Full
DING Donghai (1983-), Male, Ph.D., Associate Professor. E-mail: dingdongxauat@163.com
Outline
It is of great practical significance to develop thermal insulation materials with integrated load bearing and thermal insulation for energy saving and emission reduction in high-temperature engineering. In this work, SiO2f/SiO2 composites were prepared by a precursor impregnation heat-treatment method with quartz fiber needled felt as a reinforcement and silica sol as a precursor. The effect of heat-treatment temperature on the density, porosity, mechanical properties and thermal properties of SiO2f/SiO2 composites was investigated. The composition and microstructure of the composites were characterized by X-ray diffraction and scanning electron microscopy. The coefficient of thermal expansion and thermal conductivity of composites were measured by a push rod method and a transient hot-wire method. The results indicate that the apparent porosity and mechanical strength firstly increase and then decrease with the increase of heat-treatment temperature. The sample after heat-treatment at 450 ℃ has the optimum overall performance (i.e., the flexural strength of 23.5 MPa, and the compressive strength of 61.9 MPa). The fracture mechanism is a ductile fracture. At 300-700 ℃, the thermal expansion coefficient of the sample is 0.564×10-6/℃. The thermal conductivity of the samples decreases with the increase of temperature, and it is as low as 0.096 W/m·K at 700℃. The SiO2f/SiO2 composite prepared has some advantages in the integrated application of load bearing and thermal insulation, and meets the harsh requirements of hot pressing and sintering, non-ferrous metallurgy and other industries.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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