Abstract: Deep mining is an inevitable trend in the exploitation of metal resources owing to their increasing demand. The multifield coupling environment for deep mining, which includes a high in situ stress, high temperature, high hydraulic pressure, and strong disturbances from excavations, pose considerable challenges to mining safety and efficiency. Intelligent or smart mining is a key to revolutionizing the mining industry. Therefore, for promoting the intelligent transformation and upgrading of the mining industry, the study of intelligent mining technologies for deep mines has a considerable strategic significance. Based on the strategic background of mining deep resources, this study investigated future technological strategies for exploiting deep metal resources toward 2035. Global technological trends on deep intelligent mining subject to multifield couplings were analyzed using technological forecasting methods. Hot research topics and advanced technologies related to intelligent deep mining subject to multifield couplings were obtained. Based on experts’ opinions and analyses, key fundamental theories and techniques for intelligent deep mining toward 2035 were proposed. There are three promising mining methods: unconventional deep mining methods without blasting, continuous pastes backfill mining in deep mines, integration of mining, mineral beneficiation and backfill. Advanced technologies can be divided into three types: (1) smart perception of the deep mining environment, (2) intelligent working during deep mining, and (3) intelligent control of mining systems. Type 1 includes intelligent in situ stress measurements, the intelligent identification of rock mass structures, microseismic monitoring and early warning of disasters, intelligent underground space exploration, and intelligent perception of man–machine systems. Type 2 includes intelligent full-section well excavation equipment, intelligent support technology and equipment, intelligent continuous mining technology and equipment, unmanned intelligent mining equipment, and intelligent lifting technology and equipment. Type 3 includes the intelligent control of the filling system, intelligent control of the microclimate in tunnels, flexible data communication on working faces, intelligent scheduling for the entire life cycle of deep mining, intelligent scheduling of the entire mining process, integrated platform for mining management, and big data analysis for deep mining. Technological strategies, key tasks, and a technical roadmap for 2035 were proposed for intelligent deep mining subject to multifield couplings in China, including development targets and demands, fundamental research areas, and key technologies and equipment. Technological development procedures to transform deep mining technologies and improve mining intelligence were presented. Some suggestions were provided in terms of policies, industries, technologies, and talent for intelligent deep mining.
Abstract: With the increasing scale of underground space projects in China, the types of underground space development and utilization are characterized by diversification, deepening, and complexity. Moreover, many underground space projects have been transferred from the construction stage to the long-term, safe, and stable operation stage. At present, and even in the future, how to maintain the safety and stability of underground space engineering during excavation, construction, and service is an important topic that must be considered. Based on the analysis of the complex geological conditions faced by underground space engineering, the influence of construction quality on service safety, deterioration of structural performance caused by environmental factors and sudden disasters, and extensive development of underground space, this study identified three key scientific problems of service safety in underground space engineering, namely, the law of damage and deterioration of structural materials under multi-field coupling, dynamic fatigue damage characteristics of structures under cyclic dynamic load, and interaction between support and surrounding rock. This study summarized and commented on the failure process of rock and concrete in special environments, dynamic mechanical properties of rock and concrete under dynamic load, damage test and evaluation method of rock mass under explosion load, rock and concrete fatigue, surrounding rock stability analysis, support mechanism of underground space engineering, and other related research work and latest progress. Finally, this study specified the future development trend of this subject and the basic research work that needs to be focused on and strengthened, that is, developing new green building materials for underground space engineering, establishing a new support design theory, conducting underground space service safety research based on artificial intelligence, and building a full life-cycle underground space service risk analysis, prevention and control system, so as to provide scientific ideas and feasible methods to ensure the service safety of urban underground space engineering.
Abstract: Tailings and waste rock produced in metal mines are the most common industrial solid wastes all over the world, resulting in serious environmental and safety issues. Cemented paste backfill (CPB) is widely used for tailings management and stope treatment. CPB of total solid waste (TSW-CPB) was proposed on the basis of CPB of full-tailings. In the TSW-CPB process, thickened full-tailings, waste rock, and slag are mixed to prepare a paste that is filled into the stope. TSW-CPB can avoid the collapse of a stope, failure of the tailings storage facility, and landslide of a waste-rock yard, achieving the goal of “total waste to cure three harms.” The effects of solid fraction (SF), waste rock dosage (WRD), and glue powder dosage (GPD) on the slump (S), yield stress (τ0), uniaxial compressive strength (UCS), and bleeding rate (BR) were investigated through orthogonal experiments. According to the scope of technical indicators specified in the National Standard of the People’s Republic of China “Technical specification for the total tailings paste backfill (GB/T 39489—2020),” the overall desirability function approach was used to conduct multiple response optimization of key TSW-CPB performance indicators. TSW-CPB was shown to have similar fluidity, transportation performance, mechanical properties, and bleeding performance to the CPB of full-tailings. The SF, WRD, and GPD affect the S, τ0, UCS, and BR of TSW-CPB considerably. The SF has the most important influence on S and τ0, while GPD has the most substantial impact on UCS and BR. Multiple response optimization yielded SF = 79.31%, WRD = 18.86%, and GPD = 3:20, with S = 25.45 cm, τ0 = 100.49 Pa, UCS = 3.55 MPa, and BR = 1.50% as the corresponding responses. The optimal results can provide references for practical application, and the overall desirability function approach can be used in other mines to optimize multi objective CPB.
Abstract: To ensure the stability of an overlying roadway in close proximity to a 1000-m deep coal seam, this work, through theoretical analysis and numerical simulation, studies the deformation and failure mechanism, failure types, and prevention methods of the overlying roadway while mining a lower coal seam. Based on the study of mining conditions and overburdened space structures formed through mining, the deformation and failure law of the roadway in the strike and dip directions is obtained. Moreover, the stress evolution law of roadway deformation and failure is obtained by studying the influence of different mining stages and filling rates of the lower face on the mining of the overlying roadway. Results show that there are two types of potential roadway deformation and failure: (1) roadway section reduction failure and (2) roadway strike step subsidence failure. The fundamental cause of the deformation and failure of the overlying roadway is the influence of the large buried depth, strong mining stress, and unequal distance between the coal seam and roadway. The direct causes are the sudden increase in the stress of the roadway surrounding the rock and the subsidence of the key strata. In the mining process, when the mining range of the working face is more than 400 m, the roadway section reduction failure and strike ladder subsidence failure superimpose each other, inducing further roadway failure. Therefore, a scheme of partial filling and strengthening of the roadway along the working face is designed. Field measurements revealed that the above scheme can meet the stability requirements of the overlying roadway and the high efficiency and yield of the underlying working face. The results provide some references for the safe mining of coal in the 1000-m deep coal seam.
Abstract: The demands for deep underground mining and construction are increasing with the continuing development of society and the economy. Deep underground chambers function as primary elements in deep underground mining and other subsurface facilities. Therefore, rational designs of such chambers would play a pivotal role in construction safety and economic efficiency. The primary goal of this study is to reveal the relation between the in situ stress field and axes of an elliptical cross section of an underground chamber. Based on the rock deformation and damage, a numerical model is developed to define the heterogeneous damage evolution near the chamber. In this parametric study, we characterized the damage evolution in response to the chamber’s cross-sectional shape, lateral stress coefficient, and tectonic stress azimuth, thus introducing the critical lateral stress coefficient to define the chamber stability. Furthermore, a case study of a ?2000 m chamber in the Sanshandao gold mine was conducted using the proposed model to optimize the shape, design, and location analysis of the underground mining chamber. Simulation outcomes show that the damaged area and stress concentration near the chamber are minimized when the axis ratio is equal to the lateral stress coefficient. The damaged area is determined by the in situ stress configuration; a high lateral stress coefficient sees a pronounced increment in the tension stress inside the roof and floor of the chamber, resulting in an exponential enlargement of the damaged area. Compared with the shallow underground chamber, the deep chamber is more sensitive to an increase in the lateral stress coefficient. With an increase in depth, the critical lateral stress coefficient gradually decreased to 1. The larger horizontal tectonic stress in the deep strata causes damage accumulation in the roof and the floor, encouraging rock outbursts in the damaged zones. To conclude, to optimize the design and minimize the outburst hazard for a deep underground chamber, the chamber’s cross-sectional shape, axes ratio, and direction must reasonably reflect the in situ stress field.
Abstract: Methane is an important high-quality clean energy that mainly comes from the decomposition of organic waste, natural gas, fossil fuel extracts, etc. Recycling it from a gaseous mixture is beneficial for environmental protection and energy utilization and development. The new coal-based activated carbon is a widely used storage material for methane because of its economic benefit and practicality; thus, coal-based activated carbon modification is greatly significant. This research aims to further reveal the methane adsorption mechanism of coal-based activated carbon by studying the influence of acidic, basic, and combined modifications on methane adsorption and seek a more efficient means of coal-based activated carbon modification. The coal-based activated carbon made from anthracite coal was processed through acidic, basic, and combined modifications. In addition, the physical and chemical structures of the coal-based activated carbon surface and the adsorption ability of methane were precisely analyzed through low-temperature liquid nitrogen adsorption, Fourier infrared spectroscopy, and high-pressure methane adsorption experiments. The characteristics of adsorption thermodynamics and kinetics were also determined by using the Langmuir adsorption isotherm model and the Freundlich model for data fitting. The results show a significant increase in the specific surface area and pore volume of the coal-based activated carbon after combined modification. The specific surface area and the total pore volume increases by 66.66% and 30.89%, respectively. The methane adsorption capacity of the coal-based activated carbon also significantly improved after combined modification. Methane adsorption increases by 25.686%. In addition, both the pore structure and the contained functional groups on the surface jointly determine the methane adsorption, which is mainly affected by the polarity of the surface functional groups rather than the pore structure.
Abstract: Thin slab casting and direct rolling (TSCR) technology has experienced 30 years of development since the first production line was commissioned in 1989. Owing to consistent and successful exploration and innovation by engineers and researchers, rapid progress in TSCR technology has been witnessed. Under the background of carbon neutrality, the steel industry encounters tremendous pressure for low carbon emissions. As one of the representative near-net-shape steel manufacturing technologies, TSCR technology has attracted extensive attention. This article reviewed the development history and evolution of critical process equipment for the TSCR technology. According to the continuous extent of the manufacturing process, the TSCR technology can be classified into the following three generations, i.e., batch rolling, semiendless rolling, and endless rolling. With the improvement of the continuity of TSCR technology, the production line is greatly shortened, especially the third-generation technology, the endless strip production line. Meanwhile, the increase in continuity substantially increases productivity, production yield, and energy efficiency and expands the thinnest strip thickness down to 0.6 mm. Additionally, the specific characteristics of processing and physical metallurgy of TSCR technology were analyzed. Based on its characteristics of rapid solidification, heavy reduction per rolling pass, and uniform temperature distribution, TSCR technology was suggested to produce special steel, high strength steel, silicon steel, and thin gauge products. New advances on the development of representative products for TSCR technology, e.g., medium- and high-carbon steels, high-strength hot-rolled steels, and silicon steels, and their practical application status were discussed. Finally, this work envisaged the future development directions of TSCR technology and proposed that making the process more concise and continuous, developing product-oriented production lines, and coupling intelligent manufacturing with TSCR technology will be important development directions in the future.
Abstract: In 2020, the Chinese government proposed the goals of “peaking carbon dioxide emissions” in 2030 and reaching “carbon neutrality” in 2060, with the expectation of enhancing the optimization of industrial structure and energy structures as well as promoting the development of control technologies and new energy technologies for pollution prevention. Carbon emissions lead to global warming, glacier melting, sea level rising, and other unexpected climate changes. It is highly significant to develop sustainable technologies for treating or converting carbon dioxide and low value-added solid carbon wastes and other carbon pollutants to achieve solid-state valuable carbon products. Carbon pollutants are also regarded as secondary carbon resources, which provide sufficient raw materials for developing carbon materials. Graphitization alters the chemical structure of carbonaceous materials. However, there are still some critical issues in the traditional graphitization processes, such as high processing temperature, insufficient graphitization, and emission of greenhouse gas. In recent years, an efficient and environmentally friendly method for electrochemical graphitization in molten salts has been established, which can be used to directly convert carbon pollutants into high graphitized products. In this review, there are three main topics: (1) process flow, (2) structure characteristics, (3) conversion mechanism of electrochemical graphitization. The use of carbon nanomaterials in secondary batteries such as lithium-ion batteries and aluminum-ion batteries has been discussed for a potential application. As a result, the efficient strategies of transforming and utilizing abundant secondary carbon resources to achieve the applications have also been analyzed. Finally, the ultimate goals for bridging the gap between molten salt electrochemical graphitization and engineering of graphitized products have been identified. Further efforts should be made to develop large-scale electrolytic technology with low energy consumption, build advanced in-situ characterization technology and quantitative analysis method for high-temperature molten salt electrochemistry, and understand the mechanism of electrochemical graphitization at the microscale.
Abstract: Aluminum is the second largest metallic material after steel. It is also an indispensable and basic raw material in the economic development of a country. Besides, aluminum is known as a green strategic material due to its efficient recycling performance. China’s aluminum industry has made remarkable achievements in technological innovation and scientific progress through decades of development. However, in recent years, the huge production scale of the aluminum industry has increasingly prominent problems of limited resources, rising energy costs, and environmental pollution. It should be realized that the development and survival of China’s aluminum industry have reached a very critical period. This paper comprehensively studied the current situation of the production and technology of China’s aluminum metallurgical industry. Major contradictions and challenges faced by the development of China’s aluminum industry in the fields of resources, energy, and the environment were revealed. In addition, the competitiveness of the production cost for Chinese alumina refining and aluminum smelting in the world was compared and analyzed. It is shown that the major factors restricting China’s aluminum industry development include the lack of high-quality bauxite resources, high energy costs, the requirement for further improvement of the production technology, and no effective treatment of solid and hazardous wastes. Hence, a development strategy for China’s aluminum industry was proposed, which includes the strict control of the production capacity without out-of-order expansion and establishment of a reasonable industry arrangement, optimization of the resource and energy supply structure, improvement of the production core competitiveness by implementing high-quality, energy-saving, and low consumption strategy, and realizing standardized discharge and resource utilization of waste gas emissions, wastewater, and solid disposals from China’s aluminum industry. The research results of this work are of great significance to the industrial structure adjustment and high-quality, sustainable development for China’s aluminum industry.
Abstract: Additive manufacturing technology is a method of manufacturing parts that are stacked layer by layer through the principle of discrete stacking, which is different from traditional subtractive manufacturing. It has been widely concerned due to its advantages of short process flow, high material-utilization rate, and highly flexible manufacturing. Additive metal manufacturing is the most important branch of additive manufacturing technology. Its forming parts have high complexity, showing excellent mechanical properties than ordinary castings. After more than 20 years of development, it has been widely used in aerospace, medical, energy, and other related fields. In the current mainstream metal material in the manufacturing process, the main use of high-energy beam-melting metal powders results in extremely high overcooling, whereas cold fine grains exhibit special precipitation and increase the mechanical properties of the material. However, there are still doubts about the corrosion performance of metal additive manufacturing parts in the service process. The mechanism of the corrosion effect of special microstructures and precipitation relative to materials in the service process is still unclear. Therefore, it is urgent to review the systematic research of the corrosion resistance of high-energy beam metal additive manufacturing parts. Corrosion resistance is also one of the key factors for metal additive manufacturing products to occupy a place in the market and should be paid attention to. Therefore, this article summarized the current research progress on the corrosion performance of metal additive manufacturing workpieces on three commonly used metal additive manufacturing technologies: laser melting, electron beam melting, and directional metal deposition. The residual stress, grain size, precipitated phase, and anisotropy affect the corrosion resistance behavior. The influence mechanism of the parameter optimization and heat-treatment process on the corrosion resistance of the material was analyzed. Finally, the prospects of improving the corrosion resistance of metal additive manufacturing products were discussed.
Abstract: Sodium-ion batteries (SIBs) are highly desirable energy storage devices because of their low cost, high safety, and environmental compatibility. Therefore, SIBs have wide application prospects in the fields of large-scale energy storage and electric vehicles. SIBs have a similar energy storage mechanism as that of lithium-ion batteries (LIBs) and can be fabricated using existing LIB production equipment. Thus, SIBs are the most promising alternative to LIBs. However, the radius of Na+ is ~34% larger than that of Li+; therefore, many electrode materials developed for LIBs are unsuitable for SIBs. The exploration of novel electrode materials for SIBs has garnered significant interest in recent years. Among various candidate anode materials for SIBs, red phosphorus is a promising material owing to its ultrahigh theoretical specific capacity (2596 mA·h·g–1), suitable oxidation–reduction potential (0.4 V vs Na/Na+), and abundance. However, the capacity utilization, long-term cycle stability, and rate performance of red phosphorous are limited due to its low intrinsic conductivity and a large volume effect upon sodium storage. At present, an effective approach for the modification of red phosphorus anodes is to prepare nanosized red phosphorus (NRP). Miniaturizing red phosphorus prevents structural damage via large volume changes during charge/discharge processes and also shortens Na+ transmission distances, which enables high electrochemical activity and long-term cycling stability. Herein, recent studies on NRP preparation for advanced SIBs are extensively reviewed. NRP preparation methods typically include ball milling, vaporization condensation, and chemical deposition. Other novel approaches such as thermal reduction, vapor growth, and solvothermal synthesis have also been reported. Ball milling is straightforward and scalable; however, strict guidelines are required to prevent the red phosphorus from burning and exploding, and slight oxidation and particle aggregation are unavoidable. Vaporization-condensation strategies are suitable for the uniform deposition of NRP onto a matrix but are limited by low phosphorus loading and residual white phosphorus. Chemical deposition methods are promising due to their simplicity, control over particle size, and scalability. There are two main chemical deposition strategies, i.e., the reduction of phosphorus-containing compounds and the dissolution and deposition of phosphorus amines. The former method is facile and compatible with ambient temperatures, while the latter method is safe, cost effective, and has high yields. Further studies should focus on morphology design, increasing phosphorus loading, and developing novel chemical reduction methods. We hope that this review promotes the development of red phosphorous anodes for application in SIBs.
Abstract: Driven by the national strategic goal of “emission peak and carbon neutrality”, developing grid-scale energy storage systems (ESSs) for high-efficiency utilization of renewable clean energy is of great importance and urgency. Currently, lithium-ion batteries (LIBs) are being widely used in portable electronics and electric vehicles markets due to their high energy density and long cycling life. Nevertheless, the ever-increasing price and uneven distribution of lithium resources limit the further applications of LIBs for large-scale ESS. Recently, sodium-ion batteries (SIBs) have gained tremendous attention as promising large-scale energy storage devices and low-speed electric vehicle power sources, owing to the low-cost and abundant sodium reserves. However, the larger size and heavier mass of Na+ than those of Li+ commonly lead to sluggish reaction kinetics, severe volume expansion, and the undesirable structural failure of electrode materials upon charge/discharge, which hinder the commercial value of SIBs. Leveraging high-performance cathode materials is expected to boost the development of SIBs because cathodes largely determine the cost and electrochemical performance of batteries. Among the reported cathode candidates, layered oxide materials hold great potential due to their high capacity and a facile synthesis process; however, these materials face some challenges such as low capacity retention and poor air stability. Recently, exploring appropriate methods to strengthen the structural stability and further enhance the energy density of layered oxides has become an emerging research hotspot. In this regard, various strategies, such as element composition and relative content manipulation and microstructure and surface/interface modulation, have been proposed. In this review, typical modification methods for improving the Na-storage performance of layered oxide cathodes are comprehensively summarized. From the perspective of component design, the effects of different doping elements and doping sites on the capacity and cycling life are discussed. In addition, the basic principle of anionic redox reaction to offer extra capacity is elucidated, and the doping strategies for enhancing the anionic redox reversibility are outlined. From the perspective of structure design, the recent progresses on the preparation of composite phase materials and microstructures design are introduced. From the perspective of surface design, the functional mechanism of metal oxides and phosphates as coating layers to improve the structural stability and rate performance is explored. Finally, the challenging issues facing layered sodium oxide cathodes and possible remedies in the future are discussed. We believe that this review will shed light on the development of advanced layered oxide cathode materials for SIBs.
Abstract: High-power and fast-discharging lithium-ion battery, which can be used in smart power grids, rail transits, electromagnetic launch systems, aerospace systems, and so on, is one of the key research directions in the field of lithium-ion batteries and has attracted increasing attention in recent years. To obtain lithium-ion batteries with a high power density, the cathode materials should possess high voltage and high electronic/ionic conductivity, which can be realized by selecting high-voltage materials and modifying them to improve the voltage and reduce the battery’s internal resistance. Currently, the cathode materials of high-power lithium-ion batteries mainly include high-voltage LiCoO2, LiNi0.5Mn1.5O4, and Li(NiCoMn)O2 materials. Meanwhile, the anode materials include carbon- and Ti-based materials and metal oxides. This paper reviews the research on the modification of these materials, such as element doping and surface coating, which have gained considerable attention nowadays, as well as some new types of anode materials that exhibit excellent electrochemical properties. In terms of the negative electrode, the prelithiation process is one of the effective means to improve the power performance of a lithium-ion battery. This process’s significance is to compensate the consumption of Li+ and reduce the potential of the negative electrode to the working range for improving the platform voltage of the battery and improving the power density and energy density. This paper summarizes several commonly used prelithiation methods of the lithium-ion battery. Finally, the lithium salts, solvents, and additives for the electrolytes of lithium-ion batteries are introduced on the basis of their classification, properties, and performances. Several new types of lithium salts and additives are mentioned herein, such as lithium bis(fluorosulfonyl)imide, lithium bis(oxalate)borate, and tetramethylene sulfone. Furthermore, this paper summarizes several common power density test methods of lithium-ion batteries and prospects the research of high-power lithium-ion batteries. As a matter of fact, the power performance of lithium-ion batteries is gaining increasing attention and has truly achieved considerable improvement in recent years.
Abstract: The development of alternative energy resources is of great significance to alleviate the global energy issue. The direct methanol fuel cell (DMFC) is gradually becoming one of the most promising portable energy technologies due to the merits of low operating temperature, high energy density, and low pollutant emission. Currently, its commercialization process mainly depends on the kinetics of the anodic methanol oxidation reaction (MOR). Noble metals have been widely studied as the most commonly used anode catalysts. However, high prices and limited reserves have severely hindered their further development. In addition, the active surface of Pt is susceptible to the poison of COads intermediate products, leading to the rapid loss of the catalytic activity due to blocked Pt sites. Considering the above problems, the design and development of low Pt or non-Pt nanocatalysts with an excellent antipoisoning ability have become very important. Transition metals have been widely used as promising substitutes for noble metal catalysts because of their abundant reserves, low price, and high catalytic activity. Among the transition metals studied, Ni, Cu, and Co have attracted sustained attention because of their high corrosion resistance. Owing to the ligand effect and synergistic effect, the addition of transition metals can effectively weaken the adsorption of COads intermediates on Pt sites. At the same time, non-noble transition metals are easy to form MOOH active species, which promote the oxidation of COads intermediates. Besides, methanol electrooxidation performance is closely related to the shape, structure, and composition of transition metals. From the principle of DMFC anode electrocatalysis, this review summarized the research progress of transition metal-based catalysts (transition metal-noble metal catalysts, transition metal catalysts, and self-supporting catalysts) in MOR. More importantly, the effects of the nanocatalyst composition, porous structure, high-index surface, crystal defects, and vertex enhancement on its electrochemical properties were emphasized. Finally, opportunities and challenges faced by transition metal-based electrocatalysts in DMFC were discussed.
Abstract: With the increasing consumption of fossil fuels, severe energy shortages and environmental issues are fast approaching. Therefore, the development of green energy resources is urgently appealed. Among them, the sunlight-driven production of hydrogen fuel with suitable photocatalysts is regarded as one of the potential strategies to meet the sustainable energy demand in the future. However, photocatalysis still faces significant uncertainties mainly because of the notorious photogenerated electron-hole (e-h) recombination and low carriers’ mobility. To achieve high photocatalytic performance, it is essential to tailor the spatial charge separation and fast charge transfer via electronic and structural manipulation of photocatalysts. As one of the hot-spot photocatalysts, graphitic phase carbon nitride (g-C3N4) has received tremendous attention in the study of solar-to-fuel (STF) conversion and carbon dioxide reduction reactions (CO2RR), owing to intrinsic merits, such as metal-free components, low-cost resources, good stability, and visible light response. Recently, considerable progress has been achieved to improve the photocatalytic STF efficiency of g-C3N4-based materials by developing strategies of structures and electric configurations engineering. In this study, different modification methods for g-C3N4 were systematically reviewed from the perspective of defects control to provide a new understanding of its structure-function relationship. Particularly, this study was composed in detail from three aspects to demonstrate the latest research progress of g-C3N4 photocatalytic materials. First, different routes toward g-C3N4 with different shapes were introduced, including 1D, 2D, and 3D. Second, doping effects and defect control on the separation and transfer of photogenerated electron-hole pairs were carefully reviewed. Finally, heterojunctions based on g-C3N4 were summarized, highlighting the Z-scheme heterojunction. In addition, some future directions and challenges for the enhancement of the photocatalytic efficiency upon g-C3N4 were pointed out according to our understanding of photocatalytic water splitting.
Abstract: Nonoxide ceramics (NOCs) as representative high-temperature structural materials are widely applied in various key fields, such as metallurgy, electric power, and chemical industry, owing to combined excellent characteristics including high strength, lightweight, good thermal shock resistance, and erosion resistance. In practical applications, NOCs are often exposed to high temperatures containing oxygen; thus, they are inevitably confronted with the oxidation issue. In addition, NOCs are mostly used as lining materials for high-temperature containers and transmission components for high-temperature devices, in which they are also subjected to external loads. Simultaneously, internal stress will be generated inside the oxide film during oxidation, owing to the density difference and thermal expansion coefficient difference between the oxidation products and substrate. The coupled effect of oxidation and complex stresses accelerates the degradation of high-temperature performance and ultimately reduces the service life of NOCs, even causing severe industrial accidents. Therefore, studying the oxidation of NOCs under complex conditions is essential. However, limited by the high temperature and long serving time, an experimental approach to the oxidation of NOCs remains a challenge. By comparison, kinetic models based on specific reaction principles and different assumptions have become an effective tool for understanding and analyzing the oxidation of NOCs. This article compares the oxidation mechanism and corresponding kinetic models of NOCs under stressfree and stress conditions. Through comparing and analyzing the application effects of different models, the effect of stress on oxidation of NOCs is determined from a quantitative point, and the oxidation kinetic models of NOCs considering stress are preliminarily established, which can provide a scientific model for further recognition of service behavior of NOCs under complex conditions and provide effective theoretical guidance for improvement of the service life of materials.
Abstract: The development of biomass fuels is of great significance for reducing excessive dependence on fossil resources and global warming. Lignin is a complex aromatic biopolymer that is abundant in nature and can be used to produce high-value biomass fuels. However, due to its complex structure, the use of lignin to produce biomass fuels needs a variety of chemical reactions and catalysts, and the intermediates and products need to be separated many times, resulting in a low yield of products. Multifunctional catalysts can catalyze two or more chemical reactions at the same time; therefore, using them can simplify the preparation process and increase the yield of products. This paper reviewed the research progress of multifunctional catalysts used in the process of lignin hydrocracking, monomer hydrodeoxygenation, and monomer upgrading to polycyclic high-value products, including sulfide catalysts, noble metal elemental catalysts, non-noble metal elemental and alloy catalysts, and phosphide catalysts. Additionally, this work emphasized the interaction between hydrogenation centers (Ru, Pt, Pd, Co, Mo, and Ni) and acid centers (Al2O3, ZrO2, NbOPO4, zeolite, and mesoporous silicate) in hydrocracking and hydrodeoxygenation. Based on these, the difficulties of the current reactions were then summarized, and the next technical developing directions were anticipated, including those of the development of biomass fuel synthesis methods with more mild reaction conditions and preparation of catalysts with higher activity, higher hydrothermal stability, and lower price. This paper hopes that new methods can reduce the amount of hydrogen, decrease the reaction temperature, and converse lignin to high-value fuels in a one-pot method. Moreover, most research on biomass fuels is still in the laboratory research stage. To realize the large-scale industrial production of biomass fuels and replace petroleum fuels, more in-depth research, perfect supporting facilities, and relevant policies and measures are needed.
Abstract: As powerful techniques for multidisciplinary research, the neutron and synchrotron radiation sources have the advantages of deep penetration and high brilliance, providing advanced and powerful tools for characterizing microstructures and revealing deformation/damage micromechanisms of materials. For research on engineering materials, such as advanced steel, superalloy, titanium alloy, and aluminum alloy, it is necessary to develop advanced in-situ microstructure and stress characterization methods to reveal the evolution of the multiscale microstructures and stress fields during preparation and service and investigate the micromechanical behaviors, including deformation damage and phase transformation, under complex external factors, such as temperature, stress, electric, and magnetic fields. The basic principles of quantitative characterization of texture and multiscale stress using neutron and X-ray diffraction (XRD) techniques were introduced in this paper. The global development and status of advanced characterization techniques based on neutron and synchrotron radiation sources were expounded. The advantages of neutron and synchrotron radiation techniques were also analyzed. The application of neutron and synchrotron-based XRD techniques in the research of structural engineering materials and components, thermoelastic martensitic transformation, and new structural materials were reviewed. The use of neutron diffraction and HE-XRD techniques on structural engineering materials mainly focuses on multiphase microstructure evolution, intergranular and interphase stress distribution in elastic/plastic zone during deformation, and temperature/stress-induced phase transformation behaviors. The microscopic stress measurement is crucial for verifying the micromechanical model of engineering structural material, which is closely related to the texture evolution during the deformation and phase transformation. The simultaneous acquisition of microscopic stress and macroscopic stress can provide essential data for the service reliability and failure evaluation standards of engineering structural materials/components. Using the μXRD characterization method with submicron resolution, through the combination of monochromatic and polychromatic diffraction analysis, the precise characterization of large stress gradient and slight orientation gradient, caused by the dislocation structures inside the grain, can be realized to achieve submicron damage evaluation. The research on thermoelastic martensitic transformation by neutron scattering (diffraction) and HE-XRD technology includes external field-assisted thermoelastic martensitic transformation, narrow hysteresis thermoelastic martensitic transformation, and colossal elastocaloric effect. Neutron diffraction and HE-XRD techniques have advantages in studying emerging structural materials, such as high-entropy alloys and heterogeneous materials, which often have complex microstructures and exhibit unique mechanical behaviors and are important for revealing their deformation and damage mechanisms. The neutron and synchrotron-based technology, combined with in-situ environmental devices, can be used to measure and analyze the multiscale microstructures/stress and service damage behaviors of key engineering components in a near-service environment. Finally, the development and application of characterization techniques based on neutron and synchrotron radiation sources have prospects.
Abstract: Due to the closed environment with high temperature and pressure in the continuous casting (CC) process, numerical simulation technology with flexible control and low cost of phenomena in the CC mold has been a research hotspot. The multiphase flow, heat transfer, solidification of steel and slag, and other complex interaction in the mold are some of the simulation difficulties. Various physical models have been established in recent studies to obtain the reactions and effects of the different phases. However, the influence of different models on the simulation results is rarely studied. In the current study, a three-dimensional (3D) mathematical model, coupled with the large eddy simulation (LES) turbulent model and volume of fluid (VOF) multiphase model, was established to investigate the multiphase flow, slag-steel interface level fluctuation, and slag entrainment in the mold of a steel bloom CC with mold electromagnetic stirring (M-EMS). The air?slag?steel three-phase flow, slag?steel two-phase flow, and steel single-phase flow were compared. An industrial computerized tomography (CT) was used to detect the large entrainment slag inclusions in blooms with different stirring current intensities. With a 150-A current intensity and a 2-Hz frequency electromagnetic stirring at the mold, the multiphase flows are approximately identical for the three models, although different at the slag?steel interface. The speed on the top surface of the single-phase model is higher than that of the multiphase models. The level fluctuation of the two-phase model is slightly more severe than that of the three-phase model, and the net slag entrainment rates of the two-phase and three-phase models are 0.00118 and 0.00040 kg·s?1, respectively. The turbulence kinetic energy at the slag?steel interface of the two-phase model is significantly greater than that of the three-phase model because the turbulence kinetic energy can not be dissipated, unlike that in the actual process. Thus, the predicated slag entrainment obtained by the two-phase model is higher. On increasing the stirring current intensity to 300 A, the net slag entrainment rate is 5 times and 15 times higher for the two-phase and three-phase model higher than that under 150 A; when the current frequency increases to 4 Hz, the net slag entrainment rate of the two-phase model varies little, while that of the three-phase model becomes 1/3 of that under 2 Hz. To accurately simulate and predict the slag entrainment phenomena at the CC mold, the air?slag?steel three-phase multiphase model should be mandatory.
Abstract: High-speed continuous casting is the theme for developing a new generation of high-efficiency continuous casting technology as well as a high-efficiency and green steelmaking production line. Presently, the actual casting speed for slabs in China is no more than 1.8 m·min?1, and it is in the range of 1.2–1.4 m·min?1 for continuous casting of peritectic steel. With the increase in the casting speed, the negative factors affecting the solidification in continuous casting mold become more evident, and the lubrication between mold copper plate and solidifying shell deteriorates. The friction force increases due to the increase of heat flux and decrease of mold flux consumption. Hence, the thickness of solidifying shell reduces and becomes nonuniform, decreasing its ability to resist all types of stress and strain during casting. Thus, the occurrence of breakout and cracks with high frequency greatly influences production. The technical issue of high-speed casting and the key to making it a reality should be resolved to ensure homogeneous growth. In this paper, the behavior of heat transfer and solidification in slab mold with high-speed casting for peritectic steel was analyzed. The effect of casting speed on the interfacial heat transfer resistance and the distribution of temperature and stress for solidifying shells in mold were investigated. It was found that the interfacial heat resistance increased evidently as the casting speed was greater than 1.6 m·min?1. The thickness of solidified shell at the exit of the mold was reduced by approximately 10%, as the casting speed increased from 1.4 m·min?1 to 1.6 m·min?1 and 1.8 m·min?1, making it more dangerous for breakout. The relative technologies such as the shape, flux, oscillation, and surface fluctuation for mold with homogenous solidification were presented and discussed. The optimization of mold inner cavity fitting for the growth of solidifying shell should be considered first for the uniformity control of peritectic steel solidification in a high-speed continuous casting mold. It is critical to design mold flux that adjusts to the solidification characteristics of peritectic steel. Moreover, the control of strand bulging is the key to stabilizing the mold surface.
Abstract: The worldwide energy crisis necessitates the urgent need for energy conservation, especially in buildings whose energy consumption has already surpassed that of transportation and industrial sectors. Most of the energy loss in buildings is related to windows because their heat transfer coefficient is different from other building fabrics. Therefore, smart window technologies are proposed to eliminate energy usage, among which cholesteric liquid crystals show great potential due to their electrically controlled bistable properties. Cholesteric liquid crystals are characterized by two stable states: (1) the planar state that shows selective reflection or high light transmittance and (2) focal conic state that scatters incident light and shows opaque appearance. To realize a bistable state in which both the planar state and the focal conic state could be maintained without an external field is of vital importance for the application, since it could save considerable energy. In this study, oily streak defects and stability of the focal conic state are controlled by introducing a type of bent molecular materials. Effects of various factors on the bistable states are investigated, and the potential applications are explored. Results show that the bent molecule CB7CB could diminish the oily streak defects in the planar state and reduce the domain size of the focal conic state because it has a smaller bent elastic constant. The electro-optical test implies that bistable states are acquired in the composite containing CB7CB. Factors such as the anchoring strength of the alignment layer and cell thickness are then investigated and results reveal that strong anchoring and thinner cell thickness are not favored by the focal conic state. Moreover, bistable states could be stabilized by introducing a small amount of polymer followed by polymerization. Based on the above guidelines, colorless and colorful bistable light shutters are demonstrated, which could maintain both transparent and opaque states without any external electric field. The light shutter saves more energy than the one based on polymer-dispersed liquid crystals. Other potential applications, such as bistable displays and electronic label could also be realized based on the bistable property.
Abstract: In the area of “carbon peaking and carbon neutralization,” changing energy structure from primary energy to new energy is an extremely important issue. Due to the intermittent and fluctuating characteristics of new energy, energy storage technology has proven a viable solution to this issue thus has attracted extensive attention. As a key to energy storage technology, the problem of the low thermal conductivity of phase change materials (PCMs) requires immediate attention. Erythritol is a high enthalpy phase change material commonly used in low-to-medium temperature processes. Its thermal conductivity of only 0.7 W?m–1?K–1 seriously hinders its energy utilization efficiency in practical application. In this paper, erythritol is the main research focus, and single-walled carbon nanotubes (CNTs) of ultra-high thermal conductivity are used as thermal conductivity reinforcements. The effects of length, mass fraction, and the distribution of CNTs on the thermal conductivity of erythritol/CNT composite PCMs were studied by means of molecular dynamics simulation. When the axial lengths of the CNTs were less than their phonon mean free paths, the thermal conductivity of the composite PCMs increased with increasing CNT axial length and mass fraction, although clear anisotropy was exhibited. Due to the introduction of erythritol–CNTs interfacial thermal resistance, the radial thermal conductivity of the composite materials was lower than that of pure erythritol. When CNTs were randomly distributed in erythritol, the anisotropy of thermal conductivity was significantly improved, as was thermal conductivity in all directions. Comparing the phonon vibration densities of the states of erythritol and CNT before and after recombination, it was found that, due to the interaction between the two, the phonon vibration of CNT was suppressed, and the phonon heat transport in erythritol was excited, thus improving thermal conductivity.
Abstract: In recent years, Chinese iron and steel enterprises have mainly adopted the “sampling after the event” method to inspect the product quality before it leaves the factory. Due to the inability to achieve quality inspection for all products, customers often claim and return defective products, leading to major economic losses in steel enterprises. To improve the stability and reliability of product quality, the use of machine learning methods to realize the online monitoring, optimization, and preset of product quality is the key technology to be solved in iron and steel enterprises. Therefore, the online identification and diagnosis of abnormal product quality based on the soft hypersphere, online optimization of the process parameters based on manifold learning and process specification formulation based on the multivariate statistical process control were proposed. In this study, integrated methods of online monitoring, diagnosis, and optimization of product quality were proposed in which the abnormal point of the product quality by the soft hypersphere method, based on the support vector data description, was identified online, and the process parameters were diagnosed through the contribution chart. Optimizing in real time, abnormal process parameters via a local projective transformation of neighbor points was then achieved. The process parameter setting model based on manifold learning by multiclass neighborhoods to extract the manifold of process parameters was established. Meanwhile, the process specification model, based on the maximum inner rectangle of the soft hypersphere, was established to obtain an effective control interval of the process parameters. Through system integration with the proposed methods and using industrial internet technology and big data analysis methods, the system of intelligent online monitoring of product quality has been successfully developed. At present, the system has been applied to more than ten production lines in iron and steel enterprises. The accuracy rate of online quality determination is 99.2%, and the online detection time is less than 0.1 s.
Abstract: As an emerging concept, metaverse has attracted extensive attention from industry, academia, media, and the public, prompting many companies worldwide about its layout. However, the layout is inseparable from strong technical support. In the early developmental stage of the metaverse, its technology is the core foundation. The development and innovation of technology are the top priority. This paper dived into the metaverse from the technical view. First, the paper discussed the metaverse’s concept and connotation from the perspective of science and technology and summarized the opinions of practitioners, experts, and scholars about it. Second, it outlined the key technologies of the metaverse, including network and operating technology (5G, 6G, Internet of things, cloud computing, fog computing, and edge computing); management technology (energy consumption, resource, session, and spatiotemporal consistency managements); virtual real object connection, modeling and management technology (Internet of X, identity modeling, social computing, and decentralized management); and virtual real space interaction and fusion technology (extend reality, video game, and brain–computer interface). The metaverse is not a novel technology but an all-inclusive internet application. The progress and development of technology play a solid foundation for realizing and applying the metaverse. At the same time, metaverse development also promotes upgrading existing technologies to drive the product, scenario, and application innovation. Finally, this paper looked into many challenges facing metaverse development. Metaverse enables the connection and integration of the real and virtual worlds. It may become a novel form of social development and change people’s way of life. Meanwhile, the growth of the metaverse concept, its development speed, ultimate form, and even its impact on philosophy, culture, society, and economic governance, as well as human beings, are unknown. By implementing a metaverse prototype, the enabling economy will also be of major interest. Moreover, the government adheres to policy guidelines to enable the real economy with technology, which will still apply in the metaverse era. No matter what trend we are in, we should have a clear understanding, make rational decisions, and steadily explore the metaverse!
Abstract: This review outlined recent developments in deep learning time series forecasting technology for the needs of industrial applications. With the advances in industrial automation, the storage and analysis of massive production data have become possible. Traditional mechanism modeling methods based on statistics encounter difficulties in dealing with high-dimensional industrial problems. Thus, time series forecasting for complex processes and products has played an important role in industrial scenarios, such as device modeling, production forecasting, remaining life prediction, and precise control, thereby receiving considerable attention from both academia and industry. To methodically review the time series forecasting method and its industrial applications, this review first introduced the three types of time series forecasting, namely, statistical learning, integrated learning, and deep learning, and compared their ease of use, complexity, and applicability issues. Focusing on industrial data analysis and decision-making, this review analyzed the three types of deep learning models, namely, recurrent neural network, convolutional neural network, and encoder–decoder network. The advantages and disadvantages of these three types of models and the applicable industrial environment were given, and how they can be embedded in industrial application sites to reduce costs and improve production efficiency was described. Afterward, to evaluate the performance of different algorithms clearly and comprehensively, statistical metrics and loss functions for the point prediction sequence and shape (motif) prediction problems were presented. At the same time, this review compiled classic public datasets of the industry for researchers to quickly find authoritative assessment data for an industry sector or issue. Taking mining and metallurgy in the process industry as examples, this review presented some widespread problems in this field, such as nonlinearity, long time delays, and unobservability of variables. This review also showed how deep-learning-based time series forecasting techniques can solve the aforementioned problems, build soft sensors, create digital twins, and achieve the visualization of complex processes. This review revealed that the application of deep learning in the process industry requires highly robust and strongly interpretable or explainable algorithms. For the robustness problem, the use of the ordinary differential equation model and Kalman filter method to solve the modeling of irregularly sampled time series and the use of the deep learning method to detect online sensor abnormalities were proposed. For the interpretability problem, sample-based, structure-based interpretable, and external co-explanation methods were introduced. This review also analyzed how explainable techniques can be applied to industrial deep learning models. Finally, the future directions of time series research were discussed in terms of both deep learning methods and industrial applications.
Abstract: “Flapping wing” is a mechanism observed in the flight of birds, insects, and bats. The lift and thrust for a flight are generated by the active movement of wings. It was first specifically designed by Da Vinci. With good concealment and maneuverability advantages, the bionic flapping wing has become the hotspot in the field of aerial vehicles at home and abroad in recent years. Due to its high degree of bionic appearance and ultra-low flight noise, the bionic flapping-wing aerial vehicle has important applications in the military and civilian fields. Because of a low Reynolds number, unsteady aerodynamics, and other issues, such as flexible deformation of the wing and so on, the study of a bionic flapping-wing aerial vehicle is quite different from that of a conventional fixed-wing aerial vehicle. The three methods used in the study of a flapping-wing aerial vehicle are aerodynamic calculations, wind tunnel experiments, and outside flight tests. In terms of aerodynamic calculation, the theory and method of an unsteady aerodynamic design and optimization are still inadequate at present. The outside flight test cannot accurately measure the complex aerodynamic force of the aerial vehicle and cannot conduct quantitative analysis as well as research on the aerial vehicle. As the wind tunnel experiment can simulate a real flight, the data obtained is more reliable, can be analyzed, and studied quantitatively. Therefore, the wind tunnel experiment has become an effective method to study a flapping-wing aerial vehicle. Researchers at home and abroad have conducted several experimental studies on a bionic flapping-wing aerial vehicle using a wind tunnel. This paper first introduced the composition and classification of a wind tunnel and then introduced the research status of the wind tunnel experiment, covering the bird-like and insect-like flapping-wing aerial vehicles in detail. Finally, this paper provided suggestions on the possible research directions to the wind tunnel experiment of the bionic flapping-wing aerial vehicle, such as research on how the multi-wing and the feather structure of the wings affect the performance of the bionic flapping-wing aerial vehicle.
Abstract: The aggravating trend of an aging population impacts industrial production and social services. Robots are expected to be able to work not only in highly structured manufacturing environments but also in human-inhabited environments, and hence, need to have more sophisticated cognitive abilities. They have to be able to operate safely and efficiently in unstructured, populated environments and achieve high-level collaboration and communication with humans. Collaborative robots, also referred to as cobots, are a new class of industrial robots that can interact with humans in shared spaces or work safely in the vicinity of humans. Collaborative robots are generally lightweight and edge-rounded with multiple degrees of freedom. Besides, multiple sensors must be integrated and limitations of speed and force must be set to ensure their behavior safety. Collaborative robots have shown good application prospects in many fields, such as flexible manufacturing, social services, medical care, disaster prevention, and antiepidemic. They have received wide attention in the industry and academia. Collaborative robots require the integration of multimodal sensory information and intelligent control methods to ensure efficient collaborative behavior. Human-robot collaboration (HRC) considers key issues attached to how safe and efficient collaboration between cobots and humans can be achieved, involving robotics, cognitive sciences, machine learning, artificial intelligence, philosophy, and others. HRC has been included in the key support research programs such as Smart Manufacturing 2025 and the Development Plan of New Generation Artificial Intelligence, recently becoming an important research direction in the field of intelligent robotics with a wide range of applications. This paper introduces several domestic and foreign collaborative robots and intelligent control methods of collaborative robots, including control methods based on perception information, high accuracy tracking control methods, and interaction control methods. It also discusses human intention estimation and robot skill learning methods for efficient human-robot collaboration. Finally, future directions of collaborative robots are explored.
Abstract: Compared with a single unmanned aerial vehicle (UAV), a large-scale UAV swarm can accomplish the unavailable, complex, and “1 + 1 > 2” tasks of traditional UAVs. To prevent the UAV swarm from falling into the dilemma of disorganized derailment and mission failure, higher requirements for the robustness and organizational scheduling capability of the UAV swarm were proposed. As one of the important components of the autonomous cooperative control technology of UAV swarms, task allocation refers to certain environmental situation information and UAV swarm status to maximize the overall efficiency of the swarm. To solve the task allocation problem of the UAV swarm, a UAV swarm task allocation algorithm based on the alternating direction method of multipliers (ADMM) network potential game theory was proposed. The ADMM is a typical algorithm that uses the idea of “divide and conquer.” The ADMM adopts the decomposition–coordination process, which coordinates the solutions of each subproblem step by step to determine the global optimum. In terms of problem modeling and algorithm design, the network potential game theory can solve the conflict and cooperation between multiple agents effectively. By combining the advantages of the ADMM and network potential game theory, UAV swarm task allocation can be divided into two parts: local and global benefits optimization. Firstly, considering the different resource constraints and execution capability factors of the UAV swarm, the task allocation problem was formulated as the problem of finding a minimum under inequality constraints, and the game model of the UAV swarm task allocation problem was constructed based on the network potential game theory. Based on the game model of UAV swarm task allocation, the equivalence of the optimum UAV swarm task allocation strategy and the Nash equilibrium solution of the evolutionary network was analyzed. Secondly, according to the UAV capability and task set characteristics, the local optimum execution efficiency of each UAV was determined using the ADMM. Moreover, each UAV was defined as a rational player, the local benefit maximization task combination of each UAV was used as the initial task allocation scheme, and the task allocation problem was transformed and solved by using the Nash equilibrium solution of the network potential game. Each UAV adjusts its strategy based on the information on the interaction between individuals in the neighborhood to maximize the global task benefits. Finally, the simulation experiments verified that the proposed UAV swarm task allocation algorithm can converge to the optimal solution stably within a limited step and assign all task target points without conflict. The feasibility and effectiveness of the method were also verified. The comprehensive verification platform for the 3D simulation process of UAV swarm task allocation and execution was given in the form of real-time deduction.
Abstract: China proposes to achieve carbon peaking and carbon neutralization by 2030 and 2060, respectively. As a heavily carbon-based fuel industry, the carbon dioxide emission of the iron and steel industry is lower than that of the power and transportation industries. In 2020, the carbon dioxide emissions of China’s steel industry were approximately 1.98 billion tons, accounting for more than 18% of the national carbon dioxide emissions. To achieve the “carbon neutral” emission reduction target of the steel industry, the three parts of the entire process of steel production, i.e., “source–process–end,” need to be involved in the exploration of low-carbon technologies. This study summarized the low-carbon technology measures of foreign low-carbon dioxide emission projects and major domestic steel companies’ carbon peaking and carbon neutralization projects; divided and classified the low-carbon technologies in today’s steel industry from three levels, i.e., carbon dioxide emission reduction, zero carbon dioxide emission, and negative carbon dioxide emission; and summarized the carbon dioxide emission reduction, maturity, and promotion time of each low-carbon technology. In terms of carbon dioxide emission reduction, carbon dioxide emissions in the production process of the steel industry were reduced by optimizing processes and process reengineering, such as blast furnace top gas circulation technology. In terms of zero carbon dioxide emissions, hydrogen or clean electricity was used to reduce or replace coal or coke with high carbon dioxide emission factors to reduce carbon dioxide emissions from the source, such as hydrogen metallurgical technology. In terms of negative carbon dioxide emissions, carbon dioxide capture was mainly conducted in the high carbon dioxide emission intensity blast furnace ironmaking process, green recycling was performed in the steel plant, and chemical coproduction was implemented outside the plant to produce high value-added chemical products, such as methanol and ethanol. Finally, geological storage of carbon dioxide on steel near the oil field was implemented to reduce carbon dioxide emissions.
Abstract: With the rapid development of semiconductor and electronics technologies, high-integration and high-performance microelectronic devices play more important roles in industrial fields, such as the aeronautics and astronautics, energy, medical, and automobile fields. To avoid thermal failure in high heat flux conditions, effective thermal management of microelectronic devices is critical. Conventional air and liquid cooling approaches suffer from not only high power consumption but also low heat dissipation efficiency, considerably limiting the stability and reliability of microelectronic devices. In recent years, researchers proposed many passive (such as nanofluids, surface roughness, and heating element structures) and active (such as the acoustic, electric, and magnetic fields) heat transfer enhancement approaches. Because of its low cost, flexible control, and diverse forms, the nanofluid approach has attracted considerable attention. To solve the low thermal conductivity issue of conventional working fluids (such as water, ethylene glycol, and mineral oil), researchers have developed a series of particulate forms, including but not limited to silica dioxide (SiO2), aluminum oxide (Al2O3), titanium dioxide (TiO2), carbon nanotube, copper (Cu), silver (Ag), silicon carbide (SiC), diamond, iron oxide (Fe2O3), zinc oxide (ZnO), magnesium oxide (MgO), and cupric oxide (CuO). Particularly, silica (SiO2) nanofluids, with their good mechanical and chemical stability, abundant structures, and diverse preparation methods, make them interesting to researchers. To date, SiO2 nanofluids exhibit outstanding intensification performance in the fields of conduction, convection, and radiation heat transfer. This study provided a systematic overview of the research progress on SiO2 nanofluids for convective heat transfer applications. First, the physicochemical properties and preparation methods (i.e., one-step and two-step methods) of SiO2 nanofluids were introduced. Further, the state of the art of SiO2 nanofluids for single-phase convection and phase change convection applications was summarized, and the numerical simulation and experimental observation results of natural convection, forced convection, pool boiling, and flow boiling were tabulated and discussed in detail. Finally, the current remaining challenges and future research directions were highlighted in terms of the in-depth heat transfer enhancement principles, practical industrialization applications, systematic and accurate evaluation of heat transfer performance, preparation and characterization strategies, exploration of a high-diversity library of particulate structures, and optimization of heat exchanger apparatus. We believe that this review article can shed new insights into the rational design and preparation of advanced SiO2 nanofluids and provide important guidelines to develop robust nanofluid-based liquid cooling heat sinks.
Monthly, started in 1955 Supervising institution：Ministry of Education Sponsoring Institution：University of Science and Technology Beijing Editorial office：Editorial Department of Chinese Journal of Engineering Publisher：Science Press Chairperson：Ren-shu Yang Editor-in-Chief：Ai-xiang Wu ISSN 2095-9389CN 2095-9389
