Crystallization Kinetics of Hydroxyapatite Nano-films on Stainless Steel Through a Sol-Gel Process

       This article describes the preparation and analysis of nano hydroxyapatite (HA) films on stainless steel 316L through sol-gel technique. The process started with preparation of a nitrate and phosphate sol. After aging the sol for 24 h at room temperature a SS316 substrate was dip-coated and heat-treated at 350 to 450 °C for different times in air. The coating phase and structure on substrate were investigated by X-ray diffraction (XRD), fourier transform infrared (FT-IR), differential thermal analysis (DTA) and scanning electron microscopy (SEM). Degree of crystallinity and time temperature transformation (TTT) diagram of HA films obtained with using Avrami equation. Results indicated that HA phase began to crystallize after a heat treatment at 250 °C and the crystallinity increased at a temperature of 450 °C. The HA film showed a nano structure with suitable crystallinity after heat treatment.