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以电熔尖晶石、Si粉和鳞片石墨为主要原料,木质磺酸钙溶液(1.25 g/mL)为成型结合剂,在氮气气氛下1450℃分别保温1、2、3和4 h原位生成β-Sialon结合Mg Al_2O_4-C材料,研究了保温时间对材料的物相组成、β-Sialon的显微结构及常规物理性能的影响,并对该复合材料进行氧化动力学研究。结果表明:当保温时间从1 h增加到4 h,试样的物相变化规律基本相同,Si单质相消失,完全转化为SiC、Si_3N_4和β-Sialon(Si_3Al_3O_3N5)。当保温时间为3 h时,生成的β-Sialon(Si3Al3O3N5)为完整圆柱状晶粒,尺寸分布均匀,交错成网络结构。随着保温时间的增加,试样内部产生较多的SiO气体,导致试样的显气孔率增加,体积密度下降,耐压强度和抗折强度先增加后下降,当保温时间为3 h时,耐压强度和抗折强度达到最大。氧化动力学研究表明,氧化过程随着时间的推移分为化学反应控制阶段、化学反应和扩散共同控制阶段及扩散控制三个阶段。
Using fused spinel, Si powder and flake graphite as the main raw materials, calcium lignosulfonate solution (1.25 g / mL) was used as a molding binder and incubated at 1450 ℃ for 1, 2, 3 and 4 h in nitrogen atmosphere Β-Sialon and Mg Al 2 O 4-C were synthesized. The effect of holding time on the phase composition, the microstructure and the physical properties of β-Sialon were studied. The oxidation kinetics of the composite was also studied. The results show that when the holding time is increased from 1 h to 4 h, the phase transformations of the samples are basically the same, and the Si simplex phase disappears and completely transformed into SiC, Si_3N_4 and β-Sialon (Si_3Al_3O_3N5). When the holding time is 3 h, the formed β-Sialon (Si3Al3O3N5) is a complete columnar grain with uniform size distribution and staggered into a network structure. With the increase of holding time, more SiO gas was generated inside the sample, which resulted in the increase of apparent porosity, bulk density, compressive strength and flexural strength firstly increased and then decreased. When the holding time was 3 h, Compressive strength and flexural strength to achieve maximum. Oxidation kinetics studies show that the oxidation process over time divided into chemical reaction control stage, the chemical reaction and diffusion of the common control phase and diffusion control of three stages.