Huimin Meng

Energy-saving and environmentally friendly electrodeposition of γ-MnO2

The paper reports a new energy-saving and environmentally friendly method for synthesis of γ-MnO2 using a Pt/C gas diffusion electrode instead of the traditional cathode. The Pt/C gas diffusion electrode has high activity in a 120 g dm−3 MnSO4·H2O + 30 g dm−3 H2SO4 electrolyte at 80 °C. At the same time, the cell voltage and electrode potential of the electrolytic cell with the Pt/C gas diffusion electrode as cathode are measured at 100 A m−2 for 12 h. The results show that the Pt/C gas diffusion electrode demonstrated good stability. The effects of the current density on the synthesis of γ-MnO2 (EMD) is studied, and the results show that the electric energy consumption of the GDE as cathode drops 61.06–57.75%, 65.6–62.9% and 61.4–55% compared with that of the Cu, Graphite, and Pt cathode at 80 A m−2, 100 A m−2, and 120 A m−2 respectively in 12 hours. The γ-MnO2 (EMD) shows a better discharge performance as a cathode material of Zn–MnO2 than the commercial battery grade manganese dioxide.

Characterization and wear behavior of WC-0.8Co coating on cast steel rolls by electro-spark deposition

Abstract To prepare high wear resistance and high hardness coatings, electro-spark deposition was adopted for depositing an electrode of a mixture of 92wt%WC+8wt%Co on a cast steel roll substrate. The coating was characterized by classical X-ray diffractometer (XRD) and scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDX). The results indicate that the coating shows nanosized particulate structure and dendritic structure including columnar structure and equiaxed structure. The primary phases of the coating contain Fe3W3C, Co3W3C, Fe2C and Si2W. The coating has a low friction coefficient of 0.13, its average wear-resistance is 3.3 times that of the cast steel roll substrate and the main mechanism is abrasive wear. The maximum microhardness value of the coating is about 1573.9 Hv0.3. The study reveals that the electro-spark deposition process has the characteristic of better coating quality and the coating has higher wear resistance and hardness.

Crystallization behavior of plasma-sprayed lanthanide magnesium hexaaluminate coatings

LaMgAl11O19 thermal barrier coatings (TBCs) were prepared by atmospheric plasma spraying. The crystallization behavior of the coatings and the synthesis mechanism of LaMgAl11O19 powders were researched. The results showed that the plasma-sprayed coatings contained some amorphous phase, and LaMgAl11O19 powders were partially decomposed into Al2O3, LaAlO3, and MgAl2O4 in the plasma spraying process. The amorphous phase was recrystallized at a temperature of approximately 1174.9°C, at which level the decomposed Al2O3, LaAlO3, and MgAl2O4 reacted again. The resynthesis temperature of LaMgAl11O19 in the plasma-sprayed coatings was lower than that of LaMgAl11O19 in the original raw powders. The synthesis mechanism of LaMgAl11O19 powders can be summarized as follows: during the first part of the overall reaction, La2O3 reacts with Al2O3 to form LaAlO3 at approximately 900°C, and then LaAlO3 further reacts with Al2O3 and MgAl2O4 to produce LaMgAl11O19 at approximately 1200°C.

Corrosion resistance and adsorption behavior of bis-(γ-triethoxysilylpropyl)-tetrasulfide self-assembled membrane on 6061 aluminum alloy

A bis-(γ-triethoxysilylpropyl)-tetrasulfide (BTESPT) self-assembled membrane (SAM) was prepared by self-assembly membrane technology on 6061 aluminum alloy. The SAM was evaluated using electrochemical techniques (potentiodynamic polarization and electrochemical impedance) in 3.5 wt% NaCl solution. In addition, molecular dynamics calculations showed a high binding energy between the self-assembled molecule and aluminum alloy surface. The formation of the self-assembled molecule was believed to be achieved by a chemical bond between the silicon oxide group and the metal surface atoms. Finally, X-ray photoelectron spectroscopy and scanning electron microscopy were carried out to confirm that BTESPT could form a membrane on 6061 aluminum alloy.

Numerical Study on Fatigue Damage Properties of Cavitation Erosion for Rigid Metal Materials

Cavitation erosion is an especially destructive and complex phenomenon. To understand its basic mechanism, the fatigue process of materials during cavitation erosion was investigated by numerical simulation technology. The loading spectrum used was generated by a spark-discharged electrode. Initiation crack life and true stress amplitude was used to explain the cavitation failure period and damage mechanism. The computational results indicated that the components of different materials exhibited various fatigue lives under the same external conditions. When the groove depth was extended, the initiation crack life decreased rapidly, while the true stress amplitude was increased simultaneously. This gave an important explanation to the accelerating material loss rate during cavitation erosion. However, when the groove depth was fixed and the length varied, the fatigue life became complex, more fluctuant than that happened in depth. The results also indicate that the fatigue effect of cavitation plays an important role in contributing to the formation and propagation of characteristic pits.

Preparation of IrO2+MnO2 coating anodes and their application in NaClO production

Abstract To improve the durability as well as to reduce the cost of anodes, the IrO2+MnO2 composite coating anodes for NaClO production were prepared by thermal decomposition. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and X-ray diffraction analysis (XRD) were carried out to investigate the morphologies, element distribution, and microstructure. The anodic polarization curves were employed to study the effect of sintering temperature on the Cl2 evolution reaction (CER) of the electrodes. The accelerated life tests (ALT) and electrochemical impedance spectroscopy measurement (EIS) were utilized to investigate the stability. The rules of NaClO production were also studied by the static electrolysis experiment. The results indicate that sintering temperature has a significant influence on the CER properties as well as the ALT values of the electrodes. The electrode prepared at 400°C has the best CER properties and the longest ALT value.