Spark plasma sintering synthesis of porous nanocrystalline titanium alloys for biomedical applications.

The reason for the extended use of titanium and its alloys as implant biomaterials stems from their lower elastic modulus, their superior biocompatibility and improved corrosion resistance compared to the more conventional stainless steel and cobalt-based alloys [Niinomi, M., Hattori, T., Niwa, S., 2004. Material characteristics and biocompatibility of low rigidity titanium alloys for biomedical applications. In: Jaszemski, M.J., Trantolo, D.J., Lewandrowski, K.U., Hasirci, V., Altobelli, D.E., Wise, D.L. (Eds.), Biomaterials in Orthopedics. Marcel Dekker Inc., New York, pp. 41-62]. Nanostructured titanium-based biomaterials with tailored porosity are important for cell-adhesion, viability, differentiation and growth. Newer technologies like foaming or low-density core processing were recently used for the surface modification of titanium alloy implant bodies to stimulate bone in-growth and improve osseointegration and cell-adhesion, which in turn play a key role in the acceptance of the implants. We here report preliminary results concerning the synthesis of mesoporous titanium alloy bodies by spark plasma sintering. Nanocrystalline cp Ti, Ti-6Al-4V, Ti-Al-V-Cr and Ti-Mn-V-Cr-Al alloy powders were prepared by high-energy wet-milling and sintered to either full-density (cp Ti, Ti-Al-V) or uniform porous (Ti-Al-V-Cr, Ti-Mn-V-Cr-Al) bulk specimens by field-assisted spark plasma sintering (FAST/SPS). Cellular interactions with the porous titanium alloy surfaces were tested with osteoblast-like human MG-63 cells. Cell morphology was investigated by scanning electron microscopy (SEM). The SEM analysis results were correlated with the alloy chemistry and the topographic features of the surface, namely porosity and roughness.

The influence of short-time ball-milling on the stability of amorphous CoFeB alloys.

The influence of short-time milling on the atomic structure of amorphous Co(70.3)Fe(4.7)B(25) has been investigated by differential scanning calorimetry (DSC), x-ray powder diffraction (XRD), vibrating sample magnetometer (VSM) and x-ray absorption fine-structure (XAFS) techniques. Our results prove that the milling process crystallizes the initially amorphous sample and that the degree of inherent crystallization is inversely proportional to the powder particle size. The investigation of the local atomic structure documents very similar environments around the Co and Fe atoms. The high-energy ball-milling of amorphous precursor represents a practical way to prepare powders having the desired amorphous/nanocrystalline microstructure.