Preparation Of Calcium Phosphate: Process Optimization And Phase Transformation During Aging

Calcium phosphate material has a wide uses in human hard tissue(teeth and bone ideal alternative materials)for its good biodegradability,biocompatibility and nontoxic,which now has become a hot research field in industry.This work focused on the production technology of tricalcium phosphate and the crystal form transformation during the process.Tricalcium phosphate has an amorphous state.And there are two crystal forms of tricalcium phosphate existing at room temperature,which are ?-type(high-temperature type)and ?-type(low-temperature type),the crystal transition temperature is 1180 ?.In the preparation of tricalcium phosphate crystals,amorphous calcium phosphate(ACP)may present momentarily in aqueous solution,and it is difficult to obtain stable ACP product.Among them,the preparation of ?-tricalcium phosphate(?-TCP)which is most widely used is the most economical.In this article,the crystalline form of tricalcium phosphate was studied under different experimental conditions,and X-ray diffractometer(XRD)was used to determine the crystalline phase of the synthesized compounds.A simple route for synthesizing ?-tricalcium phosphate(?-TCP)has been developed in methanol solvent.And ethanol solvent can effectively inhibit the crystallization of amorphous calcium phosphate(ACP).Simultaneously,the crystallization rate of amorphous calcium phosphate(ACP)was determined under different water and ethanol volume ratios.The stable ACP products can be get under PEG in the polyethylene glycol solution,followed by the best dosage of PEG.The reaction of polyethylene glycol(PEG)and calcium ion was discussed by the SEM image of products and the pH value of the solution.The effect of aging time on the solid performances of tricalcium phosphate was investigated by using XRD to identify the degree of crystallinity,and SEM to observe the crystal morphology.The Malvern particle size analyzer was also applied to measure the distribution of the particle size of tricalcium phosphate.It is found that the amourphous precipitation is initially produced,and then transforms to the crystal product during the aging process.The purity of the product during the aging process will be correspondingly increased.The crystallization of calcium phosphates into crystalline tricalcium phosphate is accompanied with a slight decrease of the pH of the solution.According to the SEM image,the final morphology of the product is flake like aggregated crystals;with the increasing of aging time,small particles gradually dissolve,and larger particles gradually grow up,which leads to an arrow particle size distribution.In the preparation of feed-grade tricalcium phosphate by chemical precipitation,the crystallization process of tricalcium phosphate was optimized.The effects of pH,stirring speed and drying conditions on the crystalline product yield,final particle size distribution and crystalline quality were investigated,followed by the determination of optimum conditions for tricalcium phosphate crystallization process.Study on the quality and safety characteristics of feed-grade tricalcium phosphate,included free water,calcium,total phosphorus,fluoride and the number of crystal.Those quality and safety characteristics meet the standards of feed-grade tricalcium phosphate.