Production and characterization of optimal porous structural material based on β Ti-Nb-Zr metastable alloy for biomedical applications
The development of porous materials is extensively been investigated for their enthralling applications in the exotic field of hard tissue replacements. The obstruction in a scaffold geometry has been associated with the preferential selection of several characteristics including admissible parameters, for instance, pores morphology, porosity, interconnectivity, permeability that authoritatively characterizes the effect of scaffold pore architecture on tissue integration and ultimately on bone ingrowth. For all the porous implants, the most appropriate pore size for bone ingrowth lies in the range of 100 to 600 um with porosity range 0.3 to 0.45. In this study, a novel experimental approach is applied based on Darcy law to measure the permeability of sintered TiNbZr foam and also to modify the pores morphology by performing controlled dynamic chemical etching at specific holding times and flow rates, with indigenously self-designed apparatus (Fig. 1) to achieve optimum porosity, pores size and permeability range. The influence of dynamic chemical etching at different pressure regimes and holding times on pores size distribution, pores morphology were investigated by means of optical microscopy, scanning electron microscopy and image-J software. In addition, compression tests were conducted to evaluate their mechanical behaviour. It is demonstrated that controlled dynamic chemical etching allows us to optimize the complex characteristics of the porous structure, including an increase in porosity, pore size, and permeability, with adequate mechanical properties. Furthermore, the specimen depict more compression strength at same porosity level after modification by chemical etching as compare to the same porosity sample fabricated by sintered process due to having more cell walls which impart materials strength. The experimental results summarize that the obtained values of permeability lie in the range of human calcaneal bone (ranging from 0.4 to 11*10-9 m2) and maximum impact of pores size retained in range between 100 to 600 µm, thus this technique is highly effective for controlling the porous structures and permeability in the variety of biomedical implants and can be used as post-treatment after fabrication of porous material to control these features.