Advanced Materials Research Vols. 399-401

Abstract: The spinel-type Li₄Ti₅O₁₂ cathode materials were synthesized by a self-combustion method. The effects of synthesis temperature on the structural and electrochemical properties of the Li₄Ti₅O₁₂ were investigated. The prepared samples were characterized by X-ray diffraction (XRD), SEM, TEM and electrochemical analysis. The results revealed that pure phase and well-crystallized Li₄Ti₅O₁₂ with nano-sized could be synthesized at a calcination temperature of 750°C. The sample prepared under the condition had the highest initial discharge capacity of 164 mAh/g and shown good capacity rentention during 50 cycles between 1.0-2.5V at 0.1C.

Abstract: The layered cathode material for Li-ion batteries was synthesized by mechanical activation-high temperature solid state method. XRD and electrochemical measurements were used to characterize the structure and electrochemical performance of the product. The X-ray diffraction (XRD) patterns reveal that the material is crystallized to layered a-NaFeO₂ structure. The cathode material with excellent electrochemical performance was obtained by sintering the mixed raw materials with n (Li)/n (M) =1.11. The initial discharge capacity was 128mAh/g at a current density of 20mA/g between 2.7-4.2V and the discharge capacity retention was 96% after 50 cycles.

Abstract: The nano precursors of La-Mg hydrogen storage alloy have been prepared using citric acid, lanthanum nitrate and magnesium nitrate by so-gel technology. The effect of citric acid and calcination temperature on microstructure of the nano precursors of La-Mg hydrogen storage alloy have been studied by Infrared Radiation (IR), thermogravimetric and differential thermal analysis (TG/DTA), X-ray diffraction analyzer (XRD) and Transmission electron microscopy (TEM). IR results indicate the molar ratio of citric acid to metal cations increases from 1 to 1.3, the amount of citrate increases correspondingly, when the molar ration increases to 1.6, the amount of citrate goes up to maximum. The most appropriate amount of citric acid is 1.6 times that of the metal cations. In addition, the amount of citric acid have little influence on size of grains. XRD and TG/DTA results show that with increase of calcination temperature the amount of impurity phase, La(OH)₃, decreases markedly. Formation of La₂O₃ and MgO two-phase mixture occurred at 950°C. TEM results reveal that the morphology of the particles is almost flake with the size of ~50nm at 950°C and La, Mg, O three elements are observed in each flake.

Abstract: Anaerobic fermentation experiments were conducted on banana (pseudo) stem residue to study the relationship between fermentation temperature and gas production yield and gas production rate, and methane content. Based on fixed dry matter concentration, inoculum concentration and fermentation time, different temperatures, i.e. 25, 30, 35, 40°C were selected and formed four experimental groups. Four levels of single factor tests were conducted to optimize temperature parameter for anaerobic fermentation of banana stem residue. The results showed that the daily gas yield of banana stem residue reached the maximum value of 36.8L on the fourth day at 35°C, and the average gas yield was 5.03L/d. The total gas yield was 402.3L, while the maximum methane content was 61.2% in the whole fermentation process. The results indicated that the comprehensive effect was best at 35°C in anaerobic fermentation of banana stem residue.

Abstract: The K4Nb6O17 powders were synthesized via a high temperature solid phase reaction and the effects of calcination temperature and calcination time were investigated. The powers were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and ultraviolet-visible diffuse reflection spectra (UV-VIS). The photocatalytic properties of these catalysts for hydrogen production were also investigated in the presence of Na₂S and Na₂SO₃ sacrificial reagents. The results revealed that the optimal synthesis condition is calcination for 2h under 1000°C. Grain-like particles could be obtained with a rapid temperature rising rate, while rod-like particles were obtained with a slow rate. The K₄Nb₆O₁₇ sample exhibited high activities for photocatalytic hydrogen production under UV light, and the highest activity of 95.4 mmol/(g cat) was achieved over the sample which at 1000°C for 2h with the temperature rising rate of 20°C/min.

Abstract: Amorphous porous FePO₄·3H₂O micro-spheres were synthesized via a controlled crystallization method. These micro-spheres have a particle size distribution from 10 to 28 μm. There are larger numbers of pores on the surface of FePO₄·3H₂O microspheres, which are important to synthesize high performance LiFePO₄ cathode materials for the application of lithium ion battery. The electrochemical properties of the LiFePO₄/C electrode, preparing by using the above porous spherical FePO₄·3H₂O particles, were measured. The electrochemical results show that the obtained LiFePO4/C has a high initial discharge specific capacity of 141.4 mAhg^-1 and good cycling performance at 0.5 C. The microstructural and electrochemical analyses indicate that this porous spherical FePO₄·3H₂O is a fascinating precursor for preparing LiFePO4/C cathode materials.

Abstract: LiCo_1/3Ni_1/3Mn_1/3O₂ has been modified with LaF₃. The surface modified materials were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and galvanostatic charge-discharge cycling. The LaF₃-coated LiCo_1/3Ni_1/3Mn_1/3O₂ had an initial discharge specific capacity of 178.0 mAh•g–1 within the potential ranges 2.75–4.5 V (vs. Li+/Li), and its discharge specific capacity is 168.7 mAh•g–1 after 50 cycles, much higher than that of the pristine LiCo_1/3Ni_1/3Mn_1/3O₂ (148.4 mAh•g^–1). The improvement could be attributed to the LaF3 coating layer that hinders interaction between LiCo_1/3Ni_1/3Mn_1/3O₂ and electrolyte and stabilizes the structure of LiCo_1/3Ni_1/3Mn_1/3O₂ .

Abstract: A Cd-Fe redox flow battery is proposed, in which CdSO₄-H₂SO₄ aqueous solution is used as negative electrolyte, FeSO₄-Fe₂(SO₄)₃-H₂SO₄ aqueous solution is used as positive electrolyte, copper is used as negative electrode, carbon felt is used as positive electrode and proton exchange membrane is used as separator. Fe²⁺ is oxidized to Fe³⁺ at positive electrode and the Cd²⁺ is reduced to cadmium and electroplated onto the negative electrode during charge. The reverse occurs during discharge. An average discharge cell voltage of about 0.99V at 10mA/cm² and an average energy efficiency of about 70.8% are obtained.

Abstract: Three different chemical reductions are used to synthesize spherical silver particles with different sizes. The results show that the sizes of silver particles by glucose、HCOONH₄ and NaBH₄ reduction are 49nm, 187nm and 37nm and those silver particles with the size below 100nm by HCOONH₄ and NaBH₄ reduction have narrow size distributions of 30-70nm. In addition, it has been found that adding a small amount of silver nano-particle can improve the conductivity of that whose size surpasses 100nm which is beneficial to the increase of efficiency of the solar cell when adding it into the silver electronic paste.

Abstract: Castor oil and microcrystalline cellulose were employed as biomass feedstock to produce bio-based polymer composites with increased tensile strength. The polymer composites were prepared by curing castor oil with 4,4'-methylenebis (phenyl isocyanate) (MDI) in the presence of microcrystalline cellulose (MC) or modified MC (MMC). The MMC was prepared by reacting MDI with MC to introduce isocyanate groups to the surface of MC. X-ray diffraction spectra suggested the good retention of the crystalline structure of MC or MMC in the composites. SEM analysis showed the well dispersion of MC or MMC in the composites. All of these factors are critical to reinforcing the composites. Mechanical tests of the composites revealed that the reinforcing effect of MMC was more significant than MC at high cellulose content such that the highest tensile strengths of 4.87 MPa was obtained for the composite containing 43% (wt) of MMC. That is almost 5 times higher than that of neat castor oil-based polyurethane.