Abstract: To clarify the influence of calcium hydroxide on the morphology of calcium sulfate hemihydrate hydrothermal products in the magnetized water system, scanning electron microscopy (SEM), conductivity analysis, and X-ray diffraction (XRD) were used to characterize the calcium sulfate hemihydrate samples. On this basis, the effect mechanism of calcium hydroxide on hydrothermal products of calcium sulfate hemihydrate crystal morphology was clarified. The results revealed that calcium hydroxide with different concentrations had an extremely significant regulatory effect on the morphology of hydrothermal products of calcium sulfate hemihydrate in the magnetized water system. With the increment of calcium hydroxide concentration, the morphology of hydrothermal products first changed from fibrous to plate-like, then to columnar. In this process, granular morphology was observed, which may be a mixture of calcium hydroxide and calcium sulfate dihydrate crystals. When the concentration of calcium hydroxide was 5.0×10-7 mol/L, hydrothermal products mainly existed as fibrous. With calcium hydroxide concentration increased to 5.0×10-5 mol/L, Ca2+ inhibited the dissolution of calcium sulfate dihydrate through the common ion effect, resulting in a diminishing of SO42- in the solution. Meanwhile, OH- and SO42- competitively adsorbed on the (002) crystal plane of calcium sulfate hemihydrate crystal in the form of chemical adsorption, which was not conducive to the precipitation of growth components on the crystal plane and led to the morphology transition from fibrous to plate-like. With the concentration of calcium hydroxide further expanded to 5.0×10-3 mol/L, excessive Ca2+ concentration in the solution was beneficial to the growth of hemihydrate calcium sulfate crystals along (200) and (110) crystal planes, while OH- restrained the growth of hemihydrate calcium sulfate crystals on (002) crystal plane. Beneath the combined influence of the above two factors, calcium sulfate hemihydrate transformed into columnar. This work provides references for the preparation of calcium sulfate hemihydrate hydrothermal products with different morphologies in magnetized water systems.

Key words: Magnetized water system, calcium hydroxide, calcium sulfate hemihydrate, common ionic effect, crystal morphology

摘要： 为掌握在磁化水体系中氢氧化钙对半水硫酸钙水热产物形貌的影响规律，采用扫描电镜(SEM)、电导率和X射线衍射(XRD)等方法对半水硫酸钙试样进行表征，在此基础上阐明氢氧化钙对其形貌的影响机理。结果表明，在磁化水体系中氢氧化钙对半水硫酸钙水热产物的形貌有明显的调控作用。随氢氧化钙浓度增大，水热产物的形貌由纤维状先转变为板状，后转变为柱状，并且在此过程中，有少量颗粒状形貌产物出现，其可能是氢氧化钙和二水硫酸钙晶体的混合物。当氢氧化钙的浓度为5.0×10-7 mol/L时，水热产物的形貌主要为纤维状。随着氢氧化钙浓度的增加，当其浓度为5.0×10-5 mol/L时，Ca2+通过同离子效应抑制二水硫酸钙溶解，导致SO42-数目减少，同时，OH-与SO42-产生竞争吸附并以化学吸附的形式作用于半水硫酸钙晶体的(002)晶面，不利于生长组元在该晶面的沉淀，导致晶体形貌向板状转化。当其浓度为5.0×10-3 mol/L时，溶液中过大的Ca2+浓度有利于半水硫酸钙晶体沿(200)和(110)晶面生长，而OH-抑制(002)晶面生长，在二者共同作用下，晶体形貌转变为柱状。研究可为磁化水体系中制备不同形貌半水硫酸钙水热产物提供一定的参考意义。

关键词: 磁化水体系, 氢氧化钙, 半水硫酸钙, 同离子效应, 晶体形貌