Ultrasound assisted anodic oxidation treatment of carbon/carbon composites and deposition of strong bonding calcium phosphate coatings on the treated substrate

This work described the ultrasound assisted anodic oxidation treatment of carbon/carbon (C/C) composites with H₃PO₄ which aims to create a chemical bonding between the surface-treated C/C composites and subsequently deposited calcium phosphate (CaP) coatings. The results revealed that the surface energy of C/C which had experienced the ultrasound assisted anodic oxidation treatment with 0.5 M H₃PO₄ at the current density of 50 mA/cm² (USAT-C/C-50) (93.31 mJ/m₂) was much higher than that of untreated C/C (10.43 mJ/m²). And the high content of O-containing groups and some amounts of P-containing groups were obtained on the USATC/C-50. When the USAT-C/C-50 was used as the substrate of CaP coatings deposited by ultrasound assisted electrochemical deposition (USECD), the surface of USAT-C/C-50 turned to have a strong CaP induction ability and large amounts of CaP were deposited on it in the initial deposition process. After USECD, very strong CaP coatings were formed on USAT-C/C-50. The average of shear bond strength of the coatings obtained on the USAT-C/C-50 (12.14±1.30 MPa) was about two times of the coatings obtained on the untreated C/C (6.78±1.06 MPa).