Integration of space-holder technique and spark plasma sintering: An innovative approach for crafting radially graded porosity implants

Bone resorption and possible fracture of host tissue are some consequences resulting from the mismatch between the Young's Modulus of the constituent materials of implants and bone that compromises the reliability of implants for replacing damaged bone tissue. The use of functional graded porous materials presents an interesting approach that could help decrease the Young's modulus while simultaneously mimicking highly hierarchical porosity of the bone structure. However, these structures are more difficult to fabricate than those with homogenous porosity. The design and distribution of this porosity in the implant must ensure the biomechanical and biofunctional balance of the bone tissue it is intended to replace. In this study, Ti radially graded structures were successfully fabricated using Spark Plasma Sintering combined with Space Holder Technique. The effects of temperature on porosity and mechanical properties were thoroughly examined. The results indicated that this processing route allows to achieve good control of porosity, close to the amount of added spacer. Yield stress of 181 MPa and an elastic modulus of 56 GPa were obtained for samples sintered at 800 °C for 5 min under a pressure of 6.3 MPa. These mechanical properties make the structure a viable candidate for replacing human long bones.