Research On Preparation And Thermal Properties Of Boron- Containing Alloy Fuels

Aluminum and boron powder are widely used as metal fuels in the field of solid propellants and explosives,but both fuels have the disadvantage of incomplete combustion.In order to improve their combustion performance,this paper has prepared Al-B alloy powder and added lively metal elements Eu and Li to improve the combustion efficiency of the alloy fuel.The effects of B content and oxygen partial pressure on the thermal properties of the series alloy fuels are compared.In this paper,Al-B,Al-B-Eu and Al-B-Eu-Li alloy powders were prepared by non-consumable arc melting technology and inert gas atomization method.All powders have good sphericity and dispersion.The phase composition and microstructure of the three series of alloy powders were characterized by XRD and SEM.The thermal oxidation characteristics of the alloy powder were investigated by TG-DTA.The combustion characteristics of the alloy powder were measured by oxygen bomb tests.Studies have shown that the intermetallic compound of AlB₂ in the Al-B alloy distributed as fine dendritic crystal.The initial oxidation temperature of all Al-B alloy powders are lower than that of pure aluminum powder.As the B content increases,the total weight gain and total released heat of the Al-B alloy powder increase.The oxygen bomb combustion experiment shows that the combustion enthalpy of the alloy powder also increased with the increase of B content.However,the combustible elemental aluminum is still detected in the combustion products of the Al-B alloy,which means insufficiently burned.In order to improve the combustion performance of the Al-B alloy,active metals Eu and Li are added to the alloy to support combustion.It was found that the surface of Al-B-3Eu alloy particles exhibits uniform reticular gap structure.Al-3.5B-3Eu undergoes intense oxidation and heat release at 1110°C,and the efficiency of weight gain is 53.66%.When the Eu content is constant,as the mass fraction of B increases,the combustion enthalpy of the Al-B-Eu alloy powder increases first and then decreases.The maximum combustion heat release of Al-3.5B-3Eu ternary alloy powder is measured at the partial pressure of oxygen of 3.0 MPa.Under the synergistic action of two intermetallic compounds,Al₄Eu and B₆Eu,a special reticular metallographic structure is formed in the Al-3.5B-3Eu alloy powder.The preferential oxidation expansion of the intermetallic compounds causes the fuel particles to crack during the combustion process.The phenomenon makes the Al-3.5B-3Eu alloy powder burn more vigorously and fully than the Al-B alloy.The Al-B-Li-Eu alloy particles have a smooth surface and a high sphericity,and exhibit a micro-nano reticular grain boundary.Al-B-Li-Eu undergoes a strong oxidative exotherm at 1036°C.The combustion enthalpy of the Al-B-Li-Eu alloy powder increases as the oxygen partial pressure increases,and combusted completely under high pressure.During the combustion process,the grain boundary are preferential oxidated and consumed,resulting in the formation of a porous structure on the surface,which facilitates the diffusion of oxygen into the interior of the particle to accelerate the burning rate of the particle,and the final product exhibits a porous shell structure.In summary,the three series of Al-B,Al-B-Eu and Al-B-Eu-Li alloy powders prepared by the aerosol method have superior oxidation and combustion properties compared with the pure Al powder,which provides new design ideas of development of high-activity boron-containing alloy fuels.