科研之友
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摘要
Whitlockite was firstly synthesized by a hydrothermal method using CaO, Mg(NO3)(2) and H3PO4 as starting materials and then characterized by X-ray diffraction, scanning electron morphology, thermal analysis, and X-ray fluorescence. The variation of molar ratio of Mg/(Ca+Mg) in the precursor solution resulted in different crystallization behaviors of whitlockite during hydrothermal treatment. With the increase of the molar ratio of Mg/(Ca+Mg), crystal morphologies of products varied from hexagonal plate (about 30-50 mu m) to spheres (about 3-5 mu m) and cell parameters of a and c values decreased gradually. Meanwhile, the content of Mg/(Ca+Mg) in the products increased gradually and reached a high value of 13.6%. It was found that the nucleation and growth of whitlockite were almost completed within 2 h. Ca18Mg2H2(PO4)(14) was transformed to Ca18Mg2(PO4)(12)P2O7 after calcination at temperature ranging from 680 degrees C to 950 degrees C due to the dehydration reaction.
