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A nanosized magnesium substituted beta-tricalcium phosphate (Mg:β-TCP) was synthesized by an aqueous precipitation method, at room temperature, in one single step. In the present study, the novel and stable Mg:β-TCP resulted in a crystalline and spherical nanoparticles (diameter of approximately 20 nm) with mesoporous structures and a high specific surface area (about 574 m2/g). These special characteristics make this novel crystalline mesoporous Mg: β-TCP nanoparticles ideal candidates for drug delivery system and a promising non-viral vector for gene therapy.

Alumina-mullite composites with low shrinkage can be made by reaction bond using mixtures of alumina, aluminum and silicon carbide. In this work, an alternative route is used to produce alumina composites with low shrinkage. Here alumina samples containing additions of 10 and 20 wt% of a preceramic polymer were warm-pressed and treated in the range of 900 -1500°C to produce alumina based composites. The obtained composites were analyzed by linear shrinkage and compared to pure alumina samples sintered at the same temperature range. It were also evaluated the density variation and crystalline phases formed during heat treatment of alumina composites. Results showed that alumina-silicon oxycarbide and alumina-mullite composites were obtained with lower shrinkage than pure alumina samples.

In the last decade, a variety of methods for fabrication of three-dimensional biomimetic scaffolds based on hydrogels have been developed for tissue engineering. However, many methods require the use of catalysts which compromises the biocompatibility of the scaffolds. The electrochemical polymerization (ECP) of acrylic monomers has received an increased attention in recent years due to its versatility in the production of highly biocompatible coatings for the electrodes used in medical devices. The main aim of this work was the use of ECP as scaffold fabrication technique to produce highly porous poly(N-isopropylacrylamide) (PNIPAM)/hydroxyapatite (HAp) composite for bone tissue regeneration. The prepared PNIPAM-HAp porous scaffolds were characterized by SEM, FTIR, water swelling, porosity measurements and X-ray diffraction (XRD) techniques. FTIR indicates that ECP promotes a successful conversion of NIPAM to PNIPAM. The water swelling and porosity were shown to be controlled by the HAp content in PNIPAM-HAp scaffolds. The PNIPAM-HAp scaffolds exhibited no cytotoxicity to MG63 cells, showing that ECP are potentially useful for the production of PNIPAM-HAp scaffolds. To address the osteomyelitis, a significant complication in orthopedic surgeries, PNIPAM-HAp scaffolds were loaded with the antibiotic oxacillin. The oxacillin release and the bacterial killing activity of the released oxacillin from PNIPAM-HAp against S. aureus and P. aeruginosa were demonstrated. These observations demonstrate that ECP are promising technique for the production of non-toxic, biocompatible PNIPAM-HAp scaffolds for tissue engineering.

Titanium alloys are widely used as implants in orthopedics and dentistry due to their properties such as high strength, corrosion resistance, biocompatibility and good fatigue resistance. Alloys composed of non-toxic elements, like Nb and Zr, provide lowest Young’s modulus with values near to human bone modulus. The goal of this work was to study the effect of NbH particle size and cooling type on the microstructure, phase composition and microhardness of Ti-20Nb-20Zr alloy. The powders were produced by hydrogenation method. Two different powders of NbH were prepared: powders comminuted (C) and comminuted followed by milling (C+M). After, the alloy powders were milling and homogenizated for 6 h / 300 rpm and sintered at 1300 °C / 3h followed furnace cooling. Afterward, the specimens were treated at 1000 °C / 1 h and cooling in air and water. The samples were characterized by XRD, SEM and Vickers microhardness. The results showed that the alloy is classified as α + β. Vickers microhardness of Ti-20Nb-20Zr ranged between 680-700 and 540-600 HV from alloys prepared with NbH-comminuted and NbH comminuted + milled, respectively. Results indicated that NbH agglomerate behave as barriers for the sintering process of the alloy.

A novel class of upconversion luminescent nanocrystals of Yb/Tm:calcium deficient hydroxyapatite were synthesized by co-precipitation method in aqueous solution (pH adjusted to 6) and specially heat-treated with microwave radiation at different temperatures (from 900 °C to 1000 °C) and times (2–10 min) to produce small nanocrystals of Yb/Tm:β-tricalcium phosphate (β-TCP). As a result, we report for the first time, a single-phase Yb/Tm-doped β-TCP nanocrystals with a mean crystallite size of 55.3 nm. This material has an efficient visible luminescence from the 1G4 (blue emission) and 3F2 (red emission) and near infrared emission from the 3H4 excited states of Tm3+ induced by the Yb3+→Tm3+ energy transfer under laser excitation (Yb3+) at 972 nm. This β-TCP activated by Yb3+ and Tm3+ ions constitutes a new nano-fluoroprobe that can be used as optical contrast agents, affording high resolution and sensitivity for visible-near infrared applications.

The effects of the heat treatment on the phase transformations, microstructures and mechanical properties of Ti-8.5Nb-4.5Ta-13Zr alloy were studies in this work. Some of the starting powder were obtained by hydrogenation method and homogenized with metallic tantalum in a high-energy planetary mill. The samples were compacted in a uniaxial and cold isostatic presses and then, sintered at 1150 °C for 10 hours under high vacuum. The heat treatments were carried out at the same sintering temperature, above the α / β transus, at different cooling rates such as furnace cooling, air cooling and water quenching. The sintered samples were characterized using the Archimedes density method, X-ray diffraction (XRD) and scanning electron microscopy (SEM). The microhardness was measured using the Vickers indentation (ASTM E384-11 Standard). It was shown that the microstructure of Ti-8.5Nb-4.5Ta-13Zr alloy consists of beta-phase matrix and alpha-phase region of two structures: equiaxed and needle-like grains also known as Widmanstätten structure. The precipitation of the alpha-phase in the beta-phase matrix led to an increase in Vickers microhardness of the alloy which was furnace cooled. Moreover, a few remaining pores were still found and density above 98% was achieved.

Europium-doped hydroxyapatite (HA), beta-tricalcium phosphate (β-TCP) and biphasic phosphate nanopowders were synthesized by co-precipitation method and their crystal structures and fluorescence properties were investigated depending on the pH of the starting solution. In the range of pH 6–10, HA and β-TCP phases coexist. The β-TCP proportion increased as the pH of the solution decreased, while HA yields decreased. At pH below 6, monophasic β-TCP powder was obtained after thermal treatment. In particular, HA and β-TCP can be used as luminescent materials when activated by Eu 3+ ions in substitution of Ca 2+ ions. Herein, the Eu 3+ ions doped HA and β-TCP phase composition were analyzed in order to investigate the fluorescence emission of the HA, β-TCP and biphasic compounds. Eu-doped HA exhibited a red-orange emission at 575 nm with several minor peaks at 610–640 nm, while Eu-doped β-TCP had an unexpected strong red emission at 610–620 nm and a secondary band at 590–600 nm. In fact, the Eu:β-TCP integrated emission area is almost 20-fold higher than Eu:HA for the same europium ion concentration. These results demonstrate the potential of Eu:β-TCP as biomarker for medical applications, as drug release and targeting based on their luminescent properties.

This paper describes a study of shrinkage behavior in the liquid phase sintering of silicon carbide, SiC, using eutectic mixtures of Al 2 O 3 +Dy 2 O 3 and Al 2 O 3 +Yb 2 O 3 as liquid-forming additives. A volume fraction 10% of these mixtures was added to the SiC and homogenized in an attrition mill. Sintering was performed in a horizontal dilatometer at 1800 °C for 60 min, applying heating rates of 10, 20 and 30 °C/min. The results indicate that these heating rates affected neither shrinkage nor microstructure, from the standpoint of the complete sintering cycle. However, significant differences occurred during the non-isothermal sintering stage, leading to very different shrinkage results as a function of the heating rate. Higher heating rates produced lower shrinkage, and the work of final shrinkage occurred during the isothermal stage.

The aim of this study was to evaluate the effect of Y2O3:Al2O3 additives and sintering temperature on thermal shock resistance of silicon carbide sintered via liquid phase. Silicon carbide samples containing 10 mol% Y2O3:Al2O3 (1:3 and 1:4) were prepared, compacted and sintered at 1750, 1850 and 1950 °C in a graphite resistive furnace. Thermal shock resistance was evaluated after each thermal cycle performed at 600, 750 and 900 °C followed by abrupt cooling in water. Samples with two Y2O3:Al2O3 proportions did not show major differences when sintered at the same temperature, though, rising the sintering temperature improves Y2O3:Al2O3 modified-SiC thermal shock resistance.

In this work, we present the synthesis, characterization and the luminescence properties of Ca10(PO4)6(OH)2 (hydroxyapatite/HAp) nanocrystals doped with europium trivalent ions. The most important processes that lead to europium emissions in the visible region were identified. Eu:HAp nanopowder excited at 394 nm (or 460 nm) exhibits several emissions: (i) weak emissions at 579 nm, 592 nm and 616 nm due to the 5D0 → 7F0, 5D0 → 7F1 and 5D0 → 7F2 transitions, respectively, with europium ion occupying site I in hydroxyapatite structure and (ii) strong emissions due to the 5D0 → 7F0 (574 nm), 5D0 → 7F1 (602 nm) and 5D0 → 7F2 (610–630 nm) transitions, when Eu3+ is occupying site II. The emission spectrum and the time-resolved luminescence analysis showed that the HAp nanocrystals (nanopowder) thermally treated at temperature (T) between 500 and 800 °C have a change in the initial Eu3+ site distribution of 100 % of Eu3+ at site I to a more stable one where the majority of europium ions are at site II: 30% remains at site I and 70% migrates to site II. In addition, an enhancement of the Eu3+ emission intensity is observed due to the increasing crystallite size. A time-resolved luminescence investigation using a short pulse laser excitation at 460 nm was employed to measure the luminescence decays and to determine the most important mechanisms involved in the deexcitation process of 5D0 excited state of Eu3+, where it is seen a fast (2.9 μs) energy transfer from Eu3+- site I (donor) to Eu3+- site II (acceptor) in the thermally treated nanopowders with T > 500 °C. The initial presence of 100% of Eu3+ at site I in the synthesized nanocrystals is gradually modified by the thermal treatments with temperatures above 500 °C by thermal activation of Ca2+ vacancy (the charge compensator) diffusion through the HAp lattice, which propitiates the Ca2+- vacancies and Eu3+ ions to exchange positions in the lattice. By this thermal activated mechanism, Eu3+ ion migrates through the lattice until get the final distribution of 30% at site I and 70% at site II. As a result, the complete description of the Eu3+ (5D0) decay and the energy transfer process from Eu3+ (site I) → Eu3+ (site II) were proposed.

Hydroxyapatite (HA) doped with europium (HAEu) offers the advantage of making the hydroxyapatite a fluorescent biomarker, allowing their imaging through emissionin vivoandin vitrotests. Several authors had been based their studies about europium site occupation (CaI and CaII) in hydroxyapatite by the lanthanide ion luminescence, verifying the influence of the method of synthesis and concentration of the dopant ion. In this study HA nanoparticles doped with 1.4 mol% of trivalent europium were synthesized by co-precipitation method and thermal treated at different temperatures (600°C and 1200°C). A careful evaluation of the influence of the excitation wavelength of europium luminescence in the HAEu was performed and it has been verified that both the characteristics transitions of europium, at CaI and CaII sites, and the luminescent intensity are dependent on the excitation wavelength. The non-observance of this fact can lead to erroneous conclusions about the site occupation of europium in hydroxyapatites.

Ti-13Nb-13Zr alloy produced via powder metallurgy was submitted to heat treatment under various conditions and the effects on microstructure and elastic modulus were investigated. Heat treatment was performed using temperatures above and below α/β transus combined with different cooling rates – furnace cooling and water quenching. Microstructure and phases were analyzed employing scanning electron microscopy and X-ray diffraction. Elastic Modulus was determined using a dynamic mechanical analyzer (DMA). The results indicated that α phase precipitation and elastic modulus values increased after heat treatment performed using temperature below α/β transus. However, when it was performed above α/β transus and using higher cooling rate, a decrease in elastic modulus was observed despite higher α phase precipitation, indicating that the microstructural modifications observed via SEM, due to the presence of martensitic α phase, influenced on elastic modulus values.

Samples of SiC+10 vol%(Al 2 O 3 +Dy 2 O 3 ) and SiC+10 vol%(Al 2 O 3 +Yb 2 O 3 ) mixtures were obtained by cold isostatic pressing and sintered for one hour in a dilatometer at 1800 °C and 1900 °C, applying heating rates of 10, 20 and 30 °C/min. The results of the complete sintering cycle indicated that the heating rates do not significantly influence the shrinkage, but that temperature and total sintering time may be relevant factors. The compacts sintered at 1900 °C shrank on average 9% more than those sintered at 1800 °C, and it was found that the sintering time can be reduced by 40–50% at faster heating rates. The maximum shrinkage rates occurred at temperatures lower than those of the sintering thresholds for the two mixtures, two temperatures and three heating rates. It was also found that after formation of the liquid, the mechanisms of particle rearrangement and solution-precipitation were not as fast as reported in the literature, even at high heating rates, for example 30 °C/min, but they are responsible for much of the shrinkage occurring throughout the sintering cycle.

Commercial polysilsesquioxanes filled with silicon and aluminum particles were prepared in the form of a thin sheet by tape casting and pyrolyzed in nitrogen atmosphere at various temperatures up to 1500 °C. Two silicone resins with different carbon content were used to prepare slurries containing 30 vol% of Si and Al as filler with volume ratios of 1:1 and 1:3. The crystalline phases that formed in the polymer derived ceramic (PDC) substrates pyrolyzed at different temperatures were identified using x-ray diffraction patterns. Substrates pyrolyzed at 1500 °C were characterized with respect to their density, total open porosity and thermal expansion coefficient. The resulting microstructures were examined using scanning and transmission electron microscopy. The main crystalline phases in substrates pyrolyzed at 1000 °C were identified as Si, β-SiC and AlN. These gradually converted to β-SiC/SiAlON composites at 1500 °C. The higher carbon content favored formation of the phases β-SiC and AlN. The β-SiAlON phase predominated in substrates with higher Si content while SiALON polytypoids were more significant in substrates with higher Al content. The 21R (SiAl 6 O 2 N 6 ), 12H (SiAl 5 O 2 N 5 ) and 15R (SiAl 4 O 2 N 4 ) SiAlON polytypoids were observed in all the samples and were identified by high resolution electron microscopy (HREM) in samples pyrolyzed at 1500 °C.

The effects of adding polysiloxane (polymethylsilsesquioxane) on the sintering behavior, microstructure and hardness of alumina ceramics have been studied. The sintering kinetics of cold-pressed specimens was studied by dilatometry. Polymer sintering aid was used for alumina based ceramics sintered at 1650o C. The sintered materials were characterized using helium picnometry, x-ray diffraction analysis, scanning electron microscopy, transmission electron microscopy, energy dispersive x-ray spectrometry and Vickers indentation. The addition of polymethylsilsesquioxane yielded alumina/Si2Al4O4N4composites. The sintering studies in nitrogen atmosphere (1650 °C/1h) revealed that the highest densities were obtained for specimens with 1wt% PMS. The materials prepared with ceramic polymer precursors had higher hardness than the standard specimen. The preparation of ceramic composites using small amounts of polymer precursors is suited for alumina based ceramics. The processing route being simple, it has the potential to enable the manufacture of complex shaped pieces.

Porous metallic structures have been developed to mimic the natural bone architecture, having interconnected porosity, disposing enough room to cell migration, anchoring, vascularization, nourishing and proliferation of new bone tissue. Research involving porous titanium has been done with purpose to achieve desirable porosity and increasing of bone-implant bond strength interface. Samples of titanium were prepared by powder metallurgy (PM) with addition of different natural polymers (cornstarch, rice starch, potato starch and gelatin) at proportion of 16wt%. In aqueous solution the hydrogenated metallic powder (TiH2) and the polymer were mixed, homogenized and frozen in molds near net shape. The water was removed in kiln and the polymer by thermal treatment in air- (350°C/1h) before sintering in high-vacuum (1300°C/1h). The biological evaluation was performed by in vivo test in rabbits. Histological analysis was performed by scanning electron microscopy (SEM), energy dispersive spectroscopy (SEM-EDS) and fluorescence microscopy (FM). The processing methodologies using natural low cost additives propitiate the production of porous metallic implants in a simplified manner, with different porosities, proper porosity degree (40%), distribution, and maximum pore size of 80 μm to 220 μm depending of natural polymer used. The samples added with rice starch, presented the most similar structure organization when compared to the bone tissue microstructure organization of the trabecular bone. All implants osseointegrated, the pore microarchitecture and its interconnected network allowed bone ingrowth in all pore sizes, but the continuous bone maturation occurred in pores bigger than 80 μm.

PURPOSE To examine the biologic response to titanium implant surfaces treated with a neodymium:yttrium-aluminum-garnet laser. MATERIALS AND METHODS Sixty mini-implants made of grade 2 titanium were placed in the femora of 30 Wistar rats. Thirty implants had a machined surface and the other 30 had surfaces that were roughened by laser treatment. The animals were subdivided into three groups according to bone repair periods of 15, 30, and 60 days. The samples were observed under light and electron scanning microscopes and analyzed with the Student t test. RESULTS Formation of new bone trabeculae toward the surface was apparent for the laser-treated implants at 15 days. Thin layers of bone matrix in intimate contact with the surface in the area of the central screw threads were observed, indicating high biocompatibility. Similar results were seen with machined implants after 30 days. A significant difference in bone formation was observed between the implant types at 15 days. CONCLUSION Bone-to-implant contact was better on the surfaces subjected to laser treatment than on the machined titanium implants. The development of new laser treatments, which promote alterations in the surface energy as well as in the macro- and microstructures of titanium, may lead to improved bone-to-implant contact and thus better outcomes.

An electrospun nanocomposite fibrous material holds promise as a scaffold, as well as a drug-delivery device to aid in root maturogenesis and the regeneration of the pulp–dentine complex. A novel three-dimensional (3D) nanocomposite scaffold composed of polydioxanone (PDS II®) and halloysite nanotubes (HNTs) was designed and fabricated by electrospinning. Morphology, structure, mechanical properties and cell compatibility studies were carried out to evaluate the effects of HNTs incorporation (0.5–10 wt% relative to PDS w/w). Overall, a 3D porous network was seen in the different fabricated electrospun scaffolds, regardless of the HNT content. The incorporation of HNTs at 10 wt% led to a significant (p

Purpose: To evaluate supracortical bone neoformation with the use of hydroxyapatite (HA) hollow domes specially manufactured for osteogenesis promotion. Materials and Methods: Nine New Zealand rabbits were selected and 18 domes were placed, divided into three groups according to the filler: control (blood clot), vitamin complex, and particulate β-tricalcium phosphate (β-TCP). The healing period was 8 weeks, hence fluorescent markers were applied. After healing, the samples were embedded in resin to prepare slides for light and fluorescence microscopic evaluation of the amount of neoformed bone tissue. Energy dispersive spectroscopy was also used for chemical analysis of the material inside the domes. Results: The quality of neoformed bone tissue with active bone remodeling areas was observed. As a filler, β-TCP showed higher bone formation (14.1%), better quality of neoformed bone tissue with organized structures, and an area of mineralized tissue in the dome. Bone neoformation inside the dome filled with blood clot confirmed the osteoconductive property of HA, as indicated by the migration of osteogenic cells from the blood clot, without the action of another biomaterial (mean area of bone formation for blood clot filler = 7.5%). Bone neoformation was not favored in samples filled with vitamin complex because of the difficulty of blood penetration through the material. Conclusion: HA domes performed well as a scaffold for bone neoformation over the cortical bone of rabbits, and this is based on maintenance of good stability and good integration with bone tissue. β-TCP presented higher values of neoformed bone area compared with the blood clot. HA domes have osteoconductive properties, especially when filled with blood clot, because of the migration of osteogenic cells without action of any other biomaterial. In domes filled with vitamin complex, no bone formation was noted because of the absence of resorption.

Titanium and its alloys are the main metals studied as porous metallic implants by their excellent mechanical properties and biological interactions. Production methods of porous metallic materials are based on powder metallurgy (PM), because it allows the manufacturing of parts with complex shapes and dimensions close to the finals (near-net shape), and the addition of alloying elements reaching a satisfactory structural homogeneity, and porosity. The pore production by space-holder technique constitutes of mixing organic compounds with metal powder, which when removed by thermal treatment prior structures are kept in place. The objective of this study is to obtain porous implants of commercially pure titanium (cpTi) and Ti-13Nb-13Zr alloy by PM with space-holder technique and albumin as an additive. For the processing of the samples were used hydride titanium powder (TiH2) to obtain cpTi samples, and metal powders of Ti, Nb and Zr in the stoichiometric proportions for obtaining the alloy samples. The samples were prepared by mixing the metallic powder to the albumin (30wt%) and filling a silicone model that was pressed isostatically (140 MPa). The thermal treatment was performed in an oxidizing atmosphere (350°C/1h) for the decomposition of organic material. The sintering was performed at a temperature of 1300°C (1h/cpTi, 3h/Alloy) in high vacuum furnace (10-5 mBar) to all samples. The calculated porosity showed a significant difference between the samples cpTi (40%) and alloy (60%). The samples surface characterization showed very rough with high specific surface area. Samples of cpTi presented formation of necks arising from sintering. In the alloy samples were observed homogenous microstructure with the presence of α and β phases composing the Widmanstätten structure. It is possible to conclude that the same amount albumin allowed the formation of pores in the microstructure of cpTi and alloy although in different proportions, without harming the sintering of both and allowing diffusion of the alloy elements.

The effects of adding polymer precursor on the sintering behavior, microstructure and hardness of alumina ceramics have been studied. Polymer sintering aid polymethylhidrogensiloxane were used for alumina based ceramics sintered at 1650º C. The sintered materials were characterized using: (a) helium picnometry to determine apparent density; (b) x-ray diffraction analysis, scanning electron microscopy, transmission electron microscopy and energy dispersive x-ray spectrometry to determine the microstructure and composition; (c) Vickers indentation analysis to determine the hardness and fracture toughness. The addition of polymethylhidrogensiloxane yielded alumina/mullite composites. The preparation of ceramic composites using small amounts of polymer precursors is suited for alumina based ceramics. The processing route being simple, it has the potential to enable the manufacture of complex shaped pieces.

Production of nanometric ceramic powders is one of the most recent advances in materials science. However the large scale production of some materials is still a challenge. There are two approaches to the fabrication of nanomaterials that results in powders with distinct characteristics. In high energy milling the particle size is reduced by mechanical forces to achieve nanosized particles. Another technique is reactive milling in which nanometric particles are synthesized by mechanically activated reactions. In this work NbC nanoparticles were produced by high energy milling of commercial NbC and by self-sustained high energy reactive milling of Nb2O5-Al-C powder mixture. The NbC particles were desagglomerated for 1h in a planetary mill. The obtained powders were characterized by X-ray diffraction, scanning electron microscopy and laser diffraction. The objective of this study was to compare the efficiency of two employed techniques to determine the most of producing nanoscale NbC.

In this present work Ti-13Nb-13Zr alloy was produced by PM using planetary ball mill with zirconium oxide grinding bowl and balls to reduce contamination. The effect of milling time upon microstructure and microhardness was studied. Powders have been produced by hydrogenation of Ti, Nb and Zr at 1MPa. Milling speed was 200 rpm during 90 to 360 min. Sintering was carried out at 1150°C during 10h. Powder size distribution was analyzed using CILAS equipment and chemically characterized by X-Ray Fluorescence (XRF). Microhardness was determined by means of a Vickers microhardness tester. Microstructure and phases were analyzed employing scanning electron microscopy (SEM) and X-Ray diffraction.

Silicon carbide is used to produce abrasive and high-temperature structural ceramic materials due to its mechanical and chemical properties. The possible applications of porous silicon carbide ceramics are diesel engines catalysers and molten metal filters. In the last years the starch gained importance as a pore-forming and consolidation agent, due to it is environmental friendly and easily processing. The current work uses starch (corn, rice and potato) as pore forming and consolidation agent. The samples sintered at different sintering times were characterized by density and microstructure (XRD, SEM). The results show that the samples presented porosity between 20 and 40% and the microstructures obtained is homogeneous with a pore size similar to the starch particle added.

Ceramic materials based on alumina are considered excellent for produce cutting tools used to machining hard metals. However, low mechanical strength and toughness presented by these materials limit their application. Traditionally particles, such as TiC, TiN and ZrO2, are added to the alumina matrix to improve their mechanical properties, increasing the range of applications. Recent studies have shown that the addition of particles of different sizes in alumina matrix can promote simultaneous increase in mechanical strength and tenacity. In this work sintering behavior of Al2O3micro-nanocomposite containing nanometric particles of NbC and micrometric particles of WC, was studied by dilatometry using heating rate of 20°C/min up to 1800°C. The addition of carbides in alumina matrix is prejudicial to sintering causing an increase in temperature of shrinkage.

Titanium alloys are widely used in biomedical applications due to their excellent properties such as high strength, good corrosion resistance and biocompatibility. Titanium alloys with alloying elements such as Nb and Zr are biocompatible and have Young's modulus close to that of human bone. To increase the bioactivity of titanium alloy surfaces is used chemical treatment with NaOH followed by immersion in simulated body fluid (SBF). The purpose of this study was to produce the alloy Ti-27Nb-13Zr with low Young's modulus by powder metallurgy using powders produced by the HDH process. The formation of biomimetic coatings on samples immersed in SBF for 3, 7, 11 and 15 days was evaluated. Characterization of the coating was performed by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and scanning electron microscope. The microstructure and composition of the alloy were determined using SEM and XRD, while the mechanical properties were evaluated by determining the elastic modulus and the Vickers microhardness. The sintered alloys were composed of α and β phases, equiaxed grains and with density around 97.8% of its theoretical density. The Vickers microhardness and elasticity modulus of the alloy were determined and their values indicate that this alloy can be used as a biomaterial. Analysis of the coating revealed the presence of calcium phosphate layers on samples immersed for >3 days in the SBF solution.

O capeamento pulpar é uma medida importante e muito usada no cotidiano da prática odontológica e, quando realizado de forma consciente, baseado em um bom diagnóstico da condição pulpar no momento da exposição, pode prevenir o dente de sofrer uma intervenção endodôntica. Além do hidróxido de cálcio, outros materiais vêm sendo testados quanto a sua ação em promover o reparo pulpar pela formação de ponte de dentina, após capeamento pulpar direto. Uma das alternativas de materiais viáveis para o capeamento pulpar são as cerâmicas à base de fosfatos de cálcio, destacando-se a hidroxiapatita (HAp) e o fosfato tricálcico (β-TCP). Estes materiais não promovem a formação de área necrótica, característica da utilização do hidróxido de cálcio, são biocompatíveis e favorecem o reparo do tecido pulpar. Para avaliar os efeitos desses materiais no capeamento pulpar foi realizada esta revisão de literatura, abordando desde a resposta do tecido pulpar, até o protocolo para o uso clínico.

The effects of the hydrogenation stage on microstructure and mechanical properties of Ti-13Nb-13Zr alloy produced by powder metallurgy have been studied. Powder alloys have been produced by hydrogenation with 250 MPa or 1 GPa and via high energy planetary ball milling. Samples were isostatically pressed at 200 MPa and sintered at 1150 °C for 7, 10 and 13 hours. Elastic modulus and microhardness were determined using a dynamic mechanical analyzer (DMA) and a Vickers microhardness tester. Density of the samples was measured using a liquid displacement system. Microstructure and phases presents were analyzed employing scanning electron microscopy (SEM). Elastic modulus was 81.3  0.8 and 62.6  0.6 GPa for samples produced by 250 MPa and 1 GPa hydrogenation, respectively when sintered for 7h.

Specific properties of structural ceramics such as their mechanical and thermal stability permit their use in high-speed cutting processes that involve deep cuts and low wear rates. The process by which wear occurs in tribological contacts is complex and cannot be explained by one simple wear mechanism. The contribution of different mechanisms to the total wear of a component is related to the mechanical and chemical properties of both the materials and the contact interface. In this investigation, diffusion tests were carried out to determine the influence of chemical interactions between alumina composite and gray cast iron, without the interference of mechanical wear mechanisms. These tests were carried out at 1100°C using static couples. The tests did not generate a strong metal–ceramic interface, indicating that the alumina composites were chemically stable under the test conditions.

In this work alumina based composites ceramics with a polymeric precursor (polysiloxane) and metallic Ti with two different size particle distribution, Ti without milling (ATM) and 5h milling (ATM5), were characterized. PMS thermogravimetric curve indicates that the weight loss percentage was about 20%. The densities achieved were 3,50g/cm3 and 3,70g/cm3 for samples prepared with Ti as received and 5h milling, respectively. During decomposition of the polymer during pyrolysis and sintering, the particles of the matrix may react with carbon and Si from the polymer precursor, metallic Ti and gas atmosphere, nitrogen, to form different phases. The ATM samples presented Al2O3 and TiCN. The specimens prepared with 5h milling Ti (ATM5) is constituted by mullite besides Al2O3 and TiCN. The ATM5 samples have smaller densities than ATM but there is no significant difference in the hardness values.

Foram estudados os efeitos da adição de polímero precursor na sinterização, microestrutura e dureza da alumina. O polímero inorgânico polifenilmetilvinilhidrogenosilsesquioxano (PPS) foi utilizado como aditivo em cerâmicas de alumina sinterizadas a 1650 ºC. Os materiais sinterizados foram caracterizados por dilatometria, determinando-se a densidade aparente por picnometria de hélio, pela análise de carbono total, por difração de raios X, por microscopia eletrônica de varredura, espectrometria de energia dispersiva de raios X e por análise de indentação Vickers para determinação de dureza e tenacidade a fratura. Foram obtidas fases heterogêneas de Si2Al4O4N4 nas amostras com PPS. Dentre as amostras analisadas, a que contém 5% de PPS apresentou dureza e tenacidade à fratura superiores à da alumina pura. A preparação de compósitos cerâmicos com pequenas quantidades de polímero precursor mostrou-se um processo adequado para cerâmicas à base de alumina, sendo uma rota simples de conformação com grande potencial para a obtenção de peças com geometria complexa.

Methylsilicone resin as a polymer precursor for a SiOC ceramic material was cured and foamed by electron beam (EB) irradiation in air prior to the pyrolysis under an inert atmosphere. Methylsilicone foams were obtained without additional foaming agent when exposed to accelerated electrons with radiation doses up to 9 MGy and dose rate of 2.8 kGy/s. During irradiation the polymer was melted and simultaneously gaseous products were formed by the methyl group oxidation and by the poly-condensation crosslinking reactions. The formed gases could not escape from the molten polymer and began to aggregate into bubbles. The effect of the radiation dose on the polymer foam molecular structure, the gel fraction and the ceramic yield was analyzed. The results indicate that the maximum amount of crosslinking in methylsilicone, when EB radiation is used, occurred between 1.0 and 2.0 MGy radiation dose. Methylsilicone foams were pyrolysed in N 2 atmosphere at temperatures of 1200 and 1500 °C, resulting in amorphous SiOC and partially crystalline ceramic foams, respectively. A porosity of ~84% was achieved in the pyrolyzed foams, with cell size ranging from 30 to 300 μm and density of about 0.31 g cm −3 .

Silicon nitride based ceramics have been widely used as structural ceramics, due mainly to their thermo-mechanical properties such as high density, high thermal shock resistance, corrosion resistance and chemical stability. The aim of this study was to determine the influence of rare earth and aluminum oxide additions as sintering aids on densification, microstructure and mechanical properties of silicon nitride. Silicon nitride mixtures with 91 wt. (%) Si3N4 and 9% wt. (%) additives were prepared and sintered. The density, microstructure and mechanical properties of the sintered specimens of these mixtures were determined. In most specimens, scanning electron microscopic examination and X ray diffraction analysis revealed elongated grains of β-Si3N4 with aspect ratio of about 2.0 and dispersed in a glassy phase. The density of the sintered specimens was higher than 94% of the theoretical density (td) and specimens with La2O3 and Al2O3 additions exhibited the highest value. The results of this investigation indicate that the rare earth ion size influences densification of silicon nitride, but this correlation was not observed in specimens containing two different rare earth oxides. The hardness values varied in direct proportion to the density of the specimens and the fracture toughness values were influenced by the composition of the intergranular glassy phase.

Biocompatibility is an important characteristic of dental implant material, and in vitro tests are required to elucidate the interaction between these materials and human tissues. Cell proliferation assays were done with fibroblasts plated on the surface of alumina and hydroxyapatite sintered samples, each with a different surface treatment (sintered, rectified, or polished). After 1, 2, and three days, the samples were prepared for scanning electron microscopy observations. The data were compared by analysis of variance followed by Tukey's test. It was concluded that neither the hydroxyapatite or alumina substrate is cytotoxic, and hydroxyapatite is more biocompatible than alumina.

Mixtures of hydroxyapatite (HAp) and tricalcium phosphate (TCP) powders with different Ca/P ratios were prepared by a wet chemical precipitation synthesis of calcium-deficient hydroxy apatite (CDHA) and subsequent calcination. The influence of precipitation method and calcination temperature on the chemical and physical properties of the resulting powders were evaluated. Different ratios between HAp and TCP were obtained by variation of the velocity of orthophosphoric acid addition into calcium hydroxide suspension. Slow addition (1 mL/min, S-powder) of H3PO4 into Ca(OH)2 suspension lead to a higher amount of CO3 groups substituting PO4 in the apatite lattice compared to powders synthesized by fast addition (200 mL/min, F-powder). Consequently, the Ca/P molar ratio of S-powder (1.55) was higher than that of F-powder (1.52)

Objectives. (1) To synthesize 3 mol% yttria-stabilized zirconia (3Y-TZP) powders via coprecipitation route, (2) to obtain zirconia ceramic specimens, analyze surface characteristics, and mechanical properties, and (3) to compare the processed material with three reinforced dental ceramics.Methods. A coprecipitation route was used to synthesize a 3 mol% yttria-stabilized zirconia ceramic processed by uniaxial compaction and pressureless sintering. Commercially available alumina or alumina/zirconia ceramics, namely Procera AllCeram (PA), In-Ceram Zirconia Block (CAZ) and In-Ceram Zirconia (IZ) were chosen for comparison. All specimens (6 mm x 5 mm x 5 mm) were polished and ultrasonically cleaned. Qualitative phase analysis was performed by XRD and apparent densities were measured on the basis of Archimedes principle. Ceramics were also characterized using SEM, TEM and EDS. The hardness measurements were made employing Vickers hardness test. Fracture toughness (K(IC)) was calculated. Data were analyzed using one-way analysis of variance (ANOVA) and Tukey's test (alpha = 0.05).Results. ANOVA revealed that the Vickers hardness (p Significance. The coprecipitation method used to synthesize zirconia powders and the adopted ceramic processing conditions led to ceramics with mechanical properties comparable to commercially available reinforced ceramic materials. (C) 2008 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

A novel bone scaffolding material was successfully fabricated by electrospinning from hyperbranched polyglycerol (HPGL) solutions containing nanoparticles of hydroxyapatite (HA). The potential use of the electrospun fibrous HPGL-HA scaffolds for bone regeneration was evaluated in vitro with human osteoblasts in terms of alkaline phosphatase (ALP) activity of the cells that were cultured directly on the scaffolds. The results were compared with those on corresponding HPLG-HA solution-cast film scaffolds. It was found that all of the fibrous scaffolds promoted much better adhesion and proliferation of cells than the corresponding film scaffolds.

In recent years, the processing of porous ceramic materials for implant applications has motivated the development and optimization of new technologies. To this purpose, a globular protein based (i.e. ovalbumin) consolidation approach has been proposed. In the present study, a porous hydroxyapatite:b-tricalcium phosphate - biphasic ceramics (BCP), was processed by consolidation using the protein-action technique. The processed ceramic materials exhibited appropriate pore configuration in terms of size, morphology and distribution. The in vitro reactivity and dissolution behavior of the ceramics was evaluated in SBF and biocompatibility in an osteoblasts culture, respectively. Overall, the materials tested showed biocompatibility and suitable properties for osteoconduction. A rough surface pattern displayed by the ceramics seemed to have improved both; cell adhesion and proliferation processes. In conclusion, this study revealed that the porous matrices obtained, promoted suitable development of cell metabolism without cellular death.

Reinforcement with yttria stabilized zirconia (YSZ) is an alternative to improve mechanical strength of hydroxyapatite (HAp) ceramic. However, calcium may react with zirconium to form calcium zirconate. In addition, decomposition of HAp to tricalcium phosphate (TCP) occurs with water loss inhibiting ceramic densification. In order to minimize the formation of these compounds, two synthesis routes were compared in this work: coprecipitation of hydrous yttria stabilized zirconia in a calcium phosphate gel medium and powder mixture of individual calcined powders. Composite nominal compositions were fixed at 90 and 95 HAp wt%. Calcium, zirconium and yttrium chlorides and ammonium hydrogen phosphate were the employed precursors. Ammonium hydroxide was the selected precipitation agent. Calcination was performed at 800oC for 1 hour and pellets were sintered in the range of 1150 and 1350oC for 1, 3 and 5 hours. Ceramic samples were characterized by scanning electron microscopy and apparent density measurements. Crystalline phases were quantified by Rietveld analysis of X-ray diffraction patterns. Results indicate that powders prepared by coprecipitation can cause porosity formation due to the higher chemical reactivity during synthesis process.

O carbeto de silício (SiC) é utilizado como material estrutural devido à boa combinação de propriedades, como altas resistências ao desgaste, ao choque térmico e à oxidação. Cerâmicas à base de SiC foram obtidas com aditivos poliméricos polimetilhidrogenossiloxano, polimetilhidrogenossiloxano com D4Vi e, como aditivos de sinterização, alumina (Al2O3, 4% em peso) e ítria (Y2O3, 4% em peso). Após obtenção das composições, foi feita cura, pirólise (500 ºC e 900 ºC/1 h) e sinterização dos materiais compactados (1850 ºC e 1950 ºC/1 h, sob Ar). A maior densidade obtida foi 3,0 g/cm³ para as amostras pirolisadas a 900 ºC/1 h e sinterizadas a 1950 ºC/1 h. Foram avaliados os efeitos dos aditivos poliméricos na microestrutura e na dureza das cerâmicas. A obtenção de compósitos cerâmicos utilizando pequenas adições de polímeros precursores cerâmicos mostrou-se viável para materiais à base de SiC, apesar da alta perda de massa. É uma rota simples de conformação, com grande potencial para a fabricação de peças com geometria complexa.

This study presents the in-vivo evaluation of Ti–13Nb–13Zr alloy implants obtained by the hydride route via powder metallurgy. The cylindrical implants were processed at different sintering and holding times. The implants' were characterized for density, microstructure (SEM), crystalline phases (XRD), and bulk (EDS) and surface composition (XPS). The implants were then sterilized and surgically placed in the central region of the rabbit's tibiae. Two double fluorescent markers were applied at 2 and 3 weeks, and 6 and 7 weeks after implantation. After an 8-week healing period, the implants were retrieved, non-decalcified section processed, and evaluated by electron, UV light (fluorescent labeling), and light microscopy (toluidine blue). BSE-SEM showed close contact between bone and implants. Fluorescent labeling assessment showed high bone activity levels at regions close to the implant surface. Toluidine blue staining revealed regions comprising osteoblasts at regions of newly forming/formed bone close to the implant surface. The results obtained in this study support biocompatible and osseoconductive properties of Ti–13Nb–13Zr processed through the hydride powder route.

Nanocrystalline hydroxyapatite was prepared by a precipitation method with add of ultrasonic irradiation. In this work the effect of H3PO4 addition rate during synthesis and the influence of the magnesium incorporation into apatite were studded. The results revealed that the morphology and cristalinity of synthesized nanopowders are significantly affected by ultrasonic irradiation. Monophase hydroxyapatite was obtained when magnesium was added into HA lattice during the synthesis with ultrasonic irradiation.

In many in-vivo and in vitro studies, the behavior of calcium phosphate ceramics like β - tricalcium phosphate in biological environments has been reported to be predictive and positive. In terms of bone tissue growth, this ceramic can be more attractive presenting a porous microstructure. To obtain biomaterial quality ceramics, in this investigation β- TCP porous ceramics were prepared by a special consolidation method with albumin as a foam generating agent. This technique enables preparation a variety of formats with complex geometries. To obtain porous samples using albumin, heat had to be introduced into the system during the consolidation stage. After consolidation, the samples were sintered at 1250oC for 30 minutes and characterized using X-ray diffractometry, scanning electron microscopy and mercury porosimetry. The foams that were obtained by this method exhibited spherical and interconnected pores, characteristics desirable in biomedical implants.

Tricalcium phosphate based ceramics (TCP) are bioresorbable and thereby considered to be promising bone replacement materials. The differences in crystal structure between {alpha} and {beta}-TCP phases gives rise for different dissolution rates in vitro and in vivo, which may alter the bioresorbable behavior of TCP ceramics. It is suggested that the addition of magnesium ions, which are also present in biological tissues, stabilizes {beta}-phase to higher temperatures and thus enables the sintering of {beta}-TCP at elevated temperatures compared to Mg free TCP. In this paper, Mg-substituted TCP, with the general formula (Ca{sub 1-x}Mg {sub x}){sub 3}(PO{sub 4}){sub 2} and 0.01 {

beta-tricalcium phosphate (beta-TCP) and biphasic calcium phosphate powders (BCP), consisting of hydroxyapatite (HA) and beta-TCP, were synthesized by thermal decomposition of precursor powders obtained from neutralization method. The precursor powders with a Ca/P molar ratio of 1.5 were prepared by adding an orthophosphoric acid (H(3)PO(4)) solution to an aqueous suspension containing calcium hydroxide (Ca(OH)(2)). Mixing was carried out by vigorous stirring and under sonochemical irradiation at 50 kHz, respectively. Glycerol and D-glucose were added to evaluate their influence on the precipitation of the resulting calcium phosphate powders. After calcination at 1000 degrees C for 3 h BCP nanopowders of various HA/beta-TCP ratio were obtained.

In the last years, the porosity in ceramic materials for implants production has motivated the development of various technologies. Calcium phosphate ceramics, in special the tricalcium phosphate - TCP, are very promising as bone substitutes and scaffolds for tissue engineering. The macroporosity incorporation in TCP ceramics by porogenic, foaming and consolidator agent, as globular protein (ovalbumin) was the focus of this work. Preliminary studies of zeta potential were made to have a suitable suspension. Ovalbumin amounts (5-7 wt%) were added to the ceramic slurries and suspensions with a solid percentage higher than 60 wt% were obtained. The interaction albumin/surfactant with detergency properties was evaluated by pH and viscosity measurements. The foam was produced by mechanical stirring. The results suggested that the presence of the surfactant increase the volume and stability of foam. After drying, burnout and sintering (1200oC/30 min.) the phase composition of the foams was determined by X-ray diffraction. The microstructure and porosity were evaluated by scanning electron microscopy. SEM micrographs of the foam show that the structure consists of a permeable porous network, being observed spherical and interconnected pores.

A process for synthesis of fine zirconium titanate powders by chemical route is described. Zirconium/titanium molar ratio was varied from 0.67 to 1.5 and the powders produced were analyzed. The precipitation process comprises the mixture of zirconium and titanium metal salt solutions to ammonium hydroxide solution, followed by washing of the precipitate, calcination and grinding to result in zirconium titanate. The ceramic powder is then uniaxially pressed as cylindrical samples and sintered at 1400°C for 5 hours. The microstructure of fractured and thermally etched ceramic was observed by scanning electron microscopy, and crystal phase identifications were done by X-ray diffraction. At least two different zirconium titanate phases, ZrTiO4 and Zr5Ti7O24, were identified. Ceramic hardness was measured by Vickers indentation.

Calcium phosphates with different Ca/P molar ratio can be obtained depending the precipitation conditions such as pH and temperature. In this work the effect of the pH’s variation during the H3PO4 addition in the synthesis of hydroxyapatite-HA, (Ca/P molar ratio 1.67) by neutralization method, was studied. The H3PO4 addition’s rate was 1.0, 1.5, 8.0 mL.min-1 and in other experiment the H3PO4 was added at a time. After the addition was completed the pH ranged from 7-12. The suspensions were kept during 24 hours for ripening. The precipitate was separated from the suspension by vacuum filtration, washed with distilled water and dried at 70°C/24h. Afterwards the materials were analyzed by thermogravimetric analysis (TGA) with heating rate of 10°C/min in air. The calcination of the powders was accomplished at 800°C/3h with heating rate of 10°C.min-1. The powders were characterized by X-ray diffraction (XRD), infrared spectrometry (FTIR), specific surface area (BET), and scanning electron microscopy (SEM). The results indicated that the ratio of addition of the acid can influence both the morphology and the formation of the phases (HA and TCP) in the obtained powders.

Comparing to hydroxyapatite (HA), which forms a strong chemical bond with the bony tissues, metallic materials are not able to bond with bone. For this reason, a great variety of complex coating methods, such as pulse-laser deposition, ion-beam assisted deposition and plasma-spray has been used to form a HA layer onto metallic surfaces. This study evaluated the performance of the biomimetic technique on apatite-based coating formation on two Tialloys. Ti-13Nb-13Zr and Ti-35Nb-7Zr-5Ta were obtained via powder metallurgy. The Tibased alloys were biomimetically coated using a technique which was modified from the conventional ones using a sodium silicate solution as the nucleant agent. Both alloys presented similar behavior in the evaluated conditions which means the formation of a homogeneous and well defined HA coating. These results show that these new non-toxic Tialloys seem to be very promising for biomedical applications.