Study On Explosion And Thermal Decomposition Of ZrH₂-PETN Mixed Explosive

In mining and underground excavation engineering,problems such as sticking of drill pipe and blocking of pass often occur,it usually takes only a small amount of charge to deal with such problems,the method of shaped charge blasting is adopted.Therefore,the explosive charge is required to have the characteristics of high power,miniaturization,safety and stability.In this paper,zirconium hydride（ZrH₂）was used as energy additive and PETN as matrix explosive,ZrH₂-PETN high explosive with different particle size and content of zirconium hydride was prepared,the performance of the system was studied by air explosion experiment and thermal analysis experiment.Zirconium hydride powder was milled by high energy planetary mill,three particle sizes(D₅₀)of were obtained 1.99μm、8.63μm、57.77μm zirconium hydride powder.It is found that the particle size of zirconium hydride powder decreases with the increase of milling time until it becomes stable,and the particle size distribution becomes narrow gradually.XRD results show that ball milling has no effect on the hydrogen storage structure of zirconium hydride.Therefore,with different particle size and content of zirconium hydride as variables,different specifications of ZrH₂-PETN high explosives were prepared,with the increase of zirconium hydride content,the grain density increases greatly,and the charge volume decreases greatly.The effect of different particle size and content of zirconium hydride on the explosion performance of ZrH₂-PETN explosive was studied by air explosion experiment.The results show that zirconium hydride can effectively enhance the explosion performance of PETN,it contains 10%zirconium hydride and the particle size is 1.99μm,the peak value of shock wave,normal phase impulse and normal phase time of ZrH₂-PETN mixed explosive are increased by 4.7%,8.3%and 2.6%respectively compared with that of passivated PETN.According to the grain parameters and explosion performance test of ZrH₂-PETN mixed explosive,it shows that the energy per unit volume of the mixed explosive is higher than that of the passivated PETN,and the charge density is higher,which is conducive to the miniaturization of the charge.The thermal decomposition characteristics and thermal stability of ZrH₂-PETN high explosive were studied by DSC-TG thermal analysis.The results of thermal analysis show that zirconium hydride has a significant effect on the thermal decomposition parameters of PETN,Due to the high heat capacity of zirconium hydride,during the thermal decomposition process of ZrH₂-PETN explosive,there is a significant thermal dilution effect,the activation energy of PETN is increased by thermal dilution,the activation energy changes with the particle size of zirconium hydride as E_PETN<E_1.99μ_m<E_8.63μ_m.Furthermore,the stability of ZrH₂-PETN explosive was judged according to the accelerating decomposition temperature(T_b0)and thermal explosion critical temperature（T_P）,the results show that the compatibility of zirconium hydride with PETN is general,When the particle size of zirconium hydride is1.99μm,the stability of ZrH₂-PETN explosive decreases,when the particle size is 8.63μm,its stability is enhanced,this indicates that the small size zirconium hydride can promote the thermal decomposition of PETN.In general,the thermal decomposition temperature of mixed explosives is much higher than the ambient temperature,which does not affect the safety of ordinary engineering conditions,if it is used in high temperature underground engineering environment,it is necessary to further improve the thermal stability of the mixed explosive.In order to explore the effect of zirconium hydride on the thermal decomposition mechanism of triamcinolone acetonide,the most probable mechanism function of thermal decomposition of ZrH₂-PETN explosive is calculated,the results show that both ZrH₂-PETN and PETN have random nucleation and subsequent growth mechanism,according to the same mechanism function,the thermal dilution effect of zirconium hydride does not affect the thermal decomposition process of PETN.