Papers by Author: Wen Liu

Abstract: Fe-SBA-15 materials with different Fe content have been prepared using tetraethyl orthosilicate (TEOS) and iron nitrate (Fe (NO₃)_3·H₂O as precursors and Pluronic P123 as structure directing agent through evaporation-induced self-assembly (EISA) method. The materials were characterized by nitrogen sorption, powder X-ray diffraction and TEM. All the Fe-SBA-15 samples appeared ordered 2D hexagonal mesostructure. The BET surface area and pore diameter were about 500 m²/g and 4 nm respectively. In the reaction of phenol hydroxylation to dihydroxybenzenes, the Fe-SBA-15 materials showed good catalytic activity, giving 20.2% of phenol conversion, 58.2% of selectivity for o-dihydroxy benzene and 41.8% of selectivity for p-dihydroxy benzene. After five cycles, the product yield was 25.2%, while selectivities of o-dihydroxy benzene and p-dihydroxy benzene were 58.2% and 41.8%, respectively. All these findings indicated the potential of Fe-SBA-15-10 could be used as a cost-effective, environment-friendly catalyst.

Abstract: In this paper, Mechanical alloying (MA) and field activated and pressure assisted synthesis (FAPAS) were used for preparing the ultra-hard, super-abrasive AlMgB₁₄-xTiB₂ composite ceramic. The samples were fabricated at 1500 under a pressure of 60 MPa. The microstructures and compositions of samples were observed and determined by scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), X-ray diffraction (XRD). It was indicated that addition of TiB₂ was effective for increasing both quantities. A maximum Vichers hardness of 38.5GPa and a fracture toughness of 3.85MPam^½ of AlMgB₁₄ reinforced with 70 wt.% of TiB₂ were achieved. Abrasion wear tests showed that adding TiB₂ would improve the wearability obviously.

Abstract: Mechanical alloying(MA) and field activated and pressure assisted synthesis(FAPAS) combining the method of in-situ synthesis were used for the preparing ultra-hard, super-abrasive AlMgB₁₄ metallic ceramic. AlMgB₁₄ was performed at 1500°C under a pressure of 60 MPa from the elemental constituents (aluminium, magnesium and boron (vacuum annealed 1500°C)). The sample was examined by SEM, EDS and XRD. The products contained uniform AlMgB₁₄. The hardness of AlMgB₁₄ prepared under these conditions is 27.2-32.5GPa, the average density is 2.62g/cm³ and the fracture toughness is 3MPam1/2.These values are in correspond to the hardness of AlMgB₁₄ prepared by mechanical alloying/hot uniaxial pressing (28-35GPa). Analysis of the mechanisms of fracture,the fracture surface of AlMgB₁₄ sintered at 1500°C is of transgranularfracture. A new approach is brought forward by the mechanical alloying assisted FAPAS process (MA-FAPAS) to have synthesized AlMgB14 with fast heating-up, efficiency, energy saving and high yield.

Abstract: Hard and superlight thin films laminated with boron carbide have been proposed as candidates for strategic use such as armor materials in military and space applications. We prepared Al-Mg-B films by sputter deposition on Si (100) substrates with one AlMgB14 target. The films were characterized by X-ray diffraction, atomic force microscope, GD-OES spectroscopy. The results show that films of AlMgB with different compositions have been deposited by changing the target power and deposition temperature.The influences of substrate temperature and sputtering power on the quality of the films are discussed.

Abstract: The growth mechanism of Onion-like fullerenes (OLFs) synthesized by arc discharge in liquid benzene was discussed. HRTEM was employed to characterize the morphologies and microstructures of the products. Results showed that the typical OLFs were highly crystallized with uniform diameter of 10-30nm. The growth of OLFs depended on the appropriate temperature gradient and quenching zone provided by the bubbles. The aromatic debris could act as graphite fragments composed of hexagonal carbon rings. The reducing of dangling bonds on the edges of graphite fragments would lower the energy of the system, resulting in formation of a close-caged structure at suitable temperature gradient by the auto-curling of graphite fragments. Based on the impact of the innermost core shape, such as C60 shape, quasi-spherical or polyhedral hollow concentric OLFs was formed. Adding ferrocene, ferrocene directly influenced the morphology and yield of OLFs.

Abstract: Silicon was electrodeposited by electrochemical reduction of silicon tetrachloride in propylene carbonate solvent on an alloy of nickel-titanium-niobium and nickel, which were used as working electrodes respectively. The effect of two substrates as working electrodes on the electrodeposition ability of the silicon was investigated by scanning electron microscopy (SEM) and energy dispersion spectroscopy (EDS). Results show that using an alloy of titanium, nickel and niobium as working electrode is better than nickel in the morphology and deposition yield of silicon.

Abstract: In this paper it was investigated that silicon be electrodeposited in the room temperature from propylene carbonate solvent. Cyclic voltammograms indicated that it was possible to electrochemical reduction of silicon chloride at -2.3984V versuHg/Hg2Cl2/ KCl (saturation) quasi-reference electrode. Potentiostatic electrolysis yielded deposits, accompanied by the change in electrolyte color from transparent to brown. Scanning electron microscopy (SEM) and energy dispersion spectroscopy (EDS) were used to characterize the physical properties of the silicon. The EDS analysis performed simultaneously with SEM observation demonstrates that the deposit consists of Si, O and Cl.