Mingli Qin

Combustion synthesis and excellent photocatalytic degradation properties of W18O49

In this paper, one-dimensional W18O49 nanopowders were fabricated by a one-step solution combustion method using glycine as the fuel and a metal acid radical ion as the metal source. The morphologies and non-stoichiometric single-crystal phase of W18O49 can be controlled by changing the amount of the fuel. The nanoneedles had a large amount of defects such as oxygen vacancies. This characteristic resulted in an excellent visible light-driven photocatalytic performance that took about 50 min to degrade methylene blue (100 mL; 40 mg L−1) under visible light. The interesting reaction mechanism of such needle-like W18O49 and the photocatalytic mechanism are studied in this paper.

Synthesis of Mesoporous Single Crystal Co(OH)2 Nanoplate and Its Topotactic Conversion to Dual-Pore Mesoporous Single Crystal Co3O4

A new class of mesoporous single crystalline (MSC) material, Co(OH)2 nanoplates, is synthesized by a soft template method, and it is topotactically converted to dual-pore MSC Co3O4. Most mesoporous materials derived from the soft template method are reported to be amorphous or polycrystallined; however, in our synthesis, Co(OH)2 seeds grow to form single crystals, with amphiphilic block copolymer F127 colloids as the pore producer. The single-crystalline nature of material can be kept during the conversion from Co(OH)2 to Co3O4, and special dual-pore MSC Co3O4 nanoplates can be obtained. As the anode of lithium-ion batteries, such dual-pore MSC Co3O4 nanoplates possess exceedingly high capacity as well as long cyclic performance (730 mAh g(-1) at 1 A g(-1) after the 350th cycle). The superior performance is because of the unique hierarchical mesoporous structure, which could significantly improve Li(+) diffusion kinetics, and the exposed highly active (111) crystal planes are in favor of the conversion reaction in the charge/discharge cycles.

Superior optical properties of Fe3+–W18O49 nanoparticles prepared by solution combustion synthesis

Modification by metal-doping allows the design of new nanomaterials with enhanced optical properties. In this paper, the photocatalytic effects of Fe3+-doped W18O49 nanorods prepared by solution combustion synthesis were studied for the first time. The Fe3+-doped W18O49 powders were investigated by X-ray diffraction, high-resolution transmission electron microscopy, selected area electron diffraction, and X-ray photoelectron spectroscopy. The powders were well-crystalline with diameters ranging from 50 nm to 250 nm and the length decreasing from more than 10 μm to 4 μm on average. The photoluminescence (referred to as PL here after) spectrum showed that the emission intensity increased with increasing Fe3+ doping, suggesting that more defects were generated. Moreover, this novel composite catalyst displayed excellent photocatalytic efficiency towards the degradation of organic compounds in aqueous media under UV-visible light irradiation. In particular, 0.5 wt% Fe3+-doped W18O49 had the best photocatalytic efficiency. This improvement was mainly attributed to the synergistic effect between Fe3+ and W18O49 nanopowders and the defects in the nanostructure caused by doping.

Microstructural Characterization of Co-Based ODS Alloys

Co-based ODS alloys, strengthened by nanosized oxide dispersion and γ′ precipitates, are potential high-temperature structural materials. The characteristics of the mechanically alloyed powder and the microstructural evolution of the Co-based ODS alloys were investigated. The results revealed that mechanical alloying had induced the formation of supersaturated solid solution in immiscible Co-Al-W-based alloys, originating mainly from extensive grain boundary region, high dislocation density, and ample point defect. Chemical compositions of mechanically alloyed Co-Al-W-based ODS alloys easily deviate from the γ/γ′ two-phase region, leading to the existence of AlxCo, Co3W, Co7W6, and W phases in addition to the γ and γ′ phases. Nonuniform distribution of alloying elements brings about the differences in morphologies and sizes of γ′ precipitates. Microstructural formation process is impelled by spinodal decomposition mode, and spinodal decomposition behavior has been accelerated in the fine-grained alloy because of the presence of short-circuited diffusion paths for atomic movement.

Solution combustion synthesis of nanosized WOx: characterization, mechanism and excellent photocatalytic properties

Various nanoscale tungsten oxides with excellent photocatalytic properties were synthesized via an ultra-rapid solution combustion synthesis method. The results indicated that the WO3 and W18O49 could be synthesized with different fuels (glycine, urea, urea and citric acid) and the powders presented mesoporous structures with different morphologies such as nanoparticles, nanorods and nanoneedles. Detailed reaction mechanisms of various systems were identified, and the specific roles of different fuels were discussed. Moreover, the synthesized powders displayed excellent photocatalytic efficiency, degrading organic compounds in 50 min under UV-visible light irradiation. The work suggests that solution combustion synthesis can be used as a new strategy to design nanosized stoichiometric and oxygen-vacancy-rich nonstoichiometric oxides with excellent properties.

Wettability and pressureless infiltration mechanism in SiC-Cu systems

Abstract The wetting behavior of copper alloys on SiC substrates was studied by a sessile drop technique. The microstructure of SiCp/Cu composites and the pressureless infiltration mechanism were analyzed. The results indicate that Ti and Cr are effective elements to improve the wettability, while Ni, Fe, and Al have minor influence on the improvement of wettability. Non-wetting to wetting transition occurs at 1210 and 1190°C for Cu-3Al-3Ni-9Si and Cu-3Si-2Al-1Ti, respectively. All the copper alloys react with SiC at the interface forming a reaction layer except for Cu-3Al-3Ni-9Si. High Si content favors the suppression of interfacial reaction. The infiltration mechanism during pressureless infiltration is attributed to the decomposition of SiC. The beneficial effect of Fe, Ni, and Al is to favor the dissolution of SiC. The real active element during pressureless infiltration is Si.

The formation of CuO porous mesocrystal ellipsoids via tuning the oriented attachment mechanism

We report a new chemical reaction route to synthesizing CuO porous mesocrystal ellipsoids via decomposition of copper vanadium oxide under hydrothermal conditions. By finely tuning the oriented attachment growth mechanism of CuO, a porous mesocrystal structure was synthesized. Structural and morphological evolutions of the CuO product were investigated and the formation of CuO porous mesocrystal ellipsoids here was essentially determined by the amount of ammonium metavanadate. An oriented nanoparticle aggregation with tailoring of the structure, including compact mesocrystals and porous mesocrystals, could be achieved in different concentrations of reactants. The strategy of constructing the structure via an oriented attachment growth mechanism could be applied to the synthesis of other nanomaterials with complex structures.

Solution combustion synthesis of Ni–Y2O3 nanocomposite powder

Abstract Ni–Y 2 O 3 nanocomposite powder with uniform distribution of fine oxide particles in the metal matrix was successfully fabricated via solution combustion process followed by hydrogen reduction. The combustion behavior was investigated by DTA-TG analysis. The influence of urea to nickel nitrate (U/Ni) ratio on the combustion behavior and morphology evolution of the combusted powder was investigated. The morphological characteristics and phase transformation of the combusted powder and the reduced powder were characterized by FESEM, TEM and XRD. The HRTEM image of Ni–Y 2 O 3 nanocomposite powder indicated that Y 2 O 3 particles with average particle size of about 10 nm dispersed uniformly in the nickel matrix.

Facile route for synthesis of mesoporous graphite encapsulated iron carbide/iron nanosheet composites and their electrocatalytic activity

Mesoporous graphite encapsulated Fe3C/Fe nanosheet composites have been synthesized by a facile template free method using ferric nitrate, glycine and glucose as raw materials. X-ray diffraction, transmission electron microscopy, high-resolution transmission electron microscopy and Raman spectrometer have been used to characterize the composites. The formation process and morphology of the products have been discussed in detail. Interestingly, this facile route can synthesize graphite encapsulated Fe3C, Fe3C/Fe and Fe composites with two dimensional nanosheet structure by tuning the reaction temperature and the Fe3C and Fe nanoparticles with size less than 30nm are well dispersed on the carbon sheet. The mesoporous graphite encapsulated Fe3C/Fe nanosheet composites with a high specific surface area have application in non-noble metal electrocatalysis for hydrogen evolution reaction.

Facile solution combustion synthesis of MoO2 nanoparticles as efficient photocatalysts

Foam-like MoO2 assembled from nanoparticles was fabricated by a solution combustion synthesis method using hexaammonium molybdate, ammonium nitrate (NH4NO3) and glycine as the precursors. The effect of the glycine/NH4NO3 ratio (Φ = 0.25, 0.50, 0.75, 1.0 and 1.25) on the physicochemical properties of the final products was systematically studied. The Φ value was found to display significant roles in the final phases and morphologies of the products. With a Φ value of 0.50, the foam-like product consisting of MoO2 nanoparticles with an average size of about 20–30 nm was synthesized. The photocatalytic activities of the foam-like MoO2 towards degradation of several contaminants, including methyl orange (MO), methylene blue (MB), rhodamine B (Rh B) and phenol, were investigated. The foam-like MoO2 offered excellent capability and stability toward photocatalytic degradation of the studied contaminants. The results reported here demonstrated that rational design of MoO2-based photocatalysts might be able to improve their properties in energy conversion and environmental preservation.