Explosion And Safety Performance Of RDX-based Metal Hydride Composite Explosives

Persistent effort has been made on promoting the explosion property and work capacity of energetic materials.High-combustion-heat metal powder is usually added to enhance the explosion parameters,such like explosion heat.However,it is difficult to acquire a balanced formula attributed to the limits of the metal additive.To obtain more enhanced and balanced explosives,new energetic additives are wanted.The high combustion heat of metal hydrides makes them an excellent propellant fuel and an attractive kind of energetic materials.To date,research on the application of metal hydride in high composite explosive was still limited.Therefore,it is significant to study the explosion property and safety of metal-hydride composite explosive.In present research,influence of particle size and mass fraction of different metal hydrides on the air and underwater explosion performance of composite explosive was studied experimentally and theoretically.Furthermore,the stability and storage performance of RDX-based metal hydride composite explosive was investigated by thermal analysis and ambient storage tests.Firstly,Two typical binary metal hydrides,TiH2 and MgH2 were introduced into the RDX based explosive composites(RDX-MHx composite explosive).Particle distribution of titanium hydride(TiH2)during the ball mill process was studied by milling it with different time.Scanning electron microscope(SEM)pictures showed that particle size decreased quickly at the initial stage,and homogeneous,super fine TiH2 powder was obtained after 4-hour milling.Application of TiH2 in energetic materials was investigated by preparation of TiHz/RDX.Air explosion experiments were carried out to investigate the influence of different titanium hydride(TiH2)contents and sizes on properties of RDX-based TiH2 composite explosive.Meanwhile,the solid explosion products were analyzed.Results show that the explosion properties of composite explosive are improved with TiH2 size decreasing.Compared to standard RDX.the peak overpressure,positive duration and positive impulse of composite explosive with TiH2 content of 20%and size of 0.96um increase 3.8%,12.7%and 14.0%,respectively.As the content of 0.96μm TiH2 increasing from 10%to 20%,the explosion positive impulse increased 7.0%and the peak overpressure decreased 5.1%.Variance analysis indicates that titanium hydride size has a significant impact on properties of composite explosive,and there was an interaction between titanium hydride content and size.Analysis of solid explosion products revealed that the TiH2 is oxidized into TiO2 during explosion of composite explosive.Based on the results of air explosion experiments and solid explosion products analysis,a theoretic model was built to predict the reaction of binary metal hydride during the detonation and explosion.Experiments were conducted to study the underwater explosion performance of RDX-based Titanium Hydride(TiH2/RDX)composite explosive.Cylinder charges with different TiH2 particle sizes and contents were prepared and tested.Explosion parameters like peak overpressure,impulse,specific shock energy and bubble energy were analyzed.It was notable that underwater explosion performance of TiH2/RDX composite explosive was promoted by addition of small particle size TiH2(D50=0.96μm),in which case increasing TiH2 content also showed a favorable effect.The maximum increments of specific initial shock energy,bubble energy,and total energy were 10.5%,6.4%,and 7.1%respectively.However,with bigger TiH2 particle sizes(D50=20.78 μm,D50=136.74 μm),the explosion parameters and the TiH2 content showed a negative relationship,which revealed that TiH2 particle size played an important role in determining the reactivity of TiH2,meanwhile,the interaction between TiH2 particle size and content was significant.Explosive with 10%MgH2 exhibited the best shockwave parameters,peak overpressure,specific impulse and specific shock energy of which promoted by 5.7%,7.0%and 8.4%respectively.Whereas,density specific energy of RDX-based titanium hydride explosive increased significantly attributed to the high density of TiH2.Thermal analysis(TG-DTA)was carried out to study the stability and compatibility of TiH2/RDX composite.Experimental results revealed that the addition of TiH2 will affect the thermal dynamics and peak temperatures of decomposition,resulting in a weakened stability.Meanwhile,a 2-year ambient storage test of metal hydride reactants and RDX-metal hydride explosive composites was conducted to evaluate the safety and stability.X-ray diffraction(XRD),thermogravimetry(TG)and differential thermal analysis(DTA)were then conducted to analyze the aged samples.Results revealed that TiH2 and its explosive composite showed an excellent storage stability due to the formation of thin TiO2 film.Whereas,Mg(OH)2 and Mg were found increasing with time in both MgH2 and its explosive composite,of which hydrolysis and decomposition of MgH2 were the main mechanisms.Mechanical strength of aged charges of RDX based MgH2 explosive also degraded significantly ascribed to the released hydrogen.Research results showed that the explosion performance of composite explosives was significantly promoted by addition of metal hydrides,which revealed its potential application.The enhanced explosion property and excellent storage stability of RDX-based titanium hydride composite explosive made it an attractive explosive system.The research also provided useful informants for future study on metal-hydride composite explosive.