PbO和TiO_2混合粉磨的机械力化学反应和化学变化

MECHANO-CHEMICAL REACTION AND CHEMICAL CHANGE IN THE GRINDING OF MIXED PbO AND TiO_2 POWDER

本实验首次发现,在振动磨中混合粉磨PbO和TiO_2化学配比的粉体,能合成PbTiO_2化合物。这种机械力化学反应是以表面能为扩散的主要推动力,使PbO扩散至TiO_2颗粒内并在TiO_2颗粒表面形成PbTiO_2,实验证明在PbTiO_2形成以前,PbO及TiO_2二者受机械力的作用,晶型均已发生了变化,锐钛矿转变为金红石,铅黄转变为密陀僧。由铅黄向密陀僧转变的过程中,当密陀僧的容积成分达到75％时即达平衡状态,然而这种机械化学平衡是亚稳的,继续粉磨超过75h后,平衡即遭破坏,密陀僧又重新转变为铅黄。

An this study, it is first found that the reaction of PbO+TiO_2→PbTiO_2 can take place during grinding PbO and TiO_2 mixed powders in stoichiometric proportions in vibration mill.It is considered that the surface energy is s major diffusive force making PbO diffuse into Ti_2 particles and forming PbTiO_2 on the TiO_2 particle surface.Experiments show that before forming PbTiO_2, the crystal phasea of both PbO and TiO_2 have been changed during grinding by the effect of mechano-cemical force, i. e., some anatase converts into rutile and massicot into litharge. The mechano-chemical equilibrium is reached when about 75% volume fraction of litharge are formed in the particles of massicot during grinding. However, this equilibrium is metastable, it will be broken when the mechanical force is exerted continuously up to 75h on the particles and the litharge converts back into massicot thereof.