In order to improve the working performance of drum cutter in mining mechanism, the cutting process of drum cutter under different working conditions was numerically simulated by using discrete element method (DEM). The effects of cutting thickness, rotating speed and tractor speed on cutting resistance, productivity and specific energy consumption were investigated by single-factor analysis and orthogonal testing. With cutting resistance and specific energy consumption of the drum cutter as evaluation indexes, the best working parameters of the drum cutter were obtained by matrix analysis. The results show that as cutting thickness increases, both cutting resistance and productivity increase, while specific energy consumption decreases. With rotation speed increases, cutting resistance and productivity decrease, but specific energy consumption increases. And with tractor speed increases, both cutting resistance and productivity increase, while specific energy consumption decreases. It is concluded that the optimum working parameters of drum cutter are as follows: cutting thickness of 50 mm, rotation speed of 100 r/min, and tractor speed of 0.06 m/s.

In order to clarify the influence of geometric parameters of tapered pipeline on particle flow characteristics in pneumatic conveying, numerical simulation was conducted for horizontal pipelines with 5 kinds of taper ratio and taper length by adopting CFD-DEM coupling method. Influence of geometric parameters of taper ratio and taper length on particle velocity, pressure loss and Froude number in tapered pipeline was investigated. The results show that tapered pipe can reduce particle velocity. As taper length and taper ratio increase, particle velocity increases first and then decreases. And the tapered pipe can also reduce pressure drop in pipeline. As taper ratio and taper length increase, pressure loss in pipeline increases. The higher the taper ratio, the smaller the Froude number in tapered pipe is. As taper length increases, the Froude number decreases more slowly.

In order to improve accuracy in selection of blasting parameters for open-pit mines, a mathematical model was established for determining bench blasting parameters in open-pit mines based on production cost of stope, and the blasting parameters were then optimized by using an improved sparrow search algorithm. The results show that the improved sparrow search algorithm can effectively improve the effect of bench blasting in open-pit mine, but also improves the construction efficiency. With Yulong Mining Industry Company in Xizang as an example, the blasting parameters after optimization are as follows: hole spacing of 6.2 m, row spacing of 4.9 m, and unit explosive consumption of 0.32 kg/t. With these blasting parameters, the stope production cost goes down by 7.5% to 11.06 yuan/t, and the bulk rate can be controlled within 10%.

Tailings slurry with different mass concentration and cement to sand ratio was prepared with a certain kind of tailings, which was taken to study for its rheological properties by adopting Brookfield R/S+ rheometer. It is found that at room temperature, the mass concentration of paste slurry has a stronger effect on the rheological properties of paste than the cement to sand ratio of slurry. When the concentration is lower than 64%, the cement to sand ratio has little effect on the rheological properties. As the slurry concentration increases, its yield stress and viscosity present exponential growth, which increase at the fastest rate when the slurry concentration is 68%. As the cement to sand ratio of slurry increases, its yield stress and viscosity increase approximately linearly. The influences of slurry concentration, cement to sand ratio, gradation and temperature on rheological properties of slurry were studied by experiments, and then the rheological parameters were predicted by using XGBoost based on the obtained experimental data. It is shown that the relative errors and variances between the predicted results and the actual values are within a reasonable range, which has proven the accuracy of the prediction model.

In order to study the influences of diameter, length and installation position of tapered pipeline on the ratio of full pipe flow in gravity-fed pipeline transport of backfill slurry, a small-scale loop pipe test was carried out by using independently developed tapered pipeline. The hydraulic slope and ratio of full pipe flow were tested for gravity-fed transport of slurry via tapered pipeline, and Pearson correlation analysis was also conducted to explore the influence of various factors on the ratio of full pipe flow. The results show that the ratio of full pipe flow significantly presents a negative correlation to the diameter of tapered pipeline, which increases exponentially with the reduction in the diameter of tapered pipeline. The ratio of full pipe flow increases sharply for a pipe with diameter less than 50 mm. Furthermore, the ratio of full pipe flow presents a positive correlation to the length of tapered pipeline, which increases linearly with the increased length of tapered pipeline. However, the installation position of tapered pipeline in horizontal section of pipe has little effect on the ratio of full pipe flow, which can be negligible.

A nine-hole cut blasting method was adopted in a test of Tonglushan stope. In combination with on-site actual situation, cutting blasting with medium hole length was studied by using theories of compensated space and fissure zone. The first circle of blasthole layout for cutting blasting was optimized, and four types of models for first circle of blasthole layout were then established by LS-DYNA software. After simulation calculation, the rock blasting effect was simulated by using RHT constitutive model. The results show that the more number of empty blastholes (that is, the larger the compensation space), the better the blasting effect in cutting area. The uniformity of empty blasthole position (that is the uniformity of compensative space) will also influence blasting effect. It is shown that both the section and height of the trench after blasting in the field test meet the design requirement, which proves that the first circle blasthole layout for cutting blasting is reasonable.

In order to improve the construction efficiency in benching excavation for tunnels in water-rich ground, a main tunnel of Xiaomaliu tailings pond was taken as an example in the study. A three-dimensional digital model was constructed according to the actual situation of the project, and the fluid-structure interaction analysis was conducted by simulating benching excavation with three types of bench length. Then, the effect of benching construction with different bench length was analyzed in terms of seepage field, displacement field, stress field and plastic zone distribution of tunnel after construction, and a comprehensive evaluation was presented by using CRITIC algorithm. Results show that excavation with micro bench can bring the best construction effect for the tunnel in water-rich ground, followed by excavation with long bench, and excavation with short bench presents poor effect.

Based on a deep foundation pit project for Pazhou Station of Guangzhou Metro, numerical simulation was conducted with FLAC^3D finite element software for foundation pit excavation. Shear test schemes with different stress paths were prepared based on the stress state of the surrounding soil of the foundation pit, and the influence of different stress path on the mechanical properties of the soil was also studied. The results indicate that stress path can bring significant impact to the stress-strain relationship, pore pressure, and shear strength indicators of the soil. The shear strength of the soil in consideration of the unloading stress path of the foundation pit is lower than the shear strength obtained from conventional tests.

A thick layer of accumulated debris after landslide is distributed on the slope in the middle of site. And the debris will lose stability due to excavation of slope, resulting in an unstable slope. The physical and mechanical parameters of those accumulated debris after landslide were determined by performing indoor tests and inverse analysis. According to the site environmental conditions and the distribution characteristics of rock and soil layers, the overall and local stability and deformation characteristics of slope under different working conditions were analyzed by simulation with software. Also, the stability and development trend of slope in the middle of site were comprehensively evaluated. Based on the stability analysis and evaluation results, a corresponding prevention and control suggestion is put forward.

Aiming at the problem of high fragmentation by blasting in Baiyinnuoer Lead-Zinc Mine, the unit consumption of explosive and delay intervals between rows in a fan-shaped pattern of blastholes with medium depth were analyzed by numerical simulation with ANSYS/LS-DYNA. According to Von Mises yield criterion, the effective stress, peak value of vibration velocity, and rock damage area of the recorded unit were analyzed. The results show that with unit consumption of explosive at 1.16 kg/m³ and delay interval of 100 ms between rows, the effective stress, peak value of vibration velocity and rock damage area of the recorded unit all can meet the design requirements. The optimized parameters of unit consumption of explosive and delay interval were then applied in on-site blasting with blastholes in a staggered array. The muck pile after blasting was analyzed by using Split-Desktop 4.0, and it is found that the rock fragmentation by blasting is 4.34%, indicating that high fragmentation by blasting can be effectively controlled.

Fluorite and barite in a low-grade associated ore are intimately intergrown, with the content of 21.2% and 41.7% respectively. Thus, it is hard to separate them via flotation process as they possess similar floatability. In view of the characteristics of this ore, a closed-circuit preferential flotation process consisting of one stage of roughing and seven stages of cleaning was adopted in an experiment, producing a high-quality fluorite concentrate with a yield of 15.60%, CaF₂ grade of 97.36% and recovery of 70.43%, while the BaSO₄ content therein was reduced to only 0.77%. In flotation process, the synergistic effect between inorganic and organic depressants can strengthen the depression of barite and significantly improve the selectivity of fluorite collector, resulting in an efficient separation of fluorite and barite.

Mineral processing tests were conducted for a fine refractory copper ore with Cu grade of 0.75%. A combined process consisting of magnetic separation, rapid flotation of copper minerals, enhanced copper flotation of rapid flotation tailings, and regrinding and cleaning of rough copper concentrate was adopted in a closed-circuit test, yielding a copper concentrate grading of 23.57% Cu at a recovery of 83.23%.

The action and mechanism of copolymer of maleic acid and acrylic acid (PMAA) in flotation separation of barite and fluorite in the presence of collector of sodium oleate were studied. A single mineral flotation test shows that sodium oleate has a good collecting for barite and fluorite, and PMAA has an obvious selective depressing effect on fluorite. A flotation test of artificially mixed minerals confirms that PMAA can achieve the separation of barite from fluorite in the presence of sodium oleate. A Zeta potential test shows that PMAA can hinder the adsorption of sodium oleate on the surface of fluorite, but cannot hinder its adsorption on barite surface. An XPS analysis shows that PMAA isn't effectively adsorbed on the surface of barite, but is chemically adsorbed on the surface of fluorite through the interaction between carboxyl groups of PMAA and calcium ions of fluorite, thus achieving the selective depression of fluorite during the flotation of barite with sodium oleate.

With the polymetallic tailings from Chenzhou of Hunan Province as the research object, an approach of macro volume and mass separation according to the composition of tailings was proposed for a comprehensive utilization. Firstly, magnetic separation was used to sort out iron-aluminum minerals, and then the non-magnetic minerals were processed to obtain calcium and silicon minerals by adopting a flotation process consisting of one stage of roughing, two stages of scavenging and seven stages of cleaning, with sodium oleate as the collector, sodium carbonate as the regulator, and the mixture of GLY-Ⅲ and sodium hexametaphosphate as the depressant. The as-obtained iron-aluminum minerals contain 40.17% garnet at a recovery of 94.08%. The obtained calcium mineral has a Ca grade of 58.00% at a recovery of 50.29%, with the content of fluorite therein reaching 76.47%, while the silicon mineral has a Si grade of 27.96% at a recovery exceeding 99%. These three products all meet the requirements for preparing building materials such as cementing materials and ceramic aggregates, providing new methods and ideas for high consumption of tailings.

According to the difficulties in beneficiation, such as intimate dissemination and complicated intergrowth of pentlandite, chalcopyrite and pyrrhotite, and high content of magnesium-bearing silicate minerals, a beneficiation experiment was conducted for a low-grade copper-nickel sulfide ore from abroad. A flowsheet consisting of rough grinding, fine-grinding of middlings, copper-nickel bulk flotation was introduced to treat this raw ore with Ni and Cu grades respectively as 0.50% and 0.20%. Adopting selective grinding approach and using high-efficient depressant CMC, excessive comminution of copper and nickel minerals can be avoided while magnesium-bearing silicate minerals can be selectively depressed. A closed-circuit test produced a copper-nickel concentrate grading 9.70% Ni and 4.75% Cu at corresponding recoveries of 68.99% and 79.85%, indicating copper and nickel resources were all effectively recovered.

To effectively recover titanium resources in the tailings from a titanium processing plant and improve the relative utilization rate of raw ore, beneficiation of the tailings with a TiO₂ grade of 5.81% from the tailings pond was studied. A gravity and magnetic separation process were proposed and the influences of magnetic field intensity, rising water flow rate, feeding rate and feeding concentration on ilmenite separation indices were studied. The results show that after a gravity separation of +38 μm range, a gravity separation of underflow from -38 μm classification and magnetic separation of overflow from -38 μm classification, a rough concentrate with TiO₂ grade of 16.08% was obtained at recovery of 62.63%, while tailings with a yield of 77.41% and TiO₂ grade of 2.39% was cast off. Consequently, the feeding amount of succeeding flotation can be greatly reduced.

Effects of Ca²⁺, Mg²⁺, SO₄^2- and PO₄^3- on the flotation behavior and surface properties of dolomite and fluorapatite were studied by performing tests of pure mineral flotation, Zeta potential and contact angle. The results show that dissolved ions can significantly change the floatability, surface electricity property and surface wettability of these two minerals. Ca²⁺, Mg²⁺, SO₄^2- and PO₄^3- can reduce their contact angles, weaken their hydrophobicity and decrease the flotation recovery. Ca²⁺ and Mg²⁺ can increase, while SO₄^2- and PO₄^3- can decrease the Zeta potential of dolomite and fluorapatite. These results can be used as reference for removal of harmful ions in phosphorite ore processing.

In view of problems such as low grade of iron concentrate and low metal recovery for 0-15 mm fine ore in JISCO by adopting high-intensity magnetic separation process, experimental researches were conducted, including pre-concentration for tailings discarding, optimization of grinding-separation process and enhancing recovery of tailings by selective flocculation and magnetic seed magnetization. The results show that, the pre-concentration can effectively discard the surrounding rock and gangues that affect the separation indices, thus improving the grade of feed to grinding and separation. Tower grinding of rough concentrate can avoid overgrinding, and the recovery of magnetic concentrate can be increased by 5.32%, while concentrates have similar grade. Selective flocculation and magnetic seed magnetization can further improve metal recovery and reduce iron grade of tailings. An iron concentrate with TFe grade of 48.29% and recovery of 82.90% can be collected over the whole process. The scanning electron microscopy and infrared spectroscopy analyses show that caustic starch can establish bridges between target minerals and magnetic seeds, and it can be adsorbed onto target minerals mainly in the forms of chemisorption and hydrogen bonding, which can reduce the inclusion of gangue minerals in magnetic flocs and improve significantly the iron recovery while ensuring the iron grade of concentrate.

In view of the resource characteristics and production status of Ekou Iron Mine of Taiyuan Iron & Steel (Group) Co Ltd, an experimental research was conducted to upgrade iron grade of the concentrate from the second-stage magnetic separation while reducing impurities therein. An optimized flowsheet consisting sequentially of grinding, low-intensity magnetic separation and reverse flotation was adopted in the experiment, resulting in a high-quality iron concentrate grading 69.93% TFe at a recovery of 93.08%, with a yield of 76.33%, while the SiO₂ content was reduced to 1.63%.

Experimental study was conducted on the properties and beneficiability of a refractory scheelite ore from Luanchuan of Henan Province. The results show that the WO₃ grade for this diopsidite garnet skarn-type molybdenum-tungsten ore is 0.067 2%, and scheelite is the dominant tungsten minerals. This ore is prone to become sliming and also has high content of calcium-bearing gangues, which are unfavorable to scheelite recovery. With a flotation reagents scheme including regulator sodium carbonate 1 500 g/t, depressor sodium silicate 600 g/t, depressor SG 40 g/t, and collector FX-6 400 g/t, a closed-circuit test was performed with the tailings from molybdenum flotation for scheelite flotation. As a result, the roughing stage in the closed-circuit test produced a rough scheelite concentrate grading 1.472% WO₃ at 83.54% recovery, and the cleaning stage produced a scheelite concentrate grading 31.92% at 95.71% recovery. By using a combination of sodium silicate and SG, the recovery efficiency of scheelite can be effectively improved, which is favorable for subsequent large-scale industrial production.

Aiming at the problems of insufficient dissociation degree of mineral monomer and unsatisfactory indices in the leaching process of roasted gold ore in a smelter of Lingbao Gold Group Co Ltd, an ALC mill, for the first time, was applied to fine grinding of roasted gold ore. The results show that with ALC mill used in an open-circuit fine grinding, the filter cake pulped and then milled to a fineness of -38 μm 96% before cyanide leaching, the final cyanide tailings can have its gold grade reduced from 1.72 g/t to 1.42 g/t. As a result, the comprehensive economic benefit can be increased by 8.156 8 million yuan per year.

The pollution of heavy metals in the soil of a zinc smelting site was analyzed, and the influence mechanism of goethite on cadmium migration in the soil was discussed by performing simulation experiments. The results show that the geometric mean values of As, Cd, Cu, Hg and Pb in zinc smelting site soil are 15.9 mg/kg, 1.52 mg/kg, 62.1 mg/kg, 0.108 mg/kg and 167 mg/kg respectively. The average content of Cd is 11.7 times the general value of soil in Hunan Province. It is shown that Cd in the soil has strong migration, and can be infiltrated down to the depth of 6 m or more of the soil. The results of stochastic forest model analysis show that Cd migration in the soil is mainly affected by goethite and silt. Cd in the soil can be adsorbed by goethite and then migrated. The pH value and ionic strength of leachate obviously affect the migration of Cd by goethite in the soil. When the pH of leachate is 6 and the ionic strength is 1 mmol/L, 37.6% of Cd in the soil can be migrated by goethite. Adjusting the pH value and salt ions concentration of soil can change the migration of Cd by goethite in the soil. As a result, the risk of pollution by heavy metals such as Cd in the soil of zinc smelting site can be controlled.

The granulated copper slag prepared by dry centrifugal granulation process was taken as oxygen carrier, a thermodynamic analysis and an experimental study were conducted for oxygen absorption and release reactions of copper slag. The effects of oxidation temperature, reduction temperature, particle size of copper slag and CaO addition on the phase composition of copper slag were investigated. The results show that the reactions of oxygen absorption and release of iron oxide in copper slag run step by step, and the granulated copper slag particles have certain capacity of oxygen absorption and release. Oxidation and reduction at higher temperature is beneficial to reactions of oxygen absorption and release of iron oxide in copper slag. Copper slag with smaller particle size is beneficial to the oxygen absorption reaction of FeO and Fe₃O₄, and addition of CaO is beneficial to the oxygen release reaction of copper slag.

A silicothermic process was adopted to extract phosphorus, and the main chemical reactions and Gibbs free energy were clarified by thermodynamic calculation. The feasibility of the process was then verified by performing practical experiments. The main reaction of silicothermic process for phosphorus extraction is as follows: 2 (3CaO·P₂O₅)+5Si+SiO₂ ==== 2P₂(g)+6CaO·SiO₂. The vacuum degree can promote the reaction to proceed in the forward direction, and a reaction system with lower pressure can lead to smaller standard Gibbs free energy of the reaction, leading to silicothermic reduction reaction occuring much easier. Increasing temperature can promote the reaction to proceed in the forward direction, and prolonging reduction time properly at the same temperature can improve the reduction rate of the reaction. After a reaction at 1 250 ℃ for 2.5 h under normal pressure, rough phosphorus (yellow phosphorus) with purity of 95.03% can be obtained by adopting silicothermic process, and the content of residual phosphorus in the dry slag is 1.45%. It is shown that using siliceous reductant in the silicothermic process for preparing yellow phosphorus can avoid the usage of coke, which conforms to low-carbon development strategy.

The acid leaching solution of electrostatic precipitator dust from copper smelting has a high concentration of sulfuric acid, in which the iron and arsenic exist in the form of Fe³⁺and As⁵⁺, thus it is decided to adopt arsenic sulfide residue as the precipitant for copper precipitation. Firstly, an experiment was performed on the addition of arsenic sulfide residue in single Cu²⁺ and Fe³⁺ solution with different acid concentrations. Based on that, an experiment was performed for copper precipitation and arsenic leaching in the actual acid leaching solution. The results show that in the process of copper precipitation with arsenic sulfide residue, oxidation and reduction reactions between Fe³⁺ and S^2- occur firstly, which is followed by oxidation and reduction reactions of As⁵⁺ and S^2-, and finally a sulfurization reaction for precipitation of Cu²⁺. When the addition of arsenic sulfide residue is at an amount of 1.4 times the theoretical amount, it is shown that the copper precipitation rate is relatively higher, but the rate of arsenic dissolution is lower.

An interactive orthogonal experiment was carried out. With the metallization rate of the products of fluidized reduction of iron ore powder as dependent variables, reduction temperature, reduction time, gas linear velocity and pressure of reduction as independent variables, the effects of various operating parameters and their interactions on the fluidized reduction of iron ore powder were investigated by means of range analysis and variance analysis. Results show that effects of four factors and their interaction on the metallization rate of fluidized reduction of iron ore powder are in the following descending order: reduction temperature > gas linear velocity > reduction time > pressure of reduction > interaction between reduction temperature and gas linear velocity > interaction between reduction temperature and pressure of reduction > interaction between reduction time and gas linear velocity > interaction between pressure of reduction and gas linear velocity > interaction between reduction temperature and reduction time > interaction between pressure of reduction and reduction time. It is shown that higher reduction temperature is helpful to the combination of iron whiskers, forming a compact structure. A higher gas linear velocity can improve the kinetic conditions of fluidized reduction, which is beneficial to fluidized reduction of iron ore powder.

Based on a summarization of decomposition techniques of scheelite by hydrometallurgical process, the advantages and disadvantages of several decomposition techniques, such as decomposition with hydrochloric acid, soda sintering, pressure boiling of soda, decomposition with sodium hydroxide, decomposition with fluorine salt, decomposition with mixture of sulfuric acid and phosphoric acid, as well as lime sintering conversion followed by decomposition with ammonium bicarbonate were all analyzed. It is concluded that those three techniques, including decomposition with fluorine salt, pressure boiling of soda and decomposition with mixture of sulfuric acid and phosphoric acid, will gradually become the mainstream decomposition techniques for scheelite.

Electrolytic manganese anode slime (EMAS) was processed by adopting sulfur-based reduction roasting and sulfuric acid leaching to separate manganese and lead therein. The effects of roasting temperature, molar ratio of sulfur to manganese, roasting time, particle size of EMAS, stirring speed in leaching, leaching temperature, leaching time, solid-liquid ratio and sulfuric acid concentration on separation of manganese and lead were studied. The results show that with the optimized roasting conditions, including roasting temperature of 550 ℃, molar ratio of sulfur to manganese at 1∶1, roasting time of 50 min, EMAS at particle size of -0.177 mm, and optimized acid leaching conditions including stirring speed of 350 r/min, leaching temperature of 40 ℃, leaching time of 20 min, solid-liquid ratio at 1∶20, and sulfuric acid concentration of 2.5 mol/L, the leaching rate of manganese from EMAS can reach 97.4%, and the concentration of manganese ions in filtrate is 38.84 g/L, while the content of Pb in leaching residue is 45.26%. As a result, the effective separation between manganese and lead can be actualized.

A thermodynamic analysis reveals the phase evolution of main metals in the production of low-grade nickel matte by sulfidation smelting of copper-nickel electroplating sludge, and the main influencing factors in the process of sulfidation smelting were analyzed. The thermodynamic calculation shows that with the electroplating sludge grading 6% Cu and 4% Ni, respectively, sulfur gypsum as the sulfurizing agent, the actual addition of sulfur 2.0 times of the theoretical amount, and the smelting atmosphere P(CO)/[P(CO)+P(CO₂)]=50%, the low-grade nickel matter with the expected grade of 57.2% (Cu+Ni) can be produced, with the grade of copper and nickel in the slag lower than 0.2%. It is shown that the direct recovery rate of copper and nickel can reach 99.89% and 96.59% respectively, and the sulfur fixation rate is 77.20%. An industrial application shows that compared with conventional wet metallurgical recovery process, this technique can bring higher metal recovery rate with a green and low carbon process, thus presenting obvious technical advantages.

In order to obtain the optimal concentration of bone glue as a commonly used additive for lead electrolysis and also understand the influence of its colloidal impurities on lead electrolysis, the effects of the concentration of bone glue in the electrolyte, the standing time of bone glue solution and the liquid-solid ratio for purification with activated carbon on lead electrolysis were investigated by evaluating the turbidity of the solution, current efficiency, power consumption and the morphology of precipitated lead. It is found that the optimal concentration of bone glue in lead electrolyte is 0.8 g/L, and colloidal impurities can be removed by resting the bone glue solution for 72 hours or by purifying it with activated carbon in a ratio of 1 000∶1. After purification, lead electrolyte has its current efficiency up to 99.19%. The power consumption of electrolysis declines to 51.79 kW·h/t, and the obtained precipitated lead has a flat and smooth surface.

A foreign copper sulfide concentrate from slag processing was treated by adopting heated sulfuric acid leaching with trivalent iron compound as an oxidant for recovering copper therein. The effects of oxidant dosage, leaching temperature, leaching time, initial concentration of sulfuric acid and liquid-solid ratio on the leaching rate of copper from copper sulfide concentrate were investigated. The results show that with the proper condition, including the oxidant of hematite at an amount of 0.2 g/g ore, leaching temperature of 85 ℃, leaching time of 6 h, liquid-solid ratio at 5∶1, and sulfuric acid with initial concentration of 200 g/L, the copper leaching rate can reach 97.96%. A verification test with different oxidants shows that hematite and magnetite present good oxidability in acid leaching system, leading to the copper in those copper sulfide concentrate leached out at a medium temperature. Also, the higher the purity of trivalent iron compounds, the better the oxidative leaching effect of copper.

To address the problems of low conductivity and poor cycling performance of silicon oxide as negative electrode material, polyacrylamide (PAM) was adopted as a carbon source for the first carbon coating, and the methane-acetylene mixture was used as a gas-phase carbon source for the second coating by chemical vapor deposition to prepare nitrogen-containing double-layer carbon-coated silicon oxide anode materials (SiO_x@ DC-N). Compared with pure gas-phase coated (SiO_x@ GC) and pure liquid-phase coated (SiO_x@ LC) silicon oxide anode material, SiO_x@ DC-N exhibits excellent rate performance and cycling stability, showing that the specific capacity is 850.1 mAh/g at a current density of 4C (1C=1 500 mA/g). The 18650 cylindrical batteries prepared by using a mixed graphite in a ratio of 5∶95 can have a capacity retention rate of 92.70% after 700 cycles of charging and discharging at a current density of 1C.

Experiments were carried out for alumina ceramics with rotary ultrasonic-assisted and ordinary milling-grinding processes respectively by using a small diameter electroplated grinding wheel. The variation of grinding force with ultrasonic power, linear speed of grinding wheel, feed rate and grinding depth during milling-grinding of alumina ceramics was analyzed. The results show that with ultrasonic power from 0 W up to 90 W and other parameters keeping constant, the grinding force is in decline and the surface topography is significantly improved. As the linear speed of grinding wheel increases, while the feed rate and grinding depth decrease, the grinding force in both rotary ultrasonic-assisted and ordinary milling-grinding processes decreases. With the processing parameters in the tested range, the grinding force in rotary ultrasonic-assisted milling-grinding process is lower compared to the ordinary milling-grinding process. Besides, the maximum reduction in normal and tangential grinding force of rotary ultrasonic-assisted milling and grinding can reach 24.17% and 23.30% respectively.

The microstructure and mechanical properties of A356 aluminum alloy joints were studied after they were processed with technique of T6 heat treatment followed by friction stir welding (T6-FSW) and technique of friction stir welding followed by T6 heat treatment (FSW-T6) respectively. It is found that the nugget zone of T6-FSW joint is composed of dynamically recrystallized fine-grains, but the precipitates are dissolved or coarsened. The transverse tensile strength and elongation of T6-FSW joint are 214 MPa and 5.3% respectively, and an average hardness is 76HV_0.5. The tensile strength and elongation of the nugget zone are 236 MPa and 12.5% respectively, and the impact toughness of the joint is 12.10 J. Abnormal grain growth occurs in the nugget zone of FSW-T6 joint, where fine precipitates with high density are formed. The transverse tensile strength and elongation of FSW-T6 joint are 254 MPa and 8.5% respectively, and an average hardness is 96HV_0.5. The tensile strength and elongation of the nugget zone are 297 MPa and 7.0% respectively, and the impact toughness of the joint is 8.23 J.

To address the problems of low recognition accuracy and slow speed of current plate shape pattern recognition methods, a pattern recognition model for cold-rolled strip plate shape based on IHPO-KELM was proposed. Firstly, kernel extreme learning machine (KELM) network was adopted to reduce the number of initial parameters in the network and improve the accuracy and speed of plate shape recognition. Secondly, Levy flight mechanism was added to the improved position update formula for linear combination by using the population of the predator algorithm initialized based on Sine chaos mapping, so as to improve the accuracy of the predator (HPO) algorithm, as well as to address the problem of HPO easily falling into local precocity during the iteration process. Then, the improved predator algorithm was used to optimize the regularization and kernel parameters of the KELM network model, as well as improve the accuracy of plate shape recognition. Finally, the Matlab simulation results have verified that the IHPO-KELM algorithm has the advantages of simple network structure, high convergence speed, and high recognition accuracy. The recognition accuracy of IHPO-KELM algorithm in identifying the measured data of 900HC reversible cold rolling mill of a company is higher than the KELM recognition model optimized with sparrow algorithm (SSA-KELM) by 58.8%, indicating a good generalization ability of IHPO-KEM recognition model. This provides a new idea for efficient and intelligent recognition of plate shape defects.

With Pr₆O₁₁ and CeO₂ as additives, B₄C matrix composite materials were prepared at 2 200 ℃, 1 900 ℃, and 1 700 ℃ by adopting techniques of pressureless sintering, hot pressing sintering, and spark plasma sintering, respectively. The relative microstructure and mechanical properties were also studied. It is found that PrB₆ and CeB₆ formed in situ can fill the pores between B₄C grains, and improve the density of the composites. Compared with pressureless sintering and hot pressing sintering, the technique of spark plasma sintering can bring the prepared composites with higher density. The fracture toughness of B₄C-CeB₆ composites can be improved due to its high relative density, as well as the deflection, branching and bridging of cracks occuring along CeB₆, which extends the expansion path of cracks and reduces stress concentration. The B₄C-CeB₆ composite prepared by spark plasma sintering has good comprehensive mechanical properties, with the relative density, vickers hardness, bending strength and fracture toughness reaching 99.3%, 34.7 GPa, 451 MPa and 4.38 MPa·m^1/2, respectively.

The effects of low temperature tempering on the microstructure and mechanical properties of Q1100 ultra-high strength steel after pretreatment of normalizing and quenching were studied. The results show that tempered martensite were obtained after normalizing (890 ℃ × 40 min) + quenching (890 ℃ × 30 min) + tempering (185-320 ℃ × 90 min) processes. After tempering at different temperatures, all tested steels have their tensile strength higher than 1 360 MPa, yield strength higher than 1 200 MPa, hardness higher than 400HV3, elongation higher than 13%, and impact energy at -40 ℃ higher than 35.2 J. With the rising of tempering temperature, the tensile strength and hardness gradually decrease, the yield strength first increases and then decreases, the elongation after fracturing increases after an initial slight decrease, and the impact energy at -40 ℃ decreases followed by increase. At a tempering temperature of 230 ℃, the steel in the test has tensile strength of 1 445 MPa, yield strength of 1 238 MPa, hardness of 429HV3, plasticity of 13.8%, and toughness of 47.5 J, which all largely exceed the service standard of Q1100 ultra-high strength steel for construction machinery.

A basic polishing solution consisting of perchloric acid and methanol was optimized by adding citric acid and glycerol, and different kind of polishing solution was used for electropolishing of titanium nickel alloy wires. The surface morphology, corrosion resistance, and blood compatibility of untreated and polished wires were compared and studied. The results show that addition of citric acid and glycerol has a significant effect in corrosion inhibition and increases the controllability of the polishing process. With the optimized polishing solution, the surface of electropolished titanium nickel wire becomes flatter, with average roughness declined from 161.3 nm to 15.6 nm. The self-corrosion potential increases from -0.167 V to 0.045 V. The dissolved nickel content of phosphate buffer solution becomes lower, indicating the higher corrosion resistance. The hemolysis rate declines from 2.333% to 0.333%, and the number of adhesive platelet significantly decreases, thus the blood compatibility is enhanced.