Modification of Ceramic Powders by Utilizing Organic-Inorganic Hybrid Interface

本论文尝试了以下几种新型功能材料的制备及其性能的改善：1.通过癸二酸对金属氮化物粉体进行表面化学改性，在保持其亲水性的同时，提高其对水的化学稳定性。用乙酸钇处理癸二酸改性的粉末导致Y^<3+>离子作为烧结助剂通过离子交换以高度分散的水平在金属氮化物粉末表面上的强固定化。通过选择合适的浆料组成和烧成条件，在1900℃下无压烧结5 h，AlN的热导率达到约250 W·m·<-1>K·2<-1>。2.采用1，12-十二烷二羧酸的LB膜在硅或玻璃基底上制备了亚微米尺寸的球形氧化物过氧化物的紧密堆积单层膜，然后脱水二羧酸的羧基与基体和陶瓷表面的羟基发生缩合反应3.<-1>以锡酸钠为原料，采用氯化十六烷基吡啶自组装，磷酸处理，600℃煅烧5 h，制备了具有高热稳定性和高比表面积的有序介孔SnO_2粉体。4.采用二甲基二乙氧基硅烷对SnO_2粉体进行表面化学修饰，并对其气敏性能进行了评价。TEM观察表明，表面改性引入的SiO_2以晶界相形式存在。SiO_2薄膜对SnO_2颗粒间颈部生长的限制，是提高势垒高度和改善对H_2、CH_4和C_3H_8等可燃气体敏感性能的主要原因。

Preparation of various new functional meterials and improvement of its properties were attempted as below.1.Chemical stability of metal nitride powders against water was improved by surface chemical modification with sebacic acid, while maintaining a hydrophilic surface. Treatment of the sebacic acid-modified powder with yttrium acetate resulted in strong immobilization of Y^<3+> ions, as a sintering aid, at a highly dispersive level on the metal nitride powder surface through ion exchange. By selecting slip compositions for better deflocculation and firing conditions, a thermal conductivity of ca.250 W m^<-1>K^<-1> was attained by the pressureless sintering of AIN at 1900℃ for 5h.2.Closely packed monolayer of spherical oxide perticles of sub-micron size was fabricated on a silicon or glass substrate by employing a Langmuir-Blodgett film of 1, 12-dodecanedicaboxylic acid, followed by dehydration-condensation reatcion between carboxyl groups of the dicarboxylic acid and the surface hydroxyl groups of both the substrate and the ceramic spheres.3.Ordered mesoporous SnO_2 powders with high thermal stability and a high surface area 305 m^2g^<-1> were prepared from sodium stannate by utilizing the self-assembly of n-cetylpyridinium chloride, followed by treatment with phosphoric acid and calcinations at 600℃ for 5h.4.SnO_2 powder was subjected to surface chemical modification with diethyoxydimethylsilane and the gas sensing properties were evaluated. The SiO_2 introduced by the surface modificaton was found to exist as a grain-boundary phase from TEM observation. The limitation of neck growth between SnO_2 particles by the SiO_2 thin film coating is anticipated to be responsible for increasing the potential barrier height and improving the sensing properties to inflammable gases such as H_2, CH_4 and C_3H_8.