Advanced Materials Research Vols. 197-198

Abstract: Li[Li_(1/3-x)Mn_(2/3-x)Ni_xCo_x]O₂ (x=0.1, 0.15, 0.2, 0.22, 0.25) compounds were synthesized and studied by the X-ray diffraction method and electrochemical techniques. The XRD analysis showed that these compounds could be classified as the α-NaFeO₂ structure type. Both a and c parameters decreased linearly, while c/a increased with the increase of Ni and Co content. The first discharge capacity increases with increasing lithium content at the 3a sites in the Li[Li_(1/3-x)Mn_(2/3-x)Ni_xCo_x]O₂. A Li[Li_0.23Mn_0.57Ni_0.1Co_0.1]O₂ electrode delivers discharge capacities of 238 mAh/g at C/10 between 4.6V and 2.5V.

Abstract: The most promising hydrogen storage materials are perhaps complex metal hydrides. Thus, a plausible first step in the rehydrogenation mechanism is proposed by simulating the reversible hydrogen storage in Zr-doped NaAlH₄. It provides insight into the catalytic role of Zr atoms on an Al surface in the chemisorptions of molecular hydrogen. It is found that the diffusion of hydride species on Al-metallic phase and formation of Al hydride species is probably the key to syntheses the next products in the rehydrogenation reaction.

Abstract: A polyurethane/clay (PU/clay) composite was synthesized. The microstructure of the composite was examined by scanning electron microscopy. The impact properties of the composite were characterized by impact testing. The study on the structure of the composite showed that clays could be dispersed in the polymer matrix well apart from a few of clusters. The results from mechanical analysis indicated that the impact properties of the composite were increased greatly in comparison with pure polyurethane. The investigation on the mechanical properties showed that the impact strength could be obviously increased by adding 20 wt% (by weight) clay to the matrix.

Abstract: The evolution of the recrystallization texture under high current density electric current pulses (ECP) was investigated in a cold-rolled Fe-3%Si steel sheet. Results showed that the preferred nucleation always occurred in the direction parallel to the current direction at the primary stage of recrytallization. With the increment of the current density, the effect of current direction on texture and microstructural evolution was decreased. Due to the different texture component along the layer depth under different current densities, it was also found that the recrystallization nucleation was much easier to occur from the top surface.

Abstract: Thermoelectric Bi₂Te₃ bulk alloys were directionally solidified successfully at the pulling rate ranging from 1 μm/s to 50 μm/s under a high temperature gradient of 200 K/cm. Preferred crystal orientations of (0 1 5), (1 0 10) and (1 1 0) faces appeared at the pulling rate of 50 μm/s. In the Bi₂Te₃ alloys directionally solidified at 5 μm/s, the maximum Seebeck coefficient of -253 μV/K was obtained and the maximum electrical resistivity of 2.26 mΩ•cm was measured at 300 K. Besides, the optimum Power Factor (PF) value reached 3.83×10^-3 W/K²m at 1 μm/s and the measured results show that the thermoelectric Bi2Te3 bulk alloys grown at low growth rates supply the large PF value at ambient temperate, while at high temperature, the alloy grown at 50 μm/s has a better PF value.

Abstract: The platelike Co₃O₄/carbon nanofiber (CNF) composite materials were synthesized by the calcination of β-Co(OH)₂/CNF precursor prepared by a surfactant-free hydrothermal method. As negative electrode materials for lithium-ion batteries, the platelike Co₃O₄/CNF composites can deliver a high reversible capacity of 900 mAh g^-1 for a life extending over hundreds of cycles at a current density of 100 mA g^-1. The high Li-storage capacity and excellent cycling performance for Co₃O₄/CNF composite materials may mainly attribute to the beneficial effect of the CNFs addition on enhancing structural stability and electrical conductivity of Co₃O₄ platelets.

Abstract: A novel composite phase change material (PCM) was prepared with phase change material (paraffin), storage medium (expanded perlite) and coating material (VAE emulsion), which was added to the gypsum to prepare the gypsum-based energy storage material(GESM). The microstructure and thermal properties of samples were characterized by scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). The results showed that the expanded perlite had good adsorption of paraffin, and the best adsorption capacity was 50%. The prepared samples had good thermal physical properties.

Abstract: Lithium difluoro(oxalate)borate (LiODFB) as an alternative salt for lithium-ion batteries, its application was limited by salt synthesis. In this study, high purity LiODFB was synthesized by simple and continuous technology using purified self-made BF₃, the inert atmosphere and vacuum protection was avoided. Moreover, 0.7 mol L^-1 LiODFB-PC (propylene carbonate)/EMC (ethyl methyl carbonate)/DMC (dimethyl carbonate) (1:1:1, by volume) were prepared to assembling Li/MCMB (mesocarbon microbead) cell. Solid Electrolyte Interphase (SEI) was formed to stabilized MCMB structure even in one third (by volume) of PC in the electrolyte with the help of LiODFB. LiFePO₄/Li cell was assembled as well. The cell based on LiODFB had excellent cycling performance and capacity retention.

Abstract: The effect of the combined action of hot work and heat treatment on the microstructure and mechanical properties of a Mg-2Gd-Nd-0.4Zn-0.3Zr (wt. %) (E21) alloy was investigated. Results showed that the solution treatment time of the ingot played a great effect on the mechanical properties of the extruded alloy. With solution treating time of the ingot increasing, the tensile strength of the extruded alloy decreased gradually, but the elongation increased greatly. The best combination of strength and ductility was achieved for the extruded alloy after the ingot solution treated at 520°C for 3 h, extrusion at 400°C and aging at 200°C for 16 h, namely ultimate tensile strength = 331MPa and elongation = 7.1%.

Abstract: Morphologies, microstructure and composition distribution of the magnesium anodic materials were studied by metallographic microscopy, x-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). The corrosion behavior and electrochemical properties of Mg alloy were also investigated by constant current method, potential polarization, collecting gas through drainage. The results show that tin restrained β-Mg₁₇Al₁₂ phase precipitation along the grain boundary. With the content of tin increasing, granular Mg₂Sn phase was improved. After uniform heat treatment, most of β-Mg₁₇Al₁₂ phase was dissolved, but most of Mg₂Sn was not dissolved. Tin could improve self-corrosion potential and release hydrogen rate. Magnesium alloy anode with 1% tin content had high discharge potential and current efficiency. With the current density increasing, the release hydrogen rate augmented. The current efficiency reached 82 % at 20mA/cm². The main composition of the corrosion products were MgO and Al²O³ which were easily peeled off. As a result, more negative and stable work potential was produced and the reaction was accelerated continuously.