Research Of Nano-Mn(Zn) Ferrite Synthesis By Detonation Of Emulsion Explosive

It was a common goal for industry that nano-Mn(Zn) ferrite could be prepared by a rapid method with low cost since Mn(Zn) ferrites were more and more broadly applied in industry. In present time Mn(Zn) ferrites were prepared in industry by high temperature solid state reaction, in which the raw powders were ball milled under high temperature and high pressure for a considerably long time which would consume plenty of energy and resource. Although there were many alternative means preparing nano-Mn(Zn) ferrite, however, the defective workmanships meanwhile existed, such as high temperature and high pressure would result in high cost, or complex process would result in uneasy controlled experimental conditions, or organic matters were poisonous to human and environment, such reasons made these methods difficultly popularized in a short time. In the present paper, nano-Mn(Zn) ferrite synthesized by detonation of emulsion explosive was developed in which the ferrite nitrate and manganese nitrate were regarded as main oxidants and AN was regared as auxidiary oxidant respectively, compound oil(the mixture of paraffin wax, vaseline and machine oil with a certain proportion) was regarded as incendiary agent and SP-80 as the emulsifier. Four aspects, that is, the factors effecting nano-Mn(Zn) ferrite synthesis via detonation, preparing process and safety of emulsion explosive, equation of state of detonation products and reaction mechanism of detonation synthesis were investigated in this work, the following achievements were obtained:(1) The crystal structure, morphology, dimension, distribution and magnetism of the prepared powders could be effectively controlled by detonation parameters of explosives. The results indicated that the average dimension of detonation products was reduced with the increasing of explosion velocity, the powders with better dispersity could be obtained from the explosive with RDX content 9.18.wt%, and relatively purer products could be obtained from the explosive with negative oxygen balance, inner phase of AN and high density. The original powders could completely converted into pure phase when they were heated at 280℃for 1h.The max coercive force and specific remanence of the Original nano-MnFe₂O₄ powders were 98.77Oe and 2.35emu/g, and both reduced with the increasing of RDX content(explosion velosity), but RDX content did not obviously effect the specific saturation magnetization and the average value was 20emu/g.The magnetism of the products obtained from high density explosives was prior to that obtained from low density explosive. The magnetism of the powders obtained from explosives with high velosities was relatively better than that obtained from explosives with low velosities, and the magnetism of the original powders was notably influenced by detonation structure of explosives.The max coercive force, max specific remanence and specific saturation magnetization of pure nano-MnFe₂O₄ powders were 105Oe, 38.6emu/g and 4.6emu/g, respectively. The max coercive force, max specific saturation magnetization and specific remanence of pure nano-MnZn ferrite powders were 78.57Oe, 48.39emu/g and 4.27emu/g respectively.(2) A design idea of a new-type emulsion explosive was presented for preparing nano-oxide particles according to the recipe rule of emulsion explosive and the experiments of nano-oxide particles preparation by detonation method and a new-type emulsion explosive containing Fe and Mn elements was prepared. The results indicated that the explosive had large crucial detonation diameter( (?) 50mm), the explosion velocity could arrive at more than 4000m/s. Metal ions could obviously reduce the stability of the explosive, but its storage time was still longer than 24h, which was completely satisfied with synthesis experiments.(3) The code of BKW equation coupling with solid state equation was programmed and the shortcomings of the original BKW code were improved. The detonation parameters of the emulsion explosive containing Fe and Mn elements were calculated. The results indicated that the detonation pressure were ranging from 6GPa to 11GPa, the detonation temperature were ranging from 1500K to 2300K.(4) The chemical and mathematical model of nano-Mn(Zn) ferrite synthesis by explosion was established, the reversible reaction and the components and distribution of the solids in detonation products were investigated and optimized, respectively, and the nucleation and diffusion of the solid products of detonation were simulated. The results indicated that Mn(Zn) ferrite could only form under certain temperatures and pressures, and Mn(Zn) ferrite formed during the course of raped expansion of detonation products. At the duration of detonation reaction, the growing radius of crystal nucleus was 6-16nm.