氧化铝粉对微孔方镁石—镁铝尖晶石耐火骨料显微结构和性能的影响

Effect of Al2O3 Powder on Microstructure and Properties of Microporous Magnesia Spinel Refractory Aggregates

中文关键词:  微孔方镁石－镁铝尖晶石耐火骨料  盐湖镁资源  显微结构  导热系数  热震稳定性

英文关键词:Microporous magnesia spinel refractory aggregates  Salt lake MgO resources  Microstructure  Thermal conductivity  Thermal shock resistance

中文摘要:

      以盐湖轻烧MgO粉和煅烧Al2O3粉为原料制备了4组微孔方镁石－镁铝尖晶石耐火骨料(镁铝尖晶石5 wt.%~20 wt.%)，并采用XRD、SEM和压汞仪等研究了煅烧Al2O3粉添加量(3.7 wt.%，7.7 wt.%，12.1 wt.%和16.8 wt%)对其显微结构和性能的影响。煅烧Al2O3粉在骨料内部形成多孔状镁铝尖晶石颗粒，增加其添加量，可增大微孔骨料的显气孔率，降低体积密度。尽管多孔状镁铝尖晶石微颗粒与MgO微颗粒间存在微裂纹，降低了耐火骨料的抗折强度，但该多孔镁铝尖晶石微颗粒能够诱导微孔骨料中微裂纹产生偏转和裂纹分支，在经受热震冲击时，能改善微孔骨料的热震稳定性。当煅烧Al2O3粉的添加量为7.7wt.%时，微孔方镁石－镁铝尖晶石耐火骨料拥有最佳的综合性能，其体积密度为3.23 g/cm3，中位孔径为386.1 nm，抗折强度为45.2 MPa，800 °C导热系数为10.5 W/(m·K)，热震后抗折强度保持率最高(97.0%)。

英文摘要:

      The present work prepared four microporous magnesia spinel refractory aggregates (spinel content 5 wt.%-20wt.%) with the light-burned MgO powder from the salt lake as the main raw material. The effects of the calcined Al2O3 powder addition (3.7 wt.%， 7.7 wt.%， 12.1 wt.% and 16.8 wt.%) on the microstructure and properties of microporous magnesia spinel aggregates were investigated by XRD， SEM and thermal shock test. Calcined Al2O3 powder formed porous spinel particles in microporous magnesia spinel aggregates. Increasing its addition can increase the apparent porosity of microporous aggregate and reduce the bulk density. Although there were microcracks between porous spinel particles and MgO micro-particles， which reduced the flexural strength of the microporous refractory aggregates， porous spinel particles induced the micro-cracks to deflect and branch in microporous magnesia spinel aggregates during the thermal shock test， which enhanced the thermal shock resistance of microporous magnesia spinel aggregates. At the addition of the calcined Al2O3 powder by 7.7 wt.%， microporous magnesia spinel aggregates had the best comprehensive performance， the bulk density of 3.23 g/cm3， the median pore size of 386.1 nm， the flexural strength of 45.2 MPa， the thermal conductivity of 10.5 W/(m·K) at 800 °C and the highest retention rate (97.0%) of the flexural strength after the thermal shock test.