Study On The Mechanism Of Formation And Thermal Reaction Of Nano-Aluminum/F2604 Composite Particles

Fluorine-containing materials with high stability can react with aluminum powder to form AlF₃ under certain conditions.Its formation enthalpy is higher than that of pure Al-O reaction and can shorten the induction period of aluminum powder reaction.It is widely used to prepare highly reactive nano-aluminum powder?n-Al?composite materials,improving the comprehensive performance of n-Al in the application of fire explosive.In this paper,macroscopic properties and microstructure of composite particles are closely combined with experiments and molecular dynamics?MD?simulation.It provides theoretical support for improving the effect of coating and safety design and comprehensive performance design in the application.The main research work is as follows.Firstly,the coating system of nano-aluminum powder was designed.The dispersion effect on n-Al was studied with subsidence test of different surface modifiers?SPAN80,SDBS,KH550,SE?.MD simulation was carried out to build interface models between Al₂O₃on the surface of n-Al and these modifiers or several typical fluorine-containing materials?PTFE,PVDF,F2604,PFPE?to study the interface interaction under different temperature?298 K⁹00 K?.It was found that KH550 had the best dispersity effect on n-Al.With the increase of temperature,the stability of the interface interaction between the four fluorine-containing materials and Al₂O₃ was F2604>PVDF>PTFE>PFPE.Then n-Al/F2604 composite particles modified with KH550 were designed.Secondly,with regard to the selected n-Al/F2604 composite system,the influence mechanism of solution parameters on its microstructure was studied.The composite particles were prepared with different F2604 content?3 wt%²3 wt%?in different solvent?acetone and ethyl acetate?using electrostatic spray technology.It was found by scanning electron microscope?SEM?and differential scanning calorimeter?DSC?that acetone as solvent can make the morphology of composite particles more uniform neat and achieve more heat release.When the content of F2604 was less than 13%,the composite increased with increasing particle diameter as F2604 proportion.When the content of F2604 continued to increase,the particle size distribution of composite particles became uneven,with irregular shape and obvious spinning phenomenon.MD simulation results show that the diffusion coefficient of F2604 in solvent is one of the important factors affecting the molecular chain morphology when it is coated with n-Al.The unit binding energy between F2604 and n-Al is mainly composed of electrostatic interaction energy?75%⁹3%?and van der Waals interaction energy?6%²2%?.The content of fluorine rubber influences the microstructure of the composite particles through intermolecular electrostatic interaction.Finally,the thermal reaction mechanism of n-Al/F2604 composite system was studied.Abinitio molecular dynamics?AIMD?simulation was used to establish decomposition model of F2604 and thermal reaction model of Al₂O₃/HF,to study the situation of bond fracture and formation in the reaction process,and to verify each other with mass spectrum fragments detected by Thermogravimetric-Mass Spectrometry?TG-MS?.The results show that much HF is generated when fluorine rubber is decomposed,and C-C bond is broken to form aromatic ring.In the Al/F2604 composite system,HF generated by fluorine rubber decomposition can combine with Al₂O₃ on the surface of aluminum powder to generate H₂O,indicating that F in fluorine rubber can activate Al₂O₃.