The application of an external field is a promising method to control the microstructure of materials, leading to their improved performance. In the present paper, the strengthening and toughening behavior of some typical high-performance structural materials subjected to multifield coupling treatment, including electrostatic field, electro-pulse current, thermal field, and stress field, are reviewed in detail. In addition to the general observation that the plasticity of materials could be increased by multi-external fields, strength enhancement can be achieved by controlling atomic diffusion or phase transformations. The paper is not limited to the strengthening and toughening mechanisms of the multifield coupling effects on different types of structural materials but is intended to provide a generic method to improve both the strength and ductility of the materials. Finally, the prospects of the applications of multi-external fields have also been proposed based on current works.

Diamond/metal composites are widely used in aerospace and electronic packaging fields due to their outstanding high thermal conductivity and low expansion. However, the difference in chemical properties leads to interface incompatibility between diamond and metal, which has a considerable impact on the performance of the composites. To improve the interface compatibility between diamond and metal, it is necessary to modify the interface of composites. This paper reviews the experimental research on interface modification and the application of computational simulation in diamond/metal composites. Combining computational simulation with experimental methods is a promising way to promote diamond/metal composite interface modification research.

Copper-bearing biotite is a refractory copper mineral found on the surface of the Zambian Copperbelt. Biotite is a copper oxide from which copper is extracted by various methods, especially by leaching. Leaching is the process of extracting a substance from a solid material dissolved in a liquid. To improve the efficiency of the leaching process by a more effective method, a new method called ultrasonic-assisted acid leaching is proposed and applied in this study. Compared with regular acid leaching, the ultrasound method reduced the leaching time from 120 to 40 min, and sulfuric acid concentration reduced from 0.5 to 0.3 mol·L⁻¹. Besides, leaching temperature could be reduced from 75 to 45°C at the leaching rate of 78%. The mechanism analysis indicates that an ultrasonic wave can cause the delamination of a copper-bearing biotite and increase its specific surface area from 0.55 to 1.67 m²·g⁻¹. The results indicate that copper extraction from copper-bearing biotite by ultrasonic-assisted acid leaching is more effective than regular acid leaching. This study proposes a promising method for recycling valuable metals from phyllosilicate minerals.

A computational fluid dynamics (CFD) model was developed to accurately predict the flash reduction process, which is considered an efficient alternative ironmaking process. Laboratory-scale experiments were conducted in drop tube reactors to verify the accuracy of the CFD model. The reduction degree of ore particles was selected as a critical indicator of model prediction, and the simulated and experimental results were in good agreement. The influencing factors, including the particle size (20–110 μm), peak temperature (1250–1550°C), and reductive atmosphere (H₂/CO), were also investigated. The height variation lines indicated that small particles (50 μm) had a longer residence time (3.6 s) than large particles. CO provided a longer residence time (~1.29 s) than H₂ (~1.09 s). However, both the experimental and analytical results showed that the reduction degree of particles in CO was significantly lower than that in H₂ atmosphere. The optimum experimental particle size and peak temperature for the preparation of high-quality reduced iron were found to be 50 μm and 1350°C in H₂ atmosphere, and 40 μm and 1550°C in CO atmosphere, respectively.

The carbothermic reduction of vanadium titanomagnetite concentrate (VTC) with the assistance of Na₂CO₃ was conducted in an argon atmosphere between 1073 and 1473 K. X-ray diffraction and scanning electron microscopy were used to investigate the phase transformations during the reaction. By investigating the reaction between VTC and Na₂CO₃, it was concluded that molten Na₂CO₃ broke the structure of titanomagnetite by combining with the acidic oxides (Fe₂O₃, TiO₂, Al₂O₃, and SiO₂) to form a Na-rich melt and release FeO and MgO. Therefore, Na₂CO₃ accelerated the reduction rate. In addition, adding Na₂CO₃ also benefited the agglomeration of iron particles and the slag–metal separation by decreasing the viscosity of the slag. Thus, Na₂CO₃ assisted carbothermic reduction is a promising method for treating VTC at low temperatures.

As a part of the fundamental study related to the reduction smelting of spent lithium-ion batteries and ocean polymetallic nodules based on MnO–SiO₂ slags, this work investigated the activity coefficient of NiO in SiO₂-saturated MnO–SiO₂ slag and Al₂O₃-saturated MnO–SiO₂–Al₂O₃ slag at 1623 K with controlled oxygen partial pressure levels of 10⁻⁷, 10⁻⁶, and 10⁻⁵ Pa. Results showed that the solubility of nickel oxide in the slags increased with increasing oxygen partial pressure. The nickel in the MnO–SiO₂ slag and MnO–SiO₂–Al₂O₃ slag existed as NiO under experimental conditions. The addition of Al₂O₃ in the MnO–SiO₂ slag decreased the dissolution of nickel in the slag and increased the activity coefficient of NiO. Furthermore, the activity coefficient of NiO (γ_NiO), which is solid NiO, in the SiO₂ saturated MnO–SiO₂ slag and Al₂O₃ saturated MnO–SiO₂–Al₂O₃ slag at 1623 K can be respectively calculated as γ_NiO = 8.58w(NiO) + 3.18 and γ_NiO = 11.06w(NiO) + 4.07, respectively, where w(NiO) is the NiO mass fraction in the slag.

The effect of Al content (0.035wt%, 0.5wt%, 1wt%, and 2wt%) on the composition change of steel and slag as well as inclusion transformation of high manganese steel after it has equilibrated with CaO−SiO₂−Al₂O₃−MgO slag was studied using the method of slag/steel reaction. The experimental results showed that as the initial content of Al increased from 0.035wt% to 2wt%, Al gradually replaced Mn to react with SiO₂ in slag to avoid the loss of Mn due to the reaction; this process caused both Al₂O₃ in slag and Si in steel to increase while SiO₂ and MnO in slag to reduce. In addition, the type of inclusions also evolved as the initial Al content increased. The evolution route of inclusions was MnO → MnO−Al₂O₃−MgO → MgO → MnO−CaO−Al₂O₃−MgO and MnO−CaO−MgO. The shape of inclusions evolved from spherical to irregular, became faceted, and finally transformed to spherical. The average size of inclusions presented a trend that was increasing first and then decreasing. The transformation mechanism of inclusions was explored. As the initial content of Al increased, Mg and Ca were reduced from top slag into molten steel in sequence, which consequently caused the transformation of inclusions.

This study aims at providing systematically insights to clarify the impact of cathodic polarization on the stress corrosion cracking (SCC) behavior of 21Cr2NiMo steel. Slow-strain-rate tensile tests demonstrated that 21Cr2NiMo steel is highly sensitive to hydrogen embrittlement at strong cathodic polarization. The lowest SCC susceptibility occurred at −775 mV vs. SCE, whereas the SCC susceptibility was remarkably higher at potentials below −950 mV vs. SCE. Scanning electron microscopy (SEM) and electron backscattered diffraction (EBSD) revealed that the cathodic potential decline caused a transition from transgranular to intergranular mode in the fracture path. The intergranular mode transformed from bainite boundaries separation to prior austenitic grain boundaries separation under stronger cathodic polarization. Furthermore, corrosion pits promoted the nucleation of SCC cracks. In conclusion, with the decrease in the applied potential, the SCC mechanism transformed from the combination of hydrogen embrittlement and anodic dissolution to typical hydrogen embrittlement.

We investigated the effect of ‎the 2-mercaptobenzothiazole concentration on the sour-corrosion behavior of API ‎X60 pipeline steel in an environment containing H₂S at 25°C and in the presence of 0, 2.5, 5.0, 7.5, and 10.0 g/L of ‎2-mercaptobenzothiazole inhibitor. To examine this behavior, we conducted open-circuit potential (OCP), potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) tests. Energy dispersive spectroscopy and scanning electron microscopy were also used to analyze the corrosion products. The results of the OCP and potentiodynamic polarization tests revealed that ‎2-mercaptobenzothiazole reduces the speed of both the anodic and cathodic reactions. An assessment of the Gibbs free energy of the inhibitor (

) indicated that its value was less than −20 kJ·mol⁻¹ and greater than −40 kJ·mol⁻¹. Therefore, the adsorption of 2-mercaptobenzothiazole onto the surface of the API X60 pipeline steel occurs both physically and chemically, the latter of which is particularly intentional. In addition, as the

value was negative, we could conclude that the adsorption of 2-mercaptobenzothiazole onto the surface of the pipeline steel occurs spontaneously. The EIS results indicate that with the increase in the 2-mercaptobenzothiazole inhibitor concentration, the corrosion resistance of API X60 steel increases. An analysis of the corrosion products revealed that iron sulfide compounds form on the surface. In summary, the results showed that an increase in the inhibitor concentration results in a decrease in the corrosion rate and an increase in inhibitory efficiency. Additionally, we found that the 2-mercaptobenzothiazole adsorption process on the API X60 steel surfaces in an H₂S-containing environment follows the Langmuir adsorption isotherm and occurs spontaneously.

An excellent organolead halide perovskite film is important for the good performance of perovskite solar cells (PSCs). However, defects in perovskite crystals can affect the photovoltaic properties and stability of solar cells. To solve this problem, this study incorporated a complex of CdS and Cd(SCN₂H₄)₂Cl₂ into the CH₃NH₃PbI₃ active layer. The effects of different doping concentrations of CdS and Cd(SCN₂H₄)₂Cl₂ on the performance and stability of PSCs were analyzed. Results showed that doping appropriate incorporation concentrations of CdS and Cd(SCN₂H₄)₂Cl₂ in CH₃NH₃PbI₃ can improve the performance of the prepared solar cells. In specific, CdS and Cd(SCN₂H₄)₂Cl₂ can effectively passivate the defects in perovskite crystals, thereby suppressing the charge recombination in PSCs and promoting the charge extraction at the TiO₂/perovskite interface. Due to the reduction of perovskite crystal defects and the enhancement of compactness of the CdS:Cd(SCN₂H₄)₂Cl₂:CH₃NH₃PbI₃ composite film, the stability of PSCs is significantly improved.

Ceria (CeO₂) nanoparticles were successfully synthesized via a simple complex-precipitation route that employs cerium chloride as cerium source and citric acid as precipitant. The elemental analysis results of carbon, hydrogen, oxygen, and cerium in the precursors were calculated, and the results revealed that the precursors were composed of Ce(OH)₃, Ce(H₂Cit)₃, or CeCit. X-ray diffraction analysis showed that all ceria nanoparticles had a face-centered cubic structure. With the molar ratio of citric acid to Ce³⁺ (n) of 0.25 and pH of 5.5, the specific surface area of the sample reached the maximum value of 83.17 m²/g. Ceria nanoparticles were observed by scanning electron microscopy. Selected area electron diffraction patterns of several samples were obtained by transmission electron microscopy, and the crystal plane spacing of each low-exponent crystal plane was calculated. The ultraviolet (UV)–visible transmittance curve showed that ceria can absorb UV light and pass through visible light. Among all samples, the minimum average transmittance of ultraviolet radiation a (UVA) was 4.42%, and that of ultraviolet radiation b (UVB) was 1.56%.

NH₄ZnPO₄ powders were synthesized using a simple precipitation method at room temperature. The effects of polyvinyl pyrrolidone (PVP), polyvinyl alcohol (PVA), glucose, and hexadecyltrimethylammonium bromide (CTAB) solutions on the morphology and structure of the prepared samples were investigated. The phase composition and morphology of the prepared samples were characterized using X-ray diffraction and scanning electron microscopy, respectively. Depending on the polymer sources, the hexagonal structure prepared using non-surfactant of water completely changed to monoclinic structure when CTAB was added. X-ray absorption near-edge structure (XANES) and X-ray photoelectron spectroscopy (XPS) were performed to study the local structure and surface electronic structure of the prepared samples, confirming that the oxidation states of P and Zn ions are 5+ and 2+, respectively. On the basis of the results of inductively coupled plasma atomic emission spectroscopy (ICP-OES), the NH₄ZnPO₄ powders can be classified as a slow-release fertilizer where less than 15% of the ions were released in 24 h. A simple precipitation method using water, PVP, PVA, sucrose, and CTAB as a template can be used to synthesize NH₄ZnPO₄ powders. In addition, this method may be extended for the preparation of other oxide materials.

This study investigates the effect of graphene oxide (GO) on the mechanical and corrosion behavior, antibacterial performance, and cell response of Mg–Zn–Mn (MZM) nanocomposite. MZM/GO nanocomposites with different amounts of GO (i.e., 0.5wt%, 1.0wt%, and 1.5wt%) were fabricated by the semi-powder metallurgy method. The influence of GO on the MZM nanocomposite was analyzed through the hardness, compressive, corrosion, antibacterial, and cytotoxicity tests. The experimental results showed that, with the increase in the amount of GO (0.5wt% and 1.5wt%), the hardness value, compressive strength, and antibacterial performance of the MZM nanocomposite increased, whereas the cell viability and osteogenesis level decreased after the addition of 1.5wt% GO. Moreover, the electrochemical examination results showed that the corrosion behavior of the MZM alloy was significantly enhanced after encapsulation in 0.5wt% GO. In summary, MZM nanocomposites reinforced with GO can be used for implant applications because of their antibacterial performance and mechanical property.

To improve the properties of Babbitt alloys, Ni-coated-graphite-reinforced Babbitt metal composite specimens were prepared via selective laser melting (SLM), and the composites microstructures, mechanical properties, and tribological properties were studied through scanning electron microscopy (SEM), shear testing, and dry-sliding wear testing, respectively. The results showed that most of the nickel-coated graphite (NCGr) particles were distributed at the boundaries of laser beads in the cross section of the SLM composite specimens. Microcracks and microvoids formed at the boundaries of laser beads where NCGr particles accumulated. Both the shear strength and the friction coefficient of the SLM composite specimens decreased with increasing NCGr content. The shear strength and the friction coefficient of the SLM composite sample with 6wt% NCGr were approximately 20% and 33% lower than those of the NCGr-free sample, respectively. The friction mechanism changed from plastic shaping furrow to brittle cutting with increasing NCGr content. A practical Babbitt material with a lower friction coefficient and sufficient strength can be obtained by controlling the NCGr particle dispersion; this can be achieved by choosing NCGr particles with a thicker Ni layer and precisely controlling the laser energy input during the SLM process.

Stellite-21/WC nanopowders were deposited on Inconel through vibration-assisted laser cladding with different laser parameters. Optical and scanning electron microscopy, hardness measurements, and wear characterizations were employed to understand the microstructural and mechanical behaviors of the nanocomposites. Results showed that varying the cooling rate exerted remarkable effects on the microstructure of the as-cladded composites. Moreover, increasing the laser power from 150 W to 250 W increased the heat input and the dilutions. Dilution was affected by the scanning rate and powder feeding rate at a high laser power of 250 W. When WC nanoparticles were added as reinforcement, the dilution magnitude intensified while the hardness value increased from HV 350 to HV 700. The wear characterizations indicated that the composites containing 3wt% WC nanoparticles possessed the highest wear resistance.

Cement hydration is the underlying mechanism for the strength development in cement-based materials. The structural and electronic properties of calcium silicates should be elucidated to reveal their difference in hydration reactivity. Here, we comprehensively compared β-C₂S and M3-C₃S and investigated their structural properties and Bader charge in the unit cell, during surface reconstruction and after single water adsorption via density functional theory. We identified different types of atoms in β-C₂S and M3-C₃S by considering the bonding characteristics and Bader charge. We then divided the atoms into the following groups: for β-C₂S, Ca and O atoms divided into two and four groups, respectively; for M3-C₃S, Ca, O, and Si atoms divided into four, four, and three groups, respectively. Results revealed that the valence electron distribution on the surface was more uniform than that on the unit cell, indicating that some atoms became more reactive after surface relaxation. During water adsorption, the electrons of β-C₂S and M3-C₃S were transferred from the surface to the adsorbed water molecules through position redistribution and bond formation/breaking. On this basis, we explained why β-C₂S and M3-C₃S had activity differences. A type of O atom with special bond characteristics (no O–Si bonds) and high reactivity existed in the unit cell of M3-C₃S. Bader charge analysis showed that the reactivity of Ca and O atoms was generally higher in M3-C₃S than in β-C₂S. Ca/O atoms had average valence electron numbers of 6.437/7.550 in β-C₂S and 6.481/7.537 in M3-C₃S. Moreover, the number of electrons gained by water molecules in M3-C₃S at the surface was higher than that in β-C₂S. The average variations in the valence electrons of H₂O on β-C₂S and M3-C₃S were 0.041 and 0.226, respectively. This study further explains the differences in the hydration reactivity of calcium silicates and would be also useful for the design of highly reactive and environmentally friendly cements.

The ordinary cemented tailings backfill (CTB) is a cement-based composite prepared from tailings, cementitious materials, and water. In this study, a series of laboratory tests, including uniaxial compression, digital image correlation measurement, and scanning electron microscope characteristics of fiber-reinforced CTB (FRCTB), was conducted to obtain the uniaxial compressive strength (UCS), failure evolution, and microstructural characteristics of FRCTB specimens. The results show that adding fibers could increase the UCS values of the CTB by 6.90% to 32.76%. The UCS value of the FRCTB increased with the increase in the polypropylene (PP) fiber content. Moreover, the reinforcement effect of PP fiber on the CTB was better than that of glass fiber. The addition of fiber could increase the peak strain of the FRCTB by 0.39% to 1.45%. The peak strain of the FRCTB increased with the increase in glass fiber content. The failure pattern of the FRCTB was coupled with tensile and shear failure. The addition of fiber effectively inhibited the propagation of cracks, and the bridging effect of cracks by the fiber effectively improved the mechanical properties of the FRCTB. The findings in this study can provide a basis for the backfilling design and optimization of mine backfilling methods.

Two amino-functionalized diatomite (DE) composites modified by 3-aminopropyltriethoxysilane (APTS) or glycine (GLY) (i.e., APTS/DE and GLY/DE) were successfully synthesized via the wet chemical method for the time- and cost-efficient removal of indoor formaldehyde (HCHO). First, the optimal preparation conditions of the two composites were determined, and then their microstructures and morphologies were characterized and analyzed. Batch HCHO adsorption experiments with the two types of amino-modified DE composites were also conducted to compare their adsorption properties. Experimental results indicated that the pseudo-second-order kinetic and Langmuir isotherm models could well describe the adsorption process, and the maximum adsorption capacities of APTS/DE and GLY/DE prepared under optimal conditions at 20°C were 5.83 and 1.14 mg·g⁻¹, respectively. The thermodynamic parameters of the composites indicated that the adsorption process was spontaneous and exothermic. The abundant amine groups grafted on the surface of DE were derived from the Schiff base reaction and were essential for the high-efficient adsorption performance toward HCHO.