Papers by Keyword: Electrochemical Property

Abstract: Flower-like TiO₂ hierarchical structures were synthesized by a solvothermal strategy using tetrabutyl titanate as the titanium source. The obtained flower-like TiO₂ hierarchical structures were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), specific surface area analysis, Raman spectroscopy and energy-dispersive spectroscopy (EDS). Results show that the flower-like hierarchical structures are composed of anatase titanium dioxide. TiO₂ nanowires are first formed by the self-assembly of nanocrystals with a diameter of 20 nm, and then several TiO₂ nanowires produce a petal-like structure. Finally, flower-like TiO₂ hierarchical structures with a diameter of 2 ~ 2.3 μm are assembled by these petal-like structures. The electrochemical properties of the flower-like TiO₂ hierarchical structures were studied by using these hierarchical structures as the anode material in a lithium-ion battery. The flower-like TiO₂ hierarchical structures have an initial discharge capacity of 473.9 mAh/g at a current density of 100 mA/g and an initial discharge capacity of 244.4 mAh/g at a current density of 2 A/g in the potential range of 0.01~3 V. The photocatalytic properties of the flower-like TiO₂ hierarchical structures were studied by degrading methyl orange (MO) solution under ultraviolet (UV) light irradiation. When used as a photocatalyst, the degradation rate of MO is 95.8% after 40 min of UV irradiation, showing that the flower-like TiO₂ hierarchical structures have excellent photocatalytic activity.

Abstract: La_0.70Mg_0.30Ni_2.45Co_0.75Al_0.30 alloys were synthesized by milling and blending of the La_0.70Ni_2.45Co_0.75Al_0.30 pre-alloy prepared by melting and elemental Mg, followed by annealing. The effects of milling time on the microstructures and electrochemical properties of the La_0.70Mg_0.30Ni_2.45Co_0.75Al_0.30 hydrogen storage alloys were investigated. The structure, microstructure and electrochemical properties of the alloys were investigated by XRD, SEM and electrochemical measurements. The results showed that a noticeable (La,Mg)₂Ni₇ phase can be observed in the alloy milled for 2 h. Moreover, the distribution of the Mg element in the alloy milled for 15 h presents some aggregation phenomena. The La_0.70Mg_0.30Ni_2.45Co_0.75Al_0.30 alloy milled for 2 h exhibits the best maximum discharge capacity (313.5 mAh/g) and discharge potential characteristic. The cyclic stability of the as-cast La_0.70Ni_2.45Co_0.75Al_0.30 alloy is better than that of the milled La_0.70Mg_0.30Ni_2.45Co_0.75Al_0.30 alloy.

Abstract: Aiming at the special service environment of aluminum alloy drill pipe, in this paper, the influence of extrusion texture on the mechanical and electrochemical properties of aluminum alloy drill pipe was studied. And the macroscopic textures of longitudinal profile and cross section of aluminum alloy drill pipe were tested, and the tensile, compressive and impact mechanical properties were tested, followed by immersion and electrochemical testing. The results show that the texture which 2A12T4 aluminum alloy drill pipe contains is <001> and <111> along the extrusion direction and <223>, <101> in the transverse direction. The test results of mechanical properties show that the extruded texture will affects the mechanical properties of material. When the cross section and longitudinal profile samples of 2A12T4 were soaked in 3.5% NaCl solution at 25°C, 60°C and 90°C, their corrosion resistance are different. The pits of transverse specimens exhibit a dispersed distribution and that of longitudinal specimens are distributed along the extrusion direction.

Abstract: The alloy with the composition of Mg₂Ni prepared by low-temperature solid-phase sintering was mechanically milled for 10, 25, 40 and 50 h. The microstructures and electrochemical properties of the Mg₂Ni alloys were investigated by X-ray diffraction (XRD), optical microscope (OM) and electrochemical measurements. Furthermore, two broadening effects of XRD peaks caused by crystallite size and lattice strain were separated by the approximate function method and least square method. Crystallite size and lattice strain of the alloy were calculated. The results showed that sintered and milled alloys consist of the Mg₂Ni phase. The milled alloys transform partly into nanocrystalline/amorphous structures during the milling process. By calculation, the crystallite size decreases and the lattice strain in the alloy decreases first and then increases with increasing milling time. The discharge capacities of the sintered alloy are significantly improved by milling. The maximum discharge capacities of the milled alloys increase with the increasing milling time.

Abstract: The nickel and manganese oxides (Ni-Mn oxides) were prepared by a simple co-precipitation process with sodium carbonate (Na₂CO₃) as precipitant. The products are the mixture of nickel oxides, manganese oxides and their solid solution. The phase and morphology of the synthesized product were characterized by X-ray diffraction and field emission scanning electron microscope. The electrochemical capacitive characterization was performed using cyclic voltammetry (CV), galvanostatic charge/discharge (GCD) and electrical impedance spectroscopy (EIS) measurements in a 6mol/L KOH aqueous solution electrolyte. The result shows that a maximal specific capacitance value when stoichiometric amounts of NiCl₂ and MnCl₂ are equal (cationic ratio of Ni:Mn=1:1) which the specific capacitance is 110 F/g (at a current density of 1A/g). Overall we found that the nickel and manganese oxides have better electrochemical performance compared to the single parts, and while the introduction of nickel oxides can further improve the performance.

Abstract: The structural and electrochemical properties of lanthanum manganate (LaMnO₃) powder prepared by the sol-gel method are researched in this article. The powder calcined at 600 °C showed amorphous, and the powder calcined at 700-800 °C showed the pure phase of the LaMnO₃. The grains with the size of about 80-120 nm were agglomerating together. Cyclic voltammetry and galvanostatic charge-discharge were used to characterize the electrochemical properties in alkaline environment. The electrochemical properties calcined at 700 °C showed a specific capacitance of 73 F/g at the current density of 0.5 A/g. The raw materials for preparing the LaMnO₃ powder are cheap, and the operation method is simple.

Abstract: Cu-Ag alloy nanoparticles were synthesized by a liquid phase reduction method. Using sodium formaldehyde sulfoxylate (SFS) as reducing agents, copper-silver bimetallic nanoleaflets with high content of Cu were prepared. The obtained Cu-Ag bimetallic nanocrystal were characterized by powder X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), field emission scanning electron microscope (FESEM), high resolution transmission electron microscopy (HRTEM) and transmission electron microscopy (TEM). Different molar ratio of Cu-Ag bimetallic nanomaterials could produce different morphologies. The surfactant β-CD plays a crucial role on the structure of the products. The different molar ratios of Cu-Ag were also investigated. The electrochemical activity was evaluated using cyclic voltammetry (CV), electrochemical hydrogen evolution reaction (HER) in a 0.5M Na₂SO₄ electrolyte.

Abstract: WO₃-NiO thin films have been prepared using WO₃ and NiO, deposited on ITO conductive glass by the sol-gel spin coating technique, which has the advantages of simple operation, low cost and high volume production. The composition, surface morphology and electrochemical properties of the obtained films were carried out using X-ray diffraction (XRD), fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and electrochemical workstation. The experimental results show that after 450 °C calcination, it makes the structure of WO₃/NiO obtained by sol-gel method from amorphous into crystalline. Finally, compared with the different films fabricated by different processes, the composite films of WO₃ calcined at 450 °C and NiO can achieve the best electrochemical performance.

Abstract: he effect of pass deformation on the microstructure of Al-Mg-Sn-Bi-Ga-In alloy anode was investigated by using SEM, TEM, and EBSD. The results show that when controlling the rolling deformation at 40%, the segregation phases on the Al alloy matrix was the best distributed for the reason of dynamic recrystallization procedure. The electrochemical and anti-corrosion results show that uniform distribution of segregation phase will improve the related properties of Al alloy anode. After optimizing the rolling procedure, the Al alloy anode has more negative electrode potential of about -1.585V(vs.Hg/HgO) and lower hydrogen evolution rate of 0.092mL/ (min·cm2)

Abstract: Supercapacitor electrodes in the monolithic form were prepared by carbonization and activation of green monoliths (GMs). The GMs and composite GMs were prepared from self-adhesive carbon grains (SACG) of oil palm empty fruit bunches and SACG added with 2 wt.% of multi-layers graphene, respectively. Both GMs and composite GMs were subjected to 18 h and 36 h milling time, respectively. The structure and porosity of the electrodes observed in the Raman spectroscopy and nitrogen adsorption-desorption results, respectively, indicated the effects of graphene addition and doubling the milling times. Galvanic charge discharge results of the supercapacitor cells fabricated using these electrodes showed that the greatest improvement due to the graphene addition occurred for the electrodes prepared based on the lower milling time. The results obtained from the electrochemical characterization showed that specific capacitance, specific power and specific energy of the cell with electrodes from the composite GMs produced from the mixture milled for 18 h were 46 F g^-1, 165 W kg^-1 and 1.2 W h kg^-1, which were ~500 %, ~25 % and ~1100 % better than the other cells.