Alcohol-thermal Synthesis Of Core-shell Structured Al@CuO Nanothermite And Its Reactive Properties

Metastable intermixed composites,also known as nanothermite,have attracted much attention in the field of nanoenergetic composites in recent years due to their advantages of high volumetric energy density and high energy release rate.In order to solve the problem of uneven mixing and inadequate contact between the reactants of the nanothermite prepared by the traditional physical mixing method,this paper obtains core-shell structured Al@CuO based on the one-step method of alcohol-thermal technology,and the heat release characteristics,ignition and combustion characteristics and reaction mechanism have been investigated in this paper.The main research contents and results are as follows:(1)With copper acetate as the precursor and ethanol as the solvent,Al@CuO composite particles were prepared by in-situ coating of nano CuO on the surface of Al powder by alcohol-thermal method.XRD and XPS results show that the product has high purity and no other impurities are detected.SEM and TEM observations showed that CuO with a particle size of about 10 nm closely combined with nano Al to form nominal core-shell structure,while CuO grew in situ as a nanosheet layer on the surface of micron Al to achieve tight coating.(2)The reaction peak type,exothermic peaks,onset temperature and apparent activation energy of Al@CuO samples prepared by alcohol-thermal method and physically mixed Al/CuO samples were compared and analyzed through thermal analysis experiments.The results show that the two samples appeared two exothermic reaction,with the increase of stoichiometric ratio(?),the first exothermic peak becomes more and more obvious,while the second exothermic peak tends to be weak,and the total heat release first increases and then decreases.When?is at 1.5-5,compared with Al/CuO,the total heat release of Al@CuO increases by 21.3%-38.4%,and the onset temperature of the first exothermic peak decreases by 7.2-23.1°C.The apparent activation energy is reduced by 20.1%-25.5%.(3)The ignition and combustion characteristics of Al@CuO and Al/CuO are compared through hot wire ignition experiment,constant volume combustion experiment and high-speed photography in an open environment.The results show that there is no significant difference in the ignition delay of the two samples,but the ignition energy of Al@CuO is generally lower than that of Al/CuO.And the peak combustion pressure,pressure rise rate as well as combustion luminescence intensity of Al@CuO are all higher than that of Al/CuO.In addition,the stoichiometric ratio has a greater influence on the combustion performance of the thermite.As?increased from 0.75 to 5,the peak pressure,pressure rise rate and maximum light intensity all showed a trend of first increasing and then decreasing,and the burning time showed a trend of first decreasing and then increasing.The Al@CuO sample showed the most excellent combustion performance when?was 1.5,which peak pressure,pressure rise rate as well as maximum light intensity are 1.6 times,4.2 times and 1.5 times that of Al/CuO respectively,and the burning time is shortened by 63%.(4)Through the analysis of the microscopic morphology and structural composition of the product,and the reaction mechanism of the sample during the thermal analysis and the combustion process are studied respectively.The results show that Al@CuO undergoes a thermite main reaction at 500-660°C,but the reaction at this stage is not complete during thermal analysis.The intermediate products mainly include Al,CuO and a small amount of Cu,Cu₂O and Al₂O₃.When heating temperature reaches 1000°C,the thermite reaction is complete,and the final reaction products are Cu,Cu₂O and Al₂O₃.The size of the combustion residue of Al@CuO samples(3-10?m)is smaller than that of Al/CuO samples(5-20?m).When?is between 0.75-1.5,the combustion products are Al₂O₃,Cu₂O and Cu;when?>3,in addition to the main reaction of thermite,excess fuel Al participates in the alloy reaction to produce Al₂Cu and Cu Al O₂.