Effect Of Microstructure Control Of Plant Pore-forming Agent On Properties Of Alumina Insulation Material

Alumina thermal insulation material are typically fabricated by the addition of a pore-forming agent,and plant matter has a long history as the most widely used pore-former in the ceramic industry.However,there are many problems such as elastic aftereffect,imbibition and microporous when using plant pore-forming agent.In addition,the silicon element and multi-level and multi-dimensional special structure of plant pore-forming agent itself have not been effectively utilized in thermal insulation materials,resulting in poor thermal insulation performance and other physical properties of the prepared thermal insulation materials.However,there are few reports on the optimization of the pore structure of the material by the control of the morph-genetic porous structure of the plant pore-forming agent,thereby improving the thermal insulation properties and mechanical properties of the alumina insulation material.Focusing on the above problems,inorganic sols are used to impregnate the pore-forming agents to retain its morph-genetic structure at high temperature,and the effect of the morph-genetic structure of plant pore-forming agent on the structure and properties of alumina insulation material was explored.The main research work of this paper includes:(1)Plant pore-forming agents were vacuum-infiltrated with zirconium sol,aluminum sol and silica sol,respectively,and the effect of sol impregnation on elastic aftereffect,expansion condition and the structure retention and evolution of plant pore-forming agents were explored;(2)Alumina thermal insulation material was prepared by adding the pore-forming agent impregnated with the above-mentioned sol as the main raw material,and the effect of the morph-genetic structure of plant pore-forming agent on the structure and properties of alumina thermal insulation material was studied.(3)Walnut shell powder impregnated with silica sol-alumina sol,silica sol-zirconium sol and silica sol-alumina sol-zirconium sol was used as pore-forming agent to study the evolution of the morph-genetic structure of walnut shell powder and its effect on the structure and properties of alumina thermal insulation material.The detailed results were listed as follows:(1)The elastic aftereffect and expansion condition of rice husk,sawdust and walnut shell powder after impregnation with zirconium sol,aluminum sol and silica sol show differences due to their structure and types;After heat treatment at high temperature,the morph-genetic structure of pore former are preserved.(2)The difference in the structure of the pore former and the type of the sol result in different effects on the performance of specimens.The alumina thermal insulation material prepared by impregnating rice husk,sawdust and walnut shell powder with a solid content of 3wt% as pore formers exhibits the best physical properties when the firing temperature is 1550 ?.The thermal conductivity of most specimens decreases at different temperatures,when the morph-genetic structure of plant pore-forming agents are introduced into alumina insulation material.Moreover,the introduction of the morph-genetic structure of rice husk and walnut shell powder into the porosity of alumina thermal insulation material greatly reduces the pore size of specimens.However,the morph-genetic structure of sawdust leads to the opposite result.The porous morph-genetic structure of rice husk,sawdust and walnut shell powder are found in the pore of the specimens.In addition,mullite is formed in the pore of specimens using pore formers with 3wt% silica sol to form a cross-network structure.(3)Alumina thermal insulation material is prepared with walnut shell powder impregnated by multiple sol as pore-forming agent.The cold crushing strength and thermal insulation properties of the specimens were greatly improved without obvious changes in porosity,linear shrinkage and bulk density.Among them,the specimen with walnut shell powder impregnated with silica sol?aluminium sol?zirconium sol as pore-forming agent have better comprehensive performance.The impregnation of walnut shell powder with multiple sols resulted in a large number of small pores in the range of 0.3-5?m.In addition,the existence of morph-genetic structure of walnut shell powder was observed in the pore of all groups of samples,and these morph-genetic structures were porous structures.