A self-designed multi-functional rod was adopted to provide a real-time monitoring of surrounding rock stability during the excavation of a metal mine, and the variations of vertical stress of rock stratum and surrounding rock vibration occurrence within the monitoring range of the multi-functional rod during stoping were all recorded. It is found that the stress and peak ground velocity of the surrounding rock are all trending up as excavation area increases, which reflects that more fractures occur inside the surrounding rock, leading to lower degree of stability for the surrounding rock, and the excavation damage zone (EDZ) goes deeper. As for mines supported by top threaded anchor bolts, the EDZ evolution process and caving of rock mass can be more effectively controlled when the thread length of rod is greater than the depth of EDZ. After one month's mining of this stope, it is found that the vertical stress of the rock stratum within the monitoring length of the multifunctional rod increases by 3.9 MPa due to the subsidence of the stratum, and the frequency of vibration occurrence meets the blast vibration standard for safety permit in China. It is shown that the surrounding rock has a good stability based on the comprehensive evaluation.

A database including 336 sets of engineering practical samples was established for rockburst prediction based on literature research. An improved salp swarm algorithm (ISSA) was adopted to optimize the support vector machine (SVM), and then an ISSA-SVM model was constructed for predicting the rockburst intensity grade and its effectiveness was also verified. Results show that this ISSA-SVA model for rockburst prediction can have accuracy up to 94.0%, much higher than other model, which can provide a certain scientific basis for rockburst prevention and control.

The upper middle section in the West 2^#Mining Area of Jinchuan Longshou Mine, with the mining method changed from underhand cut-and-fill mining to sublevel caving without sill pillar, was taken as an example for studying extraction of the orebody in a confined space from sublevels of stope. A combined scheme was prepared with different ore-drawing method for each sublevel. As for the first and second sublevels, the total amount of mined ore in the ore drawing is controlled to ensure the safe caving of roof and forming of overburden. And ore drawing by controlling ore dilution is adopted for the third sublevel for avoiding ineffective dilution, so as to achieve high-quality ore recovery. For the fourth sublevel, a scheme of ore drawing by controlling ore dilution in the normal stope drift plus ore-drawing by controlling cutoff grade in an auxiliary extraction drift is designed to achieve a full and effective ore recovery. Experiments were then performed with three groups of different ore-drawing schemes, and results show that a combined ore-drawing scheme can achieve safe and effective mining of orebody in a confined space, but also has a significant advantage in controlling loss and dilution of ores, which can bring the mine good economic benefit from mining. It is concluded that this research can provide scientific theory and technical guidance for the following engineering practice.

For determining support parameters in an advancement project of the secondary shaft of Comica Mining's Kamoya copper-cobalt mine in the DRC, 25 sets of testing schemes were designed by using Box-Behnken based on the engineering geological conditions. After numerical analysis with FLAC^3D, the mechanical response characteristics under various support conditions were obtained. In combination with technical and economic requirement, analysis hierarchy process and principal component analysis were adopted for the combined weighting of nine selected indices, including advancement cost, maximum tensile stress among others, and then a comprehensive evaluating model was established for the parameters of shaft support. A multivariate second-order regression prediction equation was then obtained with the comprehensive scores as response indicators, and shaft support parameters as the variables. It is found that shaft is supported with 35 anchor bolts with thread length of 2.5 m arranged in horizontal direction, with spacing of 1 m in vertical direction, as well as the concrete lining with strength grade of C35, and the best comprehensive benefits can be obtained.

A core of uranium deposit was taken in an experiment of column leaching with alkaline solution (NaHCO₃+H₂O₂), and then the surface characteristics and pore distribution of sandstone-type uranium deposit were analyzed by using scanning electron microscope images. The variation in the microscopic pore structure of uranium-bearing sandstone in alkaline in situ leaching process was characterized by using T₂ spectrum of nuclear magnetic resonance (NMR). The results show that the matrix in the core firstly becomes connected pores due to chemical dissolution of leaching solution, resulting in more pore throats among large and small pores. The Al(OH)₃ mineral colloid and CaCO₃ generated by the reaction are deposited intensively in the pores and microcracks, which reduces the effective reaction area between leaching solution and matrix, thus reducing the uranium leaching efficiency. During the period of 97-158 h, dissolution is predominant, leading to the amount of chemical dissolution much higher than the amount of precipitation and accumulation, thus forming a large number of connected pores. Further reaction and dissolution of uranium minerals in the leaching solution can increase the recovery of uranium mineral to the peak.

With a transport roadway at+392 m section of №92 ore body in Tongkeng Mine as an example, the testing area was firstly divided for investigating the required on-site data. Then, the roadway roof rock was scored by using mining rock mass rating (MRMR) system for rock quality classification and rating. Finally, an appropriate support measure was proposed for the roadway roof based on the grading result. It is shown that the roof rock mass has its score of 50 by RMR system and is rated to be Grade Ⅲ. However, with the modified MRMR system, the rock mass has its score of 29 and is rated to be Grade IV. Compared with the on-site actual investigation of structural plane, the rating result by using MRMR system is much more consistent with actual situation.

By establishing a particle flow model of geological profile with discrete element software PFC^2D, the formation and development process of overlying strata cracks during the mining of ore body were studied, and the mechanism for overlying strata gradually developing into collapse and caving was also revealed. It is found that with the mining of ore bodies, fractures grow upward and increase in numbers. The goaf after mining can cause the overlying strata with tensile-shear failure, and also the new cracks will constantly occur in the strata. Tensile fractures predominantly develop in the overlying strata, but tensile fractures occur at the both ends of fracture development region. Also, more and more concentrated fractures grow upward at both ends of goaf, presenting a potential of gradual collapse and caving of goaf roof. After the third and fourth stratified ore bodies are mined out, roof collapse will take place locally and then gradually develop into roof caving of the whole goaf, finally leading to roof collapse to the surface and forming a small sinkhole on the ground surface. Then, the development progress of sinkholes can be subdivided into stable stage, slow-progress stage, rapid-progress stage and end of progress in terms of the numbers of fractures, presenting the mechanism for overlying strata developing from tensile fracture and shear fractures at both ends of goaf to overall collapse.

In order to study the energy distribution of blast wave propagation, the EEMD and Hilbert transform techniques were adopted to analyze the blast vibration signals at the same measuring point in different directions, on the same line with different distance away from explosion center, as well as with the same distance away from explosion center but with different maximum charges. It is found that vertical signal energy is mainly concentrated in the midbands, while the radial signal energy in horizontal direction is distributed in both the mid- and low-bands, and tangential signal energy in the horizontal direction is mainly concentrated in the high-bands. Under the same monitoring, a greater attenuation is found in high frequency energy and the proportion of signal energy distribution shifts from high-bands to low-bands as the distance is farther away from the explosion center. However, with the same distance away from the explosion center, increasing the maximum charge in a single stage can lead to higher proportion of low frequency energy, and significantly increased charge can bring more obvious effect.

The progress in the research of micro-fine mineral flotation process is reviewed in terms of grinding, pulping, separation, and finally a prospect for the research direction of micro-fine mineral flotation process is presented.

Pure quartz and pyrite minerals in the size range of 5-30 μm were taken in an experiment on viscosity under different pulp temperature and concentration conditions, for investigating the viscosity variation law of ultrafine particles. The results show that the viscosity for both minerals within the same size range increases along with the increase of pulp concentration, and the finer the particle, the greater the increasing rate. Furthermore, the viscosity variation of quartz is more remarkable．With the same pulp concentration, the viscosity of both minerals displays a declining-ascending trend as the temperature rises, which is more significant for finer minerals. The regression analysis shows that the correlation between viscosity and concentration of quartz and pyrite slurry are in line with the exponential fitting model. According to this analysis, the pulp concentration for ultrafine grinding should not exceed 40% and the optimum pulp temperature should be regulated at 50 ℃, which is beneficial for improving grinding efficiency.

The influence of Ce³⁺ in the sodium oleate system on the flotation of fluorite and calcite was investigated by flotation test, zeta potential measurement, solution chemistry study and X-ray photoelectron spectroscopy analysis. The results reveal that in the sodium oleate system, Ce³⁺ with a low concentration exists on fluorite surface in the form of CeF₃·0.5H₂O(s) under acidic and neutral conditions, therewith, fluorite can be activated to generate more active sites for the adsorption of sodium oleate. Meanwhile, Ce³⁺ can be adsorbed onto calcite in the form of Ce₂ (CO₃)₃·8H₂O(s). There are more active sites generated as well, but calcite may be depressed as the hydrophilic nature of Ce₂ (CO₃)₃·8H₂O(s) and the spatial site barrier effect of crystalline water hinder the adsorption of sodium oleate. In alkaline pulp, Ce³⁺ is mostly precipitated to form Ce(OH)₃(s) and depresses both fluorite and calcite as Ce(OH)₃ (s) can consume sodium oleate and reduce its adsorption on both minerals.

Aiming at the commercial production problems in the usage of high-temperature reagents for the reverse flotation in Qidashan Concentrator, a new laboratory-prepared combined collector (AG-1) was adopted in the reverse flotation of mixed magnetic concentrate at room temperature (20 ℃). The results show that a reverse flotation flowsheet consisting of one stage of roughing, one stage of cleaning and three stages of scavenging, with pulp pH of 11.5, the dosages for depressant (corn starch), activator (CaO) and collector (AG-1) at amount of 950 g/t.100 g/t and 750 g/t, respectively, can yield an iron concentrate grading 68.13% TFe at 88.43% recovery. XRD patterns and optical microscopy visualization of flotation concentrate and tailings show that AG-1 has good selectivity, and can effectively separate valuable minerals from gangue mineral of quartz. Compared with the single collector of sodium oleate or dodecylamine, AG-1 possesses a lower surface tension and a stronger ability in reducing the surface tension of gas-liquid interface, which can better improve mineral hydrophobicity.

A flotation experiment was performed with medium grade siliceous and calcareous collophanite from Guizhou Province for determining the optimum technical process and reagent system. With the process flow consisting of three roughing, one cleaning and one scavenging, a high quality phosphate concentrate grading 34.07% P₂O₅ at 75.38% recovery was finally obtained. The adsorption behavior of collector SGC-01 on the apatite surface during the direct flotation process was also investigated by using Zeta potential, infrared spectrum and QCM-D. The results show that SGC-01 can be chemically adsorbed onto apatite in various forms, and presents a better flotation performance compared with sodium oleate.

By performing settling rate test, turbidity test, zeta potential measurements, solution chemistry study and extended DLVO theoretical analysis, the mechanism for sodium hexametaphosphate (SHMP) to disperse ultrafine potassium feldspar and hematite was investigated. It is shown that, Na_m (PO_3)n^m-n (m<n) anions derived from SHMP ionization can wrap around mineral grains in a form of spiral long-chain polymers, forming thick hydrophilic macromolecule protective films. Meanwhile, HPO₄^2-formed by hydrolysis can be adsorbed onto ore grains, leading to decrease of the surface potential and increase of the interparticle electrostatic and steric repulsions. In this case, mineral particles need to overcome a higher potential barrier to reach a stable condensed state. Therewith, the non-selective agglomeration of ore particles weakens, resulting in a significant improvement in dispersion stability.

The adsorption of phosphate ions and oleate ions onto CO₃^2- defects on dolomite (104) surface was studied by using density functional theory (DFT) calculation. The results showed that the CO₃^2- defects that were generated due to dolomite dissolution led to the enhancement of the activity of metal atoms on the surface, which was beneficial to the interaction between anions and mineral surface. The adsorption energies of H₂PO₄^- onto calcium atoms on the ideal dolomite surface and the defective dolomite surface were calculated to be -183.30 kJ/mol and -561.24 kJ/mol, respectively. Based on the calculation of density of states, it was found that after adsorption of H₂PO₄^- onto the calcium atoms on the surface of defective dolomite, the adjacent magnesium atoms still had strong activity, and the adsorption energies of oleate ions onto the magnesium atoms on the surfaces of the ideal dolomite and defective dolomite were -52.29 kJ/mol and -489.43 kJ/mol, respectively. Phosphoric acid ions and oleic acid ions were adsorbed together on the surface of dolomite, resulting in the floating of dolomite.

An experimental study was carried out to comprehensively recover lead and zinc resources from a refractory pyrrhotite lead-zinc sulfide ore grading 1.84% Pb and 4.53% Zn respectively. And a new ester collector of ZQ-11, in combination with 25^# dithiophosphate, was used to float lead minerals. After that, magnetic separation process was adopted to treat lead flotation tailings for desulfurization, and butyl xanthate was then used to collect zinc minerals from the desulfurized tailings. A closed-circuit test resulted in 89.49% Pb recovery into a lead concentrate grading 62.57% Pb and 3.30% Zn respectively, and 85.79% Zn recovery into a zinc concentrate grading 43.37% Zn and 1.01% Pb respectively. It is concluded that this process can actualize an effective recycle of refractory pyrrhotite-type lead-zinc sulfide ore.

A process consisting of flocculation-sedimentation and chemical decalcification was adopted to treat mineral processing wastewater of a tungsten polymetallic ore with high suspended solid (SS) and Ca²⁺contents. The influence of flocculant dosage, stirring time, stirring speed, water temperature and pH value on flocculation-sedimentation performance was investigated, and the process was then optimized. A closed-circuit test of fluorite flotation with the recycled water shows that the flotation index obtained is similar to that using fresh water, indicating that the wastewater after treatment is applicable for fluorite flotation.

To improve the copper flotation indices of a large copper-molybdenum mine, experimental studies on reagent regime and beneficiation process were carried out, and the influences of collector type and dosage, scrubbing and desliming parameters on flotation indices were investigated. The results of a closed-circuit test of copper flotation show that a copper concentrate with Cu grade of 23.22% can be obtained at 89.10% recovery under the optimal reagent system and renewed process conditions.

For solving the problems of coarse feed size for grinding and high energy consumption in processing Daye Iron Ore, an experiment was carried out with high pressure roller grinding (HPRG) to mill the fine crushing products. The parameters of pressure between rollers, the water content of feed and the rotational speed at roller surface were optimized correspondingly as 10 MPa, 2% and 0.26 m/s. A closed-circuit test shows that HPRG can obviously reduce grinding energy consumption and improve mineral liberation degree. Jaw crushing and HPRG products were then taken as the feed for grinding-flotation test and it is shown that HPRG can improve flotation recovery, with recoveries of Cu, Fe and S all up by 2.56, 1.93 and 1.44 percentage points, respectively.

A kind of refractory hematite-limonite ore containing 0.39% lead, 0.30% zinc and 47.04% TFe was taken to perform carbothermic reduction roasting experiment, and the reduction effect of hematite-limonite ore and the removal rate of lead and zinc in the reduction roasting process were all investigated. The reaction fraction, reaction rate and kinetic parameters of the reduction roasting process were studied by means of thermogravimetric analysis at a constant temperature, and the kinetics of carbothermic reduction roasting of refractory hematite-limonite ore was also discussed. After 60-min roasting at 1 200 ℃ with the reducing agents of carbon and oxygen at a ratio of 2.25, the obtained roasted ore was subjected to low intensity magnetic separation, resulting in the yielded iron concentrate grading 89.63% TFe at 86.09% recovery and the removal rates of lead and zinc up to 98.97% and 91.19%, respectively. The iron minerals are mainly transformed into spherical metallic iron particles with iron purity over 99.4% in micro-zone. The reduction roasting process of iron ore follows the shrinkage boundary control reaction mechanism and shrinkage core model. The apparent activation energy is calculated to be 91.37 kJ/mol, and the pre-exponential factor is calculated to be 18.09 min^-1, indicating that the rate-limiting reaction step is solid-state diffusion. This research can provide reference for removing harmful impurities from similar ores by reduction roasting process.

In order to investigate the influence of additive on iron recovery from red mud by using a process consisting of magnetizing roasting and low intensity magnetic separation, a kind of red mud containing high content of iron and aluminum was taken for experiments. It is found that addition of dolomite and phosphogypsum won't bring any effect to iron recovery, but sodium sulfate can bring an obvious activation effect. In the experiment, the roasting process ran at 650 ℃ for 90 min, with the addition of sodium sulfate at an amount of 10%, with total gas flow at a rate of 500 mL/min and CO at a volume fraction of 30%. And then, the obtained calcine, after being ground to a fineness of -0.045 mm 65%, was subjected to a magnetic separation with magnetic intensity of 68.8 kA/m, yielding an iron concentrate with 60.65% TFe grade at 94.01% recovery. The subsequent thermodynamic analysis showed that at the temperature within the tested range, both dolomite and phosphogypsum were conducive to the decomposition of iron olivine rather than iron spinel, while sodium sulfate could work for both.

The impurities of iron and cobalt in nickel sulfate mixture solution were removed by oxidation with chlorine, and the varying pattern for the potential of metal ions and pH value during the chlorine oxidation was investigated. Based on the thermodynamic analysis, the proper potential range for removing iron and cobalt was determined. Meanwhile, the effects of pH value, temperature among other factors on impurity removal were also investigated. Results show that the reaction temperature has little influence on the removal effect of iron and cobalt, but pH value can bring great impact. It is found that under the following optimal conditions, including reaction at 50 ℃ for 140 min, agitation at a rate of 400 r/min, pH value initially at 1.6 and maximally at 4.0-4.5, potential controlled within the range of 0.62-0.64 V for the stage of iron removal and at 1.08 V for the stage of cobalt removal, the content of iron and cobalt in the solution of nickel sulfate mixture can be reduced to less than 0.4 mg/L and 1 mg/L, respectively. It indicates that the removal rates of iron and cobalt approach 100%, meeting the requirement in the actual production of a domestic company (with iron content less than 1 mg/L and cobalt content less than 2 mg/L). Furthermore, the loss of nickel in this removal process is around 0.5%.

The sulfur-containing cyanide leaching tails were taken for experimental research by using pyrolysis process in a rotary kiln for degradation to remove cyanide as well as sulfur fixation. The influence of temperature, atmosphere, shielding gas flow rate, and the time of constant temperature for pyrolysis process on the degradation effect were all investigated. After experiment, soil testing was performed to detest the toxicity of the leaching tails for determine the effect of the clean treatment. It is found that under the atmosphere of 95%N₂, after 2 hours pyrolysis at a constant temperature with the highest temperature at 500 ℃, the total cyanide content in the tails detected by soil testing is less than 0.04 mg/kg, showing the content of total cyanide, copper, lead and zinc after cyanide leaching all can meet the relevant requirements for class I general solid waste in GB 18599-2020. The sulfur fixation rate in the left slag is approaching 100% after pyrolysis, and there is no large amount of SO₂ in the flue gas during pyrolysis. It is concluded that clean treatment of cyanidation tails can be actualized by using this low-temperature pyrolysis process.

Arsenic-iron slag were treated by using magnetizing reduction for recovering arsenic and iron therein, and the experimental conditions were optimized as follows: roasting at 650 ℃ for 180 min, adding carbon at an amount of 25% and protecting with argon. Under such conditions, the arsenic volatilization rate reached 97.25% and arsenic content in the roasted slag decreased to 0.61%. It is found that arsenic can be recovered in the form of As₂O₃, with purity up to 99.13%, while iron therein is magnetized and can be recovered in the form of Fe₃O₄ by magnetic separation. Therefore, this process can actualize the resource utilization of arsenic-iron slag.

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.

In order to understand carbon performance of the mining sector in Hunan Province, the carbon emissions and carbon performance of the mining sector in Hunan Province were calculated based on the latest statistical data of national economic accounting, and factors influencing carbon performance were analyzed based on the established model. It is shown that the carbon performance of Hunan's mining sector was at a relatively low level from 2010 to 2020, and there was great difference in carbon performance of sub-sectors. Factors of asset size and energy efficiency had a positive impact on carbon performance, while factors of asset liability ratio and energy structure had negative constraints on carbon performance. Achieving economies of scale, improving energy efficiency, optimizing energy structure and maintaining a stable liabilities-to-assets ratio made sub-sectors of non-ferrous metal and gas production and supply in the front rank in terms of carbon performance. However, decreasing returns of scale in sub-sectors of coal mining and washing, as well as unreasonable energy structure and low energy efficiency in coal sub-sector led to the carbon performance of coal sub-sector ranking at the bottom. Consequently, it is suggested that the mining sector in Hunan Province should optimize its energy structure, accelerate low-carbon innovation, and increase various energy efficiency, so as to improve their carbon performance.

In order to explore the current status of sustainable development of mining enterprises in China in recent years, static and dynamic analysis was performed for ecological efficiency of mining enterprises in 11 different sub-sectors in China from 2012 to 2020, in which SBM-DEA model with undesirable output taken into consideration was adopted in combination with GML index. And regression testing was also conducted in combination with Tobit model for the influencing factors for ecological efficiency. Results show that during the sampling period, the ecological efficiency of mining enterprises was generally trending up, but there was some difference in the efficient frontier, and great difference between each sub-sector. It is found that the technological advancement is the main driving factor for improving ecological efficiency, which is also positively correlated with high degree of interaction with outside world, but negatively correlated with environmental regulations. At last, as for improving ecological efficiency of mining enterprises, some recommendations are proposed for the state, mining sector and mining enterprises.