 78% (nozzle Ø 0.41 = mm) and 82% (nozzle Ø 0.25 = mm), i.e., a slight increase in the residual interfilamentous porosity is observed, as the extrusion tip diameter increases, while linear shrinkage is statistically similar (≈25%). Likewise, a progressive reduction of flexural strength and Weibull modulus as nozzle diameter increases was noticeable, being respectively σX-ray diffraction analyses on the fracture surface of flexural test samples suggests that the toughening mechanism by tetragonal→ monoclinic phase transformation is the main responsible for the mechanical strength of this structural ceramic. Additionally, the reduction of flexural strength for samples printed with extrusion nozzle of 0.41 mm could be explained by the surface roughness of the bending surfaces, as well as the lower effective resistance to crack-propagation arising from the higher size of residual pores on the fracture surface.

Made available in DSpace on 2021-07-14T10:26:01Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-12-13. Added 1 bitstream(s) on 2021-07-14T11:30:01Z : No. of bitstreams: 1 S0366-69132020000100030.pdf: 2969385 bytes, checksum: 6f7cb1d7980557e113a2dfcaefef07cc (MD5) Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) O objetivo deste estudo foi caracterizar e avaliar as propriedades físicas e mecânicas de uma zircônia experimental para aplicação odontológica e comparar os resultados da resistência à flexão biaxial com a simulação de elementos finitos (MEF). Amostras de zircônia tetragonal estabilizada com ítria (Y-TZP) foram sinterizadas a 1475 °C/2 h e caracterizadas por difração de raios X, microscopia eletrônica de varredura, densidade relativa, resistência à flexão usando teste de pistão em três bolas (P-3B) e módulo de Young. A partir dos resultados de resistência à flexão, foram realizadas simulações numéricas utilizando o software Abaqus. O modelo completo utilizou 70216 elementos. Os resultados apontaram para densificação total em amostras sinterizadas, ZrO2 tetragonal e cúbica como fases cristalinas, tamanho de grão de 0,6±0,2 μm, módulo de Young de 195±4 GPa, resistência à flexão de 1191±9 MPa e módulo de Weibull m=16,3. A simulação numérica indicou uma resistência à flexão próxima de 1100 MPa, com diferença menor que 7% em relação aos resultados experimentais. Os resultados foram comparados associando as propriedades físicas e mecânicas de Y-TZP com seus fenômenos intrínsecos, como a transformação tgm e o domínio ferroelástico. The objectives of this study were to characterize and evaluate the physical and mechanical properties of an experimental zirconia for dental application and compare the biaxial flexural strength results with the finite element simulation (FEM). Yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) ceramic samples were sintered at 1475 °C/2 h and characterized by X-ray diffraction, scanning electron microscopy, relative density, flexural strength using piston-on-three balls (P-3B) test and Young’s modulus. From the flexural strength results, numerical simulations were performed using Abaqus software. The complete model used 70216 elements, considering the components of the test. The results indicated full densification of sintered samples, ZrO2-tetragonal and ZrO2-cubic as crystalline phases, and average grain size of 0.6±0.2 μm. Mechanical characterization of sintered samples indicated Young’s modulus of 195±4 GPa, flexural strength of 1191±9 MPa and Weibull modulus m=16.3. FEM simulation indicated a flexural strength close to 1100 MPa, with a difference lower than 7% in relation to the experimental results. The results were compared associating the physical and mechanical properties of Y-TZP with its intrinsic phenomena such as tgm transformation and ferroelastic domain. Universidade Federal Fluminense, Escola de Engenharia Industrial Metalúrgica de Volta Redonda Universidade do Estado do Rio de Janeiro, Faculdade de Tecnologia de Resende Universidade Estadual Paulista, Faculdade de Engenharia de Guaratinguetá Universidade Estadual Paulista, Faculdade de Engenharia de Guaratinguetá FAPERJ: E26-201.476/2014; E26-202.997/2017; E26-211.760/2015 CNPq: 311119/2017-4; 305194/2015-1

Made available in DSpace on 2019-10-06T15:35:15Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-06-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ) In this work, the influence of milling strategy and cutter wear on the flexural strength of sintered Y-TZP ceramics machined in a CAD-CAM system, was investigated. Pre-sintered Y-TZP blocks were machined with tungsten carbide (WC) milling cutters and divided into three groups: a) samples machined with New Cutting Tools (NCT); b) samples machined with End-of-life cutting tools (ELCT); and c) samples machined and subsequently polished. The samples were machined parallel and perpendicularly to the diameter of pre-sintered Y-TZP blocks aiming to evaluate the effect of the machining orientation on roughness. After cutting, the specimens were sintered at 1530 °C for 2 h and characterized. After sintering, dense Y-TZP samples presenting grain size average of 0.81 ± 0.23 μm, hardness of 1205 ± 12 HV, K C of 7.7 ± 0.4 MPam 1/2 and flexural strength of 1207 ± 199 MPa were obtained. Furthermore, the control roughness (polished surfaces) presented R a = 0.058 ± 0.011 μm. The surface roughness of the samples was influenced by the machining methodology using NCT mills, with R a = 0.386 ± 0.149 μm and R a = 0.292 ± 0.105 μm for samples machined parallel and perpendicularly to the pre-sintered Y-TZP blocks, respectively. The use of ELCT led to a roughness increasing (R a = 0.582 ± 0.183 μm for samples milled perpendicularly, and R a = 0.919 ± 0.164 μm for samples cut parallel to the pre-sintered blocks. The flexural strength of the sintered Y-TZP decreases with use of ELCT as consequence of surface roughness increasing, resulting from wear of WC mills, which presented chippings with sizes ranging from 30 to 340 μm in the cutting edge. Universidade do Estado do Rio de Janeiro - Faculdade de Tecnologia de Resende UERJ-FAT, Rodovia Presidente Dutra, km 298 Universidade Estadual Paulista - Faculdade de Engenharia de Guaratinguetá UNESP/FEG, Av. Ariberto Pereira da Cunha, 333, Portal das Colinas Centro Universitário de Volta Redonda - UniFOA, Av. Paulo Erlei Alves Abrantes, 1325 - Três Poços Instituto Militar de Engenharia Materials Science Department, Pça Gen. Tibúrcio, 80, Praia Vermelha Universidade Estadual Paulista - Faculdade de Engenharia de Guaratinguetá UNESP/FEG, Av. Ariberto Pereira da Cunha, 333, Portal das Colinas CNPq: n° 311119/2017-4 FAPERJ: n° E26-201.476/2014

Este trabalho avaliou o impacto da concentração de ítria (Y2O3) e de um agente colorante (Fe2O3) nas propriedades cristalográficas, morfológicas, ópticas e mecânicas da zircônia. Para isto, pós comerciais de ZrO2 contendo 3% mol (Zpex) e 5% mol (Smile) de Y2O3, dopados ou não com Fe2O3, foram caracterizados quanto a sua composição química e massa especifica. Os pós de partida foram compactados por prensagem uniaxial (100 MPa) em cinco espessuras diferentes, entre 0,35 e 1,35 mm, em regime de triplicata, e divididos em dois lotes, referentes aos pós de partida. Cada lote foi submetido a diferentes temperaturas de sinterização (1475ºC, 1500ºC, 1550ºC ou 1600ºC) por um período de 2 horas. As amostras foram caracterizadas por difração de raios X, refinamento de Rietveld, microscopia eletrônica de varredura, densidade aparente, rugosidade por perfilometria, dureza, módulo de elasticidade, tenacidade à fratura, por meio das técnicas de indentação Vickers e SEVNB, e resistência à flexão. A translucidez foi avaliada por espectrofotometria (razão de contraste e diferença de coloração). Resultados indicam que: Todas amostras apresentaram densificação superior a 99% para todas as condições de sinterização, contudo as amostras Zpex apresentaram resultados de densidade aparente ligeiramente maiores, no máximo 0,5%; O aumento do teor de ítria foi acompanhado pela presença de fase ZrO2-cúbica e do aumento do tamanho médio dos grãos, de 0,8 µm para 2,3 µm para a maior temperatura de sinterização analisada, 1600°C; O aumento da temperatura de sinterização induziu o aumento do módulo de elasticidade em todas as amostras, na ordem de 190 GPa para 225 GPa; Os valores aferidos para dureza Vickers permaneceram na ordem de 13 GPa independente do pó de partida ou condição se sinterização analisada; As amostras Zpex apresentaram variações de tenacidade à fratura na ordem de 6,7 a 8,2 MPa.m1/2 enquanto as amostras Smile apresentaram resultados na ordem de 3,6 a 3,9 MPa.m1/2 em função da temperatura de sinterização; Os resultados de resistência à flexão das amostras Zpex apontam para valor médio de 1200 MPa enquanto as amostras Smile indicam valor médio de 600 MPa; Já os resultados de espectrofotometria apontam para variação do RC em função da espessura na ordem de 30% para as amostras Zpex e 23% para as amostras Smile, e variação da RC medida em função do percentual de Y2O3 na ordem de 6 a 10% em função da presença ou não de agente colorante; Os resultados de variação de coloração apontam para resultados máximos na ordem de 5 a 8,2, respectivamente para as amostras Smile e Zpex, para as amostras com 0,35 mm de espessura. Os resultados apontam para perdas expressivas de propriedades mecânicas para as amostras Smile, contudo, os resultados medidos são coerentes com às exigências para aplicações dentárias que possuem foco em propriedades estéticas, classes 1 a 3. Os resultados medidos para as propriedades ópticas justificam e corroboram os ganhos induzidos pelo aumento do percentual de Y2O3 This work evaluated the impact of the concentration of yttria (Y2O3) and a coloring agent (Fe2O3) on the crystallographic, morphological, optical and mechanical properties of zirconia. For this, commercial ZrO2 powders containing 3 mol% (Zpex) or 5 mol% (Smile) of Y2O3, doped or not with Fe2O3, were characterized for their chemical composition and specific mass. The starting powders were compacted by uniaxial pressing (100 MPa) in five different thicknesses, between 0.35 and 1.35 mm, in triplicate regime, and segregated into two batches for the starting powders. Each batch was subjected to different sintering temperatures (1475ºC, 1500ºC, 1550ºC or 1600ºC) for a period of 2 hours. The samples were characterized by X-ray diffraction, Rietveld refinement, scanning electron microscopy, bulk density, profilometry roughness, hardness, modulus of elasticity, fracture toughness, using Vickers and SEVNB indentation techniques, and flexural strength. . Translucency was assessed by spectrophotometry (contrast ratio and color difference). Preliminary results indicate that: All samples showed densification greater than 99% for all sintering conditions, however Zpex samples showed slightly higher apparent density results, at most 0.5%; The increase in yttria content was accompanied by the presence of the cubic ZrO2 phase and the increase in average grain size from 0.8 µm to 2.3 µm for the highest sintering temperature analyzed, 1600 ° C; The increase of sintering temperature induced the increase of elastic modulus in all samples, in the order of 190 GPa to 225 GPa; The measured values for Vickers hardness remained in the order of 13 GPa regardless of the starting powder or sintering condition analyzed; Zpex samples presented fracture toughness variations in the order of 6.7 to 8.2 MPa.m1/2 while Smile samples presented results in the order of 3.6 to 3.9 MPa.m1/2 as a function of the temperature of sintering; The flexural strength results of Zpex samples point to an average value of 1200 MPa while Smile samples indicate an average value of 600 MPa; Spectrophotometry results indicate RC variation as a function of thickness in the order of 30% for Zpex samples and 23% for Smile samples, and RC variation as a function of Y2O3 percentage in the order of 6 to 10% in function of the presence or absence of coloring agent; The color variation results indicate maximum results in the order of 5 to 8.2, respectively for Smile and Zpex samples, for 0.35 mm thick samples. The results point to significant mechanical properties losses for Smile samples, however, the measured results are consistent with the requirements for dental applications that focus on aesthetic properties, classes 1 to 3. The measured results for optical properties justify and corroborate the results. gains induced by increasing the percentage of Y2O3.

The aim of this work was to obtain porous ceramic parts based on Zirconia stabilized with 5mol.% Yttria (5Y-PSZ), suitable for the infiltration with bioactive glasses, using 3D printed sacrificial polymeric molds. In a first step, honeycomb structured molds were designed with the SolidWorks® software and manufactured by 3D printing using polylactic acid filaments (PLA). These molds were filled with a ceramic mass composed of 5Y-PSZ nanoparticles containing 3wt% polymeric binder and consolidated under pressure of 10MPa and then sintered at 1200 °C-30 min the polymeric molds were consumed. The obtained hexagonal-shaped, porous 5Y-TZP bodies were infiltrated with the bioactive glass 45S5, calcium sodium phosphosilicate, at 1350 °C. The materials were characterized by their relative density, their phase composition by X-ray diffraction analysis, and their microstructure by scanning electron microscopy (SEM-EDS), besides their mechanical properties of hardness and fracture toughness. Pre-sintered 5Y-PSZ substrates exhibit relative density around 75%, and 90% after sintering and Bioglass infiltration. The samples' microstructure is composed of a 5Y-PSZ matrix of sub-micrometric zirconia grains with an average size of 1.0 mm, besides the secondary infiltrated glassy phase homogeneously distributed, with a Ca/P ratio of 1.7, close to the ideal proportion for hydroxyapatite formation. In conclusion, sacrificial molding is an interesting route to obtaining dense Y-PSZ/Bioglass 45S5 composite in a honeycomb format. El objetivo de este trabajo fue obtener piezas cerámicas porosas a base de Zirconia estabilizada con 5mol.% Yttria (5Y-PSZ), aptas para la infiltración con vidrios bioactivos, utilizando moldes poliméricos de sacrificio impresos en 3D. En un primer paso, se diseñaron moldes con estructura de panal con el software SolidWorks® y se fabricaron mediante impresión 3D utilizando filamentos de ácido poliláctico (PLA). Estos moldes se llenaron con una masa cerámica compuesta de nanopartículas de 5Y-PSZ que contenían un 3% en peso de aglutinante polimérico y se consolidaron a una presión de 10 MPa y luego se sinterizaron a 1200ºC-30 min. Se consumieron los moldes poliméricos. Los cuerpos de 5Y-TZP porosos de forma hexagonal obtenidos se infiltraron con el vidrio bioactivo 45S5, fosfosilicato de calcio y sodio, a 1350 °C. Los materiales se caracterizaron por su densidad relativa, su composición de fases por análisis de difracción de rayos X y su microestructura por microscopía electrónica de barrido (SEM-EDS), además de sus propiedades mecánicas de dureza y tenacidad a la fractura. Los sustratos presinterizados de 5Y-PSZ exhiben una densidad relativa de alrededor del 75% y el 90% después de la sinterización y la infiltración de Bioglass. La microestructura de las muestras está compuesta por una matriz 5Y-PSZ de granos de circonio submicrométrico con un tamaño promedio de 1.0 mm, además de la fase vítrea infiltrada secundaria distribuida homogéneamente, con una relación Ca / P de 1.7, cercana a la proporción ideal para formación de hidroxiapatita. En conclusión, el moldeo de sacrificio es una ruta interesante para obtener un compuesto denso Y-PSZ / Bioglass 45S5 en un formato de panal. O objetivo deste trabalho foi a obtenção de peças cerâmicas porosas à base de Zircônia estabilizada com 5mol.% de ítria (5Y-PSZ), adequadas para a infiltração com vidros bioativos, utilizando moldes poliméricos sacrificiais impressos em 3D. Em uma primeira etapa, os moldes estruturados em honeycombs foram projetados com o software SolidWorks® e fabricados por impressão 3D usando filamentos de ácido polilático (PLA). Esses moldes foram preenchidos com uma massa cerâmica composta por nanopartículas 5Y-PSZ contendo 3% em peso de ligante polimérico e consolidados sob pressão de 10MPa e então sinterizados a 1200 ° C-30 min os moldes poliméricos foram consumidos. Os corpos 5Y-TZP porosos de forma hexagonal obtidos foram infiltrados com o vidro bioativo 45S5, fosfosilicato de cálcio e sódio, a 1350 ° C. Os materiais foram caracterizados quanto à densidade relativa, composição de fases por difração de raios X e microestrutura por microscopia eletrônica de varredura (MEV-EDS), além de propriedades mecânicas de dureza e tenacidade à fratura. Substratos pré-sinterizados 5Y-PSZ exibem densidade relativa em torno de 75% e 90% após sinterização e infiltração de Biovidro. A microestrutura das amostras é composta por uma matriz 5Y-PSZ de grãos de zircônia submicrométricos com tamanho médio de 1,0 mm, além do infiltrado secundário fase vítrea distribuída homogeneamente, com relação Ca / P de 1,7, próxima à proporção ideal para formação de hidroxiapatita. Em conclusão, a moldagem sacrificial é uma rota interessante para a obtenção de compósito Y-PSZ / Bioglass 45S5 denso em formato de colmeia.

Objectives This study aimed to optimize the crystallization process and the microstructure of a new bioactive glass-ceramic (GC) previously developed by our research group to obtain machinable glass-ceramics. Methods Differential scanning calorimetry (DSC) analyses were conducted to explore the characteristic temperatures and construct a semi-quantitative nucleation curve. The GC specimens were characterized by X-ray diffraction (XRD) and Rietveld refinement. Their brittleness index (B) and machinability were characterized and compared with IPS e.max-CAD®. Their Young's modulus, fracture toughness, and hardness were assessed. Results We found that the maximum crystal nucleation rate temperature of this GC is ~470 °C. Treatments were designed based on the 1st DSC peak onset (570 °C), 1st peak offset (650 °C), and 2nd peak offset (705 °C) crystallization temperatures of lithium metasilicate (LS, LiSi2O3) and lithium disilicate (LS2, Li2Si2O5). Rietveld refinement indicated an increase in LS2 and a reduction in LS and amorphous phase for increased temperatures and longer treatment times. Their B values indicate good machinability compared with that of the control group based on statistical analyses. As expected, lower levels of LS2 increase the machinability regardless of the rotation speed adopted, leading to a greater depth of cut and reduced Edge Chipping Damage Depth (ECDD). Conclusion This bioactive GC with optimized microstructure presents high machinability. For treatment temperatures above 570 °C, the number of elongated LS2 crystals increases and decreases the amorphous phase content, which reduce the machinability of the GC, and should therefore be avoided. The best results were obtained using heat treatment at 570 °C, which produces LS crystals embedded in a glassy matrix (67%) with small contents of secondary phases.

The influence of Fe2O3 additions on the microstructure, mechanical properties and translucence of zirconia with 3 mol-% or 5 mol-% Y2O3 was evaluated. Samples were pressed with different thickness and sintered at 1475, 1500, 1550 and 1600°C for 2 h. Density, phases, microstructure, roughness, strength and translucency were analyzed. All samples showed densification greater than 99%. After sintering at 1600°C, the phase analysis revealed only tetragonal ZrO2 in samples with 3% Y2O3, while in samples with 5% Y2O3 the cubic ZrO2 phase was identified. Significant increase in the grain size was noted, when increasing the Y2O3 content from 3% to 5% from 0.8 µm to 2.3 µm for sintered samples at 1600°C. The strength was affected with Y2O3 content and no relevant influence of the Fe2O3 on density, microstructure or mechanical properties. Visible reflectance spectroscopy analyses, related to the CIELab scale, indicate variation in the contrast ratio as function of thickness of samples and coloring agent Fe2O3 content.

Ti-6Al-4V and TiAl-based alloys are widely used for fabricating the implantable orthopedic devices and automotive components, respectively. Ti6Si2B-based alloys are attractive for use in orthopedic components because their higher hardness, superior biocompatibility and corrosion resistance in simulated body fluid than Ti and Ti-6Al-4V alloy. Limited information on Ti6Si2B stability in Co-dopped 67Ti-22Si-11B alloys are available in literature. This work presents the effect of cobalt doping and milling time on microstructure and Vickers microhardness of 65Ti-2Co-22Si-11B and 61Ti-6Co-22Si-11B (at-%) alloys produced by spark plasma sintering at 1100 oC for 12min using 20MPa. Samples were characterized by X ray diffraction, scanning electron microscopy, energy dispersive spectrometry, laser particle size analysis, and Vickers microhardness. Sintered alloys with 2 and 6at-%Co indicated the major presence of Ti6Si2B and Ti5Si3 dissolving up to 2.7 and 4.2 at-%Co, respectively, besides the minor precipitates of CoTi2 (4.4-16.7at-%Si) and CoTi (4.6-4.7at-%Si). Vickers microhardness of the sintered 65Ti-2Co-22Si-11B and 61Ti-6Co-22Si-11B alloys were in the range of 950-1050 and 1050-1150HV, respectively. Although the increase from 2 to 6at-%Co has reduced the Ti6Si2B stability, the Co-rich phases increased their hardness values up to 1150HV (11.3GPa), which are superior than those of commercial Ti alloys used for joint orthopedic components and automotive rotating parts.

The objective of this work was the development and characterization of a ceramic composite based on (Ce,Y)-TZP/AlCeramic samples, 3Y-TZP (n = 40) and (Ce,Y)-TZP/AlAll sintered specimens presented nearly full densification. After the hydrothermal degradation tests, 3Y-TZP samples presented 16.4% of monoclinic (m)-ZrOThe composites (Ce,Y)-TZP/Al

In this study, an alumina-toughened zirconia composite (ATZ) was developed from mechanical alloyed nano-scale powder mixtures using low-sintering temperatures. A powder mixture, composed of 80 wt.% Y-TZP, ZrO2 (3 mol.% Y2O3), and 20 wt.% Al2O3, was prepared by mechanical alloying (MA) in a planetary ball mill under argon atmosphere, with milling times of up to 60 h, using a rotary speed of 200 rpm and a ball-to-powder weight ratio of 10:1. The mixtures were compacted at 100 MPa and sintered at 1400 °C—2 h. In the milled powders, the crystallite size of the ZrO2 matrix was reduced from 130 to 40 A, when increasing the milling time from 1 to 60 h. After sintering, the samples were characterized by its phase composition, microstructure, relative density, fracture toughness and biaxial flexural strength. Fully dense samples were obtained after sintering the powder-mixture milled for 60 h at 1400 °C—2 h. In comparison, the conventional powder-mixture achieved high densification only after sintering at 1600 °C—2 h. Sintered samples prepared with mechanical alloyed powder mixtures presented a fracture toughness (KIC) of 8.2 ± 0.3 MPa m1/2 and a bending strength of 880 ± 45 MPa, significantly higher compared to samples prepared from the conventional processed powder mixture sintered at 1600 °C—2 h, presenting a KIC of 6.7 ± 0.5 MPam1/2 and a bending strength of 697 ± 85 MPa. The improved mechanical strength of the composites prepared from mechanical alloyed powders is attributed to the increased sinterability of these powders, allowing full densification at 1400 °C, and also resulting in a reduction in the tetragonal ZrO2 grain size. Thus, a larger population of these grains is formed in the microstructure, increasing fracture toughness and strength by the tetragonal to monoclinic phase transformation toughening mechanism.

Made available in DSpace on 2019-10-06T16:48:11Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-01-02 Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ) This study evaluated the effect of the surface roughness parameters on the flexural strength of Yttria-partially stabilized zirconia, Y-TZP ceramics: ZrO2 (3 mol%) or ZrO2 (5 mol%), as function of different surface finishing protocols: polishing or alumina (Al2O3) blasting. Zirconia discs were manufactured by CAD/CAM prototyping and sintered at different temperatures. The specimens were characterized by X-ray diffraction, scanning electron microscopy, biaxial flexural strength test and 3D profilometry. In all specimens tetragonal Y2O3-ZrO2 was observed to be the main crystalline phase. The 3D profilometry indicated that alumina blasting of ZrO2 (3 mol%) increased the roughness Ra around 16–26 times as opposed to the polished surfaces, and approximately 38 times for ZrO2 (5 mol%) specimens when compared to the polished samples. The results of flexural strength indicate that groups of ZrO2 (3 mol% Y2O3) ceramics present a reduction of 21–23% from polished to alumina blasted specimens. In the group of ZrO2 (5 mol% Y2O3) ceramics, a flexural strength reduction of 37.5% was observed. A correlation between flexural strength, failure size and different roughness parameters: Ra (arithmetic average of the absolute values of the profile heights over the evaluation length), Rz (measure of the ordinates of the five highest peaks and the five deepest valleys along the specimen's length) and PV (mean values of peak and valley measured in the specimen space) is proposed and indicates that Rz and PV should not be neglected in a systematic evaluation of the surface roughness effect on the bulk mechanical properties of dental ceramics. Catholic University of Rio de Janeiro Department of Chemical and Materials Engineering PUC-Rio, Marques de São Vicente St 225, Gávea Fluminense Federal University / Faculty of Dentistry - Institute of Health of Nova Friburgo, Dr. Silvio Henrique Braune St, 22 - Downtown University of Toronto / Faculty of Dentistry, 124 Edward St #539 State University of Rio de Janeiro – Faculty of Technology, Presidente Dutra Highway, km 298 São Paulo State University - Faculty of Engineering of Guaratinguetá UNESP/FEG, Ariberto Pereira da Cunha Ave, 333 - Portal das Colinas São Paulo State University - Faculty of Engineering of Guaratinguetá UNESP/FEG, Ariberto Pereira da Cunha Ave, 333 - Portal das Colinas FAPERJ: E26-201.476/2014

Ceramic composites are developed with the aim of improving the properties of single phase materials, adapting it to the demands of their applications. In this work, composite ceramics with an unidirectional functional gradient based on Al2O3 reinforced with 3, 5, 10 and 15 wt-% of Y-TZP (Yttria stabilized tetragonal zirconia polycrystals) nano-sized particles were prepared, using multilayer deposition and uniaxial compaction. The composites were characterized by their relative density, microstructure, phase composition, hardness and fracture toughness. The results showed the presence of α-Al2O3 and t-ZrO2 as crystalline phases and relative density near to 98%. The hardness varied according to the indented region varying between 1750 and 1540 (HV), for layers containing 3 and 15 wt-% of Y-TZP, respectively. Fracture toughness of the composite layers is also sensitive to the increasing ZrO2 content, presenting average values of 3.2 to 4.8 MPa.m1/2, indicating the influence of toughening mechanisms such as the t → m ZrO2 phase transformation and compressive residual stresses between the α-Al2O3 matrix and the reinforcing t-ZrO2 particles, generated by their thermal mismatch.

In this work three dental ceramics were characterized according to ISO 6872: yttria-stabilized zirconia (ZrO2-Y2O3), lithium disilicate (Li2Si2O5) and the spinel-zirconia composite (MgAl2O4-ZrO2). The zirconia ceramic and the zirconia-spinel composite were sintered at 1600°C-2h, while the lithium disilicate was thermally treated at 820°C-20min. These materials were characterized by relative density, X-ray diffraction, scanning electron microscopy, hardness, fracture toughness, chemical solubility and cytotoxicity. The XRD results showed for the stabilized zirconia only the tetragonal phase of ZrO2, and to the composite only the phase MgAl2O4, Li2Si2O5 was the only phase to lithium disilicate. Relative density results showed that the zirconia and the lithium disilicate showed high densification (> 99.5%) and the composite had a relative density of 75% (10% composite doped with ZrO2) and 90% (50% doped with ZrO2). Hardness and toughness showed 450HV and 3.2MPa.m1/2 to ZrO2-MgAl2O4 composites, 525HV and 1.8MPam1/2 to lithium disilicate and 1280HV and 8.0MPa.m1/2 to zirconia. The materials evaluated showed chemical solubility 2 and the results of cytotoxicity tests indicated cell viability of the samples near 100% for all the materials, showing good chemical stability and potential for dental applications.

This study aims to evaluate the effects of sintering parameters in crystalline phases, microstructure and mechanical properties of composites obtained through the Al2O3-TiO2 ceramic system. Cylindrical specimens, containing molar ratio of 3 Al2O3: 1 TiO2, were uniaxially pressed at 100 MPa. The applied sintering parameters were varied in five distinct temperature ranges (1300°C, 1400°C, 1500°C, 1575°C or 1600°C) for 2h and 1600°C for 10h. After sintering, samples were characterized by relative density, X-ray diffraction, scanning electron microscopy and mechanical properties (hardness and fracture toughness). After sintering the results point to a microstructure with grains near to 2.5mm, independent of the present phases and crystalline phases composed of: Al2O3 rhombohedral, TiO2 tetragonal e Al2TiO5 orthorhombic. The specimens sintered at 1600°C-10h feature densification 30% higher them the ones sintered at 1300°C-2h, reaching a density higher than 85% of theoretical density. The composite presents hardness higher than 1000HV and fracture toughness upper than 2.2MPam1/2. The better results for the mechanical properties were found in the composites sintered at 1600°C-10h, that showed a bigger relative density than all analyzed specimens, and only phases of Al2O3 and Al2TiO5 could be found, what means that all TiO2 was consumed in the sintering of the new composite.

The objective of this work was the development of Al2O3-ZrO2 ceramic composites using recycled-source of ZrO2(Y2O3). Al2O3 powder was mixed with different proportions of ZrO2(Y2O3) arising from pre-sintered blocks used in dental prostheses manufacturing. The mixtures containing 3wt% to 15wt% ZrO2(Y2O3) were uniaxially pressed at 80MPa and sintered at 1600°C-2h. Raw materials and sintered samples were characterized by X-ray diffraction, scanning electron microscopy (SEM), relative density, hardness and fracture toughness. The results of X-ray diffraction showed α-Al2O3 and tetragonal-ZrO2 as crystalline phases after sintering. Furthermore, the relative density in all compositions was higher than 95%. The samples presented Vickers hardness and fracture toughness higher than 1300HV and 3.5MPa. m1/2, respectively.

Made available in DSpace on 2020-12-12T00:55:05Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-02-01 Financiadora de Estudos e Projetos Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ) In this work bio-composites were obtained by infiltrating porous alumina–titania (Al2O3–TiO2) substrates with a lanthania-rich (La2O3) glass. Al2O3–TiO2 substrates were fabricated using high-energy milled powder mixtures of two different compositions with molar ratios of 3:1 and 1:1, uniaxial compaction under 100 MPa and sintering at 1300 °C - 2 h or 1400 °C - 2 h. The high energy milling process of the powders resulted in homogeneous, extremely fine mixtures. For comparison, as-received Al2O3 and TiO2 powders were also mixed at a proportion of 3:1 and sintered at 1600 °C - 2 h. The sintered substrates presented α-Al2O3 and β-Al2TiO5 (aluminium titanate) as crystal phases and relative densities ranging between 65.5 ± 2% and 69.4 ± 1.2% of the theoretical density. These porous substrates were infiltrated with a lanthania containing glass at a temperature of 1140°C-2h. The resulting ceramic composites exhibited high density, varying between 94 to 99% of the theoretical density, Vickers hardness ranging between 895 ± 14 HV and 1036 ± 33 HV, fracture strength ranging between 218 ± 28 MPa and 254 ± 18 MPa and a fracture toughness (KC) higher than 2.6 MPam1/2. Phase analysis of the infiltrated substrates by X-ray diffraction indicated the decomposition of aluminium titanate into alumina and titania besides the formation of lanthanum borosilicate, LaBSiO5. In addition, all compositions studied presented non-cytotoxic behaviour and low chemical solubility, inferior to 75 μg/cm2. Universidade do Estado do Rio de Janeiro - UERJ Faculdade de Tecnologia de Resende, Rod.Presidente Dutra, Km 298 Universidade de São Paulo-USP Escola de Engenharia de Lorena Departamento de Engenharia de Materiais Polo Urbo Industrial, Gleba AI-6 Universidade Federal de Alfenas-UNIFAL Instituto de Ciência e Tecnologia, Rod. José Aurélio Vilela, 11999 Universidade Estadual Paulista - Unesp Faculdade de Engenharia de Guaratinguetá, Av. Ariberto Cunha, 333 Universidade Federal de São João Del-Rei - UFSJ Campus Santo Antônio, Pça Frei Orlando 170 Universidade Estadual Paulista - Unesp Faculdade de Engenharia de Guaratinguetá, Av. Ariberto Cunha, 333 Financiadora de Estudos e Projetos: 01.10.0805-00 CNPq: 311119/2017-4 CNPq: 551048/2011-5 FAPERJ: E26-202.997/2017

Objectives The objective of this work was the development and characterization of a ceramic composite based on (Ce,Y)-TZP/Al2O3 aiming an application on dental implants, comparing it with conventional monolithic 3Y-TZP ceramics, currently used for the same type of application. Methods Ceramic samples, 3Y-TZP (n = 40) and (Ce,Y)-TZP/Al2O3 (n = 40), were sintered at 1500 °C - 2h and characterized by relative density, X-Ray diffraction (XRD) and microstructure. Then, the samples of both materials were divided into two groups: 1) samples with original (as sintered) surfaces; 2) samples with conditioned, polished, surfaces. All samples were submitted to hydrothermal degradation tests, on an autoclave (134 °C - 2 bar), for 10 h in artificial saliva. The degraded samples were characterized by XRD and the polished group were also characterized by their elastic moduli, Vickers hardness and fracture toughness (Vickers indentation method). Both groups were also submitted to a flexural strength test, 3B–P testing, for which the data were interpreted using Weibull statistics. Results All sintered specimens presented nearly full densification. After the hydrothermal degradation tests, 3Y-TZP samples presented 16.4% of monoclinic (m)-ZrO2 phase while the composite samples withheld 100% of tetragonal (t)-ZrO2 phase. Both materials presented equiaxial ZrO2 grains with an average size of 0.48 ± 0.17 μm and 0.75 ± 0.22 μm, respectively, for the monolithic and composite ceramics. In the composites, is observed the presence of well distributed Al2O3 grains on the ZrO2 matrix, in two distinct morphologies: equiaxial grains and platelets. The composites (Ce,Y)-TZP/Al2O3 presented average values of elastic moduli, Vickers hardness and fracture toughness of 228.3 ± 6.5 GPa, 1427 ± 46 HV e 11.3 ± 0.4 MPa m1/2, respectively. An inversely proportional relationship is observed between the roughness and the bending strength, since the 3Y-TZP samples presented a average strength of 860.7 ± 81 MPa (as-sintered) and 965.4 ± 93 MPa (polished) while the (Ce,Y)-TZP/Al2O3 composites presented average strength of 810.6 ± 147 MPa (as-sintered) and 952.6 ± 88 MPa (polished). Conclusions The composites (Ce,Y)-TZP/Al2O3 showed high resistance to degradation in saliva and adequate properties for use as dental implants. Values of flexural strength (>950 MPa) and Weibull modulus (m > 10) were similar to the conventional 3Y-TZP ceramics. Moreover, its hardness, elastic modulus and fracture toughness were higher than those obtained for 3Y-TZP. The expressive values of KIC obtained for (Ce,Y)-TZP/Al2O3 composites are results of association of different toughening mechanisms acting simultaneously in the material.

Made available in DSpace on 2020-12-12T02:24:49Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-09-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ) Objectives: The aim of this study was to evaluate the effect of hydrothermal aging on the mechanical properties and translucency of dental zirconia with different levels of translucency. Methods: Three different types of dental yttria-stabilized zirconia were used: 3Y-TZP (ZrO2 - 3 mol.% Y2O3) of medium opacity (designated Z3OP), 3Y-TZP of medium translucency (Z3MT), and 5Y-PSZ (ZrO2 - 5 mol.% Y2O3) of high translucency (Z5HT). A total of 120 specimens were sintered (n = 40 specimens/group). The control group (sintered→polished→heat-treated) and the aged group (sintered→polished→heat-treated→hydrothermally degraded at 134 °C, 2 bar, 5h) were characterized by relative density, quantitative phase analysis by X-ray diffraction using the Rietveld method, microstructural analysis by scanning electron microscopy, surface roughness and translucency. All groups were submitted to a biaxial flexural strength test. Data analysis using Kruskal-Wallis, Nemenyi (p-value = 0.05), and Weibull statistics were used. Results: All sintered specimens presented full densification. After aging, an increase of the m-ZrO2 phase content was observed for the Z3OP group. On the other hand, Z3MT and Z5HT did not show any m-ZrO2 phase, indicating resistance to the hydrothermal degradation. Smaller grains were observed in the Z3MT group in relation to Z3OP group and the Z5HT group presented a bimodal grain distribution, where the largest grains were associated to cubic ZrO2. Z3OP exhibited a slight increase in roughness as a function of degradation, while the roughness remained statistically stable in the other groups. Translucency was little influenced by degradation, but considerably affected by increasing thickness. The Z5HT samples were the group with the highest translucency among the control groups. Z3OP exhibited the highest flexural strength, while being the most susceptible to hydrothermal degradation. The lowest values were presented by Z5HT in all groups, due to the high concentration of c-ZrO2 grains. Conclusion: Hydrothermal aging is less critical to the flexural strength of zirconia-based materials than the materials’ composition and microstructure. Z5HT zirconia showed the highest translucency, however the measured difference is not visually perceptible. Z5HT was considered the most resistant to hydrothermal degradation. Fluminense Federal University Faculty of Dentistry Institute of Health of Nova Friburgo, Dr. Silvio Henrique Braune St, 22 - Downtown Pontical Catholic University of Rio de Janeiro Department of Chemical and Materials Engineering PUC-Rio, Marques de São Vicente St 225, Gávea University of Toronto Faculty of Dentistry, 124 Edward St #539 State University of Rio de Janeiro Faculty of Technology, Presidente Dutra Highway, Km 298 São Paulo State University Faculty of Engineering of Guaratinguetá UNESP/FEG, Ariberto Pereira da Cunha Ave, 333 - Portal Das Colinas São Paulo State University Faculty of Engineering of Guaratinguetá UNESP/FEG, Ariberto Pereira da Cunha Ave, 333 - Portal Das Colinas CNPq: 308684/2013-3/311119/2017-4 FAPERJ: E-26-201.476/2014

Made available in DSpace on 2019-10-06T17:12:39Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-10-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ) Objectives: The properties of lithium-silicate dental glass-ceramics are very sensitive to heat treatments which are conducted after CAD/CAM (Computer Aided Design/Computer Aided Machining) processing. In particular, temperature variations inside the furnace chamber which may occur between different models of furnaces may result in altered mechanical properties of these materials. In this work, the effect of thermal treatment parameters on the transformation of lithium metasilicate (Li2SiO3) into lithium disilicate (Li2Si2O5) and on the resulting mechanical properties has been investigated. Methods: Lithium metasilicate samples. containing 59 vol% of amorphous phase, were thermal treated under vacuum at 820 °C for up to 9 min or at 840 °C for 7min (as control group). The samples were characterized by X-ray diffraction analysis using the Rietveld refinement and scanning electron microscopy. Hardness and fracture toughness (n = 30 indentations/group) were evaluated by the Vickers indentation technique. The elastic properties were measured by the Impulse Excitation Technique and the flexural strength (n = 15/group) was measured using the piston-on-three-ball (P–3B) testing assembly. Complementary Weibull statistic were conducted as statistical analysis. Results: The results indicate a progressive reduction of the Li2SiO3 phase with increasing isothermal holding time at 820 °C until the conversion into Li2Si2O5, is completed for treatments longer than 7 min. A complete transformation of Li2SiO3 into Li2Si2O5 has also been observed for the control group of samples treated at 840 °C for 7min. Samples of the control group exhibited hardness, fracture toughness, Young's modulus and Poisson ratio 5.76 ± 0.17 GPa, 1.60 ± 0.03 MPa m1/2, 100.3 GPa e 0.21, respectively. The reduction of the thermal treatment temperature to 820 °C reduced the fracture toughness and the Young's modulus between 5-10%. Furthermore, the fracture strength was significantly reduced by approximately 71%, because of the lower amount of elongated Li2Si2O5 grains and higher amount of residual amorphous phase. Conclusion: In general, the glass-ceramic material containing residual amorphous phase associated with various crystalline phases, presented a reduction of its mechanical properties in relation to the lithium disilicate glass-ceramic. The reasons for these differences in the mechanical behavior are discussed by analyzing the influences of different phenomena such as thermal expansion anisotropy, residual stresses, amorphous phase content and microstructure on the properties. UNESP/FEG Universidade Estadual Paulista Faculdade de Engenharia de Guaratinguetá, Av. Ariberto Pereira da Cunha, 333, Portal das Colinas USP/EEL Universidade de São Paulo Escola de Engenharia de Lorena Campus II, Polo Urbo Industrial Gleba AI6, s/n UERJ/FAT Universidade do Estado do Rio de Janeiro Faculdade de Tecnologia, Rod. Presidente Dutra, km 298 UFSJ Universidade Federal de São João Del´Rei, Pça Frei Orlando 170 UNESP/FEG Universidade Estadual Paulista Faculdade de Engenharia de Guaratinguetá, Av. Ariberto Pereira da Cunha, 333, Portal das Colinas CNPq: 308684/2013-3 CNPq: 3311119/2017-4 FAPERJ: E-26-201.476/2014

This work reports on effect of zinc and milling time on microstructure and Vickers hardness of mechanically alloyed and spark plasma sintered (66,7-x)Ti-xZn-22,2Si-11,1B alloys (at.-%, with x = 2 and 6 at.-%). Ball milling at different times (20, 60, 180 and 300 min) was performed under argon atmosphere in a planetary ball mill from these elemental powder mixtures. Cylinder bodies with 10 mm diameter were consolidated by spark plasma sintering (1100 °C, 12 min, 20 MPa) under argon atmosphere. As-milled powders and sintered Ti-Zn-Si-B samples were evaluated by X-ray diffraction, scanning electron microscopy, energy dispersive spectrometry, laser diffraction particle size analysis, and Vickers hardness tests. It was noted a similar behavior during ball milling of Ti-Zn-Si-B powder mixtures. Only the α-Ti and Si peaks were indexed in XRD patterns of Ti-Zn-Si-B powders milled for 300 min. Rietveld refining indicated that the amount of amorphous structures has increased during milling up to 300 min, which was more pronounced for the Ti-6Zn-22Si-11B powders. The particle sizes of the Ti-2Zn-22Si-11B and Ti-6Zn-22Si-11B powder mixtures increased during milling from 94 (20 min) to 156 (300 min) μm and from 101 (20 min) to 136 (300 min) μm, respectively. Coherently, the average specific surface area of powder particles was continuously reduced during milling. Despite the adopted parameters, the SPS process produced dense Ti-xZn-22Si-11B (x = 2 and 6 at.-%) alloys with 98% from their theoretical specific mass. Regardless of milling time, the Ti6Si2B formation was inhibited in microstructure of the spark plasma sintered Ti-6Zn-22Si-11B alloy previously milled for longer times. EDS analysis indicated that the Ti6Si2B phase dissolved close to 1.8 at.-% Zn. Beside the TiB and Ti5Si3, the Ti2Zn and Ti3Zn (not explored) phases were also found in microstructure of sintered Ti-Zn-Si-B alloys. The Ti-2Zn-22Si-11B alloy presented average Vickers hardness values higher than 1050 HV whereas the Ti-6Zn-22Si-11B alloy varied between 970 and 1036 HV, which could be associated with the Ti6Si2B formation.

Robocasting, também conhecido como Direct Ink Writing, é uma técnica de fabricação aditiva (AM), que inclui extração direta de sistemas coloidais, que consiste na exposição de camadas e um controlador controlado por computador de uma mídia altamente concentrada nesta extrusão. Este artigo apresenta uma visão geral das contribuições e desafios no desenvolvimento de biomateriais cerâmicos tridimensionais (3D) por esse método de impressão. O estado da arte em diferentes biocerâmicas como alumina, zircônia, fosfato de vidro, vidro / vitrocerâmica e compostos é avaliado e discutido em relação a suas aplicações e comportamento biológico, em uma pesquisa que produziu desde uma produção de próteses dentárias personalizadas a biofabricantes 3D humanos tecidos.Embora o robocasting represente uma interrupção na fabricação de estruturas porosas, como os andaimes para a Engenharia de Tecidos (TE), muitas vantagens ainda são necessárias, mas ainda são divulgadas, essa técnica já está usando a utilização de peças densas. Assim, são necessárias estratégias para a fabricação de biocerâmica densificada, com o objetivo de ampliar as possibilidades dessa técnica de AM. As vantagens e desvantagens e também perspectivas futuras da aplicação do robocasting no processamento biocerâmico também são exploradas.