Transformation of induction heating deposited monetite coating to hydroxyapatite coating on HT-C/C composites by hydrothermal treatment in two types of solution

Monetite coatings on H2O2-treated carbon/carbon composites were prepared by induction heating deposition method and then converted to HA coatings by hydrothermal treatment in an autoclave with two different types of solutions, respectively NaOH aqueous solution and ammonia solution. The structure, morphology and chemical composition of the as-achieved HA coatings were characterized by XRD, FTIR SEM and EDS. The adhesion of HA coatings to the HT-C/C substrates was evaluated by a scratch test. The results showed that there are no obvious changes in the structure and morphology for the as-achieved HA coatings except to their compositions. The average critical load of the ammonia hydrothermally treated HA coatings is 10.9 N, while the NaOH hydrothermally treated HA coatings show the average one of 51 N, and the reason for it was suggested.