Investigation On The Preparation And Performance Of The Lightweight Zirconia-based Fiber Insulation Material

With the rapid development of aerospace technology,for hypersonic vehicle subjected to aerodynamic heating for a long time,in order to ensure the safety of the main structure of the aircraft and internal instruments,it is necessary to use efficient thermal insulation materials to prevent external heat flow to the interior.Furthermore,the lightweight and efficient thermal protection materials are also of great significance to improve the payload and flight distance of missiles and spacecraft.In addition,in recent years,the worldwide energy crisis has become increasingly serious,reducing the loss of energy in the process of generation,transmission and utilization,and improving the efficiency of energy utilization has become the focus of widespread attention.Thermal insulation materials can effectively block heat transfer between different environments,which is of great significance for improving energy efficiency.In addition,However,the existing thermal insulation materials have problems such as high density,low space utilization efficiency and poor heat insulation ability,which are difficult to meet the higher requirements of civil high efficiency,energy saving and aerospace equipment.Therefore,the development of lightweight,high efficiency,high temperature resistant thermal insulation materials has become a hot topic in current research.In this thesis,taking zirconia fiber as the research subject,focusing on the macroscopic and microscopic structure of the material,the three-dimensional fiber sponge and Janus structural fiber membrane with lightweight characteristics were designed.In addition,starting from the microscopic mechanism of heat transfer,this thesis focuses on solving the problem of thermal radiation of zirconia fiber under high temperature,and improves the thermal radiation resistance of zirconia fiber by compounding with titanium oxide material with high nearinfrared reflection ability.Zirconia fiber sponge(ZF sponge),zirconia-titanium oxide Janus structural fiber membrane(ZTF membrane)and zirconia-titanium oxide composite fiber sponge(ZTF sponge)based on the first two studies were prepared.The mechanical properties and thermal insulation properties of the ZF sponge were investigated.The thermal insulation performance and near-infrared reflection performance of the ZTF membrane were studied.The fluffy mechanism,mechanical properties,near-infrared reflection performance,hightemperature thermal insulation and thermal insulation mechanism of three-dimensional ZTF sponge were investigated.The main research results of this thesis are as follows:The corresponding typical densities of three-dimensional ZF sponge after heat treatment at 1000℃,1100℃ and 1200℃ was 8.58 mg/cm3,9.34 mg/cm3 and 10.56 mg/cm3,respectively.ZF sponge possessed excellent compression resilience at room temperature,high temperature and low temperature,which can be attributed to the three-dimensional flufy structure.In addition,the thermal conductivity of ZF sponge at room temperature after heat treatment at 1000℃,1100℃ or 1200℃ was 26.8-27.4 mW/(m·K),exhibiting excellent thermal insulation performance.When the test-temperature was 1200℃,1.7 cm thick fiber sponge could block the temperature higher than 800℃,which showed good high-temperature insulation performance compared with other ordinary thermal insulation materials.The Janus structural fibers in the ZTF membrane combine the characteristics of zirconia and titanium oxide respectively.The room temperature thermal conductivity of ZTF membranes with different feed rates of zirconia and titania electrospinning solutions after heat treatment at 1000℃ and 1100℃ were 27.7-28.5 mW/(m·K)and 28.0-28.5 mW/(m-K),respectively.In addition,the average reflectance of the four fiber membranes with different feed rates was above 83%in the near infrared band,which was higher than that of pure zirconia fiber membranes.The ZTF sponge exhibited the characteristics of regular shape,low density,good compressibility,high near-infrared reflectance,good thermal insulation and so on.The typical density of ZTF sponge was 9.5 mg/cm3,and the thermal conductivity at room temperature was 27 mW/(m·K).At the same time,the sponge had good compressibility at-196℃ to 1200℃,and with an average near-infrared reflectivity greater than 92%in the range of 700-2500 nm.When the temperature of the hot side was 1200℃,the maximum temperature of the cold side of the 2.27 cm thick ZTF sponge was only 190℃,exhibiting good thermal insulation performance.The results showed that ZTF sponge was a kind of high-quality lightweight composite insulation material.