A composite photocatalyst of TiO₂-CNTs was synthesized by adopting the sol-gel method and ultrasonic dispersion, and then its activity in the photocatalytic reduction of CO₂ was tested. With a load capacity of carbon nanotubes (CNTs) at 0.75%, the TiO₂-CNTs present a better performance in photocatalytic CO₂ reduction. Under UV irradiation with wavelength of 365 nm, the average yield of CH₄ and CO from the composite catalyst are enhanced by 90% and 156% respectively, compared to the usage of single TiO₂ catalyst. It is believed that the reaction is based on the following mechanisms: CNTs, as a co-catalyst, forms a compact electron transport structure with semiconductor of TiO₂, which significantly accelerates the transfer of photogenic carriers and reduces the electron-cave recombination efficiency. In addition, high specific surface area and excellent adsorption performance of CNTs can increase active sites for reaction, thus improving efficiency of photocatalytic reduction of CO₂ by the catalyst.

In order to address problems of high cost, high noise and low efficiency of traditional smooth blasting technology, a new charging structure without a detonating cord was proposed, and the parameters were determined according to the requirements of smooth blasting. Tests on smooth blasting without a detonating cord were carried out for blastholes with non-coupling coefficients of 3.8, 3.9 and 4.0, respectively. Based on the analysis of the half-hole rate after smooth blasting, the smooth blasting effects of blastholes corresponding to three non-coupling coefficients were analyzed based on comparison. The results show that each blasthole for smooth blasting can be successfully initiated by using a charging structure without a detonating cord, and the half-hole rates of blastholes are 78.40%, 89.60% and 57.60% respectively corresponding to those three non-coupling coefficients. It is concluded that an optimal non-coupling coefficient of this new smooth blasting technology in the test is 3.9.

Effect of step quenching at different temperatures on mechanical and corrosion properties of Al-Mg-Si-Cu alloy was explored by carrying out room temperature tensile test, intergranular corrosion test, electrochemical corrosion test, as well as by means of transmission electron microscopy (TEM). It is found that the alloy, after 60 minutes of step quenching at 100 ℃ followed by 28 days of natural aging, can not only maintain a low yield strength of 162.49 MPa and a high strengthening increment of 105.60 MPa, but also exhibit a 57.2% reduction in intergranular corrosion depth compared to water-quenched alloy. TEM and EDS analyses show that type II Mg-Si clusters formed during step quenching effectively inhibit type I clusters formed during natural aging, while promote precipitation of intergranular β″ phase and β′ phase. Moreover, the precipitated phase at grain boundary is coarse and spherical with discrete distribution due to depletion of nearby solute atoms.

In view of low prediction accuracy and slow speed of traditional prediction methods for strip crown, a weighted prediction model based on random forest (RF) and support vector machine (SVM) was established. The parameters of models based on RF, SVM, and a combination of RF and SVM were optimized respectively by adopting the improved coati optimization algorithm (ICOA), so as to improve crown prediction accuracy. A 1 580 mm production line of a hot-rolling mill in one company was taken in a simulation research on crown prediction based on its actual measurement. The root mean square error of the weighted prediction model based on RF and SVM is 2.23 μm. It is found that this weighted prediction model has its prediction accuracy increased by 7.08% and 2.62% respectively, compared with the models based on RF and SVM respectively.

The alloy structural steel for gear shafts was treated by adopting a quenching and partitioning process, and effects of temperature and time of partitioning on the tensile properties, physical phase composition, microstructure and fracture morphology of structural steel were all explored. The results show that when the end temperature of fixed quenching and temperature of partitioning remain unchanged, extension of partitioning time can lead to gradual decrease in the tensile strength of the steel for gear shafts, and an increase followed by decrease in the fracture strain; with partitioning temperature at 225 ℃ and 275 ℃ respectively, the highest fracture strain is obtained at partitioning time of 120 s and 90 s, respectively; extension of partitioning time can lead to an increase followed by decrease in the strength-elongation product of the steel for gear shafts; the highest strength-elongation product can be obtained when the partitioning time is 90 s, and the strength-elongation product of the sample after quenching and partitioning treatment is obviously higher compared to the sample just treated by quenching. There is almost no residual austenite in the directly quenched sample, while the residual austenite in the sample by quenching and partitioning treatment is in a volume fraction of 3.0%-6.4%. It is found that at the same partitioning temperature, extension of partitioning time can result in martensitic tempering transformation, and carbide precipitation and growth in the steel for gear shafts.

In view of problems of low conversion and low productivity in preparation of benzoquinone by the oxidation of aniline, a leaching process with a shear-enhancement approach was adopted to investigate the effects of adding amount of pyrolusite, acidity, shear rate, and liquid-solid ratio on the conversion rate of p-benzoquinone. It is found that high-speed shearing can accelerate the homogenization of pyrolusite and aniline, and enhance the oxidation reaction, resulting in efficient conversion of aniline. Under optimized process conditions, including acidity of 90 g/L, shear rate of 2 500 r/min, liquid-solid ratio of 5∶1, pyrolusite addition at 1.6 times theoretical amount, the conversion rate of p-benzoquinone is 91.23%. Compared to traditional mechanical stirring process, the reaction time can be significantly shortened and the conversion rate of p-benzoquinone can be significantly increased. It is concluded that the leaching process with shear-enhancement approach can have a promising future in industrial application.

A seabed collector vehicle usually carries a large amount of sediments during mining seabed polymetallic nodules. For reducing the environmental impact caused by tail water discharged in the mining, two kinds of high efficiency and low diffusion desliming pretreatment devices, with twine-drum spiral structure and a direct discharge device with arresting mesh structure, respectively, have been developed, which integrates a jet-assisted transport testing equipment, and is also equipped with an online monitoring system. The desliming effect and environmental performance of the developed device was evaluated by performing computational fluid dynamics simulations and laboratory tests. It is found that the direct discharge device with arresting mesh can pretreat tails with desliming rate over 98%, and this pretreatment device can make quick separation of nodules from sediment, and also lead to subsequent quick settlement of the separated sediment, thus effectively controlling the plume caused by collector in the mining. It is concluded that this developed pretreatment device can improve the lifting efficiency in the mining and mitigate the pollution of tails in the deep-sea mining from the source.

According to the characteristics of high-content aluminum and low-content lithium in hydrochloric acid leaching solution of a clay-type lithium ore in Hubei Province, lithium and aluminum were firstly separated by adopting calcination at 390 ℃ for 2.0 h. Then, the calcined residue, without grinding, was leached at 90 ℃ for 1 h with water in a volume ratio of 3∶1. After the leaching process, the leaching rate of lithium reached 93.85%, and no aluminum was detected in leaching solution, indicating a good Li-Al separation result. An analysis of chemical composition of calcined residue and leaching residue show that after water leaching, the main metal elements in the calcined residue, such as lithium, kalium, sodium, calcium and magnesium, all are leached into the lixivium, and the main composition of leaching residue are alumina and iron oxide.

Manganese-rich phase with low impurity content was prepared with manganese sulfate crude solution by precipitation. A single-factor experiment was carried out to explore effects of reaction time, reaction temperature, pH value and feeding speed of precipitating agent on precipitation efficiency, and then the content of impurity in the finally prepared manganese-rich phase was also analyzed. After the leaching solution with Mn²⁺ in mass concentration of 38 g/L, and pH of 8.0 was precipitated at 60 ℃ for 4 h, with R as precipitating agent fed at a speed of 0.5 L/h, the conversion rate of Mn²⁺ was 94.3%. The ICP and EDS analyses showed that there were low content of impurity ions (K, Na, Ca, Mg) in the precipitate of manganese-rich phase.

For estimating the amount of infiltrated water during heavy rainfall after transition from open-pit mining to underground block caving, the Beiyi mining area of Shilu Iron Mine in Hainan Province after transition from open-pit to underground mining was taken for study. The characteristics of “three zones” formed due to overburden subsidence during the block caving of Beiyi mining area were analyzed based on the field investigation and numerical simulation of land subsidence area. The influence of different overburden on the infiltration coefficient of rainfall was also analyzed with a numerical calculation model for unsaturated overburden. Then, based on the practical measurement of rainfall and drainage, statistical analysis and inverse analysis were conducted for the infiltration coefficient of the caving zone and the surface runoff coefficient. The infiltrated water due to heavy rainfall in Beiyi mining area after transition from open pit from underground mining is calculated to be 225 386 m³, which can provide a reference for the design of infiltration and drainage system for the mine after transition from open-pit to underground mining.