Structure of CaPs coatings electrophoretically deposited on NiTi shape memory alloy

Abstract

The surface of NiTi shape memory alloys applied as long-term implants has been modified by protective calcium phosphates (CaPs) coatings, with the objective of improving the biocompatibility of this material. The calcium phosphates such as hydroxyapatite Ca5(PO3)OH (HAP) and -tricalcium phosphate -Ca3(PO4)2 ( -TCP) were deposited by electrophoretic deposition. In order to improve the adhesion, the deposited samples were vacuumsintered at wide range of temperature from 500 C to 1000 C for 2 h. The studies revealed that applied sintering conditions did not change the structure of CaPs. The coatings consisted of HAP with hexagonal structure (P63=m) and -TCP with rhombohedral structure (R-3c). Changes in lattice parameters for CaPs coatings after deposition and sintering were refined by the Rietveld method.