PREPARATION OF HYDROXYAPATITE AND CALCIUM PHOSPHATE BIOCERAMIC MATERIALS FROM THE AQUEOUS SOLUTION AT ROOM TEMPERATURE

摘要

A chemical reaction method was used to study the formation mechanism of hydroxyapatite on the surfaces of Ca_3 (PO_4)_3, Ca_3 (PO_4)_3/A1_2O_3, and Ca_3 (PO_4))_3/ZrO_2 ceramic substrates, when these ceramic substrates were chemically reacted with Ca~(2+), PO_4~(3-) and OH~- ions in the different aqueous solutions. With a dipping coating or soaking technique, brushite (dicalcium phosphate dihydrate, CaHPO_4 centre dot 2H_2O) was formed on the surface of ceramic substrate in the phosphate acid solution at pH=2.5. After a subsequent solution treatment in a 2.5M of NaOH aqueous solution at 80 deg C for 1h, brushite coating was converted into hydroxyapatite (HA). Except for the phase change, the morphologies of surface coatings were also progressively changed from the plate-like structure to the network structure as the pH value increased. In the Ca_3 (PO_4)_3/Al_2O_3 and Ca_3 (PO_4)_3/ZrO_2 ceramic substrates, HA was much easier to form on these substrate surfaces after an alkaline solution treatment, if the volume ratio of Ca_3 (PO_4)_3/Al_2O_3 or Ca_3 (PO_4)_2/ZrO_2 in the ceramic substrate was 7/3. As to the effect of basicity, HA was much easier to form on the ceramic substrates at pH=12-14 after a subsequent NaOH-containing solution treatment.