氧化铝基蜂窝陶瓷蓄热体的制备及其性能研究/

2018-12-10 20:34:57

thermal heat 材料 10 Al



以α-Al_2O_3微粉料为主原料,采用粘土、羧甲基纤维素(CMC)等有机-无机复合增塑剂,加入桐油等作为润滑剂,采用挤出成型法制备刚玉质高温型蜂窝陶瓷蓄热体。用塑性测试仪测定了增塑剂等对泥料可塑性指标的影响;解决了瘠性料难以挤塑成型的技术难题。在制备过程中,引入MgO等矿化剂来降低氧化铝的烧结温度,促进氧化铝陶瓷的烧结,调整材料的矿物组成,控制材料的显微结构,优化材料的热学性能和力学性能等,使其能够应用于高温蓄热燃烧领域。实验发现,泥料的含水量应该保持在10%~20%的范围内,复合增塑剂含量保持在3~7%为宜。MgO等矿化剂的引入能够有效的促进Al_2O_3陶瓷的烧结,使其能够在1450℃保温1小时的条件下发生烧结。
通过XRD、SEM(带能谱分析)等测试手段测试样品的矿物组成和显微结构;结果表明,引入MgO等矿化剂后,材料在烧结过程中主要形成第二相和一定量的低共溶相填充在Al_2O_3晶粒之间,籍此可以有效控制材料的显微结构。用示差法、阿基米德法、三点弯曲法等方法测试出材料的热膨胀系数、密度、吸水率、气孔率、强度等。材料的热膨胀系数可降低到62.5×10-7℃-1以下,孔壁密度大于2.40 g/cm3,吸水率保持在9~16%,显气孔率小于38%,抗折强度则大于40MPa,用TC700OH激光热常数测试仪测定了材料的导热系数和比热,导热系数为1.015×101 W/(m·K)(18℃)和 5.802×100 W/(m·K)(1300℃),比热为8.836×10-1 J/(g·K)(18℃)和 1.960×100 J/(g·K)(1300℃),用三角耐火锥测温法测定了材料的耐火度,其值大于1790℃,采用模拟实际工况的方法对材料的抗热震性进行了测试,在1100℃~10℃的冷水交替循环下抗热冲击次数大于40次。
实验发现,当外加剂含量较少时,样品的烧结程度低,强度不理想,抗热震性能不好。外加剂含量过多则生成过多的液相,使样品的气孔率大大减小,减少了材料在热冲击过程中的结构调整空间,从而降低了材料的抗热震性能。SiC的引入,不但能够与Al_2O_3发生反应生成液相组分和第二相,并且能够诱导A_l2O_3晶粒长成片状,大大增强晶粒间的结合强度,剩余的SiC还可以起到颗粒弥散增强的作用,从而有效的提高了Al_2O_3陶瓷材料的强度。引入SiC的样品在烧结过程中,首先在样品的表面产生SiC与O_2及Al_2O_3的反应,形成一层致密的保护层,阻碍O_2进入材料内部,在材料的内部留下较大的气孔率,可以降低其热膨胀系数,并使材料在受热过程中有一定的空间进行结构调整,能够显著的提高Al_2O_3陶瓷材料的抗热冲击次数。
实验结果表明,本文开发的蜂窝陶瓷蓄热体具有良好的蓄热性、传热性、抗热震性和耐高温性,并具有较高的强度和密度,是一种非常理想的高温型蓄热体。



In the dissertation high-temperature corundum honeycombed ceramic regenerative body was prepared by an extrusion process, α-Al_2O_3 minute powder as main raw material, clay, CMC etc as plasticizers, tung oil etc as lubricator. The plastic performance was tested on a plastic measure apparatus. During preparation added MgO etc as mineralization were added to decreases sintering temperature of Al_2O_3, control the mineral composion and microstructure, optimize the performance of heat and mechanics, etc, resulting in its use in regenerative combustion field. The result of experiment show that the best content of water is in the range of 10%~20%, and the CMC is about 3~7%. Dropping of MgO etc can decrease sintering temperature of Al_2O_3 efficaciously, and make Al_2O_3 sintered at 1450℃ for 1 hour.
Mineral compositions and the microstructure were investigated by XRD and SEM; the result show that The second phase and liquid phase are produced during sintering, and the second phase and liquid phase were filled in space of the Al_2O_3 crystals, which can control the microstructure efficaciously. Density, porosity, thermal expansion coefficient and intensity were tested by Archimedes-method, show the distance and bend resist of three point etc. Heat-conducting coefficient and specific heat etc were tested on a TC700OH laser heat constant measure apparatus, The fire-resistant performances were tested by triangle thermoscope, Thermal shock property was tested by simulating the fact, the results show that the material’s thermal expansion coefficient can be decreased less than 62.5×10-7℃-1, the density of the wall of bore more than 2.40 g/cm3, the sop rate range in 9~16%, the pore rate less than 38%, the intensity were more than 40MPa, the heat-conducting coefficient were 1.015×101 W/(m·K)(18℃)and 5.802×100 W/(m·K)(1300℃),specific heat were 8.836×10-1 J/(g·K)(18℃)and 1.960×100 J/(g·K)(1300℃). the fire-resistant temperature were more than 1790℃.,and the samples’ thermal shock resistance times were over 40 times during tested by simulating the fact(1100℃~cold water which temperature is less than 10℃).
The experiment results show that the samples can not be sintered when the addition phases were in a very low level, and their strength and thermal shock resistance performance were neither, there were too much liquid phase created when the addition phases were in a high level, it can decrease the pore rate of the samples, and the space for structure adjusting during thermal shock, resulting in the decrease of their thermal shock resistance performance. Adding SiC can decreases sintering temperature of Al_2O_3 efficaciously, but also can make the Al2O3 crystal growth as flake, strengthen the coalescent of the Al_2O_3 crystals, and the residual SiC during sintering can strengthen the Al_2O_3 ceramics. Because the reaction between SiC and Al_2O_3 begins from the surface of samples, there is a compact protecting field on the surface of the samples to restrain O_2 enter into the samples, and leave more pore in them to decrease the thermal expansion coefficient and increase their the Al_2O_3 ceramics’ thermal shock resistance times.
The results of experiment show that the samples have good regenerative conduction of heat, good heat-conducting, good heat-shock resistant, refractoriness property, and have higher strength and density, and it can be used as a kind of ideal high-temperature regenerative body.