Preparation And Reactivity Of Highly Active Boron Composites

Boron is a significant component of energetic materials due to its high energy release on both a mass and volumetric basis.However,Boron has the disadvantages of easily agglomeration,high ignition temperature and low combustion efficiency which limited the application of boron.Researches show that dispersion and reactivity of Boron can be improved by prepared Boron-based composites.In this paper,Boron-based composites were prepared by different methods,and their properties were studied.(1)The thermal performance of micro Boron and nano Boron was studied by TG-DSC.The results show that the activity of nano Boron is obviously higher than that of micro Boron.But its oxidation reaction rate is slow,and weight gain(about 110%)is far lower than the theoretical(222%).Boron/Y(Y=Viton?PVDF?PTFE)composites were prepared by solvent volatization for improving the activity of Boron,and their thermal performance was studied by TG-DSC.The results show that Viton has the best effect,and PVDF has better effect than PTFE.Viton can improve the activity of Boron and decrease the oxidizing temperature of Boron,decreased by 31.9? for micro Boron,decreased by 15? for nano Boron.(2)Boron/X(X=Mg?Al?.Fe?Mo?Ni)composites were prepared by the wet ball milling for improving the activity of Boron.TG-DSC shows that after adding Fe,the performance of the Boron can be best improved.The peak temperature decreases by 14.8?,the weight gain increases by 17.6%compared with the original Boron.The results of the test of combustion for HTPB/AP propellants show that B/Fe composite is better than other composites for improving the combustion performances of HTPB/AP propellants.The burning rate of HTPB/AP propellants with B/Fe composite in air is 2.39mm·s-1 which is 1.6 times than blank HTPB/AP propellant and 1.41 times than HTPB/AP propellants with original Boron.The pressurization rate of HTPB/AP propellant with B/Fe composite in constant-volume is 24.8kPa·ms-1 which is 1.45 times than HTPB/AP propellant with original Boron.(3)Boron/NC composites with different NC content were prepared by electrospray.TG-DSC shows that the reactivity of Boron in Boron/NC composites can be improved,and the oxidating temperature decreases by about 14?.The oxidation weight and heat release are both the biggest when the content of NC is 5%.The weight gain is 189.2%which is 1.66 times than original Boron.The heat release is 32388J·g-1 which is 1.55 times than original Boron.The test of combustion properties for HTPB/AP propellants with B/NC composites or original Boron shows that the burning rate of propellants with B/NC composites in air increases by 11.4%compared with propellant with original Boron,and the burning rate of propellants with B/NC composites in a cell with a constant-volume increases by 15.9%compared with propellant with original Boron.(4)B/Fe2O3/NC composites with different Fe2O3 content were prepared by electrospray.SEM shows that the Fe2O3 content plays an important role in the morphology of composites.The higher the Fe2O3 content,the better the morphology.TG-DSC shows that the activity of Boron in composites is improved,its oxidation temperature decreases by 116.7? compared with original Boron.The burning rate of HTPB/AP propellants with B/Fe2O3/NC composites or original Boron was tested.The results show that the burning rate of HTPB/AP propellants with B/Fe2O3/NC composites is faster than that of HTPB/AP propellants with B/NC composites.The burning rate of HTPB/AP propellants with B/Fe2O3/NC composites in air is the biggest which is 2.77 times than that of blank HTPB/AP propellant when the rate of B/Fe2O3 is 10/8.The burning rate of HTPB/AP propellants with B/Fe2O3/NC composites in a cell with a constant-volume is increased with the increase of Fe2O3 content.(5)NC,NC/RDX and n-B/RDX/NC fibers were prepared by electrospinning technique.SEM shows that the fibers with diameter less than 100nm were prepared,when the concentration of NC is 7%,the voltage is 18kV,the flow rate is 4mL·h-1,the distance of nozzle top to substrate is 10cm.TEM shows that RDX which is uniformly dispersed in NC/RDX fibers is ellipsoid.The results of the combustion test show that the n-B can increase the burning rate of fibers.The rate reaches the maximum which is 1.84 times than NC/RDX fibers when the rate of n-B/NC is 2/10.TG-DSC shows that the activity of n-B in n-B/RDX/NC fibers is also improved,the oxidation temperature of n-B is up to 46.3 ? in advance.