Papers by Author: Hong Hao Yan

Abstract: A detonation method for synthesizing carbon-encapsulated metal nanoparticles (CEMNPs) is reported. The composite precursors containing various nitrate dissolved in absolute ethanol is ignited by a nonelectric detonator in nitrogen gas in an explosion vessel. The material characteristics of these nanoparticles are then examined with the XRD,TEM,EDX and RS. The results show that the composite particles whose coating shell were graphite carbon could be dispersed finely. The core of nanoparticles were composed of iron, cobalt and nickel crystal to that of the above explosive precursors.

Abstract: In this paper, TiO2 nanopowders are produced by gas-phase detonation method. The powders are analyzed by X-ray diffraction (XRD), transmission electron microscopy (TEM) and specific surface area determination. The results indicate that the powders are mixed crystal of rutile and anatase, and have good dispersibility and high specific surface area. Also, the particle sizes of powders are between 40 to 200 nm which are spheroid and cube. The measurement data of detonation pressures shows that the reaction took place under a deflagration to detonation transition (DDT).

Abstract: Nanostructured spherical lithium manganese oxide (Li-Mn-O) with about 30nm in diameter was synthesized for the first time by explosive method. The water-solubility explosive was prepared using a simple facility at room temperature. The growth of lithium manganese oxides via detonation reaction was investigated with respect to the presence of an energetic precursor, such as the metallic nitrate and the degree of confinement of the explosive charge. The detonation products were characterized by scanning electron microscopy. Powder X-ray diffraction and transmission electron microscopy were used to characterize the products. Lithium manganese oxides with spherical morphology and more uniform secondary particles, with smaller primary particles of diameters from 10 to 50 nm and a variety of morphologies were found. Lithium manganese oxides with a fine spherical morphology different from that of the normal is formed after detonation wave treatment due to the very high quenching rate. It might also provide a cheap large-scale synthesis method. Explosive detonation is strongly nonequilibrium processes, generating a short duration of high pressure and high temperature. Free metal atoms are first released with the decomposition of explosives, and then theses metal and oxygen atoms are rearranged, coagulated and finally crystallized into lithium manganese oxides during the expansion of detonation process. For detonation of the water-solubility explosive, the detonation pressure, the detonation temperature and the adiabatic gamma were close to 3 GPa, 2300 K and 3. The inherent short duration, high heating rate (1010 – 1011 K/s) and high cooling rate (108 – 109 K/s) prevent the lithium manganese oxides crystallites from growing into larger sizes and induce considerable lattice distortion.