Macro-dynamics Study Of The Structure Of The Mechano-chemical Preparation Of Zinc Ferrite And Hydroxyapatite Process

As a kind of overlapping disciplines developed in recent years,mechanochemistry has been applied successfully in various field, whichdisplays a great prospect of development. However, study on themechanochemical theory is insufficiency and a clear understanding inreaction process is absent up to now. Therefore, it is necessary to explorethe regulation of kinetics and structure evolution in mechanochemicalreaction process.In this dissertation, kinetic model, reaction mechanism and the effectof various factors in the mechanochemical synthesis of zinc ferrite andhydroxyapatite has been investigated by using X-ray diffraction andstructural macrokinetics theory for reference. The regulation of phasestructur parameters on crystalline size, micro-strain and lattice constanthas been also studied in mechanochemical reaction process.Several of conclusions had been abtained by the study.(1) The mechanochemical reaction process can be divided into threestages: the inducement stage, acceleratory stage and deceleration stage.(2) The synthesis reaction is a nucleation growth controlled process,which can be described by Aurami-Erofe'ev equation.(3) The phase structure changes carry out by stage in grindingprocess. The crystal size of ferric oxide decreases and microstrainincreases at first, and then the crystal size of ferric oxide decreases nolonger and microstrain increases continuously. The lattice constant beginsto increase obviously at the subsequent stage. At the late reaction, both ofthe crystal size and microstrain of zinc ferrite increase, in which the mainfactor is the increase of crystal size at the beginning, and then becomesthe increase of microstrain.(4) The process of mechanochemical synthesis hydroxyapatite is atwo-step reaction, and generate intermediate product of dicalciumphosphate dihydrate. There is a "explosive" phenomenon in the second reaction. The main reason is that the mechanochemical grinding lead tothe increase of intermediary product potential, and the decrease of thereaction energy barrier. It quickens the diffusion and nucleation rate andthen strengthen the reaction kinetic process.(5) The stronger the grinding intensity and the more negative theGibbs free energy are, the larger the reaction rate constant is. Theabsorption of grinding medium inhibits the mechanochemical reactionand the reaction effect decrease in the sequence of air, water and alcohol.