Research On Preparation And Thermal Properties Of Al-Li And Al/PMF (Carbon Monofluoride) Energetic Fuels

Al powder as a metal fuel,is a major component of solid propellant,but some difficult issues are encountered in its application,such as high ignition temperature,incomplete combustion and severe surface agglomeration phenomenon.In this paper,Al-3Li(wt.%)alloy powder and Al/PMF composite particles(Al/PMF 95/5% and 90/10%)were prepared by close-coupled gas atomization(CCGA)and two-step mechanical activation(MA),respectively.The particle size distribution,phase composition,morphology and thermal properties were characterized and analyzed by a laser particle size analyzer,XRD,SEM/EDX,TG/DTA.Oxidation mechanisms were also explored.To avoid severe surface oxidation of high reactivity alloy powder in storage,Al-3Li alloy powder was coated with a continuous and uniform iron layer by modified chemical liquid deposition method.And thermal stability of both powders before and after coa ting was studied.The results show that gas atomized Al-3Li alloy powder has a highly spherical shape without agglomeration phenomenon.Iron coated composite particles exhibit core-shell structure and the outer iron film is very uniform and compact.Significantly enhanced thermal reactivities of Al-3Li alloy powder and Fe/Al-3Li composites are achieved compared with pure Al powder,which include sharp mass increase and intensive heat release.Thermal stability studies show that,after coating,the reactivity decay rates of alloy powder decrease significantly,and the mass combustion enthalpies remain basically stable,which demonstrate that iron coating indeed improves aging stability of Al-3Li alloy powder.Al/PMF composite particles were prepared by two-step mechanical activation.With the increase of PMF content,the mean particle diameter of composite particles decreases from 20.6?m to 13.7?m.The combustion enthalpies of Al/PMF 95/5% and 90/10% composite particles are respectively 22.26 kJ/g and 21.51 kJ/g.Compared with pure Al powder,Al/PMF 95/5% and 90/10% composite particles all show significantly enhanced thermal reactivities and the oxidation onset temperature reduces.In order to evaluate the application of prepared powders in the propellants,this paper has researched the effects of Al-3Li?Fe/Al-3Li and Al/PMF energetic fuels on the thermal decomposition behaviors of ammonium perchlorate(AP).Results show that,Fe/Al-3Li composites have a strong catalytic effect on the low and high temperature decomposition of AP.Al/PMF particles have a better catalytic effect of low temperature decomposition on AP than that of high temperature decomposition.Al-3Li alloy powder promotes low temperature decomposition of AP,but has inhibitory effect on high temperature decomposition of AP.In conclusion,Al-3Li alloy powders before and after coating and Al/PMF composite particles all exhibit superior thermal reaction activities and have different catalytic effects on the decomposition of AP,which indicate potential application prospect in energetic field.