Cladding of titanium/hydroxyapatite composites onto Ti6Al4V for load-bearing implant applications

To improve the bioactivity of Ti6Al4V alloy for use as a load-bearing hard tissue replacement, titanium/hydroxyapatite (Ti/HA) composites were bonded to a Ti6Al4V substrate by a novel cladding method. With the aid of a silver foil as the interlayer and an external pressure during sintering, the interfaces between the composites and the substrate were free of defects. The bioactivity of the fabricated materials was evaluated in the simulated body fluid (SBF) and the results demonstrated that the materials could induce nucleation and growth of bone-like apatite in the SBF. Factors that contributed to the bioactivity of the materials were discussed. The release of Ag+ ions from the materials was also detected, which is expected to impart antibacterial effect after implantation, and further enhance the functionalities of the materials.Peer reviewed: YesNRC publication: Ye

Cladding of titanium/fluorapatite composites onto Ti6Al4V substrate and the in vitro behaviour in the simulated body fluid

To improve the bioactivity of Ti6Al4V alloy, an innovative cladding method has been developed to bond a Ti/fluorapatite (FA) composite onto the alloy for load-bearing applications. With the aid of a silver interlayer and external pressure during sintering, a defect-free interface between the composite and the substrate was obtained. The fabricated materials were bioactive and could induce the nucleation and formation of bone-like carbonated apatite after immersed in the simulated body fluid (SBF). Functional ions, such as Ag+ and F 12, were released from the materials during immersion, which could impart favourable activities for the implant. This work demonstrated that a simple and novel method could be applied to enhance functionalities of Ti alloys for load-bearing implant applications.Peer reviewed: YesNRC publication: Ye

Fabrication of metal matrix composites by metal injection molding: A review

Metal injection molding (MIM) is a near net-shape manufacturing technology that is capable of mass production of complex parts cost-effectively. The unique features of the process make it an attractive route for the fabrication of metal matrix composite materials. In this paper, the status of the research and development in fabricating metal matrix composites by MIM is reviewed, with a major focus on material systems, fabrication methods, resulting material properties and microstructures. Also, limitations and needs of the technique in composite fabrication are presented in the literature. The full potential of MIM process for fabricating metal matrix composites is yet to be explored.Peer reviewed: YesNRC publication: Ye

Characterization of sintered titanium/hydroxyapatite biocomposite using FTIR spectroscopy

Fourier transform infrared (FTIR) spectroscopy was employed to characterize the phase changes of hydroxyapatite (Ca10(PO4)6(OH)2, HA) in a titanium/HA biocomposite during sintering. The effects of sintering temperature and the presence of Ti on the decomposition of HA were examined. It was observed that pure HA was stable in argon atmosphere at temperatures up to 1,200\ub0C, although the dehydroxylation of pure HA was promoted by the increase in sintering temperature. In the Ti/HA system, on the other hand, the presence of Ti accelerated dehydroxylation and the decomposition of HA was detected at a temperature as low as 800\ub0C. Tetracalcium phosphate (Ca4P2O9, TTCP) and calcium oxide (CaO) were the dominant products of the decomposition, but no tricalcium phosphate (Ca3(PO4)2, TCP) was detected due to phosphorus diffusion and possible reactions during the thermal process. The main decomposed constituents of HA in Ti/HA system at high temperatures ( 651,200\ub0C) would be CaO and amorphous phases.Peer reviewed: YesNRC publication: Ye

Sintering behavior of HA/Ti composites

The hydroxyapatite/titanium (HA/Ti) composites are considered promising biomaterials for orthopedic applications due to the excellent biocompatibility of HA and good mechanical properties of titanium. Since the HA/titanium composites are normally fabricated through powder metallurgy routes, a clear understanding of the sintering behavior of the composites are essential for the processing and fabrication of the materials. In this study, the sintering behavior of the HA/Ti composites under various conditions was investigated. The effect of the HA concentration, processing parameters such as sintering temperature and time, on the sintering kinetics, porosity, interface reactions, and microstructures will be discussed.Peer reviewed: NoNRC publication: Ye

Sintering of 17-4 PH feedstock for metal injection molding

NRC publication: Ye

Sintering of 17-4PH injection molding feedstock

The sintering behavior of 17-4 PH steel injection molding feedstock was investigated in the temperature range of 650\ub0-1050\ub0C. Effects of sintering conditions, such as sintering temperature and sintering atmosphere, were examined. Experimental results showed that when sintered in a hydrogen/nitrogen atmosphere, the 17-4 PH feedstock oxidized over the temperature range of the investigation. The degree of oxidization increased with the increase of sintering temperature. The main oxidization product was Cr2O3 as revealed by x-ray diffraction and composition analysis. The oxidation can be avoided by sintering in vacuum or argon atmosphere.Peer reviewed: NoNRC publication: Ye