Investigation of the Tool Wear Rate in Tungsten Powder-Mixed Electric Discharge Machining of AA6061/10%SiCp Composite

This paper presents the experimental investigation on tool wear rate (TWR) in powder-mixed electrical discharge machining (PMEDM) of aluminum 6061 alloy reinforced with 10% silicon carbide particles (AA6061/10%SiC_p composite). Composite material is fabricated by mechanical stir casting process and further characterized by scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). Tungsten powder with concentration of 4 g/L is mixed in the dielectric fluid. To know the influence of powder suspension in dielectric fluid on TWR, comparative study is done on the basis of experiments performed using basic EDM and PMEDM process. Experiments have been designed as per central composite rotatable design (CCRD) using response surface methodology (RSM) approach. Four process parameters, namely, peak current, pulse-on time, pulse-off time, and gap voltage have been considered for TWR investigation. Individual and interactive influence of various parameters on TWR is explained with the help of analysis of variance and three-dimensional graphs. Using RSM approach, results have been further optimized. PMEDM approach provides 51.12% reduction in TWR for machining of AA6061/10%SiC_p composite.     

WO3 membrane-encapsulated layered LiNi0.6Co0.2Mn0.2O2 cathode material for advanced Li-ion batteries

Despite Nickel-rich materials have all the advantages of high capacity, long cycle life and low cost, there is still a disadvantage that the capacity decreases rapidly as the number of cycles increases. In order to solve this problem, WO₃ was uniformly coated on the surface of LiNi_0.6Co_0.2Mn_0.2O₂ cathode materials by wet coating, and its cycling performance was greatly improved with the higher capacity. The coated materials were analyzed by X-ray diffraction(XRD), Scanning electron microscope (SEM), high resolution Transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy(XPS). The results showed that the coating thickness was around 3.15?nm, and some tungsten ions were doped into the lattice of the near surface area of the LiNi_0.6Co_0.2Mn_0.2O₂ material. In addition, the results of charge-discharge test showed that 1?wt%WO₃ coating LiNi_0.6Co_0.2Mn_0.2O₂ had the best performance, and delivered a discharge capacity of 140 mAh g^?1 (the capacity retention rate is 84.8%) in the potential interval of 2.8–4.3?V at 1?C (1?C?=?165?mA?g^?1) after 200 cycles, while the bare cathode material only delivered a discharge capacity of 120 mAhg^?1 (the capacity retention rate is 75%). The phenomenon indicates that the WO₃ coating plays a role in inhibiting the harmful side reactions between the cathode material and the electrolyte, improving the electrochemical and structure stability of LiNi_0.6Co_0.2Mn_0.2O₂ cathode materials.     

Tungsten phosphide nanosheets seamlessly grown on tungsten foils toward efficient hydrogen evolution reaction in basic and acidic media

Exploring earth-abundant electrocatalyst with active and stable hydrogen evolution reaction (HER) properties is desirable but still challengeable. Herein, WP₂ nanosheets are seamlessly grown on W foil (WP₂ NSs/W) through phosphorization of WO₃/W. This seamless WP₂/W structure is beneficial to reducing the resistance between WP₂ and W. Along with the exposed large density of active sites, WP₂ NSs/W displays outstanding HER activity with a lower onset potential of about 0 V, a smaller overpotential of 90 mV for the current density of 10 mA/cm² in basic media. Notably, WP₂ NSs/W electrode also catalyzes HER efficiently in acid. The synthesis of WP₂ NSs/W provides us a straightforward strategy to gain more cost-effective cathode for HER.     

Facile synthesis of IrO2 nanoparticles decorated @ WO3 as mixed oxide composite for outperformed oxygen evolution reaction

Oxygen evolution reaction (OER) electrocatalysts play the critical role in efficiency and durability for different hydrogen production systems. We have successfully synthesized the earth abundant WO₃ coupled with IrO₂ as mixed oxide composite by a facile two-step chemical method. 50% reduction in noble metal contents (IW-50) followed by two times enhancement in activity, four-folds increase in bulk mass specific activity along with the stability of mixed oxide composite as compared to state –of –the art IrO₂ catalyst are affirmed. Superior performance of mixed oxide composites are perceived due to four times increase in electrochemical surface area, reduction of Tafel slope, four-fold increase of turn over frequency, electronic distortion in Ir-4f spectrum of IW-50 along with the bridging of lattice oxygen atoms between iridium and tungsten metals. We believe that it would open up the new avenues for effective utilization of noble metal with high valence tungsten metal in corrosive environment.     

纯粹几何·古典精神——从格拉斯舒特住宅到三号住宅

对于大多数中国人来讲，奥斯瓦尔德·马蒂亚斯·翁格斯这个名字并不为人熟知，但在德国和欧洲地区，他是德国战后最重要的建筑师，也是德国新理性主义思潮的领军人物。其多产的一生为世人留下了大量伟大的建筑作品，他的创作思想深深影响了一大批欧洲建筑师。翁格斯的大多喜欢运用立方体等几何形体作为造型语汇，作品强调基于数字比例的严谨秩序，追求简化到极致的纯净形式，他的几所自宅尤其是后来的格拉斯舒特住宅和三号住宅都是他个人设计思想的最好体现。文章通过对格拉斯舒特住宅及三号住宅的对比分析，阐述了翁格斯追求纯粹几何形体的造型手法以及基于严谨数字比例的生成机制，探讨了背后蕴含的场所意义以及原型思想和古典精神。     

Kinetics of Reaction between Iron Ore Fines and Coal or Char Fines

Iron ore fines and coal fines can be made to react to produce direct reduced iron (DRI) fines. There are three ways to achieve the reactions, namely, (a) using homogeneous mixtures, (b) arranging the ore and coal fines in separate but adjacent layers and (c) by fluidizing a mixture of iron ore fines and coal fines by air. This paper mainly discusses the work done by the author and his coworkers on the kinetic aspects of reactions in such systems.     

WO3/BiVO4 composite photoelectrode prepared by improved auto-combustion method for highly efficient water splitting

We report on the improvement in the water splitting efficiency of a WO₃/BiVO₄ composite photoelectrode by the application of an improved auto-combustion method to the preparation of porous BiVO₄ thin films. The unique feature of this preparation method is the addition of both NH₄NO₃, as a strong oxidizing agent, and an organic additive into BiVO₄ precursor solution. The local decomposition heat of the organic additive and oxidizing agent created a porous film with small, highly crystalline BiVO₄ particles. The photoelectrode has many advantages over existing ones, such as the high light-harvesting efficiency (LHE), a single BiVO₄ phase, the facile access of the holes to the photoelectrode/electrolyte interface, and the ease of water and oxygen diffusion. The maximum incident photon-to-current efficiency (IPCE) was estimated to be 64% (at 440 nm, 1.23 V vs. RHE) and the applied bias photon-tocurrent efficiency (ABPE) reached as high as 1.28%. This ABPE value is highest among all oxide semiconductor photoelectrodes reported previously, except for the case of a stacking photoelectrode system.     

A combined physicochemical and electrocatalytic study of microwave synthesized tungsten mono-carbide nanoparticles on multiwalled carbon nanotubes as a co-catalyst for a proton-exchange membrane fuel cell

Tungsten mono-carbide (WC) nanoparticles supported on multiwalled carbon nanotube (MWCNT) was synthesized by a microwave-assisted solid-state carburization. The prepared samples were used as a co-catalyst to prepare Pt-WC/MWCNT catalyst for a proton-exchange membrane fuel cell. MWCNTs with and without oxidative pretreatments were characterized as the starting precursors. The influence of the carbide formation conditions on the physicochemical characteristics of the final product were extensively investigated. According to the results, surface pretreatment of the MWCNTs can improve the yield of carbide formation. Furthermore, carburization process can improve the catalyst utilization due to increasing the number of surface defects of the MWCNT supporting materials which can be interpreted as structural effect of the carburization process. It is believed that the superior performance of electrodes modified with tungsten carbide is mostly due to the structural effect of the carburization process and synergistic effect between the electrocatalytic activity of WC and Pt.     

Optimisation of friction stir processing parameters to produce sound and fine grain layers in pure magnesium

The effects of friction stir processing (FSP) parameters such as rotational, traverse speeds and tool penetration depth on the formation of fine and defect free magnesium layers were investigated. The achieved microstructures were optically studied, and the microhardness profile of the optimised workpiece was measured. The results show that rotational and traverse speeds as well as their ratio play key roles in achieving a sound friction stir processed workpiece of pure Mg. In addition, at constant rotational and traverse speeds, when the penetration depth increases, the title angle must also increases in order to have a defect free workpiece. At optimum conditions, one pass FSP significantly refined the grain size from 3 mm in the as received magnesium to 14·6 μm in friction stir process layer. The microhardness of the fabricated layer reached to about 1·6 times that of the base metal.