摘要
以AIP(Aluminum-isopropoxde)和 TEOS(Tetraethyl Orthosilicate)为主要原料,采用Sol-Gel-SCFD(超临界流体干燥)技术制备了n(Al_2O_3):n(SiO_2)=3:2的Al_2O_3-SiO_2二元纳米气凝胶,通过中温煅烧,获得了纳米级莫来石.用热重-差示扫描热量计(TG-DSC)、透射电子显微镜(TEM)、X射线衍射仪(XRD)和物理吸附分析仪(Autosorb)等手段对二元纳米气凝胶和纳米莫来石进行了分析和研究.TG-DSC研究表明,在煅烧过程中,气凝胶的大部分失重(15.98％)在700℃左右已完成,DSC曲线上在445和 1015℃存在的两个放热峰是由于二元凝胶中的Si-O-Al-O结构重整和莫来石化所致,而在805℃处小的吸热峰是由体系中结构水分解所致;借助于 TG-DSC、XRD和 TEM分析手段,可以确定在纳米Al_2O_3-SiO_2二元材料内,莫来石的开始形成温度为1015℃左右.XRD分析表明,完全转变成莫来石温度在1100～1200℃之间,1200℃可得晶粒发育良好的纳米级莫来石;TEM和物理吸附分析仪测试结果表明,1100和1200℃所得纳米莫来石的微粒大小分别为30和50nm左右,比表面积分别为138.91和95.81m^2/g.
Nanometer mullite was prepared through Sol-Gel-SCFD and middle temperature calcination by using aluminium-isopropoxde and tetraethyl orthosilicate as starting materials, the alumina-silica binary aerogel and calcined nanosized materials were investigated by using thermogravimetry-differential scanning calorimeter (TG-DSC), transmission electron microscope (TEM), X-Ray diffractometer (XRD) and specific surface area and porosimetry. TG-DSC indicated the removal of most of the volatiles, i.e. 15.98% up to about 700degreesC, and in the DSC curve, the existence of two exothermic peaks at about 445 and 1015degreesC may be due to the crystallization of Si-O-Al-O in diphasic gels and mullitization, and a small endothermic peak at about 805degreesC indicated the decomposition of structural water molecules. The beginning temperature of mullitization of the Al2O3-SiO2 at about 1015degreesC in gel was confirmed by TC-DSC, XRD and TEM, XRD results which also showed the formation of mullite at the range 1100similar to120degreesC. TEM and surface area and porosimetry results showed that the nanosized mullite calcinated at 1100 and 1200degreesC exhibited the sizes of 30nm and 50nm, specific surface area 138.91m(2)/g and 95.81m(2)/g respectively.
出处
《无机材料学报》
SCIE
EI
CAS
CSCD
北大核心
2004年第3期471-476,共6页
Journal of Inorganic Materials
基金
武汉市科技计划项目(20011007088)
湖北省科技攻关计划重点项目(2001AA101B07)
