Quick Precipitation Method Research Articles

Preparation, Characterization and Catalytic Activity of Transition Metal Oxide Nanocrystals

Nanocrystals of four transition metal oxides (TMOs) were prepared by a novel quick precipitation method and characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). From the XRD patterns, average particle sizes for CuO, NiO, Co 2 O 3 , MnO 2 are calculated to be 15 nm, 4 nm, 13 nm, 40 nm, respectively. The TEM study revealed that the majority of CuO particles are of 6–8 nm in size. Catalytic activities of the TMO nanocrystals for thermal decomposition of ammonium perchlorate (AP) were investigated using differential thermal analysis (DTA), thermogravimetric analysis (TGA) and ignition delay measurements. The order of catalytic activity of these oxide nanocrystals on thermal decomposition of AP was found to be: Co 2 O 3 > CuO > NiO > MnO 2 .

Preparation Parameters Optimization of Noncrystalline MoS<sub>3</sub> - the Precursor of Nano-MoS<sub>2</sub>

Noncrystalline molybdenum trisulfide is an important precursor for preparation of nano-MoS 2 by sodium molybdate using thioacetamide or sodium sulfide as a sulfur source under an acid condition via quick homogeneous precipitation method in our previous study. The morphology, size and shape of MoS 3 noncrystalline particles affect the properties of MoS 2 nano-particles directly. In this paper, the optimization of some preparing parameters of MoS 3 noncrystalline particles, such as temperature, pH, concentration and proportion of the reactant was investigated. The relationships among these influence factors and Na 2 Mo0 4 conversion rate have been worked out. The X-ray diffraction characterization further confirm that the as-prepared MoS 3 particles under the optimized process parameters are of typical noncrystalline characteristics, and the transmission electron microscope observations show that the size of the particles are about 500-1000 nm. In addition, MoS 2 nanoparticles can be fabricated from the MoS 3 as prepared under the optimized process conditions. The XRD and TEM results show that the obtained MoS 2 particles are of 2H-MoS 2 structure with a size of about 30 nm.

Preparation and characterisation of ball-like MoS2 nanoparticles

Molybdenum sulphide (MoSx) particles were prepared from Na2MoO4 and CH3CSNH2 by the quick homogenous precipitation method within 5 min in alcohol–water solution at 82°C and normal pressure. The prepared MoSx particles were studied by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM). The results showed that the as prepared product was ball-like amorphous MoSx (x=3·20) nanoparticles. The resultant amorphous ball-like MoSx nanoparticles were then calcined under hydrogen flow at a selected temperature for 50 min. The results of XRD, TEM and HRTEM confirmed that the ball-like MoS2 nanoparticles with fullerene structure were prepared by calcining the amorphous MoSx nanoparticles at 780°C. The resultant ball-like nano-MoS2 particles were transformed into polyhedron like nano-MoS2 particles as the calcining temperature was increased to 960°C.

Synthesis of nanometric molybdenum disulphide particles and evaluation of friction and wear properties

Nanometric molybdenum disulphide particles of about 30 nm diameter have been prepared by the hydrodesulphurisation of molybdenum trisulphide obtained from acidifying a mixed solution of Na2MoO4 and Na2S at ambient temperature using a quick homogeneous precipitation method (QHPM). Using X-ray diffraction and transmission electron microscopy (TEM), the size and crystallisation of the nano-MoS2 obtained by hydrodesulphurisation at different temperatures have been investigated. In addition, the tribological performance of nano-MoS2 has been investigated by means of a block-on-ring tribometer, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The results show that base oils with nanometric MoS2 as an additive provide higher wear resistance than other oils containing commercially available common MoS2. However, the friction reduction is not obviously improved. SEM characterisation reveals a worn, smooth surface when using the nano-MoS2 additive, and XPS analysis indicates a greater amount of molybdenum oxide and iron sulphide in the antiwear thin film formed on the rubbed surface.

Highly dispersed CuO nanoparticles prepared by a novel quick-precipitation method

Highly dispersed copper oxide (CuO) nanoparticles with an average size of 6 nm have been successfully prepared by a novel quick-precipitation method. The as-prepared CuO nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV–Visible absorption spectroscopy and BET nitrogen adsorption. The results show that the as-prepared CuO nanoparticles have high dispersion and narrow size distribution. The influence of reaction conditions on morphology of CuO nanocrystals was discussed. Spherical, ellipsoidal and needle-shaped CuO nanocrystals can be obtained simply by varying the reaction temperature and controlling the addition of NaOH.