Crystallographic Characterization and Themal Decomposition Behavior of High-Purity Microcrystalline Magnesite
The intergranular cracking face is smooth and transgranular cracking fracture shows trace of cleavage. It is hard to find characteristic rhombus in the dense small crystals.As measured by SEM, the particle size of microcrystalline magnesite originating in Sichuan-Tibet is uniform, most grains range in 2-4 μm. Three-dimensional (3D) crystal morphology assumes cubic or column. The result of chemical analysis shows that the microcrystalline magnesite has high purity and XRD indicates that the lattice constant is the same as macrocrystalline magnesite with standard d values and X-ray diffraction intensity. The decomposition temperature is 650 ℃ determined by DTA, which is also the same as macrocrystalline magnesite. Crystal morphology of nanometer periclase treated at 650 ℃ for 4 h and calcined at 1 000 ℃ respectively was observed by FE-SEM, the grain of periclase fired at 650 ℃ is <20 nm and that of the periclase calcined at 1 000 ℃ is <200 nm, both are round. The quality of high purity magnesite manufactured by high temperature shaft kiln is at the same level as sea water magnesite made in Japan and brine magnesite produced in the Netherlands, while the crystal size is slightly larger.