The composition structure and operation process of mini seafloor crawler drill are briefly introduced. A multi-body dynamic model of mini seafloor crawler drill was established by using Recurdyn software. And then, a mechanical model was established for seafloor sediment based on an experimental study on mechanical properties of sediment soil. Dynamic simulation was also performed for the motion of mini crawler drill on seafloor. Results show that mini seafloor crawler drill runs on seafloor sediment with slight slippage and an elevation angle due to a certain sinking of seafloor sediment. It is found that the dynamic characteristics of mini seafloor crawler drill is significantly influenced by the mechanical properties of sediment (especially thin and soft sediment), and mini seafloor crawler drill running at a lower speed will bring greater influence to its dynamic characteristics.

With Sanguikou Lead Zinc Mine in the Inner Mongolia Autonomous Region taken for study, the influencing factors and parameter optimization for rock fragmentation by deep-hole cut blasting were explored by performing theoretical analysis, image processing and engineering tests. Firstly, in view of the problems of high fines generation rate and small fragment size on average, the factors influencing blasting fragmentation were tested and field data were collected. Also, image processing and analysis were performed for the muckpile in the test by using Split-Desktop 4.0 software. Then, the primary and secondary factors affecting blasting fragmentation were determined based on grey correlation analysis. Finally, an optimal scheme of blasting parameters was determined by using trend analysis based on actual situation of the site, and was then verified in the practical engineering test. The results show that the fines generation rate by the cut blasting in the mine is mainly affected by the delay time between rows and the borehole spacing, and the average fragment size is mainly affected by the borehole spacing and the number of rows for blasting. The optimized blasting parameters are finally determined as follows: borehole spacing of 1.2 m, row spacing of 1.5 m, burden of 0.8 m, 3 rows of boreholes, delay interval of 13 ms, 0 ms, 9 ms and 18 ms, respectively, between 4 holes, and a delay interval of 42 ms between rows. With the above-mentioned parameters, the blasting can result in the fines generation rate down by 27.19% and the average fragment size up by 62.89%.

With a water cut-off and slope reinforcement project in Tenglong open-pit mine in Hebei Province as the background, a three-dimensional numerical model was established for finite slope with a retaining wall. Firstly, this numerical model was verified for its validity, and then was adopted in numerical simulation and analysis for the distribution law of earth pressure on the back of wall under translational motion. The results show that as the bench becomes wider, the angle of inclination for sliding surface of finite slope falls down to zero first, and then is gradually increased. When the bench is 9 m wide, the numerical solution of passive earth pressure on the back of wall is almost consistent with the analytical solution in term of its variation rule, which fully verifies the validity of this numerical model. The passive earth pressure presents nonlinear distribution, and the active earth pressure presents convex curve distribution. With both the stability of retaining wall and the construction cost taken into consideration, it is recommended that the slope degree should be set at 30° and the bench should be 9 m wide.

An all-weather moving target detection method by using Retinex algorithm based on HSV color space conversion was proposed for complex situation in a mine, which changed the detection of moving target to the detection of special marker on the moving target, and extracted the original grey image of the target by color space conversion. The histogram of grey distribution was used to judge whether to restore the low-illumination image. And special markers were selected in the scene, and the original image was converted to HSV color space. Then, the corresponding ROI region was selected, and the binary image was obtained based on the threshold value. After smoothing of the data, the Canny operator was used to extract contour information, thus characteristic parameters of the marker was extracted. The practice proves that the characteristic parameters of the markers can be accurately obtained by this method, which can thus solve the problem of connector falling off from mechanical equipment under complex situation. It is shown that this method is of certain practical significance in engineering application.

A new directional core acoustic emission technique was used to measure in-situ stress of the gas storage reservoir construction area of the Zhangbei Comprehensive Energy Project in Hebei Province. Results show that three boreholes buried at depth of 90 m have the corresponding in-situ stress dominated by horizontal structural stress, with the maximum principal stress approximately in the same north-south direction. In addition, the circumferential wave velocity anisotropy analysis method was conducted for verification, and the results show that the maximum principal stress is in a direction consistent with the result obtained from the acoustic emission testing of borehole core, which further verifies the correctness of the measurement by acoustic emission technique for the borehole cores.

Random Forest (RF) and eXtreme Gradient Boosting model (XGboost) were adopted to assess the landslide hazard in Changsha City, and frequency ratio (FR) was then used to check and verify the obtained result. A vulnerability assessment system was established based on analytic hierarchy process (AHP) and then adopted to make vulnerability assessment. Finally, efficient risk assessment was realized by integrating the results of hazard assessment and vulnerability assessment with numerical classification method. It is found that RF model is similar to XGBoost model in its evaluation performance, but XGBoost model regulated by FR method can bring a more accurate assessment. Also, the vulnerability assessment has the largest weight value of population density, and high vulnerability areas are mostly concentrated in downtown area and traffic arteries. The areas with relatively higher and high risk account for about 4.6% of the entire study area in Changsha City, which are mainly concentrated in valleys, towns and traffic arteries.

In order to obtain the information of landslide in forest area, a high-resolution digital terrain model was derived from LiDAR point cloud, and the data of landslide in forest area were extracted by Res-Unet network and persistent homology. The Fenghe Experimental Forest in Washington State of USA was selected for study, among which three areas were selected for quantitative analysis. Based on calculation, the extracted data of landslide in the forest area show an average precision of 79.7%, an average recall rate of 70.2%, and average F₁ of 65.5%. The extraction method based on Res-Unet and persistent homology can accurately identify most landslides in the research area. It is shown that by using deep learning and persistent homology, this extraction method can make up for the weakness of traditional remote sensing methods in extracting landslide information in vegetation covered areas, and also provide a technical support for landslide analysis.

In order to explore the reliability of type selection in the design of lift pipe for underwater transport system in deep sea mining, hydrodynamic parameters were checked with transport indices as input for design. Based on the settling velocity of polymetallic nodules, anti-fatigue threaded sleeve of P110 steel, with outer diameter of 244.48 mm and wall thickness of 20.24 mm, was selected for lift pipe. And a towing test performed in a pool shows that the resistance drag coefficient is 1.4 for the lift pipe at the upper end of the pump and 1.3 at the lower end of the pump. Hydrodynamic parameters were calculated and analyzed for the underwater transport system according to working conditions and launching conditions, showing that the safety factor of lift pipe can meet the requirements of API RP 2RD Standard. In the deep-sea polymetallic nodules mining test project, lift pipe in the at-sea acceptance test, with reliable joint connection, could meet the requirement for each transporting parameter, which has verified that the type selection of lift pipe in the design is acceptable.

Calculation was made for four typical pipelines by adopting typical critical flow rate and frictional pressure drop calculation model. The precision of the model was analyzed by comparing the calculated value with the measured value of four pipelines. The results show that as for flow rate and pipe diameter, the calculated values from Wasp model, HAN Wenliang model, FEI Xiangjun model and LIU Dezhong model are in good agreement with the measured value, presenting the maximum deviation within the range of ± 15%. FEI Junxiang model presents higher precision in the calculation of frictional pressure drop, with the maximum deviation within the range of ± 10%, but also has certain margin in calculation. It is concluded that FEI Xiangjun model can provide an important basis and reference for the design of long-distance transportation.

Experimental studies were carried out for iron recovery from the leaching residue of lateritic nickel ore containing 51.38% TFe and 2.01% S, by adopting processing techniques of centrifugal separation, magnetic separation and magnetic roasting. It is found that the process of magnetic roasting followed by magnetic separation is an efficient technique to recover iron from such leaching slag. It is shown that the process of coal-based reduction followed by low-intensity magnetic separation (LIMS) can produce the concentrate grading 62.77% TFe at 94.04% recovery, and the process of gas-based reduction followed by LIMS leads to the concentrate grading 68.77% TFe at 95.15% recovery, with sulfur content of 0.12% in the impurity, which can meet the quality standard for iron concentrate. Although the process of direct reduction followed by LIMS can produce the concentrate grading 90.89% TFe at 88.90% recovery, it is shown that there is higher content of sulfur in the concentrate.

In an experiment for Cu/Mo separation of a copper-molybdenum bulk concentrate, ozone oxidation technique was applied to enhance floatability difference between chalcopyrite and molybdenite. Under adequate ozone oxidation conditions, a molybdenum concentrate grading 47.46% Mo at 94.96% recovery, with Cu content of 0.10% can be obtained from a closed-circuit flotation test adopting a flowsheet consisting of one stage of roughing and three stages of cleaning. It is shown that the flotation indicators obtained by applying ozone oxidation technique is superior to that by using Na₂S as the depressant, which indicates that the ozone oxidation technique can be used to substitute Na₂S depression approach for Mo flotation whilst depressing Cu.

After iron tailings was subjected to preconcentration followed by magnetizing roasting process, the obtained product was taken in an experiment to be processed respectively by adopting a grinding and magnetic separation process and a combined process of grinding plus magnetic separation followed by flotation process. The roasted ore with TFe grade of 33.19% was processed using a grinding and magnetic separation approach, resulting in an iron concentrate grading 63.04% TFe at 80.04% recovery at a grinding fineness of -0.025 mm 97%. Although the processing flowsheet is simple, it is still hard to achieve such a grinding fineness in commercial practice and the grinding cost is also extremely high. However, a process consisting of grinding, magnetic separation and flotation, with a grinding fineness of -0.025 mm 85%, can produce an iron concentrate grading 65.36% TFe at 73.39% recovery. Therewith, such grinding fineness is commercially practicable and the grinding cost can be obviously reduced.

A copper-lead-zinc polymetallic sulfide ore, being characterized by complex dissemination of main minerals and intimate intergrowth of valuable minerals and gangue, was taken for study. In an experiment, the raw ore grading 0.21% Cu, 2.37% Pb and 3.01% Zn was treated with a weak-alkali process, consisting of Cu-Pb bulk flotation, Cu/Pb separation and Zn flotation. With A22 as a copper-lead bulk flotation collector, TZ01 and zinc sulphate as depressants of zinc and sulfur minerals, CZ08 as a zinc flotation collector, sodium sulfite and CMC as depressants for Cu/Pb separation, a copper concentrate grading 22.09% Cu at 70.48% recovery, a lead concentrate grading 59.48% Pb at 89.35% recovery, and a zinc concentrate grading 45.00% Zn at 86.96% recovery were yielded.

Flotation tests were conducted for a low-grade copper-nickel sulfide ore with high content of mud and magnesium oxide from Xinjiang. Using sodium carboxymethyl cellulose and sodium silicate as a combined inhibitor, butyl xanthoxanthate and butyl ammonium black as a combined collector, a closed-circuit test with a flowsheet consisting of a Cu-Ni bulk flotation and a Cu/Ni separation produced a copper concentrate grading 25.11% Cu at 79.90% recovery, with MgO content of 2.02%, as well as a nickel concentrate grading 6.98% Ni at 75.01% recovery, with MgO content of 5.32%. It is concluded that effective recovery and separation of copper and nickel can be actualized.

A low-grade manganese carbonate ore in Tongren of Guizhou Province has complicated mineral compositions, with a higher content of clay mineral illite (19.30%). In order to improve the mineral dressing index of this type of manganese ore resources, magnetic separation experiments was performed for it by using a high gradient magnetic separator. In the experiment, the mineral after pre-desliming was ground by a ball mill to a grinding fineness of -75 μm 69.62%. Then, it was subjected to a magnetic separation process consisting of one roughing and two scavenging, resulting in the final manganese carbonate concentrate grading 19.39% Mn at 83.66% recovery, with yield of 52.81%. The experiment results are of great significance for reducing the discharge of electrolytic manganese slag in Tongren.

An experimental study on mineral processing was carried out for the lean magnetite in M1033 Iron Ore from JISCO. After being crushed with high pressure grinding mill, the ore with a fineness of -0.030 mm 85% was processed using a magnetic separator with the magnetic field strength of 180~220 mT, resulting in an iron concentrate grading 65.18% TFe, with SiO₂ content of 5.21% and Fe metal recovery of 73.20%.

Magnetic separation tests were carried out by adopting a pulsating high gradient magnetic separators (HGMS) for low-grade manganese rhodochrosite ores from Yingjiang County of Yunnan Province, with more than 50% passing size of the raw ore finer than -0.019 mm, TMn grade of 6.72% and manganese carbonate content of 84.97%. Based on the laboratory test applying a SLon-100 type cyclic pulsating HGMS, a pilot test was conducted with a SLon-500 type vertical ring pulsating HGMS, by adopting an optimized processing flowsheet consisting of one roughing, one scavenging and a cleaning process of the scavenging concentrate, a manganese concentrate was produced with TMn grade and recovery of 16.77% and 87.61%, respectively.

Processing parameters were optimized to improve the quality of a vanadium-titanium iron concentrate from Panzhihua-Xichang region. A process flowsheet of staged grinding followed by mineral separation was adopted, consisting of demagnetization, pre-classification with 0.074 mm fine screen, regrinding of +0.074 mm range particles to a fineness of -0.074 mm 92.85% followed by magnetic separation, and direct magnetic separation of -0.074 mm range particles. It is shown that the obtained iron concentrate can have its TFe grade upgraded by 3.19 percentage points, and the total content of SiO₂, Al₂O₃ and MgO therein reduced by 3.91 percentage points.

Experimental study on flocculation sedimentation was carried out in a laboratory for the lead processing tailings from a lead-zinc mine, and the flocculant type, flocculant dosage and feed concentration were all investigated. Then, the selected flocculant was applied into a lead-zinc-sulfur flotation. The results show that the anionic PAM flocculant AX868 presents a better sedimentation effect, and its addition into the flotation system leads to the obtained flotation indicators equivalent to those by using clear water. It is found that an addition of 20 g/t AX868 into the thickener with a diameter of 36 m can meet the sedimentation requirements in industrial production.

Tests were conducted to compare the performance of detergent FD-602 and nitric acid in cleaning the copper concentrate ceramic filter plate in Tonglushan Mine in Hubei Province. The results show that after being cleaned with FD-602, the ceramic filter plate has cleaner surface and its filter cake also presents uniform adsorption during filtration. After being cleaned using FD-602 and nitric acid, the ceramic filter can produce 6.63 t/h and 5.85 t/h filter cakes on average, with average moisture of 11.21% and 11.58%, respectively. Every ton of filter cake consumes 0.16 kg and 1.78 kg detergent, with the cost of 6.4 yuan and 5.696 yuan, respectively. When the cleaning water collected from the FD-602 cleaning process mixed with domestic water at a ratio of 1∶5 is returned to flotation process, it is shown that there is no obvious influence brought to the flotation performance.

As for a kind of low-calcium and low-magnesium stone coal featuring low alkalinity and high content of silica, a process of sulfuric acid curing followed by water leaching was adopted in an experiment, and the effects of grain size, sulfuric acid dosing, curing temperature and curing time on vanadium leaching were investigated. The results show that the leaching rate of vanadium reaches 88.6% when the raw ore with grain size of -0.15 mm was cured at 120 ℃ for 8.5 h by adding sulfuric acid at 20%, and then water leaching at the room temperature for 2 h with liquid and solid at a ratio of 2∶1. During the curing process, the mica structure with the locked vanadium therein is effectively dissociated and soluble vanadium is released. It is shown that the leaching solution has a lower content of silicon (0.08 g/L), significantly reduced compared to the process of direct acid leaching or the process of roasting plus acid leaching, which is beneficial to the subsequent extraction process.

A typical metal mine with a smelter in Hunan Province was taken as an example, and 22 key factors affecting the environmental risk diffusion path of heavy metal pollution area were chosen based on data crawling and on-site case investigation, as well as systematical sorting. Nemerow integrated pollution index (NIPI) of soil was calculated using Nemerow pollution index method, and then was used to aid the identification of key factors. Results show that atmospheric deposition and soil permeability are selected as the environmental risk diffusion path for heavy metal pollution of soil based on the analytic hierarchy process, and the key factors for environmental risk diffusion include distance from pollution source, PM₁₀ content in air, hard cover on ground surface, anti-seepage measures, soil pH value and soil organic matter (SOM) content. It is found that the NIPI of the soil is positively correlated to soil pH value, SOM, PM₁₀, but negatively correlated to the distance from pollution source, hard cover on soil surface and anti-seepage measures. The correlation coefficient fits well with the factor weight (R²=0.63).

The influence of magnetite on bioleaching of chalcopyrite by Acidithiobacillus ferrooxidans was systematically explored by electrochemical tests such as open-circuit potential and cyclic voltammetry. Results show that the leaching rate of chalcopyrite can be increased by increasing the addtion of magnetite in the leaching system by undomesticated bacteria. The bacteria after domestication presents enhanced activity. With the addition of magnetite at an amount of 0.5 g, the copper leaching rate can be increased by around 8%. With the addtion of magnetite at an amout over 0.5 g, jarosite is generated during the leaching process, which can worsen the leaching environment, leading to the copper leaching rate just up by about 2%. The open circuit potential of chalcopyrite is always higher than that of magnetite in the system with different concentrations of Fe³⁺. During the galvanic reaction between chalcopyrite and magnetite, chalcopyrite acts as the cathode, which is not conducive to oxidation and dissolution of chalcopyrite. However, Fe³⁺in the solution can increase the corrosion rate of chalcopyrite, leading to an increased leaching rate of chalcopyrite.

To investigate the current situation of heavy metal pollution in a stone coal mine in Hunan Province, the content of Cd, Hg, As, Pb, Cr, Cr (Ⅵ), Zn, Fe, and Mn in water and soil samples was determined by using ICP, and the risk of heavy metal pollution was evaluated by using the Nemerow pollution index and potential ecological hazard index respectively. The results show that concentrations of Cd, Cr (Ⅵ), Zn, Fe and Mn in water are 1.935 5, 0.025 3, 6.024 9, 16.222 0 and 4.214 9 mg/L on average, with pollution indices of 387.10, 5.06, 3.01, 54.07 and 42.15, presenting the pollution degree in the following descending order: Cd>Fe>Mn>Cr (Ⅵ)>Zn; while content of Pb、Zn、Cr、As、Hg and Cd in the soil is 8.51, 38.59, 18.65, 10.01, 0.18 and 3.41 mg/kg on average, with ecological risk coefficient of 2.13, 0.98, 0.85, 18.00, 28.55 and 339.80 on average, presenting pollution degree in the following descending order: Cd>Hg>As>Pb>Zn>Cr. It is shown that the comprehensive potential ecological risk indices of the whole mine is 390.31, indicating a higher ecological pollution risk. The mine area is polluted by several kinds of heavy metals, especially in the downstream areas of waste dump and sedimentation tank.

Mo-Bi bulk concentrate is usually processed with a longer flowsheet at higher cost, and the traditional bismuth smelting processing technique also features longer flow, high energy consumption, as well as lower bismuth recovery. In order to solve those problems, an oxygen-rich hydrochloric acid leaching process was adopted in an experimental study on beneficiation of Mo-Bi bulk concentrate, and the effects of HCl concentration, leaching time and temperature on the leaching rates of Mo and Bi were investigated. It is shown that oxygen-rich hydrochloric acid leaching at 80 ℃ for 6.0 h, with HCl concentration of 3 mol/L, liquid/solid ratio of 3 ∶ 1, and stirring speed of 500 r/min, can result in the Bi leaching rate up to 99.13% and Mo left in the leaching residue. Thus, molybdenum and bismuth can be efficiently separated. The obtained leaching solution is then subjected to purification for purity removal and replacement with iron plate, and the finally obtained sponge bismuth can have purity exceeding 99%.

In order to comprehensively utilize iron-containing dust and consume alkaline residue from petrochemical industry, a sintering pot test was conducted by adding iron-containing dust and the alkaline residue from petrochemical industry into raw materials for sintering. The results show that an addition of iron-containing dust and the alkaline residue from petrochemical industry can not only improve vertical sintering speed, utilization coefficient, yield rate and tumbler index, but also lead to increased content of alkali metals and Zn, as well as falling in the TFe content in the sintered ores. Thus, the sintered ore presents poor reduction performance, and poor low-temperature reduction pulverization indices. It is found that the raw material with the addition of iron-containing dust at an amount of 0.5% and the addition of alkaline residue from petrochemical industry at an amount of 0.05% can meet the requirement for feed to furnace, and also make it possible for the comprehensive utilization of iron-containing dust and consumption of alkaline residue from petrochemical industry.

In order to effectively separate acid, arsenic and copper/zinc from smelting waste acid, a kind of simulated waste acid was taken to be treated by using electrodialysis with bipolar membrane. The effects of running time, acidity, initial concentration of arsenic and copper/zinc on the separation rate of acid, copper/zinc, and arsenic were investigated, and the process was also applied in the treatment of waste acid from copper smelting for verification. Besides, the surfaces of anion exchange membrane, cation exchange membrane and bipolar membrane in electrodialysis after long-term usage were analyzed and characterized. The results show that with the running time more than 80 min, arsenic concentration less than 9 g/L, acidity less than 5% and copper/zinc concentration less than 5 g/L, three kinds of solution respectively containing arsenic, valence metallic salt and acid were obtained. It is shown that the arsenic separation rate is more than 93%, the recovery rate of copper/zinc is more than 96%, and the recovery rate of acid is more than 97%. More than 90% of other metallic ions (such as Na, K, Mg, Ca) in waste acid are trapped in the bipolar membrane salt chamber, thus making inorganic salt ions effectively recovered from waste acid by an open circuit. After nearly two years of application, electrodialysis membrane and bipolar membrane are observed to have no obvious change in the apparent morphology, and no obvious precipitant attached on them.

The furnace slag generated from smelting of South African vanadium-titanium magnetite was taken in an experimental study by adopting direct reduction followed by melting, and then analyzed by XRD to investigate the effect of basicity on the metallurgical properties of the slag, as well as on the separation of iron from slag. Furthermore, the effect of basicity on the melting characteristics and viscosity of the slag were also explored. Results show that melting at 1 450 ℃ with the addition of carbon at an amount of 5%, the slag has its corresponding softening temperature, hemisphere temperature and flow temperature rising gradually with the increase in basicity. With the basicity ranging from 0.9 to 1.2, the melting temperature of slag increases rapidly, and the measured and calculated viscosity of slag presents a trend of an initial decrease followed by increase. When the basicity rising from 0.9 to 1.4, the diffraction peaks of pyroxene and feldspar in the slag climb to the high value and then start to fall, and the relative contents of perovskite and calcium-aluminum spinel gradually increase after an initial decrease. It is shown that the slag with basicity of 1.2 and viscosity of 0.130 Pa·s can present better performance.

Based on the technique for separation and recovery of metal ions in the leaching solution of spent lithium-ion batteries, nickel and cobalt ions were efficiently separated from manganese ions in leaching solution by selective precipitation of sulfide. The effects of pH value, addition coefficient of sodium sulfide, temperature and time for precipitation on the precipitation rates of nickel, cobalt and manganese ions were systematically investigated. The results show that the precipitation rates of nickel, cobalt, manganese and aluminum ions are 99.73%, 100%, 2.77% and 1.24%, respectively, after 6 min-precipitation at 25 ℃ with the addition of sodium sulfide at a coefficient of 1.5 and pH of 5.0. An orthogonal experiment shows that factors of addition coefficient of sodium sulfide, pH value, precipitation temperature and precipitation time have influence on the precipitation rates of nickel ions in a descending order, while the various factors of addition coefficient of sodium sulfide, precipitation temperature, pH value and precipitation time also have influence on the precipitation rates of cobalt ions in a descending order. It is found that the precipitation rates of manganese and aluminum can reach 99.77% and 6.86%, respectively, after a 12 min-precipitation at 70 ℃ with addition of sodium sulfide at a coefficient of 2.5 and pH of 6.0.

In view of interference of the existence of selenium in determination of gold and silver in crude selenium sample, the sample with an addition of concentrated sulfuric acid was firstly heated to remove selenium. Then, sodium chloride solution was added to precipitate silver therein, and the obtained residue after filtration was taken for gold and silver determination using fire assay by gravimetry. Thus, a process of heating with sulfuric acid to remove selenium followed by fire assay gravimetry was established for continuous determination of gold and silver in crude selenium, and the effects of residual selenium, sulfuric acid dosage and heating time on the determination results were also discussed. Furthermore, such continuous determination process was also compared to the industrial standard method in terms of the analysis of gold and silver in crude selenium. By using the proposed continuous method, the relative standard deviations (RSD₇) of gold was within a range of 0.54%-1.30%, and the RSD₇ of silver was within a range of 0.28%-0.39%. The spike recovery of gold was 94.6%-101.3%, and the spike recovery of silver was 96.3%-100.1%. It is shown that the analysis results are consistent with those by industrial standard method. It is concluded that the proposed determination method, being fast and accurate, is suitable for determination of gold and silver in crude selenium.

Experiments on tempering at different cooling rates were conducted for annealed 30CrMnSiA steel to investigate the effect of cooling rate during tempering on the properties of tempered 30CrMnSiA steel and its microstructure evolution. The results show that the cooling rate during tempering has brought slight effect to the hardness, and a certain influence to impact properties of 30CrMnSiA steel. After tempering at 510 ℃, the 30CrMnSiA steel has its surface mainly subjected to compressive stress and the center subjected to tensile stress. A faster cooling rate during tempering will result in a higher residual stress on the surface of the sample. During the tempering process, C element mainly combines with Fe element to form Fe-C compounds, while a trace of C element, together with Cr and Si elements, forms Cr-C compounds and Si-C compounds. It is found that the rapid cooling rate has slight effect on the content and size of carbides.

The effects of different heat treatment regimes on the microstructure and properties of as-cast Mg-5Sn-1.5Al-1Zn-1Si alloy were investigated. The results indicate that during the dissolution of solid, as the dissolution time is prolongsed, the alloy dendrites gradually dissolve and the grains gradually spheroidize. It is shown that the appropriate dissolution parameter is 510 ℃ × 8 h, and the alloy after such treatment has an evenly distributed microstructure, with a trace of precipitation of fine second-phase particles from the matrix, and thus possesses a high elongation rate. The appropriate aging parameter for the alloy is 200 ℃ × 16 h, and due to precipitation and migration of the phases segregating at the grain boundary, the alloy after aging treatment possesses clear grain boundaries and a microstructure with high uniformity, and also has the yield strength up to 136.3 MPa, which is higher than that of the as-cast alloy by 16.5%. After a treatment including 8 hours of solid dissolution at 510 ℃ and 16 hours of aging at 200 ℃, the alloy has its uniformity and dispersion of the microstructure further improved, and its tensile strength and hardness reach to 178.2 MPa and 59.6HB, respectively, up by 21.6% and 23.4% compared to the as-cast alloy.

An experiment on dynamic loading at high strain rate was conducted for T4 deformed ZK60 magnesium alloy by means of split Hopkinson pressure bar (SHPB). The experimental results show that the flow stresses of the ZK60 alloy samples increase with the increasing of strain rate. Observation of transmission electron microscopy results indicate that a large number of second phases precipitated in the alloy after dynamic loading. The hardness measurement results show that the hardness of material is elevated from 64.40HV to 93.05HV after dynamic loading at 3 000 s^-1. High-density dislocation is generated within the ZK60 alloy and numerous reinforcing phases (β′₁ and β′₂) precipitated in the matrix during deformation.

Interrupted quenching experiments were conducted to investigate the hardness (HV) and unit initiation energy (UIE) of 7N65 alloy samples at various temperatures with different hold time, and the relative TTP-HV and TTP-UIE contour diagrams were also plotted. The precipitation behavior of second phases at various temperatures was characterized by adopting scanning electron microscope and transmission electron microscope. The findings reveal that S-phase (Al₂CuMg) is the dominant grain boundary precipitate after the alloy is held at a temperature between 390 ℃and 450 ℃, and increases in grain size and numbers as hold time is prolonged. Thus the alloy has less fracture toughness and is prone to fragile fracture along with the broken grains. When the alloy sample is held at a temperature between 250 ℃and 390 ℃, precipitates at grain boundaries are predominated by η-phase (MgZn₂), which increases in the numbers and grain size as hold time is prolonged, leading to lower strength of inner grain, smaller difference in strength between inner grains and grain boundaries. Thus, the alloy has higher fracture toughness and is more prone to ductile fracture with more transgranular dimples.

Hollow microsphere BiOBr photocatalyst was synthesized using hydrothermal method. BiOBr photocatalyst doped with different content of Fe were prepared by regulating Fe³⁺/Bi³⁺molar ratio. The crystal structure, morphology, optical and electrochemical properties of Fe-doped BiOBr photocatalyst were characterized respectively. With organic dye Congo red (CR) as the pollutant, its photocatalysis was evaluated by testing the degradation effect of the photocatalyst on the pollutant under visible light irradiation. The results showed that the photocatalytic material with 7% Fe doping exhibited the optimal photocatalytic performance. The degradation efficiency of CR within 180 min of irradiation with 5 W light-emitting diode (LED) was 89.66%, which was much higher than that of undoped BiOBr (62.82%). It is found that the enhanced photocatalytic performance of Fe-doped BiOBr is attributed to the enhanced light absorption and the efficient transfer and separation of photogenerated carriers.

316L stainless steel coatings were prepared on the surface of 304 stainless steel by using laser cladding at different scanning speed, and then metallographic microscopy, X-ray diffractometer, scanning electron microscopy and microhardness tester were adopted respectively to investigate the macroscopic morphology, phase composition, microscopic structure and microhardness for the coatings. The results showed that the 316L coating had a single-phase austenitic structure, and as the scanning speed increased, the grain size of the coating became smaller due to the reduction in the laser power density and heat input, and an increase in the cooling speed. It is found that the microhardness of the coatings is positively correlated with scanning speed, and the 316L coatings prepared by laser cladding at a scanning speed of 1 400 mm/min presents the highest microhardness of about 275HV_0.3. The improvement of the microhardness of the coating is ascribed to the effect of solid solution strengthening caused by lattice distortion combined with the effect of fine crystal strengthening. The wear test showed that the average friction coefficient of 316L coatings was significantly lower than that of 304 stainless steel substrate. And the 316L coating prepared by laser cladding at 1 400 mm/min has a friction coefficient of 0.424 and wear rate of 2.29 × 10^-6 mm³/(N·m), and is prone to abrasive wear.

V₂O₅ thin films were prepared on FTO conductive glass substrates by electrodeposition-assisted sol-gel technique, and effects of precursor concentration on the structure, morphology and optical properties of V₂O₅ thin films were investigated. The results of XRD and XPS show that the prepared films are all V₂O₅ films, and the diffraction peaks in the XRD pattern are sharp, indicating that the films have good crystallinity. No other impurity peaks appeared in the XRD and XPS spectra, which indicated that the prepared V₂O₅ film had high purity. The results of SEM show that the surface of V₂O₅ film is uniform and compact, and mainly consists of spaced small particles. UV/VIS/NIR test results indicate that the transmittance of V₂O₅ thin film is greatly affected by the concentration of precursor, and reaches the highest of 80.18% when the concentration of precursor is 1∶100. The infrared spectrum test result shows that the infrared transmittance of V₂O₅ thin film decreases from 89.5% to 20.5%, as its semiconductor state at low temperature changes to metal state at high temperature.

Fe-Cr-B based wear-resistant coating was prepared on the surface of 45 steel by ultra-high-speed laser cladding. The effects of laser power, scanning speed and powder feeding speed on the aspect ratio and crack of single pass cladding layer were studied by orthogonal experimental method, and the effects of overlap rates on the surface quality of cladded layer was also studied. The optimal process parameters were determined as follows: laser power of 2 300 W, scanning speed of 250 mm/s, powder feeding speed of 24 g/min, and overlap rate of 70%. The results show that the hardness of the coating is between 754HV_0.2 and 831HV_0.2, which is 2.36 times to 2.60 times of the matrix hardness. Under the same conditions, the volume wear of the coating is only 3.64% of electroplated hard chromium coating.

The effects of different heat treatment processes on the microstructure and mechanical properties of RM80 steel were studied by means of scanning electron microscopy, Rockwell hardness tester and universal testing machine. As quenching temperature increases, carbides in RM80 steel gradually dissolve and the original austenite grains continue to grow. During tempering process, the structure of RM80 steel changes from tempered troostite to tempered sorbite, and martensite can still be observed in the structure of RM80 that is tempered after quenching at a higher temperature. After quenching at 1 150 ℃ and then three times of tempering at 550 ℃, RM80 steel finally has a good match between strength and plasticity, with a yield strength of 1 244 MPa, a tensile strength of 1 590 MPa, and an elongation of 12.0%.