The Preparation And The Study On The Properties Of The Calcium Sulfate/Calcium Phophate Bioceramics

In this paper, liquid deposition was used for preparing calcium sulfate crystals. The composite powders of calcium sulfate/hydroxyapatite and calcium sulfate/β- tricalcium phosphate were respectively prepared by using co-precipitation and ball milling. The composite powders were compacted to green bodies and then sintered. Calcium sulfate crystals, calcium sulfate/hydroxyapatite and calcium sulfate/β-tricalcium phosphate composites were immersed in Tris, which can be used for evaluating degradation behaviors of biomaterials. The calcium sulfate shape was studied by optical microscope; the composite powders were studied by XRD and the morphologies of composites before and after degradation were studied by SEM. Weight loss was calculated.1. The effects of pH value and temperature of solutions on calcium sulfate shape were analyzed depended on theory of crystal growth and crystal structure of CaSO₄·2H₂O. The calcium sulfate shape is mainly depended on the combining of H₂O and Ca²⁺. The breaking down of bond between H₂O and Ca²⁺ also affects the shape of sintered CaSO₄ and the weight loss of CaSO₄·2H₂O.2. The phase of calcium sulfate/hydroxyapatite composite powders were studied by theory of multi-component dissociation of phosphoric acid and precipitation reaction and thermal reaction of phosphate. The preponderant component of phosphate in the solution determines phase composition of the composite powder. Calcium sulfate releases Ca²⁺ that supplies the need of precipitation reaction of phosphate. The weight loss and pores of composites after degradation is affected by residual calcium sulfate.3. Degradation and resorption models, one tells us what affect degradation rate and the other depict resorption proceed layer by layer, were suggested in this paper. Interpretation of degradation were given using the models and the morphologies of composites. Pores are very helpful to degradation. It is easy for the composites have more calcium sulfate to interconnect and enlarge the pores. The resorption proceed layer by layer happens on pureβ-tricalcium phosphate.