The iron-carbon (Fe-C) micro-electrolysis was adopted to treat arsenic-containing wastewater from copper smelting, and the effects of processing parameters, including pH of inlet water, air blowing rate, contacting time, vibration frequency, solid-liquid ratio (mass ratio of Fe-C micro-electrolysis material to inlet water per minute), on the arsenic removal efficiency were explored. Results show that during the treatment by Fe-C micro-electrolysis, the generated oxides such as FeAsO₄, Fe₂O₃, and Fe₃O₄ are deposited on the surface of the Fe-C micro-electrolysis material, making passivation of the Fe-C micro-electrolysis material ineffective, thus resulting in poor arsenic removal efficiency. The use of vibration can effectively solve such problem. It is shown that after 90 d continuous treatment under the conditions, including pH of inlet water at 2.0, air blowing rate at 5 L/min, contacting time of 2 min, solid-liquid ratio of 2.5∶1, vibration frequency rate at 2 min every 4 h, the arsenic removal rate can be up to 99.99% and the arsenic content in water falls down to 0.033-0.036 mg/L, presenting a good and stable removal effect. It is concluded that this arsenic removal approach by adopting Fe-C micro-electrolysis can provide a new idea for treatment of arsenic-containing wastewater from copper smelting.

According to the existence of manganese, an experiment was carried out by adopting a processing technique consisting of reduction roasting and acid leaching to treat high-silicon manganese oxide ore. The effects of roasting temperature, roasting time, mass ratio of coal to ore, leaching temperature and time, initial sulfuric acid concentration, and liquid-solid ratio on the manganese leaching rate were all investigated. The results show that the leaching rate of manganese can reach 95.83% under the conditions including roasting temperature of 880 ℃, roasting time of 1.5 h, a mass ratio of 18% for coal to ore, leaching temperature of 55 ℃, leaching time of 2 h, initial sulfuric acid concentration of 1.80 mol/L, as well as liquid-solid ratio of 5 mL/g.

By adjusting the pH value of electrokinetic remediation cathode and adding enhancers, the total removal rate of Cr from the contaminated soil by electrokinetic remediation technology was increased. Then, the change of energy consumption and law of Cr migration and distribution during the electrokinetic remediation project were explored. The results show that EDTA, citric acid and hydrochloric acid can significantly enhance the total Cr removal rate during the electrokinetic remediation process. The total removal rates of Cr were 24.47% and 23.24% respectively after 7 days of electrokinetic remediation without adjusting the pH value of the cathode, by adding EDTA and citric acid into the soil. The pH value of the cathode isn't adjusted, which results in an obvious polarization effect. In contrast, the total removal rates of Cr were 44.20% (4.9 times as much as the blank) and 36.80%, respectively, after 7 days of electrokinetic remediation with the pH value of the cathode controlled, by adding hydrochloric acid and citric acid to the soil, respectively. Controlling the pH value of the cathode can effectively prevent the precipitation of Cr in the cathode region, thus enhancing the removal rate of Cr, but won't significantly increase the energy consumption of the electrokinetic remediation process. This method can greatly increase the total removal rate of Cr in contaminated soil by electrokinetic remediation, which is of significance in guiding the remediation of heavy metal contaminated soil.

Hydrothermal carbon generated by hydrothermal carbonization of waste jujube branches was activated with zinc chloride as an activator, and a kind of modified biochar was prepared with highly porous and aromatic structure on its surface, which was then used to adsorb Zn²⁺ in aqueous solution. It is shown that for the solution with pH of 9 and initial Zn²⁺ concentration of 30 mg/L, after 80 min adsorption at a temperature of 55 ℃ by adding 700 mg/L modified biochar, the removal rate of Zn²⁺ therein exceeds 99%. The adsorption process is well-fitted to the Freundlich adsorption model, indicating that the adsorption process with the modified biochar is a multilayer molecular adsorption. The removal rate of Zn²⁺ by the modified biochar, after 5 cycles of adsorption and desorption, can still remain over 97%.

The effect of laser remelting (LR) on the microstructure property and thermal stability of Ti-6Al-4V alloy prepared by laser powder bed fusion (LPBF) was investigated. The results show that after LR treatment, the thermal stability of the α′ phase within the LRed-Ti-6Al-4V titanium alloy samples is significantly improved, and the temperature at which β-Ti phase appears is up from 500 ℃ to 700 ℃. After heat treatment, the grains in LPBF-Ti-6Al-4V titanium alloy grow continuously, and obviously appear to be “short bar-like” and “coarse lamellar” at the temperature above 700 ℃; while the grains in the melting zone of the surface layer of the LRed-Ti-6Al-4V sample are still maintain equiaxial, and the relatively uniform and fine needle-like microstructure are observed in the melting zone and heat affected zone above 700 ℃. The surface microhardness of those two groups of samples decreases with the increased temperature, especially significant at 700 ℃ and 850 ℃ respectively. It is found that the rapid coarsening of β-Ti grains is the main reason for the falling down of hardness.

The surface of 38CrMoAl steel was processed by ion nitriding at 560 ℃ with the mixture of nitrogen and argon as nitrogen source. After that, the friction and wear property of 38CrMoAl steel was studied. The results show that as the N₂ volume fraction in the mixed gas increases, the thickness of nitrided layer increases, and the surface hardness of the nitrided layer increases first and then decreases. By adjusting the volume fraction of N₂ in the mixed gas, the number of active nitrogen atoms can be changed, thus leading to the change in the phase composition of the nitrided layer. With N₂ and Ar in a volume ratio of 2∶3, γ′-Fe₄N phase is the major phase and ε-Fe_2-3N phase is the minor phase in the nitrided sample. With N₂ and Ar in a volume ratio of 3∶2, the nitrided layer has ε-Fe_2-3N phase as the major phase andγ′-Fe₄N as the minor phase. Compared with the substrate material, the ion-nitrided sample has a smaller friction coefficient and higher wear-resistance. With N₂ and Ar in a volume ratio of 3∶2, the ion-nitrided sample has its compound layer in a thickness of 21.4 μm, and its average friction coefficient up to 0.26, presenting good wear resistance. The mechanisms of friction and wear include fatigue, abrasion and oxidation.

In order to improve surface hardness and corrosion resistance of 304 stainless steel, a medium-entropy alloy (CoCrNi) coating was prepared on the surface of 304 stainless steel by laser cladding, and phase composition, element distribution and corrosion resistance of the cladded coating were studied. The results show that the treatment has achieved good metallurgical bonding between the cladded CoCrNi coating and the substrate, with no cracks, pores and other defects. The cladded coating is composed of single FCC phase, and exhibits dendrite and inter-dendrite structure. The elements are uniformly distributed on the cladded coating without obvious segregation. The uniform distribution of Cr element plays a positive role in improving corrosion resistance of the coating. The CoCrNi coating has its polarization resistance (101.65 kΩ) higher than that of 304 substrate (90.56 kΩ), and also significantly higher corrosion resistance.

Based on the current situation and demand in the field of commercial aircraft engine bracket, analysis and review of research progress in magnesium alloy were presented in terms of formability, corrosion resistance and flame retardancy, and the prospects of applications of magnesium alloys in aircraft engine bracket were also discussed.

The effects of Zr content on solidification process of Al-Si-Mg-Mn alloy, and its microstructure and mechanical properties after aging treatment were investigated by means of numerical simulation, microstructure observation and mechanical property testing. The research results reveal that with increasing Zr content, the solidification path of the alloy become significantly different, and grains evolve from initial dendrites to equiaxed grains. After aging treatment at 175 ℃ for 7 h, an addition of Zr can significantly improve the hardness of the alloy. The addition of Zr promotes the precipitation of precipitates at lower aging temperature, which may be attributed to grain refinement of Zr, thus leading to improved diffusion efficiency. The main precipitates of the alloy are β″ phase and Q′ phase during peak aging.

Aiming at the shortcomings of single crystalline high-nickel ternary cathode material, including high residual alkali on the surface, poor cycle performance at high temperature, co-doping with niobium and yttrium was proposed to modify the cathode material for improving its electrochemical performance. With monocrystalline high-nickel ternary precursor (Ni_0.6Co_0.1Mn_0.3(OH)₂) as raw material, a series of cathode materials co-doped with two different elements were synthesized by high-temperature solid-state reaction. The results show that the niobium and yttrium co-doped sample presents excellent cycling stability and rate capability at high temperature. Compared to niobium-doped sample, it can have capacity retention rate higher by 2.58 percentage points after 50 cycles at 45 ℃, and discharge capacity higher by 6.2 mAh/g at 2C charge-discharge rate.