Preparation Of High Activity Flake Aluminum Powder And Its Application In Composite Solid Propellants

Metal additives is a kind of important components of composite solid propellants.Aluminum powder is the primary and effective metal additive because of its low density and high thermal energy.However,it is indistinctive in improving the performance of propellants due to low active-aluminum content in general aluminum powder.In this paper,the high-active flaky aluminum powder was prepared through the method of wet mechanical ball milling and applied to the Al/AP/HTPB three component solid composite propellant.Then TG-DSC-DTG,thermal decomposition kinetics,mechanical sensitivity,and the rate of explosion heat and combustion were adopted to investigate the influence of the high-active flake aluminum powder on the performance of propellant system.And research contents and results of this paper are as follows:First of all,we used ’wet mechanical ball milling’ method to prepare high-active flaky aluminum powder.The optimal experimental conditions were:ethyl acetate as solvent,4 wt%stearic acid as grinding aids the speed of the ball mill 1100 rpm,the ball/material ratio 20:1 and the milling time 4 h.And the active-aluminum content of flaky aluminum powder obtained under the conditions was 97.13%.SEM and XRD results showed that the ball milling only changed the morphology of aluminum powder and crystal form was not changed.The particle size(d50)of aluminum powder decreased from 13.9 μm to 1.108 μm,which was measured by laser particle size analyzer.Secondly,the high-active flaky aluminum powder prepared by mechanical milling was applied to Al/AP/HTPB ternary composite solid propellant.And the influence of AP grade,Al powder grade on the preparation technology of propellant and curing time were studied.The results showed that with the increase of the ultrafine AP content in the system,the apparent heat of decomposition of the propellant increased.As the content of flake aluminum increased,both of the apparent heat of decomposition of the propellant system and the viscosity of the whole system increased.The addition of flaky A1 powder did not have obvious effect on the curing time of the propellant system.Compared with the propellant system containing spherical Al powder,the thermal decomposition tendency of that containing flake Al powder did not change,but the decomposition peak temperature of each stage increased.Finally,the effects of flaky aluminum and spherical aluminum powder on the thermal decomposition,mechanical sensitivity,detonation performance and burning rate of Al/AP/HTPB composite solid propellants were investigated.Compared with spherical aluminum powder,the apparent activation energy of propellants decreased from 265.374 kJ·mol-1 to 142.086 kJ·mol-1 with the addition of the flaky aluminum powder.Besides,results showed that the impact sensitivity decreasing from 44.66 cm to 39.81 cm,impact sensitivity increasing by 10.85%,the friction sensitivity increasing from the original 32%to 40%,the average burst heat of the whole system increasing by 11.6%,from 7558.7 J·g-1 to 8436.1 J·g-1,and the combustion rate increasing from 1.343 mm/s to 1.61 mm/s with an increase of 19.8%.