Vapor Transport Sintering of Porous Calcium Phosphate Ceramics
Vapor transport sintering (VTS) of calcium phosphates in various reactive atmospheres was investigated as a new fabrication method for ceramic scaffolds with fully interconnected porosity. Experiments were carried out for two different starting compositions—β‐tricalcium
phosphate (β‐TCP) and biphasic calcium phosphate (BCP)—within various halide atmospheres and in water vapor. During the nondensifying VTS process, grain and pore size increase simultaneously
although the interconnectivity of the pores is retained. Successful VTS is possible in the presence of several halide acids (HCl, HBr) and solid chlorides (MgCl2,
CaCl2, AgCl). At elevated temperatures, sufficient amounts of volatile species are formed to sustain material transport through evaporation and condensation. The resulting microstructure and phase
composition are both adjustable by choosing appropriate precursor materials, additives and process parameters. Furthermore, the use of AgCl as a sintering additive both facilitates VTS and the condensation of finely dispersed Ag
particles on the scaffold's surface, which may lend antibacterial properties to the implant material.