Study On Sintering Behavior And Properties Of Silicon Carbide Ceramics With Rare-Earth Non-oxide Additives

With series excellent properties of high melting point, high hardness, corrosion resistance, abrasion resistance, low expansion coefficient and other, Si C advanced engineering ceramics is the most promising one for industrial application. This article introduces the structure, properties and applications and several preparation methods of Si C, and emphatically introduces the research progress of the sintering of Si C ceramics. The non-pressure sintering method is more wide-ranging than the others, and has great research value. In this paper, the effects of the experimental parameters, such as sintering additives, sintering temperature and doping concentration on the microstructure, dielectric coefficient and expansion coefficient of Si C ceramic materials were prepared by the non-pressure sintering method. The main research contents are as follows.In this paper, we study the surface morphology of Si C ceramics using Y₂O₃-Al₂O₃-Mg O as sintering aids under different sintering temperature. The micro structure of the crystal structure and surface of ceramic samples were tested and analyzed in this paper. The results show that, compared to without pre oxidation of the sample, the one after pre oxidation treatment has more pores and loss of sintering quality. Both the samples are in the Y3Al5O12 phase（YAG）.In this paper, silicon carbide ceramic samples prepared by different mass ratio of Nd OCl/Mg O whose mass fraction is 9%, and the tests of the samples crystal structure and micro structure of the surface are analyzed. The conclusion is that the porosity of the sample has a decreasing trend with the increase of the mass ratio of Nd OCl/Mg O, the value of relative dielectric constant and loss ratio of the Nd OCl/Mg O whose mas ratio is 2:7 were smaller than the value of the sample with the ratio 4:5, and the loss of the two ones are linear with the change of temperature.In this article, we also study the preparation process of Si C composite ceramics with La F₃+Mg O as sintering aids whose mass fraction is 5% or 11% under the temperature 1800 ℃in liquid phase. We test the phase composition, micro morphology and thermal expansion properties of the samples by XRD and SEM. In other word, we find that the sample whose sintering additives mass fraction is 11wt% has larger grains gap and thermal expansion coefficient, and clearer crystal edges than the one with the sintering additives mass fraction 5%.