Microstructures and fracture characteristics of spark plasma-sintered HAp–5 vol.% Ag composites

Microstructures and mechanical properties of SPSed HAp–5 vol.% Ag composites, using ball-milled Ag and electroless-deposited Ag-coated HAp powders, were investigated by the XRD, SEM and TEM techniques. In the Ag ball-milled HAp powder, many cracks and shrinkage cavities were observed at the interfaces between HAp and large-sized Ag particles due to the mismatch of their thermal expansion coefficients. However, in the composite using 5 vol.% Ag-coated HAp powder by electroless deposition process, no microcracks were found at the interfaces due to the homogeneous and fine distribution of Ag particles. The main fracture mode of ball-milled HAp–Ag composite was a transgranular type with flat fracture morphology although there were found some pulling-out and elongated phenomenon of large Ag particles. However, in electroless-deposited 5 vol.% Ag-coated HAp composite, its fracture surface was appeared to be rougher than that of ball-milled HAp–Ag composite due to the homogenous dispersion of fine Ag particles in the HAp matrix.