水氯镁石是一种非常具有应用前景的镁盐资源, 其储量丰富, 成本低廉。以青海盐湖水氯镁石和水玻璃合成不同MgO/SiO2摩尔比(0.5∶1, 1∶1, 1.5∶1)的水合硅酸镁(M-S-H)凝胶, 采用XRD、SEM、红外和核磁共振等测试手段研究M-S-H的合成机理和结构特征, 进而将合成的M-S-H与硅微粉复合制备镁质浇注料, 探究M-S-H结构对浇注料结合特性的影响规律。结果表明: 不同MgO/SiO2摩尔比的M-S-H呈层状堆叠结构, MgO/SiO2摩尔比为1∶1时M-S-H的层间自由水少, 结晶度最高; M-S-H替代部分硅微粉制备镁质浇注料能显著提高1 550 ℃热处理后浇注料的力学性能, 其中MgO/SiO2摩尔比为1∶1的M-S-H复合硅微粉制备的镁质浇注料综合性能最佳, 与添加6%(质量分数)硅微粉制备的镁质浇注料相比, 其常温抗折强度和高温抗折强度分别提高75%和8%。

Bischofite is a very promising magnesium salt resource with abundant reserves and low cost. Magnesium silicate hydrate (M-S-H) gels with different MgO/SiO2 molar ratios (0.5∶1, 1∶1, 1.5∶1) were synthesized using bischofite from Qinghai Salt Lake and sodium silicate. The synthesis mechanism and structural characteristics of M-S-H were studied by XRD, SEM, infrared, and nuclear magnetic resonance tests. Then, the synthesized M-S-H was compounded with microsilica to prepare magnesia castable, and the influence of M-S-H structure on the bonding characteristics of castable was explored. The results show that M-S-H obtained from different MgO/SiO2 molar ratios exhibits a layered stacking structure. When the MgO/SiO2 molar ratio is 1∶1, the interlaminar free water is the least and the crystallinity is the highest. The synthesized M-S-H is used to replace part of microsilica to prepare magnesia castable, which significantly improves the mechanical properties of the castable after heat treatment at 1 550 ℃. The magnesia castable prepared with M-S-H (MgO/SiO2 molar ratio of 1∶1) and microsilica obtains the best comprehensive properties. Compared with the magnesia castable prepared by adding 6% (mass fraction) microsilica, the flexural strength at room temperature and high temperature increases by 75% and 8%, respectively.