Jia, Jiangang and Siddiq, Abdur R. and Kennedy, Andrew R. (2015) Porous titanium manufactured by a novel powder tapping method using spherical salt bead space holders: characterisation and mechanical

Porous Ti with open porosity in the range of 70-80% has been made using Ti powder and a particulate leaching technique using porous, spherical, NaCl beads. By incorporating the Ti powder into a pre-existing network of salt beads, by tapping followed by compaction, salt dissolution and “sintering”, porous structures with uniform density, pore and strut sizes and a predictable level of connectivity have been produced, showing a significant improvement on the structures made by conventional powder mixing processes. Parts made using beads with sizes in the range of 0.5-1.0 mm show excellent promise as porous metals for medical devices, showing structures and porosities similar to those of commercial porous metals used in this sector, with inter-pore connections that are similar to trabecular bone. The elastic modulus (0.86 GPa) is lower than those for commercial porous metals and more closely matches that of trabecular bone and good compressive yield strength is retained (21 MPa). The ability to further tailor the structure, in terms of the density and the size of the pores and interconnections has also been demonstrated by immersion of the porous components in acid. 1.0 Introduction Permanent, porous biomaterial structures have the ability to provide a transitional space between bone and a biomaterial substrate (which provides the main structural support) and an appropriate level and geometry of porosity will allow the in-growth of new bone tissue and vascularisation, so that good integration with the host bone tissue can be obtained [1,2]. Porous titanium continues to attract attention as a biomaterial for medical applications, owing to its excellent specific mechanical properties, chemical stability and biocompatibility [1-3] and numerous processes have been developed to manufacture porous Ti, comprehensively reviewed in [2,4]. Porous metal fabrication using sacrificial space-holders offers the ability to control the pore size and shape, with the potential to achieve good pore uniformity and interconnectivity [5-10]. There are problems with this method, however, originating from unpredictable and inhomogeneous mixing of the space holder and