稻壳质二氧化硅轻质绝热材料内孔隙强化机理与孔隙结构优化方法研究

Rice husk, consisted of organicmaterials (e.g. cellulose, hemicellulose and lignin) (61-77 wt%), ash (mainly amorphous SiO2) (13-29 wt%) and water, is an abundant agriculture by-product available in rice-producing countries. Lots of rice husk is left, which is treated as waste and disposed at landfill site in some areas, leading to air and water pollution. Nowadays, how to use rice husk this economical and abundant industrial waste becomes a hot topic. . Due to its porous structure and high silica content, the fabrication of insulation or porous materials using rice husk as raw material is an alternative for environmental subjects, as well as adding value to the residue. Furthermore, the biological structure is hierarchical in nature, and rice husk is a typical example of which with large surface area and porosity. Such structural features of rice husk inspire us to replicate them on functional materials with special functional properties. Thus, we except to prepare porous silica light insulation utilizing rice husk effectively for inheriting its advantages of both chemical composition and microstructure.. Based on removing metal oxides impurity by acid leaching, sol doping method are used to in-situ impregnation of infrared opacifier on rice husk silica, which not only dispersing infrared opacifier in rice husk well, but also strengthening rice husk intrinsic pore structure and enhancing rice husk silica sintered temperature(>1000 ºC) without gathering. The porous structure, mechanical strength, thermal insulation and some other properties are analyzed by means of XRD, BET, SEM, TEM and some other experimental techniques. An analytical model based on the fractal theory is used to describe the porous morphology of rice husk silica. Finite element analysis software is used to analyze the kinetics of pore structure evolution and the temperature field and stress field of porous silica insulation. Software FACTSAGE is used to calculate forming conditions of new phases in porous silica insulation. Mathematical analysis and simulations are carried out to quantify the influence of the pore size distribution on the thermal conductivity, which is the main physical property associated to the microstructure’s insulating capacity. A new approach is used to extract the pore parameters controlling physicochemical properties through optimizing the model to experimental data. . The optimization parameters and strengthening mechanism of rice husk silica porous structure are analyzed. Regulate the microstructure of porous light insulation in coordination with physical and chemical conditions, optimize preparation, and provide theoretical guidance of rice husk intrinsic porous structure. Lay a theoretical foundation of preparing porous rice husk silica light insulation with stable porous structure, heat insulation and excellent mechanical strength.

本项目以新型二氧化硅（SiO2）轻质绝热材料作为研究对象，利用农业废料稻壳的特有织构原位构筑微纳米级气孔。针对气凝胶类材料热导率随温度升高而升高，在1000 ºC以上高温下不能使用等缺陷，采用第二相浸渍、包覆稻壳SiO2孔筋技术，不仅有效提高稻壳SiO2高温下孔隙强度，而且均匀富载热辐射遮蔽剂，优化孔隙微结构，大幅降低材料热传导。将处理后的稻壳粉成型，控制烧结条件，得到结构稳定、物理性能优异的SiO2轻质绝热材料。本项目拟采用分形学和有限元理论模拟不同条件下稻壳本征结构特征及其相应轻质绝热材料内孔隙结构，研究孔隙微结构与材料物理性能间关系，揭示稻壳SiO2轻质绝热材料的孔筋强化机理。通过分析孔隙内新相晶型与生长发育条件，研究孔隙结构的控制参数与材料传热过程及力学性能的内在关联，建立相关模型，总结高效保温材料内孔隙微结构优化方法，为利用稻壳制备微纳米孔SiO2轻质绝热材料打下理论基础。

本项目研究了稻壳本征织构的变化；研究了复合条件对稻壳孔隙结构、孔隙强度及屏蔽红外热辐射效果的影响，总结出稻壳SiO2的孔隙强化条件与结构优化方法。利用复合红外遮蔽剂的稻壳制备了轻质氧化铝绝热材料，分析了材料的微结构和力学性能及传热特性之间的关系。采用溶胶真空浸渍修饰孔形，发现试样的狭缝形气孔向类球形过渡的同时平均孔径显著降低，其力学性能也相应得到提高。确定了3种高性能轻质绝热材料的制备工艺参数和强化机理及传热机理。共计发表论文15篇，共计申报专利2项，其中1项授权。