The impact of large-diameter pressure-relief borehole arrangement and drilling parameters on roadway stability was studied. It is found that arrangement of boreholes in a two-row pattern, compared to boreholes in a single-row pattern, can benefit stress shift and control of roadway deformation. By adopting the arrangement of boreholes in a single-row pattern and a two-row pattern, the deformation at both sides was reduced by 6.05% and 15.44% respectively, and the original maximum stress was reduced from 39.61 MPa to 33.50 MPa and 32.70 MPa respectively. It is also found that boreholes should be arranged, as much as possible, near the center of two sides, penetrating the plastic zone to the place with the maximum stress. And the spacing between boreholes should be determined based on the horizontal distance of the plastic zone of boreholes, and the burden spacing should be less than the height of stress-relaxed zone.

The west slope of SCM copper cobalt mine in DRC was taken as an example for determining the shear strength parameters of rock mass by a laboratory triaxial compression test, back analysis of landslides, evaluation of rock mass quality and strength conversion with Hoek-Brown criterion, and then the obtained strength parameters were verified. The results show that due to the size effect of the samples, there may be deviation in the cohesion of rock mass shear strength obtained from the laboratory triaxial compression tests. It is found that with the obtained parameters used in slope stability analysis, more accurate evaluation results can be obtained from the slope model with higher sensitivity to friction angle, while lower accuracy from the slope model with higher sensitivity to cohesion. Under the same working condition, the parameters of slope rock mass obtained from the back analysis of shallow landslides can be used for analyzing local or single bench stability, and the parameters of slope rock mass from back analysis of deep-seated landslides or the landslides due to weak structural planes can be used for overall stability analysis. It is found that the shear strength parameters obtained based on Hoek-Brown failure criterion are close to the results from laboratory triaxial compression test, also easy to operate and more accurate, which can have a wide application.

Guizhou Jinfeng Gold Mine was taken as an engineering example for investigating effect of geometric features of rock surface on the performance of shotcrete support in the roadway constructed by drilling and blasting. The rock surface of the roadway was scanned by using a 3D laser scanner, and a 3D geometric model was established for the roadway. The actual shape of cross-sections was created by slicing the geometric model with a 3D software for analyzing the geometric features. With numerical models respectively established for the designed and actual sections, the variation in internal forces of the shotcrete and its supporting effect for the surrounding rock were analyzed. The results show that uneven rock surface of a roadway can lead to significant increase in the shear force and bending moment of shotcrete, but relatively small effect on the axial force. It is found that concave part of surrounding rock in a roadway is subjected to maximum negative bending moment, while convex part is mostly subjected to maximum positive bending moment. Under the interaction of axial force and bending moment, the shotcrete on convex part has an obvious lower safety factor, leading to weakened support to the surrounding rock, thus tensile failure is prone to occur.

The concentration of plume caused by hydraulic collecting system during deep-sea polymetallic nodules mining under different working conditions were analyzed. Test results show that the concentration of discharged plume from conveying system is much higher than that of sediment plume caused by the disturbance of capture system, which is one of the main causes of turbidity current in the sea. In the test, the curve of slurry concentration presented a steep upward trend line followed by a steep downward line. Increasing oil pressure of the pump of capture system will lead to higher concentration of slurry. However, the oil pressure of the pump of conveying system won't result in obvious variation in slurry concentration.

In order to explore disturbance of seabed sediment during mining of polymetallic nodules, a pool experiment was carried out to scour sediment by a waterjet from polymetallic nodules collector. Variation of gully depth, and migration and diffusion regulation of sediments were investigated in the experiment by setting the waterjet at different speed, with nozzle at different height from sediment, and collector at different traveling speed. The results show that the collecting process of polymetallic nodules brings scour to both particles and blocks of sediment, leading to uneven surface of the gully. Then, disturbed sediment migrates and diffuses through upper plume flow and bottom gravity flow.

Microseismic signals collected during roadway construction in Jinfeng Gold Mine in the southwest Guizhou Province are non-stationary and also contaminated with background noise. For solving this problem, a noise reduction method based on the improved complete ensemble empirical mode decomposition with adaptive noise (ICEEMDAN) combined with blind source separation (BSS) was proposed. With this method, a microseismic signal can be preliminarily decomposed by ICEEMDAN algorithm, and then correlation coefficient and marginal spectrum of signal can be calculated with MATLAB. Components of noise-containing mode and main frequency of signal can be filtered, and FastICA algorithm is finally used for BSS to achieve noise reduction. The practical application in mine shows that compared to empirical mode decomposition (EMD) and traditional wavelet packet threshold method, the proposed method, with higher signal-to-noise ratio (24.142 5 dB), can bring better noise reduction effect with smaller standard error (0.012 18).

In consideration of safety problem of landfilling into a dump with inclined foundation in an open-pit mine, an inclined foundation model and an anti-slide coal pillar model were established based on the analysis of landfilling methods in such inclined dump, deformation characteristics and sliding mode of inclined foundation, and then the method for evaluating stability of anti-slide coal pillar and influencing factors of the stability coefficient of dump slope were all discussed. The research results show that the stability of anti-slide coal pillar mainly depends on the relationship between the internal friction angle of coal pillar and the rest angle of waste material. When the internal friction angle is greater than or equal to the rest angle, the stability coefficient of dump slope increases with an increase in the length of anti-slide coal pillar; while when the internal friction angle is less than the rest angle, the stability coefficient of dump slope increases first, then falls down and finally increases again as anti-slide coal pillar becomes longer.

In view of the data of ground-based SAR presenting high oscillation and high fluctuation with less obvious characteristic trend, an approach for early warning and prediction of slope deformation by using velocity reciprocity was proposed, which adopts a data processing method of subtracting dislocations and deleting limits to optimize the quality of deformation data, thus the accuracy of early warning and timely prediction of landslide can be improved. The application of this approach in an iron mine in Inner Mongolia shows that not only those problems faced in the actual actuation can be solved, but also the data about disaster approaching can present obvious deformation rule. It is concluded that this early warming and prediction approach has a wide application.

In order to find a more accurate and efficient way to measure volume of explosion-produced craters, the traditional method by using a reference plane with a vertical section was improved. Taking the crater produced by single-hole blasting of the deep orebody in Gaofeng Mine as an example, the measurement result by using 3D laser scanning was compared to that by using a reference plane with a vertical section. It is found that 3D laser scanning measurement is superior in terms of accuracy, efficiency and measuring operability. This research can provide a new idea for accurately measuring the volume of explosion-produced craters.

The motion of spherical, tetrahedral and hexahedral particles flowing in a vertical pipe under different working conditions was simulated by using computational fluid dynamics-discrete element method (CFD-DEM), and the motion of irregular particles flowing in a vertical pipe was obtained. Based on comparison of local concentration and local flow rate, it is found that with lower flow rate at the inlet, the shape of particles can bring a larger influence to local concentration; while with a higher feed concentration and lower inlet flow rate, the shape of particles can bring obvious influence to local flow rate.

Response surface methodology (RSM) was used to optimize the flocculation settlement parameters of fine iron tailings slurry. According to the Box-Behnken test method in Design-Expert 8.0 software, a three-factor and three-level test was designed to obtain a regression equation of turbidity model for flocculation settlement of fine-grained iron tailings slurry. The results show that with the following favorable flocculation settlement parameters, including addition of inorganic flocculant FeCl₃ at an amount of 113.44 mg/L, organic flocculant PAM at an amount of 0.61 mg/L and stirring speed of 440.57 r/min, the slurry turbidity is predicted to be 11.45NTU, while the measured value is 12.38NTU, indicating that the model has a good accuracy with a small error. Based on the model variance analysis, reliability analysis and factor interaction analysis, it can be verified that RSM is reasonable and feasible to be used for optimizing the flocculation settlement parameters of fine iron tailings slurry, which can provide theoretical basis for its efficient treatment.

A technique featuring separated treatment and recycling was introduced to process a mineral processing wastewater from a tungsten-copper ore concentrator. The wastewater from copper tailings precipitation and copper concentrate filtration is recycled for copper flotation, while the water from tungsten concentrate filtration is returned to the cleaning stage in tungsten flotation. They all can meet the water quality requirement in beneficiation. Tungsten tailings water can be reused in grinding and tungsten flotation after intensified treatment by lime flocculation and Fenton oxidation processes. In a close-circuit test, each type of wastewater from different beneficiation processes was separately returned to the corresponding stages based on its quality, and the obtained technical indicators were equivalent to those from the tests with fresh water.

The interaction mechanism of kyanite group minerals and quartz in cationic flotation system was studied by using an extended DLVO (EDLVO) theory combined with microscopy analysis. The results show that, under conditions including pH value of 8, FeCl₃·6H₂O dosage of 30 mg/L and dodecylamine dosage of 80 mg/L, there is interaction between quartz and kyanite group minerals in various size fraction, and the adhesive coating among particles is one of the main reasons for the interaction between kyanite group minerals and quartz amidst flotation process. Besides, the adsorption force between kyanite group minerals and quartz is in the following descending order：andalusite/quartz ≥kyanite/quartz ≥ sillimanite/quartz, indicating that it is relatively difficult for andalusite to be separated from quartz by flotation.

Natural chalcopyrite (CuFeS₂) was used as a catalyst to activate persulfate (PS) for butyl xanthate wastewater treatment. The influences of CuFeS₂ dosage, PS dosage and initial pH of solution on the removal rate of butyl xanthate in CuFeS₂/PS system were investigated, and the recyclability of CuFeS₂ was also evaluated. The results show that CuFeS₂ can significantly activate PS. After 10 min reaction with initial pH of 3, CuFeS₂ dosage of 4 g/L and PS dosage of 5 mmol/L, the removal rate of butyl xanthate reached 99.23%, while the removal rate of total organic carbon (TOC) was only 31.29%. After the reaction time was extended to 60 min, the TOC removal rate reached 68.31%, and CuFeS₂ still sustained good catalytic activity after being recycled for five times. The UV-Visible absorption spectra of butyl xanthate wastewater degradation showed that butyl xanthate was initially oxidized to alcohols, then decomposed and mineralized to carbon dioxide and water. X-ray diffraction and fourier transform infra-red spectroscopy analysis showed that CuFeS₂ reacted with PS without surface passivation, thus could be reused. A free radical quenching test and an electron spin resonance analysis showed that the removal mechanism of xanthate included free radical degradation and CuFeS₂ physisorption, in which sulfate radical (SO₄^-·) and hydroxyl radical (HO·) were the main active substances to promote xanthate degradation, and the SO₄^-· played a dominant role.

A kind of ore from Inner Mongolia containing 1.89% Pb, 1.84% Zn and 125 g/t Ag was taken in a flotation experiment for recovering the valuable elements therein. From the process mineralogy study, it is found that the Pb and Zn therein exist mainly in the form of galena and sphalerite, while Ag is in the form of freibergite. A preferential flotation process was adopted for treating this ore, in which zinc sulfate and sodium sulfite were taken as sphalerite depressants, propyl xanthate, ammonium dibutyl dithiophosphate and 25^# dithiophosphate were taken as the collector for lead flotation, and then copper sulfate was taken as the activator and butyl xanthate was taken as the collector for zinc flotation from the tailings of lead flotation. A lead concentrate grading 52.71% Pb, 2.29% Zn, containing 3 182.00 g/t Ag was produced at 94.22% Pb recovery and 82.00% Ag recovery, and a zinc concentrate grading 46.11% Zn, 0.76% Pb, containing 255 g/t Ag was also yielded at 87.31% Zn recovery and 6.78% Ag recovery, showing that silver was mainly pulled into lead concentrate. It is concluded that this processing technique can bring not only a good Pb/Zn separation effect, but also an effective recovery of Ag.

Based on the study of process mineralogical properties and grindability of an iron ore from Australia, experiments were carried out to explore its beneficiability. The results show that this kind of ore has a TFe grade of 34.90%, with magnetite and hematite as the dominant Fe-containing minerals, and quartz as its dominant gangue mineral. The ore is medium hard, with a protodyakonov coefficient of 3.13, and also comparatively hard to mill, with a Bond ball milling work index of 13.27 kW·h/t. On this basis, a flowsheet consisting of sequentially primary grinding, a roughing process of low-intensity magnetic separation (LIMS), secondary grinding and a cleaning process of LIMS was adopted in an experiment, producing an iron concentrate grading 65.45% TFe at 65.98% recovery, with mFe recovery of 95.69%. After intensified grinding, the iron concentrate was subjected to further magnetic separation, resulting in ultrapure iron concentrate grading 71.90% TFe at 60.20% recovery. Meanwhile, the middlings was subjected to a scavenging, and a super-high grade iron concentrate with TFe grade of 69.87% was obtained with recovery of 35.21%, indicating that this ore has a good beneficiability.

An accumulative bauxite ore in Yunnan containing 42.13% Al₂O₃, 15.73% SiO₂ and 17.44% TFe, namely, with an Al/Si ratio of 2.68, was taken in a flotation for Al/Si separation, and the effects of pH regulator dosage, type and dosage of depressant, collector dosage and grinding fineness on desilication performance of flotation were all investigated. A closed-circuit flotation test performed with the optimized parameters produced an aluminum concentrate with Al₂O₃ grade and recovery of 52.16% and 70.30%, Al/Si ratio of 7.69, and TFe grade of 20.89%, respectively. Then, a flowsheet consisting of magnetic roasting and magnetic separation was introduced to treat this aluminum concentrate for Al/Fe separation, which produced a final aluminum concentrate containing 69.34% Al₂O₃ with Al/Si ratio of 8.70, and a rough iron concentrate grading 52.34% TFe with a process recovery of 76.03%.

A lead-zinc deposit is rich in valuable metals of gold and silver. In order to improve the economic benefits of products, the associated gold and silver should be enriched in lead concentrate to the maximum extent. Based on the actual situation in the production, the distribution of associated gold and silver in the products after mineral processing was ascertained, and then optimization tests were perform. The results showed that most of the associated gold and silver were concentrated in the lead concentrate, and the recovery of gold and silver was positively correlated with the recovery of lead. Without altering the original reagent regime for lead flotation, ethyl xanthate was introduced as an auxiliary collector in a close-circuit test adopting a flowsheet consisting of one stage of roughing, two stages of cleaning and two stages of scavenging. And the obtained lead concentrate with grade around 50% can have a high enrichment of gold and silver and a low content of zinc. It is concluded that gold and silver resources can be comprehensively recovered, which can bring in the maximized economic benefit.

The fine slime collected from the flotation overflow in a titanium concentrator located at Panzhihua-Xichang region, with fineness of－0.025 mm 78.10% and TiO₂ grade of 8.33%, was taken as the raw material for study. Based on the characteristics of this slime, a pre-enrichment process was adopted for impurity removal in an experiment, and CC, a new type of dispersant with good selectivity, was used in the following flotation. An ilmenite concentrate was obtained grading 47.97% TiO₂ at 73.09% recovery, indicating the titanium resources in the slime can be reclaimed.

In the actual production, not only the copper oxide ore has a high content of slime, but also the copper minerals therein are prone to be lost during the beneficiation. In consideration of these problems, a cyclone desliming system was added to process the tailings after the copper sulfide was preferentially floated. The industrial experiment results show that a copper oxide concentrate grading 19.20% Cu can be obtained with the process recovery of 76.24% by adopting a direct sulphidizing flotation process to reclaim copper oxide minerals from copper sulfide flotation tailings, and the copper grade of tailings can be reduced to 0.94%. After copper sulfide flotation tailings were deslimed by cyclone, a process consisting of flotation of copper oxide minerals from underflow and a wet leaching to recover copper resource from fine slime (overflow) was adopted, resulting in a comprehensive copper oxide concentrate with Cu grade of 24.63% and process recovery of 85.55%, and the final tailings with Cu grade reduced to 0.60%. The indices of the copper oxide concentrate from the flowsheet containing cyclone desliming process are obviously superior to those by direct sulphidizing flotation process. Besides, this flow is relatively simple with reduced unit consumption of reagent for copper oxide flotation.

The amphibolite-type magnetite ore in Yuanjiacun Iron Mine was processed adopting a processing technique consisting of high pressure grinding roll (HPGR) plus pre-concentration, followed by staged grinding and staged separation process. In order to reduce the grinding feed in the following concentration, HPGR was introduced for superfine crushing, and the obtained material in a size fraction of－3 mm was treated by a wet pre-concentration process, yielding 22% coarse tailings for discarding. And then a pre-concentration process resulted in the obtained concentrate with TFe grade up to around 36%. The work index for grinding before and after adopting HPGR was reduced from 11.91 kW·h/t to 11.11 kW·h/t. An experiment was performed with a flowsheet of HPGR plus pre-concentration followed by staged grinding and staged separation process, yielding 33.92% concentrate grading 67.13% TFe at 75.75% recovery, showing the ratio of concentration down to 2.27 from 2.95. It is concluded that the above-mentioned processing technique can provide an energy-conservation and consumption-reduction solution for large-scale and low-cost exploitation of similar low-grade magnetite mines.

A flowsheet consisting of pre-reduction magnetic roasting and magnetic separation was introduced to process a refractory weakly-magnetic iron ore from Jiangsu Province. The results show that after 60 min roasting at 750 ℃ by adding coal as a reducing agent at an amount of 3%, the pre-reduced iron ore was ground to a fineness of 75% -0.074 mm and then subjected to low intensity magnetic separation consisting of one roughing, one cleaning and one scavenging, resulting in a high quality iron concentrate grading 65.05% Fe at 96.19% recovery. The research results can provide technical reference for the mineral processing of refractory weakly-magnetic iron ore.

With sodium oxalate and D401 chelating resin as impurity removal materials, impurities of calcium and magnesium in crude lithium solution were removed by adopting a process consisting of chemical precipitation and ion exchange. In an experiment, reaction was firstly run at 25 ℃ for 60 min by adding sodium oxalate at an amount of 17.6 times the theoretical value, with pH of 6.5 and stirring rate of 300 r/min. And then, the lithium solution after filtration flowed through a resin column at a rate of 8 BV/h. As a result, the removal rates of calcium and magnesium reached 98.21% and 83.36%, respectively, and the lithium loss rate was 5.34%. The purified lithium solution was then recrystallized and purified, and the obtained lithium phosphate powder, with regular morphology and uniform dispersion, has its purity higher than 99.5%.

In an experiment, with hydrochloric acid as leaching agent and NaClO₃ as oxidizing agent, lithium was selectively leached from cathode material of spent lithium iron phosphate battery, and the effects of factors, including dosage of hydrochloric acid, solid-liquid ratio and reaction time, on the lithium leaching rate were investigated. It is shown that with an addition of hydrochloric acid at an amount of 1.0 time theoretical value, solid-liquid ratio of 1∶3 and reaction time of 3 h, the average lithium leaching rate can reach 99.33% by using this process. After that, magnesium hydroxide and sodium hydroxide were added into the raffinate in turn to remove impurities of P, Al and Fe. And then, the obtained solution was used to prepare Li₂CO₃ at 95 ℃ by adding anhydrous sodium carbonate. After water washing to remove NaCl, a high purity Li₂CO₃ (99.62%) can be obtained, which meets the industrial standard for industrial-grade lithium carbonate.

In order to solve problems including serious atmospheric pollution by sulfur-containing flue gas and utilization of red mud, sulfur-containing flue gas was treated by using a wet process with red mud. Under the following optimal process conditions, including liquid-solid ratio of 9∶1, flue gas at a temperature of 60 ℃, liquid-gas ratio of 8.0 L/m³, liquid with pH of 5.6 for desulfurization, the SO₂ concentration in flue gas can be reduced from 5 000 mg/m³ to less than 35 mg/m³, meeting a standard of ultra-low emissions. In an industrial experiment on desulfurization with red mud for the flue gas from a 75 t/h coal-fired boiler, the SO₂ concentration in the low-sulfur flue gas was reduced from 4 100 mg/m³ to less than 30 mg/m³, with removal efficiency up to 99.68%；while the SO₂ concentration in the high-sulfur flue gas was reduced from 10 600 mg/m³ to less than 35 mg/m³, with a removal efficiency up to 99.89%. Based on the comparison between this wet desulfurization with red mud and with limestone-gypsum flue gas desulfurization process, it is found that the wet flue gas desulfurization process with red mud as desulfurizer can have the operation cost reduced by 20.05% for the treatment of same volume of flue gas with the same SO₂ concentration.

Limonite-type and serpentine-type nickel laterite ores were taken for experiment. A coupled process for extracting nickel and cobalt was adopted, consisting of chloridizing leaching with HCl as the initial leaching medium for limonite-type nickel laterite ore, and selective hydrolysis for serpentine-type nickel laterite ore. The leaching rates of Ni, Co, and Fe from limonite-type laterite ore were 99.6%, 100%, and 96.9% respectively, under the conditions including acid-to-ore ratio of 5∶4, liquid-to-solid ratio of 4∶1, reaction temperature of 100 ℃, and reaction time of 30 min. After that, the obtained lixivium of limonite-type nickel laterite ore, being mixed with concentrated HCl in a volume ratio of 1∶4, was used to leach serpentine-type nickel laterite at 150 ℃ for 90 min with a liquid-to-solid ratio of 1∶1, resulting in the leaching rates of Ni and Co up to 84.9% and 100%.

A complex precipitation method was adopted to synthesize CuO nanoparticles, and its morphology and structure were characterized. Then, the CuO nanoparticles were taken as the activator in the degradation of ofloxacin with persulfate. Based on the advanced technology of activated persulfate oxidation, the influences of different parameters, including concentration of K₂S₂O₈ and an initial pH of the ofloxacin solution, on the degradation activity of ofloxacin in the wastewater were investigated. It is found that the degradation rate can reach 95.6% with 10 mg/L of ofloxacin in the wastewater with an initial pH of 3.5, by adding 0.003 0 g/L CuO and 1.0 mmol/L K₂S₂O₈. The experiments on capturing free radicals show that SO₄^-· and O₂^-· are active species for the catalytic degradation of ofloxacin, which is possibly the catalytic reaction mechanism.

Experiments of roasting and leaching of some sulfur concentrate were performed, and the effects of two schemes with fixed bed roasting and fluidized bed roasting on gold extraction were analyzed. The results showed that with the sulfur concentrate at a sizing of 80% -0.074 mm, the proper conditions for a fixed bed roasting included a roasting temperature of 650 ℃ and roasting time of 4 h; while the proper conditions for a fluidized bed roasting included a roasting temperature of 650 ℃ and roasting time of 3 h, roasting gas and material in a ratio of 2.1 m³/kg. The calcines obtained by these two roasting methods were then separately leached for 24 h with the slurry concentration of 33% and pH of 11.5, 2 h alkali treatment and CG505 dosage of 10 kg/t, resulting in the leaching rate of gold reaching 69.45% and 69.92% respectively. It is shown that the fluidized bed roasting can bring in a better gold extraction result. This research results can provide a technical basis for recovery of valuable elements from sulfur concentrate.

With nickel removal solution after copper electrolysis taken to be a substitute for sulfuric acid as the leaching agent, a processing technique consisting of oxygen pressure acid leaching, evaporative crystallization and reduction by SO₂ was adopted to realize utilization of arsenic matte resource. The results show that with sulfuric acid concentration at 120 g/L, leaching temperature of 120 ℃, oxygen partial pressure of 0.8 MPa, liquid-solid ratio of 7∶1 and leaching time of 2 h, the leaching rates of copper, arsenic and antimony from arsenic matte can reach 97.99%, 94.68% and 17.28%, respectively, showing an efficient leaching of copper and arsenic from matte copper and selective separation of antimony can be actualized. The solution obtained from pressure acid leaching was then subjected to vacuum evaporation followed by natural cooling for crystallization, leading to the precipitation of copper sulfate. And then reduction by SO₂ was adopted to prepare arsenic trioxid using mother liquor, leading to the obtained copper sulfate with purity up to 98.12% and the obtained arsenic trioxide with purity up to 99.49%.

As for a cobalt-containing raffinate in Africa, several neutralizing agents, including limestone, lime, limestone-lime, as well as a combination of flotation tailings and lime, were separately used for impurity removal in the study, and a preliminary economic evaluation was also conducted. It is found that a combination of flotation tailings and lime is a good choice for impurity removal by neutralization, which can not only save the usage of limestone, but also recover part of the copper and cobalt in flotation tailings. Using this process, the leaching rates of copper and cobalt from flotation tailings can reach 81.69% and 41.10%, respectively. After an addition of lime, the precipitation rates of copper and cobalt can reach 95.43% and 13.64% respectively, and the iron removal rate is up to 99.86%.

The spent cathode carbon block after aluminum electrolysis was treated by acid leaching with a mixed solution of sulfuric acid and ammonium sulfate, and the effects of factors, such as molar ratio of sulfuric acid to ammonium sulfate, liquid-solid ratio, leaching temperature and time, on the leaching rate of cryolite from this spent cathode carbon sulfate were investigated. The results show that at a leaching temperature of 70 ℃, with liquid-solid ratio of 8 mL/g, sulfuric acid and ammonium sulfate in a molar ratio of 4, a 120-min leaching process can lead to the leaching rate of cryolite up to 99.48%. The leaching residue, being composed of carbon and calcium fluoride and free of leaching toxicity, can be treated as a general solid waste.

The effects of different cooling rates in retrogression and re-aging on the microstructure and properties of Al-Zn-Mg-Cu alloy profiles were investigated by performing tests on hardness, electrical conductivity, room temperature tensile, local corrosion and stress corrosion, combined with microstructure characterization by using metallographic microscopy and transmission electron microscopy. The results show that retrogression with cooling rates of 660.0, 12.7 and 0.5 ℃/min, the alloy has a tensile strength of 663.1, 653.4 and 636.9 MPa, an electrical conductivity of 35.1% IACS、35.2% IACS and 36.8% IACS, an exfoliation corrosion in the form of EC, EB-and EB, and a stress corrosion sensitivity of 4.7%, 4.0% and 3.2%, respectively. The precipitates at grain boundaries along the direction of length, with an average size of 48.7, 54.7 and 68.7 nm, are distributed with a spacing of 28.9, 33.6 and 40.3 nm, respectively. The variation in size and distribution is the main reason for variation of the above-mentioned properties. With both mechanical properties and corrosion resistance taken into consideration, it is appropriate to select cooling rates ranging from 0.5 ℃/min to 12.7 ℃/min for retrogression.

The problems of oxidation and corrosion of LIBs copper foil in its production and application have restricted its service life and battery safety. Based on the research status of anti-oxidation technologies for LIBs copper foil in recent years, the mechanism of different passivation methods is summarized. After an introduction of the corrosion mechanism of copper foil fluid in Li-ion battery electrolyte, the research progress in improving corrosion resistance by modification of copper foil surface is reviewed. On this basis, the prospects of chromium-free passivation technology and surface modification technologies for copper foil are presented. At last, a clean, eco-friendly and efficient anti-oxidation and anti-corrosion concept is proposed.

A 5 mm thick DL510 ultra-high strength steel (1 500 MPa) was welded by using metal active gas (MAG) arc welding. The influence of heat input on the microstructure and mechanical properties of weld joint was investigated, and the residual weld stress of the joint was eliminated by hammering while welding. The results show that with heat input within the range of 43-70 kJ/cm, the obtained weld joints can have a good shape. If hammering time is less than 20 min, the tensile strength of weld joint increases as hammering time prolongs; however, after hammering time exceeds 20 min, there is little variation in the tensile strength. With the increasing of heat input, the grain size of weld joints grows obviously, and a small amount of fine granular bainite structure appears in the coarse-grained area with the heat input of 70 kJ/cm, leading to improvement in the toughness of weld joints.

With laser high-energy beam as heat source to initiate exothermic reaction, Cu-Al powder was compacted and sintered into Cu-Al alloy containing in-situ formed hard reinforcing phase Al₂O₃ by laser-induced self-propagating synthesis. The effect of Cu-Al ratio in the composition on the microstructure and properties of alloy system was explored. The results show that the microstructure of Cu-Al alloy is a multiphase structure composed of hard reinforcing phase Al₂O₃ and matrix of CuAl₂, AlCu₄, Al₄Cu₉ and other intermetallic compounds. The alloy has rich dendritic crystals in microstructure, and becomes more uniform and fine-grained with the increase of aluminum content. Increasing the content of aluminum to a certain range is helpful to improve the compactness of sintered products. With copper and aluminum in a mass ratio of 33.2∶66.8, the sintered product has the lowest porosity (10.57% ), the highest microhardness (373HV) and the best wear resistance (with wear rate of 0.137 g/mm²).

An orthogonal experiment was performed for laser welding of 5 mm ZL114A and 6061 aluminum alloys, and the influences of welding parameters on the microstructure and mechanical properties of welded joint were investigated. It is shown that the influences of three parameters of laser welding power, defocus and welding speed are in a descending order. With laser welding power of 3 kW, welding speed of 16 mm/s and the defocus of -3 mm, the welded joint has an average tensile strength of 208.03 MPa and the elongation of 5.16%. Compared to ZL114A and 6061 aluminum alloy, the tensile strength is reduced to 64.14% and 65.60%, respectively, while the elongation is reduced to 41.38% and 33.70%, respectively. The welded joint presents a mixed mode of brittle and ductile fracture when failing under tensile.

Based on the theory of metal oxidation and the mechanism of diffusion rate control, a kinetic model was established for high temperature oxidation of Cr-Fe alloy plate. The effects of composition, temperature, atmosphere, partial pressure of oxygen on the oxidation behavior of the alloy were studied. The results show that the established oxidation kinetic model can quantitatively present an oxidation process of Cr-Fe alloy plate, by which the calculated results are in good agreement with the experimental results. The oxidation characteristic time (t_Φ) of the Cr-Fe alloy is about (3-4) × 10^-14 s, and t_Φ in argon atmosphere decreases gradually with the increase of Fe content in the alloy. Partial pressure oxygen doesn' t bring significant impact to the oxidation rate of alloy, and all products from the equilibrium oxidation of alloy in argon atmosphere are Cr₂O₃. According to the standard of oxidation resistance of superalloy, Cr-Fe alloy in air atmosphere can meet the rating standards for oxidation resistance and secondary oxidation resistance.

ZnO narowires were synthesized by adopting hydrothermal synthesis, and ZnO/activated carbon composite material was then prepared by compounding activated carbon powder and nano-ZnO. The research on the sensing performance of such composite to ethanol gas shows that the sensor with ZnO/activated carbon composite presents good response and recovery characteristics to ethanol gas at 150 ℃. Its sensitivity to the ethanol with concentration of 5 × 10^-6 can be up to 4.75, and will increase positively with the increase of ethanol concentration, which presents a reproducibility and stability.

An experiment on non-quenched and tempered steel F45MnVS was carried out by adopting controlled cooling after hot rolling. The mechanical properties, decarburized layer and microstructure of rolled steel without cooling and after controlled cooling process were compared for analysis. The results show that controlled cooling after hot rolling can lead to the steel with yield strength, elongation, section shrinkage and impact energy improved all, and with the decarburized layer being effectively controlled or even "disappeared". With the surface temperature of the hot-rolled steel decreased to 650 ℃, granular bainite begins to occur on the steel surface; with the surface temperature down to 460 ℃, much granular bainite occurs on the steel surface. It is shown that by using controlled cooling after hot rolling, the ferrite and pearlite on the steel surface and near 1/2 radius on the cross section of the steel become fine-grained. The total ferrite net is reduced, and long strip ferrite is transformed to blocky ferrite. Due to larger size, the central part of steel shows little difference in the microstructure.