Passivation of unpassivated aluminium nanoparticles using C 13 F 27 COOH is reported with materials containing as much as 32 . 95%Al. Characterisation data, including scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and attenuated total reflectance Fourier transform infrared (ATR FTIR) spectrometry, indicate that the C 13 F 27 COOH molecule binds to the surface of the Al particle, protecting the surface from oxidation in ambient air. The fast reaction capability of the Al-C 13 F 27 COOH material was investigated using two different means. Response of the material to strong shock was analysed using the small scale shock reactivity test (SSRT). SSRT results show that the Al-C 13 F 27 COOH material formulated with cyclotetramethylenetetranitramine (HMX) and hydroxyl terminated polybutadiene (HTPB) binder produced a significantly larger dent than comparable conventional Al specimen. Additionally, laser ablation/ignition studies of the prepared Al-C 13 F 27 COOH material demonstrate the fast reaction capability of the material.
Examination with atomic force microscopy has revealed apparent shear-type cleavage steps with heights as small as 0.05 nm, smaller than the size of cyclotrimethylenetrintramine (RDX) molecules, on the fracture surfaces of crystals that were subjected to aquarium shocks of 61.6 or 129 kbar, both greater than the pressure (38 kbar) required for the alpha-to-gamma phase transformation. The shocked centimeter size, originally transparent crystals became opaque and white from prolific fractures and internal cracks that are associated with their breakup into nanocrystallites of sizes extending from 500 down to 20 nm. The submolecular steps are related geometrically to the macroscale (K∥) fracture mechanics mode of shear fracturing that has obvious consequences at the nanoscale level for nonregistry between molecules across the crack surfaces. The results are of interest in relation to lattice trapping of crack fronts and as a contribution to the possibility of deformation-induced chemical decomposition/detonations.
Microwave interferometry appears to be a promising method for the study of wave and mass velocity in shocked dielectric materials. This paper discusses the mathematics concerning the frequencies and amplitudes in the microwave reflections from the shock wave and from an impacting piston which drives the shock into a nonreacting porous solid. Methods for the determination of the state variables in the compressed region between the shock wave and the piston are given. In this paper, these methods have been confirmed by experimental measurements in nonenergetic materials in which there is no ionization from chemical reaction. The microwave reflection from the shock wave traveling through an inert media is shown to result from a dielectric discontinuity at the wave front. Studies on energetic materials (explosives and propellants) are considered in a companion paper where ionization associated with the chemical reactions is required to explain the increased reflection from the shock front.
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