With tartaric acid as a leaching agent, an experiment was conducted to investigate the effects of different leaching conditions on the leaching rates of sodium and titanium from red mud. The process parameters were optimized by orthogonal experiments, and the leaching mechanism was then analyzed in combination with the study of leaching kinetics and the properties of leaching residues. It can be seen from the leaching test and orthogonal experiment that with tartaric acid at a concentration of 1.00 mol/L, leaching temperature of 90 ℃, liquid-solid ratio of 8 mL/g, and leaching time of 60 min, the leaching rates of sodium and titanium from red mud can reach 93.50% and 76.66%, respectively. XRD analysis of red mud before and after tartaric acid leaching shows that the sodium in the leaching solution mainly comes from cancrinite and sodium hydroxide in the Bayer process, while the titanium mainly comes from perovskite and secondary titanium that dissolves and re-precipitates on the surface of red mud during the Bayer process. The leaching kinetics analysis shows that both alkali removal and titanium leaching from red mud conform to an unreacted shrinking core model, and the processes of alkali removal and titanium leaching are mainly controlled by interfacial chemical reactions.

A new short-process preparation technique for battery-grade iron phosphate was explored with iron powder and phosphoric acid as main raw materials. The effects of iron powder dissolution mechanism, iron phosphate reaction conditions, and mother liquor recycle on product indicators were investigated. The results show that the dissolution rate of iron powder can reach 97.92% at a temperature of 70 ℃, with phosphoric acid at a concentration of 20%, iron and phosphorus at a ratio of 1/3, and iron powder at a size of 150 μm；after 1 h precipitation at 100 ℃, with an addition of hydrogen peroxide at 110% of the theoretical amount, an iron phosphate with D₅₀ of 2 μm was prepared with the precipitation rate of 98.86%. The obtained iron phosphate has stable crystal form with uniform crystal grains, and the contents of elemental impurities are significantly lower than the requirements specified in the HG/T 4701—2021 standard. The precipitated mother liquor in the process can be recycled, leading to actualization of low-carbon and green production.

An experiment was carried out on treating high-salinity wastewater by air gap membrane distillation (AGMD). Effects of different operating conditions on the performance of AGMD were investigated, and membrane fouling and its control measures were also analyzed. It is shown that the permeation flux increases with the increase of temperature and flow rate of feed, and decreases with the increase of cooling water temperature and salt concentration. The salt rejection rate can maintain above 99.8% with the salinity less than 60 g/L, and still exceed 90% with salinity within the range of 60－100 g/L. It is concluded that AGMD technology can be adopted to treat high salinity wastewater.

With bamboo as a raw material, different hard carbon materials were prepared by different impurity removal processes, and the effects of those processes on the impurity content, physical structure and sodium storage performance of hard carbon were explored. The results show that after impurity removal treatment, the bamboo-derived hard carbon has reduced impurity content and specific surface area, and increased interlayer spacing. With the preparation cost and the sodium storage performance of hard carbon comprehensively taken into consideration, acid leaching is chosen as the impurity removal process for hard carbon. It is shown that at a current density of 30 mA/g, the anode material with prepared hard carbon can have an initial Coulombic efficiency of 83.87% and a reversible specific capacity of 308.96 mAh/g；it demonstrates a capacity retention rate of 96.57% after 100 cycles at a current density of 300 mA/g, showing excellent sodium storage performance.

Effects of quenching and tempering at different temperatures on the microstructure and hardness of annealed W6Mo5Cr4V2 steel were studied by means of OM, SEM, XRD analysis and hardness test. The results show that the microstructure of quenched W6Mo5Cr4V2 steel is mainly composed of martensite, MC carbide rich in V, W and Mo, and M₆C carbide rich in W and Mo, as well as residual austenite. As tempering temperature rises, the carbide in the microstructure of W6Mo5Cr4V2 steel grows in size, and the hardness decreases after an initial increase. After quenching at 1 160 ℃ plus three times of tempering at 540 ℃, W6Mo5Cr4V2 steel has its carbide become smaller and evenly distributed, and its residual austenite almost eliminated, showing the hardness up to 64.2HRC.

The additive manufacturing of SiC_p/Al606 by photocuring process was studied, and the effects of resin monomer and solid volume fraction on the stability, rheological properties and photocuring performance of SiC_p/Al6061 slurry, as well as the compactness and microstructure of sintered product were explored. The results show that as photosensitive resins of PEG200DA and PEG400DA mixed at an appropriate ratio of 1∶1, the prepared slurry with content of 52.5%, viscosity of 5.05 Pa·s (shear rate of 10 s^－1) and single-layer curing thickness of 100.3 μm can meet the requirements for photocuring in additive manufacturing. The SiC_p/Al component manufactured by photocuring process can have a complete structure and good interlayer bonding, and the sintered product with no cracks and obvious necking presents relatively high compactness (94.07%).

To improve the surface quality of high-end plates by descaling and cleaning process, an experimental study was carried out with different process routes that are determined based on the combination of Steel Eco Descaling (SED) technology and other surface pretreatment processes. Based on the analysis of surface appearance, surface roughness, surface micromorphology and surface energy spectrum of the plates treated by different processes, an optimal descaling process is finally determined, consisting of SED, soaking with roller brush cleaner, polishing with scouring pad buffering wheel, and high-pressure flushing. After cleaning treatment with this process, the plate sample is overall in a uniform metallic color, with significantly reduced surface roughness and oxygen content. It is concluded that after treatment with this combined process, surface quality of the third-generation advanced high-strength steel (AHSS) plates for automotive can be effectively improved.

For reducing energy consumption while ensuring weld joint quality, the welding process parameters for electron beam welding of TU2 oxygen-free copper were optimized with SYSWELD simulation software, and a finite element model with appropriate boundary conditions was established for a 30-mm-thick TU2 copper plate. A heat source model was determined based on the actual situation of electron beam welding, and simulation analysis was made by imputing varied energy consumption value in the welding process, with the obtained simulation results compared with actual welding results. It is shown that with a double-ellipsoidal heat source input of 1260 J/mm and a 3D Gaussian heat source input of 5 000 J/mm, a full penetration weld with the lowest energy consumption can be achieved. The simulation results show that the obtained morphology of molten pool is almost the same with that in the actual welding, proving that the welding parameters set in the simulation analysis are feasible for TU2 welding. It is concluded that this study can provide a reliable reference for optimizing the parameters in welding of TU2 oxygen-free copper.

Martensitic steel with different ferrite content and distribution was firstly fabricated by heat treatment. Then, the effects of ferrite content and distribution on the microstructure and properties of such ultra-high strength martensitic steel with yield strength more than 1 100 MPa was explored based on microstructure characterization and mechanical property tests. The microstructure evolution and strengthening and toughening mechanism were also analyzed. The results show that with a small amount of ferrite uniformly distributed in the martensite matrix, the steel sample in the experiment can exhibit not only ultra-high yield strength (1 245.44 MPa) and tensile strength (1 411.96 MPa), but also higher impact energy (80 J) at low temperature, presenting the optimal comprehensive mechanical properties. A small amount of ferrite in the local area continuously distributed along the rolling direction can slightly improve the tensile strength, but the unevenly distributed ferrite can improve the stress concentration and reduce the toughness. An increase in the content of continuously distributed ferrite can improve the tensile strength, but the formation of banded martensite and improved stress concentration make the toughness of the steel sample in the experiment substantially reduced.

Effect of annealing temperature on the mechanical properties and fatigue properties of Al-Cu-Mg-Ag alloy was explored by preforming fatigue crack propagation (FCP) rate testing, room-temperature tensile test and using characterization means such as X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results show that the T4 state specimen annealed at 420 ℃ for 4 h presents higher yield and tensile strength, but poor plasticity. As the annealing temperature increases within the range of 400－430 ℃, the orientation density of the Goss texture in the alloy first increases and then decreases, and the T4 specimen after 4 h annealing at 420 ℃ presents an optimal fatigue performance, with lower FCP rate around 1.34×10^－3 mm per cycle at ΔK≈20 MPa·m^0.5.