氧化铝陶瓷低温特性研究

Research of Mechanical and Thermal Properties of Al_2O_3 at Cryogenic Temperatures

研究了α-Al2O3含量分别为99%和92%的氧化铝陶瓷(以下分别简称99和92氧化铝陶瓷)在室温和低温下(293,195和77K)的力学和热学性能。结果表明:两种氧化铝陶瓷的抗弯强度变化规律相同且变化幅度都较小,说明玻璃相的存在并没有对氧化铝的低温强度造成显著影响;99氧化铝的断裂韧性随温度降低线性升高,而由于晶界玻璃相的存在,92氧化铝的断裂韧性在77K时有所降低。热学性能测试表明,两种氧化铝的热导率随温度的变化规律一致。99和92氧化铝在20K时的热导率分别为4.1和1.7W/(m·K),远远小于不锈钢的热导率14.7W/(m·K)。因此,如果采用氧化铝陶瓷替代不锈钢作为超导绝缘支撑材料可以大大降低系统的漏热,提高超导磁体的稳定性。

The mechanical and thermal properties of two types of alumina ceramics containing 99% and 92% α-Al2O3 respectively at cryogenic and ambient temperatures (293, 195 and 77 K) were investigated. It is noted that the influence of temperature on flexural strength of both types proves to be the same, indicating that the strength at cryogenic temperatures can't be affected by the presence of glass phases. The fracture toughness of 99% Al2O3 is increased linearly with decreasing temperature while that of 92% Al2O3 is decreased at 77 K related to the presence of glass phases. It is also observed that the thermal conductivity of both types of ceramics with the decrease of temperature has the same trend. The thermal conductivity of 99% and 92% Al2O3 turn out to be 4.1 and 1.7 W/m·K respectively which are much less than that of stainless steel. The heat penetration to cryogenic area can be, consequently, reduced significantly and thus the stable operation of superconducting magnets can also be enhanced.