【作者】 郭兵健；

【导师】 武七德； 吉晓莉；

【作者基本信息】 武汉理工大学 ， 材料学， 2004， 硕士

【摘要】 SiC陶瓷材料具有优良的热学、力学、化学或电学性能，是一种颇具应用前景的结构陶瓷材料。但由于陶瓷实现后期加工的困难性、低可靠性等因素限制了其广泛应用。湿法及胶态成型工艺是制备高可靠性、复杂形状陶瓷部件的有效方法，它具有容易控制坯体的团聚、杂质、减少坯体的缺陷、可制各出形状复杂的陶瓷部件等许多优点。此种成型工艺的关键是制备具有高固相含量(≥50％的体积分数)、低粘度(＜1Pa.S)特性的均匀稳定陶瓷料浆，这一目标可通过对粉体尤其是超细粉体的表面改性获得。 研究中采用对陶瓷粉体表面进行有机包覆改性的方法改变其表面特性。并通过对硅烷偶联剂官能团进行修饰的方法，制备出了满足SiC粉表面包覆改性所需的偶联剂，最终使之与SiC微粉表面通过化学键合的方式结合，改善了SiC微粉在水基料浆中的分散特性。利用FTIR、XPS、TEM、XRD、TG-DSC、电视显微电泳仪等测试方法对包覆改性前后SiC微粉的表面结构、胶态特性和分散稳定性能进行了详细分析，研究讨论了包覆层物质、改性工艺参数等因素对改性粉体分散稳定性的影响，并对改性SiC微粉的分散稳定机理作了探讨。 使用在单纯包覆改性SiC微粉料浆中加入分散剂的方法，成功制备了固相含量高达58％、表观粘度(855.6mPa.S)＜1Pa.S的水基料浆。注浆成型所需的高固相含量、低粘度SiC料浆可利用颗粒级配、料浆pH值调整和加入消泡剂的方法获得。并最终成型得到绝对密度高达2.58g/cm~3、相对密度为80.4％的均匀注浆SiC坯体。更多还原

【Abstract】 Covalent ceramic materials like silicon carbide (SiC) have been recognized as potential candidates for high temperature structural applications, because of their superior thermal, mechanical, chemical and electrical characteristics. Their widespread application is, however, limited by the critical and complicated manufacturing technologies of brittle ceramics and the low reliability to the material’s properties. With wet or colloidal processing method, which has the advantages of easy control of agglomeration, impurities, and the defects, ceramics can be produced with high reliability and complicated shapes. The problem, which must be solved firstly, is the preparation for the low viscosity, homogeneous concentrated ceramic suspension of which solid loading is higher than 50% solid volume fraction. The surface modification of fine ceramic powders is the optimal method to improve the dispersity of ceramic powders.The dissertation describes an organic-coating method for changing the surface properties of ceramics powder. The modified organosilane coupling agent can bond with Si-OH which is on the surface of SiC powder. This covering layer will change the chemical constitution and surface properties of the SiC powder, that will consequently improve the dispersity of the SiC fine powder in water. A various of analysis methods such as FTIR, XPS, TEM, XRD and TG-DSC are used to detect the substance and the structure of the covering on the SiC powder surface. In this paper, the size distribution, exterior configuration and colloidal properties of the powder are analyzed. The dispersion and stability mechanism of modified powder are also studied. The effects of technologic parameters and package substances on the dispersity of modified powders are carefully investigated.The low viscosity (855.6mPa.S) and homogeneous concentrated SiC suspension with 58vol% is prepared with the addition of dispersant by using the modified fine powders. The high solid loading and low viscosity suspension,which will be applied to slip casting to manufacture SiC, is prepared by using fine modified SiC powder mixed with coarse powder properly through the redressal of pH value and the addition of defoaming agent. The highest density of green body prepared by slip casting may reach 2.58g/cm3, which is about 80.4%of theoretical density of the SiC material.更多还原