Synthesis and electrochemical properties of layered Li[Ni0.333Co0.333Mn0.293Al0.04]O2−zFz cathode materials prepared by the sol–gel method

The cathode-active materials, layered Li[Ni_0.333Co_0.333Mn_0.293Al_0.04]O_2−zF_z (0 ≤ z ≤ 0.1), were synthesized from a sol–gel precursor at 900 °C in air. The influence of Al–F co-substitution on the structural and electrochemical properties of the as-prepared samples was characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and electrochemical experiments. The results showed that Li[Ni_0.333Co_0.333Mn_0.293Al_0.04]O_2−zF_z has a typical hexagonal structure with a single phase, the particle sizes of the samples tended to increase with increasing fluorine content. It has been found that Li[Ni_0.333Co_0.333Mn_0.293Al_0.04]O_1.95F_0.05 showed an improved cathodic behavior and discharge capacity retention compared to the undoped samples in the voltage range of 3.0–4.3 V. The electrodes prepared from Li[Ni_0.333Co_0.333Mn_0.293Al_0.04]O_1.95F_0.05 delivered an initial discharge capacity of 158 mAh⁻¹ g and an initial coulombic efficiency is 91.3%, and the capacity retention at the 20th cycle was 94.9%. Though the F-doped samples had lower initial capacities, they showed better cycle performances compared with F-free samples. Therefore, this is a promising material for a lithium-ion battery.     

Preparation and sintering of nano Fe coated Si3N4 composite powders

Fe/Si₃N₄ composite powder was synthesized by the heterogeneous precipitation-thermal reduction process, and then pressed into flakes under a pressure of 10 MPa. Flakes were sintered by pressureless and hot-pressing at 1 600 °C under 0.1 MPa N₂. The chemical composition, phases and microstructure of composite powder and sintered flakes were investigated by energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that the structure of composite powders is Si₃N₄ coated by nano Fe. The crystal phases of sintered flakes by pressureless are Fe(Si) compound, SiC and Si₃N₄. The crystal phases of the sintered samples by hot-pressing are Fe, Fe(Si) compound and Si₃N₄. It is found that crystal phases flakes obtained by pressureless and hot-pressing are very different. Foundation item: Project(50804016) supported by the National Natural Science Foundation of China     

Creep behavior and failure mechanisms of CVI and PIP SiC/SiC composites at temperatures to 1650 °C in air

Creep properties of 2D woven CVI and PIP SiC/SiC composites with Sylramic™-iBN SiC fibers were measured at temperatures to 1650 °C in air and the data was compared with the literature. Batch-to-batch variations in the tensile and creep properties, and thermal treatment effects on creep, creep parameters, damage mechanisms, and failure modes for these composites were studied. Under the test conditions, the CVI SiC/SiC composites exhibited both matrix and fiber-dominated creep depending on stress, whereas the PIP SiC/SiC composites displayed only fiber-dominated creep. Creep durability in both composite systems is controlled by the most creep resistant phase as well as oxidation of the fibers via cracking matrix. Specimen-to- specimen variations in porosity and stress raisers caused significant differences in creep behavior and durability. The Larson-Miller parameter and Monkman-Grant relationship were used wherever applicable for analyzing and predicting creep durability.     

Adaptive multi-mode switching strategy for the spherical underwater robot with hybrid thrusters

The conventional autonomous cruise and tracking system cannot transition and change its motion mode according to the underwater environment during operation, so it is of great significance to study the multi-mode switching of cruise control for Autonomous Underwater Vehicles (AUVs). In this paper, a Multi-Mode Adaptive Switching (MMAS) strategy for the Spherical Underwater Robot with Hybrid Thruster (HPSUR) was proposed, which provided the possibility for the robot to choose optimal control mode according to the unpredictable operating environment. Then, the dynamic and force of the hybrid thruster are analyzed to improve the accuracy of multi-mode switching, and the MMAS strategy is developed linking the attitude adjustment and switching problems. Furthermore, a series of multi-mode switching experiments were conducted using water-jet mode, propeller mode and hybrid mode. Finally, the experimental result was discussed, which verified the effectiveness and accuracy of the proposed MMAS strategy. The proposed control strategy has a certain reference value for the multi-mode switching of propulsion devices.     

Combustion and energy balance of aluminum holding furnace with bottom porous brick purging system

For acquiring the details in aluminum holding furnace with bottom porous brick purging system, efforts were performed to try to find out the potential optimal operation schemes. By adopting transient analysis scheme and constant boundary temperature, combustion in the furnace was investigated numerically using computational fluid dynamics (CFD). The predicted gas temperature shows good agreement with the measured results, and the predicted energy distribution of the furnace is consistent with that obtained from energy balance experiment, which confirms the reliability of the numerical solution. The results show that as the fuel-air mixture temperature rises up from 300 K to 500 K, the energy utilization of the furnace could increase from 34.55% to 37.14%. However, as the excess air coefficient increases from 1.0 to 1.4, energy utilization drops from 34.55% to 29.56%. Increasing the combustion temperature is the most effective way to improve the energy efficiency of the furnace. High reactant temperature and medium excess air coefficient are recommended for high operation performance, and keeping the furnace jamb sealed well for avoiding leakage has to be emphasized.     

Trace amounts of impurities in electrolytic manganese metal by sector field inductively coupled plasma mass spectrometry

An analytical method, using sector field inductively coupled plasma mass spectrometry （SF-ICP-MS） for rapid simultaneous determination of Be, Na, Mg, Si, Ca, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, As, Sn, Sb, Pb and Bi in electrolytic manganese metal, was described. At the beginning, the samples were decomposed by HNO3 and H2504, and then analyzed by SF-ICP-MS. Most of the spectral interferences could be avoided by measuring in different mass resolution modes. The matrix effects due to the excess of sulfuric acid and Mn were evaluated. Correction of matrix effects was conducted by using the internal standard elements. The optimum condition for the determination was investigated and discussed. The detection limit is in the range of 0.001-0.169 gg/L. The current method is applied to the determination of trace impurities in electrolytic manganese metal. And experiments show that good results can be obtained much faster, more accurately and conveniently by current method.     

Growth kinetics of Thiobacillus ferrooxidans in bioelectrochemical cell

Thiobacillus ferrooxidans might be the most important bacteria used in biometallurgy. The foundation way of its growth process is oxidizing ferrous in order to obtain energy needed for metabolism, but the variation of ferrous concentration and mixed potential of the culture media would have crucial effect on the bacteria growth. Based on the characteristics of Thiobacillus ferroxidans growth and redox potential of ferric and ferrous, an electrochemical cell was designed conventionally to study growth rule and the relationship between redox potential and bacteria growth was built up, and some growth kinetics of Thiobacillus ferrooxidans were elucidated. It demonstrates that the variation of open potential of electrochemical cell ΔE shows the growth tendency of Thiobacillus ferrooxidans, at the initial growth stage, the value of δE increases slowly, when at logistic growth stage, it increases drastically, and the growth rate of bacteria is linear with the oxidation rate of ferrous. The bacteria growth kinetics model is proposed using Monod and Michealis-Menten equation, and the kinetics parameters are got. The consistence of the measured and the calculated results proves that it is proper to use the proposed kinetics model and the electrochemical cell method to describe the growth rule of Thiobacillus ferrooxidans. Foundation item: Project (50204001) supported by the National Science Foundation of China     

Dry three-body abrasive wear behavior of WC reinforced iron matrix surface composites produced by V-EPC infiltration casting process

This paper fabricated tungsten carbide (WC) particles reinforced iron matrix surface composites on gray cast iron substrate using vacuum evaporative pattern casting (V-EPC) infiltration process, investigated dry three-body abrasive wear resistance of the composites containing different volume fractions of WC particles, comparing with a high chromium cast iron. The fabricated composites contained WC particles of 5, 10, 19, 27, 36, and 52 vol.%, respectively. The results in abrasive wear tests showed that, with the increase in the volume fraction of WC particles, the wear resistance of the composites first increased until reached the maximum when the volume fraction of WC was 27%, then decreased, and was 1.5–5.2 times higher than that of the high chromium cast iron. The changes of the wear resistance of the composites with the volume fraction of WC particles and the mode of material removal in dry three-body abrasive wear condition were analyzed.     

[100]取向Al-Ti共掺杂ZnO薄膜的制备与光电性能研究

采用常压固相烧结法制备了Al-Ti共掺ZnO靶材, 采用射频磁控溅射技术及真空退火工艺, 在普通玻璃衬底上制备了具有[100]取向Al-Ti共掺杂ZnO薄膜(ZATO). 采用X射线衍射(XRD)、扫描电子显微镜(SEM)对ZATO薄膜的生长机理、显微结构、形貌进行了测试分析, 用四探针测试仪、紫外-可见分光光度计及荧光光谱仪对ZATO薄膜的光电性能进行了测试分析. 结果表明, ZATO薄膜经500℃保温3h退火后, 择优取向由(002)向(100)方向转变; 此时, 衍射谱上还观察到超点阵衍射线条. [100]取向ZATO薄膜的光学带隙从退火前的3.29降至2.86, 平均可见光透过率从90%降至70%, 表现为一般的透过性; 而电阻率则从1.89×10^-2Ω·cm降至1.25×10^-3Ω·cm, 呈现较好的导电性. 薄膜中均出现了380nm附近的带边发射(NBE)峰以及410、564nm的深能级发射峰, 且经500℃保温3h退火后, 这些峰的位置并未改变, 但峰强均明显减弱. 对上述实验机理进行了分析讨论.