Advanced Materials Research Vols. 239-242

Abstract: Nanostructured α-Ni(OH)₂/ mesoporous carbon composites were synthesized by a facile solvothermal method using sodium dodecyle sulfate as a soft template and urea as a hydrolysis-controlling agent. The obtained products were characterized by X-ray diffraction(XRD), and scanning electron microscopy(SEM). Electrochemical properties studies were carried out using cyclic voltammetry(CV) and galvanostaitc charge/discharge method. The results exhibited that the α-Ni(OH)₂/ mesoporous carbon composites single electrode had high specific capacitance in KOH electrolyte. The maximum specific capacitance of the α-Ni(OH)₂/ mesoporous carbon composites single electrode was up to 2191 F/g in 6 M KOH solution at a charge-discharge current density of 4 mA/cm², when the mass percent of mesoporous carbon was 5%. It is suggested its potential application in the electrode material for supercapacitors.

Abstract: The electronic properties of N-doped orthorhombic SrHfO₃ have been calculated using the plane-wave ultrasoft pseudopotential technique based on the first-principles density-functional theory with the local density approximation. From the calculated band structure and density of states, the bandgap reduction is observed due to the presence of the N-2p states in the top of valence bands, which leads to red-shift. Moreover, in order to clarify the charge transfer and bonding properties of N-doped orthorhombic SrHfO₃, we have calculated and analysed the charge density.

Abstract: Nanocrystalline Ni-W-Fe-La alloys coatings were prepared by pulse electrodeposition. X-ray diffraction (XRD), scan electron microscopy (SEM) and energy dispersive spectrometer (EDS) were used to characterize the products, which average particle size of 17 nm and have special properties such as array densification, uniformity and crack-free surface. The linear sweep voltammetry (LSV) and neutral salt spray test demonstrated the coatings have good catalytic activity for hydrogen evolution and corrosion resistance.

Abstract: Spheroidal graphite was obtained by direct quenching iron melt atfter spheroidization and inoculation procedures. The morphology and the effects of trace elements on the formation of spheroidal graphite were investigated by scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX) spectroscopy. Results indicate that all the graphite fixed by quenching, is nearly spheroidal with a diameter of approximately 20μm. In addition, the SEM image of graphite morphology confirms the screwed growth model of spheroidal graphite. The linear distribution of trace elements shows that the nucleus of spheroidal graphite consists of antimony, cerium, magnesium and sulfur element. Meanwhile, trace elements, such as antimony, cerium and magnesium, enrich around graphite nodule, which facilitates the formation of spheroidal graphite.

Abstract: Al₂O₃-Ti(C,N)composite ceramics were prepared by in situ aluminothermic reduction and pressureless sintering. The effects of different Ti(C,N) contents and sintering temperatures on microstructure and mechanical properties (bulk density ,apparent porosity and blending strength)of samples were investigated through experiments.The results show that Al₂O₃-Ti(C,N) composite ceramics with 10 wt.% Ti(C,N) prepared using titanium dioxide and metal aluminum powder as raw materials and sintered at 1300 °C for 3h under a flowing nitrigen stream have good properties ,with bulk density 2.94g/cm³,apparent porosity 26.4%, and blending strength reaches to 28.04 MPa. According to the microstructure analysis,the fine in situ synthesis Ti(C,N) particles are uniformly dispersed in tabular alundum matrix. Ti(C,N) and tabular alundum phases are closely combined and can inhibit grain growth each other,which is benefical in improving the comprehensive properties of composite ceramics.

Abstract: Semisolid alloy slurry was prepared by an efficient and energy-saving technology which consists of low superheat pouring and slightly electromagnetic stirring (LSPSES). The effects of the main preparing parameters on the slurry were researched. The results indicate that the slurry to satisfy rhoe-forming needed can be prepared by LSPSES. The pouring temperature and the stirring power remarkablely affect the morphology and size of primary α-Al in semisolid Al alloy slurry. Through the suitable slightly electromagnetic stirring, the pouring temperature can be suitably raised to reach the efficient and energy-saving effectiveness.

Abstract: The variations of hardness and electrical conductivity of a deformed supersaturated Cu-Cr alloy have been investigated during isothermal aging. The influence of trace rare earth elements (La, Y or Nd) as a second alloying element was also studied. The results showed that the heavily deformed alloys exhibited an instant increase in both hardness and electrical conductivity due to an accelerated precipitation after a short aging treatment. Compared with the solution treated Cu-0.8wt %Cr-0.05wt. %La and Cu-0.8wt %Cr-0.05wt. %Y alloy, the as-cast Cu-0.8 wt. %Cr-0.05 wt. %Nd exhibited a retarded recrystallization which should be attributed to the pinning effect of primary Cr precipitates lying in the grain boundaries. Rare earth elements can act as a useful second alloying element to inhibit recrystallization of the deformed alloys due to the occurrence of some copper-rare earth intermetallic compounds and rare earth oxides.

Abstract: Based on the impedance matching and electromagnetic resonant characteristic of composite materials, we present a single-layer metamaterial absorber consisting of arch copper loop and substrate FR-4, of which the resonant frequency depended on the loop’s geometry perimeter. By combining resonant loops with different dimensions together, we can achieve multi-band absorption. The standard finite difference time domain method was used to calculate the magnitudes of reflectance, and then the induced surface current and power loss distributions were demonstrated to analyze the insight physical picture of the multi-band resonant feature. By optimizing the simulation results, the absorptivities of two absorption peaks are all above 98% when the number of copper loops is two, 95% for three absorption peaks of three loops, and 87% for four absorption peaks of four loops.

Abstract: Multi-ion beam (MIB) surface modification techniques are used to treat Cr12MoV cold die work steel. The modified layers of steel treated by MIB is improved with low friction coefficient, high wearing resistance and strong adhesion with the matrix through results of hardness, scratch and wearing test. The modified layers include (Ti₂N +TiN), (а-Fe+TiN) and (а- Fe(N)+Cr₇C₃) three layers from surface to inside by analysis of SEM, EPMA and TEM. And the surface layer presents nano-size grain refining. The service life of the Cr12MoV cold die steel treated by MIB can be prolonged 3-5 times longer than the untreated one.

Abstract: A novel type of liquid crystalline polyimide with good electroactive properties has been successfully synthesized through polycondensation in the component solvent of benzene sulfonyl chloride, dimethyl formamide and pyridine by N,N’-hexane-1,6-diylbis(trimellitimides), p-hydroxybenzoic acid, 4,4'-dihydroxybenzophenone and double amino-capped aniline trimer (N¹,N^1'-(1,4-phenylene)bis(benzene-1,4-diamine)). The structure of the obtained polymer was characterized and verified. The polymer can be dissolved in the component solvent of phenol and chloroform or DMF, NMP alone, et al. The molecular weight (Mn=1.7×10⁴, Mw=8.2×10⁴，PDI=4.8) was determined by gel permeantion chromatography using DMF as eluent. By combining the excellent properties of both polyimide and oligoaniline, such material could be used in more broad fields. Furthermore, due to the orientation properties of liquid crystalline property, the conductivity of this polymer is anisotropic, with 10^-6 S/cm along the shear direction vs. 10^-7 S/cm perpendicular to the shear direction.