Electrolytic depositions of calcium phosphates on substrate

Abstract

Calcium phosphate deposition layers on cathode substrates were prepared by electrolysing acidic Ca(H₂PO₄)₂·H₂O (MCP) solutions of 0.02–0.21 mol dm⁻³ added with and without NaNO₃ at cathode currents of 2–200 mAcm⁻² at 20–90 °C. At relatively high MCP concentrations and low currents, CaHPO₄·2H₂O and CaHPO₄ plate-like crystals were deposited below and above ∼30 °C, respectively. With increasing current, the deposits became fine. On further increasing the current and/or decreasing the MCP concentration, apatite deposition occurred. The addition of NaNO₃ facilitated the formation of apatite. Deposited apatites were very fine grains and had a calcium-deficiency of ∼1.50 in the Ca/P molar ratio.