《1 Engineering research fronts》
1 Engineering research fronts
《1.1 Trends in Top 11 engineering research fronts》
1.1 Trends in Top 11 engineering research fronts
The Top 11 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. “Novel high-performance ceramic energy storage materials and capacitors”, “high-performance polymer acceptors and their application in flexible all-polymer solar cells”, “bionics design of intelligent biomaterials and materiobiology theory”, and “creation and application of high-catalytic-activity nanozymes” are based on core papers provided by Clarivate and experts. The other 7 fronts are recommended by experts.
The “design of rapid self-healing polymer materials” with broad application prospects has attracted the attention of scientific researchers, with 267.62 citations per paper. Papers on “novel high-performance ceramic energy storage materials and capacitors” and “high-performance polymer acceptors and their application in flexible all-polymer solar cells” related to new energy are highly cited. Papers on “research on low-temperature steel for polar ships” with a long research and development cycle have been cited only 4.38 times, but the number of core papers has increased in recent years (Table 1.1.2). The number of core papers related to “synthesis of multicarbon platform compounds from CO2”, which is most related to the “double-carbon” goal, has shown a downward trend in recent years. The number of core papers on “novel high-performance ceramic energy storage materials and capacitors” related to new energy has not changed significantly (Table 1.1.2).
(1) Novel high-performance ceramic energy storage materials and capacitors
With the continuous consumption of fossil energy and increasingly severe environmental problems, the development and use of high-performance and environmentally friendly energy storage materials and devices have become current research hotspots. Dielectric capacitors have the advantages of a high power density, rapid charge/discharge rate, excellent stability, and low manufacturing cost, which have broad
《Table 1.1.1》
Table 1.1.1 Top 11 engineering research fronts in chemical, metallurgical, and materials engineering
| No. | Engineering research front | Core papers | Citations | Citations per paper | Mean year |
| 1 | Novel high-performance ceramic energy storage materials and capacitors | 80 | 11828 | 147.85 | 2017 |
| 2 | Synthesis of multicarbon platform compounds from C02 | 250 | 21383 | 85.53 | 2016.4 |
| 3 | Coupling hydrogen metallurgy to nuclear hydrogen production | 51 | 3161 | 61.98 | 2016.7 |
| 4 | High-performance polymer acceptors and their application in flexible all-polymer solar cells | 171 | 22 224 | 129.96 | 2017.2 |
| 5 | Design of advanced materials for high-efficiency gas separation and purification and application thereof | 261 | 21148 | 81.03 | 2016.5 |
| 6 | Materials and devices for semi-conducting optical memory | 121 | 14 841 | 122.65 | 2017 |
| 7 | Design of rapid self-healing polymer materials | 151 | 40410 | 267.62 | 2016.4 |
| 8 | Multiphase micro-interface evolution behavior | 212 | 10 128 | 47.77 | 2016.6 |
| 9 | Bionics design of intelligent bio materia Is and materiobiology theory | 133 | 13 224 | 99.43 | 2017.1 |
| 10 | Research on low-temperature steel for polar ships | 91 | 399 | 4.38 | 2018.3 |
| 11 | Creation and application of high-catalytic-activity nanozymes | 114 | 14 133 | 123.97 | 2017.4 |
《Table 1.1.2》
Table 1.1.2 Annual number of core papers published for the Top 11 engineering research fronts in chemical, metallurgical, and materials engineering
| No. | Engineering research front | 2015 | 2016 | 2017 | 2018 | 2019 | 2020 |
| 1 | Novel high-performance ceramic energy storage materials and capacitors | 15 | 14 | 19 | 17 | 14 | 1 |
| 2 | Synthesis of multicarbon platform compounds from CO2 | 71 | 74 | 55 | 28 | 19 | 3 |
| 3 | Coupling hydrogen metallurgy to nuclear hydrogen production | 14 | 11 | 9 | 10 | 5 | 2 |
| 4 | High-performance polymer acceptors and their application in flexible all-polymer solar cells | 28 | 37 | 38 | 28 | 27 | 13 |
| 5 | Design of advanced materials for high-efficiency gas separation and purification and application thereof | 75 | 60 | 65 | 43 | 14 | 4 |
| 6 | Materials and devices for semi-conducting optical memory | 29 | 20 | 21 | 27 | 21 | 3 |
| 7 | Design of rapid self-healing polymer materials | 15 | 10 | 17 | 27 | 19 | 63 |
| 8 | Multiphase micro-interface evolution behavior | 58 | 50 | 50 | 36 | 17 | 1 |
| 9 | Bionics design of intelligent biomaterials and materiobiology theory | 24 | 25 | 31 | 29 | 21 | 3 |
| 10 | Research on low-temperature steel for polar ships | 6 | 7 | 9 | 24 | 23 | 22 |
| 11 | Creation and application of high-catalytic-activity | 13 | 18 | 23 | 29 | 28 | 3 |
application prospects in the storage and transportation of electric energy. Compared with traditional energy storage devices, ceramic dielectric capacitors are of increased interest in terms of dielectric properties, breakdown electric fields, stability, and fatigue resistance. However, current high- performing dielectric energy storage ceramics tend to contain elemental lead, which causes environmental pollution. Global restrictions on lead-containing materials in electronic devices have resulted in the development of environmentally friendly unleaded ceramic dielectric capacitors becoming an important research direction. Compared with traditional unleaded linear dielectrics, nonlinear dielectric materials have a higher effective energy storage density and higher energy storage efficiency because of their ferroelectric, antiferroelectric, and piezoelectric characteristics. These materials do not satisfy industrial application requirements, so the energy storage density and energy storage efficiency need to be optimized. Developments of new technologies require ceramic capacitors to exhibit a stable performance over a wide temperature range and a range of harsh operating environments. The storage, transportation, distribution, and use of high-efficiency and clean electric energy require miniaturized and lightweight energy storage devices. Core issues that need to be addressed for new high-performance ceramic energy storage capacitors include an improved effective energy density, energy storage efficiency and breakdown field strength, broadened stability over a wide temperature range, and the development of miniaturized and lightweight devices. The development of new high-performance energy storage ceramic materials and capacitors involves interdisciplinary research of materials, physics, and chemistry; urgent integration of multiple disciplines; expansion of new research paths; and the development of high-performance and environmentally friendly energy storage ceramic materials and devices.
(2) Synthesis of multicarbon platform compounds from CO2
Advances in the industrialization of human society have led to the overconsumption of fossil energy such as coal, natural gas, and fossil oil, and excessive carbon-dioxide emissions into the atmosphere by humans, resulting in an energy crisis and environmental problems. The conversion of carbon dioxide into high-value-added chemical products and the realization of an artificial carbon cycle are urgent problems that need to be solved. The preparation of multicarbon platform compounds by carbon-dioxide reduction refers to the technology of using green hydrogen that is produced by renewable energy, clean electricity, or solar energy from renewable energy to convert carbon dioxide into multicarbon products (such as ethanol, ethylene, and long-chain alkanes). Such technology achieves zero or negative carbon emissions. Research into the preparation of multicarbon products (C2+) by carbon-dioxide reduction has focused on four aspects. ① Rational design and controllable synthesis of high-efficiency catalytic materials for different reaction systems to achieve excellent catalytic performance. On the basis of an in-depth study of the catalytic mechanism, an effective structure–activity relationship should be established. ② The research and development of in situ characterization methods for carbon-dioxide reaction systems, using in situ electron microscopy, in situ spectroscopy, and in situ synchrotron radiation technology to capture and monitor the change state of intermediate species and the evolution of catalytic structures during reaction. ③ Reasonable design and structural optimization of reactors for different reaction systems to enhance mass transfer and reduce energy losses. ④ On the basis of market prices, process levels, multidimensional models and other factors, life cycle assessments and economic analyses must be carried out to provide guidance for industrial applications.
(3) Coupling hydrogen metallurgy to nuclear hydrogen production
Hydrogen is a clean fuel and an excellent reductant. Hydrogen metallurgy can reduce CO2 emissions by using hydrogen to replace carbon as the iron-ore reducing agent. Hydrogen is considered an achievable low-carbon or carbon-free metallurgical technology. The economic supply of hydrogen on a large scale is key for the development of hydrogen metallurgy. Current global industrial methods of hydrogen production include mainly fossil-fuel reforming, which struggles to meet the demands of hydrogen metallurgy with a high efficiency, at a large scale, and with no carbon emissions. Nuclear hydrogen production is an important solution for the future large-scale supply of hydrogen, and uses heat that is generated by nuclear reactors as primary energy to prepare hydrogen from water. The coupling of hydrogen metallurgy with nuclear hydrogen production is a revolutionary and significant cross innovation, which connects nuclear energy, hydrogen production, and metallurgical technology. Future research priorities include nuclear hydrogen production and hydrogen metallurgy. In nuclear hydrogen production, water is decomposed by high-temperature thermochemical circulation, and hydrogen production is by high-temperature steam electrolysis using nuclear power and nuclear heat. Hydrogen metallurgy focuses on hydrogen-enriched blast- furnace reduction, direct reduction based on hydrogen metallurgy, and smelting reduction based on hydrogen metallurgy.
(4) High-performance polymer acceptors and their application in flexible all-polymer solar cells
All-polymer solar cells (all-PSCs) have garnered significant research interest in recent years because of their inherent advantages of a good film-forming ability, stable morphology, and mechanical flexibility, which makes them attractive for use in wearable and portable electronics. The scarcity of suitable polymer acceptors remains the major obstacle for advancing this technology toward commercialization. In 2017, researchers from the Institute of Chemistry, Chinese Academy of Sciences proposed a new strategy of polymerizing small- molecule acceptors (SMAs) to construct new-generation polymer acceptors with low-band-gap SMAs as the key building block copolymerized with aromatic linking units. This strategy has merits of a strong absorption from SMAs and potential advantages of a good film-forming ability, mechanical flexibility, and high polymer stability. Polymerized SMAs (PSMAs) show tremendous potential for use in all-PSCs and remove major bottlenecks that limit all-PSCs, that is, a poor absorptivity in the near-infrared region. Inspired by the advantages of PSMAs, intensive work from different groups on the design of new PSMAs has been carried out, and extensive progress has been made on all-PSCs, with PCEs rapidly exceeding 17%. Flexible all-PSCs have been constructed, and these show excellent morphological and mechanical stabilities. With these encouraging results, the followings are suggestions: ① PSMA design with a simple structure and their synthesis via a greener routes to reduce their production cost; ② active layer morphology control and a reduction in energy loss in the all-PSCs are required to improve the device performance; and ③ the development of a flexible device that integrates well with functional devices for wearable and portable electronics is a challenging topic in this field.
(5) Design of advanced materials for high-efficiency gas separation and purification and application thereof
Gas separation is important in the energy and environment industry. Typically, the process involves a variety of separation systems, including H2/CH4 separation, CO2 capture, CO removal, and fuel desulfurization. However, traditional separation technologies, such as low-temperature separation, pressure-swing adsorption, and chemical absorption do not meet the vision of carbon neutrality because of their high energy consumption. Therefore, new separation methods with a high efficiency, low energy consumption, and environmental friendliness have gradually been given attention, such as ionic-liquid absorption, new-adsorbent adsorption, and microporous-membrane separation. Among them, the development of new materials for adsorption and membrane separation has become an important research frontier. Current new microporous or mesoporous materials, including carbon-based adsorbents, zeolites, and covalent/ metal organic frameworks, have attracted the most attention because of their large surface area, controllable pore diameter, chemical properties, and acceptable stability. Key scientific challenges in the design of new materials include the development of a level of molecular control, modern characterization, and computational methods, which help to support large-scale screening of new materials and guide high-throughput material synthesis and characterization, based on which further refinement to the most promising structures can be provided.
(6) Materials and devices for semi-conducting optical memory
Semi-conducting optical memory can convert external optical signals into electrical signals to provide memory of light on a photoelectronic device based on semi-conducting materials. A high integration density, multifunctionalization of electronic memory, compatibility with conventional CMOS technology, rapid computing speed, low power consumption, low crosstalk, and high-speed internet broadband of optical devices are expected in neuromorphological calculations. Photoelectronic memory based on semi-conducting materials is in a stage of rapid development, and the main challenge remains the transformation of the optical signal to an electrical signal with the achievement of data storage and calculation by light modulation. Current attention with regards semi-conducting optical storage materials and devices has been given to the selection and preparation of optical storage materials, new mechanisms for optical memory, the fabrication of artificial vision systems, and a focus on the inherent correlation between the defect chemistry of low-dimensional surface/interfaces and the properties of photoelectronic memory.
(7) Design of rapid self-healing polymer materials
Rapid self-healing polymer materials can repair spontaneously or through stimulating the properties or functions of damaged parts. Self-healing can extend polymer material service life, reduce maintenance costs, reduce raw material waste, and improve the reliability of materials in use. Self-healing polymer materials have attracted attention in the field of flexible electronic skins, tissue engineering, and smart materials. Intrinsic self-healing polymer materials are the main research direction of self-healing polymer materials. Two main design routes include: ① dynamic covalent crosslinking introduction into the polymer networks (such as disulfide bonds, dynamic borate bonds, Diels-Alder reactions, and Schiff base reactions) and ② non-covalent cross-linking introduction into the polymer networks (such as hydrogen bonding, metal coordination interaction, electrostatic interaction, and host– guest interaction). Harsh self-healing conditions and the loss of physical and mechanical properties from the introduction of many self-healing groups are the main problems. Therefore, self-healing materials with mild self-healing conditions, synergistic self-healing, and a high strength are proposed future directions. Research into the intrinsic structure– property relationship of self-healing hydrogels, and the underlying healing mechanisms and molecular dynamics processes are still in their infancy. The challenge of self- healing polymers is to prepare self-healing networks with the same metabolic characteristics as the living body. Therefore, the goal of future research on self-healing polymers is to make organism-like materials that are autonomous and adaptable and can determine their own growth and structural assembly in response to the environment, like the coding molecules of biological organisms.
(8) Multiphase micro-interface evolution behavior
The properties and behaviors of interfaces in multiphase systems often affect mass transfer, heat transfer, momentum transfer, separation, and reaction in chemical processes. Multiphase micro-interface evolution behavior (MMEB) refers to the interface behavior that is caused by multifarious physicochemical processes on the phase interface. MMEB is critical in many processes, and involves the chemical composition, physical structure, and electronic state of the substances in the interface region, and the properties of the main phase substances on both sides of the interface. MMEB includes the breakup and coalescence of the phase interface, thinning and fracturing behavior of the liquid film, interfacial mass transfer and enrichment, and interfacial fluctuation and capillary wave propagation. Thus, a study of the interfacial phenomena and behavior in different systems helps us to understand the objective laws of chemical processes and is of significance in the design and optimization of chemical reactions and industrial separation processes. Physical and chemical changes between multiphase interfaces are also involved in material manufacturing technology. The application of interface chemistry laws and interfacial properties improves the process conditions and opens new technical fields. Relevant frontier research includes: regulation and control techniques of pollutant interfacial behaviors and its applications, micro-interface reaction strengthening and structure–activity regulation of heterogeneous reaction systems, theoretical research and model development of nanofluid interface behaviors, material design and structural optimization based on interfacial behaviors, and in situ drive techniques for particle interface self-assembly.
(9) Bionics design of intelligent biomaterials and materiobiology theory
Biomaterials and biology have a close relationship. The theory of “materiobiology” is derived from their interdependence, which is a scientific discipline that studies the biological effects of the characteristics of biological materials at the level of biological functions of cells, tissues, organs, and the entire organism. The principles of materiobiology contribute to the development of new intelligent biomaterials. An understanding of the basic mechanism of the interaction between materials and organisms provides inspiration for the design of other advanced bionic materials. Most traditional biomaterials have been used statically in clinical applications. To deal with more complex disease treatments, intelligent biomaterials with self-adaptive properties have been developed to extend their broader biomedical application. These materials are highly sensitive to stimulation changes in the biological environment because of their self-adaptive dynamics, which allow them to be used in applications such as cell recovery, isolation, and nanomedicine for damage/ disease therapy. New intelligent biomaterials that can adjust specific biological functions include pH-responsive hydrogels, chemical-sensitive biomaterials, stimulus-responsive drug-release systems, artificial cell membranes and bionic treatment system for diagnosis, and surface-recognition– response characteristics of biomaterials. The integration of life and material sciences, which is aimed at organisms and bionics at different levels, can make materials and systems intelligent and environmentally friendly. The bionics design strategy provides new opportunities for the development of intelligent biological materials, enriches materiobiological theories, and drives advancements of new self-adaptive intelligent biomaterials and advanced novel technologies based on such intelligent biomaterials.
(10) Research on low-temperature steel for polar ships
Global warming and polar accessibility have led to polar region exploitation by many countries and a drive in the demand and development of polar ship equipment. Polar ships require steel with an extremely high performance that can function in a harsh environment at ultralow temperature for extended periods. The steel needs an excellent low- temperature toughness, high strength, weldability, and fatigue performance because the hull below the ice contact line is hit repeatedly by ice. Russia, Japan, South Korea, Finland, and other countries are leaders in the research and development of low-temperature steel for polar ships. In recent years, on the basis of the building of the “Snow Dragon” icebreaker, China has made breakthroughs in the development and application of key materials for polar ships, and has provided a foundation for low-temperature steel for polar ships. Problems remain, such as the production of low-temperature steel with a thickness above 80 mm whose grade is E, F, and higher; evaluation studies of low-temperature steel for polar regions; and research on the low-temperature toughness and strength mechanism of ultrathick steel. Attention to the polar- region strategy provides broad prospects for the research and development of low-temperature steel for ships and proposes higher requirements for material performance. The following need to be considered in the future: ① low-temperature steel needs strength-matching toughness and crack arresting to adapt to harsh navigation conditions and to ensure the safety of ships at low temperatures; ② low-temperature steel requires an improved strength to reduce the mass, increase the load capacity, and improve the speed of polar ships; ③ to improve the efficiency, reduce the cost, and simplify maintenance in a harsh environment, low-temperature steel must meet the requirements of low-temperature toughness and have a high heat energy welding performance; and ④ the welding materials, technology, and evaluation of fracture behavior at ultralow temperature should be addressed.
(11) Creation and application of high-catalytic-activity nanozymes
Nanozymes are a group of functional nanomaterials that mimic the activities of natural enzymes to convert enzyme substrates to products under physiologically relevant conditions and obey the enzymatic kinetics. Nanozymes combine nanoscale and enzyme-like catalytic properties, and have advantages such as a facile preparation and purification, high stability, and excellent recycling performance compared with native enzymes. Therefore, they have emerged as promising materials in bridging heterogeneous and enzymatic catalysis. Nanozymes function under harsh conditions that would normally inactivate native enzymes, which holds promise for future applications of analysis, sensation, biomedicine, and environmental remediation fields. Future nanozyme research should focus on: ① expanding categories of new nanozyme-catalyzed- reactions, especially those that native enzymes cannot catalyze in nature; ② precise characterization of catalytic behaviors to investigate the catalytic mechanisms of nanozymes; and ③ delicate design of active sites to mimic the sophisticated structures of enzymes to improve the activity and specificity.
《1.2 Interpretations for three key engineering research fronts》
1.2 Interpretations for three key engineering research fronts
1.2.1 Novel high-performance ceramic energy storage materials and capacitors
Rapid developments of the global economy and increased energy consumption have resulted in a global fossil energy crisis, climate change, environmental pollution, and other issues. Therefore, it is necessary to develop clean and renewable energy sources for a clean, low-carbon, safe, and efficient energy system that should gradually dominate the energy system. The efficient and convenient use of renewable energy poses stringent requirements on energy storage devices, and makes energy storage a key issue for global development. Ideal electric energy storage technology should have advantages of a high simultaneous energy and power density, be environmentally friendly, economically feasible, and reliable in use. Commonly used electrical energy storage devices include mainly batteries, electrochemical capacitors, and dielectric capacitors. Compared with the first two electrical energy storage devices, dielectric capacitors have advantages of a higher power density, shorter charge and discharge, and higher voltage, which shows great application prospects in the fields of power electronics, new energy vehicles, aerospace, and cutting-edge technology. Materials that are used in dielectric capacitors include mainly ceramic- and polymer-based materials. Dielectric ceramics have advantages of a larger dielectric constant, lower dielectric loss, moderate breakdown electric field, better temperature resistance, stability, and good fatigue resistance, and hence they are excellent candidates for energy storage materials. For example, dielectric ceramics with a high energy storage density and high reliability have almost irreplaceable application in high-energy pulsed power technology and other fields. Almost all dielectric ceramics with an excellent energy storage performance contain lead that is harmful to the human body and the environment. Therefore, new lead- free energy storage ceramics with a high energy storage density have become the research focus.
In the research field of new energy storage ceramics, the focus is on nonlinear dielectric ceramics with ferroelectric, antiferroelectric, piezoelectric and other characteristics, and mainly involves sodium bismuth titanate (Na0.5Bi0.5TiO3), barium titanate (BaTiO3) and silver niobate (AgNbO3)-based ceramics. Compared with traditional lead-free ceramics with linear dielectrics, their effective energy storage density and energy storage efficiency are higher. Furthermore, because the density of lead-free dielectric ceramics is significantly lower than that of lead-based ceramics, miniaturization and integration of energy storage capacitors are easier for the same energy storage density. However, the energy storage density of most lead-free dielectric ceramics remains far from industrial application requirements.
Current research on high-performance lead-free dielectric ceramics has focused mainly on resolving key issues, such as improving the effective energy density, energy storage efficiency and breakdown field strength; widening the stability temperature range; and developing miniaturization and lightweight ceramic energy storage capacitors. The research involves the following aspects: ① the development of new lead-free dielectric ceramics with a greater effective energy storage density and energy storage efficiency; ② the preparation of relaxation-type antiferroelectric ceramic materials by doping to obtain a higher effective energy storage density and energy storage efficiency; and ③ the development of a new process to prepare ultrafine ceramic powders, increase the relative material density, reduce the grain size, and increase the breakdown field strength of dielectric ceramics. The development of new high-performance energy storage ceramics and capacitors involves interdisciplinary research into materials, physics, and chemistry. However, core researchers have focused mainly on the fields of ferroelectric, piezoelectric, and dielectric materials. The integration of multiple disciplines, expansion of new research paths, and development of high-performance and environmentally friendly energy storage materials and devices are required.
In recent years, the main countries and institutions that have produced core papers on “novel high-performance ceramic energy storage materials and capacitors” are shown in Tables 1.2.1 and 1.2.2, respectively. China ranks first with 72 core papers, far ahead of the United States, the United Kingdom, Australia, and other countries (Table 1.2.1). As shown in Table 1.2.2, Xi ‘an Jiaotong University ranks first among institutions with 21 published papers, followed by Tsinghua University, the Chinese Academy of Sciences, and Tongji University. According to Table 1.2.3, the top three citing countries for core papers are China, the United States, and India. Table 1.2.4 shows that the Xi’an Jiaotong University, Chinese Academy of Sciences, and Tsinghua University are the main institutions that published core papers. Collaborations among major countries and institutions are shown in Figures 1.2.1 and 1.2.2, respectively. China–USA, China–UK, and China–Australia show the most collaboration followed by USA–UK and USA– Australia. Extensive collaboration exists among the top ten institutions (Figure 1.2.2).
1.2.2 Synthesis of multicarbon platform compounds from CO2
Excessive consumption of fossil energy has led to an energy crisis and excessive CO2, which has had a serious impact on global ecosystems. The Chinese government has proposed a strategic goal of “double carbon”, which limits excessive carbon-dioxide generation through emission reductions, capture, storage, and utilization, and improved related technologies to achieve carbon neutralization. The catalytic conversion of CO2 to multicarbon platform compounds is an important direction in carbon capture and resource utilization, with important research significance, economic value, and industrialization prospects. However, because of the high thermodynamic stability of CO2 molecules, carbon-dioxide activation and C=O bond breakage have become problematic in carbon conversion. Because multicarbon products undergo C—C bond coupling, the effective formation of C—C bonds and a control of the coupling extent have become research difficulties in carbon conversion.
Researchers have proposed the use of renewable energy to drive reactions, catalyze the directional conversion of carbon dioxide into high value-added carbon products, establish an artificial carbon cycle, and achieve zero or negative carbon emissions. Research into the conversion of carbon dioxide to multicarbon products by various catalytic technologies remains limited, and most studies have focused on C1 products. Among them, the thermal catalytic conversion of carbon dioxide to multicarbon products is the most studied carbon-dioxide conversion technology, but problems remain,
《Table 1.2.1》
Table 1.2.1 Countries with greatest output of core papers on “novel high-performance ceramic energy storage materials and capacitors”
| No. | Country | Core papers | Percentage of core papers | Citations | Citations per paper | Mean year |
| 1 | China | 72 | 90.00% | 10168 | 141.22 | 2017.1 |
| 2 | USA | 12 | 15.00% | 2 541 | 211.75 | 2017 |
| 3 | UK | 10 | 12.50% | 1370 | 137 | 2017.2 |
| 4 | Australia | 9 | 11.25% | 1962 | 218 | 2018 |
| 5 | Czech Republic | 2 | 2.50% | 266 | 133 | 2018.5 |
| 6 | Germany | 2 | 2.50% | 169 | 84.5 | 2016 |
| 7 | South Korea | 1 | 1.25% | 189 | 189 | 2018 |
| 8 | Russia | 1 | 1.25% | 173 | 173 | 2016 |
| 9 | Pakistan | 1 | 1.25% | 169 | 169 | 2018 |
| 10 | Sweden | 1 | 1.25% | 162 | 162 | 2018 |
《Table 1.2.2》
Table 1.2.2 Institutions with the greatest output of core papers on “novel high-performance ceramic energy storage materials and capacitors”
| No. | Institution | Core papers | Percentage of core papers | Citations | Citations per paper | Mean year |
| 1 | Xi'an Jiaotong University | 21 | 26.25% | 3 835 | 182.62 | 2017.2 |
| 2 | Tsinghua University | 15 | 18.75% | 2 451 | 163.4 | 2017.4 |
| 3 | Chinese Academy of Sciences | 12 | 15.00% | 1536 | 128 | 2017.8 |
| 4 | Tongji University | 10 | 12.50% | 1116 | 111.6 | 2017.2 |
| 5 | University of Wollongong | 8 | 10.00% | 1833 | 229.12 | 2018 |
| 6 | Shaanxi University of Science & Technology | 8 | 10.00% | 914 | 114.25 | 2017.9 |
| 7 | The Pennsylvania State University | 7 | 8.75% | 1948 | 278.29 | 2016.7 |
| 8 | Air Force Engineering University | 5 | 6.25% | 822 | 164.4 | 2017 |
| 9 | The University of Sheffield | 5 | 6.25% | 693 | 138.6 | 2017.8 |
| 10 | Huazhong University of Science & Technology | 5 | 6.25% | 644 | 128.8 | 2017 |
《Figure 1.2.1》
Figure 1.2.1 Collaboration network among major countries in the engineering research front of “novel high-performance ceramic energy storage materials and capacitors”
《Figure 1.2.2》
Figure 1.2.2 Collaboration network among major institutions in the engineering research front of “novel high-performance ceramic energy storage materials and capacitors”
《Table 1.2.3》
Table 1.2.3 Countries with the greatest output of citing papers on “novel high-performance ceramic energy storage materials and capacitors”
| No. | Country | Citing papers | Percentage of citing papers | Mean year |
| 1 | China | 2 660 | 64.64% | 2019 |
| 2 | USA | 418 | 10.16% | 2018.9 |
| 3 | India | 253 | 6.15% | 2019.4 |
| 4 | UK | 167 | 4.06% | 2019 |
| 5 | Germany | 127 | 3.09% | 2019 |
| 6 | South Korea | 123 | 2.99% | 2019 |
| 7 | Australia | 121 | 2.94% | 2019.1 |
| 8 | Japan | 89 | 2.16% | 2019.2 |
| 9 | France | 62 | 1.51% | 2018.8 |
| 10 | Thailand | 48 | 1.17% | 2018.9 |
《Table 1.2.4》
Table 1.2.4 Institutions with the greatest output of citing papers on “novel high-performance ceramic energy storage materials and capacitors”
| No. | Institution | Citing papers | Percentage of citing papers | Mean year |
| 1 | Xi'an Jiao Tong University | 330 | 19.08% | 2019 |
| 2 | Chinese Academy of Sciences | 269 | 15.55% | 2018.9 |
| 3 | Tsinghua University | 228 | 13.18% | 2018.8 |
| 4 | Tongji University | 152 | 8.79% | 2018.9 |
| 5 | Shaanxi University of Science & Technology | 144 | 8.32% | 2019 |
| 6 | The Pennsylvania State University | 131 | 7.57% | 2018.6 |
| 7 | Wuhan University of Technology | 124 | 7.17% | 2019 |
| 8 | Northwestern Polytechnical University | 93 | 5.38% | 2018.9 |
| 9 | Sichuan University | 93 | 5.38% | 2019.2 |
| 10 | Huazhong University of Science and Technology | 86 | 4.97% | 2019 |
such as a low selectivity and low product yield. Research hotspots have focused mainly on: ① the preparation of new catalytic materials to improve the selectivity and activity for multicarbon products. The thermal catalytic system focuses mainly on the rational design of bifunctional catalysts, including metal nanoparticles and zeolite molecular sieve composites, metal oxides (such as ZnO and Ga2O3), zeolite molecular sieves (such as SAPO-34 and ZSM-5), composites and specific structure catalysts (such as a core– shell structure). Cu-based materials are studied mostly in electrocatalytic systems, including their morphology and structure, doping elements, and surface/interface design, to improve the kinetics of electrochemical reactions, increase the specific surface area and electrical conductivity of electrode materials, and improve the multicarbon yield and stability of the system. ② Develop in situ characterization methods for carbon-dioxide conversion systems, including in situ electron microscopy (such as STEM, TEM), in situ spectroscopy (such as infrared and Raman spectroscopy,) and in situ synchrotron radiation technology (such as XAFS). Research work on direct in situ observation of electrocatalytic processes was published in Nature in 2021. Through a combination of in situ scanning probe and X-ray microscopy, the relationship between the oxygen evolution activity and locally adjustable structure of single-crystal β-Co (OH)2 flake particles was established, and the dynamic relationship between bulk-ion insertion and surface catalytic activity was revealed. ③ Optimization of reaction conditions, reasonable reactor design, and structural innovation in different systems. Fixed-bed, fluidized-bed, and membrane reactors are used in industry but improvements and innovation are needed in different systems. ④ For carbon-dioxide conversion, life cycle assessment and economic analysis are carried out by considering factors such as raw materials, production process, and engineering equipment to provide a basis for industrial application.
Since 2015, the main countries and institutions that have published core papers on the “synthesis of multicarbon platform compounds from CO2” are shown in Tables 1.2.5 and 1.2.6, respectively, and collaboration among major countries and institutions is shown in Figures 1.2.3 and 1.2.4. China published most, with Chinese Academy of Sciences ranking first among the main output institutions with 34 published papers. As shown in Figure 1.2.3, China and the USA have the most collaborative relationships, and close cooperation exists between China and the UK, China and Japan, and the USA and Canada. Close collaboration exists between the Oak Ridge National Laboratory and The University of Tennessee in the USA, and Korea Research Institute of Chemical Technology and Pusan National University (Figure 1.2.4). According to Table 1.2.7, the top three cited countries include China, the USA, and Germany, and Table 1.2.8 shows that the Chinese Academy of Sciences and Tianjin University are the main institutes of cited papers.
1.2.3 Coupling hydrogen metallurgy to nuclear hydrogen production
Coupling hydrogen metallurgy to nuclear hydrogen production is a major revolutionary and innovation technology, which uses high-temperature gas-cooled reactors to provide hydrogen, power, and heat for metallurgy; develops hydrogen metallurgical technology with hydrogen instead of carbon; and achieves the coupling of nuclear hydrogen production to metallurgical technology. The coupling will lead to new future global trends in the development of nuclear energy and the metallurgical industry when this technology works.
Major iron and steel companies globally are developing hydrogen metallurgy, but the large-scale economic production of hydrogen has become a bottleneck. In Europe, hydrogen production by water electrolysis with renewable energy (such as wind and solar power generation) is being carried out and applied in the direct reduction of iron ore to achieve steel production without fossil energy. Hydrogen production by water electrolysis has a low efficiency and high cost, and is not economical for application in the metallurgical industry on a large scale. Nuclear hydrogen is an important solution for large-scale future hydrogen supply, with advantages of no greenhouse gas emissions and the use of water as a raw material, with a high efficiency and large scale. The USA, Japan, South Korea, and France are carrying out research into nuclear hydrogen production. POSCO, a Korean steel company, participated in research into nuclear hydrogen production with the Korean Atomic Energy Research Institute in 2009 and tested hydrogen-reduction technology in a blast furnace. China’s research began in 2005. In 2019, China
《Table 1.2.5》
Table 1.2.5 Countries with the greatest output of core papers on “synthesis of multicarbon platform compounds from CO2”
| No. | Country | Core papers | Percentage of core papers | Citations | Citations per paper | Mean year |
| 1 | China | 115 | 46.00% | 8116 | 70.57 | 2016.6 |
| 2 | USA | 50 | 20.00% | 4487 | 89.74 | 2016.3 |
| 3 | Germany | 23 | 9.20% | 3 733 | 162.3 | 2016.2 |
| 4 | South Korea | 16 | 6.40% | 1264 | 79 | 2016.4 |
| 5 | J叩an | 14 | 5.60% | 1375 | 98.21 | 2016.1 |
| 6 | UK | 11 | 4.40% | 748 | 68 | 2017.5 |
| 7 | Australia | 9 | 3.60% | 683 | 75.89 | 2016.8 |
| 8 | Spain | 9 | 3.60% | 631 | 70.11 | 2017 |
| 9 | Canada | 8 | 3.20% | 625 | 78.12 | 2016.6 |
| 10 | France | 7 | 2.80% | 686 | 98 | 2015.7 |
《Table 1.2.6》
Table 1.2.6 Institutions with the greatest output of core papers on “synthesis of multicarbon platform compounds from CO2”
| No. | Institution | Core papers | Percentage of core papers | Citations | Citations per paper | Mean year |
| 1 | Chinese Academy of Sciences | 34 | 13.60% | 2 604 | 76.59 | 2016.5 |
| 2 | Oak Ridge National Laboratory | 7 | 2.80% | 544 | 77.71 | 2016.3 |
| 3 | Brookhaven National Laboratory | 6 | 2.40% | 1041 | 173.5 | 2016.7 |
| 4 | The University of Tennessee | 6 | 2.40% | 392 | 65.33 | 2016.5 |
| 5 | Sun Yat-sen University | 6 | 2.40% | 370 | 61.67 | 2016.5 |
| 6 | Technische Universitat Munchen | 5 | 2.00% | 589 | 117.8 | 2016.4 |
| 7 | National University of Singapore | 5 | 2.00% | 514 | 102.8 | 2016.4 |
| 8 | Korea Research Institute of Chemical Technology | 5 | 2.00% | 505 | 101 | 2016.4 |
| 9 | Pusan National University | 5 | 2.00% | 471 | 94.2 | 2016.2 |
| 10 | Zhejiang University | 5 | 2.00% | 296 | 59.2 | 2016.2 |
《Figure 1.2.3》
Figure 1.2.3 Collaboration network among major countries in the engineering research front of “synthesis of multicarbon platform com- pounds from CO2”
《Figure 1.2.4》
Figure 1.2.4 Collaboration network among major institutions in the engineering research front of “synthesis of multicarbon platform com- pounds from CO2”
《Table 1.2.7》
Table 1.2.7 Countries with the greatest output of citing papers on “synthesis of multicarbon platform compounds from CO2”
| No. | Country | Citing papers | Percentage of citing papers | Mean year |
| 1 | China | 7 069 | 49.98% | 2018.9 |
| 2 | USA | 1761 | 12.45% | 2018.7 |
| 3 | Germany | 846 | 5.98% | 2018.7 |
| 4 | India | 733 | 5.18% | 2019 |
| 5 | South Korea | 687 | 4.86% | 2018.9 |
| 6 | UK | 653 | 4.62% | 2018.9 |
| 7 | J叩an | 582 | 4.12% | 2018.8 |
| 8 | Australia | 516 | 3.65% | 2019 |
| 9 | Spain | 468 | 3.31% | 2018.6 |
| 10 | Iran | 426 | 3.01% | 2018.9 |
《Table 1.2.8》
Table 1.2.8 Institutions with the greatest output of citing papers on “synthesis of multicarbon platform compounds from CO2”
| No. | Institution | Citing papers | Percentage of citing papers | Mean year |
| 1 | Chinese Academy of Sciences | 1282 | 40.45% | 2018.8 |
| 2 | Tianjin University | 265 | 8.36% | 2019.2 |
| 3 | Dalian University of Technology | 243 | 7.67% | 2018.9 |
| 4 | Nankai University | 192 | 6.06% | 2018.6 |
| 5 | Tsinghua University | 183 | 5.77% | 2018.8 |
| 6 | University of Science and Technology of China | 177 | 5.59% | 2019.1 |
| 7 | South China University of Technology | 177 | 5.59% | 2018.7 |
| 8 | Zhejiang University | 175 | 5.52% | 2018.8 |
| 9 | Huazhong University of Science and Technology | 167 | 5.27% | 2018.7 |
| 10 | Beijing University of Chemical Technology | 164 | 5.18% | 2019.3 |
Baowu Steel Group, CNNC, and Tsinghua University signed an agreement to carry out collaborative research on nuclear hydrogen metallurgy projects. The coupling of hydrogen metallurgy to nuclear hydrogen production remains in the early stage, but it has received extensive attention from metallurgical and nuclear energy industries globally with wide application prospects.
Future research includes nuclear hydrogen production and hydrogen metallurgy. For nuclear hydrogen production, fourth-generation nuclear-technology ultra/high-temperature gas-cooled reactors are recognized as the most suitable reactors for nuclear hydrogen production because of their inherent safety, high outlet temperature, and suitable power. Key research directions of hydrogen-production technology include iodine–sulfur thermochemical-cycle decomposition water–hydrogen production using nuclear heat at the outlet of a high-temperature gas-cooled reactor, mixed-sulfur- cycle decomposition water–hydrogen production, and high- temperature steam electrolysis using nuclear power and nuclear heat. In terms of hydrogen metallurgy, key research include hydrogen-enriched blast furnace reduction, direct reduction based on hydrogen metallurgy, and smelting reduction based on hydrogen metallurgy. In Europe, research has focused mainly on hydrogen-based shaft furnace direct reduction. In China, the BF-BOF is the main route for iron and steel production. Therefore, we should focus on hydrogen- enriched blast-furnace reduction, and direct reduction based on hydrogen metallurgy in the future.
Most core papers were published by Canada, the USA, Turkey, and China, where Canada’s output accounted for 33.33%. Publications from Australia, the USA, and Turkey were cited most (Table 1.2.9) and institutions with the greatest output of
《Table 1.2.9》
Table 1.2.9 Countries with the greatest output of core papers on “coupling hydrogen metallurgy to nuclear hydrogen production”
| No. | Country | Core papers | Percentage of core papers | Citations | Citations per paper | Mean year |
| 1 | Canada | 17 | 33.33% | 940 | 55.29 | 2016.9 |
| 2 | USA | 7 | 13.73% | 550 | 78.57 | 2016.7 |
| 3 | Turkey | 7 | 13.73% | 442 | 63.14 | 2017.7 |
| 4 | China | 7 | 13.73% | 175 | 25 | 2016 |
| 5 | Malaysia | 4 | 7.84% | 194 | 48.5 | 2016.2 |
| 6 | Australia | 3 | 5.88% | 391 | 130.33 | 2015.7 |
| 7 | Germany | 3 | 5.88% | 70 | 23.33 | 2016.3 |
| 8 | Bangladesh | 2 | 3.92% | 121 | 60.5 | 2017 |
| 9 | Egypt | 2 | 3.92% | 106 | 53 | 2017 |
| 10 | UK | 2 | 3.92% | 87 | 43.5 | 2017.5 |
《Table 1.2.10》
Table 1.2.10 Institutions with the greatest output of core papers on “coupling hydrogen metallurgy to nuclear hydrogen production”
| No. | Institution | Core papers | Percentage of core papers | Citations | Citations per paper | Mean year |
| 1 | University of Ontario Institute of Technology | 14 | 27.45% | 814 | 58.14 | 2017.2 |
| 2 | Yildiz Technical University | 3 | 5.88% | 200 | 66.67 | 2018 |
| 3 | The University of Queensland | 2 | 3.92% | 354 | 177 | 2015.5 |
| 4 | Bahcesehir University | 2 | 3.92% | 212 | 106 | 2018.5 |
| 5 | Mansoura University | 2 | 3.92% | 106 | 53 | 2017 |
| 6 | Karabuk University | 2 | 3.92% | 103 | 51.5 | 2017.5 |
| 7 | UniversitiTeknologi Malaysia | 2 | 3.92% | 73 | 36.5 | 2015.5 |
| 8 | Chinese Academy of Sciences | 2 | 3.92% | 57 | 28.5 | 2015.5 |
| 9 | King Fahd University of Petroleum and Minerals | 2 | 3.92% | 51 | 25.5 | 2015.5 |
| 10 | Northeastern University | 2 | 3.92% | 48 | 24 | 2015 |
《Figure 1.2.5》
Figure 1.2.5 Collaboration network among major countries in the engineering research front of “coupling hydrogen metallurgy to nuclear hydrogen production”
core papers were mainly from Turkey (Table 1.2.10). Turkey and Canada had the most collaborations, followed by Australia and the USA (Figure 1.2.5). Some collaboration existed between Turkish institutions and universities (Figure 1.2.6). China and the USA had 30.83% and 13.63% of the citations, respectively (Table 1.2.11). China had the most citations, which indicates that Chinese scholars are at the forefront in this research area. The Chinese Academy of Sciences had the highest number of citations with Northeastern University and Tsinghua University exceeding 10% of the cited papers (Table 1.2.12).
《2 Engineering development fronts》
2 Engineering development fronts
《2.1 Trends in Top 11 engineering development fronts》
2.1 Trends in Top 11 engineering development fronts
The top eleven engineering development fronts assessed by the Field Group of Chemical, Metallurgical, and Materials Engineering are shown in Table 2.1.1. “Deep purification and resource utilization of waste gas from the process industry”, “design and application of wearable flexible intelligent systems”, “key materials in green intelligent secondary batteries and system application”, “biobased and biodegradable polyester rubber materials” and “new light alloys with high strength and excellent corrosion resistance” were based on patents provided by Derwent Innovations
《Figure 1.2.6》
Figure 1.2.6 Collaboration network among major institutions in the engineering research front of “coupling hydrogen metallurgy to nuclear hydrogen production”
《Table 1.2.11》
Table 1.2.11 Countries with the greatest output of citing papers on “coupling hydrogen metallurgy to nuclear hydrogen production”
| No. | Country | Citing papers | Percentage of citing papers | Mean year |
| 1 | China | 715 | 30.83% | 2019.3 |
| 2 | USA | 316 | 13.63% | 2019.1 |
| 3 | Canada | 192 | 8.28% | 2019 |
| 4 | UK | 169 | 7.29% | 2019.3 |
| 5 | Germany | 169 | 7.29% | 2019 |
| 6 | Turkey | 156 | 6.73% | 2019.1 |
| 7 | South Korea | 132 | 5.69% | 2019.5 |
| 8 | Iran | 132 | 5.69% | 2019.3 |
| 9 | India | 117 | 5.05% | 2019.2 |
| 10 | Italy | 114 | 4.92% | 2019 |
《Table 1.2.12》
Table 1.2.12 Institutions with the greatest output of citing papers on “coupling hydrogen metallurgy to nuclear hydrogen production”
| No. | Institution | Citing papers | Percentage of citing papers | Mean year |
| 1 | University of Ontario Institute of Technology | 83 | 17.51% | 2018.6 |
| 2 | Chinese Academy of Sciences | 60 | 13.39% | 2019.3 |
| 3 | Northeastern University | 52 | 11.61% | 2018.9 |
| 4 | Tsinghua University | 51 | 11.38% | 2018.8 |
| 5 | Yildiz Technical University | 48 | 10.71% | 2018.8 |
| 6 | University of Science and Technology Beijing | 34 | 7.59% | 2019.1 |
| 7 | University ofTehran | 33 | 7.37% | 2019.2 |
| 8 | University of Tokyo | 32 | 7.14% | 2019.1 |
| 9 | Forschungszentrum Julich | 29 | 6.47% | 2018.5 |
| 10 | Imperial College London | 28 | 6.25% | 2019.8 |
《Table 2.1.1》
Table 2.1.1 Top 11 engineering development fronts in chemical, metallurgical, and materials engineering
| No. | Engineering development front | Published patents | Citations | Citations per patent | Mean year |
| 1 | Industrialization of low-cost and high-efficiency perovskite solar cells | 1303 | 1682 | 1.29 | 2018.73 |
| 2 | Deep purification and resource utilization of waste gas from process industry | 1472 | 1566 | 1.06 | 2017.14 |
| 3 | Preparation technology for large-scale homogeneous high-entropy alloy | 899 | 2 861 | 3.18 | 2018.52 |
| 4 | Key technologies for green and low-carbon smelting | 984 | 1539 | 1.56 | 2016.96 |
| 5 | Design and application of wearable flexible intelligent system | 449 | 1318 | 2.94 | 2017.82 |
| 6 | Key materials in green intelligent secondary battery and system application | 675 | 6 955 | 10.3 | 2016.22 |
| 7 | Bio-based and biodegradable polyester rubber materials | 1115 | 1598 | 1.43 | 2017.86 |
| 8 | Ultra-fast laser precision manufacturing technology for multi-scale functional materials | 622 | 6141 | 9.87 | 2016.68 |
| 9 | Advanced ammonia fuel cell system and its applications | 501 | 3 533 | 7.05 | 2016.15 |
| 10 | New light alloys with high strength and excellent corrosion resistance | 442 | 6 272 | 14.19 | 2016.95 |
| 11 | Development and application of key alloy materials for extreme environment | 640 | 834 | 1.3 | 2017.73 |
Index. The other six were recommended by experts. As an emerging energy technology, “Industrialization of low-cost and high-efficiency perovskite solar cells” has a low number of published patents (Table 2.1.1), but the number of core patents shows an obvious upward trend (Table 2.1.2). “Key materials in green intelligent secondary batteries and system application” remains a direction of widespread interest with highly cited patent articles (10.3 per patent) and an increase in number of core patents in recent years. The citations per patent of “new light alloys with high strength and excellent corrosion resistance” reached 14.19, but the number of core patents showed a downward trend.
(1) Industrialization of low-cost and high-efficiency perovskite solar cells
Organic–inorganic hybrid perovskite solar cells have advantages of high photoelectron power-conversion efficiency and a low production cost, which makes them one of the most promising technologies for industrialization among third-generation photovoltaics. Because perovskite can be prepared by a low-temperature solution-based method, carbon emissions during production are reduced. Therefore, the industrialization of perovskite solar cells is of great significance to reduce energy consumption and emissions in
《Table 2.1.2》
Table 2.1.2 Annual number of core patents published for the Top 11 engineering development fronts in chemical, metallurgical, and mate- rials engineering
| No. | Engineering development front | 2015 | 2016 | 2017 | 2018 | 2019 | 2020 |
| 1 | Industrialization of low-cost and high-efficiency perovskite solar cells | 21 | 101 | 166 | 208 | 342 | 342 |
| 2 | Deep purification and resource utilization of waste gas from process industry | 213 | 402 | 168 | 188 | 194 | 240 |
| 3 | Preparation technology for large-scale homogeneous high- entropy alloy | 28 | 54 | 75 | 170 | 256 | 292 |
| 4 | Key technologies for green and low-carbon smelting | 96 | 112 | 120 | 129 | 112 | 193 |
| 5 | Design and application of wearable flexible intelligent system | 35 | 71 | 77 | 77 | 88 | 94 |
| 6 | Key materials in green intelligent secondary battery and system application | 82 | 98 | 78 | 73 | 76 | 128 |
| 7 | Bio-based and biodegradable polyester rubber materials | 101 | 133 | 185 | 166 | 168 | 206 |
| 8 | Ultra-fast laser precision manufacturing technology for multiscale functional materials | 65 | 56 | 67 | 106 | 104 | 101 |
| 9 | Advanced ammonia fuel cell system and its applications | 45 | 50 | 57 | 71 | 69 | 80 |
| 10 | New light alloys with high strength and excellent corrosion resistance | 83 | 82 | 108 | 111 | 57 | 1 |
| 11 | Development and application of key alloy materials for extreme environment | 90 | 86 | 95 | 129 | 115 | 125 |
the photovoltaic industry. Research on the industrialization of perovskite solar cells has received increased attention and input from academia and industry globally. Major photovoltaic production and consumption economies such as China, the USA, and the European Union have listed perovskites as key photovoltaic technologies. Frontier topics for the industrialization of perovskite photovoltaics focus mainly on the development of high-efficiency photovoltaic panel fabrication technologies that are suitable for large areas, streamlined production, encapsulation and stability improvement of perovskite photovoltaic modules, and the development of tandem solar cells with silicon as bottom cells.
(2) Deep purification and resource utilization of waste gas from the process industry
“Industrial waste flue gases” is the general term for gases that contain a variety of pollutants that are discharged from power generation, steel sintering, building materials, and coking industries during fuel combustion and production. Problems such as acid rain, haze, the hole in the ozone layer, greenhouse effects, and photochemical smog from waste gas emissions threaten the ecological environment and human development. Hence, it is particularly important to develop economical and effective purification technologies for industrial waste flue gas. After decades of development, technologies such as electrostatic precipitators, wet flue gas desulfurization, and selective catalytic reduction denitration are relatively mature and used extensively in power plants. Control equipment is aimed at a single pollutant and a series arrangement is used, which results in a large occupation area, system complexity, and high operation costs. Current in-depth control strategies of industrial flue gas are shifting from single pollutant control to the collaborative control of multiple pollutants. Advanced technologies of collaborative purification include activated carbon collaborative control technology, dust removal collaborative control technology, and SCR collaborative control technology. The above technologies involve the application of adsorption and catalytic materials and the design and synthesis of adsorption and catalytic materials with an excellent effect, low price, high stability, and strong applicability as key future issues.
(3) Technology for large-scale homogeneous high-entropy alloy preparation
High-entropy alloys (HEAs), which are a family of solid solutions that are composed of multiprincipal elements in equimolar or near-equimolar ratios, have unique properties such as a high strength and robust resistance to wear, radiation, low-temperature embrittlement, and high-temperature softening. Therefore, HEAs show great application prospects in key fields such as nuclear energy, anti-corrosion engineering, and power systems. However, the complex compositions and unsatisfactory castability limit the manufacture of large-scale bulk HEAs. To date, bulk HEAs have been prepared mainly by powder metallurgy and casting. Both methods are limited in the large-scale fabrication of bulk HEAs. Frontier technologies of large bulk HEAs are carried out according to: ① new smelting equipment and techniques for HEA casting (e.g., vacuum suspension smelting) and an optimization of smelting preparation; ② the development of additive manufacturing technology, especially technology that enables defect reduction, quality control, and near- net-shape forming for the manufacture of HEA components with complex shapes; and ③ large HEA additive forging technology for engineering applications and processes for the manufacture of different HEA systems by additive forging.
(4) Key technologies for green and low-carbon smelting
As a major consumer of resources and energy, the metallurgy industry is a large carbon emitter, and low-carbon development technologies are essential. Innovative and breakthrough low-carbon metallurgical technology in the steel industry is essential towards achieving carbon reduction. Europe, Japan, South Korea, and the USA have provided their own development routes and strategy plans for low-carbon metallurgy. In 2021, SSAB, a Swedish iron and steel company, produced “fossil-free steel” with zero carbon emissions for the first time, which was an important step towards carbon neutrality in the metallurgical industry. In recent years, China has promoted the green transformation of the metallurgical industry, carried out developments of green and low-carbon metallurgical technology, and progressed key technologies, such as hydrogen-enriched blast furnace reduction, high scrap ratios in converter steelmaking, and near-net shape manufacturing. However, no major breakthrough has been made in terms of key technologies. Three future directions will be faced in green and low-carbon metallurgical technology: ① process treatment: a development of top gas recycling blast furnaces, high scrap ratios in converter smelting, green and high-efficiency electric arc furnace steel-making, high- efficiency continuous casting technology, hot delivery and hot charging of continuous casting billets, near-net shape endless rolling, and biomass energy utilization, which are based on the optimization of existing processes, an adjustment of energy structure, and the use of waste heat and energy; ② source treatment: the use of hydrogen to replace traditional carbon reduction, including hydrogen-enriched blast-furnace reduction, direct reduction, and smelting reduction based on hydrogen metallurgy; and ③ terminal treatment: a development of the technology of carbon capture, utilization, and storage.
(5) Design and application of wearable flexible intelligent system
Wearable flexible intelligent systems make use of wireless communication, artificial intelligence, big data, flexible electronics, sensors, chip integration, and other technologies to achieve the intelligent design of various wearable objects. In the intelligent era, wearable flexible intelligent systems show important research value and potential application in the fields of health and fitness, medical and health care, industry and military, information, and entertainment because of their wearability, sustainability, interactivity, and intelligence. To achieve technical dominance in the field of wearable flexible intelligence, countries have formulated research and development plans and made efforts to overcome technical difficulties. Research in related fields has focused mainly on the following technologies: sensor preparation, flexible electronics, batteries, wireless communication, human–computer interactions, big data, and cloud computing technologies. Insufficient endurance ability, poor comfort, low data accuracy, single function, security, and privacy risks remain problematic. Comfort, miniaturization, intelligence, self-power, and multifunction are future research directions. Overall design and system construction based on functional requirements of wearable smart products, combined with the Internet of Things, mobile internet, and other technologies will generate huge economic and social value.
(6) Key materials in green intelligent secondary batteries and system application
The development of new rechargeable secondary batteries is key to achieving efficient energy conversion and storage, and has been applied in new energy vehicles, aerospace, large-scale energy storage, smart grids, and other major national demand fields. Secondary energy storage batteries have passed through the development of lead-acid, lithium- ion, sodium-ion, and zinc-ion batteries. The increasingly prominent influence of resources, cost, safety, and other factors, with an improvement in energy storage performance of secondary batteries is necessary in green, cheap, and safe battery systems. The advancement of these properties has been limited by improvements and innovative research into key materials in batteries. The exploration of new materials, technologies, and processes, together with the development of new, environmentally friendly, and low-cost electrode and electrolyte materials, can lead to new general- purpose technologies, such as interface microstructure design and regulation technology. Combined with advanced semiconductor technology, secondary battery manufacturing achieves digitization and green intelligence, and ultimately, the construction and system application of a high energy density, a high safety, a long life, and green intelligent secondary batteries.
(7) Biobased and biodegradable polyester rubber materials
Rubber is irreplaceable in daily life and national defense because of its unique properties. Global rubber consumption is ~30 million tons, of which China’s rubber consumption is ~10 million tons. However, rubber is not environmentally friendly and is non-degradable. Biodegradable polyester rubber material is obtained by melt-condensation polymerization of large biobased diacids and diols, which can resolve pollution problems. Biodegradable polyester rubber materials are expected to be used in degradable tires, degradable shoes, environmentally friendly toughening, and plasticizing agents for polyester plastics, oil-resistant rubber materials, and in other fields. A wider field of application can be achieved by molecular structure design and formula process optimization. Since China proposed the concept of biobased polyester rubber at the International Rubber Conference in 2008, 1 000 tons of pilot production has been completed. Biobased degradable rubber materials, which are an original rubber variety, are currently in the stage of performance optimization and market verification. The synthesis process, catalyst system, and production equipment differ from general polyester materials. Key technologies involve obtaining high- molecular-weight polyester rubber, optimizing formulation and processability, and adjusting the rubber degradation rate to meet product requirements. Continuous production and processing must be accelerated to achieve market application as soon as possible.
(8) Ultrafast laser-precision manufacturing technology for multiscale functional materials
Functional materials and devices are oriented by functional requirements and generally have single or combined functions, such as light, electricity, sound, magnetism, and heat. The development of multimaterial, multiscale, and multifunctional integration has led to traditional design theory and manufacturing methods no longer being applicable in the manufacture of functional materials and devices. The introduction of new manufacturing technology to achieve the cross-scale fine machining of multifunctional materials from the macro- to the mesoscopic scale would be valuable. Ultrafast laser-precision manufacturing technology is based on a short pulse laser with a shorter duration than lattice thermal diffusion and energy injection into the region with a high spatial selection, to achieve ultrafine three- dimensional material processing. The technology uses a non- hot melt, is accurate and selective, and has unique processing advantages in its structural complexity, material diversity, scale leap, and functional integration, which has great potential in the manufacture of functional material devices. The development of ultrafast laser-precision manufacturing technology for multiscale processing of functional materials requires multiscale “shape control” and multimaterial “property control”. The evolution of a physical field during the interaction between the laser and material needs to be explored from multiple perspectives, and the mechanism of action between the ultrafast laser and multiscale construction of functional materials should be revealed. The mapping relationship of laser time domain and spatial distribution should be constructed by using multiple parameters that reflect the properties and morphology of materials as indicators, to form a complete processing evaluation system. The demand for functional material devices has driven the development of multiscale precision manufacturing of functional materials and an expansion of its research value and application prospects in industry, aerospace, military, medical, and daily life.
(9) Advanced ammonia fuel cell system and its applications
Hydrogen is a green-energy source with high conversion efficiency, but difficulties in hydrogen storage and transportation, and its low intrinsic safety limit its application for reasons of safety, efficiency, and cost. Ammonia, which has high hydrogen content, is liquefied easily under mild conditions for storage and transportation and has a high intrinsic safety, which makes it a promising candidate for hydrogen storage. Hydrogen storage in ammonia and the development of ammonia-fed fuel-cell technology is supposed to be a new way to provide carbon-free energy with a high efficiency and safety and a low cost. Research on the clean transformation and utilization of ammonia energy, such as the “REFUEL” program, the “Green Ammonia” project, and ammonia-based energy storage demonstration systems, has been developed in the United States, Japan, and Europe, respectively. The ammonia production in China is the largest globally, and it should therefore be possible to build a mature system of ammonia storage and transportation for carbon- free ammonia-fed fuel cell technology. Research on ammonia- fed fuel cell technology is at the cutting edge globally, and includes indirect ammonia fuel cells (ammonia decomposition for hydrogen production coupled with a hydrogen fuel cell) and direct ammonia fuel cells, for which the main challenges are as follows: ① the synthesis and large-scale production of ammonia decomposition catalysts with a high catalytic performance at low temperature for hydrogen production, and their corresponding catalytic reactors, ② the system integration and whole-chain process technology for low- temperature indirect ammonia-fed fuel cells, and ③ the design and fabrication of anodes for direct ammonia-fed fuel cells with a high catalytic performance and the development of a membrane electrode.
(10) New light alloys with a high strength and excellent corrosion resistance
New light alloys include mainly aluminum, magnesium, and titanium alloys. Their good performance in terms of a low density, high specific strength, easy processing and recycling, and long service life has led to their widespread use in transportation, shipping and marine engineering, biomedicine, electronics information, aerospace, national defense, and military industry. However, problems such as poor corrosion, a poor oxidation resistance, and a low strength have limited their wider application. An ultrahigh- strength aluminum alloy (> 600 MPa) and magnesium alloy (> 400 MPa) are considered advanced structural materials. To expand its application scope in marine, aviation, and other fields, it is important to improve the corrosion resistance of light alloys significantly. Technologies to prepare new light alloys with a high strength and excellent corrosion resistance in the future include: ① a study of alloying theory and an optimization of the composition design of light alloys; ② new light alloy preparation methods, and the process of strengthening–toughening deformation and heat treatment; ③ technology for light-alloy surface anti-corrosion and modification; ④ a study of the light-alloy corrosion behavior and mechanism; and ⑤ preparation and application of high- strength corrosion resistant aluminum-, magnesium-, and titanium-based matrix composites.
(11) Development and application of key alloy materials for extreme environments
Developments in science and technology have led to increased metal material use in extreme service environments, such as high altitudes, deep-sea, polar, and space fields, which exist at high and low temperatures, high and low pressures, high humidities, high overloads, and long service times. Research into the development of advanced special steels, high-temperature specialty metals, high-strength light alloys, and their composites has become important because of the focus on national major projects and high- end equipment manufacture. The contrast between strong plastic properties, high–low temperature properties, and long-transient material properties is required to meet extreme service-condition requirements. Future research directions include: ① a mechanism of microstructure strengthening- toughening and fatigue resistance of high-strengthening– toughening, and corrosion-resistant metal materials in extreme service environments and damage and failure mechanisms of metal materials in extreme service environments; and ② technologies for the preparation and processing of high- performance metal materials and their key components, service safety evaluation and life prediction of metal materials and their components in extreme environments, and surface protection and surface-composite-reinforced engineering of metal materials and key components in extreme environments.
《2.2 Interpretations for three key engineering development fronts》
2.2 Interpretations for three key engineering development fronts
2.2.1 Industrialization of low-cost and high-efficiency perovskite solar cells
Photovoltaic technology is one of the most widely used technologies for solar energy use. China has the world’s largest photovoltaic industry and the world’s highest photovoltaic system installed capacity. Because the current photovoltaic industry is still dominated by crystalline silicon, higher energy consumption during production has become an obstacle towards reducing carbon emissions further. Therefore, the development of low-energy consumption photovoltaic technologies is of great significance.
Perovskite solar cells use organic metal-halide semiconductors with perovskite-type crystal structures as light-absorbing materials. Perovskite solar cells have advantages of a higher theoretical efficiency (~30%) and lower production costs. The current laboratory efficiency exceeds 25%, is the most efficient technology in third-generation photovoltaics, and is comparable to current silicon solar cells. Unlike silicon solar cells that require high-temperature processing, perovskite solar cells can be prepared by low-temperature solution processing, which could reduce the energy consumption and carbon emissions.
In early attempts of perovskite PV industrialization, efficiency was the focus point of most research interest. Current small- area module efficiencies have gradually exceeded 20% and stability issues have received increasing attention from academia and industry. A perovskite solar module with a lifetime longer than 10 000 hours has been reported recently. The combination of perovskite and silicon solar cells to construct tandem cells can improve the silicon cell efficiency significantly. For example, the Helmholtz Institute in Germany reported ~30% perovskite–silicon two-junction tandem solar cells. The tandem cell system with good compatibility with existing silicon photovoltaic equipment has appeal in the upgrade of the traditional silicon photovoltaics industry. Current key trends in perovskite industrialization remain divided in two directions: the development of single-junction solar cell systems and tandem solar cell systems. In single- junction solar cell systems, the current research focus is to improve the efficiency and stability of the device by composition and structure optimization with encapsulation technology. For tandem systems, it is also important to pay attention to the spectral matching of the perovskite layer/ silicon underlayer and charge extraction efficiency at the interface. Regardless of whether the system is single-junction or tandem, improvements in solar module stability while ensuring a high efficiency remain the main goal and challenge of current research.
In the industrial development of perovskite solar cells, Chinese scholars and research institutions have a leading position in fundamental research into perovskite solar cells. Corresponding scientific and technological advantages are reflected in industrialization research trends. China leads in patent application numbers and has the leading number of institutions (Table 2.2.1). China also has the largest number of leading commercial corporations that are engaged in perovskite industrialization research (Table 2.2.2). In addition to China, Japan and the United States have fewer patents but have attracted more attention. China–Germany and the USA– South Korea show the highest international collaborative developments (Figure 2.2.1). No obvious collaborative relationship exists between different institutions. It is believed that strong collaboration between leading institutions would occur after the technological path of perovskite industrialization becomes clearer.
《Table 2.2.1》
Table 2.2.1 Countries with the greatest output of core patents on “industrialization of low-cost and high-efficiency perovskite solar cells”
| No. | Country | Published patents | Percentage of published patents | Citations | Percentage of citations | Citations per patent |
| 1 | China | 1047 | 80.35% | 1327 | 78.89% | 1.27 |
| 2 | South Korea | 158 | 12.13% | 120 | 7.13% | 0.76 |
| 3 | Japan | 33 | 2.53% | 85 | 5.05% | 2.58 |
| 4 | USA | 25 | 1.92% | 75 | 4.46% | 3 |
| 5 | Germany | 4 | 0.31% | 21 | 1.25% | 5.25 |
| 6 | India | 4 | 0.31% | 0 | 0.00% | 0 |
| 7 | Switzerland | 3 | 0.23% | 9 | 0.54% | 3 |
| 8 | UK | 2 | 0.15% | 1 | 0.06% | 0.5 |
| 9 | Sweden | 1 | 0.08% | 4 | 0.24% | 4 |
| 10 | Russia | 1 | 0.08% | 3 | 0.18% | 3 |
《Table 2.2.2》
Table 2.2.2 Institutions with the greatest output of core patents on “industrialization of low-cost and high-efficiency perovskite solar cells”
| No. | Institution | Published patents | Percentage of published patents | Citations | Percentage of citations | Citations per patent |
| 1 | Huazhong University of Science and Technology | 31 | 2.38% | 100 | 5.95% | 3.23 |
| 2 | University of Electronic Science and Technology of China | 29 | 2.23% | 55 | 3.27% | 1.9 |
| 3 | Soochow University | 29 | 2.23% | 19 | 1.13% | 0.66 |
| 4 | Beijing Hongtai Innovation Technology Co. Ltd. | 29 | 2.23% | 4 | 0.24% | 0.14 |
| 5 | Wuhan University of Tech nology | 27 | 2.07% | 32 | 1.90% | 1.19 |
| 6 | Hangzhou Xianna Optoelectronic Technology | 26 | 2.00% | 12 | 0.71% | 0.46 |
| 7 | Shanghai Institute of Ceramics of Chinese Academy of Sciences | 26 | 2.00% | 6 | 0.36% | 0.23 |
| 8 | Nanjing University of Posts and Telecommunications | 23 | 1.77% | 23 | 1.37% | 1 |
| 9 | Seoul National University | 22 | 1.69% | 35 | 2.08% | 1.59 |
| 10 | Nanjing Tech University | 21 | 1.61% | 34 | 2.02% | 1.62 |
《Figure 2.2.1》
Figure 2.2.1 Collaboration network among major countries in the engineering development front of “industrialization of low-cost and high-efficiency perovskite solar cells”
2.2.2 Deep purification and resource utilization of waste gas from the process industry
Industrial waste flue gas is one of the main air-pollutant sources. Large amounts of pollutants, such as particulate matter (PM), nitrogen oxides (NOx), sulfur oxides (SO2), volatile organic compounds (VOCs), and heavy metals, are emitted from power plants, steel sintering plants, building materials, and coking industries during fuel combustion and production. The removal technologies of multiple pollutants in power generation are relatively mature, but applications of pollutant control technologies and equipment in steel, coking, and cement industries are in the development stage. Problems, such as acid rain, haze, the hole in the ozone layer, greenhouse effects, and photochemical smog from pollutant emissions threaten the ecological environment and human development. Therefore, developments of multipollutant emission control for industrial waste flue gas have become key to improving current environmental quality.
The diversity of production processes in different industries has resulted in significant differences in flue gas pollutant emission characteristics, large fluctuations in flue gas flow and temperature, complex and variable flue gas composition, and a strong corrosivity. These differences have resulted in higher requirements for in-depth treatment technologies and air-pollution processes. Some developed countries have studied pollutant treatment in industrial flue gas, and pollutant control is focused mostly on single pollutant control technologies. Electrostatic precipitators, wet desulfurization, and selective catalytic reduction denitration have been widely applied in practice. With the tightening of environmental protection and technological progress, in addition to PM, SO2, and NOx, the removal of unconventional pollutants needs to be solved urgently, which increases challenges in post- treatment technology. Different pollutant removal equipment is arranged in tandem series, which leads to large floor areas, complex systems, and high investment and operating costs. From the perspective of technological development, the field of flue gas treatment has changed from a control strategy for single pollutants to the development of efficient and economic collaborative removal technology for multiple pollutants. Academia and industry are committed to collaborative in- depth control of PM, SO2, NOx, and unconventional pollutants; the development of new technologies or equipment; and constructing multipollutant collaborative treatment demonstration projects in many fields, such as sintering furnaces, cement kilns, waste incinerators, and coal-fired boilers, to provide key technical support for the in-depth elimination of multipollutant in flue gas.
Frontiers and hot technologies of collaborative deep purification and recycling of industrial waste gas mainly include: ① Multipollutant collaborative control technology of activated carbon. On the basis of activated carbon, waste gas pollutants can be purified through adsorption and catalysis, which achieves the systematic control of SO2, NOx, and unconventional pollutants, and sulfur resource utilization. ② Dust removal collaborative control technology. With a bag filter as the core, the catalyst is loaded into the pores of ceramic fiber filter tubes to form a material with a catalytic effect, to achieve the integrated removal of PM, NOx, and mercury. ③ SCR denitration collaborative control technology. In addition to the selective reduction of NOx, SCR catalysts have a certain oxidation performance. Within a certain temperature range, SCR catalysts can decompose volatile organic compounds, dioxins, and other organic pollutants in waste gas into harmless substances, such as carbon dioxide and water, and oxidize elemental mercury into divalent mercury, for the simultaneous removal of NOx, dioxins, and mercury. These technologies involve the application of adsorption/catalytic materials. The design and synthesis of adsorption/catalytic materials with an excellent performance, low price, good stability, and strong universality are key issues in the development of various future technologies.
China, Japan, South Korea, Germany, and the USA are the top five countries in terms of patents related to deep purification and resource utilization of industrial waste flue gas (Table 2.2.3). Chinese institutions or individuals lead in terms of patent quantity at 94.23%. However, the number of citations per Chinese patent is 0.94, which is far lower than that of Germany, Japan, and the USA, indicating that the innovation and influence of Chinese patents should be improved. There is little collaboration between countries on the engineering development front. China needs to strengthen international cooperation and develop core technologies with independent intellectual property rights.
Most of the main institutions with the greatest output of core patents (Table 2.2.4) are enterprises, which indicates that the technology of deep purification and resource utilization of industrial flue gas has gradually become market-oriented. The first and second institutions are WISDRI Engineering & Research Inc. Ltd. and Suzhou Yunlan Environmental Protection Technology Co. Ltd., respectively. According to the collaboration networks of the top ten patent output institutions, cooperative development and joint study is still lacked between enterprises and universities, and there is potential for industry–university–research cooperation in cutting-edge technology.
2.2.3 Technology for large-scale homogeneous high- entropy alloy preparation
HEAs break traditional alloy design concepts and represent a class of materials that are composed of multiprinciple elements in equimolar or near-equimolar ratios. Compared with traditional alloys, HEAs have multiple excellent properties, such as a high strength, high hardness, high ductility, and robust resistance to low-temperature embrittlement, high-temperature softening, wearability, and irradiation. With great application potential in extreme conditions, such as ultralow/high temperature, irradiation, and a corrosive environment, HEAs have rapidly become a
《Table 2.2.3》
Table 2.2.3 Countries with the greatest output of core patents on “deep purification and resource utilization of waste gas from process industry”
| No. | Country | Published patents | Percentage of published patents | Citations | Percentage of citations | Citations per patent |
| 1 | China | 1387 | 94.23% | 1302 | 83.14% | 0.94 |
| 2 | J叩an | 47 | 3.19% | 142 | 9.07% | 3.02 |
| 3 | South Korea | 12 | 0.82% | 10 | 0.64% | 0.83 |
| 4 | Germany | 6 | 0.41% | 85 | 5.43% | 14.17 |
| 5 | Russia | 3 | 0.20% | 8 | 0.51% | 2.67 |
| 6 | USA | 3 | 0.20% | 0 | 0.00% | 0 |
| 7 | Austria | 1 | 0.07% | 9 | 0.57% | 9 |
| 8 | Switzerland | 1 | 0.07% | 5 | 0.32% | 5 |
| 9 | Saudi Arabia | 1 | 0.07% | 0 | 0.00% | 0 |
《Table 2.2.4》
Table 2.2.4 Institutions with the greatest output of core patents on “deep purification and resource utilization of waste gas from process industry”
| No. | Institution | Published patents | Percentage of published patents | Citations | Percentage of citations | Citations per patent |
| 1 | WISDRI Engineering & Research Inc. Ltd. | 26 | 1.77% | 29 | 1.85% | 1.12 |
| 2 | Suzhou Yunlan Environmental Protection Technology Co., Ltd., | 19 | 1.29% | 24 | 1.53% | 1.26 |
| 3 | Guangdong Junfenghua Technology Co., Ltd. | 5 | 0.34% | 19 | 1.21% | 3.8 |
| 4 | The Wonderland Environmental Protection Technology (Suzhou) Co., Ltd. | 5 | 0.34% | 8 | 0.51% | 1.6 |
| 5 | Ningbo Dongfang Shengda Environmental Protection Technology Co., Ltd. | 5 | 0.34% | 6 | 0.38% | 1.2 |
| 6 | Shenzhen Hongdong Environmental Engineering Co., Ltd. | 5 | 0.34% | 6 | 0.38% | 1.2 |
| 7 | China Petroleum & Chemical Corporation | 5 | 0.34% | 6 | 0.38% | 1.2 |
| 8 | Suzhou Rainbow Environmental Equipment Co., Ltd. | 5 | 0.34% | 2 | 0.13% | 0.4 |
| 9 | Mitsubishi Heavy Industries Ltd. | 4 | 0.27% | 31 | 1.98% | 7.75 |
| 10 | Sun Yat-sen University | 4 | 0.27% | 21 | 1.34% | 5.25 |
research focus among global materials. The emergence of HEAs makes it possible to transfer the paradigm of material research from “apply existing-materials” to “design in- demand materials”. By regulating the composition of multiple components to achieve a combination of excellent material properties, high-performance materials may be formed that overcome the limits of traditional materials. Potential applications of HEAs include solid-state cooling, liquified natural gas processing, irradiation-resistant materials, high- performance aerospace materials, superhard ballistic systems, ruggedized and corrosion-resistant medical devices, magnetic resonance imaging technology, and other key areas of the defense industry. Large-scale bulk HEA preparation is key for HEA application.
HEA preparation methods include mechanical alloying, coating deposition, powder metallurgy, casting, and additive manufacturing. Mechanical alloying is mainly used to prepare HEA powder. Coating deposition, including laser cladding deposition and magnetron sputtering deposition, is mainly used to prepare HEA coatings. Bulk HEA fabrication mainly involves powder metallurgy based on solid-phase forming and casting based on liquid-phase forming. HEA and composite fabrication through powder metallurgy is achieved by sintering the alloy powder. However, the alloy is easily exposed to a contaminant environment, which makes it difficult to eliminate pores in the alloy, and only a limited HEA shape and size can be obtained. Casting is the most effective preparation method for HEAs with different dimensions. However, because of the complex composition and different melting points of multiprinciple elements, HEAs have a poor liquidity and castability, which leads to the formation of casting defects, such as segregation, shrinkage cavity, and cracks in the cast ingots, and difficulties in homogenized large-scale bulk HEA manufacture. The reported maximum HEA mass is limited to a few kilograms.
HEA preparation remains limited to the laboratory scale with many unsolved issues with existing preparation methods. To better serve important national industries and gain competitiveness in international markets as a mass product, it is necessary to speed up the layout and carry out in-depth research on HEA preparation as soon as possible. The following aspects should be addressed: ① casting is the most effective bulk HEA preparation method and the casting capacity requires improvement. Vacuum arc melting is used mostly in HEA casting, but the HEA size, shape, and uniformity are limited. Vacuum levitation melting provides less contamination, a high-temperature capability, better uniformity, and the capability to fabricate relatively big size samples and has demonstrated good potential application for the preparation of small inhomogeneous bulk HEAs. Vacuum levitation technology should be studied further to prepare different types of HEAs with a high quality. ② HEA additive manufacturing with advantages in grain refinement and component shape complexity has also been studied extensively recently. However, defect control and treatment in additive manufacturing need to be studied further and elucidated. ③ New developed additive forging technology provides significant prospects in the large-scale manufacture of bulk HEAs. Homogenized large-scale HEA production can be achieved by additive forging of small high-quality alloy billets. Although additive forging technology has been applied successfully in the fields of wind power, hydropower, and nuclear power, the fundamental research and application of this technology to HEAs remain in its infancy. The following aspects need to be resolved: the fabrication of homogenized small HEA billets, exploration of efficient surface cleaning methods and the development of special surface treatment equipment for additive forging, and the construction of an HEA additive forging demonstration line.
After more than one decade, HEA development in China is rapid, and the number of patents has increased rapidly. Tables 2.2.5 and 2.2.6 show the main countries and institutions that have produced core patents on “technology for large-scale homogeneous high-entropy alloy preparation”. China has
《Table 2.2.5》
Table 2.2.5 Countries with the greatest output of core patents on “preparation technology for large-scale homogeneous high-entropy alloy”
| No. | Country | Published patents | Percentage of published patents | Citations | Percentage of citations | Citations per patent |
| 1 | China | 809 | 89.99% | 2 431 | 84.97% | 3 |
| 2 | South Korea | 52 | 5.78% | 257 | 8.98% | 4.94 |
| 3 | USA | 11 | 1.22% | 89 | 3.11% | 8.09 |
| 4 | India | 5 | 0.56% | 0 | 0.00% | 0 |
| 5 | Switzerland | 4 | 0.44% | 13 | 0.45% | 3.25 |
| 6 | Romania | 4 | 0.44% | 7 | 0.24% | 1.75 |
| 7 | Japan | 2 | 0.22% | 33 | 1.15% | 16.5 |
| 8 | Russia | 2 | 0.22% | 2 | 0.07% | 1 |
| 9 | Sweden | 1 | 0.11% | 10 | 0.35% | 10 |
| 10 | UK | 1 | 0.11% | 2 | 0.07% | 2 |
《Table 2.2.6》
Table 2.2.6 Institutions with the greatest output of core patents on “preparation technology for large-scale homogeneous high-entropy alloy”
| No. | Published patents | Percentage of published patents | Citations | Percentage of citations | Citations per patent | Institution |
| 1 | Beijing Inst Tech no logy | 34 | 3.78% | 127 | 4.44% | 3.74 |
| 2 | University of Science and Technology Beijing | 25 | 2.78% | 289 | 10.10% | 11.56 |
| 3 | Central South University | 23 | 2.56% | 114 | 3.98% | 4.96 |
| 4 | Xiangtan University | 23 | 2.56% | 47 | 1.64% | 2.04 |
| 5 | Jiangsu University of Technology | 23 | 2.56% | 19 | 0.66% | 0.83 |
| 6 | Tianjin University | 20 | 2.22% | 44 | 1.54% | 2.2 |
| 7 | Kunming University of Science and Technology | 19 | 2.11% | 44 | 1.54% | 2.32 |
| 8 | South China University of Technology | 16 | 1.78% | 104 | 3.64% | 6.5 |
| 9 | Lanzhou Institute of Chemical Physics Chinese Academy of Sciences | 16 | 1.78% | 52 | 1.82% | 3.25 |
| 10 | Taiyuan University of Technology | 16 | 1.78% | 52 | 1.82% | 3.25 |
《Figure 2.2.2》
Figure 2.2.2 Collaboration network among major countries in the engineering development front of “preparation technology for large-scale homogeneous high-entropy alloy”
《Figure 2.2.3》
Figure 2.2.3 Collaboration network among major institutions in the engineering development front of “preparation technology for large-scale homogeneous high-entropy alloy”
Participants of the Field Group
Experts of the Field Group
Directors: WANG Jingkang, XUE Qunji, LIU Jongtian
Deputy directors: LI Yanrong, LIU Zhongmin, MAO Xinping, NIE Zoren, TAN Tianwei, ZHOU Yu, Qu Ling Bo, YUAN Yingjin
Members of the working group
CHEN Biqiang, DENG Yuan, AN Yichao, YANG Zhihua, YE Mao, CAI Di, LI Daxin, WANG Jing, WANG Jingtao, YANG Xuejing,
YAO Changguo, ZHU Wei , CHENG Luli, HUANG Yaodong, LI Yanni, TU Xuan, WANG Aihong, ZHU Xiaowen,
Report writers
BAI Zhishan, CAI Di, CHEN Huidong, LI Junhua, LI Yulin, LIANG Shijing, LIU Qiang, SUN Chengli, SUN Mingyue, WAN Ying,
WANG Chao, WANG Xianfu, XU Zhi, YANG Yusen, YAO Changguo, ZHANG Taiyang, ZHANG Zhiguo, ZHAO Yixin, ZHU Xiaowen, ZHU Wei
Acknowledgements
We are grateful to the following scholars for their contributions to the project.
Beihang University
GUO Siming, HAN Guangyu, HU Shaoxiong, ZHANG Qingqing, ZHOU Jie
Beijing University of Chemical Technology
CHEN Changjing, LI Guofeng, QIN Xuan, WANG Dan
Central Research Institute of China Baowu Steel Group
GU Haifang, WANG yuan
Dalian Institute of Chemical Physics, Chinese Academy of Sciences
GAO Dunfeng, RONG Qian, WANG Yu
East China University of Science and Technology
CAO Jun, HE Xiaopeng, WANG Bingjie
Harbin Institute of Technology
LIU Qiang, JIA Dechang
Institute of Chemistry, Chinese Academy of Sciences
LI Yongfang
Northeastern University
WANG Cong, WANG Zhanjun
Tianjin University
HOU Jinjian, QIAO Jianjun
University of Electronic Science and Technology of China
LI Jie, PENG Bo, SUN Chengli, WANG Xianfu
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