The Effect of Gravity on the Combustion Synthesis of Porous Biomaterials

Production of highly porous composite materials by traditional materials processing is limited by difficult processing techniques. This work investigates the use of self propagating high temperature (combustion) synthesis (SHS) to create porous tricalcium phosphate (Ca3(PO4)2), TiB-Ti, and NiTi in low and microgravity. Combustion synthesis provides the ability to use set processing parameters to engineer the required porous structure suitable for bone repair or replacement. The processing parameters include green density, particle size, gasifying agents, composition, and gravity. Tricalcium phosphate produced through the reaction: 3CaO + P2O5 = Ca3(PO4)2 (1) has the ability of being resorbed in-vivo. Currently titanium is used in a number of biomedical applications. The reactions incorporating Ti investigated here are: (x+y)Ti + xB = yTi + xTiB (2) Ni + Ti = NiTi (3) The advantage of the TiB-Ti system is the high level of porosity achieved together with a modulus that can be controlled by both composition (TiB-Ti) and porosity. At the same time, NiTi exhibits shape memory properties. SHS of biomaterials allows the engineering of required porosity coupled with resorbtion properties and specific mechanical properties into the composite materials to allow for a better biomaterial.