As for a mine in Yunnan, the failure modes of surrounding rock in roadways buried at a depth of 1 500 m was analyzed by adopting a combination of theoretical analysis, in-situ monitoring and numerical simulation for exploring the variation law of surrounding rock stress. The results indicate that the surrounding rock in the main transportation roadway and the drift transportation roadway near the ore body at a depth of 1500 m predominantly belongs to Class Ⅰ and Class Ⅱ rock masses. The influence of stratum stability on the broken zone is greater than that of the roadway cross-sectional dimensions. Under the disturbances of surrounding rock stress, mining-induced stress and blasting loads, the stress in the arch corner of the roadway is higher than that in the side walls. Based on the failure modes of the surrounding rock, a support method combining rock bolts, steel mesh and shotcrete was proposed. The 3DEC numerical simulation results show that after support, the depths of the plastic zones in the side walls, roof and floor of the roadway are reduced by 0.5 m, 0.8 m and 0.6 m, respectively.

Ultra-fine iron ore tailings were modified through thermal activation, and then together with some waste rock were taken for mixed calcination. With the mass ratio of iron ore tailings to waste rock, calcination temperature and calcination time as variables, and the compressive strength of specimens and the content of chemically bound water as the objectives for optimization, an orthogonal experiment was carried out to analyze the sensitivity and influence trends of each factor on the target values, and the hydration products of the cemented materials were also analyzed. The results indicate that with an increase in the mass of waste rock, the specimen compressive strength initially increases and then decreases. As the calcination temperature rises, the specimen compressive strength monotonically decreases. As calcination time is prolonged, the specimen compressive strength first decreases and then increases. In consideration of both calcination cost and material performance, an optimal calcination scheme is finally determined, including iron ore tailings and waste rock in a mass ratio of 7∶3, a calcination temperature of 800 ℃, and a calcination time of 2 h. Under these conditions, the 3-day, 7-day and 28-day compressive strengths of the specimens can reach 4.18, 6.36 and 9.87 MPa, respectively. The main hydration products of the cemented materials are calcium silicate hydrate gel, rankinite, ettringite and hydrotalcite.

In order to study the high-temperature and high-pressure sintering of binderless tungsten carbide (WC), X-ray diffraction, scanning electron microscopy, universal testing machine, and microhardness tester among others were adopted to characterize the phase composition, microstructure and mechanical properties of the WC samples. The results show that the relative density, hardness and fracture toughness of the samples increase as the sintering temperature rises. It is found that WC sample prepared by sintering at 1 500 ℃ can exhibit excellent comprehensive mechanical properties, with relative density of 99.5%, hardness of 2 885HV, and fracture toughness of 9.50 MPa·m^1/2.

To gain an in-depth understanding of research status of ceramic additive manufacturing, the technical processes of direct ink writing, fused deposition modeling, selective laser sintering, stereolithography and digital light processing, as well as the materials used in those technologies are reviewed based on domestic and international researches on ceramic additive manufacturing. The advantages and disadvantages of those five technologies are summarized, which can provide references for their application scenarios. Finally, the prospect for the development of ceramic additive manufacturing is also discussed.

Based on the analysis of patent application trend, major applicants and technological development in recycling of spent lithium iron phosphate batteries by leaching process, a list of key patents of mainstream technologies is presented. The results show that the number of patent applications for recycling of spent lithium iron phosphate batteries by leaching process has been steadily increasing since 2015, and oxidative acid leaching is the mainstream technology at present, with other technologies keeping in pace. However, some outdated technologies are being phased out.

The relevant literature on laser-MIG hybrid welding of aluminum alloy from the China National Knowledge Infrastructure (CNKI) core journal database and Google Scholar database in 2000-2023 was systematically analyzed by using VOSviewer. Three primary research focuses were identified by analyzing citation frequencies of key literature and the evolution of research hotspots: ① the interaction between laser and MIG heat sources, particularly the effects of laser-arc distance and heat source leading modes on plasma behavior and molten pool stability; ② hybrid welded joints, revealing the formation mechanisms and optimization strategies for defects such as porosity and cracks by investigation into morphological characteristics; ③ mechanical properties of welded joints, focusing on microhardness distribution and softening mechanisms in the heat-affected zone. Results indicate that the transition of Mg and other alloying elements can be effectively achieved by adopting welding wire alloying, and after heat treatment of those heat-treatable aluminum alloys, the welded metal exhibit remarkably enhanced strength and hardness through aging. The subsequent researches can employ multi-scale numerical simulations to explore the dynamic coupling mechanisms between laser and arc, and the interaction between droplet transfer and keyhole stability, as well as to optimize process parameters to suppress porosity and overcome the technical bottleneck in simultaneously improving welding speed and quality. This review can provide insights for enhancing the performance of laser-MIG hybrid welding of aluminum alloy.

The effect of Cr content in mass fraction on the microstructure and mechanical properties of Al-Cu-Mg-Ag alloy with a low Cu/Mg ratio was investigated. Results indicate that after an addition of Cr to the Al-Cu-Mg-Ag alloy with low Cu/Mg ratio, phases of Al-Cr and Al_1.6TiCr_0.4 are generated in the alloy; with Cr content from 0.17% up to 0.22%, the alloy has its tensile strength improved from 463 MPa to 484 MPa (a 4.5% increase), and its yield strength enhanced from 288 MPa to 319 MPa (a 10.8% increase). The enhancement in mechanical properties is attributed to solid solution strengthening by Cr and precipitation strengthening by S′ phases.

The parameters of lifter bars in the design of a Φ12.2 m×6.7 m semi-autogenous grinding (SAG) mill liner for the Las Bambas concentrator in Peru were optimized by employing discrete element method, and a quadratic regression model was constructed based on response surface analysis to investigate the effect of various factors on total collision energy and energy dispersion. The results indicate that lifter height has a significant impact on particle motion behavior, and it can alter drop height, particle trajectory and moving range, thereby impacting the collision energy during grinding process. The face angle and width of lifter can influence the distribution of collision energy by adjusting particle positions in the cascading and grinding zones. Based on a comprehensive consideration, the optimal lifter parameters are finally determined as follows: height of 380 mm, width of 100 mm, and face angle of 30°.

Quartz crystal microbalance with dissipation (QCM-D) was used to monitor the micro-mass change during the gold leaching process for exploring the variation of gold leaching rate in cyanide solution. It is found that with a cyanide ion concentration of 55.2 mg/L and the dissolved oxygen concentration in the system increased from 1.5 mg/L to 8.5 mg/L, the leaching rate of gold can be increased from 430.9 ng/(cm²·min) to 514.8 ng/(cm²·min), up 19.5%; with the dissolved oxygen at the mass concentration of 8.5 mg/L, an increase in the cyanide ion concentration from 22.6 mg/L to 55.2 mg/L can lead to the gold leaching rate up to 514.8 ng/(cm²·min) from 60.1 ng/(cm²·min), presenting a 7.6-fold improvement. It is concluded that the gold-leaching rate has something to do with the ratio of cyanide ion concentration to dissolved oxygen concentration . The gold leaching rate is higher with at the room temperature.

An acoustic emission (AE) test of granite under uniaxial step loading was carried out, and the evolution characteristics of AE frequency, event incidence and fractal dimension of the sample at each load-holding stage before occurrence of instability and fracture were analyzed. The results show that the high-frequency signal first decreases and then increases with the increase of stress in the process of step loading; and macro-instability occurs in the sample at the last stage of step loading, at which the internal micro-cracks in the sample undergo from stable propagation to unstable propagation. The incidence of acoustic emission events decreases gradually as time is prolonged. At the last stage of step loading, the incidence of acoustic emission events decreases first and then increases, unstable fracture in the rock increases and micro-cracks gradually merge and coalesce to form macro-cracks, resulting in overall instability and fracture of the sample; with the increase of stress, the fractal dimension of acoustic emission decreases after an initial increase, and the rock fracture develops gradually in an order way from a disorder way.