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

A high thrust-to-weight ratio poses challenges to the high-temperature performance of Ni-based superalloys. The oxidation behavior of GH4738 at extreme temperatures has been investigated by isothermal and non-isothermal experiments. As a result of the competitive diffusion of alloying elements, the oxide scale included an outermost porous oxide layer (OOL), an inner relatively dense oxide layer (IOL), and an internal oxide zone (IOZ), depending on the temperature and time. A high temperature led to the formation of large voids at the IOL/IOZ interface. At 1200°C, the continuity of the Cr-rich oxide layer in the IOL was destroyed, and thus, spallation occurred. Extension of oxidation time contributed to the size of Al-rich oxide particles with the increase in the IOZ. Based on this finding, the oxidation kinetics of GH4738 was discussed, and the corresponding oxidation behavior at 900–1100°C was predicted.

W-based WTaVCr refractory high entropy alloys (RHEA) may be novel and promising candidate materials for plasma facing components in the first wall and diverter in fusion reactors. This alloy has been developed by a powder metallurgy process combining mechanical alloying and spark plasma sintering (SPS). The SPSed samples contained two phases, in which the matrix is RHEA with a body-centered cubic structure, while the oxide phase was most likely Ta₂VO₆ through a combined analysis of X-ray diffraction (XRD), energy-dispersive spectroscopy (EDS), and selected area electron diffraction (SAED). The higher oxygen affinity of Ta and V may explain the preferential formation of their oxide phases based on thermodynamic calculations. Electron backscatter diffraction (EBSD) revealed an average grain size of 6.2 μm. WTaVCr RHEA showed a peak compressive strength of 2997 MPa at room temperature and much higher micro- and nano-hardness than W and other W-based RHEAs in the literature. Their high Rockwell hardness can be retained to at least 1000°C.

The challenge of high temperatures in deep mining remains harmful to the health of workers and their production efficiency. The addition of phase change materials (PCMs) to filling slurry and the use of the cold storage function of these materials to reduce downhole temperatures is an effective approach to alleviate the aforementioned problem. Paraffin–CaCl₂·6H₂O composite PCM was prepared in the laboratory. The composition, phase change latent heat, thermal conductivity, and cemented tailing backfill (CTB) compressive strength of the new material were studied. The heat transfer characteristics and endothermic effect of the PCM were simulated using Fluent software. The results showed the following: (1) The new paraffin–CaCl₂·6H₂O composite PCM improved the thermal conductivity of native paraffin while avoiding the water solubility of CaCl₂·6H₂O. (2) The calculation formula of the thermal conductivity of CaCl₂·6H₂O combined with paraffin was deduced, and the reasons were explained in principle. (3) The “enthalpy-mass scale model” was applied to calculate the phase change latent heat of nonreactive composite PCMs. (4) The addition of the paraffin–CaCl₂·6H₂O composite PCM reduced the CTB strength but increased its heat absorption capacity. This research can give a theoretical foundation for the use of heat storage backfill in green mines.

The impact of alkyl dimethyl betaine (ADB) on the collection capacity of sodium oleate (NaOl) at low temperatures was evaluated using flotation tests at various scales. The low-temperature synergistic mechanism of ADB and NaOl was explored by infrared spectroscopy, X-ray photoelectron spectroscopy, surface tension measurement, foam performance test, and flotation reagent size measurement. The flotation tests revealed that the collector mixed with octadecyl dimethyl betaine (ODB) and NaOl in a mass ratio of 4:96 exhibited the highest collection capacity. The combined collector could increase the scheelite recovery by 3.48% at low temperatures of 8–12°C. This is particularly relevant in the Luanchuan area, which has the largest scheelite concentrate output in China. The results confirmed that ODB enhanced the collection capability of NaOl by improving the dispersion and foaming performance. Betaine can be introduced as an additive to NaOl to improve the recovery of scheelite at low temperatures.

In the long traditional process of steelmaking, excess oxygen is blown into the converter, and alloying elements are used for deoxidation. This inevitably results in excessive deoxidation of products remaining within the steel liquid, affecting the cleanliness of the steel. With the increasing requirements for steel performance, reducing the oxygen content in the steel liquid and ensuring its high cleanliness is necessary. After more than a hundred years of development, the total oxygen content in steel has been reduced from approximately 100 × 10⁻⁶ to approximately 10 × 10⁻⁶, and it can be controlled below 5 × 10⁻⁶ in some steel grades. A relatively stable and mature deoxidation technology has been formed, but further reducing the oxygen content in steel is no longer significant for improving steel quality. Our research team developed a deoxidation technology for bearing steel by optimizing the entire conventional process. The technology combines silicon–manganese predeoxidation, ladle furnace diffusion deoxidation, and vacuum final deoxidation. We successfully conducted industrial experiments and produced interstitial-free steel with natural decarbonization predeoxidation. Non-aluminum deoxidation was found to control the oxygen content in bearing steel to between 4 × 10⁻⁶ and 8 × 10⁻⁶, altering the type of inclusions, eliminating large particle Ds-type inclusions, improving the flowability of the steel liquid, and deriving a higher fatigue life. The natural decarbonization predeoxidation of interstitial-free steel reduced aluminum consumption and production costs and significantly improved the quality of cast billets.

Abstract

The development of anode materials with high rate capability and long charge–discharge plateau is the key to improve performance of lithium-ion capacitors (LICs). Herein, the porous graphitic carbon (PGC-1300) derived from a new triply interpenetrated cobalt metal-organic framework (Co-MOF) was prepared through the facile and robust carbonization at 1300°C and washing by HCl solution. The as-prepared PGC-1300 featured an optimized graphitization degree and porous framework, which not only contributes to high plateau capacity (105.0 mAh·g⁻¹ below 0.2 V at 0.05 A·g⁻¹), but also supplies more convenient pathways for ions and increases the rate capability (128.5 mAh·g⁻¹ at 3.2 A·g⁻¹). According to the kinetics analyses, it can be found that diffusion regulated surface induced capacitive process and Li-ions intercalation process are coexisted for lithium-ion storage. Additionally, LIC PGC-1300//AC constructed with pre-lithiated PGC-1300 anode and activated carbon (AC) cathode exhibited an increased energy density of 102.8 Wh·kg⁻¹, a power density of 6017.1 W·kg⁻¹, together with the excellent cyclic stability (91.6% retention after 10000 cycles at 1.0 A·g⁻¹).

Abstract

Solid-state impedance spectroscopy (SS-IS) was used to investigate the influence of structural modifications resulting from the addition of Nb₂O₅ on the dielectric properties and relaxation processes in the quaternary mixed glass former (MGF) system 35Na₂O-10V₂O₅-(55−x)P₂O₅−xNb₂O₅ (x = 0–40, mol%). The dielectric parameters, including the dielectric strength and dielectric loss, are determined from the frequency and temperature-dependent complex permittivity data, revealing a significant dependence on the Nb₂O₅ content. The transition from a predominantly phosphate glass network (x < 10, region I) to a mixed niobate-phosphate glass network (10 ≤ x ≤ 20, region II) leads to an increase in the dielectric parameters, which correlates with the observed trend in the direct-current (DC) conductivity. In the predominantly niobate network (x ≥ 25, region III), the highly polarizable nature of Nb⁵⁺ ions leads to a further increase in the dielectric permittivity and dielectric strength. This is particularly evident in Nb-40 glass-ceramic, which contains Na₁₃Nb₃₅O₉₄ crystalline phase with a tungsten bronze structure and exhibits the highest dielectric permittivity of 61.81 and the lowest loss factor of 0.032 at 303 K and 10 kHz. The relaxation studies, analyzed through modulus formalism and complex impedance data, show that DC conductivity and relaxation processes are governed by the same mechanism, attributed to ionic conductivity. In contrast to glasses with a single peak in frequency dependence of imaginary part of electrical modulus, M″(ω), Nb-40 glass-ceramic exhibits two distinct contributions with similar relaxation times. The high-frequency peak indicates bulk ionic conductivity, while the additional low-frequency peak is associated with the grain boundary effect, confirmed by the electrical equivalent circuit (EEC) modelling. The scaling characteristics of permittivity and conductivity spectra, along with the electrical modulus, validate time-temperature superposition and demonstrate a strong correlation with composition and modification of the glass structure upon Nb₂O₅ incorporation.

Abstract

The flotation separation of Cu-Fe sulfide minerals at low alkalinity can be achieved using selective depressants. In the flotation system of Cu-Fe sulfide minerals, depressants usually preferentially interact with the pyrite surface to render the mineral surface hydrophilic and hinder the adsorption of the collector. This review summarizes the advances in depressants for the flotation separation of Cu-Fe sulfide minerals at low alkalinity. These advances include use of inorganic depressants (oxidants and sulfur-oxygen compounds), natural polysaccharides (starch, dextrin, konjac glucomannan, and galactomannan), modified polymers (carboxymethyl cellulose, polyacrylamide, lignosulfonate, and tricarboxylate sodium starch), organic acids (polyglutamic acid, sodium humate, tannic acid, pyrogallic acid, salicylic acid, and lactic acid), sodium dimethyl dithiocarbamate, and diethylenetriamine. The potential application of specific inorganic and organic depressants in the flotation separation of Cu-Fe sulfide minerals at low alkalinity is reviewed. The advances in the use of organic depressants with respect to the flotation separation of Cu-Fe sulfide minerals are comprehensively detailed. Additionally, the depression performances and mechanisms of different types of organic depressants on mineral surfaces are summarized. Finally, several perspectives on depressants vis-à-vis flotation separation of Cu-Fe sulfide minerals at low alkalinity are proposed.

Abstract

Zinc-ion batteries (ZIBs) are recognized as potential energy storage devices due to their advantages of low cost, high energy density, and environmental friendliness. However, zinc anodes are subject to unavoidable zinc dendrites, passivation, corrosion, and hydrogen evolution reactions during the charging and discharging of batteries, becoming obstacles to the practical application of ZIBs. Appropriate zinc metal-free anodes provide a higher working potential than metallic zinc anodes, effectively solving the problems of zinc dendrites, hydrogen evolution, and side reactions during the operation of metallic zinc anodes. The improvement in the safety and cycle life of batteries creates conditions for further commercialization of ZIBs. Therefore, this work systematically introduces the research progress of zinc metal-free anodes in “rocking chair” ZIBs. Zinc metal-free anodes are mainly discussed in four categories: transition metal oxides, transition metal sulfides, MXene (two dimensional transition metal carbide) composites, and organic compounds, with discussions on their properties and zinc storage mechanisms. Finally, the outlook for the development of zinc metal-free anodes is proposed. This paper is expected to provide a reference for the further promotion of commercial rechargeable ZIBs.

Abstract

Scholars aim for the improved impedance matching (Z) of materials while maintaining their excellent wave absorption properties. Based on the hydrolysis characteristics of isopropyl titanate, a simple preparation process for the coating of carbonyl iron powder (CIP) with TiO₂ was designed. Given the TiO₂ coating, the Z of the CIP@TiO₂ composite was adjusted well by decreasing the dielectric constant. Moreover, the interfacial polarization of CIP@TiO₂ was enhanced. Ultimately, the electromagnetic-wave (EMW) absorption property of the CIP@TiO₂ composite was improved substantially, the minimum reflection loss reached −46.07 dB, and the effective absorption bandwidth can reach 8 GHz at the composite thickness of 1.5 mm. Moreover, compared with CIP, the oxidation resistance of CIP@TiO₂ showed remarkable improvement. The results revealed that the oxidation starting temperature of CIP@TiO₂ was about 400°C, whereas the uncoated CIP had an oxidation starting temperature of approximately 250°C. Moreover, the largest oxidation rate temperature of CIP@TiO₂ increased to around 550°C. This work opens up a novel strategy for the production of high-performance EMW absorbers via structural design.