Full
JIANG Zhendong (2002-), male, Master candidate. E-mail: jzd0880@163.com
Outline
Driven by the rapid development of hypersonic vehicles and long-duration spacecraft, increasingly severe aerothermal environments have imposed unprecedented demands on thermal protection systems, requiring novel thermal insulation materials that combine low density, ultralow thermal conductivity, and excellent high-temperature durability. Aerogels, with their three-dimensional nanoporous networks, ultrahigh porosity, and suppressed solid- and gas-phase heat transport, are promising candidates for thermal protection applications. Among them, conventional silica aerogels, despite their excellent insulating properties, are typically limited to service temperatures below 800 ℃ due to structural densification and performance degradation at elevated temperatures. In contrast, alumina aerogels can operate above 1000 ℃ while maintaining low thermal conductivity and demonstrating superior high-temperature stability, making them a focal point in the field of high-temperature thermal insulation.
However, alumina aerogels still face serious challenges under high-temperature conditions. During heating, alumina undergoes successive phase transitions; in particular, above approximately 1000 ℃, the transformation to thermodynamically stable α-Al2O3 involves reconstruction from a cation-vacancy-rich spinel-like structure to a close-packed corundum structure. This transition causes rapid densification, substantial volumetric shrinkage, and particle sintering. As a result, the specific surface area and porosity collapse rapidly, causing the thermal insulation performance to deteriorate sharply at high temperatures, which severely restricts practical application.
To address these issues, recent efforts to improve the high-temperature performance of alumina aerogels can be grouped into three main strategies: 1) structural-unit engineering, in which highly crystalline or anisotropic building blocks are designed to enhance the thermal stability of the aerogel skeleton; 2) extrinsic doping, in which elements such as Si, Ti, Zr, and La are introduced to suppress the nucleation and grain growth of α-Al2O3; and 3) isolation phase construction, in which thermally stable secondary phases are formed between alumina particles to retard sintering after phase transformation. This review summarizes recent progress in these three strategies, analyzes of their underlying mechanisms, and discusses future directions for developing alumina aerogels with higher temperature resistance.
This review systematically summarizes recent advances in enhancing the temperature resistance of alumina aerogels through three key strategies: structural-unit engineering, extrinsic doping, and isolation phase construction. These approaches have effectively delayed alumina phase transformation and suppressed high-temperature sintering, increasing the short-term service temperature from approximately 1000 ℃ to as high as 1600 ℃ while maintaining low thermal conductivity and structural integrity at elevated temperatures. However, for applications requiring higher temperatures and longer exposure times, future research should prioritize multiscale synergistic design, infrared opacification, mechanical reinforcement, and deeper investigation of the microscopic mechanisms of high-temperature phase transformation and sintering. Integrating the integration of emerging technologies such as multiscale simulation and artificial intelligence is expected to accelerate the development of alumina aerogels that simultaneously achieve ultrahigh-temperature structural stability and durable thermal insulation functionality.
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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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