【作者】 梁斌；

【导师】 才庆魁； 张宁；

【作者基本信息】 沈阳大学 ， 材料学， 2012， 硕士

【摘要】 重结晶碳化硅(R-SiC)陶瓷具有低密度、低热膨胀系数、高熔点、高热导率、高硬度、高强度、耐磨损、耐腐蚀以及优异的抗热震性能等,成为窑具、电热元件、锅炉燃烧器等首选陶瓷材料。R-SiC陶瓷制品的性能主要取决于陶瓷坯体的密度以及微观结构的均匀性,而坯体的密度以及微观结构又取决于碳化硅浆料的固相含量和流变性。为此,本文以制备高固相含量、低粘度且流变性良好的重结晶碳化硅浆料为出发点,重点研究了分散剂四甲基氢氧化铵(TMAH)对碳化硅浆料流变性的影响。从红外光谱、Zeta电位、物相分析、流变性、沉降行为等角度分别研究了分散剂TMAH对重结晶碳化硅细粉及其浆料的稳定分散效果。研究表明,与未添加TMAH的碳化硅粉体表面Zeta电位相比,添加TMAH后,在pH=3～11范围内Zeta电位绝对值明显提高。在重结晶碳化硅细粉浆料中添加0.3wt%TMAH,可以将其固相含量由33vol%提高到60vol%。研究还表明,在本实验条件下,碳化硅粗粉(中位径100μm)和细粉(中位径2.0μm)的最佳粒度级配为7:3。添加0.1wt%TMAH,控制pH在9.63,可以获得最大固含量为70.25vol%的重结晶碳化硅浆料。本文还研究了分散剂TMAH对粗细混合粉体浆料流变性的影响。结果表明,浆料流变曲线在高剪切速率范围内呈现高Newton区;在中低剪切速率范围内浆料呈现剪切变稀行为,粘度与剪切速率之间符合幂律方程。通过拟合得到固相含量为62.5vol%、65.0vol%、67.5vol%、69.0vol%的重结晶碳化硅浆料体系的幂律方程分别为:η=0.354γ-0.3743、η=1.232γ-0.4495、η=1.188γ-0.2867、η=1.513γ-0.2752。这也正是本文的创新之处。固相含量为70.25vol%的浆料经注浆成型后获得的重结晶碳化硅陶瓷坯体的密度为2.37g/cm3。更多还原

【Abstract】 candidate material for kiln furniture, electric heating elements and boiler burners due to its low density and thermal expansion coefficient, high melting point, thermal conductivity, flexural strength and hardness, excellent resistance to thermal shock, abrasion and corrosion. The solid loading and rheological properties of SiC suspensions have considerable influence on the ceramic bulk density and homogeneous microstructure, then having effect on the comprehensive properties of SiC ceramic products. The aim of this investigation was, therefore, to research the influence of tetramethyl ammonium hydroxide (TMAH) used as a dispersant on the rheological properties of SiC suspensions used for recrystallized ceramics to prepare aqueous suspensions with high solid loading, low viscosity and good rheological properties.With TMAH addition, the stable dispersion in both fine SiC powders and suspensions was studied from different viewpoints such as infrared spectrum, zeta potential, phase analysis, rheological properties and sedimentation behavior. The results showed that, compared with zeta potentials of SiC powders without TMAH addition, the zeta potential absolute values with TMAH addition were considerably increased with a pH ranged from 3 to 11. Moreover, with an amount of 0.3wt% TMAH addition, the solid loading of fine SiC suspensions increased from 33vol% to 60vol%.The results in the present study also indicated that, the optimum particle size gradation of SiC was 7:3 in the weight ratio for coarse powders and fine powders with a median particle size of 100μm and 2.0μm, respectively. With a pH of 9.63 and a TMAH concentration of 0.1wt%, the SiC suspensions mixed with coarse and fine powders used for recrystallized ceramics could be prepared with the highest solid loading of 70.25vol%.The influence of TMAH used as the dispersant on the rheological properties of SiC suspensions used for recrystallized ceramics was also investigated. The results showed that the Newtonian fluid behavior appeared in high shear rate range in the flow curve of SiC suspensions, while in low and middle shear rate range, shear thinning behavior presented and the variation of viscosity with the increasing shear rate could be fitted by power law, which was an innovative idea in this study. As power law, the fitting equations wereη=0.354γ-0.3743,η=1.232γ-0.4495,η=1.188γ-0.2867 andη=1.513γ-0.2752 for SiC suspensions with a solid loading of 62.5vol% 65.0vol%, 67.5vol% and 69.0vol%, respectively.Additionally, the recrystallized SiC ceramic bodies with a bulk density of 2.37g/cm3 had been successfully obtained by slip casting using SiC suspensions with a solid loading of 70.25vol%.更多还原