THE EFFECT OF ALKALI TREATMENT ON THE MORPHOLOGY OF CALCIUM PHOSPHATE COATINGS DEPOSITED ON A TI-6AL-4V SUBSTRATE BY AN ELECTROLYTIC METHOD

摘要

Since the bioenvironment in the human body is very complicated, metallic implants could interact with surrounding tissues and then cause corrosion. Clinical experience has shown that they are susceptible to localized corrosion in human bodies causing the release of metal ions into the tissues surrounding the implants. Hence biocompatible and corrosion-resistant layers are normally coated on alloys. Many efforts have been made in recent years in the development of processing methods for depositing hydroxyapatite (HAP) on implant alloy substrates such as Ti-6Al-4V in order to have high strength, suitable specific density, good process ability, and excellent corrosion resistance in living bodies. HAP is the most interesting form of calcium phosphate to be electrochemically deposited (ECD) from several solutions at elevated temperatures. Silva et. al. [1] have deposited calcium phosphates (MCP, DCPD) on the Ti-6Al-4V alloy by ECD, and discussed the phase transformation of deposits in various alkali solutions, such as KOH, NH{sub}4OH and NaOH. Wang et al. [2] have reported that HAP is found to form at 10V 60°C and 80 Torr for 1h in the ECD process The main objective of this study is to investigate the effect of NaOH{sub}(aq) immersion treatment on the phase transformation of the calcium phosphate deposited on the Ti-6Al-4V substrate. The ECD process has been used at 60°C, 10V for 1h in the 0.04 M MCPM aqueous solution, followed with the immersion treatment in different concentrations of NaOH{sub}(aq) and temperatures for 1h. The morphology and physical properties have been carefully investigated by XRD, FT-IR, SEM, and TEM.