Study On Fluorination Of Aluminum And Its Application In HTPB Propellant

As a highly energrtic combustion agent,aluminum has a series of advantages,such as high density,low oxygen consumption and high combustion enthalpy,as a result,aluminum is widely used in solid propellant.Aluminum plays significant role on improving specific impulse,and is often used in propellant,explosives,gunpowder.In order to solve the problems raised by the application of aluminum in propellant,for example,aggregation and low combustion efficiency,perfluorinated myristic acid was applied to modify aluminum.Organic fluoride modified aluminum?Al/PF?was added in aluminized HTPB solid propellant,whose impact on the combustion behavior was tested then.First of all,nmAl/C₁₃F₂₇COOH was prepared by in-situ coating method.SEM,TEM,particle analysis and the test of active aluminum were applied to determine the property of nmAl/C₁₃F₂₇COOH.Results show that,compared with the air-passivation nano-aluminum?air-nmAl?,the thickness of oxide layer in nmAl/C₁₃F₂₇COOH was obviously reduced.Although the content of active aluminum was significantly improved about 55%,the content of active aluminum in nmAl/C₁₃F₂₇COOH was still much lower,which was just 44.9%.Secondly,nano?micrometer?aluminum and organic fluoride was used to prepare nmAl/PF,?mAl/PF and 5 different quality ratios nmAl/PF compounds by ball milling method.SEM,thermal analysis,XRD and particle size analysis were applied to determine the properties of compounds.Results show that nano and micrometer aluminum had different states when combined with PF;The lattice state of Al&PF were not changed by ball milling method;Based on the results of theoretical calculation and experiment,the best quality ratio is mAl:mPF=3:7.Then,two series of propellants were prepared based on the 5 micron aluminum HTPB propellant.At the same time,by adding PF,nmAl/PF&?mAl/PF,the combustion properties of four-group propellant and 18?m aluminum contained propellant were studied.Results show that compared with original propellant,the burning rate of propellants contained nmAl/PF&?mAl/PF respectively increased in3,5,7MPa.With the increasing of the aluminum content in milling compounds,the explosion heat and burning rate of propellant had both decreased.In four-group propellant,aading nmAl/PF&?mAl/PF would increase the burning rate of propellant when pressure was higher than 3MPa.The explosion heat of 18?m aluminum contained propellants was higher than the corredponding formula of the first series propellant.Finally,SEM,XRD and particle size analysis were applied to determine the condensed combustion poduct?ccp?of propellant.Results show that in the first series propellant,the dispersion condition of ccp had improved by adding nmAl/PF and?mAl/PF,and the content of?-Al₂O₃??-Al₂O₃ reduced in ccp.The particle size of two propellants that contained nmAl/PF?mAl:mPF=3:7&mAl:mPF=5:5?respectively were relatively lower.In 18?m aluminum contained propellants,the one which contained nmAl/PF had little cotent of?-Al₂O₃.