3.1. Synthesis of CoHA

The CoHA powder was prepared by electrochemical deposition [21]. The electrolyte solution was formulated with 42 mM calcium nitrate (Shimakyu’s pure chemical, Osaka, Japan), 25 mM ammonium dihydrogen phosphate (Showa, Tokyo, Japan), and 7.98 mM cobalt chloride (Shimada chemical works, Tokyo, Japan) in de-ionized water. The titanium sheet was a cathode, the stainless-steel sheet was an anode. The electrodeposition procedure was carried out with a direct current power supply (GR-50H10, GICEK, Taipei, Taiwan) and at constant potential by 5.5 V at 328 K for 20 min. After the reaction was completed, rinsed with deionized water and dried, the powder was removed from the surface and collected.