Study On Preparation And Thermal Properties Of Al₃Zr/Al Composite Fuels

Metal fuels were counted as an important component of propellants and hybrid explosive.In this paper,in order to improve the ignition and combustion performance and obtain a new type type of metal composite fuel with high density,high volumetric combustion enthalpy and complete combustion,Al₃Zr/Al system composite alloy fuels with excellent performance were prepared by alloying of Al and Zr.Under the condition of ensuring volumetric energy,the fuel density and combustion property were improved.In this paper,Al₃Zr/Al and Al-Zr-Eu composite fuels with different ratios were successfully prepared using non-consumable arc melting technology,levitation melting,and close-coupled gas atomization.These composite fuels were characterized by modern analysis techniques such as laser particle size analyzer,XRD,SEM,EDS,TG-DTA and DSC.The results showed that the powders prepared by the new process were homogeneous and had high degree of spherical shape.There were obvious grain boundaries on the surface,and a special structure that intermetallic compound Al₃Zr embedded in the matrix Al formed in the interior of Al₃Zr/Al composite fuels.TG-DTA results showed that,compared with pure Al powder,the exothermic reaction of Al₃Zr/Al composite fuels is ahead,weight gain is more obvious,the highest weight gain was up to 71.2%,which indicated that Al₃Zr/Al composite fuels had a higher thermal reactivity,the reaction was more complete.The DSC results showed that Al₃Zr powders exotherms at 960°C under O₂ atmosphere,which is one of the important reasons for the concentrated heat release of Al₃Zr/Al composite fuels.For the Al-Zr-Eu comosite fuels,the addition of Eu made the micro-nano structure formed inside the Al-30Zr-Eu composite fuels.This micro-nano structure contributed to the oxidation of the Al-30Zr-Eu composite powders.The results of TG-DTA showed that Al-30Zr-Eu composite fuels had higher thermal reactivity than Al₃Zr/Al composite alloy fuels,and the heat release was more concentrated with the increase of Eu content.When the Eu content was 3 wt.%,a more concentrated exothermic reaction and a more pronounced weight gain were exhibited,and the weight gain reached 66.5%,which was twice that of the Al-30Zr composite fuels.In order to further study the thermal properties of Al₃Zr/Al composite fuels,the combustion enthalpy of alloy fuels was determined by oxygen bomb experiments.The pressure changes within oxygen bombs in the combustion process of Al₃Zr/Al composite fuels were monitored simultaneously.The results showed that with the increase of Zr content,the gravimetric combustion enthalpies of Al₃Zr/Al composite fuels were linear downward trend.Meanwhile,gravimetric combustion enthalpies were also on the increase with the increase of pressure.When the pressure was higher than 2.5 MPa,the volumetric combustion enthalpies had an overall upward trend with the increase of Zr content.When the pressure was lower than 2.5 MPa,the volumetric combustion enthalpies tended to increase first and then descended.For Al-Zr-Eu composite fuels,with the increase of Eu content,the gravimetric combustion enthalpies of Al-Zr-Eu tended to decrease linearly.When the Eu content was 3 wt.%,both the high oxidation degree and the high combustion enthalpy can be achieved.The maximum pressurization rate?dP/dt?_max of Al₃Zr/Al composite fuels increased exponentially with the increase of Zr content when burned at 3MPa.When the gas pressure in the bomb reaches a maximum value,the gas temperature in the bomb meeted the following rules:the temperature decreases linearly with increasing Zr content and increases with decreasing gas pressure.Both Al₃Zr/Al compoite alloy fuels and Al-Zr-Eu composite fuels had relatively excellent thermochemical activity with high density and high volumetric combustion enthalpy,which made them have potential application prospects in the field of propellants and explosives.