This paper reports the preparation and characterization of a new type of composite particles with a core/shell structure. A tetrahydrofuran suspension containing 3-nitro-1,2,4-triazol-5-one(NTO) and Octahydro-1,3,5,7-tetranitro -1,3,5,7-tetrazocine (HMX) was injected into a spray dryer. After solvent evaporation, the NTO crystallized in the shape of small particles on the surface of the ultrafine HMX particles. Through this process the core/shell structure of HMX/NTO composite particles was obtained. Scanning Electron Microscopy (SEM) images (20 kV) of these composite particles revealed that extensive flaws existed in the external shell layer. Atomic Force Microscopy (AFM) revealed that the surface of the composite particles were "potholed" while those of the HMX particles were smooth. The nitrogen 1s spectrum of X-ray Photoelectron Spectroscopy (XPS) indicated that, on the surface of composite particles, the content of NTO was much higher than that of HMX. Thermogravimetry and Differential Scanning Calorimetric (TG-DSC) curves revealed that thermolysis of NTO in the core/shell composite particles occurred with a slight shift toward the lower temperature region compared with that of HMX/NTO physical mixture at the same ratio. Friction and impact sensitivity of the HMX/NTO core/shell composite explosive were significantly reduced in comparison with that of the physical mixture with an equivalent composition.
Core/shell composite particles, HMX, NTO, Preparation