Fracture Surface Topography of TNT Using Atomic Force Microscopy
Height profiles spaced 0.008 μm apart across the fracture surface of TNT were obtained with an atomic force microscope (AFM). Spatial power spectra (wavelengths of 0.016 μm to 4.2 μm) were calculated using a prolate spheroidal data window in the horizontal space domain prior to using a fast Fourier transform algorithm.1 Preliminary findings based on the first 13 profiles across the surface are as follows. The power spectral density of the individual fracture surface profiles is found to decrease with increasing spatial frequency over the region examined, ≈ 1.0 μm−1 to ≈ 10.0 μm−1. Power spectral slopes ≤ −3 indicate deterministic fracture. Harmonic distribution of peaks in the power spectra defines the cluster size across the full scan. The variation of the power amplitudes at given frequencies across the profile set defines the cluster size across the 13 profiles. A typical TNT cluster size is found to be approximately 106 TNT molecules.
KeywordsAtomic Force Microscope Fracture Surface Spatial Frequency Power Spectral Density 4New York City
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