Mg<sup>2+</sup>对半水硫酸钙晶须结晶习性的影响

本文以磷石膏为原料蒸压制备半水硫酸钙晶须, 采用数字显微镜、X射线衍射(XRD)和X射线光电子能谱(XPS)等微观测试方法对Mg2+作用下的半水硫酸钙晶须微观形貌、组成及晶面发育情况等进行试验研究, 运用分子动力学技术模拟计算Mg2+在半水硫酸钙晶体晶面的相互作用能和径向分布函数, 两者结合探讨Mg2+对半水硫酸钙晶体不同晶面结晶习性的影响。结果表明, Mg2+和半水硫酸钙晶体不同晶面的相互作用能从小到大顺序为: ΔE(200)<ΔE(002)<ΔE(400)<ΔE(020)<ΔE(204), 即Mg2+主要吸附在半水硫酸钙晶体的(200)、(002)、(400)晶面上。Mg2+与SO2-4间的作用距离小于Ca2+与SO2-4间的作用距离, Mg与S之间产生了明显的电子效应, 且电子效应随硫酸镁掺量的增加而增强, XRD衍射峰位置随硫酸镁掺量的增多向右偏移变得更加明显, 说明有少量的Mg2+嵌入半水硫酸钙晶格。在硫酸镁掺量0.15%(质量分数, 下同)时, 优先促进晶体c轴方向的生长, 使半水硫酸钙晶须呈细长针状, 平均长度为47.29 μm, 平均长径比为36.07; 在硫酸镁掺量为0.30%时, 抑制晶体沿c轴和径向的生长, 使半水硫酸钙晶须呈细短针状, 平均长度为39.72 μm, 平均长径比为28.91。

Abstract

In this paper, calcium sulfate hemihydrate whiskers were prepared by autoclaving using phosphogypsum as raw material. Digital microscope, X-ray diffraction (XRD) and X-ray photoelectron spectrometer (XPS) were used to investigate the microscopic morphology, composition and crystal surface development of calcium sulfate hemihydrate whiskers under the effect of Mg2+. Using molecular dynamics technology to simulate the interaction energy and radial distribution function of Mg2+ in the crystal surface of the calcium sulfate crystal. The effect of Mg2+ on the crystallization habits of calcium sulfate crystals was explored by combining the two techniques. The results show that the interaction energies of Mg2+ and different crystal faces of calcium sulfate hemihydrate crystals from smallest to largest are listed below: ΔE(200)<ΔE(002)<ΔE(400)<ΔE(020)<ΔE(204), which illustrates that Mg2+ is mainly adsorbed on the (200), (400) and (002) crystal faces of calcium sulfate hemihydrate crystals. The interaction distance between Mg2+ and SO2-4 is smaller than that between Ca2+ and SO2-4. There is an obvious electronic effect between Mg and S, and the electronic effect is enhanced with the increase of magnesium sulfate content. The position of XRD diffraction peak is more obvious to the right with the increase of magnesium sulfate. All indicate that a small amount of Mg2+is embedded in the crystal lattice of calcium sulfate hemihydrate. At 0.15% (mass fraction, the same as below) of magnesium sulfate content, the growth of c-axis direction was preferentially promoted, resulting in slender needle-like calcium sulfate hemihydrate whiskers with an average length of 47.29 μm and an average L/D ratio of 36.07. At 0.30% of magnesium sulfate content, the growth of c-axis and radial direction was inhibited, resulting in slender needle-like calcium sulfate hemihydrate whiskers with an average length of 39.72 μm and an average L/D ratio of 28.91.

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王青, 刁华利, 刘冬梅, 张典, 徐港. Mg²⁺对半水硫酸钙晶须结晶习性的影响[J]. 人工晶体学报, 2023, 52(10): 1897. WANG Qing, DIAO Huali, LIU Dongmei, ZHANG Dian, XU Gang. Effect of Mg²⁺ on Crystallization Habit of Calcium Sulfate Hemihydrate Whiskers[J]. Journal of Synthetic Crystals, 2023, 52(10): 1897.

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