The grouted bolt, combining rock bolting with grouting techniques, provides an effective solution for controlling the surrounding rock in deep soft rock and fractured roadways. It has been extensively applied in numerous deep mining areas characterized by soft rock roadways, where it has demonstrated remarkable control results. This article systematically explores the evolution of grouted bolting, covering its theoretical foundations, design methods, materials, construction processes, monitoring measures, and methods for assessing its effectiveness. The overview encompassed several key elements, delving into anchoring theory and grouting reinforcement theory. The new principle of high pretensioned high-pressure splitting grouted bolting collaborative active control is introduced. A fresh method for dynamic information design is also highlighted. The discussion touches on both conventional grouting rock bolts and cable bolts, as well as innovative grouted rock bolts and cables characterized by their high pretension, strength, and sealing hole pressure. An examination of the merits and demerits of standard inorganic and organic grouting materials versus the new inorganic–organic composite materials, including their specific application conditions, was conducted. Additionally, the article presents various methods and instruments to assess the support effect of grouting rock bolts, cable bolts, and grouting reinforcement. Furthermore, it provides a foundation for understanding the factors influencing decisions on grouted bolting timing, the sequence of grouting, the pressure applied, the volume of grout used, and the strategic arrangement of grouted rock bolts and cable bolts. The application of the high pretensioned high-pressure splitting grouted bolting collaborative control technology in a typical kilometer-deep soft rock mine in China—the soft coal seam and soft rock roadway in the Kouzidong coal mine, Huainan coal mining area, was introduced. Finally, the existing problems in grouted bolting control technology for deep soft rock roadways are analyzed, and the future development trend of grouted bolting control technology is anticipated.
Phosphogypsum (PG), a hard-to-dissipate by-product of the phosphorus fertilizer production industry, places strain on the biogeochemical cycles and ecosystem functions of storage sites. This pervasive problem is already widespread worldwide and requires careful stewardship. In this study, we review the presence of potentially toxic elements (PTEs) in PG and describe their associations with soil properties, anthropogenic activities, and surrounding organisms. Then, we review different ex-/in-situ solutions for promoting the sustainable management of PG, with an emphasis on in-situ cemented paste backfill, which offers a cost-effective and highly scalable opportunity to advance the value-added recovery of PG. However, concerns related to the PTEs’ retention capacity and long-term effectiveness limit the implementation of this strategy. Furthermore, given that the large-scale demand for ordinary Portland cement from this conventional option has resulted in significant CO2 emissions, the technology has recently undergone additional scrutiny to meet the climate mitigation ambition of the Paris Agreement and China’s Carbon Neutrality Economy. Therefore, we discuss the ways by which we can integrate innovative strategies, including supplementary cementitious materials, alternative binder solutions, CO2 mineralization, CO2 curing, and optimization of the supply chain for the profitability and sustainability of PG remediation. However, to maximize the co-benefits in environmental, social, and economic, future research must bridge the gap between the feasibility of expanding these advanced pathways and the multidisciplinary needs.
Traditional research believes that the filling body can effectively control stress concentration while ignoring the problems of unknown stability and the complex and changeable stress distribution of the filling body-surrounding rock combination under high-stress conditions. Current monitoring data processing methods cannot fully consider the complexity of monitoring objects, the diversity of monitoring methods, and the dynamics of monitoring data. To solve this problem, this paper proposes a phase space reconstruction and stability prediction method to process heterogeneous information of backfill-surrounding rock combinations. The three-dimensional monitoring system of a large-area filling body-surrounding rock combination in Longshou Mine was constructed by using drilling stress, multipoint displacement meter, and inclinometer. Varied information, such as the stress and displacement of the filling body-surrounding rock combination, was continuously obtained. Combined with the average mutual information method and the false nearest neighbor point method, the phase space of the heterogeneous information of the filling body-surrounding rock combination was then constructed. In this paper, the distance between the phase point and its nearest point was used as the index evaluation distance to evaluate the stability of the filling body-surrounding rock combination. The evaluated distances (ED) revealed a high sensitivity to the stability of the filling body-surrounding rock combination. The new method was then applied to calculate the time series of historically ED for 12 measuring points located at Longshou Mine. The moments of mutation in these time series were at least 3 months ahead of the roadway return dates. In the ED prediction experiments, the autoregressive integrated moving average model showed a higher prediction accuracy than the deep learning models (long short-term memory and Transformer). Furthermore, the root-mean-square error distribution of the prediction results peaked at 0.26, thus outperforming the no-prediction method in 70% of the cases.
This study introduces a coupled electromagnetic–thermal–mechanical model to reveal the mechanisms of microcracking and mineral melting of polymineralic rocks under microwave radiation. Experimental tests validate the rationality of the proposed model. Embedding microscopic mineral sections into the granite model for simulation shows that uneven temperature gradients create distinct molten, porous, and nonmolten zones on the fracture surface. Moreover, the varying thermal expansion coefficients and Young’s moduli among the minerals induce significant thermal stress at the mineral boundaries. Quartz and biotite with higher thermal expansion coefficients are subjected to compression, whereas plagioclase with smaller coefficients experiences tensile stress. In the molten zone, quartz undergoes transgranular cracking due to the α–β phase transition. The local high temperatures also induce melting phase transitions in biotite and feldspar. This numerical study provides new insights into the distribution of thermal stress and mineral phase changes in rocks under microwave irradiation.
In combination with theoretical calculations, experiments were conducted to investigate the evolution behavior of nonmetallic inclusions (NMIs) during the manufacture of large-scale heat-resistant steel ingots using 9CrMoCoB heat-resistant steel and CaF2–CaO–Al2O3–SiO2–B2O3 electroslag remelting (ESR)-type slag in an 80-t industrial ESR furnace. The main types of NMI in the consumable electrode comprised pure alumina, a multiphase oxide consisting of an Al2O3 core and liquid CaO–Al2O3–SiO2–MnO shell, and M23C6 carbides with an MnS core. The Al2O3 and MnS inclusions had higher precipitation temperatures than the M23C6-type carbide under equilibrium and nonequilibrium solidification processes. Therefore, inclusions can act as nucleation sites for carbide layer precipitation. The ESR process completely removed the liquid CaO–Al2O3–SiO2–MnO oxide and MnS inclusion with a carbide shell, and only the Al2O3 inclusions and Al2O3 core with a carbide shell occupied the remelted ingot. The M23C6-type carbides in steel were determined as Cr23C6 based on the analysis of transmission electron microscopy results. The substitution of Cr with W, Fe, or/and Mo in the Cr23C6 lattice caused slight changes in the lattice parameter of the Cr23C6 carbide. Therefore, Cr21.34Fe1.66C6, (Cr19W4)C6, Cr18.4Mo4.6C6, and Cr16Fe5Mo2C6 can match the fraction pattern of Cr23C6 carbide. The Al2O3 inclusions in the remelted ingot formed due to the reduction of CaO, SiO2, and MnO components in the liquid inclusion. The increased Al content in liquid steel or the higher supersaturation degree of Al2O3 precipitation in the remelted ingot than that in the electrode can be attributed to the evaporation of CaF2 and the increase in CaO content in the ESR-type slag.
A 3D mathematical model was proposed to investigate the molten steel–slag–air multiphase flow in a two-strand slab continuous casting (CC) tundish during ladle change. The study focused on the exposure of the molten steel and the subsequent reoxidation occurrence. The exposure of the molten steel was calculated using the coupled realizable k–ε model and volume of fluid (VOF) model. The diffusion of dissolved oxygen was determined by solving the user-defined scalar (UDS) equation. Moreover, the user-defined function (UDF) was used to describe the source term in the UDS equation and determine the oxidation rate and oxidation position. The effect of the refilling speed on the molten steel exposure and dissolved oxygen content was also discussed. Increasing the refilling speed during ladle change reduced the refilling time and the exposure duration of the molten steel. However, the elevated refilling speed enlarged the slag eyes and increased the average dissolved oxygen content within the tundish, thereby exacerbating the reoxidation phenomenon. In addition, the time required for the molten steel with a high dissolved oxygen content to exit the tundish varied with the refilling speed. When the inlet speed was 3.0 m·s−1 during ladle change, the molten steel with a high dissolved oxygen content exited the outlet in a short period, reaching a maximum dissolved oxygen content of 0.000525wt%. Conversely, when the inlet speed was 1.8 m·s−1, the maximum dissolved oxygen content was 0.000382wt%. The refilling speed during the ladle change process must be appropriately decreased to minimize reoxidation effects and enhance the steel product quality.
The global importance of lithium-ion batteries (LIBs) has been increasingly underscored with the advancement of high-performance energy storage technologies. However, the end-of-life of these batteries poses significant challenges from environmental, economic, and resource management perspectives. This review paper focuses on the pyrometallurgy-based recycling process of lithium-ion batteries, exploring the fundamental understanding of this process and the importance of its optimization. Centering on the high energy consumption and emission gas issues of the pyrometallurgical recycling process, we systematically analyzed the capital-intensive nature of this process and the resulting technological characteristics. Furthermore, we conducted an in-depth discussion on the future research directions to overcome the existing technological barriers and limitations. This review will provide valuable insights for researchers and industry stakeholders in the battery recycling field.
Given the carbon peak and carbon neutrality era, there is an urgent need to develop high-strength steel with remarkable hydrogen embrittlement resistance. This is crucial in enhancing toughness and ensuring the utilization of hydrogen in emerging iron and steel materials. Simultaneously, the pursuit of enhanced metallic materials presents a cross-disciplinary scientific and engineering challenge. Developing high-strength, toughened steel with both enhanced strength and hydrogen embrittlement (HE) resistance holds significant theoretical and practical implications. This ensures secure hydrogen utilization and further carbon neutrality objectives within the iron and steel sector. Based on the design principles of high-strength steel HE resistance, this review provides a comprehensive overview of research on designing surface HE resistance and employing nanosized precipitates as intragranular hydrogen traps. It also proposes feasible recommendations and prospects for designing high-strength steel with enhanced HE resistance.
Compared with the conventional Charpy impact test method, the oscillographic impact test can help in the behavioral analysis of materials during the fracture process. In this study, the trade-off relationship between the strength and toughness of a DZ2 axle steel at various tempering temperatures and the cause of the improvement in impact toughness was evaluated. The tempering process dramatically influenced carbide precipitation behavior, which resulted in different aspect ratios of carbides. Impact toughness improved along with the rise in tempering temperature mainly due to the increase in energy required in impact crack propagation. The characteristics of the impact crack propagation process were studied through a comprehensive analysis of stress distribution, oscilloscopic impact statistics, fracture morphology, and carbide morphology. The poor impact toughness of low-tempering-temperature specimens was attributed to the increased number of stress concentration points caused by carbide morphology in the small plastic zone during the propagation process, which resulted in a mixed distribution of brittle and ductile fractures on the fracture surface.
Attaining a decarbonized and sustainable energy system, which is the core solution to global energy issues, is accessible through the development of hydrogen energy. Proton-exchange membrane water electrolyzers (PEMWEs) are promising devices for hydrogen production, given their high efficiency, rapid responsiveness, and compactness. Bipolar plates account for a relatively high percentage of the total cost and weight compared with other components of PEMWEs. Thus, optimization of their design may accelerate the promotion of PEMWEs. This paper reviews the advances in materials and flow-field design for bipolar plates. First, the working conditions of proton-exchange membrane fuel cells (PEMFCs) and PEMWEs are compared, including reaction direction, operating temperature, pressure, input/output, and potential. Then, the current research status of bipolar-plate substrates and surface coatings is summarized, and some typical channel-rib flow fields and porous flow fields are presented. Furthermore, the effects of materials on mass and heat transfer and the possibility of reducing corrosion by improving the flow field structure are explored. Finally, this review discusses the potential directions of the development of bipolar-plate design, including material fabrication, flow-field geometry optimization using three-dimensional printing, and surface-coating composition optimization based on computational materials science.
To study the atmospheric aging of acrylic coatings, a two-year aging exposure experiment was conducted in 13 representative climatic environments in China. An atmospheric aging evaluation model of acrylic coatings was developed based on aging data including 11 environmental factors from 567 cities. A hybrid method of random forest and Spearman correlation analysis was used to reduce the redundancy and multicollinearity of the data set by dimensionality reduction. A semi-supervised collaborative trained regression model was developed with the environmental factors as input and the low-frequency impedance modulus values of the electrochemical impedance spectra of acrylic coatings in 3.5wt% NaCl solution as output. The model improves accuracy compared to supervised learning algorithms model (support vector machines model). The model provides a new method for the rapid evaluation of the aging performance of acrylic coatings, and may also serve as a reference to evaluate the aging performance of other organic coatings.
Rare-earth silicates are promising environmental barrier coatings (EBCs) that can protect SiCf/SiCm substrates in next-generation gas turbine blades. Notably, RE2Si2O7 (RE = Yb and Ho) shows potential as an EBC due to its coefficient of thermal expansion (CTE) compatible with substrates and high resistance to water vapor corrosion. The target operating temperature for next-generation turbine blades is 1400°C. Corrosion is inevitable during adhesion to molten volcanic ash, and thus, understanding the corrosion behavior of the material is crucial to its reliability. This study investigates the high-temperature corrosion behavior of sintered RE2Si2O7 (RE = Yb and Ho). Samples were prepared using a solid-state reaction and hot-press method. They were then exposed to volcanic ash at 1400°C for 2, 24, and 48 h. After 48 h of exposure, volcanic ash did not react with Yb2Si2O7 but penetrated its interior, causing damage. Meanwhile, Ho2Si2O7 was partially dissolved in the molten volcanic ash, forming a reaction zone that prevented volcanic ash melts from penetrating the interior. With increasing heat treatment time, the reaction zone expanded, and the thickness of the acicular apatite grains increased. The Ca:Si ratios in the residual volcanic ash were mostly unchanged for Yb2Si2O7 but decreased considerably over time for Ho2Si2O7. The Ca in volcanic ash was consumed and formed apatite, indicating that RE3+ ions with large ionic radii (Ho > Yb) easily precipitated apatite from the volcanic ash.
Specific grades of high-entropy alloys (HEAs) can provide opportunities for optimizing properties toward high-temperature applications. In this work, the Co-based HEA with a chemical composition of Co47.5Cr30Fe7.5Mn7.5Ni7.5 (at%) was chosen. The refractory metallic elements hafnium (Hf) and molybdenum (Mo) were added in small amounts (1.5at%) because of their well-known positive effects on high-temperature properties. Inclusion characteristics were comprehensively explored by using a two-dimensional cross-sectional method and extracted by using a three-dimensional electrolytic extraction method. The results revealed that the addition of Hf can reduce Al2O3 inclusions and lead to the formation of more stable Hf-rich inclusions as the main phase. Mo addition cannot influence the inclusion type but could influence the inclusion characteristics by affecting the physical parameters of the HEA melt. The calculated coagulation coefficient and collision rate of Al2O3 inclusions were higher than those of HfO2 inclusions, but the inclusion amount played a larger role in the agglomeration behavior of HfO2 and Al2O3 inclusions. The impurity level and active elements in HEAs were the crucial factors affecting inclusion formation.
Thermal insulation materials play an increasingly important role in protecting mechanical parts functioning at high temperatures. In this study, a new porous high-entropy (La1/6Ce1/6Pr1/6Sm1/6Eu1/6Gd1/6)PO4 (HE (6RE1/6)PO4) ceramics was prepared by combining the high-entropy method with the pore-forming agent method and the effect of different starch contents (0–60vol%) on this ceramic properties was systematically investigated. The results show that the porous HE (6RE1/6)PO4 ceramics with 60vol% starch exhibit the lowest thermal conductivity of 0.061 W·m−1·K−1 at room temperature and good pore structure stability with a linear shrinkage of approximately 1.67%. Moreover, the effect of large regular spherical pores (>10 µm) on its thermal insulation performance was discussed, and an optimal thermal conductivity prediction model was screened. The superior properties of the prepared porous HE (6RE1/6)PO4 ceramics allow them to be promising insulation materials in the future.
In recent years, ultra-wide bandgap β-Ga2O3 has emerged as a fascinating semiconductor material due to its great potential in power and photoelectric devices. In semiconductor industrial, thermal treatment has been widely utilized as a convenient and effective approach for substrate property modulation and device fabrication. Thus, a thorough summary of β-Ga2O3 substrates and devices behaviors after high-temperature treatment should be significant. In this review, we present the recent advances in modulating properties of β-Ga2O3 substrates by thermal treatment, which include three major applications: (i) tuning surface electrical properties, (ii) modifying surface morphology, and (iii) oxidating films. Meanwhile, regulating electrical contacts and handling with radiation damage and ion implantation have also been discussed in device fabrication. In each category, universal annealing conditions were speculated to figure out the corresponding problems, and some unsolved questions were proposed clearly. This review could construct a systematic thermal treatment strategy for various purposes and applications of β-Ga2O3.
Nonreciprocity of thermal metamaterials has significant application prospects in isolation protection, unidirectional transmission, and energy harvesting. However, due to the inherent isotropic diffusion law of heat flow, it is extremely difficult to achieve nonreciprocity of heat transfer. This review presents the recent developments in thermal nonreciprocity and explores the fundamental theories, which underpin the design of nonreciprocal thermal metamaterials, i.e., the Onsager reciprocity theorem. Next, three methods for achieving nonreciprocal metamaterials in the thermal field are elucidated, namely, nonlinearity, spatiotemporal modulation, and angular momentum bias, and the applications of nonreciprocal thermal metamaterials are outlined. We also discuss nonreciprocal thermal radiation. Moreover, the potential applications of nonreciprocity to other Laplacian physical fields are discussed. Finally, the prospects for advancing nonreciprocal thermal metamaterials are highlighted, including developments in device design and manufacturing techniques and machine learning-assisted material design.
Rare-earth nickelates (RENiO3) show widely tunable metal-to-insulator transition (MIT) properties with ignorable variations in lattice constants and small latent heat across the critical temperature (T MIT). Particularly, it is worth noting that compared with the more commonly investigated vanadium oxides, the MIT of RENiO3 is less abrupt but usually across a wider range of temperatures. This sheds light on their alternative applications as negative temperature coefficient resistance (NTCR) thermistors with high sensitivity compared with the current NTCR thermistors, other than their expected use as critical temperature resistance thermistors. In this work, we demonstrate the NTCR thermistor functionality for using the adjustable MIT of Nd xSm1−xNiO3 within 200–100 K, which displays larger magnitudes of NTCR (e.g., more than 7%/K) that is unattainable in traditional NTCR thermistor materials. The temperature dependence of resistance (R–T) shows sharp variation during the MIT of Nd xSm1−xNiO3 with no hysteresis via decreasing the Nd content (e.g., x ≤ 0.8), and such a R–T tendency can be linearized by introducing an optimum parallel resistor. The sensitive range of temperature can be further extended to 210–360 K by combining a series of Nd xSm1−xNiO3 with eight rare-earth co-occupation ratios as an array, with a high magnitude of NTCR (e.g., 7%–14%/K) covering the entire range of temperatures.
Bioderived carbon materials have garnered considerable interest in the fields of microwave absorption and shielding due to their reproducibility and environmental friendliness. In this study, KOH was evenly distributed on biomass Tremella using the swelling induction method, leading to the preparation of a three-dimensional network-structured hierarchical porous carbon (HPC) through carbonization. The achieved microwave absorption intensity is robust at −47.34 dB with a thin thickness of 2.1 mm. Notably, the widest effective absorption bandwidth, reaching 7.0 GHz (11–18 GHz), is attained at a matching thickness of 2.2 mm. The exceptional broadband and reflection loss performance are attributed to the 3D porous networks, interface effects, carbon network defects, and dipole relaxation. HPC has outstanding absorption characteristics due to its excellent impedance matching and high attenuation constant. The uniform pore structures considerably optimize the impedance-matching performance of the material, while the abundance of interfaces and defects enhances the dielectric loss, thereby improving the attenuation constant. Furthermore, the impact of carbonization temperature and swelling rate on microwave absorption performance was systematically investigated. This research presents a strategy for preparing absorbing materials using biomass-derived HPC, showcasing considerable potential in the field of electromagnetic wave absorption.
Herein, two asymmetric hexacyclic fused small molecule acceptors (SMAs), namely BP4F-HU and BP4F-UU, were synthesized. The elongated outside chains in the BP4F-UU molecule played a crucial role in optimizing the morphology of blend film, thereby improving charge mobility and reducing energy loss within the corresponding film. Notably, the PM6:BP4F-UU device exhibited a higher open-circuit voltage (V oc) of 0.878 V compared to the PM6:BP4F-HU device with a V oc of 0.863 V. Further, a new wide bandgap SMA named BTP-TA was designed and synthesized as the third component to the PM6:BP4F-UU host binary devices, which showed an ideal complementary absorption spectrum in PM6:BP4F-UU system. In addition, BTP-TA can achieve efficient intermolecular energy transfer to BP4F-UU by fluorescence resonance energy transfer (FRET) pathway, due to the good overlap between the photoluminescence (PL) spectrum of BTP-TA and the absorption region of BP4F-UU. Consequently, ternary devices with 15wt% BTP-TA exhibits broader photon utilization, optimal blend morphology, and reduced charge recombination compared to the corresponding binary devices. Consequently, PM6:BP4F-UU:BTP-TA ternary device achieved an optimal power conversion efficiency (PCE) of 17.83% with simultaneously increased V oc of 0.905 V, short-circuit current density (J sc) of 26.14 mA/cm2, and fill factor (FF) of 75.38%.
Layered oxide is a promising cathode material for sodium-ion batteries because of its high-capacity, high operating voltage, and simple synthesis. Cycling performance is an important criterion for evaluating the application prospects of batteries. However, facing challenges, including phase transitions, ambient stability, side reactions, and irreversible anionic oxygen activity, the cycling performance of layered oxide cathode materials still cannot meet the application requirements. Therefore, this review proposes several strategies to address these challenges. First, bulk doping is introduced from three aspects: cationic single doping, anionic single doping, and multi-ion doping. Second, homogeneous surface coating and concentration gradient modification are reviewed. In addition, methods such as mixed structure design, particle engineering, high-entropy material construction, and integrated modification are proposed. Finally, a summary and outlook provide a new horizon for developing and modifying layered oxide cathode materials.
The worldwide proliferation of portable electronics has resulted in a dramatic increase in the number of spent lithium-ion batteries (LIBs). However, traditional recycling methods still have limitations because of such huge amounts of spent LIBs. Therefore, we proposed an ecofriendly and sustainable double recycling strategy to concurrently reuse the cathode (LiCoO2) and anode (graphite) materials of spent LIBs and recycled LiCoPO4/graphite (RLCPG) in Li+/PF6 − co-de/intercalation dual-ion batteries. The recycle-derived dual-ion batteries of Li/RLCPG show impressive electrochemical performance, with an appropriate discharge capacity of 86.2 mAh·g−1 at 25 mA·g−1 and 69% capacity retention after 400 cycles. Dual recycling of the cathode and anode from spent LIBs avoids wastage of resources and yields cathode materials with excellent performance, thereby offering an ecofriendly and sustainable way to design novel secondary batteries.
Aqueous zinc-ion batteries (AZIBs) show great potential for applications in grid-scale energy storage, given their intrinsic safety, cost effectiveness, environmental friendliness, and impressive electrochemical performance. However, strong electrostatic interactions exist between zinc ions and host materials, and they hinder the development of advanced cathode materials for efficient, rapid, and stable Zn-ion storage. MXenes and their derivatives possess a large interlayer spacing, excellent hydrophilicity, outstanding electronic conductivity, and high redox activity. These materials are considered “rising star” cathode candidates for AZIBs. This comprehensive review discusses recent advances in MXenes as AZIB cathodes from the perspectives of crystal structure, Zn-storage mechanism, surface modification, interlayer engineering, and conductive network design to elucidate the correlations among their composition, structure, and electrochemical performance. This work also outlines the remaining challenges faced by MXenes for aqueous Zn-ion storage, such as the urgent need for improved toxic preparation methods, exploration of potential novel MXene cathodes, and suppression of layered MXene restacking upon cycling, and introduces the prospects of MXene-based cathode materials for high-performance AZIBs.