Coatings of needle/stripe-like fluoridated hydroxyapatite on H₂O₂-treated carbon/carbon composites prepared by induction heating and hydrothermal methods

Abstract

A hydroxyapatite (HA) coating was achieved on H₂O₂-treated carbon/carbon (C/C) composite through hydrothermally treating and induction heating deposited CaHPO₄ coating in an ammonia solution under ultrasonic water bath. Then, this HA coating was placed in a NH₄F solution and hydrothermally treated again to fabricate fluorinated hydroxyapatite (FHA) coatings for 24 h at 353, 373, 393 and 413 K, respectively. The structure, morphology and chemical composition of the HA and FHA coatings were characterized by SEM, XRD, EDS and FTIR, and the adhesiveness and chemical stability of these FHA coatings were examined by a scratch test and an immersion test, respectively. The results showed that the as-prepared FHA coatings contained needle-like or stripe-like crystals, different from those of the HA coating. As the fluoridation temperature rose, the adhesiveness of the FHA coating first increased from 34.8 to 40.9 N at a temperature between 353 and 393 K, and then decreased to 24.2 N at 413 K, while the dissolution rate of the FHA coating decreased steadily. The reasons for the property variation of the FHA coatings were proposed by analyzing the morphology, composition and structure of the coatings.

Keywords

carbon / hydroxyapatite (HA) / coating / scratch test / dissolution behavior