| As a high-energy ignition powder,boron potassium nitrate ignition powder is widely used in conventional weapons,aerospace and other fields.In the application process,there is a problem that the interaction between boron powder and potassium nitrate is weak and the mixing uniformity is week.Based on the above problems,in order to enhance the stability of the performance of the ignition agent,the subject designed and selected polyol bonding agent to modify the surface of boron powder to increase the distance between the oxidizing group and the reducing group,on this basis,the interface of boric acid and organic cobalt were designed and selected to modify the boron powder to further enhance the interface bonding force between boron and potassium nitrate,improve the mixing uniformity of the system,and study the effect of bonding agent modified boron powder on the microstructure and properties of BPN ignition powder.The details were as follows:(1)The adsorption process of pentaerythritol and erythritol on B{1 1 1}surface was studied by density functional theory.The adsorption strength and mechanism were studied from adsorption energy,density of states and electron density difference.The stable adsorption sites of the two polyols were both at the top position.The adsorption energy of pentaerythritol was higher than that of erythritol,and the adsorption on the B surface was more stable.There was a strong sp~2orbital hybridization and electron interaction during the adsorption of B surface.(2)Molecular dynamics simulation of boric acid and organic cobalt bonding agent multivariate system,used binding energy,radial distribution function,cohesive energy density analysis of interaction strength and type.The interaction strength in boric acid bonding agents was calculated as potassium phenyl trifluoroborate<pinacol phenyl borate<2-nitrophenyl pinacol borate.The order of interaction strength in organic cobalt bonding agents was cobalt isooctanoate<cobalt benzoate<cobalt p-hydroxybenzoate.Simulation analysis showed that the intermolecular interaction between cobalt p-hydroxybenzoate and system components was stronger,which was more conducive to enhance the stability of the system.(3)The pentaerythritol-modified boron powder was prepared by recrystallization process.The particle size of the composite particles was between 1μm and 2.5μm,and the surface shell size was about 50nm.The results of TG-DSC showed that the pentaerythritol-modified boron powder began to decompose at 200°C until 260°C.The addition of 2-nitrophenyl pinacol borate and cobalt p-hydroxybenzoate had no effect on the thermal decomposition of boron powder.(4)Potassium borate nitrate ignition powder was prepared by mechanical mixing process using boron powder modified by bonding agent as raw material.The effects of bonding agent on the micromorphology,element distribution,combustion characteristics and aging properties of boron powder were investigated.The results showed that the boric acid bonding agent can greatly reduce the thermal sensitivity and increase the combustion calorific value of the boron potassium nitrate ignition powder.The organic cobalt bonding agent could enhance the combustion performance of the agent to a certain extent and improve the environmental adaptability.On the basis of pentaerythritol modified boron powder,the thermal decomposition temperature of boron/potassium nitrate ignition powder composed of cobalt p-hydroxybenzoate was547°C,the laser ignition delay time was 4ms,the burning rate was 64.30mm/s,the combustion calorific value was 8166J/g,and the moisture absorption rate was 22.62%.The boron/potassium nitrate igniter powder composed of(amorphous boron powder21.35%,pentaerythritol 2.14%,cobalt p-hydroxybenzoate 0.21%),potassium nitrate70.7%,phenolic resin 4.97%and methyl ethyl ketone peroxide 0.63%is a laser igniter with excellent comprehensive performance.It provides a reference for making boron/potassium nitrate igniter to meet the higher application requirements of pyrotechnic components. |
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