Growth of 2D Plate-Like HMX Crystals on Hydrophilic Substrate

Two-dimensional (2D) plate-like HMX crystals have been grown first on hydrophilic substrate using an evaporation/solvent nonsolvent crystallization technique. As-grown crystals have been investigated by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectra, scanning electron microscopy (SEM), confocal laser scanning microscope (CLSM), and atomic force microscopy (AFM). The results unambiguously indicate that the plate-like crystals with large (011) faces are beta-HMX, and the fluctuations in the smooth area of (011) face are monomolecular or bimolecular HMX, which suggests the mechanism of monomolecular stacking pattern and layer-by-layer growth. Furthermore, the distinct recess consisting of hexagons parallel to each other is observed on the center of the (011) face. The special growth morphology, which is markedly different from that by the classical spiral growth, is attributed mainly to the negative concentration gradient in the constrained condition.