机械力研磨引起的生物成因文石和方解石的低温可逆相变

REVERSIBLE TRANSFORMATION BETWEEN ARAGONITE AND CALCITE INDUCED BY MECHANICAL MILLING AT LOW TEMPERATURE

采用翡翠贻贝和近江牡蛎为实验样品对生物成因纯文石和方解石矿物进行了1min^10h不同时间段的机械力研磨实验,并采用XRD和SEM对研磨产物进行了系统的分析。结果表明,生物成因的文石和方解石在低温下就可以实现相互相变。其中纯文石在研磨15min后即部分相变成方解石,在研磨1h左右,方解石质量分数达到最大值(约33%)。继续研磨,方解石含量反而会逐步减小直至平衡。相比之下,纯方解石在研磨5h后才出现明显的文石相。继续研磨,文石的含量快速增加,在约6.5h时质量分数即达80%以上,随后文石含量缓慢增加直至平衡。总之,无论原始材料为文石还是方解石,当研磨足够长时间后,研磨产物会达到相同的平衡状态(文石约88%,方解石12%),充分说明在低温下文石与方解石的相变符合勒夏特列原理。

The mechanical milling of biogenic aragonite and calcite was performed at room tem- perature with milling time of 1 min-10 h and the milled products were characterized with XRD and SEM. The results show that the reversible transformation between aragonite and calcite can be realized by milling at low temperature. In fact,the pure aragonite begins to transform into calcite after 15 min milling. On further milling for about 1 h, the calcite proportion amounts to the maximum of about 33% ,however,gradually decreases to an equilibrium value with more than lh milling. In comparison,the pure calcite begins to transform into aragonite only after 5 h milling. On further milling, the aragonite proportion increases rapidly to about 800%, then gradually increases to an equilibrium value after more than 6.5 h milling. The milled products always reach a similar equilibrium value （aragonite-88 %, calcite-12 %） after enough milling time,independent of the original material composition. Therefore, the milling-induced transformation between aragonite and calcite is consistent with Le Chatelierrs principle.