International Journal of Minerals, Metallurgy, and Materials最新文献

The one-ladle technology requires an efficient ironmaking and steelmaking interface. The scheduling of the hot metal ladle in the steel plant determines the overall operational efficiency of the interface. Considering the strong uncertainties of real-world production environments, this work studies the dynamic scheduling problem of hot metal ladles and develops a data-driven three-layer approach to solve this problem. A dynamic scheduling optimization model of the hot metal ladle operation with a minimum average turnover time as the optimization objective is also constructed. Furthermore, the intelligent perception of industrial scenes and autonomous identification of disturbances, adaptive configuration of dynamic scheduling strategies, and real-time adjustment of schedules can be realized. The upper layer generates a demand-oriented prescheduling scheme for hot metal ladles. The middle layer adaptively adjusts this scheme to obtain an executable schedule according to the actual supply–demand relationship. In the lower layer, three types of dynamic scheduling strategies are designed according to the characteristics of the dynamic disturbance in the model: real-time flexible fine-tuning, local machine adjustment, and global rescheduling. Case test using 24 h production data on a certain day during the system operation of a steel plant shows that the method and system can effectively reduce the fluctuation and operation time of the hot metal ladle and improve the stability of the ironmaking and steelmaking interface production rhythm. The data-driven dynamic scheduling strategy is feasible and effective, and the proposed method can improve the operation efficiency of hot metal ladles.

Natural minerals-based energy materials have attracted enormous attention because of the advantages of good materials consistency, high production, environmental friendliness, and low cost. The uniform distribution of grains can effectively inhibit the aggregation of active materials, improving lithium storage performance. In this work, natural graphite is modified by polyvinylpyrrolidone to obtain modified graphite with reduced size and better dispersion. Natural pyrite composite polyvinylpyrrolidone-modified graphite (pyrite/PG) material with uniform particle distribution is obtained by the ball milling process. The subsequent calcination process converts pyrite/PG into Fe_1−xS compounded with polyvinylpyrrolidone-modified graphite (Fe_1−xS/PG). The homogeneous grain distributions of active material can facilitate the faster transfer of electrons and promote the efficient utilization of active materials. The as-prepared Fe_1−xS/PG electrode exhibits a remarkably reversible specific capacity of 613.0 mAh·g⁻¹ at 0.2 A·g⁻¹ after 80 cycles and an excellent rate capability of 523.0 mAh·g⁻¹ at 5 A·g⁻¹. Even at a higher current density of 10 A·g⁻¹, it can deliver a specific capacity of 348.0 mAh·g⁻¹. Moreover, the dominant pseudocapacitance in redox reactions accounts for the impressive rate and cycling stability. This work provides a low-cost and facile method to fabricate natural mineral-based anode materials and apprise readers about the impact of uniform particle distribution on lithium storage performance.

As a heat-resistant wave-absorbing material, silicon carbide (SiC) aerogel has become a research hotspot at present. However, the most common silicon sources are organosilanes, which are costly and toxic. In this work, SiC aerogels were successfully prepared by using water glass as the silicon source. Specifically, the microstructure and chemical composition of SiC aerogels were controlled by adjusting the Si to C molar ratio during the sol–gel process, and the effect on SiC aerogel microwave absorption properties was investigated. The SiC aerogels prepared with Si:C molar ratio of 1:1 have an effective electromagnetic wave absorption capacity, with a minimum reflection loss value of −46.30 dB at 12.88 GHz and an effective frequency bandwidth of 4.02 GHz. They also have good physical properties, such as the density of 0.0444 g/cm³, the thermal conductivity of 0.0621 W/(m·K), and the specific surface area of 1099 m²/g. These lightweight composites with microwave-absorbing properties and low thermal conductivity can be used as thermal protection materials for space shuttles and reusable carriers.

This monograph presents an overview of friction stir processing (FSP) of surface metal-matrix composites (MMCs) using the AZ91 magnesium alloy. The reported results in relation to various reinforcing particles, including silicon carbide (SiC), alumina (Al₂O₃), quartz (SiO₂), boron carbide (B₄C), titanium carbide (TiC), carbon fiber, hydroxyapatite (HA), in-situ formed phases, and hybrid reinforcements are summarized. AZ91 composite fabricating methods based on FSP are explained, including groove filling (grooving), drilled hole filling, sandwich method, stir casting followed by FSP, and formation of in-situ particles. The effects of introducing second-phase particles and FSP process parameters (e.g., tool rotation rate, traverse speed, and the number of passes) on the microstructural modification, grain refinement, homogeneity in the distribution of particles, inhibition of grain growth, mechanical properties, strength–ductility trade-off, wear/tribological behavior, and corrosion resistance are discussed. Finally, useful suggestions for future work are proposed, including focusing on the superplasticity and superplastic forming, metal additive manufacturing processes based on friction stir engineering (such as additive friction stir deposition), direct FSP, stationary shoulder FSP, correlation of the dynamic recrystallization (DRX) grain size with the Zener–Hollomon parameter similar to hot deformation studies, process parameters (such as the particle volume fraction and external cooling), and common reinforcing phases such as zirconia (ZrO₂) and carbon nanotubes (CNTs).

In general, malachite is recovered via sulfidization–xanthate flotation, although many unsatisfactory flotation indexes are frequently obtained as a result of the presence of associated calcite. This phenomenon occurs because the dissolved components of malachite and calcite affect the flotation behavior of both minerals. In this study, the effect of the dissolved components derived from malachite and calcite on the flotation behavior and surface characteristics of both minerals was investigated. Flotation tests indicated that malachite recovery decreased when the calcite supernatant was introduced, while the presence of the malachite supernatant increased the recovery of calcite. Dissolution and adsorption tests, along with zeta potential measurements, X-ray photoelectron spectroscopy, Fourier transform infrared spectrometry, and time-of-flight secondary ion mass spectrometry demonstrated that the Ca species in the calcite supernatant were adsorbed on the malachite surface, which hindered the interaction of Na₂S with malachite, thereby resulting in the insufficient adsorption of sodium isoamyl xanthate (NaIX) on the surface of malachite. By contrast, the Cu species in the malachite supernatant were adsorbed on the calcite surface, and they provided active sites for the subsequent adsorption of Na₂S and NaIX.

The macroscopic characteristics of molten salts are governed by their microstructures. Research on the structures of molten salts provides the foundation for a full understanding of the physicochemical properties of molten salts as well as a deeper analysis of the microscopic electrolysis process in molten salts. Information about the microstructure of matter can be obtained with the help of several speculative and experimental procedures. In this review, the advantages and disadvantages of the various test procedures used to determine the microstructures of molten salts are compared. The typical coordination configurations of metal ions in molten salt systems are also summarized. Furthermore, the impact of temperature, anions, cations, and metal oxides (O²⁻) on the structures of molten salts is discussed in detail. The accuracy and completeness of the information on molten salt structures need to be investigated by the integration of multiple methods and interdisciplinary fields. Information on the microstructure and coordination of molten salts deepens the understanding of the elementary elements of the microstructure of matter. This paper, which is based on the review of the coordination states of metal ions in molten salts, is hoped to inspire researchers to explore the inter-relationship between the microstructure and macroscopic properties of materials.

This study investigated the influence of band microstructure induced by centerline segregation on carbide precipitation behavior and toughness in an 80 mm-thick 1 GPa low-carbon low-alloy steel plate. The quarter-thickness (1/4t) and half-thickness (1/2t) regions of the plate exhibited similar ductility and toughness after quenching. After tempering, the 1/4t region exhibited ∼50% and ∼25% enhancements in both the total elongation and low-temperature toughness at −40°C, respectively, without a decrease in yield strength, whereas the toughness of the 1/2t region decreased by ∼46°%. After quenching, both the 1/4t and 1/2t regions exhibited lower bainite and lath martensite concentrations, but only the 1/2t region exhibited microstructure bands. Moreover, the tempered 1/4t region featured uniformly dispersed short rod-like M₂₃C₆ carbides, and spherical MC precipitates with diameters of ∼20–100 nm and <20 nm, respectively. The uniformly dispersed nanosized M₂₃C₆ carbides and MC precipitates contributed to the balance of high strength and high toughness. The band microstructure of the tempered 1/2t region featured a high density of large needle-like M₃C carbides. The length and width of the large M₃C carbides were ∼200–500 nm and ∼20–50 nm, respectively. Fractography analysis revealed that the high density of large carbides led to delamination cleavage fracture, which significantly deteriorated toughness.

CoFe₂O₄ has been widely used for electromagnetic wave absorption owing to its high Snoek limit, high anisotropy, and suitable saturation magnetization; however, its inherent shortcomings, including low dielectric loss, high density, and magnetic agglomeration, limit its application as an ideal absorbent. This study investigated a microstructure regulation strategy to mitigate the inherent disadvantages of pristine CoFe₂O₄ synthesized via a sol–gel auto-combustion method. A series of CoFe₂O₄ foams (S0.5, S1.0, and S1.5, corresponding to foams with citric acid (CA)-to-Fe(NO₃)₃·9H₂O molar ratios of 0.5, 1.0, and 1.5, respectively) with two-dimensional (2D) curved surfaces were obtained through the adjustment of CA-to-Fe³⁺ ratio, and the electromagnetic parameters were adjusted through morphology regulation. Owing to the appropriate impedance matching and conductance loss provided by moderate complex permittivity, the effective absorption bandwidth (EAB) of S0.5 was as high as 7.3 GHz, exceeding those of most CoFe₂O₄-based absorbents. Moreover, the EAB of S1.5 reached 5.0 GHz (8.9–13.9 GHz), covering most of the X band, owing to the intense polarization provided by lattice defects and the heterogeneous interface. The three-dimensional (3D) foam structure circumvented the high density and magnetic agglomeration issues of CoFe₂O₄ nanoparticles, and the good conductivity of 2D curved surfaces could effectively elevate the complex permittivity to ameliorate the dielectric loss of pure CoFe₂O₄. This study provides a novel idea for the theoretical design and practical production of lightweight and broadband pure ferrites.

The low-reactivity mold flux with low SiO₂ content is considered suitable for the continuous casting of high-aluminum steel since it can significantly reduce the reaction between Al in steel and SiO₂ in mold flux. However, the traditional low-reactivity mold flux still presents some problems such as high viscosity and strong crystallization tendency. In this study, the co-addition of Li₂O and B₂O₃ in CaO–Al₂O₃–10wt%SiO₂ based low-reactivity mold flux was proposed to improve properties of mold flux for high-aluminum steel, and the effect of Li₂O replacing B₂O₃ on properties of mold flux was investigated. The viscosity of the mold flux with 2wt% Li₂O and 6wt% B₂O₃ reached a minimum value of 0.07 Pa·s. The break temperature and melting point showed a similar trend with the viscosity. Besides, the melt structure and precipitation of the crystalline phase were studied using Raman and X-ray diffraction spectra to better understand the evolution of viscosity. It demonstrated that with increasing Li₂O content in the mold flux from 0 to 6wt%, the degree of polymerization of aluminate and the aluminosilicate network structure increased because of increasing Li⁺ released by Li₂O, indicating the added Li₂O was preferentially associated with Al³⁺ as a charge compensator. The precipitation of LiAlO₂ crystalline phase gradually increased with the replacement of B₂O₃ by Li₂O. Therefore, Li₂O content should be controlled below 2wt% to avoid LiAlO₂ precipitation, which was harmful to the continuous casting of high-aluminum steels.

Tetragonal barium titanate was synthesized from barium hydroxide octahydrate and titanium tetrachloride through a simple one-step hydrothermal method. The effect of different solvents on the crystal structure and morphology of barium titanate nanoparticles during the hydrothermal process was investigated. Except for ethylene glycol/water solvent, impurity-free barium titanate was synthesized in pure water, methanol/water, ethanol/water, and isopropyl alcohol/water mixed solvents. Compared with other alcohols, ethanol promotes the formation of a tetragonal structure. In addition, characterization studies confirm that particles synthesized in methanol/water, ethanol/water, and isopropyl alcohol/water mixed solvents are smaller in size than those synthesized in pure water. In the case of alcohol-containing solvents, the particle size decreases in the order of isopropanol, ethanol, and methanol. Among all the media used in this study, ethanol/water is considered the optimum reaction media for barium titanate with high tetragonality (defined as the ratio of two lattice parameters c and a, c/a = 1.0088) and small average particle size (82 nm), which indicates its great application potential in multilayer ceramic capacitors.