Nanometer magnesium oxide is a new kind of inorganic functional material, widely used in ceramic materials, catalysts, electrical insulation materials, cosmetics, Refractory, Superconductor classification, rubber fillers, acid gas adsorbents, catalyst carriers and other fields, it can also be used as radar absorbing material and antibacterial material, which has broad application prospects and huge economic potential.
In this paper, nano-sized magnesia powder was prepared by hydrothermal method with inorganic magnesium salt as raw material, and the effect of reaction medium on the morphology of nano-sized magnesia powder was discussed, the sintering mechanism of Spark Plasma Sintering (SPS) of nano-sized magnesia powder was studied, and the mechanical properties of solidified nano-sized magnesia ceramics were tested, at the same time, the catalytic performance of nano-mgo powder thermal decomposition ammonium perchlorate (AP) was systematically analyzed. The effects of technological parameters, such as the molar ratio of precipitator to Mg2 + , hydrothermal reaction time and hydrothermal reaction temperature, on the yield, average particle size and morphology of nano-oxide powders were analyzed by orthogonal experiment, the optimum conditions of preparing nano-oxide powder were determined as follows: the ratio of precipitator to Mg2 + was 2:1, the hydrothermal reaction time was 3 h and the hydrothermal reaction temperature was 160 °C.
The calcination temperature of precipitator and precursor for preparing nanometer magnesia powder was determined by single-factor experiment. The effects of EDTA and KCL as reaction media on the morphology and structure of nano-oxide powders were investigated. After adding EDTA or KCL into hydrothermal reaction system, the morphology of nano-mgo powder changed from hexagonal sheet to nearly circular sheet, and the crystal structure was still face-centered cubic.
The mechanism of crystal growth was explained by the growth unit theory of anionic coordination polyhedra, and the mechanism of crystal morphology change was discussed. The phase composition and grain morphology of Magnesia bulk ceramics sintered at different temperatures (900 ° C, 1050 ° C, 1200 ° C, 1300 ° C, 1420 ° C) were studied by Spark Plasma Sintering.
Sintering temperature has an important effect on grain growth and ceramic structure. XRD results show that the bulk ceramic materials are all face-centered cubic structure, and the phase composition is single, the sample purity is high. After sintering at different temperatures, the diffraction peaks of each crystal plane become sharp and narrow, which indicates that there is grain growth during sintering. SEM shows that with the increase of sintering temperature, the shape of particles changes from hexagonal sheet to polyhedron, and the interparticle space changes from continuous pore to isolated pore. The kinetic growth index (N) and activation energy (Q) of grain growth at different sintering temperatures were calculated by using the theory of phenomenological dynamics.
The results show that the mechanism of sintering and grain growth is mainly surface diffusion when the sintering temperature is 900 ° C and 1050 ° C, and surface diffusion and plastic flow when the sintering temperature is 1200 ° C The mechanism of sintering and grain growth at 1300 ° C and 1420 ° C is mainly assisted by grain boundary diffusion of plastic flow. The microhardness of mgo ceramics sintered at different temperatures and holding time was measured by Vickers microhardness method, and the bending strength of sintered mgo ceramics sintered at different temperatures was tested by three-point bending test.