Decomposition and solid reactions of calcium sulfate doped with SiO2, Fe2O3 and Al2O3
Decomposition and solid reactions of calcium sulfate doped with SiO2, Fe2O3 and Al2O3
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SiO2、Fe2O3、Al2O3掺杂硫酸钙的分解与固相反应
DOI：
10.1016/j.jaap.2015.03.019
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发表时间：
2015-05
影响因子：
6
通讯作者：
Qiu, Jianrong
中科院分区：
文献类型：
--
作者：
Tu, Yaojie;Yang, Wei;Zeng, Hancai;Qiu, Jianrong
通过热重分析研究了SiO2、Fe2O3和Al2O3对硫酸钙(CaSO4)分解的影响，并通过X射线粉末衍射分析了CaSO4与SiO2、Fe2O3或Al2O3混合时高温反应产物的矿相组成。此外，还讨论了CaSO4与氧化物之间的固相反应以及CaSO4与Fe2O3混合前后的分解动力学。实验结果表明，CaSO4的分解与其晶体结构转变相关，CaSO4失稳的敏感温度范围为1473~1523 K。从整体热重分析结果来看，SiO2、Fe2O3和Al2O3等添加剂均能加速CaSO4的分解。添加SiO2后，由于SiO2与CaO发生固相反应，形成硅酸盐矿物，降低了CaSO4的起始分解温度，而1473 K以上生成的硫硅酸钙在一定程度上抑制了CaSO4的分解。添加Fe2O3后，CaSO4的分解主要是通过Fe离子扩散来促进的。添加Al2O3时，CaSO4的分解在第一阶段通过形成铝酸钙而加速，在形成硫铝酸钙后阻止CaSO4的分解。热分解动力学机理分析表明，纯CaSO4分解的动力学机理为球对称相界反应，而与Fe2O3混合后机理转变为随机成核和后续生长。
The effects of SiO2, Fe2O3and Al2O3on the decomposition of calcium sulfate (CaSO4) were investigated by thermogravimetry, and the mineral phase composition of reaction products at high temperature was analyzed by X-ray powder diffraction when CaSO4was mixed with SiO2, Fe2O3, or Al2O3. Moreover, the solid-phase reactions between CaSO4and the oxides as well as the decomposition kinetics of CaSO4before and after mixing with Fe2O3were well discussed. The experimental results show that the decomposition of CaSO4is correlated with its crystal structure transformation, and the sensitive temperature zone for CaSO4destabilization ranges from 1473 to 1523 K. All the additives including SiO2, Fe2O3and Al2O3can accelerate CaSO4decomposition from the view of whole thermogravimetric analysis results. The initial decomposition temperature of CaSO4can be reduced by the addition of SiO2due to solid-phase reactions between SiO2and CaO, and the formation of silicate mineral, while the formation of calcium sulphosilicate above 1473 K restrains CaSO4decomposition to a certain extent. CaSO4decomposition is promoted mainly by Fe ionic diffusion after adding Fe2O3. For the addition of Al2O3, the decomposition of CaSO4is sped at the first stage by the formation of calcium aluminate, and then prevented after the formation of calcium sulphoaluminate. Thermal decomposition kinetic mechanism analysis indicates that the kinetic mechanism of pure CaSO4decomposition is spherical symmetry phase boundary reaction, while the mechanism changes to random nucleation and subsequent growth after mixing with Fe2O3.
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