The present investigation introduces a composite frequency selective Rasorber (CFSR) that demonstrates a wide −1 dB transmission band, two high absorption bands with absorptivity higher than 90%, and large oblique incidence angles up to 60°. The CFSR consists of four functional layers separated by three dielectric slabs, which includes lossless metasurface-I (MS-I), loss metasurface-II (MS-II), loss metasurface-III (MS-III), and a three-dimensional metastructure (3D-MS). MS-I functions as a reflector for two absorption bands with a minimal insertion loss transmission window. MS-II is designed for high-frequency absorption. MS-III serves as a low-frequency absorption layer for CFSR and an impedance matching layer for MS- II. The design methodologies for the transmission window in MS-III and the introduction of 3D-MS are key to achieving high-performance CFSR. The physical mechanisms of CFSR are explained through equivalent circuit model (ECM) analysis and impedance characterization. Finally, measurement results confirm that the proposed CFSR exhibits a −1 dB transmission band ranging from 8.79 to 10.41 GHz with a minimum insertion loss of 0.44 dB at 9.59 GHz; furthermore, the frequency range where reflection coefficient remains below −10 dB is measured to be between 3.33 and 18.00 GHz, aligning well with simulation outcomes.

Al-Mg-Mn-Sc-Zr alloys with excellent weldability have emerged as ideal candidates for aerospace applications. Currently, the investigations on the corrosion behavior of alloys under tungsten inert gas (TIG) welding conditions are insufficient. Here, the stress corrosion cracking (SCC) behavior of base metal (BM) and weld zone (WZ) of TIG welded Al-Mg-Mn-Sc-Zr alloys was investigated by using pre-cracked compact tensile samples immersed in 3.5% NaCl solution. The direct current potential drop (DCPD) method was used to record the crack propagation. The microstructure and fracture morphology of different regions of TIG welded joints were studied by SEM, EBSD and TEM, and the SCC crack propagation mechanism of BM and WZ was analyzed. The results demonstrated that the critical stress intensity factor for stress corrosion cracking (K_ISCC) of BM and WZ was 7.05 MPa·m^1/2 and 11.79 MPa·m^1/2, respectively. Then, the crack propagation rate of BM was faster than that of WZ, and BM was more susceptible to SCC than WZ. Additionally, the fracture mode of the BM mainly exhibited transgranular fracture, while the fracture mode of the WZ mainly exhibited intergranular and transgranular mixed fracture. Moreover, SCC crack propagation was attributed to the combined effect of anodic dissolution and hydrogen embrittlement. This study will provide experimental and theoretical basis for the wide application of TIG welded Al-Mg-Mn-Sc-Zr alloys in aerospace.

In this investigation, we examined the high-temperature corrosion behavior of three nickel-based single-crystal superalloys subjected to a mixed molten salt environment of Na₂SO₄ and NaCl at 700 °C, leading to a preliminary elucidation of their molten salt corrosion mechanisms. By further comparing the corrosion degree of the three nickelbased single-crystal superalloys combined with the Gibbs free energy calculation of the corrosion products, the influence of alloying elements on the corrosion performance of nickel-based single-crystal superalloys was analyzed. It was established that the corrosion mechanism of these nickel-based single-crystal superalloys predominantly involves a cyclic process of oxide layer formation and decomposition, ultimately resulting in the establishment of a protective layer principally composed of NiO, with a constantly regenerating Al₂O₃ barrier, impeding further alloy degradation. Furthermore, the inclusion of elements such as Cr, Al, Ta, and notably Re has been found to markedly improve the thermal corrosion resistance of the superalloys. These insights not only enhance our comprehension of the corrosion mechanisms pertinent to nickel-based superalloys, but also provide strategic directions for alloy composition refinement aimed at bolstering their corrosion resilience.

The microstructures, mechanical properties, and fracture behaviors of an Al-5.9Zn-1.9Mg alloy subjected to thermomechanical treatment across different pre-rolling temperatures have been exhaustively investigated in present work. The pre-deformation temperature exerts a modest influence on grain morphology, while it profoundly impacts the dislocation configurations and precipitation behaviors. Elevating the rolling temperature from ambient to 170 °C result in a reduction in dislocation density within grains accompanied by a notable enhancement in their distributional uniformity. While advancing the temperature to 320 °C prompts the premature formation of precipitates during deformation, which diminishes the precipitation during the subsequent ageing. Tensile results reveal that the thermomechanical treatment incorporating pre-rolling at 170 °C confer a substantial strengthening effect on the alloy on the basis of both grain boundary strengthening and dislocation strengthening stemmed from pre-deformation along with the precipitation strengthening generated by ageing. Furthermore, the microstructure exhibits a relatively scarce presence of inhomogeneous features such as dislocation pile-ups and micro shear bands, contributing favorably to enhance the ductility of the alloy that present the mixture of cleavage fracture and dimple-induced failure.

TiC/Ti₂AlC core-shell structure reinforced Ti-based composite coating was prepared by laser cladding technology. The effect of Ti₂AlC content on the microstructure and mechanical behavior of the coating was studied. The results showed that the reinforced phase was mainly TiC/Ti₂AlC MAX phase core-shell structure at 20% Ti₂AlC content. According to the synthesis mechanism, Ti₂AlC nucleated on TiC through the diffusion of Al atoms to further generate the core-shell structure. The friction and wear test results showed that the wear resistance of the coating was significantly improved under the load distribution effect of the core-shell structure. The friction coefficient decreased to 0.342, and the wear rate reached 8.19×10⁻⁵ mm³/(N·m), which was only 47.07% of TC4 substrate.

High-energy continuous wave (CW) lasers are mostly used in laser damage applications, but efficient laser ablation of transparent materials is challenging due to low optical absorption. Considering the potential of femtosecond (fs) laser-induced air filament for high-peak laser transmission over long distances, femtosecond (fs) laser-induced air filaments are combined with a millisecond (ms) laser to form an fs-ms CPL, enhancing the efficiency of sapphire ablation through synchronized spatial-temporal focusing. Experimental results show that ablation efficiency increases with the ms peak power and duty ratio. Excessive thermal stress leads to fragmentation of the sapphire when the ms duty ratio is over 30% at the peak power of 800 W, or when the peak power is over 500 W at a duty ratio of 100%. Also, the mechanism of high-efficiency damage is revealed through in-situ high-speed imaging. According to it, the ablation process went through 4 stages within 1.5 ms: defect-creating, melting and ablation, spattering, and fragmentation. Finally, the equivalent ablation efficiency of the fs-ms CPL is as high as 1.73×10⁷ µm³/J, about 28 times higher compared to the fs laser only. The CPL damage method explored in this paper can provide theoretical guidance for efficient laser damage of transparent materials.

Arsenic-contained acid polymetallic solutions (AAPS) are produced from the H₂SO₄ leaching of dust generated during nonferrous metals pyrometallurgy such as copper, lead, and zinc. It is difficult to selectively remove As and efficiently recover valuable metals simultaneously. In this study, arsenic was removed from an acid polymetallic solution containing As, Cd, and Zn via scorodite formation using a hydrothermal method. First, a thermodynamic analysis of the Cd²⁺-Zn²⁺-Fe³⁺-AsO₄³⁻-SO₄²⁻-H₂O system showed that the pH range for selective As removal as FeAsO₄ was 1.8–3.9, and a higher pH will result in the precipitation of Cd in the form of Cd₅H₂(AsO₄)₄. Second, the experimental investigations, including neutralization and hydrothermal processes, showed that 88.96% As was selectively removed as scorodite with a flower cluster morphology in a hydrothermal process after adjusting the pH of AAPS to 1.0 via a neutralization process, while the total loss ratios of Cd and Zn were 2.44% and 1.13%, respectively. This study realized selective separation of Zn and Cd from AAPS by controlling the pH to avoid their loss into scorodite.

Microseismic (MS) source location plays an important role in MS monitoring. This paper proposes a MS source location method based on particle swarm optimization (PSO) and multi-sensor arrays, where a free weight joints the P-wave first arrival data. This method adaptively adjusts the preference for “superior” arrays and leverages “inferior” arrays to escape local optima, thereby improving the location accuracy. The effectiveness and stability of this method were validated through synthetic tests, pencil-lead break (PLB) experiments, and mining engineering applications. Specifically, for synthetic tests with 1 µs Gaussian noise and 100 µ is large noise in rock samples, the location error of the multi-sensor arrays jointed location method is only 0.30 cm, which improves location accuracy by 97.51% compared to that using a single sensor array. The average location error of PLB events on three surfaces of a rock sample is reduced by 48.95%, 26.40%, and 55.84%, respectively. For mine blast event tests, the average location error of the dual sensor arrays jointed method is 62.74 m, 54.32% and 14.29% lower than that using only sensor arrays 1 and 2, respectively. In summary, the proposed multi-sensor arrays jointed location method demonstrates good noise resistance, stability, and accuracy, providing a compelling new solution for MS location in relevant mining scenarios.

With the continuous expansion of deep underground engineering and the growing demand for safety monitoring, microseismic monitoring has become a core method for early warning of rock mass fracture and engineering stability assessment. To address problems in existing methods, such as low data processing efficiency and poor phase recognition accuracy under low signal-to-noise ratio (SNR) conditions in complex geological environments, this study proposes an intelligent phase picking model based on ResUNet. The model integrates the residual learning mechanism of ResNet with the multi-scale feature extraction capability of UNet, effectively mitigating the vanishing gradient problem in deep networks. It also achieves cross-layer fusion of shallow detail features and deep semantic features through skip connections in the encoder-decoder structure. Compared with traditional short-time average/long-time average (STA/LTA) algorithms and advanced neural network models such as PhaseNet and EQTransformer, ResUNet shows superior performance in picking P- and S-wave phases. The model was trained on 400000 labeled microseismic signals from the Stanford earthquake dataset (STEAD) and was successfully applied to the Shizhuyuan polymetallic mine in Hunan Province, China. The results demonstrate that ResUNet achieves high picking accuracy and robustness in complex geological conditions, offering reliable technical support for early warning of disasters such as rockburst in deep underground engineering.

Plum blossom pile is a new type of special-shaped pile, which is proposed based on the principle of maximum perimeter with the same cross-sectional area. To advance this technique, primarily for the design of plum blossom piles, it is important to investigate the skin friction behavior of plum blossom pile foundations precluding any straightforward constitutive model. In this work, an analytic method dependent on the cross-sectional geometry and the vertical shearing effects is proposed by means of equilibrium analysis to calculate the effective vertical stress in the surrounding soil, the skin friction/negative skin friction, and the axial force/dragload of a plum blossom pile. Additionally, the curves of skin friction of piles are investigated with the same conditions. The results show that the curves of skin friction of piles deduced according to the developed analytic method agree well with the FEM results and related literature solution, which validates the solution. The axial force of the pile decreases with the increase of the shear action coefficient in the buried depth direction under the vertical concentrated load when considering the vertical shearing effects on the pile-soil interfaces.

The collapse of rock masses in fault-developed zones poses significant safety challenges during the excavation of high-stress underground caverns. This study investigates the spatiotemporal evolution of the collapse mechanisms of the cavern in the Yebatan Hydropower Station through using microseismic (MS) monitoring and displacement measurements. We developed a multi-parameter deformation early warning model that integrates three critical indicators: deformation rate, rate increment, and tangential angle of the deformation time curve. The results of the early warning model show a significant and abrupt increase in the deformation of the rock mass during the collapse process. The safety and stability of the local cavern in the face of excavation-induced disturbances are meticulously assessed utilizing MS data. Spatiotemporal analysis of the MS monitoring indicates a high frequency of MS events during the blasting phase, with a notable clustering of these events in the vicinity of the fault. These research results provide a valuable reference for risk warnings and stability assessments in the fault development zones of analogous caverns.

When the interface of a multilayered saturated soil is rough with noticeable gaps, heat flow lines converge towards the actual contact points, causing thermal flow contraction. Conversely, in the interface between two layers of soil with different properties, pore water flows slowly along the pore channels, demonstrating laminar flow phenomenon. To predict the thermal contact resistance and flow contact resistance at the interface, this paper constructs general imperfect thermal contact model and general imperfect flow contact model, respectively. Utilizing a thermo-hydro-mechanical coupling model, the thermal consolidation behavior of multilayered saturated soil under two-dimensional conditions is investigated. Fourier and Laplace transformations are applied to decouple the governing equations, yielding expressions for the temperature increment, pore water pressure, and displacement in multilayered saturated soil. The inverse Fourier-Laplace transformation is then used to obtain numerical solutions, which are compared with degeneration solutions to validate the computational accuracy. The differences in the thermal consolidation process under various thermal contact and flow contact resistance models are discussed. Furthermore, the impact of parameters such as the thermal resistance coefficient, partition thermal contact coefficient, flow contact resistance coefficient, and partition flow contact coefficient on thermal consolidation are investigated. Results indicate that thermal contact resistance creates a relative thermal gradient at the interface, leading to increased pore water pressure and reduced displacement nearby. In contrast, flow contact resistance generates a relative pore pressure gradient at the interface, resulting in increased displacement within the saturated soil with minimal effect on temperature increment distribution.

Ground reinforcement is crucial for tunnel construction, especially in soft rock tunnels. Existing analytical models are inadequate for predicting the ground reaction curves (GRCs) for reinforced tunnels in strain-softening (SS) rock masses. This study proposes a novel analytical model to determine the GRCs of SS rock masses, incorporating ground reinforcement and intermediate principal stress (IPS). The SS constitutive model captures the progressive post-peak failure, while the elastic-brittle model simulates reinforced rock masses. Nine combined states are innovatively investigated to analyze plastic zone development in natural and reinforced regions. Each region is analyzed separately, and coupled through boundary conditions at interface. Comparison with three types of existing models indicates that these models overestimate reinforcement effects. The deformation prediction errors of single geological material models may exceed 75%. Furthermore, neglecting softening and residual zones in natural regions could lead to errors over 50%. Considering the IPS can effectively utilize the rock strength to reduce tunnel deformation by at least 30%, thereby saving on reinforcement and support costs. The computational results show a satisfactory agreement with the monitoring data from a model test and two tunnel projects. The proposed model may offer valuable insights into the design and construction of reinforced tunnel engineering.

Deep geothermal extraction processes expose rock masses to frequent and significant temperature fluctuations. Developing a comprehensive understanding of the shear fracture mechanisms and crack propagation behaviors in rocks under the influence of cyclic heating is imperative for optimizing geothermal energy extraction. This study encompasses several critical aspects under cyclic heating conditions, including the assessment of stress distribution states, the characterization of two-dimensional fracture paths, the quantitative analysis of three-dimensional damage characteristics on fracture surfaces, and the determination of the fractal dimension of debris generated after the failure of granite. The test results demonstrate that cyclic heating has a pronounced adverse effect on the physical and mechanical properties of granite. Consequently, stress tends to develop and propagate in a direction perpendicular to the two-dimensional fracture path. This leads to an increase in the extent of tensile damage on the fracture surface and accelerates the overall rock failure process. This increases the number of small-sized debris, raises the fractal dimension, and enhances the rock’s rupture degree. In practical enhanced geothermal energy extraction, the real-time monitoring of fracture propagation within the reservoir rock mass is achieved through the analysis of rock debris generated during the staged fracturing process.

Transparent sand is a special material to realize visualization of concealed work in geotechnical engineering. To investigate the dynamic characteristics of transparent sand, a series of undrained cyclic simple shear tests were conducted on the saturated transparent sand composed of fused quartz and refractive index-matched oil mixture. The results reveal that an increase in the initial shear stress ratio significantly affects the shape of the hysteresis loop, particularly resulting in more pronounced asymmetrical accumulation. Factors such as lower relative density, higher cyclic stress ratios and higher initial shear stress ratio have been shown to accelerate cyclic deformation, cyclic pore water pressure and stiffness degradation. The cyclic liquefaction resistance curves decrease as the initial shear stress ratio increases or as relative density decreases. Booker model and power law function model were applied to predict the pore water pressure for transparent sand. Both models yielded excellent fits for their respective condition, indicating a similar dynamic liquefaction pattern to that of natural sands. Finally, transparent sand displays similar dynamic characteristics in terms of cyclic liquefaction resistance and K_α correction factor. These comparisons indicate that transparent sand can serve as an effective means to mimic many natural sands in dynamic model tests.

In this study, a uniaxial cyclic compression test is conducted on coal-rock composite structures under two cyclic loads using MTSE45.104 testing apparatus to investigate the macro-mesoscopic deformation, damage behavior, and energy evolution characteristics of these structures under different cyclic stress disturbances. Three loading and unloading rates (LURs) are tested to examine the damage behaviors and energy-driven characteristics of the composites. The findings reveal that the energy-driven behavior, mechanical properties, and macro-micro degradation characteristics of the composites are significantly influenced by the loading rate. Under the gradual cyclic loading and unloading (CLU) path with a constant lower limit (path I) and the CLU path with variable upper and lower boundaries (path II), an increase in LURs from 0.05 to 0.15 mm/min reduces the average loading time by 32.39% and 48.60%, respectively. Consequently, the total number of cracks in the samples increases by 1.66-fold for path I and 1.41-fold for path II. As LURs further increase, the energy storage limit of samples expands, leading to a higher proportion of transmatrix and shear cracks. Under both cyclic loading conditions, a broader cyclic stress range promotes energy dissipation and the formation of internal fractures. Notably, at higher loading rates, cracks tend to propagate along primary weak surfaces, leading to an increased incidence of intermatrix fractures. This behavior indicates a microscopic feature of the failure mechanisms in composite structures. These results provide a theoretical basis for elucidating the damage and failure characteristics of coal-rock composite structures under cyclic stress disturbances.

Water is a critical factor affecting the mechanical properties of rocks, leading to their degradation. Understanding the creep mechanical behavior of deep roadway surrounding rock under the influence of underground water is of great significance. Compression and creep experiments on sandstone with varying water contents were conducted using a deep soft rock five-linked rheological experiment system. The experimental conditions, including water content (0%, 0.8%, 1.6%, 2.4% and 3.3%) and confining pressure (0, 6, 9 and 12 MPa), were determined based on pressure-free water absorption tests and in-situ stress measurements. The experimental results show that the compressive strength, creep failure stress, and dilatancy stress of sandstone decrease exponentially with increasing water content, while they increase exponentially with confining pressure. The ratio of lateral to axial instantaneous strain increases nearly linearly with the increase of stress, and the lateral creep strain characteristics of the sample are more significant than the axial ones. The duration of the attenuation creep stage of sandstone decreases with increasing water content and increases with increasing confining pressure. The lateral strain enters the steady-state creep stage before the axial strain, and the onset time of the accelerated creep stage of lateral strain under the failure stress is earlier than that of axial strain. The long-term strength of sandstone was determined based on the lateral steady-state creep rate curve, showing a negative exponential relationship with water content and a positive exponential relationship with confining pressure. A method for determining the long-term strength of rocks based on the ratio of lateral strain to axial strain (μ_c) is proposed, which is independent of water content. The research results provide a reliable theoretical basis for the analysis of the long-term stability of roadways under the influence of groundwater and the early prediction of creep failure.

To enhance the recuperation rate of the mine and comply with the stipulations of green mining technology, it is vital to expeditiously recuperate the coal pillar resources in the final stage, thus preventing the considerable squandering of resources. The coal pillar resource of the main roadway and its branch roadway constitutes a significant recovery subject. Its coal pillar shape is regular and possesses a considerable strike distance, facilitating the arrangement of the coal pillar recovery working face (CPRWF) for mining operations. However, for the remaining coal pillars with a thick and hard roof (THF) and multiple tectonic zones, CPRWF encounters challenges in selecting an appropriate layout, managing excessive roof pressure, and predicting mining stress. Aiming at the roadway coal pillar group with THF and multi-structural areas in specific projects, a method of constructing multi-stage CPRWF by one side gob-side entry driving (GSED) and one side roadway reusing is proposed. Through theoretical calculation of roof fracture and numerical simulation verification, combined with field engineering experience and economic analysis, the width of the narrow coal pillar (NCP) in the GSED is determined to be 10 m and the length of the CPRWF is 65 m. Concurrently, the potential safety hazard that the roof will fall asymmetrically and THF is difficult to break during CPRWF mining after GSED is analyzed and verified. Then, a control method involving the pre-cutting of the roof in the reused roadway before mining is proposed. This method has been shown to facilitate the complete collapse of THF, reduce the degree of mine pressure, and facilitate the symmetrical breaking of the roof. Accordingly, a roof-cutting scheme based on a directional drilling rig, bidirectional shaped PVC pipe, and emulsion explosive was devised, and the pre-splitting of 8.2 m THF was accomplished. Field observations indicate that directional cracks are evident in the roof, the coal wall is flat during CPRWF mining, and the overall level of mining pressure is within the control range. Therefore, the combined application of GSED and roof-cutting technology for coal pillar recovery has been successfully implemented, thereby providing new insights and engineering references for the construction and pressure relief mining of CPRWF.

Addressing the issues of significant entry settlement and severe mining pressure manifestations in the conventional 121 approach, an innovative N00 approach is proposed. By comparing the mining process and entry formation process of different approaches, the characteristics of entry roof settlement evolution under different approaches are obtained. The N00 approach, which incorporates roof cutting and NPR cable support, optimizes the mining and entry formation process to reduce the settlement phase of entry roof, decreases the settlement of entry roof, and enhances the steadiness of entry roof. The N00 approach modifies the entry roof structure through roof cutting and establishes a hydraulic support load mechanics model for the mining panel to derive the theoretical load pressure formula for the N00 approach’s hydraulic support. Compared with the conventional 121 approach, the pressure on the N00 approach’s hydraulic support is reduced. Empirical data obtained through field monitoring demonstrate that the N00 approach has reduced the roof settlement of the entry and weakened the mining pressure manifestation at the mining panel, achieving the goal of protecting the entry and mining panel.

This study is to determine the support mechanism of pre-stressed expandable props for the stope roof in room-and-pillar mining, which is crucial for maintaining stability and preventing roof collapse in mines. Utilizing an engineering case from a gold mine in Dandong, China, a laboratory-based similar test is conducted to extract the actual roof characteristic curve. This test continues until the mining stope collapses due to a U-shaped failure. Concurrently, a semi-theoretical method for obtaining the roof characteristic curve is proposed and verified against the actual curve. The semi-theoretical method calculated that the support force and vertical displacement at the demarcation point between the elastic and plastic zones of the roof characteristic curve are 5.0 MPa and 8.20 mm, respectively, corroborating well with the laboratory-based similar test results of 0.22 MPa and 0.730 mm. The weakening factor for the plastic zone in the roof characteristic curve was semi-theoretically estimated to be 0.75. The intersection between the actual roof characteristic curve and the support characteristic curves of expandable props, natural pillars, and concrete props indicates that the expandable prop is the most effective “yielding support” for the stope roof in room-and-pillar mining. That is, the deformation and failure of the stope roof can be effectively controlled with proper release of roof stress. This study provides practical insights for optimizing support strategies in room-and-pillar mining, enhancing the safety and efficiency of mining operations.

Driven by rapid technological advancements and economic growth, mineral extraction and metal refining have increased dramatically, generating huge volumes of tailings and mine waste (TMWs). Investigating the morphological fractions of heavy metals and metalloids (HMMs) in TMWs is key to evaluating their leaching potential into the environment; however, traditional experiments are time-consuming and labor-intensive. In this study, 10 machine learning (ML) algorithms were used and compared for rapidly predicting the morphological fractions of HMMs in TMWs. A dataset comprising 2376 data points was used, with mineral composition, elemental properties, and total concentration used as inputs and concentration of morphological fraction used as output. After grid search optimization, the extra tree model performed the best, achieving coefficient of determination (R²) of 0.946 and 0.942 on the validation and test sets, respectively. Electronegativity was found to have the greatest impact on the morphological fraction. The models’ performance was enhanced by applying an ensemble method to the top three optimal ML models, including gradient boosting decision tree, extra trees and categorical boosting. Overall, the proposed framework can accurately predict the concentrations of different morphological fractions of HMMs in TMWs. This approach can minimize detection time, aid in the safe management and recovery of TMWs.

Mechanical activation (MA) is a significant pretreatment technique for enhancing the dissolution of mineral; however, its promotion effect on the role of pyrite during chalcopyrite bioleaching has not been elucidated up to now. In this study, the effect of MA on the role of pyrite on chalcopyrite bioleaching mediated by Acidithiobacillus ferrooxidans was investigated by X-ray diffraction, scanning electron microscopy, particle size distribution analysis, and electrochemical measurement. The results showed MA could significantly reduce the minerals particle size, and increase the specific surface area and surface energy of minerals. For example, the d₅₀ of chalcopyrite reduced from 13.40 to 0.31 µm after MA. The copper extraction of mixed MA-chalcopyrite and MA-pyrite system was 63.5%, which exhibited a 51.9% enhancement compared to the non-activated mixed system. Electrochemical experiments identified that the strengthening effect of pyrite on chalcopyrite dissolution was negligible before MA. After MA, the dissolution mechanism of chalcopyrite was not changed, and pyrite could not only provide additional oxidants (acids and iron) but also act as the cathode in the galvanic couple. In this case, the bioleaching of chalcopyrite was accelerated. Therefore, a model of the promotion effect of mechanical activation on the role of pyrite on chalcopyrite bioleaching was proposed.

Full-component pyrolysis can process organic components and reduce cathode materials, making it a key focus in green recycling of lithium-ion batteries (LIBs). However, the leaching mechanism and kinetics of pyrolyzed black powder in organic acid systems remain unclear, with most research still at the laboratory stage. This study pioneers the exploration of the leaching behavior and reaction mechanism of valuable metal extraction from industrial-scale pyrolyzed black powder using citric acid. The effects of various leaching conditions on the extraction of metals were investigated by single factor experiments and response surface method. Under optimal conditions, the leaching efficiencies of Li, Ni, Co, and Mn all exceeded 97%. Kinetic analysis revealed that the leaching process was controlled by internal diffusion, with the apparent activation energies for Li, Ni, Co, and Mn being 17.89, 23.14, 20.27, and 15.21 kJ/mol, respectively. Additionally, residue characterization identified FePO₄ formation as the primary inhibitor of iron dissolution.

Nickel laterite ore is an important nickel-bearing mineral. Research on pre-heating and hydrogen pre-reduction in the pyrometallurgical process of nickel laterite ore is very limited, especially when using fluidized bed roasting. This study systematically explores the mechanisms of fluidized bed pre-heating treatment and hydrogen pre-reduction in the roasting process of saprolitic nickel laterite ore. According to single-factor experiment results, the appropriate pre-heating and pre-reduction conditions were a pre-heating temperature of 700 °C, a pre-heating time of 30 min, a pre-reduction temperature of 700 °C, a pre-reduction time of 30 min, and a hydrogen concentration of 80%. Then, the nickel metallization rate and iron metallization rate reached 90.56% and 41.31%, respectively. Various analytical and testing methods were employed to study the changes in phase composition, magnetism, surface element valence states, and microstructure of nickel laterite ore during fluidized pre-heating and pre-reduction. The study shows that hydrogen can achieve nickel reduction at relatively low temperatures. It was also found that pre-heating treatment of nickel laterite ore is beneficial. Pre-heating opens up the mineral structures of serpentine and limonite, allowing the reducing gas and nickel to interact quickly during the reduction process, enhancing the pre-reduction process.

Selenium distillation slag (SDS) is a high-value-added secondary resource with a high recovery value. This paper aims to investigate the leaching behavior and kinetics of selenium, tellurium, and copper in the SDS acid oxidation leaching process with H₂SO₄ and H₂O₂. The experimental results showed that under the optimum conditions, the contents of selenium, tellurium, and copper in the SDS were reduced from 22.13 wt%, 3.58 wt%, and 6.42 wt% to 3.06 wt%, 0.27 wt%, and 0.33 wt%, respectively. Correspondingly, the recovery rates are 87.08%, 97.15% and 99.7%. The leaching processes of selenium and tellurium were controlled by diffusion and chemical reactions, and the leaching behavior of copper was controlled by chemical reactions. Below 45 °C, the activation energies for selenium, tellurium, and copper were found to be 26.47, 62.18 and 19.67 kJ/mol, respectively. In addition, the contents of lead, silver and gold in the leaching residue are increased to 46.8 wt%, 8.35 wt% and 0.27 wt%, respectively. These substances can be utilized as raw materials for the recovery of these valuable metals. Importantly, the entire process does not generate toxic or harmful waste, making it a green and environmentally friendly method for resource recovery.

This study focuses on using a green reagent scheme of methanesulfonic acid (MSA) and citric acid (CA) to extract valuable metals from the cathodes, aiming to minimize environmental impact during the recycling process. Leaching studies on LiCoO₂ identified optimal conditions as follows: 2.4 mol/L MSA, 1.6 mol/L CA, S/L ratio of 80 g/L, leaching temperature of 90°C and leaching time of 6 h. The maximum Co and Li extraction achieved was 92% and 85%, respectively. LiCoO₂ dissolution in MSA-CA leaching solution is highly impacted by temperature; Avrami equation showed a good fitting for the leaching data. The experimental activation energy of Co and Li was 50.98 kJ/mol and 50.55 kJ/mol, respectively, indicating that it is a chemical reaction-controlled process. Furthermore, cobalt was efficiently recovered from the leachate using oxalic acid, achieving a precipitation efficiency of 99.91% and a high-purity cobalt oxalate product (99.85 wt.%). In the MSA-CA leaching solution, MSA served as a lixiviant, while CA played a key role in reducing Co in LiCoO₂. The overall organic acid leaching methodology presents an attractive option due to its reduced environmental impact.

Arching and cracking of joints between slabs have become a problem in China Railway Track System (CRTS) II slab track. The slab track is susceptible to complex temperature variations as a longitudinal continuous structure. Based on measured data, a thermal-mechanical coupling model of the track was established. The deformation characteristics and interfacial damage behavior of joints under typical temperature fields were studied. The findings indicate that the annual extreme temperature range of the slab track, fluctuates from −1.4 to 49.8 °C. The annual temperature gradient within the vertical depth range of 0 to 0.2 m of the track varies between −16.19 °C/m and 30.15 °C/m. The vertical deformation of joints is significantly influenced by high temperatures, with a maximum measured deformation of 0.828 mm. The joint seams are primarily affected by low temperatures, which lead to a separation of 0.9 to 1.0 mm. Conversely, interlayer damage of joints is predominantly influenced by elevated temperatures. In summer, the maximum ratio of interface damage area in the joint can reach up to 95%, with the maximum debonding area ratio can be as high as 84%. The research results can provide help for joint damage regularity and deformation control of CRTS II slab track.