重结晶SiC多孔陶瓷成型及烧结工艺研究

发布时间：2018-04-23 11:50

  本文选题：重结晶烧结SiC + SiC浆料　； 参考：《北京理工大学》2015年硕士论文

【摘要】：重结晶烧结SiC陶瓷材料（Recrystallized Silicon Carbide, RSiC）具有耐高温、硬度高、力学性能优良、开气孔率高，纯度高等优点，十分适合于制备金属/陶瓷双连续相复合材料。制备孔隙率适宜的SiC陶瓷是制备综合性能优异的双连续相复合材料的关键之一，但对获得不同孔隙率的RSiC陶瓷材料以及其微观结构和力学性能的研究较少，针对这方面的空白，本文通过调节制备工艺参数，制备出不同孔隙率的RSiC陶瓷，并对其微观形貌和力学性能进行研究。 RSiC陶瓷烧结为蒸发凝聚机理，必须有不同粒径的SiC颗粒的参与，本文以中位径为140μm和5μm的SiC为原料，采用注浆成型制备RSiC陶瓷坯体，并在气氛烧结炉中进行重结晶烧结制备RSiC陶瓷材料。本文主要研究了分散剂的添加量，浆料PH值对SiC浆料流变性能的影响，确定最优的分散剂添加量和浆料PH值，探讨浆料固相含量对RSiC陶瓷坯体的密度和微观结构的影响；研究了细颗粒的含量、浆料固相含量和烧结温度对RSiC陶瓷的孔隙率，微观结构和力学性能的影响，成功制备出孔隙率在15%-38%的RSiC陶瓷材料。 研究发现，添加0.2wt%的四甲基氢氧化铵（TMAH）作为分散剂，调节浆料PH值至9，可获得流变性能良好，粘度低，触变性好，适合于注浆成型的SiC浆料。调节浆料的固相含量，，发现固相含量70%以下的SiC浆料粘度较低，适合注浆成型，其坯体密度随着固相含量的增加呈现先增大后减小的趋势，当固相含量为67.5%时，坯体致密度最高，可达75%，但微观结构均匀性最好的则是固相含量为65%浆料制备的坯体。 研究表明，通过调节细颗粒的含量和浆料固相含量，可以在较大范围内调节RSiC陶瓷的孔隙率，细颗粒含量为20%-50%，浆料固相含量为60%-69%的范围内，增加细颗粒含量和浆料固相含量都可以降低RSiC陶瓷的孔隙率，提高烧结颈的发育程度，进而提高RSiC陶瓷的力学性能，制备的RSiC陶瓷最高压缩强度和弯曲强度分别为350MPa和115MPa。在2250℃-2350℃进行重结晶烧结，烧结温度对RSiC陶瓷的孔隙率影响不大，随着烧结温度的提高，RSiC陶瓷的力学性能略有提高。
[Abstract]:Recrystallized SiC ceramics (RSCC) have the advantages of high temperature resistance, high hardness, excellent mechanical properties, high porosity and high purity, so it is suitable for the preparation of metal / ceramic dual continuous phase composites. The preparation of SiC ceramics with suitable porosity is one of the key points in the preparation of dual continuous phase composites with excellent comprehensive properties. However, there are few studies on obtaining RSiC ceramics with different porosity and their microstructure and mechanical properties. In this paper, RSiC ceramics with different porosity were prepared by adjusting the process parameters, and their microstructure and mechanical properties were studied. The sintering mechanism of RSiC ceramics must include the participation of SiC particles of different diameters. In this paper, SiC with medium diameter of 140 渭 m and 5 渭 m was used as raw materials to prepare RSiC ceramic billets by grouting molding. RSiC ceramics were prepared by recrystallization sintering in atmosphere sintering furnace. In this paper, the effects of the amount of dispersant and the PH value of slurry on the rheological properties of SiC slurry were studied, the optimum amount of dispersant and the pH value of slurry were determined, and the effect of solid content of slurry on the density and microstructure of RSiC ceramic billet was discussed. The effects of fine particle content, slurry solid content and sintering temperature on the porosity, microstructure and mechanical properties of RSiC ceramics were studied. The RSiC ceramics with porosity ranging from 15% to 38% were successfully prepared. It was found that adding 0.2 wt% tetramethylammonium hydroxide (TMAH) as dispersant, adjusting the PH value of slurry to 9, the SiC slurry with good rheological property, low viscosity and good thixotropy could be obtained. By adjusting the solid content of slurry, it is found that the viscosity of SiC slurry with solid content less than 70% is lower, which is suitable for grouting molding. The density of the slab increases first and then decreases with the increase of solid content. When the solid content is 67.5%, The density of the billet is the highest, up to 75%, but the best microstructure homogeneity is the solid content of 65% slurry. The results show that the porosity of RSiC ceramics can be adjusted in a wide range by adjusting the content of fine particles and the solid content of slurry. The content of fine particles is 20-50 and the solid content of slurry is 60-69%. Increasing the content of fine particles and the solid content of slurry can decrease the porosity of RSiC ceramics, improve the development of sintered neck, and then improve the mechanical properties of RSiC ceramics. The maximum compressive strength and bending strength of the prepared RSiC ceramics are 350MPa and 115 MPA, respectively. Recrystallization sintering at 2250 鈩

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