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

Electric arc furnace dust (EAFD) is a hazardous waste but can also be a potential secondary resource for valuable metals, such as Zn and Fe. Given the increased awareness of carbon emission reduction, energy conservation, and environmental protection, hydrometallurgical technologies for the detoxification and resource use of EAFD have been developing rapidly. This work summarizes the generation mechanisms, compositions, and characteristics of EAFD and presents a critical review of various hydrometallurgical treatment methods for EAFD, e.g., acid leaching, alkaline leaching, salt leaching, and pretreatment-enhanced leaching methods. Simultaneously, the phase transformation mechanisms of zinc-containing components in acid and alkali solutions and pretreatment processes are expounded. Finally, two novel combined methods, i.e., oxygen pressure sulfuric acid leaching combined with composite catalyst preparation, and synergistic roasting of EAFD and municipal solid waste incineration fly ash combined with alkaline leaching, are proposed, which can provide future development directions to completely recycling EAFD by recovering valuable metals and using zinc residue.

The effect of Na-excess content in the precursor on the structural and electrochemical performances of sodium nickel manganese oxide (NNMO) prepared by sol–gel and electrospinning methods is investigated in this paper. X-ray diffraction results of the prepared NNMO without adding Na-excess content indicate sodium loss, while the mixed phase of P2/O′3-type layered NNMO presented after adding Na-excess content. Compared with the sol–gel method, the secondary phase of NiO is more suppressed by using the electrospinning method, which is further confirmed by field emission scanning electron microscope images. N₂ adsorption–desorption isotherms show no remarkably difference in specific surface areas between different preparation methods and Na-excess contents. The analysis of X-ray absorption near edge structure indicates that the oxidation states of Ni and Mn are +2 and +4, respectively. For the electrochemical properties, superior electrochemical performance is observed in the NNMO electrode with a low Na-excess content of 5wt%. The highest specific capacitance is 36.07 F·g⁻¹ at 0.1 A·g⁻¹ in the NNMO electrode prepared by using the sol–gel method. By contrast, the NNMO electrode prepared using the electrospinning method with decreased Na-excess content shows excellent cycling stability of 100% after charge–discharge measurements for 300 cycles. Therefore, controlling the Na excess in the precursor together with the preparation method is important for improving the electrochemical performance of Na-based electrode materials in supercapacitors.

Galena (PbS) and chalcopyrite (CuFeS₂) are sulfide minerals that exhibit good floatability characteristics. Thus, efficiently separating them via common flotation is challenging. Herein, a new method of surface sulfuric acid corrosion in conjunction with flotation separation was proposed, and the efficient separation of galena and chalcopyrite was successfully realized. Contact angle test results showed a substantial decrease in surface contact angle and a selective inhibition of surface floatability for corroded galena. Meanwhile, the contact angle and floatability of corroded chalcopyrite remained almost unaffected. Scanning electron microscope results confirmed that sulfuric acid corrosion led to the formation of a dense oxide layer on the galena surface, whereas the chalcopyrite surface remained unaltered. X-ray photoelectron spectroscopy results showed that the chemical state of S²⁻ on the surface of corroded galena was oxidized to SO ²⁻₄ . A layer of hydrophilic PbSO₄ was formed on the surface, leading to a sharp decrease in galena floatability. Meanwhile, new hydrophobic CuS₂, CuS, and Cu_1−xFe_1−y,S_2−z species exhibiting good floatability were generated on the chalcopyrite surface. Finally, theoretical analysis results were further verified by corrosion–flotation separation experiments. The galena–chalcopyrite mixture was completely separated via flotation separation under appropriate corrosion acidity, corrosion temperature, and corrosion time. A novel approach has been outlined in this study, providing potential applications in the efficient separation of refractory copper–lead sulfide ore.

SiC nanowires are excellent high-temperature electromagnetic wave (EMW) absorbing materials. However, their polymer matrix composites are difficult to work at temperatures above 300°C, while their ceramic matrix composites must be prepared above 1000°C in an inert atmosphere. Thus, for addressing the abovementioned problems, SiC/low-melting-point glass composites were well designed and prepared at 580°C in an air atmosphere. Based on the X-ray diffraction results, SiC nanowires were not oxidized during air atmosphere sintering because of the low sintering temperature. Additionally, SiC nanowires were uniformly distributed in the glass matrix material. The composites exhibited good mechanical and EMW absorption properties. As the filling ratio of SiC nanowires increased from 5wt% to 20wt%, the Vickers hardness and flexural strength of the composite reached HV 564 and 213 MPa, which were improved by 27.7% and 72.8%, respectively, compared with the low-melting-point glass. Meanwhile, the dielectric loss and EMW absorption ability of SiC nanowires at 8.2–12.4 GHz were also gradually improved. The dielectric loss ability of low-melting-point glass was close to 0. However, when the filling ratio of SiC nanowires was 20wt%, the composite showed a minimum reflection loss (RL) of −20.2 dB and an effective absorption (RL ≤ −10 dB) bandwidth of 2.3 GHz at an absorber layer thickness of 2.3 mm. The synergistic effect of polarization loss and conductivity loss in SiC nanowires was responsible for this improvement.

The anisotropy induced by rock bedding structures is usually manifested in the mechanical behaviors and failure modes of rocks. Brazilian tests are conducted for seven groups of shale specimens featuring different bedding angles. Acoustic emission (AE) and digital image correlation (DIC) technologies are used to monitor the in-situ failure of the specimens. Furthermore, the crack morphology of damaged samples is observed through scanning electron microscopy (SEM). Results reveal the structural dependence on the tensile mechanical behavior of shales. The shale disk exhibits compression in the early stage of the experiment with varying locations and durations. The location of the compression area moves downward and gradually disappears when the bedding angle increases. The macroscopic failure is well characterized by AE event location results, and the dominant frequency distribution is related to the bedding angle. The b-value is found to be stress-dependent. The crack turning angle between layers and the number of cracks crossing the bedding both increase with the bedding angle, indicating competition between crack propagations. SEM results revealed that the failure modes of the samples can be classified into three types: tensile failure along beddings with shear failure of the matrix, ladder shear failure along beddings with tensile failure of the matrix, and shear failure along multiple beddings with tensile failure of the matrix.

Blast furnace (BF) ironmaking is the most typical “black box” process, and its complexity and uncertainty bring forth great challenges for furnace condition judgment and BF operation. Rich data resources for BF ironmaking are available, and the rapid development of data science and intelligent technology will provide an effective means to solve the uncertainty problem in the BF ironmaking process. This work focused on the application of artificial intelligence technology in BF ironmaking. The current intelligent BF ironmaking technology was summarized and analyzed from five aspects. These aspects include BF data management, the analyses of time delay and correlation, the prediction of BF key variables, the evaluation of BF status, and the multi-objective intelligent optimization of BF operations. Solutions and suggestions were offered for the problems in the current progress, and some outlooks for future prospects and technological breakthroughs were added. To effectively improve the BF data quality, we comprehensively considered the data problems and the characteristics of algorithms and selected the data processing method scientifically. For analyzing important BF characteristics, the effect of the delay was eliminated to ensure an accurate logical relationship between the BF parameters and economic indicators. As for BF parameter prediction and BF status evaluation, a BF intelligence model that integrates data information and process mechanism was built to effectively achieve the accurate prediction of BF key indexes and the scientific evaluation of BF status. During the optimization of BF parameters, low risk, low cost, and high return were used as the optimization criteria, and while pursuing the optimization effect, the feasibility and site operation cost were considered comprehensively. This work will help increase the process operator’s overall awareness and understanding of intelligent BF technology. Additionally, combining big data technology with the process will improve the practicality of data models in actual production and promote the application of intelligent technology in BF ironmaking.

Sepiolite (ST) was used as a supporting matrix in compiste phase change materials (PCMs) due to its unique microstructure, good thermal stability, and other raw material advantages. In this paper, microwave acid treatment were innovatively used for the modification of sepiolite. The modified sepiolite (ST_m) obtained in different hydrochloric acid concentrations (0.25, 0.5, 0.75, and 1.0 mol·L⁻¹) was added to stearic acid (SA) via vacuum impregnation method. The thermophysical properties of the composites were changed by varying the hydrochloric acid concentration. The SA-ST_m0.5 obtained by microwave acid treatment at 0.5 mol·L⁻¹ hydrochloric acid concentration showed a higher loading capacity (82.63%) than other composites according to the differential scanning calorimeter (DSC) analysis. The melting and freezing enthalpies of SA-ST_m0.5 were of 152.30 and 148.90 J·g⁻¹, respectively. The thermal conductivity of SA-ST_m0.5 was as high as 1.52 times that of pure SA. In addition, the crystal structure, surface morphology, and microporous structure of ST_m were studied, and the mechanism of SA-ST_m0.5 performance enhancement was further revealed by Brunauere Emmett Teller (BET) analysis. Leakage experiment showed that SA-ST_m0.5 had a good morphological stability. These results demostrate that SA-ST_m0.5 has a potential application in thermal energy storage.

Mold flux serves the crucial metallurgical function of absorbing inclusions, directly impacting the smoothness of the casting process as well as the cast slab quality. In this study, the dissolution behavior and mechanism of TiO₂ and TiN inclusions in molten CaO–SiO_2–B₂O₃-based fluorine-free mold flux were explored by in situ single hot thermocouple technology combined with X-ray photoelectron spectroscopy. The results showed that TiO₂ inclusions are effectively dissolved by the molten slag within 76 s, during which the original octahedral [TiO₆]^8? structures are destroyed and convert to the networker tetrahedral [TiO₄]^4? structures. However, the dissolution rate is much lower for TiN inclusions than for TiO₂ inclusions. This can be attributed to the fact that the TiN particles need to be oxidized and then dissolved in the molten slag to form tetrahedral [TiO₄]^4? and octahedral [TiO₆]^8? structures during the TiN inclusion dissolution process, which is accompanied by the generation of a large amount of N₂ gas. Moreover, CaTiO₃ crystals tend to nucleate and grow on bubble surfaces with sufficient octahedral [TiO₆]^8? structures and Ca²⁺ ions, eventually resulting in the molten slag being in a solid–liquid mixed state.

Owing to the depletion of wolframite, the focus of tungsten extraction has gradually shifted to scheelite. However, separating the associated minerals (e.g., apatite, fluorite, and calcite) and scheelite is challenging because their surface physicochemical properties are similar to those of scheelite. Fortunately, researchers have made substantial progress in separating the minerals of scheelite by using depressants. This study reviews the application and inhibition mechanism of inorganic depressants in obtaining tungsten from its calcium-bearing minerals. The application of new organic depressants in obtaining tungsten from its calcium-bearing minerals and the associated mechanisms are also summarized. After an objective assessment of inorganic and organic depressants’ advantages and disadvantages, possible future research directions for inorganic and organic depressants are proposed. Herein, we provide a theoretical basis for developing scheelite flotation depressants.

Satellited CoNiCrAlY–Al₂O₃ feedstocks with 2wt%, 4wt%, and 6wt% oxide nanoparticles and pure CoNiCrAlY powder were deposited by the high-velocity oxy fuel process on an Inconel738 superalloy substrate. The oxidation test was performed at 1050°C for 5, 50, 100, 150, 200, and 400 h. The microstructure and phase composition of powders and coatings were characterized by scanning electron microscopy and X-ray diffraction, respectively. The bonding strength of the coatings was also evaluated. The results proved that with the increase in the percentage of nanoparticles (from 2wt% to 6wt%), the amount of porosity (from 1vol% to 4.7vol%), unmelted particles, and roughness of the coatings (from 4.8 to 8.8 µm) increased, and the bonding strength decreased from 71 to 48 MPa. The thicknesses of the thermally grown oxide layer of pure and composite coatings (2wt%, 4wt%, and 6wt%) after 400 h oxidation were measured as 6.5, 5.5, 7.6, and 8.1 µm, respectively. The CoNiCrAlY–2wt% Al₂O₃ coating showed the highest oxidation resistance due to the diffusion barrier effect of well-dispersed nanoparticles. The CoNiCrAlY–6wt% Al₂O₃ coating had the lowest oxidation resistance due to its rough surface morphology and porous microstructure.