摘要
用水热晶化法一步制得D101晶面尺寸为10～16nm的具有较好结晶度的锐钛矿型的纳米TiO2。XRD结果和热力学分析表明,当水热晶化温度控制在体系的沸点时,所得到的锐钛矿型纳米TiO2的粒度最小。用水热晶化法制得的具有锐钛矿型纳米TiO2在100℃焙烧后就开始向金红石型转变。起始相变温度大大地低于文献报道的250℃。从而有效地避免了高温焙烧制备金红石型TiO2过程中的粒子团聚现象。动力学分析表明,在实验温度范围内(100～800℃)焙烧,低温段(t<500℃)的晶粒生长速率大于高温段(t>500℃)的晶粒生长速率。其晶粒生长表观活化能分别为:当t<500℃时,EA(锐钛矿)=18.76KJ/mol,ER(金红石)=38.49KJ/mol;当t>500℃时,EA(锐钛矿)=70.76KJ/mol,ER(金红石)=75.66KJ/mol。低温段(t<500℃)有利于锐钛矿型晶粒的生长,相比较而言,高温比低温更有利于金红石型晶粒的生长。
X-ray diffractometry was used to characterize the nano-titania prepared by the hydrothermal method. Under certain hydrothermal conditions (150~310 ℃, 1.0 MPa), anatase nano-titania, with the \ plane nanocrystalline lengths from 10 to 16 nm, was obtained. Experiment results and thermodynamics analysis showed that the smallest anatase nanocrystalline particles were obtained at a boiling point (ca.190 ℃). And in the nano-titania prepared by the hydrothermal method, the initial phase transformation from anatase to rutile took place at 100 ℃. It is lower than the reported temperature (250 ℃) and has effectively reduced nano-titania agglomeration during high temperature calcination for phase transformation from anatase to rutile. Kinetics analysis indicated that there were two growth rates of titania nanocrystal within the temperature range of 100~800 ℃. The apparent activation energy of titania nanocrystal growth \%E_A\%(Anatase)=18.76 KJ/mol and \%E_R\%(Rutile)=38.49 KJ/mol, respectively, when the temperature was below 500 ℃; and \%E_A\%(Anatase)=70.76 kJ/mol and \%E_R\%(Rutile)= 75.66 kJ/mol, respectively, when the temperature was above 500 ℃. The higher temperature (\%t\%>500 ℃) was favorable for the growth of rutile nanocrystal compared with the higher temperature (\%t\%<500 ℃).
出处
《浙江工业大学学报》
CAS
2004年第1期41-46,共6页
Journal of Zhejiang University of Technology
