Huaming Yang

Mechanochemical synthesis of cobalt oxide nanoparticles

Abstract Cobalt oxide (Co 3 O 4 ) nanoparticle was synthesized by thermal treatment of the precursor obtained via mechanochemical reaction of Co(NO 3 ) 2 ·6H 2 O with NH 4 HCO 3 . Calcination of the precursor at 300 °C resulted in the formation of Co 3 O 4 nanoparticles of 13 nm in crystal size. The precursor was examined by simultaneous differential thermal analysis (DTA) and thermogravimetric analysis (TGA). The Co 3 O 4 nanoparticles were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Effect of calcination temperature on Co 3 O 4 crystal size was discussed. The activation energy ( E ) of Co 3 O 4 nanoparticle formation during thermal treatment was calculated to be 15.9 kJ/mol.

Synthesis of tin oxide nanoparticles by mechanochemical reaction

Abstract The synthesis of tin oxide (SnO 2 ) nanoparticles by mechanochemical reaction (SnCl 2 +Na 2 CO 3 ) with NaCl as diluent and subsequent thermal treatment was investigated using differential thermal analysis (DTA), thermogravimetric analysis (TGA), X-ray diffraction (XRD), infrared spectroscopy (IR) and transmission electron microscopy (TEM). Heat treatment of the as-milled powder at 600xa0°C in air and removal of NaCl through washing produced the SnO 2 nanocrystallites with an average crystal size of about 28 nm, varying with the thermal treatment temperature. The mechanism of nanocrystallites growth is discussed.

Mechanosynthesis and gas-sensing properties of In2O3/SnO2 nanocomposites

We report the successful synthesis of 30 wt% In2O3/SnO2 nanocomposites by heating the precursor obtained via a mechanochemical reaction, and investigate their gas-sensing properties. The samples were characterized by means of x-ray diffraction, scanning electron microscopy and x-ray photoelectron spectroscopy. Subsequent thermal treatment of the precursor for 2 h in air at 700 °C resulted in the formation of In2O3/SnO2 nanocomposites with an average crystal size of about 22 nm. In comparison to pure SnO2, the gas sensor fabricated from the as-synthesized In2O3/SnO2 nanocomposites has an excellent gas-sensing performance, such as high sensitivity (93 for 1000 ppm C2H5OH), a rapid response rate (within 5 s for 90% response and recovery times) and high selectivity to ethanol. To explain the enhanced sensitivity of the In2O3/SnO2 gas sensor, the gas-sensing mechanism is discussed.

Preparation of antimony-doped SnO2 nanocrystallites

Abstract The antimony-doped SnO 2 nanocrystallite was synthesised by the co-precipitation reaction and subsequent calcination from the antimony(III) chloride and tin(IV) chloride. The crystal size, pore size distribution and properties of the nanocrystalline powders were examined by differential thermal analysis, thermogravimetric analysis, X-ray diffraction and desorption isotherm(Barrett–Joyner–Halenda method). Calcination of the precipitate powder at 650°C led to the formation of Sb–SnO 2 nanocrystallite of ∼6xa0nm in crystal size. Most of the pores in the nanocrystallite are about 5–10xa0nm in diameter. Effect of doped antimony on the crystal size of the nanocrystallite is discussed.

MECHANOCHEMICAL SYNTHESIS OF CADMIUM-DOPED TIN OXIDE NANOPARTICLES

The cadmium-doped SnO2 nanoparticles have been successfully prepared by a simple mechanochemical reaction and subsequent thermal treatment. The samples were characterized using X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). Thermal treatment of the as-milled powder at 700°C for 2 h resulted in the formation of Cd-SnO2 nanoparticles with an average crystal size of 13 nm, varying with the calcination temperature. The effect of doped cadmium on the crystal size of the nanoparticles was investigated. The lattice parameter (c) of the Cd-SnO2 nanoparticles, lower than that of pure SnO2, decreased with increasing amount of doped cadmium. The apparent activation energy of Cd-SnO2 nanocrystal growth during calcination of the precursor was calculated to be 70.8 kJ/mol. The mechanochemical method is a novel, cheap and convenient technique especially suitable for large-scale synthesis of nanosized materials.

SYNTHESIS OF NANOCRYSTALLINE ANATASE TiO2 BY SOL–GEL METHOD

Synthesis of uniform nanocrystalline anatase TiO2 by sol–gel method was investigated using different thermal analysis (DTA), thermogravimetric analysis (TGA), X-ray diffraction (XRD) and scanning electron microscope (SEM) techniques. Thermal treatment of the precursor at 350°C for 2 h in air results in the formation of nanocrystalline anatase TiO2 with the average crystal size of 21.5 nm. Quantitative analysis through energy dispersive X-ray spectroscopy (EDS) indicated that the atomic ratio of Ti:O ≈ 1:1 is close to the stoichiometric ratio of TiO2, leading to the evident fact that the prepared nanoparticles are indeed the TiO2 material.