BiFeO₃ (BFO) has received considerable attention as a lead-free ferroelectric film due to its large theoretical remnant polarization. However, BFO suffers from a large leakage current, resulting in poor ferroelectric properties. Herein, the sol–gel method was used to deposit a series of BFO-based thin films on fluorine-doped tin oxide substrates, and the effects of the substitution of the elements Co, Cu, Mn (B-site) and Sm, Eu, La (A-site) on the crystal structure, ferroelectricity, and leakage current of the BFO-based thin films were investigated. Results confirmed that lattice distortion by X-ray diffraction can be attributed to the substitution of individual elements in the BFO-based films. Sm and Eu substitutions contribute to the lattice distortion in a pseudo-cubic structure, while La is biased toward pseudo-tetragonal. Piezoelectric force microscopy confirmed that reversible switching of ferroelectric domains by nearly 180° can be realized through the prepared films. The ferroelectric hysteresis loops showed that the order for the polarization contribution is as follows: Cu > Co > Mn (B-site), Sm > La > Eu (A-site). The current density voltage curves indicated that the order for leakage contribution is as follows: Mn < Cu < Co (B-site), La < Eu < Sm (A-site). Scanning electron microscopy showed that the introduction of Cu elements facilitates the formation of dense grains, and the grain size distribution statistics proved that La element promotes the reduction of grain size, leading to the increase of grain boundaries and the reduction of leakage. Finally, a Bi_0.985Sm_0.045La_0.03Fe_0.96Co_0.02Cu_0.02O₃ (SmLa-CoCu) thin film with a qualitative leap in the remnant polarization from 25.5 (Bi_0.985Sm_0.075FeO₃) to 98.8 µC/cm² (SmLa-CoCu) was prepared through the synergistic action of Sm, La, Co, and Cu elements. The leakage current is also drastically reduced from 160 to 8.4 mA/cm² at a field strength of 150 kV/cm. Thus, based on the increasing entropy strategy of chemical engineering, this study focuses on enhancing ferroelectricity and decreasing leakage current, providing a promising path for the advancement of ferroelectric devices.

Developing high ionic conducting electrolytes is crucial for applying proton-conducting fuel cell (PCFCs) practically. The current study investigates the effect of alumina on the structural, morphological, electrical, and electrochemical properties of CeO₂. Lattice oxygen vacancies are induced in CeO₂ by a general doping concept that enables fast ionic conduction at low-temperature ranges (300–500°C) for PCFCs. Rietveld refinement of the X-ray diffraction (XRD) patterns established the pure cubic fluorite structure of Al-doped CeO₂ (ADC) samples and confirmed Al ions’ fruitful integration in the CeO₂ lattice. The electronic structure of the alumina-doped ceria of the materials (10ADC, 20ADC, and 30ADC) has been investigated. As a result, it was found that the best composition of 30ADC-based electrolytes induced maximum lattice oxygen vacancies. The corresponding PCFC exhibited a maximum power output of 923 mW/cm² at 500°C. Moreover, the investigation proves the proton-conducting ability of alumina-doped ceria-based fuel cells by using an oxide ion-blocking layer.

The global importance of lithium-ion batteries (LIBs) has been increasingly underscored with the advancement of high-performance energy storage technologies. However, the end-of-life of these batteries poses significant challenges from environmental, economic, and resource management perspectives. This review paper focuses on the pyrometallurgy-based recycling process of lithium-ion batteries, exploring the fundamental understanding of this process and the importance of its optimization. Centering on the high energy consumption and emission gas issues of the pyrometallurgical recycling process, we systematically analyzed the capital-intensive nature of this process and the resulting technological characteristics. Furthermore, we conducted an in-depth discussion on the future research directions to overcome the existing technological barriers and limitations. This review will provide valuable insights for researchers and industry stakeholders in the battery recycling field.

Given the carbon peak and carbon neutrality era, there is an urgent need to develop high-strength steel with remarkable hydrogen embrittlement resistance. This is crucial in enhancing toughness and ensuring the utilization of hydrogen in emerging iron and steel materials. Simultaneously, the pursuit of enhanced metallic materials presents a cross-disciplinary scientific and engineering challenge. Developing high-strength, toughened steel with both enhanced strength and hydrogen embrittlement (HE) resistance holds significant theoretical and practical implications. This ensures secure hydrogen utilization and further carbon neutrality objectives within the iron and steel sector. Based on the design principles of high-strength steel HE resistance, this review provides a comprehensive overview of research on designing surface HE resistance and employing nanosized precipitates as intragranular hydrogen traps. It also proposes feasible recommendations and prospects for designing high-strength steel with enhanced HE resistance.

Rare-earth silicates are promising environmental barrier coatings (EBCs) that can protect SiC_f/SiC_m substrates in next-generation gas turbine blades. Notably, RE₂Si₂O₇ (RE = Yb and Ho) shows potential as an EBC due to its coefficient of thermal expansion (CTE) compatible with substrates and high resistance to water vapor corrosion. The target operating temperature for next-generation turbine blades is 1400°C. Corrosion is inevitable during adhesion to molten volcanic ash, and thus, understanding the corrosion behavior of the material is crucial to its reliability. This study investigates the high-temperature corrosion behavior of sintered RE₂Si₂O₇ (RE = Yb and Ho). Samples were prepared using a solid-state reaction and hot-press method. They were then exposed to volcanic ash at 1400°C for 2, 24, and 48 h. After 48 h of exposure, volcanic ash did not react with Yb₂Si₂O₇ but penetrated its interior, causing damage. Meanwhile, Ho₂Si₂O₇ was partially dissolved in the molten volcanic ash, forming a reaction zone that prevented volcanic ash melts from penetrating the interior. With increasing heat treatment time, the reaction zone expanded, and the thickness of the acicular apatite grains increased. The Ca:Si ratios in the residual volcanic ash were mostly unchanged for Yb₂Si₂O₇ but decreased considerably over time for Ho₂Si₂O₇. The Ca in volcanic ash was consumed and formed apatite, indicating that RE³⁺ ions with large ionic radii (Ho > Yb) easily precipitated apatite from the volcanic ash.

Short-range ordering (SRO) is one of the most important structural features of high entropy alloys (HEAs). However, the chemical and structural analyses of SROs are very difficult due to their small size, complexed compositions, and varied locations. Transmission electron microscopy (TEM) as well as its aberration correction techniques are powerful for characterizing SROs in these compositionally complex alloys. In this short communication, we summarized recent progresses regarding characterization of SROs using TEM in the field of HEAs. By using advanced TEM techniques, not only the existence of SROs was confirmed, but also the effect of SROs on the deformation mechanism was clarified. Moreover, the perspective related to application of TEM techniques in HEAs are also discussed.

Bioderived carbon materials have garnered considerable interest in the fields of microwave absorption and shielding due to their reproducibility and environmental friendliness. In this study, KOH was evenly distributed on biomass Tremella using the swelling induction method, leading to the preparation of a three-dimensional network-structured hierarchical porous carbon (HPC) through carbonization. The achieved microwave absorption intensity is robust at −47.34 dB with a thin thickness of 2.1 mm. Notably, the widest effective absorption bandwidth, reaching 7.0 GHz (11–18 GHz), is attained at a matching thickness of 2.2 mm. The exceptional broadband and reflection loss performance are attributed to the 3D porous networks, interface effects, carbon network defects, and dipole relaxation. HPC has outstanding absorption characteristics due to its excellent impedance matching and high attenuation constant. The uniform pore structures considerably optimize the impedance-matching performance of the material, while the abundance of interfaces and defects enhances the dielectric loss, thereby improving the attenuation constant. Furthermore, the impact of carbonization temperature and swelling rate on microwave absorption performance was systematically investigated. This research presents a strategy for preparing absorbing materials using biomass-derived HPC, showcasing considerable potential in the field of electromagnetic wave absorption.

NiMZn/C@melamine sponge-derived carbon (MSDC) composites (M = Co, Fe, and Mn) were prepared by a vacuum pumping solution method followed by carbonization. A large number of carbon nanotubes (CNTs) homogeneously attached to the surfaces of the three-dimensional cross-linked of the sponge-derived carbon in the NiCoZn/C@MSDC composite, and CNTs were detected in the NiFeZn/C@MSDC and NiMnZn/C@MSDC composites. Ni₃ZnC_0.7, Ni₃Fe, and MnO in-situ formed in the NiFeZn/C@MSDC and NiMnZn/C@MSDC composites. The CNTs in the NiCoZn/C@MSDC composite efficiently modulated its complex permittivity. Thus, the composite exhibited the best performance among the composites, with the minimum reflection loss (RL_min) of −33.1 dB at 18 GHz and thickness of 1.4 mm. The bandwidth for RL of ≤−10 dB was up to 5.04 GHz at the thickness of 1.7 mm and loading of 25wt%. The optimized impedance matching, enhanced interfacial and dipole polarization, remarkable conduction loss, and multiple reflections and scattering of the incident microwaves improved the microwave absorption performance. The effects of Co, Ni, and Fe on the phase and morphology provided an alternative way for developing highly efficient and broadband microwave absorbers.

Nickel-based superalloys are extensively used in the crucial hot-section components of industrial gas turbines, aeronautics, and astronautics because of their excellent mechanical properties and corrosion resistance at high temperatures. Fusion welding serves as an effective means for joining and repairing these alloys; however, fusion welding-induced liquation cracking has been a challenging issue. This paper comprehensively reviewed recent liquation cracking, discussing the formation mechanisms, cracking criteria, and remedies. In recent investigations, regulating material composition, changing the preweld heat treatment of the base metal, optimizing the welding process parameters, and applying auxiliary control methods are effective strategies for mitigating cracks. To promote the application of nickel-based superalloys, further research on the combination impact of multiple elements on cracking prevention and specific quantitative criteria for liquation cracking is necessary.

Constructing a built-in electric field has emerged as a key strategy for enhancing charge separation and transfer, thereby improving photoelectrochemical performance. Recently, considerable efforts have been devoted to this endeavor. This review systematically summarizes the impact of built-in electric fields on enhancing charge separation and transfer mechanisms, focusing on the modulation of built-in electric fields in terms of depth and orderliness. First, mechanisms and tuning strategies for built-in electric fields are explored. Then, the state-of-the-art works regarding built-in electric fields for modulating charge separation and transfer are summarized and categorized according to surface and interface depth. Finally, current strategies for constructing bulk built-in electric fields in photoelectrodes are explored, and insights into future developments for enhancing charge separation and transfer in high-performance photoelectrochemical applications are provided.

The precipitation of Fe₃O₄ particles and the accompanied formation of Fe₃O₄-wrapped copper structure are the main obstacles to copper recovery from the molten slag during the pyrometallurgical smelting of copper concentrates. Herein, the commercial powdery pyrite or anthracite is replaced with pyrite–anthracite pellets as the reductants to remove a large amount of Fe₃O₄ particles in the molten slag, resulting in a deep fracture in the Fe₃O₄-wrapped copper microstructure and the full exposure of the copper matte cores. When 1wt% composite pellet is used as the reductant, the copper matte droplets are enlarged greatly from 25 µm to a size observable by the naked eye, with the copper content being enriched remarkably from 1.2wt% to 4.5wt%. Density functional theory calculation results imply that the formation of the Fe₃O₄-wrapped copper structure is due to the preferential adhesion of Cu₂S on the Fe₃O₄ particles. X-ray photoelectron spectroscopy, Fourier transform infrared spectrometer (FTIR), and Raman spectroscopy results all reveal that the high-efficiency conversion of Fe₃O₄ to FeO can decrease the volume fraction of the solid phase and promote the depolymerization of silicate network structure. As a consequence, the settling of copper matte droplets is enhanced due to the lowered slag viscosity, contributing to the high efficiency of copper–slag separation for copper recovery. The results provide new insights into the enhanced in-situ enrichment of copper from molten slag.

Aqueous zinc-ion batteries (AZIBs) show great potential for applications in grid-scale energy storage, given their intrinsic safety, cost effectiveness, environmental friendliness, and impressive electrochemical performance. However, strong electrostatic interactions exist between zinc ions and host materials, and they hinder the development of advanced cathode materials for efficient, rapid, and stable Zn-ion storage. MXenes and their derivatives possess a large interlayer spacing, excellent hydrophilicity, outstanding electronic conductivity, and high redox activity. These materials are considered “rising star” cathode candidates for AZIBs. This comprehensive review discusses recent advances in MXenes as AZIB cathodes from the perspectives of crystal structure, Zn-storage mechanism, surface modification, interlayer engineering, and conductive network design to elucidate the correlations among their composition, structure, and electrochemical performance. This work also outlines the remaining challenges faced by MXenes for aqueous Zn-ion storage, such as the urgent need for improved toxic preparation methods, exploration of potential novel MXene cathodes, and suppression of layered MXene restacking upon cycling, and introduces the prospects of MXene-based cathode materials for high-performance AZIBs.

Hydrogen-enriched blast furnace ironmaking has become an essential route to reduce CO₂ emissions in the ironmaking process. However, hydrogen-enriched reduction produces large amounts of H₂O, which places new demands on coke quality in a blast furnace. In a hydrogen-rich blast furnace, the presence of H₂O promotes the solution loss reaction. This result improves the reactivity of coke, which is 20%–30% higher in a pure H₂O atmosphere than in a pure CO₂ atmosphere. The activation energy range is 110–300 kJ/mol between coke and CO₂ and 80–170 kJ/mol between coke and H₂O. CO₂ and H₂O are shown to have different effects on coke degradation mechanisms. This review provides a comprehensive overview of the effect of H₂O on the structure and properties of coke. By exploring the interactions between H₂O and coke, several unresolved issues in the field requiring further research were identified. This review aims to provide valuable insights into coke behavior in hydrogen-rich environments and promote the further development of hydrogen-rich blast furnace ironmaking processes.

The A₂B₂O₇-type rare earth zirconate compounds have been considered as promising candidates for thermal barrier coating (TBC) materials because of their low sintering rate, improved phase stability, and reduced thermal conductivity in contrast with the currently used yttria-partially stabilized zirconia (YSZ) in high operating temperature environments. This review summarizes the recent progress on rare earth zirconates for TBCs that insulate high-temperature gas from hot-section components in gas turbines. Based on the first principles, molecular dynamics, and new data-driven calculation approaches, doping and high-entropy strategies have now been adopted in advanced TBC materials design. In this paper, the solid-state heat transfer mechanism of TBCs is explained from two aspects, including heat conduction over the full operating temperature range and thermal radiation at medium and high temperature. This paper also provides new insights into design considerations of adaptive TBC materials, and the challenges and potential breakthroughs are further highlighted for extreme environmental applications. Strategies for improving thermophysical performance are proposed in two approaches: defect engineering and material compositing.

Magnesium and magnesium alloy foils have great potential for application in battery anodes, electromagnetic shielding, optics and acoustics, and biology because of their excellent specific damping, internal dissipation coefficients, magnetic and electrical conductivities, as well as high theoretical specific capacity. However, magnesium alloys exhibit poor deformation ability due to their hexagonal close-packed crystal structure. Preparing magnesium and magnesium alloy foils with thicknesses of less than 0.1 mm is difficult because of surface oxidation and grain growth at high temperatures or severe anisotropy after cold rolling that leads to cracks. Numerous methods have been applied to prepare magnesium alloy foils. They include warm rolling, cold rolling, accumulative roll bonding, electric plastic rolling, and on-line heating rolling. Defects of magnesium and magnesium alloy foils during preparation, such as edge cracks and breakage, are important factors for consideration. Herein, the current status of the research on magnesium and magnesium alloy foils is summarized from the aspects of foil preparation, defect control, performance characterization, and application prospects. The advantages and disadvantages of different preparation methods and defect (edge cracks and breakage) mechanisms in the preparation of foils are identified.