Influence of rapid heating with infrared radiation on RF magnetron-sputtered calcium phosphate coatings

This study evaluated the effect of rapid heating with infrared radiation on the physico-chemical and morphological properties of radio frequent (RF) magnetron-sputtered calcium phosphate (Ca-P) coatings. About 2.5 microm thick Ca-P coatings were deposited on titanium disks and cylinders. These specimens were left untreated or were heat treated by infrared radiation at 300, 400, 500, 600, and 700 degrees C for 4, 7, 11, 17, and 24 s. Subsequently, the specimens were immersed in simulated body fluid (SBF) for 1 day, 1 week, and 5 weeks. X-ray diffraction measurements showed that heating at 500 degrees C or higher resulted in an increase of coating crystallinity. In addition, FT-IR measurements revealed the appearance of OH peaks in the spectra of samples treated at 500-700 degrees C. Electron probe microanalysis showed that after 5 weeks of immersion about 40-50% of the coatings heat treated at 500 and 600 degrees C was maintained. The coatings heat treated at 700 degrees C showed no dissolution at all. On the other hand, as-coated and 300 degrees C treated films were dissolved within 1 day. Scanning electron microscopy of the samples showed that directly after heat treatment no apparent cracks were present in the coatings. On the basis of these findings, we conclude that rapid heating with infrared radiation around 600 degrees C is the best heat treatment for RF magnetron-sputtered coatings.