微沸法合成纳米莫来石及活化能的研究

Activation Energy and Synthesis of Nano-mullite by Micro-boiling Method

以硝酸铝和硅溶胶为原料,采用微沸法对合成纳米莫来石及其活化能进行研究,并用热重-差示扫描热量计(TGDSC)、X射线衍射仪(XRD)和扫描电子显微镜(SEM)对合成莫来石的粒度、相组成和形貌进行分析。结果表明:在原料中的铝硅摩尔比为3∶1的条件下,温度为854℃时莫来石开始形成,温度为920℃时Al-Si尖晶石开始转变为莫来石,温度为1200℃时莫来石化完成,合成莫来石的活化能为(634.52±28.90)kJ·mol-1。经过1200℃煅烧后,莫来石含Al2O3的摩尔分数为59.8%,平均粒度约为31.7nm,形状为针状,并由这些针状莫来石构成连续的网络结构。随着铝硅摩尔比的增加,合成莫来石的温度降低,活化能降低。当铝硅摩尔比增加至6∶1,合成莫来石的活化能降至(514.73±14.40)kJ·mol-1。

Nano-mullite was synthesized by micro-boiling method using aluminium nitrate and silica sol as raw materials,and the activation energy was studied.Grain size,phase composition and morphology of the mullite were analyzed by means of thermogravimetry-differential scanning calorimeter（TGDSC）,X-ray diffraction （XRD） and scanning electron microscope （SEM）,respectively.The results show that when Al/Si mole ratio is 3 ∶ 1 in the raw materials,mullite starts forming at 854℃,Al-Si spinel starts transforming into mullite at 920℃,mullitization is completed at 1200℃,and activation energy of mullite synthesis is （634.52±28.90） kJ · mol-1.After mullite is calcined at 1200℃,and the mole fraction of mullite containing Al2O3 is 59.8％,the average particle size is 31.7nm,with needle shape,and with these needle shape mullite forming a continuous network structure.The synthesizing temperature of mullite and activation energy decrease as mole ratio of Al/Si increases.Activation energy of synthesizing mullite decreases to （514.73 ± 14.40） kJ · mol-1 when mole ratio of Al/Si increases to 6 ∶ 1.