磷酸镁的相转变过程研究

Study of the phase transition process of magnesium phosphate

考察镁磷比、pH以及培养时间对磷酸镁的形成和相转变的影响。采用^(31)P NMR,IR与Raman技术监测了磷酸镁的相转变过程,并通过XRD对磷酸镁的晶型物相等进行了表征确定。结果表明:当pH值为9.0时,30 min即可生成Mg_(3)(PO_(4))_(2)·5H_(2)O;pH小于8.0时,一开始形成MgHPO_(4)·3H_(2)O,延长反应时间可经由Mg_(2)(PO_(4))(OH)·3H_(2)O向Mg_(3)(PO_(4))_(2)·5H_(2)O相转变。在pH为7.4的环境中,镁磷比为1时,可从最先形成的MgHPO_(4)·3H_(2)O向Mg_(3)(PO_(4))_(2)·5H_(2)O转变;镁磷比为0.25和0.67时,可生成Mg_(3)(PO_(4))_(2)·5H_(2)O;镁磷比为4时,由于镁离子浓度过大,在反应24 h后,保持MgHPO_(4)·3H_(2)O的稳定相。

The influence of magnesium ion to phosphorus ratio(denoted as Mg/P),initial pH and incubating time on MgPs phase transition are investigated.The phase transition processes of the MgPs were monitored by ^(31) P NMR,IR and Raman technology,and the obtained crystal formations of magnesium phosphate were characterized by XRD.The results show when the pH is 9.0,Mg_(3)(PO_(4))_(2)·5H_(2)O can be generated in 30 min.When the pH is less than 8.0,MgHPO_(4)·3H_(2)O is formed at the onset stage.Then Mg_(3)(PO_(4))_(2)·5H_(2)O phase could be formed from Mg_(2)(PO_(4))OH·3H_(2)O.With the initial pH at 7.4,MgHPO_(4)·3H_(2)O is generated,then transform to Mg_(3)(PO_(4))_(2)·5H_(2)O with the Mg/P ratio at 1 in the incubating solution,however,Mg_(3)(PO_(4))_(2)·5H_(2)O can be formed with Mg/P at 0.25 and 0.67.When the Mg/P ratio is set at 4,the MgHPO_(4)·3H_(2)O phase could be kept for 24 h due to the contribution of the excessive magnesium ions.