通过ＳＥＭ显微技术，从亚微观结构研究Ｎａ５Ｐ３Ｏ１０对Ｃａ（ＯＨ）２碳化反应中ＣａＣＯ３结晶的控制生长过程．结果表明，ＣａＣＯ３结晶的成核、生长在时间上是重叠的伴随过程．在ＣａＣＯ３反应结晶的起始阶段，Ｎ５Ｐ３Ｏ１０的存在促进了ＣａＣＯ３的大量成核．通过ＳＥＭ可以观测到大量正稳态 ＣａＣＯ３籽晶（Ｒ＝ ２３～２６ｎｍ）的存在.这时， ＣａＣＯ３晶体生长并不符合Ｚｅｎｅｒ－Ｈａｍ理论的扩散生长规律．结晶生长由穿越晶体界面的短程扩散控制．在反应结晶末期，ＳＥＭ已观测不到亚稳态ＣａＣＯ３籽晶的存在．ＣａＣＯ３结晶生长遵循长程扩散控制模型Ｒ（ｔ）＝（Ｄｔ）ｎ，时间指数ｎ＝０．４８７４～０．４９９２（理论值ｎ＝０．５）．随着碳化液中Ｎａ５Ｐ３Ｏ１０浓度的增大，常数λi Dｎ由１６．６９降低至１１．３６，从而有效地控制ＣａＣＯ３的结晶生长．
The ultrafine CaCO3 crystal growth controlled by Na5P3O10 in the carbonation of Ca(OH)2 suspension, was investigated by using SEM.
The results show that CaCO3 nucleates along with the nucleus growth. The presence of Na5P3O10 accelerates the CaCO3 nucleation. At the
initial stage, a large number of CaCO3 nucleus engender, and metastable tiny crystallites (R=23～26nm) can be observed in SEM imagine. The CaCO3 crystal
growth controlled by short distance diffusion when mass pass through the crystal interface, does not correspond to Zener-Ham theory. At the next stage, the metastable
tiny crystallites disappear in SEM imagine. The CaCO3 crystal growth abides by the long distance control model R(t)=λi(Dt)n, in which the time coefficient
n is 0.4874～0.4992 (theory value n=0.5) and the constant λi Dn decreases from 16.69 to 11.36. Consequently, Na5P3O10 can effectively inhabit the CaCO3 crystal growth.
参考文献
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