碳化硅空心微球的低温合成、显微结构设计和微波介电性能调控

Silicon carbide hollow microspheres (SCHMs) are synthesized by solvothermal process at about two hundred degrees with an amount of production, high yield, perfect morphology and good crystalline. The reaction mechanism of synthesis of silicon carbide with strong covalent bond and high melting-point compound in a low-temperature via a solvothermal process and the formation mechanism are proposed. The improvements of the dielectric properties of SCHMs and the matching with the wave impedance can be achieved through some approaches, such as, the microstructure control on the size, the thickness of wall and the surface morphorgy of hollow microspheres and the materials design by introducing functional spieces through solid solution modification, load in cavity and assembling and coating on the surface, combined with the unique tailorable property on the structure of hollow microspheres and the wide direct band-gap semiconductor properties of silicon carbide. The room dielectric properties under GHz of SCHMs are measured, and the change trendency and law of the dielectric properties of SCHMs from room temperature to one thousand two hundred degrees are also measured and studied. The novel lightweight materials with High temperature resistant, strong absorption, wideband absorption and more compatible under GHz microwave are expected. The outcome of the project will enrich the materials database of the high-temperature dielectric properties, which is great insufficient at present, and provide the experimental fundamentals and the theoretical ground of the new microstructure, new design and new properties of micro- & nano-materials when they are applied in the field of high technology and vital national security.

利用溶剂热法在大约两百摄氏度的较低温度下制备一定产量、较高产率、形态完整、晶形良好的碳化硅空心微球，揭示溶剂热法低温合成高熔点强共价键性的碳化硅的反应机理和空心微球形成的机理。结合空心球结构上可调的独特性和碳化硅的宽禁带半导体性质，通过对空心球的尺寸、球壁厚度、球体表面等显微结构上的调节，以及内部装载、固溶改性、表面修饰和组装等方法引入有序功能性组分进行材料设计，实现对碳化硅空心微球的微波介电性能的改善，并使其与波阻抗相匹配。测量研究碳化硅空心微球在GHz频段下的室温的介电性能，以及从室温到一千二百度高温的介电性能随温升的变化规律，以期获得对微波频段电磁波具有耐高温、强吸收、宽频带、多兼容的新型轻质材料。本项目研究将充实材料的高温介电性能数据库，为微纳米材料的新结构、新设计、新性能在高技术领域和国家重大安全领域的潜在应用提供实验基础和理论依据。

采用溶剂热法和改性的stober法两种方法制备了碳化硅空心微球。溶剂热法在反应釜中，温度为大约两百摄氏度的较低温度下和2-3MPa的压力下合成出制备较高产率、形态完整、晶形良好的碳化硅空心微球，缺点是球体尺寸不容易控制，产量不高。理论揭示溶剂热法低温合成高熔点强共价键性的碳化硅的反应机理和空心微球形成的机理。改性的stober法可以大量合成另一种结构的碳化硅空心微球，球体尺寸可控，球体内部是疏松结构，有利于掺杂和渗透，但是步骤较为复杂，碳化硅晶型控制上需要高温条件。结合空心球结构上可调的独特性和碳化硅的宽禁带半导体性质，通过对空心球的尺寸、球壁厚度、球体表面等显微结构上的调节，以及内部装载、固溶改性、表面修饰和组装等方法引入有序功能性组分进行材料设计，实现对碳化硅空心微球的微波介电性能的改善，并使其与波阻抗相匹配。测量研究碳化硅空心微球在GHz频段下的室温的介电性能，以及从室温到高温环境中的介电性能随温升的变化规律，以期获得对微波频段电磁波具有耐高温、强吸收、宽频带、多兼容的新型轻质材料。本项目研究将充实材料的高温介电性能数据库，为微纳米材料的新结构、新设计、新性能在高技术领域和国家重大安全领域的潜在应用提供实验基础和理论依据。