《1 Engineering research fronts》

1 Engineering research fronts

《1.1 Trends in Top 12 engineering research fronts》

1.1 Trends in Top 12 engineering research fronts

The Top 12 engineering research fronts as assessed by the Field Group of Chemical, Metallurgical, and Materials Engineering are shown in Tables 1.1.1 and 1.1.2. “Precise construction of catalyst surface active sites”, “next-generation high-energy-density battery cathode materials”, “high- efficiency nitrogen fixation driven by green energy in photocatalytic/electrocatalytic process”, and “autonomous inference of chemical industry big data” were chosen based on the core-paper statistics provided by Clarivate together with a panel of experts. The other eight fronts were recommended by the experts directly. Three of fronts provided by Clarivate have more than 150 citations per paper. The annual number of core papers for “precise construction of catalyst surface active sites” and “high- efficiency nitrogen fixation driven by green energy in photocatalytic/electrocatalytic processes” are increasing overall year by year.

(1)  High-performance superconducting materials for energy storage

With the increasing energy demands of modern society and the worsening fossil-fuel crisis, renewable energy has seen rapid development. Specifically, driven by the Chinese government’s “double carbon” goal, the application scale and proportional usage of renewable energy are bound to increase significantly. Currently, renewable energy sources such as wind and solar power cannot generate electricity in a stable manner like traditional fossil-based energy sources. However, superconducting energy-storage technology promises to alleviate the negative impact of this intermittent nature, thereby improving power quality and grid stability to meet the needs of new power-system voltages and frequencies. At present, as the only technology that can store electrical energy directly as current, superconducting magnetic energy storage (SMES) is the major application form of superconducting energy storage. In SMES systems, superconducting coils are combined in series and parallel to form energy storage units. In the developmental stages of this technology, low- temperature superconducting magnets cooled by direct immersion in liquid helium were employed. However, the

《Table 1.1.1》

Table 1.1.1 Top 12 engineering research fronts in chemical, metallurgical, and materials engineering

《Table 1.1.2》

Table 1.1.2 Annual number of core papers published for the Top 12 engineering research fronts in chemical, metallurgical, and materials engineering

complex and expensive low-temperature refrigeration systems required greatly limit the application scale of SMES devices. SMES based on high-temperature superconductors can be operated above 20 K (−253.15 ̊C), and the operating efficiency and stability of the refrigeration systems can also be greatly improved, allowing SMES research to regain viability. However, the currently poor performance of high-temperature superconducting materials, high preparation costs, and insufficient large-scale producibility have prevented high- temperature SMES from exceeding the practical threshold of 10 MJ, and it has not found large-scale industrial application. To develop high-performance superconducting energy-storage materials, the following problems need to be solved: ① the low current-carrying capacity, poor mechanical properties, and poor electromagnetic properties of superconducting materials under high-field conditions; ② the poor large-scale production ability of high-performance, high-temperature superconducting materials; and ③ sufficient technological development of superconducting cables. The realization of large-scale preparation of high-temperature superconducting cables will provide a material foundation for the large-scale preparation of superconducting energy storage magnets.

(2)    Green and low-carbon blast-furnace ironmaking technology

The blast furnace–basic oxygen furnace (BF-BOF) process has come to dominate modern iron and steel production. However, blast-furnace ironmaking is energy and resource intensive, and its carbon emissions account for ~66% of the total in the steel industry. To achieve global carbon-emission reduction and reach carbon neutrality, developing green and low-carbon blast- furnace ironmaking technology, such as Japan’s COURSE50, Germany’s ThyssenKrupp hydrogen injection, and Baowu’s hydrogen-enriched carbon recycling, has become an important research direction. Currently, the main areas of focus for research in this field include: ① improvement of key common technologies such as low-carbon briquetting process, high blast temperatures, oxygen-enriched coal injection, top gas recycling/injection, oxygen-enriched air smelting, and prolonged blast-furnace service life to further reduce the carbon fuel consumption and pollutant emission; ② the study of frontier technologies such as hydrogen metallurgy for blast furnaces and carbon capture utilization and storage (CCUS) for the waste gas from blast furnaces to move towards near-zero carbon emission.

(3)  Precise construction of catalyst surface active sites

Driven by the energy issues and the demands of social development, science and technology are moving towards precision. The essence of precision is selectivity. In the field of catalysis, the precise and atom-economical synthesis of target products is demanded. Although using catalysts can effectively reduce the energy consumption of chemical syntheses, the development of catalysts currently entails a certain degree of trial and error and serendipity. The precise control of catalytic reaction activity will only be realized by the construction of tailored catalyst surface active sites. Current research on the precise construction of catalyst surface active sites mainly focuses on the following aspects: ① precise control of the catalyst-preparation conditions to correctly evolve the desired catalyst surface structure; ② exploiting the actions of reactants, intermediates, and by-products to induce reconstruction of the catalyst; and ③ in situ construction of catalyst surface active sites using self-assembly and other methods. For future advances, it will be necessary to first precisely observe and identify catalyst structure, necessitating concerted multidisciplinary effort to develop in situ characterization techniques. Deepening understanding the catalyst structure–activity relationships and improving the reaction efficiency by precisely construction of catalyst surface active sites. In addition, intelligent and precise construction will be needed. Here, machine learning may facilitate precise, efficient construction and aid the rational design of high-performance catalysts. Furthermore, methods for in situ construction of catalyst surface active sites need to be developed, and these will require precise catalyst synthesis processes.

(4)   High-performance gas-separation membranes for CO₂ capture

High-efficiency CO₂ separation technology is key for carbon capture and energy-industry gas purification, so it will make significant contributions to realizing carbon neutrality. Compared with traditional absorption methods for CO₂ separation, membrane technology is energy economical, no solvent evaporation is needed, it has a small footprint, and it is applicable for various processing capacities, so it has broad application prospects. At present, there are still many basic scientific problems in each stage of the technology chain that need to be further studied, mainly focusing on the following areas. ① Development of high-performance membrane materials and separation membranes. Informed by in-depth study on the structure–activity relationship between materials and separation performance, membrane materials must be designed at the molecular level, exploiting the synergy of multifunctional groups and multiple perm-selectivity mechanisms. Then, CO₂ membranes with high permeabilities and separation factors may be prepared by comprehensively adjusting their multi-layer membrane structures. ② Large- scale preparation of defect-free membranes. The industrial manufacture of high-performance and defect-free CO₂ separation membranes will require optimization of membrane production processes and improvement of the accuracy of the production equipment used. ③ Design of high-performance membrane modules. Knowledge of the fluid mechanics and mass transfer behavior within the complex flow channels of modules will contribute to the development of high- performance membrane modules with low concentration polarization, low pressure drop, and high packing density. ④ Large-scale applicability to different scenarios. The different gas-source characteristics and capture requirements of different fields will necessitate novel integrated processes and complete construction of application-specific large-scale membrane separation systems that are highly efficient and energy saving.

(5)   Next-generation high-energy-density battery cathode materials

With the rapid expansion of the electric/hybrid vehicle industry, developing batteries with high energy density, high power, long life, and low cost has become paramount. In terms of cathode materials for lithium batteries, currently used oxide cathode materials are limited by their low theoretical capacity and they cannot meet the performance requirements of next-generation batteries. In this context, to achieve higher energy density, it is necessary to develop new cathode materials with higher capacity. At present, research into cathodes for next-generation batteries is mainly focused on high-capacity materials such as high-voltage lithium cobaltate, high-nickel ternary compounds (including lithium nickel cobalt manganate and lithium nickel cobalt aluminate) and lithium-rich manganese. For improved discharge capacity and cycle stability of the batteries using high-voltage lithium cobaltate materials, it is necessary to use multi-element doping technology to break the upper voltage limit of lithium intercalation in lithium cobaltate. For high-nickel ternary materials with nickel contents equal to or greater than 80%, the specific capacity and cycle stability should be improved through synergistic means, such as element doping, surface coating, and crystal plane optimization or the use of single crystals. To ensure high specific capacity and long life for batteries built using lithium-rich manganese-based materials, it will be necessary to explore the mechanisms of charge and discharge processes, reduce the release of oxygen, and inhibit the migration of transition metal sites during charging, which may be achieved by combining element doping, crystal form optimization (O2 or O3), surface coating, and concentration gradient design. In addition to the above problems, it is vital to address the poor stability at the interface between the cathode materials and electrolytes. Moreover, because the charging cut-off voltage of new cathode materials has exceeded the upper limit of the traditional liquid electrolyte voltage window, it is urgent to modify commonly used electrolytes or explore the use of solid-state electrolytes.

(6)  High-efficiency nitrogen fixation driven by green energy in photocatalytic/electrocatalytic processes

Photocatalytic and electrocatalytic N₂ fixation technologies, with N₂ and H₂O as raw materials and renewable energy as the driving force, are environmentally friendly and economically optimal, and they must realize distributed NH₃ production at room temperature and pressure. Owing to its compressibility, high energy density, and zero carbon emission, ammonia plays an important role in modern agriculture, and thus it has the potential to become a central molecule in the future energy landscape. Photocatalysis and electrocatalysis generate high-energy electrons, which can pre-activate N₂ and greatly reduce the activation energy of its fixation processes. Chemical adsorption of N₂ on the surface of catalysts is difficult because N₂ molecules have high bond energy and weak catalyst-coordination ability, dramatically limiting the efficiency of N₂ fixation. Recent studies have mainly focused on improving the intrinsic activity of catalysts, promoting N₂ adsorption on the surface of catalysts to break the symmetry of electron distribution, weakening the N≡N bond, and enhancing proton affinity. Various strategies for engineering such catalysts have been attempted, where interface control, surface engineering, and chemical modification have been used to optimize the intrinsic reaction activity of photocatalysts as well as for designing electrocatalysts. Despite the remarkable progress and achievements in this field, however, low catalytic efficiency and poor mechanistic knowledge remain major hurdles for the development of photochemical and electrochemical N₂ fixation. To accelerate development in this field, more research in the following areas is needed to broaden the application of photocatalytic and electrocatalytic N₂ fixation. ① Rational design and controllable synthesis of more efficient, cost-effective, environmentally friendly, and robust catalytic materials for reaction systems that achieve excellent catalytic performance. ② The development of in situ characterization techniques for photocatalytic and electrocatalytic N₂ fixation to probe reaction intermediate states and enable the identification of true active sites. This will facilitate the effective combination of theoretical analysis and experimental study, which is required to reveal the relevant reaction mechanisms. ③ Rational design and structural optimization of reactors for different reaction systems to enhance their reaction efficiency and NH3 accumulation. Despite being a great challenge, the heterogeneous catalytic synthesis of ammonia under mild conditions shows great promise as a means to reduce our reliance on fossil fuels and mitigate the impact of climate change.

(7)  Autonomous inference of chemical industry big data

To meet the requirements of “carbon peak and carbon neutrality”, a move towards green and low-carbon practices in the chemical industry is imperative. Intelligent digital development may provide a means for the chemical industry to quickly achieve carbon emission reduction and improve process economics, and the core of this concept is the mining of big data generated by industrial production processes. At present, Europe, the USA, and China all have corresponding development strategies. In 2015’s Made in China 2025 initiative, the deep integration of informatization and industry was taken as a focus, and the strategic importance of industrial data was acknowledged. However, how we might mine effective information from the high-dimensional and high-noise big data generated by the chemical industry; that is, to autonomously infer the implicit dynamic mechanisms that determine the behavior of complex industrial systems, is a crucial problem that needs to be solved. Here, it is necessary to develop a new data-driven algorithm to model the spatio- temporal dynamic characteristics of different process variables, understand the causal inference between them, determine the information transmission mechanisms, and build a hidden reaction network. Furthermore, we must then integrate such mechanistic knowledge and expert experience into a data- driven model to develop an interpretable and robust system to finally realize the autonomous inference of industrial big data and lay a foundation for the autonomous optimization and decision-making of industrial systems.

(8)    Material simulations for complex extreme service conditions

Researching the behavior and properties of materials under complex extreme service conditions, such as those in nuclear reactors and aeronautical engines, weapons, and equipment, is a great challenge, mainly because it is difficult to accurately observe and test the evolution of material structure and physical properties in a considerable number of extreme environments. First, it is difficult to implement real-time and in situ observation in extreme environments. Second, it is impossible to recreate those extreme environments in the laboratory. This makes it very difficult to develop materials for complex extreme service conditions by experimental research methods alone. Material simulations is an effective method to solve this problem. Accordingly, investigating the evolution of material microstructure and physical properties under complex extreme service conditions by these means has attracted a lot of attention. Studies in this area mainly focus on the following aspects. ① Neutron irradiation and hydrogen/helium damage of materials. In terms of fission reactors, research mainly focuses on the evolution of and damage to material structure caused by neutron irradiation in the process of core structure, nuclear fuel, and nuclear waste disposal. In a fusion reactor, the material structure evolution and damage to the first wall and divertor caused by neutron irradiation and the hydrogen/helium effect are mainly studied. Such research typically involves high-throughput cross-scale calculation of material structure evolution and damage, data collection, and database establishment. ② Effects of high strain rate on materials under impact load. This mainly involves high-throughput cross-scale calculation of constitutive relationships, strong plasticity, fracture failure, and coupling relationships with microstructure evolution and material phase transformation of various materials used in weapons equipment under dynamic load and high strain rate, collection of relevant data, and establishment of databases. ③ Effects of high temperature and high gravity on materials, which are mainly evaluated by high-throughput cross-scale calculation simulation (for example, the fatigue and creep characteristics of materials in aeronautical engines under the combined effects of high temperature and high gravity during high- speed turns), collection of relevant data, and establishment of databases. ④ The physical laws of condensed materials under extremely low temperature, strong magnetic fields, and ultra-high pressure. Through high-throughput cross-scale calculation and analysis, studying the key scientific problems and phenomena that occur in materials under those different extreme conditions, the new physical laws displayed by materials under these conditions will be revealed, providing a foundation for research and the development of relevant new materials.

(9)   Construction and application of multi-dimensional gradient metamaterials

Gradient metamaterials are a new type of artificial composite or material composed of a space gradient arrangement of basic units with unique geometry. They exhibit extraordinary physical properties that natural materials do not have, which is related not only to the intrinsic properties of the constituent materials, but also to the spatial arrangement and combination of the structural units. These novel artificially structured composite materials enable flexible regulation of light, sound, electromagnetism, and heat. The combination of multi-dimensional gradients and the construction of related metamaterials can allow more complex functions. For example, introducing a frequency gradient based on the above spatial gradient metamaterials can lead to new degrees of freedom that realize a more powerful and flexible manipulation of the electromagnetic beam, which can be used in smart skins, radar antennas, and electronic countermeasure fields. At present, research of multi-dimensional gradient metamaterials focuses on the coupling effect of gradient structure and performance in medium metamaterials, high- order optical nonlinear theory, and ultra-wideband perfect wave-absorbing materials (such as electromagnetic black holes). In the future, such research will seek to realize full-band and multi-dimensional control, improve theoretical model construction, and allow structural design and performance optimization strategies, ultimately providing large-scale and high-precision metamaterial manufacturing technology and thus the widespread application and industrialization of multi-dimensional gradient metamaterials.

(10)   Bioadaptability of new implantable biomaterials for whole life cycles

Bioadaptability is a more comprehensive theoretical parameter of biomaterials based on the present concepts of biological safety and biocompatibility, and it represents a further level of requirement. The intrinsic meaning of bioadaptability can be expressed as follows: on the basis of fulfilling the general requirements of biological safety and biocompatibility, new biomaterials should actively adapt to and have an impact on various tissues, organs, and the physiological environment (histological, mechanical, chemical, and other related factors), to promote the effective repair or healing of diseased tissues and organs, and to restore normal physiological functions. Bioadaptability mainly includes, but is not limited to, three important aspects: the adaptability of the microenvironment created in situ by the biomaterial; the adaptability of the mechanical properties of the biomaterial to the native tissues; and the adaptability of the degradation behavior of the biomaterial to the formation of new tissues. The future development trend for this field is precise bioadaptability, which requires that precisely adaptable biomaterials aimed at precision medicine should have spatiotemporally tailorable characteristics considering the mechanical and degradation behaviors, so as to precisely match the physiological process of tissue repair. In addition, it requires whole-life-cycle bioadaptability for implant materials. Under the guidance of the innovative concept of bioadaptability, the main characteristics of future biomaterials should contain the features of intelligence, accuracy, vitality, and versatility.

(11)  New steel materials for offshore engineering in deep-sea environments

In the process of ocean development from offshore to open sea, from shallow to deep water, and from ocean to pole, it is very important to study the performance of ocean engineering materials. As the key structural material of ocean engineering equipment, steel is widely used in marine platforms, marine energy equipment, and submarine pipelines. The main types of steel are as follows: steel for marine oil and gas development equipment, steel for ships, steel for bridges and infrastructure, and steel for special marine equipment (including deep submersibles, seawater desalination, and deep-sea resource exploration). Owing to the complexity and particularity of the marine environment, there are generally strict requirements for ocean engineering steel, such as high thickness, high strength, high toughness, high service safety, and easy processing and welding performance. In addition, with the rapid development of deep-sea scientific research and polar sea and space exploration, study of the key technologies in terms of stable performance, specificity of shape and size, and adaption to extreme service conditions is crucial. Accordingly, ocean platform steel with ultra-high strength (above 690 MPa) and low-temperature toughness (−60 ̊C and below) will become an important research focus.

Thus, future research directions include: ① ocean platform steel with high strength and high toughness to meet the requirements of low-temperature environments with reduced construction and installation costs; ② low-cost and high-value-added products to reduce the need for the addition of Ni, Mo, and other precious alloy elements, while still meeting the safety performance requirements of deep- and polar-sea application; ③ ocean platform steel with low yield strength ratios that ensures sufficient ductility before plastic failure and prevents catastrophic brittle fracture; ④ improved crack-arrest properties to prevent the occurrence of fracture accidents.

(12)   Supernormal enrichment and ultrapure preparation of critical metals

The concept of a “critical metal” was recently developed from international politics and national strategy, and it refers to the rare and precious metals that are basic raw materials applied in high-tech industries such as new energy and electronics. The national security risks associated with critical metals are prominent, and special measures should be taken to secure an adequate supply. Most critical metals are rare and scattered elements and occur as concomitants or isomorphs, so their metallurgical extraction necessitates “supernormal enrichment”. Furthermore, the application of critical metals is specific to high purity metals or compounds with ppm impurities, making “ultra-pure preparation” a new feature of metallurgy. Unlike the traditional bulk-metal metallurgy with three high and one intense (high temperature, high pressure, high concentration, intense agitation) processes, the metallurgy of critical metals also involves “strong selectivity”, which describes the process of converting raw materials with ppm-level dispersed elements into metallurgical products with ppm-level impurity contents. According to the “reaction- selectivity principle” of chemical processes, highly selective enrichment and separation of critical metals can be achieved only in a weak-reactivity metallurgical system. The core scientific problem facing critical metal metallurgy mainly include: the occurrence of rare and rare scattered elements and supernormal enrichment mechanisms, the selective- separation dynamics of similar elements, impurity migration behavior, and process-control in the purification of critical metals.

《1.2 Interpretations for three key engineering research fronts》

1.2 Interpretations for three key engineering research fronts

1.2.1 High-performance superconducting materials for energy storage

SMES is the only technology that can store electrical energy as current directly, thus realizing almost zero current loss. Theoretically, SMES provides high power density in the range 500–2 000 W/kg, typical rated power of 1–10 MW, energy storage efficiency of more than 97%, and microsecond-level response. However, the development of energy storage technology is relatively slow, which can mainly be attributed to the high-cost of superconducting materials as well as the poor availability of low-temperature high-magnetic- field systems. At present, promising high-temperature superconductor candidates for SMES include MgB2, Bi-based materials (Bi-2223 and Bi-2212), and YBCO. After nearly 40 years’ development, high-temperature superconductors, represented by typical practical superconducting materials, such as Bi-based tapes and YBCO-coated conductors, have begun to enter the industrialization stage. Related practical applications such as in power systems, transportation, and large scientific devices have promoted these materials into the limelight of new materials research. Large-scale research and application demonstrations have been successfully carried out in the USA, the European Union, and Japan, involving a large amount of manpower and material resources, and have achieved great results. In the future, to meet the material requirements of SMES applications, it is crucial to perform the corresponding research and development for high- temperature superconducting materials and cables, and the key technologies for large-scale production have to be focused upon.

The main output countries and institutes of core papers in recent years on “high-performance superconducting materials for energy storage” are listed in Tables 1.2.1 and 1.2.2, respectively. Among the major countries, China ranks first, with 41 core papers, accounting for 44.57% of the total, which is far more than that of the USA, the UK, Japan, and other countries. Among the main institutes, Chinese

《Table 1.2.1》

Table 1.2.1 Countries with the greatest output of core papers on “high-performance superconducting materials for energy storage”

《Table 1.2.2》

Table 1.2.2 Institutions with the greatest output of core papers on “high-performance superconducting materials for energy storage”

Academy of Sciences ranks first, followed by University of Bath and Huazhong University of Science and Technology. The major collaborations between countries and institutes are plotted in Figures 1.2.1 and 1.2.2, respectively. Among the relevant research countries, China and the USA have more collaboration, with China and the UK, and the USA and Japan also collaborating closely. Closer cooperation is observed between domestic institutes, such as between Chinese Academy of Sciences and Peking University, and between Huazhong University of Science and Technology and Wuhan University. According to Table 1.2.3, the top three countries with the most core-paper citations are China, the USA, and India, where the proportion for China is 44.21%, indicating that Chinese scholars pay close attention to the research trends of this frontier. The main institutes citing core papers are Chinese, including Chinese Academy of Sciences, Jilin University, and Tsinghua University (Table 1.2.4).

SMES systems use superconducting coils to store electro- magnetic energy, and they have the advantages of fast response speed as well as flexible and adjustable active and reactive power. However, to date, high-temperature superconducting SMES has not yet exceeded the practical threshold of 10 MJ due to the low performance of high- temperature superconducting materials and their high production costs. The main problems include: ① the application of high-temperature superconducting materials requires lower AC loss and better thermodynamic and magnetic stability; ② the superconducting performance level and batch stability of mass-produced high-temperature superconducting materials still require improvement for practical application; ③ length and production scale of high- temperature superconducting wires are relatively small and cannot yet meet the requirements of customers, affecting the application development of superconducting materials; and

《Figure 1.2.1》

Figure 1.2.1 Collaboration network among major countries in the engineering research front of “high-performance superconducting materials for energy storage”

《Figure 1.2.2》

Figure 1.2.2 Collaboration network among major institutions in the engineering research front of “high-performance superconducting materials for energy storage”

《Table 1.2.3》

Table 1.2.3 Countries with the greatest output of citing papers on “high-performance superconducting materials for energy storage”

《Table 1.2.4》

Table 1.2.4 Institutions with the greatest output of citing papers on “high-performance superconducting materials for energy storage”

④ at present, the price of high-temperature superconducting materials is relatively high, resulting in relatively narrow fields of applications, and no large-scale applications have yet been demonstrated. Therefore, in the future, it is necessary to overcome the technical difficulties associated with batch preparation of high-performance MgB2, Bi-based, and YBCO materials, which will not only greatly promote the development of SMES technology, but also provide reliable materials for high- field MRI, nuclear magnetic resonance, magnetic confinement nuclear fusion, particle accelerators, and other important devices. Accordingly, future research must provide: ① a means to control the plastic deformation of MgB2 and Bi-based ceramic powder/metal multi-core composites, and a breakthrough in terms of the high-pressure heat treatment of superconducting wire; ② the optimization of coating structures for YBCO long tapes to improve its performance under high magnetic field; and ③ high-temperature superconducting cable fabrication technology suitable for batch production. For details, see the roadmap shown in Figure 1.2.3.

1.2.2 Green and low-carbon blast-furnace ironmaking technology

The essence of blast-furnace ironmaking technology is the reduction process. Here, coal is used as fuel and a reductant to obtain iron ore or iron-containing raw materials from oxides or minerals, providing liquid pig iron at high temperature. After nearly 200 years of development, modern blast furnace ironmaking technology is relatively mature and has a low production cost, and its output accounts for over 91% of the world’s total pig iron. As the largest steel producer and consumer in the world, China’s BF-BOF process

《Figure 1.2.3》

Figure 1.2.3 Roadmap of the engineering research front of “high-performance superconducting materials for energy storage”

plays a dominant role in the steel manufacturing process, and the output of blast furnace pig iron was 869 million tons in 2021, of which electric-furnace crude steel accounted for only ~10%.

The blast furnace ironmaking process is a major consumer of resources and energy in the steel manufacturing process. At present, CO2 emissions from the steel industry account for ~7% of global emissions, and ~66% of the carbon emissions in the steel process come from the blast furnace ironmaking. Thus, in terms of global carbon emission reduction and carbon neutrality, blast furnace ironmaking is a major problem. Accordingly, the main iron and steel companies in the world have put forward strategic objectives and technical routes, with green and low-carbon blast furnace ironmaking technologies being central to such strategies. The COURSE50 project, which is being explored by Japanese iron and steel companies to reduce CO2 emissions, is scheduled to realize the practical application of the first next-generation blast furnace in 2030, with widespread application scheduled for 2050. Germany’s ThyssenKrupp tested injecting hydrogen into blast furnaces in 2019, realizing the replacement of coal with hydrogen to reduce CO2 emissions. In 2020, China Baowu launched a new low-carbon metallurgical process at Xinjiang Bayi Iron & Steel Co., Ltd., carried out research on hydrogen- enriched carbon recycling blast furnace technology, and conducted industrial production tests of ultra-high oxygen- rich and even pure oxygen blast furnaces.

The main countries and institutions with the greatest output of core papers on “green and low-carbon blast-furnace ironmaking technology” since 2016 are listed in Tables 1.2.5 and 1.2.6, respectively, and the collaborations between major countries and institutions are outlined in Figures 1.2.4 and 1.2.5, respectively; the main countries and institutions with the greatest output of citing papers on this front are shown in Tables 1.2.7 and 1.2.8, respectively. China, Malaysia, Britain, and France are the top four countries in this field, with China accounting for 41.94% of core papers, far ahead of other countries. Malaysia and Bangladesh boast the greatest level of cooperation, and collaboration networks between other countries are also well developed. The most cited core papers are by researchers from China, reaching 44.66%; the UK ranked second with 8.45% of core papers cited, with Germany, the USA, and Australia accounting for 6.49%, 6.49%, and 6.40%, respectively. Thus, China ranks No.1 in terms of both cited papers and citing core papers, which indicates that Chinese scholars lead this research and pay close attention to this frontier. Among the domestic institutions with the greatest output of cited papers, University of Science and Technology Beijing is ranked No.1, with the output reaching 21.14%, followed by Northeast University and Chongqing University, with outputs exceeding 10%.

《Table 1.2.5》

Table 1.2.5 Countries with the greatest output of core papers on “green and low-carbon blast-furnace ironmaking technology”

《Table 1.2.6》

Table 1.2.6 Institutions with the greatest output of core papers on “green and low-carbon blast-furnace ironmaking technology”

《Figure 1.2.4》

Figure 1.2.4 Collaboration network among major countries in the engineering research front of “green and low-carbon blast-furnace ironmaking technology”

《Figure 1.2.5》

Figure 1.2.5 Collaboration network among major institutions in the engineering research front of “green and low-carbon blast-furnace ironmaking technology”

《Table 1.2.7》

Table 1.2.7 Countries with the greatest output of citing papers on “green and low-carbon blast-furnace ironmaking technology”

《Table 1.2.8》

Table 1.2.8 Institutions with the greatest output of citing papers on “green and low-carbon blast-furnace ironmaking technology”

In the future, blast furnace ironmaking will begin to be replaced by non-blast furnace ironmaking technologies such as direct reduction and smelting reduction, and it will also have to face the gradual reduction of steel demand, the increase of EAF steel-making, and the need for carbon peaking and neutrality. However, considering iron ore, scrap steel, and other resources in the world, blast furnace ironmaking technology will still be the most dominant practice for the foreseeable future. Therefore, its survival and development depend on green and low-carbon ironmaking technology and reduction in its use and scale. The current and future directions of green and low-carbon blast-furnace ironmaking technology mainly include carbon resource optimization, energy efficiency improvement, and frontier technology research. This includes: ① the study of high-efficiency and low-carbon briquetting processes to optimize furnace burden structure and reduce the carbon consumption and pollutant emission of iron making;  ② research on key common technologies such as high blast temperature, oxygen- enriched coal injection, top gas recycling/injection, and oxygen-enriched gas smelting to further reduce the carbon fuel consumption of blast furnaces; ③ the study of biochar/ pulverized coal mixed injection and the use of hydrogen-rich or pure-hydrogen gas to realize the replacement of carbon with hydrogen; ④ research on blast furnace long campaign technology to further extend the service life of blast furnaces; ⑤ rational study of the blast furnace ironmaking process to achieve long-term stable production practices; and ⑥ research on CCUS for the waste gas from blast furnaces. The roadmap of the engineering research front of“green and low-carbon blast-furnace ironmaking technology” is shown in Figure 1.2.6.

1.2.3 Precise construction of catalyst surface active sites

Catalysts improve reaction efficiency by reducing its activa- tion energy, thereby reducing the input energy required to generate the target product. Clearly, this concept is of enormous importance to the current increasingly serious energy crisis. However, the design and development of catalysts have occurred mainly through serendipity or trial- and-error, which requires manpower, materials, and money.

《Figure 1.2.6》

Figure 1.2.6 Roadmap of the engineering research front of “green and low-carbon blast-furnace ironmaking technology”

With deepening understanding of chemical synthesis, the rational design of efficient catalysts through precise construction of their surface-active sites is of increasing importance. The understanding of catalytically active sites has developed from being first in terms of matter, then molecules, then atoms, and finally to electrons, and it is mainly focused on the static structure of the active site. However, under real reaction conditions, the surface-active sites of a catalyst undergo dramatic and dynamic changes along with the surrounding reaction environment. Therefore, key to the precise construction of catalyst surface active sites is the combination of experimental and simulation methods to precisely identify, measure, and control the catalyst surface active sites under real reaction conditions. In view of the fact that the active sites on the catalyst surface are closely related to the surrounding reaction environment, the most direct method for constructing active sites is to control the reaction conditions (such as temperature and pressure) and use the interactions of various substances involved in the reaction process (such as reactants, activating atmosphere, intermediates, and products) with the catalyst. In addition, the in situ precise construction of active sites on a catalyst surface can also be achieved by strategies such as self-assembly.

In recent years, the main producing countries and institutions of the core papers on “precise construction of catalyst surface active sites” are shown in Tables 1.2.9 and 1.2.10, respectively. China is foremost among the major producers of core papers, with a ratio of 86.36%, which is much higher than those of the USA and Australia. The Chinese Academy of Sciences ranks first among the main producers, with 22 core papers. The cooperation between major countries and institutions is shown in Figures 1.2.7 and 1.2.8, respectively. Among the relevant research countries, China has the most

《Table 1.2.9》

Table 1.2.9 Countries with the greatest output of core papers on “precise construction of catalyst surface active sites”

《Table 1.2.10》

Table 1.2.10 Institutions with the greatest output of core papers on “precise construction of catalyst surface active sites”

cooperative relationship with the USA, followed by Australia. For cooperation between institutions, that between Chinese Academy of Sciences and University of Science and Technology of China is relatively close. According to the citation situation of papers, the number of citing core papers from China ranks first (Table 1.2.11), accounting for 67.12%, indicating that Chinese scholars pay close attention to this field. Among Chinese institutions, Chinese Academy of Sciences has the most citing core papers, accounting for 34.32%, followed by University of Science and Technology of

《Figure 1.2.7》

Figure 1.2.7 Collaboration network among major countries in the engineering research front of “precise construction of catalyst surface active sites”

《Figure 1.2.8》

Figure 1.2.8 Collaboration network among major institutions in the engineering research front of “precise construction of catalyst surface active sites”

《Table 1.2.11》

Table 1.2.11 Countries with the greatest output of citing papers on “precise construction of catalyst surface active sites”

China and Tianjin University (Table 1.2.12).

Research on the precise construction of catalyst surface active sites remains limited. This is largely because it is limited by the slow development of in situ characterization techniques and multi-scale simulation methods. Furthermore, such research involves multiple disciplines, such as catalysis, materials, and physics. The barriers between different disciplines also need to be broken down to promote their integration. Future research needs to focus on catalysts in model reaction systems to clearly identify the surface-active sites of catalysts under real reaction conditions, and then focus on realistic complex reaction systems to achieve controllable and precise synthesis of catalysts. Ultimately, the catalytic efficiency of the entire reaction system can be improved. In terms of technology, the first step is to accurately quantify and identify the active sites on the catalyst surface as well as their structure–activity relationships to achieve precise regulation of catalytic reactions. During this research process, we must make full use of in situ characterization techniques as well as multi-scale simulation methods to fundamentally reveal the structure and evolution mechanism of catalyst surface active sites, and methods such as machine learning can provide intelligent support. Finally, the precise construction of catalyst surface active sites requires attention to in situ synthesis methods during the reaction process, which can highly improve the degree and efficiency of precise construction. The roadmap of the engineering research front of “precise construction of catalyst surface active sites” is shown in Figure 1.2.9.

《Table 1.2.12》

Table 1.2.12 Institutions with the greatest output of citing papers on “precise construction of catalyst surface active sites”

《Figure 1.2.9》

Figure 1.2.9 Roadmap of the engineering research front of “precise construction of catalyst surface active sites”

《2 Engineering development fronts》

2 Engineering development fronts

《2.1 Trends in Top 10 engineering development fronts》

2.1 Trends in Top 10 engineering development fronts

The Top 10 engineering development fronts as assessed by the Field Group of Chemical, Metallurgical, and Materials Engineering are shown in Table 2.1.1. The fronts related to energy and the environment are significant here. Works on flexible materials or devices are also prominent, for example “next-generation flexible display glass materials and technology development” and “key fabrication technologies for flexible display devices and their applications”. The annual numbers of core patents for all fronts show an overall growth trend, especially for “grid-scale molten salt energy storage technology” and “new generation of flexible display glass materials and technology development” are in faster growing (Table 2.1.2).

(1)  Development and application of ultra-high temperature ceramics for extreme environments

Ultra-high temperature ceramic matrix composites (UHTCMCs) are multi-component structures composed of fibers, interfaces, and ultra-high temperature ceramic matrices. They exhibit the excellent properties of high temperature resistance, oxidation resistance, ablation resistance, and high strength. Furthermore, they are endowed with non-brittle fracture characteristics similar to those of metals and high application reliability. They are internationally recognized as a new generation of lightweight structural materials suitable for extreme high temperature and mechanical-thermal coupling service environments. Research on UHTCMCs began in the 21st century. Over 20 years of development, great progress has been made in material fabrication and densification behavior, performance evaluation, oxidation and ablation mechanisms, and application technology development. As thermal structure/ thermal protection materials, they have gradually entered the engineering application stage. The increasing application requirements and increasingly harsh service environments present new requirements for UHTCMCs technology. On the basis of further clarifying the service behavior of materials, it is vital that we design and develop new technologies for the fabrication of low-cost, short-cycle, and large- scale UHTCMCs; develop UHTCMCs with extremely high temperature resistance (>2 500 ̊C), near-zero ablation, and long-term reusability; develop ultra-high temperature ceramic fibers with ultra-high melting points (and their corresponding composites), and realize large-scale engineering application technology for UHTCMCs. With the development and advancement of new high-speed vehicle technologies, high- performance UHTCMCs and their components will be in mass demand in the coming years.

《Table 2.1.1》

Table 2.1.1 Top 10 engineering development fronts in chemical, metallurgical, and materials engineering