自石灰石矿粉中直接提取CaCO3晶须的碳化-分解法研究

Direct Extraction of CaCO_3 Whiskers from Limestone Powders by a Combined Method of Carbonation and Thermal Decomposition

提出一种自石灰石矿粉中直接提取CaCO_3晶须的碳化-分解方法。该方法能够以天然石灰石矿粉为原料,通过水溶性碳酸的作用溶解出Ca(HCO_3)_2,进而在升温条件下通过Ca(HCO_3)_2的分解反应得到形貌规整的棱锥状CaCO_3晶须。扫描电镜观测与X射线衍射分析显示,Ca(HCO_3)_2分解温度对CaCO_3晶须微观形貌的影响显著,晶须长度与长径比随分解温度的升高均呈上升趋势,但分解温度超过80℃会导致文石晶相向方解石晶相转化。实验结果表明,80℃、2h条件下,Ca(HCO_3)_2分解产物中文石晶相含量较高,晶须几何形貌更为合理,其平均长度为14.61 μm、长径比为8.10。

With a purpose of realizing the low-cost production of CaCO3 whiskers,a feasible way was proposed in this work by making use of natural limestone powders as the starting material,which was transferred partly into Ca（HCO3）2 due to the contribution of CO2 dissolved in water.Once the soluble Ca（HCO3）2 decomposed under elevated temperature ranged from 60 ℃ to 90 ℃ ,CaCO3 whiskers with a uniform morphology of short needle were obtained.According to the observations under scanning electron microscope（SEM）,along with the analysis based on X-ray diffraction（XRD）,the great contribution of decomposition temperature was revealed,and as a result,both the length and aspect ratio of such CaCO3 whiskers increased evidently with the increase of decomposition temperature.Further increase of the decomposition temperature above 80 ℃ gave rise of the transformation of aragonite to calcite.The experimental results suggested the most promising conditions for the production of CaCO3 whisker,i.e.,80 ℃ ,2 h,which was effective to obtained CaCO3 whisker with an average length of 14.61 μm and an aspect ratio about 8.10.