Hebei Messi Biology Co., Ltd. said that magnesium oxide is an important inorganic chemical substance, medical, food, adhesives, rubber, plastics, ceramics, metallurgy, electronics and other industries are of great significance, playing a pivotal role in the national economy. Magnesium oxide with special morphology has a broader market in some areas. Special appearance of magnesium oxide usually can not be prepared directly through the experiment, usually the first preparation of special appearance of the precursor, such as magnesium carbonate or magnesium hydroxide, and then after roasting to get a unique appearance of magnesium oxide. The main raw materials for magnesium products are magnesite and dolomite. In China, these ores are rich in resources, especially magnesite, which occupies an important position in the world’s total reserves and is of high quality, laying a solid material foundation for the development of magnesium salt industry in China.
In this paper, the preparation process of magnesium oxide with different morphology was studied. First of all, we studied the best preparation process of magnesium extracted from magnesite as raw material, as well as prepared spherical magnesium oxide, flaky magnesium oxide and rod-shaped precursor and corresponding magnesium oxide powder by direct precipitation method, and explored the optimal synthesis process, and obtained the optimal conditions for the production of spherical magnesium oxide, flaky magnesium oxide and rod-shaped powder. Finally, the obtained spherical magnesium oxide, flaky magnesium oxide and rod-shaped magnesium oxide powder were filled into the general-purpose plastic PVC, and the effects of the filling amount, morphology and particle size of magnesium oxide in PVC on the thermal conductivity of the material were investigated.
The specific research content is as follows.
(1) Through the calcined thermal decomposition experiment of magnesite, the results show that the magnesite raw material is calcined in the box resistivity at room temperature with the heating rate of 10℃/min to 550℃, 600℃, 650℃, 700℃, 750℃ for 3h, and the magnesite can be decomposed completely at the temperature of 700℃. Comparing the different holding times at 700℃, it was found that it could be decomposed completely after 120min.
(2) Different particle sizes of spherical magnesium oxide powder, flaky magnesium oxide powder and rod-shaped magnesium oxide powder were prepared by changing the reaction temperature, reaction time, concentration of reactants and concentration ratio of reactants in the experiment without adding any additives. Through the analytical characterization of spherical MgO samples by XRD, SEM and particle size analysis, it is shown that by changing different factors in the experiments, morphologically controllable spherical MgO powders, flaky MgO powders and rod-shaped MgO powders can be prepared. Among them, the spherical magnesium oxide particle size is about 4μm-25μm, the flaky magnesium oxide has good crystallinity and good dispersion with uniform particle size; the rod magnesium oxide has smooth powder surface and length is about 20-30μm.
(3) The magnesium oxide obtained after roasting was filled into polyvinyl chloride (PVC), and the thermal conductivity of PVC was characterized after the addition of magnesium oxide. When the addition amount was 40% mass fraction, the thermal conductivity of PVC material filled with rod-shaped magnesium oxide increased by 5.35 times, that of PVC material filled with flake-shaped magnesium oxide increased by 6.88 times, and that of PVC material filled with spherical magnesium oxide increased by 8 times. Meanwhile, compared with the thermally conductive PVC materials prepared from magnesium powder of single particle size, the thermal conductivity of the filled PVC materials increased by 8.35 times when 4 μm magnesium oxide and 25 μm magnesium oxide were compounded with a mass ratio of 1:1 under the same filling mass fraction.