Mapping of Aluminum Particle Dispersion in Solid Rocket Fuel Formulations

Composite specimens consisting of two different kinds of hydroxylterminated polybutadiene (HTPB) loaded with either micron-or nanometer-sized Al powders were synthesized. The spatial distribution of the particles was investigated with a combination of Raman spectroscopy, atomic force microscopy (AFM), and scanning electron microscopy (SEM). The tested specimens were prepared by different manufacturing procedures to inhibit particle clustering. Although the dispersion of nano-sized Al particles was the primary interest, micron-sized Al was also used as a reference. Some specimens were prepared by ultrasonicassisted mixing, others by a simple mechanical mixing procedure, and further specimens by a mechanical mixing process with the addition of dispersing agents (used commercially in pigment and coating applications to reduce inter-particulate attraction forces between particles). Spatial mapping of the CDO Raman mode associated with the HTPB was used to quantify the dispersion of the micron-sized Al particles. Tapping mode AFM and SEM measurements were used to identify the dispersion of both the micron-and nano-sized Al particles. The presence of clusters composed of many nano-sized particles was also identified and their size measured. The results obtained show the potential of these characterization techniques in evaluating the effectiveness of the manufacturing processes of the tested solid fuels and of the examined dispersion processes.