The Characteristics Of Thermal Oxidation And Dynamic Combustion Agglomeration Of Aluminum Particles

Aluminum particles are important energy-containing components of aluminum-containing solid propellants.It's of great significance to study the reaction characteristics of aluminum particles for the research and application of propellant.In this paper,three different characteristics of micron aluminum powders were selected.Firstly,the physical and chemical properties of aluminum powders were tested,including particle size distribution,microscopic morphology,elemental composition and content,specific surface area,pore structure,element morphology and thickness of oxide layer.Thermal oxidation characteristics of aluminum particles,ignition combustion characteristics and dynamic combustion agglomeration process were tested by using thermal analysis techniques,laser ignition combustion test system and dynamic combustion test system.It can be found that most probable mechanism functions of thermal oxidation of the samples is the boundary control model function R3:G(a)=1-(1-?)1/3 in the temperature range from 550 to 1110?.The oxidation process of micron-Al powder is divided into three distinct stages:initial oxidation stage,below 550?,the accelerated oxidation stage,550?670?,the dramatic oxidation stage,670?111?.In different oxidation stages,the alumina layer on the surface of the particles has undergone growth thickening,tensile rupture and other processes,with the Al2O3 crystal form changes from amorphous to ?,? and ?-Al2O3.It proves that the smaller the particle size is,the deeper the degree of oxidation is.Aluminum powder with smaller particle size has lower apparent activation energy and is more easily oxidized.Particles own characteristics,reaction atmosphere types and content and environmental pressure have a very large influence on the ignition and combustion characteristics of aluminum particles.By increasing the specific surface area of the particles,reducing the initial oxide layer thickness,enhancing the oxidation of the atmosphere and improving environmental pressure,can shorten the ignition delay time,get higher combustion temperature and combustion intensity,greatly improve the final combustion efficiency.Al particle must undergo phase change,reunion,ignition,combustion and aggregation in its combustion process.Al particle will occur gas phase combustion and form Al2O3 smoke(consists of oxide particles smaller than 1 ?m),wich is one of the factors that cause Al to agglomerate.Dissolution reaction and diffusion reaction simultaneously exist in the static thermal oxidation and dynamic combustion of micron aluminum particles.