Papers by Author: Gui Yang Liu

Abstract: Sn-Ni intermetallic compounds have been prepared by a chemical reduction method. With different molar ratios of Sn/Ni, the products are different. XRD determination results indicate that the main phases of the products with Sn/Ni=1:0.5 and 1:1.0 are Sn6O4(OH)4 and metal Sn, and the main phases of the products with Sn/Ni=1:1.5 and 1:2.0 are SnNi, Ni3Sn and metal Sn. SEM investigation finds that the particle size of the products with Sn/Ni=1:1.5 and 1:2.0 are nano size, and the particle size increases with increasing Ni content. The particles of the product with Sn/Ni=1:1.5 are in the range of 50-100nm, and well dispersed.

Abstract: LiFe0.05Mn1.95O4 materials were prepared by molten-salts combustion synthesis and solution combustion synthesis methods, respectively. The phase structure and compositions of the products were determined by X-ray diffraction (XRD). The main phase of the products prepared by the two methods is LiMn2O4, but at 300-600oC, pure products can not be obtained. At the temperatures of 300 and 400oC, the main impurities are MnO and Mn3O4. The impurities decrease with increasing temperatures, and finally disappear at >500oC. At 500 and 600oC, the main impurity is Mn2O3, but the relative content of Mn2O3 is low.

Abstract: In this paper, LiNixMn2−xO4 materials were prepared by solution combustion synthesis method using acetic salts as raw materials and acetic acid as fuel. The phase structures are characterized by X-ray diffraction (XRD). Electrochemical performances of the materials are investigated by galvanostatic charge/discharge methods. XRD results revealed that the main phase of the products with increasing Ni3+ content is LiMn2O4, and there is a trace amount of Mn3O4 found in the product with Ni3+ content of 0.05. Electrochemical experiments showed that the capacity and the cyclability of the LiNixMn2−xO4 materials decrease with increasing Ni3+ content. Ni3+ doping has no significantly improvement for the capacity and the cyclability of the LiMn2O4 spinel.

Abstract: LiAl0.1Mn1.9O4 materials were prepared by a solution combustion synthesis method. In order to improve the purity of the products, the effect of further calcination time was investigated. The phase compositions of the as-prepared products were determined by X-ray diffraction (XRD). The electrochemical performance of the products was tested by using a coin-type half battery versus lithium metal foil as anode material. XRD results suggested that the main phase of the products was LiAl0.1Mn1.9O4, and there was a trace amount Mn2O3 impurity in some of the products. The purity, crystallinity and grain size of the LiAl0.1Mn1.9O4 were increased with increasing further calcination time. Electrochemical experiments demonstrate that the initial discharge capacities of the products with further calcination time of 0, 6, 12 and 24h were 93.7, 105.7, 114.0 and 120.6mAh/g, and about 89.8, 89.5, 89.2 and 88.3% of the initial capacities were retained after 25 cycles, respectively. Further calcination time can enhance the initial capacity, but is not favorable for the cycle ability of the products.

Abstract: Spinel LiMn2O4 have been prepared by the solution combustion synthesis method using acetate salts as raw materials and acetic acid as fuel. The phase compositions of the as-prepared products were determined by X-ray diffraction (XRD). The electrochemical performance of the products was tested by using a coin-type half battery versus lithium metal foil as anode material. XRD results suggested that the purities of the products prepared at 500oC are higher than these of the products prepared at 600oC. For the products prepared at 500oC, the purities of the products increase with increasing acetic acid ratios. But for the products prepared at 600oC, the purities of the products decrease with increasing acetic acid ratios. The performance tests indicated that the electrochemical performances of the products prepared at 500oC are better than these of the products prepared at 600oC. The product prepared at 500oC with the acetic acid ratio of 1.0 gets the best performance. The initial capacity of it reaches to 124.8mAh/g at the current density of 75mA/g, and after 50 cycles, the capacity retention is 93.7%.

Abstract: The MgO-Al₂O₃-SiO₂ (MAS) glass powders have been synthesized by low-temperature combustion technique using magnesium nitrate, aluminium nitrate, silicic acid as material, urea as fuel. The crystallization process, sintering behavior and dielectric properties were investigated by means of DTA, XRD, TMA and SEM techniques. The results showed that the glass powders could be sintered at lower than 1000°C. The μ-cordierite phase was first crystallized from glass and then transformed into α-cordierite phase during sintering process. The obtained cordierite-based glass-ceramics at 950°C and 1000°C have low dielectric constant (4.00 ~ 4.96 at 1 MHz), low dielectric dissipation factor (≈ 0.003) and high sintering density (which is above 98% of the theoretical density), which are used for electronic packaging.

Abstract: To study the interaction between hydroxyapatite (HAP) and collagen in bone, we researched the phenomenon of collagen biomineralization and self-assembly in viro by uv-vis spectra and circular dichroism (CD) spectra. The materials prepared by self-assembly collagen and collagen-HAP showed layer structures. And the product prepared by collagen-HAP had better and more compact appearance. The decrease of speed of collagen self-assembly was caused by calcium ion or strontium ion added. The trough of CD spectra moved down in calcium-containing solution and moved up when forming precipitation of calcium phosphate from the solution. It indicated that the effect of collagen self-assembly was caused by calcium ions, strontium ions etc. in the solution. The IR spectrum proved that a coordinate bond formed between calcium ion and amide groups on collagen.

Abstract: Spinel LiMn₂O₄ was synthesized by a solution combustion synthesis using lithium and manganese acetate as raw materials and acetic acid as fuel. The phase composition and micro morphology of the as-prepared products were determined by X-ray diffraction (XRD) and scanning electric microscope (SEM). The electrochemical performance of the products was tested by using a coin-type half battery versus lithium metal foil as anode material. XRD analysis suggested that the main phase of the products was LiMn₂O₄, but there was little impurity Mn₂O₃ in the products. The relative content of Mn₂O₃ was decreased gradually when the molar ratio of Li:Mn: acetic acid increased from 0.5:1:0.5 to 0.5:1:2, but increased again when the molar ratio of Li:Mn: acetic acid was 0.5:1:2.5. The purest product could be prepared when the molar ratio of Li:Mn: acetic acid=0.5:1:2. SEM investigation indicated that the typical crystal structure could not be investigated from the as-prepared products, and the particles were badly agglomerated. Electrochemical performance tests indicated that the specific capacity of the purest product was 108mAh/g. After 30 cycles, the capacity faded only 22% at the current density of 50mA/g, and the average charge/discharge efficiency was ~96%. At the current density of 75mA/g, the initial specific capacity of the purest product was only 72mAh/g, but after 30 cycles, the capacity retention was >92%, exhibiting a good cycling performance.

Abstract: Spinel LiMn₂O₄ have been prepared by a flameless solution combustion synthesis, using nitrate and acetate salts as raw materials without any fuels. The effect of ignition temperature on the phase structure, micro morphology and electrochemical performance has been studied. The results indicate that spinel LiMn₂O₄ with single phase can be prepared successfully by the present method at the ignition temperatures of 300-800°C and calcination temperature of 600°C for 5h. The crystallinity, dispersity of the gains and electrochemical performance of the products increase with the decreasing ignition temperatures.

Abstract: To improve the cyclability of spinel LiMn₂O₄, Al³⁺ doped LiAl_xMn_2−xO₄ (x=0, 0.01, 0.05 and 0.10) materials are prepared using a solution combustion synthesis method using acetic salts as raw materials and acetic acid as fuel. Their phase structures are characterized by X-ray diffraction (XRD). Electrochemical performances of the materials are investigated by galvanostatic charge/discharge methods. XRD results reveal that the purity of the samples increases with increasing Al³⁺ content. Electrochemical experiments demonstrate that the charge/discharge cyclability of the LiAl_xMn_2-xO₄ increases with increasing Al³⁺ content. Compared with the pristine LiMn₂O₄, the Al-doped LiAl_xMn_1−xO₄ show the obviously improved cyclability, especially for the sample LiAl_0.1Mn_1.9O₄.