The asymmetric creep aging behaviors of a pre-treated Al-Zn-Mg-Cu alloy under high and low stresses have been investigated for high precision creep age forming application of aluminum integral panels. With the increase of applied stress, the creep strains under the tensile stresses are higher than those of compressive stresses and the asymmetry of creep strain is more obvious. However, the mechanical properties of tensile stress creep aged samples are lower than those of compressive stress creep aged samples. Dislocation density, dislocation moving velocity and the proportion of precipitates directly lead to the asymmetry of creep strain and mechanical properties after tensile-compressive creep aging process. In addition, the tensile and compressive stresses have little effect on the width of the precipitate-free zone (PFZ). It indicates that in the high stress creep age forming process of the pretreated Al-Zn-Mg-Cu alloy, the tensile stress promotes the dislocation motion to obtain a better creep strain but weakens its mechanical properties compared with the compressive stress. In the field of civil aviation aircraft component manufacturing, the introduction of tension and compression stress asymmetry into the creep constitutive model may improve the accuracy of creep age forming components.

Basalt fibers/7075 aluminum matrix composites were studied to meet the demand of aluminum alloy drill pipes for material wear resistance. The composites with different basalt fiber additions were prepared by hot pressed sintering and hot extrusion. The mechanical properties as well as friction and wear properties of the composites were studied by microstructure analysis, tensile experiments, friction and wear experiments. The results showed that basalt fibers were oriented and uniformly distributed and led to local grain refinement in the alloy matrix. The hardness and elongation of the composites were improved. The friction coefficient of the composites increased and then decreased, and the maximum wear depth and wear amount decreased, then increased, then decreased again with the growth of basalt fiber addition. Meanwhile, the inclusion of basalt fibers mitigated the uneven wear of the extruded 7075 aluminum alloy. The value of wear depth difference of 7075-0.2BF was the smallest, and that of 7075-2.0BF was close to it. The maximum wear depth and wear volume the 7075-0.2BF and 7075-2.0BF were also the smallest. The inhibition of uneven wear by basalt fibers enhanced of wear resistance for 7075 aluminum alloy, which has reference significance for improving the performance of aluminum alloy drill pipes.

This article examines the influence of annealing temperature on fracture toughness and forming limit curves of dissimilar aluminum/silver sheets. In the cold roll bonding process, after brushing and acid washing, the prepared surfaces are placed on top of each other and by rolling with reduction more than 50%, the bonding between layers is established. In this research, the roll bonding process was done at room temperature, without the use of lubricants and with a 70% thickness reduction. Then, the final thickness of the Ag/Al bilayer sheet reached 350 µm by several stages of cold rolling. Before cold rolling, it should be noted that to decrease the hardness created due to plastic deformation, the roll-bonded samples were subjected to annealing heat treatment at 400 °C for 90 min. Thus, the final samples were annealed at 200, 300 and 400 °C for 90 min and cooled in a furnace to examine the annealing temperature effects. The uniaxial tensile and microhardness tests measured mechanical properties. Also, to investigate the fracture mechanism, the fractography of the cross-section was examined by scanning electron microscope (SEM). To evaluate the formability of Ag/Al bilayer sheets, forming limit curves were obtained experimentally through the Nakazima test. The resistance of composites to failure due to cracking was also investigated by fracture toughness. The results showed that annealing increases the elongation and formability of the Ag/Al bilayer sheet while reduces the ultimate tensile strength and fracture toughness. However, the changing trend is not the same at different temperatures, and according to the results, the most significant effect is obtained at 300 °C and aluminum layers. It was also determined that by increasing annealing temperature, the fracture mechanism from shear ductile with small and shallow dimples becomes ductile with deep cavities.

WC particles reinforced CoCrFeNiMo high-entropy alloy (HEA) composite coatings were prepared on Cr12MoV steel successfully by laser cladding technology to improve the wear resistance of substrates. Effect of WC content on microstructure and wear property of the composite coatings was studied in detail. Large numbers of carbides with four main types: primary carbide crystals, eutectic structures, massive crystals growing along the periphery of the remaining WC particles and incompletely fused WC particles, were found to exist in the WC/CoCrFeNiMo composite coatings. With increasing WC content, the microhardness of coatings is gradually improved while the average friction coefficients follow the opposite trend due to solid solution strengthening and second phase strengthening effect. The maximum microhardness and minimum friction coefficient are HV_0.2 689.7 and 0.72, respectively, for the composite coating with 30 wt.% WC, the wear resistance of the substrate is improved significantly, the wear mechanisms are spalling wear and abrasive wear due to their high microhardness.

Polyvinylidene fluoride/lead zirconate titanate (PVDF/PZT) composite films have been prepared by direct ink writing and the effect of PZT content on crystallization behavior and electrical properties of film were systematically investigated. The composite films were characterized by scanning electron microscope (SEM), X-ray diffractometer (XRD), Flourier transform infrared spectroscope (FTIR) and differential scanning calorimeter (DSC). The results show that, surface modified PZT powder (PZT@PDA) is successfully coated by polydopamine (PDA), resulting in a large number of polar groups that interact with the —CF₂— groups in PVDF, inducing the generation of polar β phase due to hydrogen bonding formed in the interaction. The β phase content in composite film increases with increasing PZT@PDA content, up to 28.09% as with 5 wt.% PZT@PDA. PZT@PDA plays a role of nucleating agent to promote the generation of polar phases in the film and also acts as an impurity hindering the growth of nuclei to reduce crystallinity. Moreover, the presence of PZT@PDA in interfaces provides more sites for the occurrence of interfacial polarization and thus improving the electrical properties of films. The composite film with 5 wt.% PZT@PDA possesses the highest dielectric constant (8.61) and residual polarization value (0.6803 µC/cm²).

This study was conducted in two sections. Initially, the effects of NaCl, MgCl₂, and urea were investigated on extracting copper and iron from chalcopyrite. Subsequently, CuFe₂O₄-based electrodes for supercapacitors were synthesized using the extracted solution. The first phase revealed that 3 mol/L NaCl achieved the highest extraction performance, yielding 60% Cu and 23% Fe. MgCl₂ at 1.5 mol/L extracted 52% Cu and 27% Fe, while a combination of 0.5 mol/L MgCl₂ and 1.6 mol/L urea yielded 57% Cu and 20% Fe. Urea effectively reduced iron levels. CuFe₂O₄-based electrodes were then successfully synthesized via a hydrothermal method using a MgCl₂-urea solution. Characterization studies confirmed CuFe₂O₄ formation with a 2D structure and 45–50 nm wall thickness on nickel foam. Electrochemical analysis showed a specific capacitance of 725 mF/cm² at 2 mA/cm² current density, with energy and power densities of 12.3 mW·h/cm² and 175 mW/cm², respectively. These findings suggest that chalcopyrite has the potential for direct use in energy storage.

Applying bio-oxidation waste solution (BOS) to chemical-biological two-stage oxidation process can significantly improve the bio-oxidation efficiency of arsenopyrite. This study aims to clarify the enhanced oxidation mechanism of arsenopyrite by evaluating the effects of physical and chemical changes of arsenopyrite in BOS chemical oxidation stage on mineral dissolution kinetics, as well as microbial growth activity and community structure composition in bio-oxidation stage. The results showed that the chemical oxidation contributed to destroying the physical and chemical structure of arsenopyrite surface and reducing the particle size, and led to the formation of nitrogenous substances on mineral surface. These chemical oxidation behaviors effectively promoted Fe³⁺ cycling in the bio-oxidation system and weakened the inhibitory effect of the sulfur film on ionic diffusion, thereby enhancing the dissolution kinetics of the arsenopyrite. Therefore, the bio-oxidation efficiency of arsenopyrite was significantly increased in the two-stage oxidation process. After 18 d, the two-stage oxidation process achieved total extraction rates of (88.8±2.0)%, (86.7±1.3)%, and (74.7±3.0)% for As, Fe, and S elements, respectively. These values represented a significant increase of (50.8±3.4)%, (47.1±2.7)%, and (46.0±0.7)%, respectively, compared to the one-stage bio-oxidation process.

A pre-reduction sintering process with flue gas recirculation (PSP_fsg-FGR) was developed to mitigate alkalis harm to the blast furnace and reduce the flue gas emission in the whole ironmaking process. The results indicated that the pre-reduction sintering process (PSP) can effectively remove 58.02% of K and 30.68% of Na from raw mixtures and improve yield and tumbler index to 74.40% and 68.69%, respectively. Moreover, PSP was conducive to reducing NO_x and SO₂ emissions and simultaneously increasing CO content in flue gas. Circulating CO-containing flue gas to sintering bed effectively recycled CO and further improved K and Na removal ratio to 74.11% and 32.92%, respectively. Microstructural analysis revealed that the pre-reduced sinter mainly consisted of magnetite, wustite and a small quantity of metallic iron, and very few silicate glass phase was also formed. This process can simultaneously realize alkali metal elements removal as well as flue gas emission reduction from the integrated ironmaking process.

Biochar-derived dissolved organic matter (BCDOM), an essential component of biochar, plays a vital role in regulating the physicochemical and biological properties of soils during biochar application. However, the influence of BCDOM on soil organisms has not been clearly explained. Hence, this review aims to discuss the factors affecting BCDOM and its interaction with soil substances including organic pollutants, heavy metals, and microorganisms. Results displayed that the quantity of BCDOM ranges from 0.17 to 37.03 mg/g, which was influenced by feedstock, preparation methods of biochar, and extraction methods. With the decrease in lignin content of feedstocks, carbonization temperature, and acidity of extraction solution, the content of BCDOM increased. Through complexation and adsorption, protein-like components in BCDOM interact with heavy metals, promoting the adsorption and immobilization of heavy metals onto biochar. Furthermore, BCDOM enhances the adsorption of organic pollutants by biochar through π–π interactions, hydrogen bonding, and redox processes. More importantly, BCDOM promotes plant growth by enhancing microbial activities, providing nutrients, and improving soil properties. However, the transport and fate of BCDOM in soil have not been well studied, and more researches are needed to explore the interaction mechanisms between BCDOM and soil organisms.

Lead (Pb) and zinc (Zn) are widely recognized as common environmental contaminants, contributing to soil degradation and posing risks to environmental health. Combining functional carbon-based materials with microorganisms has been considered as an effective and environmentally friendly strategy for remediating Pb/Zn-contaminated soil. However, there is still a lack of understanding the connection between heavy metal immobilization and plant responses, which hampers practical applications. Here, a 90-day pot experiment was conducted to investigate the integrated effects of biochar (WS700) and microorganisms including inorganic phosphate-solubilizing bacteria (IPSB) and sulfate reducing bacteria (SRB) on Pb and Zn synchronous immobilization and the physiological responses of Brassica rapa var. chinensis (Brassica). Compared with CK, bacteria-loaded biochar treatment declined the exchangeable Pb and Zn fraction by 94.69%–98.37% and 94.55%–99.52%, while increasing the residual state Pb and Zn by 75.50%–208.58% and 96.71%–110.85%, respectively. Three amendments enhanced Brassica growth by improving total chlorophyll content and superoxide dismutase (SOD) and peroxidase (POD) activities. The bacteria-loaded biochar treatment effectively regulated stomatal conductance and reduced intercellular CO₂ concentration. Moreover, compared with CK, three amendments reduced MDA content by 28.84%, 28.30% and 41.60%, respectively, under the high concentration of Pb and Zn. The findings demonstrated the significant role of bacterial-biochar consortia in immobilizing Pb and Zn and mitigating Pb and Zn-induced stress in plants by regulating photosynthetic characteristics and antioxidant enzyme activities.

Superhydrophobic glass has inspiring development prospects in endoscopes, solar panels and other engineering and medical fields. However, the surface topography required to achieve superhydrophobicity will inevitably affect the surface transparency and limit the application of glass materials. To resolve the contradiction between the surface transparency and the robust superhydrophobicity, an efficient and low-cost laser-chemical surface functionalization process was utilized to fabricate superhydrophobic glass surface. The results show that the air can be effectively trapped in surface micro/nanostructure induced by laser texturing, thus reducing the solid-liquid contact area and interfacial tension. The deposition of hydrophobic carbon-containing groups on the surface can be accelerated by chemical treatment, and the surface energy is significantly reduced. The glass surface exhibits marvelous robust superhydrophobicity with a contact angle of 155.8° and a roll-off angle of 7.2° under the combination of hierarchical micro/nanostructure and low surface energy. Moreover, the surface transparency of the prepared superhydrophobic glass was only 5.42% lower than that of the untreated surface. This superhydrophobic glass with high transparency still maintains excellent superhydrophobicity after durability and stability tests. The facile fabrication of superhydrophobic glass with high transparency and robustness provides a strong reference for further expanding the application value of glass materials.

Efficient tool condition monitoring techniques help to realize intelligent management of tool life and reduce tool usage costs. In this paper, the influence of different wear degrees of ball-end milling cutters on the texture shape of machining tool marks is investigated, and a method is proposed for predicting the wear state (including the position and degree of tool wear) of ball-end milling cutters based on entropy measurement of tool mark texture images. Firstly, data samples are prepared through wear experiments, and the change law of the tool mark texture shape with the tool wear state is analyzed. Then, a two-dimensional sample entropy algorithm is developed to quantify the texture morphology. Finally, the processing parameters and tool attitude are integrated into the prediction process to predict the wear value and wear position of the ball end milling cutter. After testing, the correlation between the predicted value and the standard value of the proposed tool condition monitoring method reaches 95.32%, and the accuracy reaches 82.73%, indicating that the proposed method meets the requirement of tool condition monitoring.

Ferrite-rich calcium sulfoaluminate (FCSA) cement is often used in special projects such as marine engineering due to its excellent resistance of seawater attack although the cost is a little high. Ground granulated blast furnace slag (GGBS), a byproduct of industrial production, is used as a mineral admixture to reduce concrete costs and provide excellent performance. This study aimed to investigate the impact of GGBS on the hydration properties of FCSA cement in seawater. Tests were conducted on heat of hydration, compressive strength, mass change, and pH value of pore solution of FCSA cement paste with a water-to-binder ratio of 0.45. X-ray diffraction (XRD) analysis and thermogravimetric analysis were used to determine the hydration products, while mercury intrusion porosimetry (MIP) was used to measure pore structure. The results indicated that the FCSA cement hydration showed a concentrated heat release at early age. The compressive strength of specimens consistently increased over time, where seawater curing enhanced the compressive strength of control samples. The pH value of pore solution decreased to 10.7–10.9 at 90 d when cured in seawater. The primary hydration products of FCSA cement included ettringite, iron hydroxide gel (FH₃), and aluminum hydroxide gel (AH₃). Moreover, when cured in seawater, Friedel’s salt was formed, which enhanced the compressive strength of the specimen and increased its coefficient of corrosion. Seawater curing gradually increased sample mass, and GGBS refined pore structure while reducing harmful pore proportions. These results suggest that while GGBS can refine pore structure and improve certain aspects of performance, its inclusion may also reduce compressive strength, highlighting the need for a balanced approach in its use for marine applications.

Soil cement bentonite (SCB) is a common material for constructing vertical cutoff walls to prevent groundwater migration at contaminated industrial sites. However, site contaminants can degrade the durability of the cutoff wall. To enhance its performance, this study developed a silica fume-SCB (SSCB). The macroscopic and microscopic properties of SSCB were assessed by unconfined compressive strength test, variable head permeability test, X-ray diffraction (XRD), scanning electron microscopy (SEM) and nuclear magnetic resonance (NMR) spectroscopy. The correlation between its multi-scale properties was analyzed based on pore characteristics. The results indicate that increasing the silica fume substitution ratio improved SSCB strength, especially in the middle and late curing stages. Moreover, increasing the substitution ratio decreased SSCB permeability coefficient, with a more pronounced effect in earlier curing stages. Silica fume addition also refined SSCB pore structure and reduced its porosity. The fractal dimension was used to quantify SSCB pore structure complexity. Increasing silica fume content reduced small pore fractal dimension in SSCB. Concurrently, SSCB strength increased and SSCB permeability coefficient decreased. The findings of this research will demonstrate the great potential of SSCB backfill for practical applications.

Coal seam water injection in tunnels is an effective technical measure for preventing coal mine rock bursts. This study used the improved split Hopkinson pressure bar (SHPB) to apply three equal static stresses to water-saturated coal to simulate the initial stress environment of coal at different depths. Then, dynamic mechanical experiments were conducted on the saturated coal at different depths to investigate the effects of water saturation and depth on the coal samples’ dynamic mechanical properties. Under uniaxial compression and without lateral compression, the strength of coal samples decreased to varying degrees in the saturated state; under different depth conditions, the dynamic strength of coal in the saturated state decreased compared with that in the natural state. However, compared with that at 0 m, the reduction in the strength of coal under the saturated condition at 200, 400, 600, and 800 m was significantly reduced. The findings of this study provide a basic theoretical foundation for the prevention and control of dynamic coal mine disasters.

This study proposes a general imperfect thermal contact model to predict the thermal contact resistance at the interface among multi-layered composite structures. Based on the Green-Lindsay (GL) thermoelastic theory, semi-analytical solutions of temperature increment and displacement of multi-layered composite structures are obtained by using the Laplace transform method, upon which the effects of thermal resistance coefficient, partition coefficient, thermal conductivity ratio and heat capacity ratio on the responses are studied. The results show that the generalized imperfect thermal contact model can realistically describe the imperfect thermal contact problem. Accordingly, it may degenerate into other thermal contact models by adjusting the thermal resistance coefficient and partition coefficient.

The evolution of cracks in shale directly affects the efficient production of shale gas. However, there is a lack of research on the characteristics of crack initiation in deep dense shale under different stress conditions. In this work, considering the different combinations of confining pressure and bedding plane inclination angle (α), biaxial mechanical loading experiments were conducted on shale containing circular holes. The research results indicate that the confining pressure and inclination angle of the bedding planes significantly influence the failure patterns of shale containing circular holes. The instability of shale containing circular holes can be classified into five types: tensile failure along the bedding planes, tensile failure through the bedding planes, shear slip along the bedding planes, shear failure through the bedding planes, and block instability failure. Furthermore, the evolution of strain and stress fields around the circular holes was found to be the fundamental cause of variations in the initiation characteristics and locations of shale cracks. The crack initiation criterion for shale containing circular hole was established, providing a new method for evaluating the trajectory of shale hole wall fractures. This study holds significant importance for evaluating the evolution and stability of fracture networks within shale reservoirs.

This study proposes an alternative calculation mode for stresses on the slip surface (SS). The calculation of the normal stress (NS) on the SS involves examining its composition and expanding its unknown using the Taylor series. This expansion enables the reasonable construction of a function describing the NS on the SS. Additionally, by directly incorporating the nonlinear Generalized Hoke-Brown (GHB) strength criterion and utilizing the slope factor of safety (FOS) definition, a function of the shear stress on the SS is derived. This function considers the mutual feedback mechanism between the NS and strength parameters of the SS. The stress constraints conditions are then introduced at both ends of the SS based on the spatial stress relation of one point. Determining the slope FOS and stress solution for the SS involves considering the mechanical equilibrium conditions and the stress constraint conditions satisfied by the sliding body. The proposed approach successfully simulates the tension-shear stress zone near the slope top and provides an intuitive description of the concentration effect of compression-shear stress of the SS near the slope toe. Furthermore, compared to other methods, the present method demonstrates superior processing capabilities for the embedded nonlinear GHB strength criterion.

The influence of ramps on the transient rolling contact characteristics and damage mechanisms of switch rails remains unclear, presenting substantial challenges to the safety of railway operations. To this end, this paper constructs a transient rolling contact finite element model of the wheel-rail in switch under different ramps using ANSYS/LSDYNA method, and analyzes the tribology and damage characteristics when the wheel passes through the switch at a uniform speed. Our research findings reveal that the vibration induced in the switch rail during the wheel load transfer process leads to a step-like increase in the contact force. Moreover, the interaction between the wheel and the rail primarily involves slip contact, which may significantly contribute to the formation of corrugations on the switch rail. Additionally, the presence of large ramps exacerbates switch rail wear and rolling contact fatigue, resulting in a notable 13.2% increase in switch rail damage under 40‰ ramp conditions compared to flat (0‰ ramp) conditions. Furthermore, the large ramps can alter the direction of crack propagation, ultimately causing surface spalling of the rail. Therefore, large ramps intensify the dynamic interactions during the wheel load transfer process, further aggravating the crack and spalling damage to the switch rails.

Urban air pollution has brought great troubles to physical and mental health, economic development, environmental protection, and other aspects. Predicting the changes and trends of air pollution can provide a scientific basis for governance and prevention efforts. In this paper, we propose an interval prediction method that considers the spatio-temporal characteristic information of PM_2.5 signals from multiple stations. K-nearest neighbor (KNN) algorithm interpolates the lost signals in the process of collection, transmission, and storage to ensure the continuity of data. Graph generative network (GGN) is used to process time-series meteorological data with complex structures. The graph U-Nets framework is introduced into the GGN model to enhance its controllability to the graph generation process, which is beneficial to improve the efficiency and robustness of the model. In addition, sparse Bayesian regression is incorporated to improve the dimensional disaster defect of traditional kernel density estimation (KDE) interval prediction. With the support of sparse strategy, sparse Bayesian regression kernel density estimation (SBR-KDE) is very efficient in processing high-dimensional large-scale data. The PM_2.5 data of spring, summer, autumn, and winter from 34 air quality monitoring sites in Beijing verified the accuracy, generalization, and superiority of the proposed model in interval prediction.