【作者】 赵强；

【导师】 李晓雷；

【作者基本信息】 天津大学 ， 材料学， 2009， 硕士

【摘要】 本文以磷酸盐粘结剂和硅溶胶为复合成膜物制备改性无机涂层,研究了硅溶胶对涂层的改性机理,磷酸盐涂层的热稳定性及涂层对多孔氮化硅基体封孔作用;以提高高温稳定性为目的,合成了改性无定形磷酸铝材料,探讨了这种改性磷酸铝的形成过程,分析了其在高温下的结构变化特点及基本的成膜特性。硅溶胶改性的磷酸盐涂层,充分利用了硅溶胶低温的结合强度和磷酸盐中、高温时的结合性能,弥补了单一粘结剂在使用性能上的不足,固化过程有利于网络大分子的形成,提高了涂层的附着能力;通过硅溶胶改性的磷酸盐涂层具有韧性好、附着力大、光泽度高等特点,并且可以在1000℃保持连续、致密,表现出较好的热稳定性。借助微观形貌分析和能谱分析,研究了涂层与多孔氮化硅基体的结合特点和封孔效果。结果表明,磷酸盐涂层经干燥、固化后可以紧密结合于氮化硅基体上,表面致密,降低了多孔基体的吸水率,提高了材料的防潮能力。涂层对多孔氮化硅的介电常数和介电损耗影响不大,保持了氮化硅本身良好的介电性能。在水溶性磷酸盐材料的基础上研究了乙醇溶剂下无定形磷酸铝材料的制备,探讨了体系的反应过程和材料的结构特点。过量铝的前体溶液设计是制备无定形磷酸铝的一个重要因素,五氧化二磷与乙醇的多酯化和水解控制着液体中的簇团的化学反应,在此过程中发生了一系列的分子过程,在P、Al、O和-OH之间产生了独特的空间配位,并通过胶凝和焙烧保留下来,增强了材料的热稳定性。氧化铝及超细二氧化硅的加入起到了抑制磷酸铝结晶的作用,进一步促进了无定形状态的生成,使得材料在高温下稳定存在,克服了传统磷酸盐材料高温下发生晶型转变带来体积效应的缺陷。同时,磷酸铝前体溶液具有良好的成膜性能,控制Al3+离子的浓度,可以在基体上沉积出平滑、完整、致密的涂层,以多次成膜的方式沉积的涂层仍保持着良好的附着性能。Al3+离子浓度为0.2mol/L时,五次成膜后可得到厚度约0.5μm的完整涂层。更多还原

【Abstract】 With mixed phosphate binder and silica sol as composite filmogen, the modified phosphate coatings were prepared. The effect of silica sol on the modified coatings and heat-durability of them were discussed. And the application of them as sealing coatings on porous silicon nitride ceramics was investigated. The modified amorphous aluminum phosphate was fabricated from the point of view of stability at high temperature. The characteristics of aluminum phosphate precursor solution and composition were studied in this paper.The modified coatings with silica sol made full use of the combination intensity of silica sol at low temperature and phosphate binder at higher temperature, which made up the deficiencies of single binder. The adhesion of the coatings was improved for the formation of macromolecules in curing process. The modified coatings with silica sol showed higher toughness, adhesion, glossiness, and performed excellent heat-durability without craze at 1000℃by studying the effect of temperature.The combination between coatings and porous Si3N4 substrate was researched by scanning electron microscope (SEM) and energy disperse spectroscopy (EDS). The results show that the coatings are compactly combined with Si3N4 substrate after solidifying. The water absorption of the porous Si3N4 substrate is decreased and the damp-proof capability of the substrate is increased after sealing by phosphate coatings. The dielectric constant and dielectric loss of the porous Si3 N4 are influenced little by sealing process, which is conducive to maintaining the dielectric properties of Si 3 N4 .The preparation of amorphous aluminum phosphate using ethanol as solvent was studied in the basis of water-solubility phosphate materials. The reaction process and structure characteristics of aluminum phosphate were discussed. The precursor solution design along with excess aluminum is believed a factor in the preparation of amorphous aluminum phosphate. The poly-esterification of P2 O5 by ethanol and hydrolysis controls the chemistry of clusters in liquid during which time a sequence of molecular event occur yielding unique spatial coordinations between P, Al, O and–OH which is preserved through gelation and calcination, which significantly enhances the thermal stability of the resulting material. It was found that the transformation of aluminum phosphate was retarded significantly in the presence of Al 2 O3 and ultrafine silica, which further promoted the formation of amorphous structure, making the material existed at high temperature to overcome the defects of polymorphic transformations with corresponding large volume changes in the traditional aluminum phosphate. At the same time, the aluminum phosphate precursor solution has good film forming properties. Diluted with ethanol to a appropriate concentration of Al3+, the precursor is well-adhered to the substrate and the micrograph demonstrates the continuous, dense and hermetic nature of the coating. The capabilities are also maintaining in repetitious filming. The thickness of the coating is about 5μm with five times filming when the concentration of Al3+ is 0.2 mol/L.更多还原