水热法合成白磷钙石

Hydrothermal Synthesis of Whitlockite

以CaO、Mg(NO_3)_2和H_3PO_4为原料,通过水热法合成白磷钙石。采用X射线衍射(XRD)、场发射扫描电子显微镜(SEM)、热分析(TG-DTA)和X射线荧光光谱(XRF)进行了分析表征。结果表明,随着初始溶液中Mg/(Ca+Mg)摩尔比的增加,白磷钙石的结晶行为有显著不同:形貌由六方板状晶体(直径30~50μm)向球形聚集体(直径3~5μm)转变,晶胞参数a和c值则逐渐减小。初始溶液中Mg/(Ca+Mg)增加,产物中的Mg/(Ca+Mg)含量也逐渐增加,Mg/(Ca+Mg)的最高值为13.6%。在实验条件下,白磷钙石的成核与结晶过程在2 h之内基本完成。白磷钙石Ca_(18)Mg_2H_2(PO_4)_(14)在680~950℃之间脱去结构水,转变为Ca_(18)Mg_2(PO_4)_(12)P_2O_7。

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 μm） to spheres（about 3–5 μm） 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. Ca（18）Mg2H2（PO4）（14） was transformed to Ca（18）Mg2（PO4）（12）P2O7 after calcination at temperature ranging from 680℃ to 950℃ due to the dehydration reaction.