Theoretical Study of Screening Dependence of Aluminium Doped MgB_2

The screening dependence of superconducting state parameters （λ, μ＊, Tc, α and NoV） of six alloys of aluminium doped MgB2 systems are studied in the BCS-Eliashberg-MeMillan framework by employing five forms of dielectric screening function, viz. random phase approximation （RPA）, Harrison, Geldart and Vosko （GV）, Hubbard and Overhauser in conjunction with Ashcroft＇s potential. It is observed that electron-phonon coupling strength and Coulomb pseudopotential μ＊ are quite sensitive to the form of dielectric screening, whereas transition temperature Tc, isotope effect exponent α and effective interaction strength NoV show weak dependence on the form of dielectric screening function. It is found that the RPA form of dielectric screening function yields the best results for transition temperature Tc for all alloys of the Mg-Al-B system. The results obtained using GV screening are much higher than the experimental results. This shows that all the four dielectric screenings used here almost describe superconductivity in all the alloys of the Mg-Al-B system, but the GV screening is not suitable for such an alloy system.

Al_(x)/HKUST-1 prepared by synthetic exchange as catalyst for reduction of NO by CO at low temperature

Al_(x)/HKUST-1(x=1/24,1/12,1/6,1/3),one of the bimetallic copper-based organic framework materials,was successfully prepared by the synthetic exchange method and characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),specific surface area(BET),thermogravimetric analysis(TG),infrared spectra(IR),X-ray photoelectron spectroscopy(XPS),and H_(2)-temperature programmed reduction(H_(2)-TPR).The findings indicated that Al_(x)/HKUST-1 maintained the octahedral morphology of its precursor(HKUST-1).The thermal stability and catalytic reduction ability of HKUST-1 skeleton were improved by doping aluminum(Al^(3+)).Al_(1/12)/HKUST-1 showed the best performance among all samples,with a nitric oxide(NO)conversion rate of 100%at 210℃(50℃lower than that of HKUST-1).The valence kind of Al,Cu,and O in Al_(1/12)/HKUST-1 did not change after the catalytic reaction,but the contents of Al,Cu,and O in different forms changed significantly.The catalytic process of the Al_(x)/HKUST-1 followed a Langmuir-Hinshelwood mechanism.

Role of Al(III) in Zn-Based Electrode Synthesis for Supercapacitor

Supercapacitor is considered as one of the most promising energy storage systems because of its high power density, long life and low production cost. Electrode materials play important roles in the performance of Supercapacitor (SC). In this study, Zn-based hydrotalcite structure materials are prepared by hydrothermal method. The influence of Zn/Al ratio in precursors on electrochemical properties of electrode materials is investigated. The results show that Al(III) promotes the formation of relatively ordered active substances and participates in redox reaction on electrode surface. Specific capacitance of Zn-based electrode reaches 2557 F·g-1 (1.0 A·g-1) at Zn/Al molar ratio of 1:1 in precursors. This method is simple and environmentally friendly. The electrode exhibits excellent electrochemical activity and stability, showing this material application prospect for supercapacitor.