【摘要】 采用TG DTG DSC热分析、X射线衍射物相分析等方法研究了稀土元素对氢氧化铝凝胶加热转变过程的影响。实验结果表明 :稀土的添加加速了非晶Al2 O3的形成 ;提高了非晶态Al2 O3的晶化温度 ;对γ Al2 O3向α Al2 O3转变的影响随稀土添加种类及添加量不同而不同 ,添加的 4种稀土元素对该转变的抑制作用由强到弱为 :La >(Y ,Nd) >Ce。对稀土作用机制的初步分析结果表明 :稀土添加减少了Al2 O3中残余的羟基 ,因而降低了晶化过程中铝离子的扩散速率 ,从而减少了γ Al2 O3的晶化速率 ;稀土对γ Al2 O3向α Al2 O3转变的抑制作用主要是由于稀土铝酸盐的形成 ,LaAl1 1 O1 8(磁铅石结构 )的形成能更有效地抑制γ Al2 O3向α Al2 O3的转变 ,而YAlO3和NdAlO3的抑制作用则较小 ,以氧化物形式沉淀出来的CeO2 对γ Al2 O3向α Al2 O3转变没有明显影响更多还原

【Abstract】 The effects of rare earth elements on the transformation of Al(OH) 3 gel during heating process were analyzed by means of TG DTG DSC thermal analysis and XRD. Rare earths accelerate the formation of Al 2O 3; and rare earths defer the crystallization of amorphous Al 2O 3; the resistance of rare earths against the transformation from γ Al 2O 3 to α Al 2O 3 is weakened gradually with an order of La>(Y, Nd)>Ce. The action mechanisms of rare earths on the transformation of Al(OH) 3 gel during heating process were also discussed. The hydroxyl remnant in γ Al 2O 3 is reduced by rare earth addition, so the transporting velocity of Al 3+ is slowed down, as a result, the crystallization of amorphous Al 2O 3 is delayed. The resistance of rare earths against the transformation from γ Al 2O 3 to α Al 2O 3 is due to the formation of rare earth aluminate, and LaAl 11 O 18 (with a magnetoplumbite structure) is more effective to delay the transformation than YAlO 3 and NdAlO 3 (with a spinelle structure), and CeO 2 does not affect the transformation.更多还原