The effect of surface modification of aluminum powder on its flowability, combustion and reactivity

Surface modification of aluminum powders for the purpose of flow improvement was performed and several samples were prepared. Correlations between the flowability and reactivity for these powders as well as for the initial untreated aluminum powder were established. The powders were characterized using Scanning Electron Microscope (SEM), particle size distribution, angle of repose flowability test, Constant Volume Explosion (CVE) combustion test, and Thermo-Gravimetric Analysis (TGA). The surface modification of micron-sized aluminum powders was done by: (1) dry coating nano-particles of silica, titania and carbon black onto the surface of spherical aluminum powders and (2) chemically and physically altering the surface properties of the same powders with methyltrichlorosilane. All surface modifications improved flowability of the powders. CVE measurements indicate that powders with an improved flowability exhibit improved combustion characteristics if the powder treatment does not add an inert component to aluminum. The TGA results do not show significant differences in the reactivity of various powders. Based on combined flowability and CVE characteristics, the silane modified material gave the best results followed by the powders dry coated with carbon, titania and silica, respectively.