Mechanochemical Synthesis Of ZnO/Brucite Composite Powders

ZnO has the disadvantages of high cost, un-environmental friendly, high consumption of energy, and so on. It is an effective way to relieve these problems that preparing core-shell type composite powder with ZnO as filming agents and other low-cost mineral as nucleating agents through mechanochemical method. In this paper, the optimal technical parameters and composite mechanism of preparing core-shell type ZnO/brucite composite powders by mechanichemical method were discussed on the basis of the research of mechanichemical effects between brucite and ZnO particles during grinding process and the the interaction between brucite and ZnO particle mixed wet grinding system.The results showed that the primary effects of burcite and ZnO particles were forming fresh surface and producing lattice defect in the wet grinding system, respectively. During the grinding process, particles activated and formed abundant associating hydroxide radical. Meanwhile, solubility of brucite was heightened owing to strengthening of the interaction between H2O and the surface groups on the surface of activated particle. After the ionic concentration risen to a certain amount, recrystallization took place. Under the combined effects of mechanical grinding and recrystallization, when grinding for less than 3 h, brucite crystal size decreased and lattice deformation increased, and then the both changes were fluctuant after 3h, while the changes of ZnO were fluctuant all the time. However, disordering of the crystal structures of ZnO and brucite in mechano-grinding system was the main tendency. The electron bond energies between Zn and O decreased and the oxidation degree of Zn reduced.Mechano-grinding and NaOH both could lead to hydroxylation on the surfaces of brucite and ZnO particles in the mixed grinding system. Composite powders were prepared through dehydration and condensation between hydroxide radicals of ZnO and brucite particles. Meanwhile, [Zn(OH)4]2- dissociating in water also dehydrated with hydroxide radicals of brucite particles, which promoted the preparation of composite powders.The optimal process parameters of ZnO/brucite composite powder prepared in the wet grinding system: (1) dispersing technology of ZnO particles: concentration of dispersing system 50%, triethanolamine 1%, dispersing time 1h.(2) mechano-grinding technology of brucite particles: grinding system concentration 50%, triethanolamine 0.5%, the mass ratio of grinding medium to brucite 5:1, grinding time 3h, grinding rotate speed 1350rpm.(3) preparing technology of ZnO/brucite composite powder: the mass ratio of ZnO to brucite 1:1, grinding time 3h, NaOH 30%, the mass ratio of NaOH, grinding medium to the total mass of ZnO and brucite 3:10 and 5:1, respectively, grinding rotate speed 1350rpm.