用于导热填料的片状氧化铝的制备

Preparation of Flaky Alumina for Heat Conducting Filler

在Na2SO4和K2SO4复合熔盐体系中,以Al2(SO4)3为铝源,饱和Na2CO3溶液为沉淀剂,用溶胶-凝胶法制得氢氧化铝凝胶,然后用去离子水将凝胶稀释成不同比例,将稀释后的凝胶采用不同的干燥方式干燥得到前驱体氢氧化铝,再经煅烧、洗涤和干燥后得到片状氧化铝粉体。将片状氧化铝粉体与丁腈橡胶(NBR)混炼,在模具中硫化压片。通过电子显微镜和粒度分析仪观察和分析氧化铝的形貌和粒度,用化学分析法检测片状氧化铝的纯度,用导热仪测试橡胶片的导热率。研究熔盐比例、凝胶干燥方式和晶体生长空间对氧化铝粉体粒度分布及形貌的影响,考察不同粒度分布的片状氧化铝对丁腈橡胶导热率的影响。结果表明,当熔盐比Al2(SO4)3∶Na2SO4∶K2SO4为1∶1∶1,稀释比为3∶1时,干燥箱干燥后于1 200℃煅烧5 h,可获得形貌完整、表面光滑、分散性好、粒度分布窄的六方片状氧化铝粉体,Al2O3含量为99.49%。片状氧化铝的填充可以提高丁腈橡胶的导热率,粒度分布越窄越有利于丁腈橡胶导热率的提高。

Using Al2(SO4)3 as aluminum source and saturated Na2CO3 solution as precipitant,aluminum hydroxide gel was prepared by sol-gel method in Na 2SO4 and K2SO4 composite molten salt system,and then the gel was diluted to different proportions with deionized water.Precursor aluminum hydroxide was derived from the diluted gel by different drying methods,then flaky alumina powder was obtained through calcined,washed and dried.The flaky alumina powder was mixed with NBR and vulcanized and pressed in the mould.The morphology and particle size of alumina were observed and analyzed by electron microscope and particle size analyzer,the purity of flaky alumina was determined by chemical analysis and the thermal conductivity of rubber sheet was measured by thermal conductivity meter.The effects of the proportion of molten salt,the drying method of gel and the space of crystal growth on the particle size distribution and morphology of alumina powder were studied.The effect of flaky alumina with different particle size distribution on the thermal conductivity of NBR was investigated.The results show that hexagonal flaky alumina powder with complete morphology,smooth surface,good dispersion and narrow particle size distribution is obtained under the conditions of 1∶1∶1 ratio of Al 2(SO 4)3∶Na2SO4∶K2SO4,3∶1 ratio of dilution,drying in oven and calcining at 1200℃for 5 h,the content of Al2O3 is 99.49%.The thermal conductivity of NBR is improved by filling flaky alumina,and the narrower the particle size distribution,the higher the thermal conductivity of NBR.