Liu Ye-xiang

Cu2SixSn1−xS3 Thin Films Prepared by Reactive Magnetron Sputtering For Low-Cost Thin Film Solar Cells

We report the preparation of Cu2SixSn1−xS3 thin films for thin film solar cell absorbers using the reactive magnetron co-sputtering technique. Energy dispersive spectrometer and x-ray diffraction analyses indicate that Cu2Si1−xSnxS3 thin films can be synthesized successfully by partly substituting Si atoms for Sn atoms in the Cu2SnS3 lattice, leading to a shrinkage of the lattice, and, accordingly, by 2θ shifting to larger values. The blue shift of the Raman peak further confirms the formation of Cu2SixSn1−xS3. Environmental scanning electron microscope analyses reveal a polycrystalline and homogeneous morphology with a grain size of about 200–300 nm. Optical measurements indicate an optical absorption coefficient of higher than 104 cm−1 and an optical bandgap of 1.17±0.01 eV.

Effects of drying method on preparation of nanometer α-Al2O3

Ammonium aluminum carbonate hydroxide (AACH) precursor was synthesized by the precipitation reaction of aluminum sulfate and ammonium carbonate. Then the precursor was dealt with five drying methods including ordinary drying, alcohol exchange, vacuum freeze-drying, glycol distillation, n-butanol azeotropic distillation respectively and calcined at 1 200 °C for 2 h to get α-Al2O3. The effects of drying methods on preparation of nanometer α-Al2O3 were discussed, and the optimal drying method was confirmed. The structural properties of powders were characterized by XRD, SEM and BET measurements. The results show that vacuum freeze-drying, glycol distillation and n-butanol azeotropic distillation can prevent the powders from aggregating, and among them the n-butanol azeotropic distillation is the best method. The nanometer α-Al2O3 powder with non-aggregation can be manufactured using n-butanol azeotropic distillation and the average particle size is about 40 nm.

A Novel Modification Approach for Natural Graphite Anode of Li-ion Batteries

To improve the rate capability and cyclability of natural graphite anode for Li-ion batteries, a novel modification approach was developed. The modification approach included two steps: (a) high-energy ball milling in a rotary autoclave containing alumina balls, H3 PO4 and ethanol; (b) coating with pyrolytic carbon from phenlic resin. The treated graphite shows obvious improvement compared with the original natural graphite in electrochemical properties such as cyclability and rate capability, especially at high current density. The primary reasons leading to the improvement in rate capability and cyclability are that the diffusion impedance of Li+ in graphite is reduced due to the fact that P filtered into graphite layers can mildly increase interlayer distances, and the fact that the structural stability of graphite surface is enhanced since the coated pyrolytic carbon can depress the co-intercalation of solvated lithium ion.

2D finite element analysis of thermal balance for drained aluminum reduction cells

Based on the principle of energy conservation, the applicable technique for drained cell retrofitted from conventional one was analyzed with 2D finite element model. The model employed a 1D heat transfer scheme to compute iteratively the freeze profile until the thickness variable reached the terminating requirement. The calculated 2D heat dissipation from the cell surfaces was converted into the overall 3D heat loss. The potential drop of the system, freeze profile and heat balance were analyzed to evaluate their variation with technical parameters when designing the 150 kA conventional cell based drained cell. The simulation results show that the retrofitted drained cell is able to keep thermal balance under the conditions that the current is 190 kA, the anodic current density is 0.96 A/cm2, the anode-cathode distance is 2.5 cm, the alumina cover is 16 cm thick with a thermal conductivity of 0.20 W/(m·°C) and the electrolysis temperature is 946 °C.

Effect of electrolysis superheat degree on anticorrosion performance of 5Cu/(10NiO-NiFe2O4) cermet inert anode

Abstracts5Cu/(10NiO-NiFe2O4) cermet inert anodes were prepared by cold-pressing and sintering process, and the effect of superheat degree of melting K3AlF6-Na3AlF6-AlF3 on their anticorrosion performance was studied under electrolysis conditions. The results show that, the fluctuation of cell becomes small with increasing of superheat degree, which is helpful to inhibit the formation of cathodic encrustation; the concentration of impurities from inert anode in bath goes up to certain degree, but it is far smaller than those in traditional high-temperature bath. Increasing the superheat degree of melting K3AlF6-Na3AlF6-AlF3 has unconspicuous effect on the contents of impurities in cathodic aluminum. The total mass fractions of Fe, Ni and Cu in aluminum are 15.38% and 15.09% respectively under superheat degree of 95 and 195 °C. From micro-topography of anode used view, increasing the superheat degree can aggravate corrosion of metal Cu in inert anode, and has negative influence on electrical conductivity of electrode to some extent.

Electrochemical characterization of surface-modified LiMn2O4 cathode materials for Li-ion batteries

To improve the performance, the surface of LiMn2O4 was coated with very fine MgO, Al2O3 and ZnO by sol-gel method, respectively. The structure and morphology of the coated materials were investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The charge and discharge performance of uncoated and surface modified LiMn2O4 spinel at 25°C and 55°C were tested, using a voltage window of 3.0–4.35 V and a current density of 0.1 C rate. There is a slight decrease in the initial discharge capacity relative to that of uncoated LiMn2O4, but the cycle ability of Li LiMn2O4 coated by metal-oxide has remarkably been improved. The EIS measurements of uncoated and Al2O3-coated LiMn2O4 were carried out by a model 273 A potentiostat/galvanistat controlled by a computer using M270 software, and using a frequency response analyzer (Zsimpwin) combined with a potentiostate (PAR 273). Consequently, the reason for the improved cycle properties is that the surface modification reduces the dissolution of Mn, which results from the suppression of the electrolyte decomposition, and suppresses the formation of passivation film that acts as an electronic insulating layer. In conclusion, the use of surface modification is an effective way to improve the electrochemical performance of LiMn2O4 cathode material for lithium batteries.

Development of Low‐Voltage Energy‐Saving Aluminum Reduction Technology

In this study, the representative low-voltage energy-saving techniques for aluminum reduction in recent years in China is reviewed, and two low-voltage energy-saving techniques are described, which include the technique based on innovation of the electrolytic technology and the process control and the one based on comprehensive innovation of cell structure, the electrolytic technology and the process control. The results show that the best energy consumption index can be realized with the application of low-voltage technology and advanced process control technique on the cells designed at the concept of “conventional planar cathode + suitable heat preservation enhancing”.

Preparation of Chalcopyrite Cuinse2 Thin Films by Pulse-Plating Electrodeposition and Annealing Treatment

CuInSe2 (CIS) thin films have been prepared on molybdenum substrates by pulse-plating electrodeposition from an aqueous solution containing CuCl2, InCl3, SeO2 and Na-citrate. The most suitable pulse potential range for co-deposition is found to be-0.6~-0.75V vs the saturated calomel electrode (SCE). The electrodeposited films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDS). The influence of the square pulse potential on crystallinity, surface morphology and compositions has been studied. Chalcopyrite phase CuInSe2 films with smooth surfaces and stoichiometric composition have been obtained at a pulse potential of-0.65~-0.7V vs.SCE and annealing treatment.

Bisensors for amino acids

Two kinds of biosensors for amino acids (one with nonspecific enzyme as bioelement, the other with specific enzyme(s) as bioelement), including their principles, applications, recent researches and future trends were discussed in detail. 61 references were given.Two kinds of biosensors for amino acids (one with nonspecific enzyme as bioelement, the other with specific enzyme(s) as bioelement), including their principles, applications, recent researches and future trends were discussed in detail. 61 references were given.