Atomic Simulations For Packing Changes Of Al Nanoparticles Under Temperature And Compression

In pursuit of higher energy and better combustion performance,Nano metal powders have been widely used and developed in energetic systems such as propellants and gunpowder.Nanomaterials are different from traditional materials.Due to volume effects,surface effects,Its mechanical properties and thermal stability are closely related to particle size and shape.When the nano metal powder is actually used in the energetic system,it is necessary to consider the change of the atomic packing structure with temperature and compression.Al has a wide range of applications due to its abundant reserves and easy preparation.Al nano metal powder has broad application prospects in energy industry and energetic system with its excellent performance.In order to solve the actual needs,it is very important to study the effects of temperature,external force and particle size on the changes of atomic stacking structure in Al nanoparticles.In this paper,nearly 40 Al nanoparticles with different particle sizes were simulated on the atomic scale by molecular dynamics.The experiment simulates the continuous heating process of Al nanoparticles and the uniaxial compression process at 300K and 500K respectively.By comparing and analyzing the atomic average potential energy,distribution function,atomic stacking structure and bond pair analysis of Al nanoparticles,the following calculation results were obtained:The melting temperature of Al nanoparticles is lower than the melting temperature of Al blocks.As the particle size of the Al nanoparticles increases,the melting temperature gradually approaches the value of the block.At lower temperatures,the surface atoms will undergo significant migration and rearrangement.The internal atoms will only vibrate around the lattice.And the shape of the particles will change significantly.At higher temperatures,the atoms are completely out of equilibrium and the particles melt.When the applied load is small at 300K,the upper and lower surface atoms are squeezed into the sub-surface layer.Internal atoms still maintain a face-centered cubic structure.When the applied load is large,the internal atoms begin to slip,and a large number of defects and atomic planes are generated in the particles.The shape of A1 nanoparticles shows obvious compression deformation.The larger the particle size of the Al nanoparticles,the greater the resistance to the load.The resistance of each surface to the load is also different.When a load is applied at a higher temperature below the melting point,surface atoms are rearranged,internal atoms are more likely to slip than at room temperature,and the number of atomic misalignments in the particles is significantly reduced.The resistance of the A1 nanoparticles to the load decreases with an increase in temperature.