This in vitro and in vivo study compared different topographies of Ti samples (dense, porosity of 30% and 40%) with or not CaP coating, prepared by powder metallurgy. Osteogenic cells from newborn rat calvaria were plated onto the samples and cell adhesion (24 hours), alkaline phosphatase activity (7 and 10 days) and mineralization nodules (14 days) were assessed. Sixteen rabbits were used for in vivo study. Each animal received three non-treated and three treated implants in the right or left tibia, respectively. Histometric evaluation of bone-implant contact (BIC) were assessed at 1, 2, 4 and 8 weeks. Metallographic analysis revealed porosities of 30% and 40%, with pore size ranging from 250 to 350 µm. Cell adhesion test and ALP revealed similar cell behavior, independently of topography and CaP coating (P > 0.05%). However, CaP coating combined with porosity of 40% influenced positively the mineralized matrix formation (P < 0.05%). CaP-coated implants showed higher BIC than non-CaP implants and BIC was different between the short (1 and 2 weeks) and long (4 and 8 weeks) healing periods (P < 0.05%). The results suggest that CaP coating combined with 40% porosity implants allowed greater osteogenesis in vitro and increased BIC in vivo.

The incorporation of refractory hard particles in Al2O3-based composites may inhibit grain growth of the matrix, which could significantly contribute to mechanical performance of the composite. The present study aimed to investigate the potential use of NbC as alumina reinforcing material, as an alternative to other carbides such as TiC and WC. Alumina was mixed with a fixed carbide concentration of 30 wt.(%) in a ball mill and uniaxially hot-pressed at 1650 ºC under a load of 30 MPa in an inert atmosphere. X-ray diffraction revealed no oxidation products were present after the sintering process. Microstructure analyses indicate a homogeneous carbide distribution in the alumina matrix. Results obtained in this study show that alumina reinforced with NbC is a composite material with properties comparable to those of alumina reinforced with WC and TiC, thereby making it good reinforcing material.

A porous material for bone ingrowth with adequate pore structure and appropriate mechanical properties has long been sought as the ideal bone-implant interface. This study aimed to assess in vivo the influence of three types of porous titanium implant on the new bone ingrowth. The implants were produced by means of a powder metallurgy technique with different porosities and pore sizes: Group 1 = 30 % and 180 µm; Group 2 = 30% and 300 µm; and Group 3 = 40% and 180 µm;. Six rabbits received one implant of each type in the right and left tibiae and were sacrificed 8 weeks after surgery for histological and histomorphometric analyses. Histological analysis confirmed new bone in contact with the implant, formed in direction of pores. Histomorphometric evaluation demonstrated that the new bone formation was statistically significantly lower in the group G1 than in group G3, (P = 0.023). Based on these results, increased porosity and pore size were concluded to have a positive effect on the amount of bone ingrowth.

Abstract: The most usual ceramic material for coating turbine blades is yttria doped zirconia. Addition of niobia, as a co-dopant in the Y2O3-ZrO2 system, can reduce the thermal conductivity and improve mechanical properties of the coating. The purpose of this work was to evaluate the influence of the addition of niobia on the microstructure and thermal properties of the ceramic coatings. SEM on coatings fractured cross-section shows a columnar structure and the results of XRD show only zirconia tetragonal phase in the ceramic coating for the chemical composition range studied. As the difference NbO2,5-YO1,5 mol percent increases, the tetragonality increases. A significant reduction of the thermal conductivity, measured by laser flash technique in the zirconia coating co-doped with yttria and niobia when compared with zirconia-yttria coating was observed.

Porous titanium scaffolds are promising materials for biomedical applications such as prosthetic anchors, fillers and bone reconstruction. This study evaluated the bone/titanium interface of scaffolds with interconnected pores prepared by powder metallurgy, using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Porous scaffolds and dense samples were implanted in the tibia of rabbits, which were subsequently killed 1, 4, and 8 weeks after surgery. Initial bone neoformation was observed one week after implantation. Bone ingrowth in pores and the Ca/P ratio at the interface were remarkably enhanced at 4 and 8 weeks. The results showed that the interconnected pores of the titanium scaffolds promoted bone ingrowth, which increased over time. The powder metallurgy technique thus proved effective in producing porous scaffolds and dense titanium for biomedical applications, allowing for adequate control of pore size and porosity and promoting bone ingrowth.

Bone injuries and failures often require the inception of implant biomaterial. Research in this field has received increasing attention recently. In particular, porous metals are attractive due to its unique physical, mechanical, and new bone tissue ingrowth properties. The aim of this work is to investigate age hardening behavior of Ti-35Nb-7Zr-5Ta alloy produced by powder metallurgy. Samples of Ti-35Nb-7Zr-5Ta were produced from a mixture of hydrided powders followed by uniaxial and cold isostatic pressing with subsequent densification by sintering at 1500 °C, in vacuum. After that, the samples were heat treated in three steps; solution treatment (1100/°C), air cooling and aging (600 °C for 4 and 6 hours). Sintered samples were characterized for microstructure and microhardness by scanning electron microscopy and Vickers indentation, respectively. In the homogenized condition alloy exhibited a microstructure consisting primarily of a beta Ti matrix with grain boundary alpha precipitates and a low volume fraction of primary alpha precipitates. In the ageing condition the alloy exhibited the precipitation of refined scale secondary alpha precipitates distributed homogeneously in the beta matrix.

Titanium is an attractive material for structural and biomedical applications because of its excellent corrosion resistance, biocompatibility and high strength-to-weight ratio. The high reactivity of titanium in the liquid phase makes it difficult to produce it by fusion. Powder metallurgy has been shown to be an adequate technique to obtain titanium samples at low temperatures and solid-phase consolidation. The production of compacts with different porosities obtained by uniaxial pressing and vacuum sintering is briefly reviewed. Powder particle size control has been shown to be very important for porosity control. Sample characterization was made using scanning electron microscopy (SEM) images.

Recent studies published in the literature have focused on reinforcing alumina with different refractory carbides and nitrides in order to improve hardness, fracture toughness and wear resistance. The incorporation of hard particles as WC, (Ti,W)C and NbC on alumina matrix has shown to be a good alternative in improving the mechanical properties of the composite material. The present work reports some preliminary results obtained reinforcing alumina with 20 wt. (%) (Ti,W)C and 10 wt. (%) NbC. Alumina, (Ti,W)C and NbC powders were homogenized and mixed in a planetary ball mill and subsequently hot-pressed at 1650 °C under 20 MPa in flowing argon. Specimens were characterized by Vicker's microhardness (H V), fracture toughness (K IC), X ray diffraction and scanning microscopy. The composite material showed hardness values of 19.5 GPa and fracture toughness values <FONT FACE=Symbol>»</FONT> 5.2 MPa.m½. The high fracture toughness encountered in this work is related to the crack deflection mechanism.

O propósito deste estudo foi avaliar a reparação óssea ao redor de implantes de superfície porosa comparados com implantes de superfície rugosa, ambos confeccionados de titânio puro grau 2 por meio da técnica de metalurgia do pó. Os implantes foram inseridos em tíbias de coelhos. Foram utilizados neste estudo 7 coelhos machos, sendo que cada um recebeu 3 implantes de superfície porosa na tíbia esquerda e 3 implantes de superfície rugosa na tíbia direita. Os animais foram sacrificados 4 semanas após a cirurgia e os fragmentos das tíbias contendo os implantes foram submetidos à análise histológica e histomorfométrica, visando analisar a neoformação óssea na interface osso-implante. As médias (%) obtidas na análise histomorfométrica foram avaliadas por meio do teste estatístico t-student de amostras pareadas com nível de significância de 5%. Os resultados da análise histológica mostraram que a osseointegração foi obtida nos dois tipos de implantes com similar qualidade de tecido ósseo. Na análise histomorfométrica, verificaram-se médias de neoformação óssea na interface osso-implante de 79,69% ± 1,00 e 65,05 ± 1,23 para os implantes de superfície porosa e rugosa, respectivamente, e foi observada diferença estatisticamente significante entre os dois tipos de implantes com relação à quantidade de neoformação óssea. Concluiu-se que os implantes de superfície porosa contribuíram para a osseointegração devido à sua maior superfície de contato na interface osso-implante.

The purpose of this study was to analyze the bone repair around commercially pure titanium implants with rough and porous surface, fabricated using powder metallurgy technique, after their insertion in tibiae of rabbits. Seven male rabbits were used. Each animal received 3 porous-surface implants in the left tibia and 3 rough-surface implants in the right tibia. The rabbits were sacrificed 4 weeks after surgery and fragments of the tibiae containing the implants were submitted to histological and histomorphometric analyses to evaluate new bone formation at the implant-bone interface. Means (%) of bone neoformation obtained in the histomorphometric analysis were compared by Student's t-test for paired samples at 5% significance level.. The results of the histological analysis showed that osseointegration occurred for both types of implants with similar quality of bone tissue. The histomorphometric analysis revealed means of new bone formation at implant-bone interface of 79.69 ± 1.00% and 65.05 ± 1.23% for the porous- and rough-surface implants, respectively. Statistically significant difference was observed between the two types of implants with respect to the amount new bone formation (p<0.05). In conclusion, the porous-surface implants contributed to the osseointegration because they provide a larger contact area at implant-bone interface.

Titanium alloys have several advantages over ferrous and non-ferrous metallic materials, such as high strengthto-weight ratio and excellent corrosion resistance. A blended elemental titanium powder metallurgy process has been developed to offer low cost commercial products. The process employs hydride-dehydride (HDH) powders as raw material. In this work, results of the Ti-35Nb alloy sintering are presented. This alloy due to its lower modulus of elasticity and high biocompatibility is a promising candidate for aerospace and medical use. Samples were produced by mixing of initial metallic powders followed by uniaxial and cold isostatic pressing with subsequent densification by isochronal sintering between 900 up to 1600 °C, in vacuum. Sintering behavior was studied by means of microscopy and density. Sintered samples were characterized for phase composition, microstructure and microhardness by X-ray diffraction, scanning electron microscopy and Vickers indentation, respectively. Samples sintered at high temperatures display a fine plate-like alpha structure and intergranular beta. A few remaining pores are still found and density above 90% for specimens sintered in temperatures over 1500 °C is reached.

Titanium alloys parts are ideally suited for advanced aerospace systems because of their unique combination of high specific strength at both room temperature and moderately elevated temperature, in addition to excellent corrosion resistance. Despite these features, use of titanium alloys in engines and airframes is limited by cost. The alloys processing by powder metallurgy eases the obtainment of parts with complex geometry. In this work, results of the Ti-6Al-4V and Ti-13Nb-13Zr alloys production are presented. Samples were produced by mixing of initial metallic powders followed by uniaxial and cold isostatic pressing with subsequent densification by sintering between 900 up to 1500 °C, in vacuum. Sintered samples were characterized for phase composition, microstructure and microhardness by X-ray diffraction, scanning electron microscopy and Vickers indentation, respectively. It was shown that the samples were sintered to high densities and presented homogeneous microstructure from the elements dissolution with low interstitial pick-up.

Alumina-based composites have been developed in order to improve the mechanical properties of the monolithic matrix and to replace the WC-Co material for cutting tool applications. Al2O3 reinforced with refractory carbides improves hardness, fracture toughness and wear resistance to values suitable for metalworking applications. Al2O3-NbC composites were uniaxially hot-pressed at 1650 °C in an inert atmosphere and their mechanical properties and microstructures were analyzed. Sintered density, average grain size, microhardness and fracture toughness measurements and microstructural features were evaluated. Results have shown that the mechanical properties of alumina-NbC are comparable to other carbide systems. Microstructural analysis has shown that the niobium carbide particles are mainly located at the grain boundaries of alumina grains, which is an evidence of the "pinning effect", produced by NbC particles.