Thermal treatment of titanate derivatives synthesized by host-guest reaction

摘要

In our previous work [1], two kinds of titanate derivatives, layered hydrous titanium dioxide and potassium octatitanate with a tunnel structure, were synthesized with the aid of the host—guest reaction method. To this end, the initial material, potassium tetratitanate (K^TLtCVnH^O), was prepared by cal-cination of a mixture of K2CO3 and TiO2 with a molar ratio of 2.8 at 1050 °C for 3 h, followed by boiling water treatment of the calcination products for 10 h. Fibrous potassium tetratitanate could be transformed into layered hydrous titanium dioxide Cy?H2O) through an exchange of K+ with using HC1, but it should be noted that to prepare layered hydrous titanium dioxide, all of the K+ ions must be substituted with H+ ions with the host framework [TuOg""],, kept in a sheet-like shape. Both the acid concentration and the treatment time were important controlling factors. It has been found that five 1 h treatments with 0.075 M HC1 solution effectively yielded layered H2Ti4Oc>-?H20. Potas-sium octatitanate (K^TisOn} could be formed by a thermal treatment of KHTi4O9-?H2O. A single KLHTi4Ot)'?H2O was effectively produced by treat-ment of K2Ti409 with a 0.005 M HC1 solution for 3O min. Thermal treatment at a temperature ranging from 250 to 500 °C for 3 h yielded K2Tis0i7 alone. The average length and diameter of the K2Ti8Oi7 whiskers were 125 and 1 /an, respectively.