A hydrochloric acid leaching process was adopted to recover rare earth from rare earth polishing powder waste. The effects of hydrochloric acid concentration, leaching temperature, leaching time and liquid-solid ratio on the leaching rates of rare earth and main impurity Al₂O₃ were investigated, and the leaching mechanism was also discussed. It is found that the optimal conditions for single-stage leaching with HCl system are as follows: HCl concentration of 8 mol/L, leaching temperature of 80 ℃, leaching time of 3 h, and liquid-solid ratio of 4∶1. Under such conditions, the leaching rates of rare earth and Al₂O₃ are 90.81% and 43.68%, respectively．Based on the comparison of results from single-stage leaching, two-stage leaching and three-stage countercurrent leaching, it is shown that the leaching rate of rare earth by three-stage countercurrent leaching can be up to 98.38%. An increased amount of rare earth in the leaching solution is beneficial to the extraction and recovery of rare earth elements in the next step, thus greatly cutting recovery cost.

Three kinds of solid wastes including fly ash, carbide slag and refining slag were taken as raw materials for preparing a kind of absorbent by adopting microwave modification method and adjusting the proportions of three wastes. Fly ash was mixed with carbide slag in a mass ratio of 1∶1, and refining slag was modified by microwave (with microwave power of 200 W, time of 30 min), which was then added in quantities of 50% by total weight of fly ash and carbide slag. All mixed materials were then pressed under the pressure of 10 MPa, and the prepared adsorbent showed to have a good adsorption performance, with which the desulfurization rate and denitration rate for the sintering flue gas can reach 97.9% and 93.0%, respectively.

Based on the analysis of existence forms of molybdenum and iron ions in acidic solution with different pH, the solvent extraction processes available for separating molybdenum from iron were classified, for which the principles, effects, advantages and disadvantages were also discussed in detail. Moreover, the potential development trend of the solvent extraction for molybdenum and iron separation in the future is prospected, thus providing ideas for the research and development of a green and efficient process for separating molybdenum and iron from acidic solutions.

For the copper-containing acidic wastewater generated during underground mining process of a copper mine, a new processing technique consisting of copper recovery by replacement with iron filings, neutralization of alkaline tailings overflow, and treatment of coagulation and sedimentation was studied, and the effects of adding amount of iron filings, replacement reaction time and stirring speed on copper replacement rate were all investigated. And then, experiments on the proportion of required alkaline tailings overflow for neutralization of acidic wastewater and on toxicity characteristic leaching of neutralized sludge were performed, as well as the kinetics of replacement process was also studied. The results show that this new processing technique can produce sponge copper grading 35.6% Cu at 92.7% recovery, and the acidic wastewater after treatment can be up to the standard and directly discharged, with the cost of treatment agent at 0.95 yuan/t. Due to no hazardous waste generated, this processing technique can bring remarkable economic and environmental benefits.

A coating of 316L+x%NbC (x=0,5,10,15) was prepared on the surface of 304 stainless steel by laser cladding, and the effect of NbC content on the phase composition, microstructure, micro-hardness and wear behavior of the prepared coating was then investigated. The results show that with NbC content at 5%-15%, the phase composition of coating consists of NbC, Cr₇C₃ and γ-Fe; while the prepared 316L coating by adding NbC has its matric structure significantly refined, and traces of Nb element are dissolved in the phase of γ-Fe, forming a gap solid solution. By adding NbC, the micro-hardness and wear resistance of coating are substantially improved, but the friction coefficient and wear rate are remarkably decreased. It is shown that the coating of 316L+15%NbC has micro-hardness as high as 381HV_0.3, friction coefficient of 0.437 by average (41% lower than the coating 316L), and wear rate of 2.95×10⁶ μm³/ (N·m), (around 50% compared to 316L coating).

A kind of spherical Mn₃O₄ was prepared in situ with manganese sulfate solution as raw material and air as oxidant, and the effects of factors, such as time and temperature of reaction process, the pH value of solution and air flow rate, on the properties of synthesized product were investigated. It is found that under the appropriated conditions, including reaction time of 6 h and reaction temperature of 80 ℃, pH of 9 for the solution and air flow rate at 20 L/min, the synthesized Mn₃O₄ has a micro-morphology of regular nano-spherical particles in a uniform size around 150 nm, showing a high crystallinity and a good dispersion. Its specific surface area is 9.85 m²/g and the tap density is 1.93 g/cm³.

In order to improve the accuracy of flatness pattern recognition, a flatness pattern recognition method based on modified seagull optimization algorithm (MSOA) and Elman network is proposed. The weight threshold of Elman network is optimized with MSOA and then used for flatness pattern recognition. 20 sets of data are chosen for testing, and the obtained results are compared respectively with the flatness pattern recognition results based on BP neural network and traditional Elman network. It is found that algorithm method proposed in this paper has higher accuracy and better effect, with the mean square error lower than other algorithms by two orders of magnitude.

Polycrystalline Cubic boron nitride (PCBN) composites were synthesized by adding a certain amount of Al and Ti, with TiN as the main binder. The effects of temperature (1 300-1 600 ℃) on the composition, microstructure and mechanical properties of the PCBN composites sintered with TiN-Al-Ti in combination with CBN were investigated. It is found that the phases of PCBN specimen are mainly composed of BN, TiB₂, TiN and AlN, and almost all Ti reacts with CBN in the sintering process to form TiN and TiB₂ phases. The relative density, flexural strength and hardness of PCBN are generally trending up with the rising of sintering temperature. And composite material with good comprehensive performance can be obtained at a sintering temperature of 1 500 ℃, showing its relative density of 99.1%, flexural strength of 807.8 MPa, fracture toughness of 6.2 MPa·m^1/2, and micro-hardness of 3 233HV.

A₂B₇-type La_xY_3-xNi_9.7Mn_0.5Al_0.3 (x=0.2, 0.4, 0.6, 0.8, 1.0) hydrogen storage alloys with different La/Y ratios were prepared by vacuum melting. The effect of partial substitution of La by Y element on the structure and properties of the alloy was systematically investigated by using XRD, SEM, gas-phase PCT curves and electrochemical charge-discharge cycle curves. The experiment results show that the prepared alloy has Ce₂Ni₇ as its main phase and contains a small amount of Gd₂Co₇, PuNi₃ and LaNi₅ phases. The abundance of main Ce₂Ni₇ phase increases gradually with the increase of La/Y ratio. When the La/Y ratio is 1∶2, the LaY₂Ni_9.7Mn_0.5Al_0.3 alloy has the maximum hydrogen absorption capacity of 1.317%. After 150 charge-discharge cycles, the alloy can have its highest capacity retention rate at 54.2%.

The effect of rolling reduction on the microstructure, damping properties and mechanical properties of ZK60 magnesium alloy were studied. The results show that the damping properties of ZK60 magnesium alloy is improved with the increase of rolling reduction. When the strain amplitude is 0.01%, the Q^-1 value increases from 0.012 7 in as-cast state to 0.015 9 on rolling surface (RD-TD) with the rolling reduction of 50%, 0.020 4 on side section (RD-ND) and 0.018 3 on cross section (TD-ND). With the increase of rolling reduction, the (0002) basal texture strength of the alloy increases from 6.547 with the rolling reduction of 10% to 10.690 with the rolling reduction of 50%, which brings a certain impact to the damping properties of the alloy. The increased recrystallization volume fraction in the microstructure is the main influencing factor for the damping properties.