Fabrication of hydroxyapatite block from gypsum block based on (NH4)2HPO4 treatment.

基于磷灰石在热力学上比石膏更稳定这一事实，本研究的目的是评估用石膏作为前驱体制备低晶多孔磷灰石块的可行性。转化反应由于与磷酸盐离子的离子交换导致硫酸盐离子的释放，从而导致溶液的pH值降低。然后，由于pH值降低，无水磷酸二钙（在较低pH值下具有相似的热力学稳定性）也作为副产物产生。在这种方法中形成的磷灰石是低结晶的，多孔的b型碳酸盐磷灰石，含有大约0.5 wt%的CO3，即使没有碳酸盐源-除了空气中的二氧化碳-加入到反应系统中。由于b型碳酸盐磷灰石是骨中含有的生物磷灰石，因此我们认为这是一种有用的骨填充物制备方法。

The aim of this study was to evaluate the feasibility of fabricating low-crystalline, porous apatite block using set gypsum as a precursor based on the fact that apatite is thermodynamically more stable than gypsum. The transformation reaction caused a release of sulfate ions due to an ion exchange with phosphate ions, thus leading to a decrease in the pH of the solution. Then, due to decreased pH, dicalcium phosphate anhydrous--which has similar thermodynamic stability at lower pH--was also produced as a by-product. Apatite formed in the present method was low-crystalline, porous B-type carbonate apatite that contained approximately 0.5 wt% CO3, even though no carbonate sources--except carbon dioxide from air--were added to the reaction system. We concluded therefore that this is a useful bone filler fabrication method since B-type carbonate apatite is the biological apatite contained in bone.