During the past thirty years, two generations of low alloy steels (ferrite/pearlite followed by bainite/martensite) have been developed and widely used in structural applications. The third-generation of low alloy steels is expected to achieve high strength and improved ductility and toughness, while satisfying the new demands for weight reduction, greenness, and safety. This paper reviews recent progress in the development of third-generation low alloy steels with an M³ microstructure, namely, microstructures with multi-phase, meta-stable austenite, and multi-scale precipitates. The review summarizes the alloy designs and processing routes of microstructure control, and the mechanical properties of the alloys. The stabilization of retained austenite in low alloy steels is especially emphasized. Multi-scale nano-precipitates, including carbides of microalloying elements and Cu-rich precipitates obtained in third-generation low alloy steels, are then introduced. The structure–property relationships of third-generation alloys are also discussed. Finally, the promises and challenges to future applications are explored.

Along with slurry concentration and particle density, particle size distribution (PSD) of tailings also exerts a significant influence on the yield stress of cemented paste, a non-Newtonian fluid. In this work, a paste stability coefficient (PSC) was proposed to characterize paste gradation and better reveal its connection to yield stress. This coefficient was proved beneficial to the construction of a unified rheological model, applicable to different materials in different mines, so as to promote the application of rheology in the pipeline transportation of paste. From the results, yield stress showed an exponential growth with increasing PSC, which reflected the proportion of solid particle concentration to the packing density of granular media in a unit volume of slurry, and could represent the properties of both slurry and granular media. It was found that slurry of low PSC contained extensive pores, generally around 20 μm, encouraging free flow of water, constituting a relatively low yield stress. In contrast, slurry of high PSC had a compact and quite stable honeycomb structure, with pore sizes generally < 5 μm, causing the paste to overcome a higher yield stress to flow.

Resistance in iron ore undergoes a sharp change of up to several orders of magnitude when the sintered solid phase changes to liquid phase. In view of the insufficiency of existing assimilation detection methods, a timing-of-assimilation reaction is proposed, which was judged by continuously detecting the changes in resistance at the reaction interface. Effects of pole position and additional amounts of iron ore on assimilation reaction timing were investigated. The results showed that the suitable depth of pole groove was about 2 mm, and there was no obvious impact when the distance of the poles changed from 4 to 6 mm, or the amount of iron ore changed from 0.4 to 0.6 g. The temperature of sudden change of resistance in the temperature-resistant image was considered to be the lowest assimilation temperature of iron ore. The accuracy of this resistance method was clarified by X-ray diffraction, optical microscope, and scanning electron microscope/energy dispersive spectrometer (SEM/EDS) analyses.

A novel method for recovering zinc from zinc ferrite by reduction roasting–ammonia leaching was studied in this paper. The reduction thermodynamic of zinc ferrite by CO was analyzed. The effects of roasting parameters on the phase transformation and conversion rate of zinc ferrite, and the leaching behavior of zinc from the reductive roasted samples by ammonia leaching, were experimentally investigated. The mineralogical phase compositions and chemical compositions of the samples were characterized by X-ray diffraction and chemical titration methods, respectively. The results showed that most of the zinc ferrite was transformed to zinc oxide and magnetite after weak reduction roasting. 86.43% of the zinc ferrite was transformed to zinc oxide under the optimum conditions: CO partial pressure of 25%, roasting temperature of 750°C, and roasting duration of 45 min. Finally, under the optimal leaching conditions, 78.12% of zinc was leached into the solution from the roasted zinc ferrite while all iron-bearing materials were kept in the leaching residue. The leaching conditions are listed as follows: leaching duration of 90 min, ammonia solution with 6 mol/L concentration, leaching temperature of 50°C, solid-to-liquid ratio of 40 g/L, and stirring speed of 200 r/min.

The method of calciothermic reduction of B₄C was proposed for preparing CaB₆. The phase transition and morphology evolution during the reaction were investigated in detail. The experimental results reveal that Ca first reacts with B₄C to generate CaB₂C₂ and CaB₆ at a low temperature and that the CaB₂C₂ subsequently reacts with Ca to produce CaB₆ and CaC₂ at a high temperature. After the products were leached to remove the byproduct CaC₂, pure CaB₆ was obtained. The grain size of the prepared CaB₆ was 2–3 μm, whereas its particle size was 4–13 μm; it inherited the particle size of B4C. The residual C content of the product was decreased to 1.03wt% after the first reaction at 1173 K for 4 h and the second reaction at 1623 K for 4 h.

In this work, different magnesium silicate mineral samples based on antigorite, lizardite, chrysotile (which have the same general formula Mg₃Si₂O₅(OH)₄), and talc (Mg₃Si₄O₁₀(OH)₂) were reacted with KOH to prepare catalysts for biodiesel production. Simple impregnation with 20wt% K and treatment at 700–900°C led to a solid-state reaction to mainly form the K₂MgSiO₄ phase in all samples. These results indicate that the K ion can diffuse into the different Mg silicate structures and textures, likely through intercalation in the interlayer space of the different mineral samples followed by dehydroxylation and K₂MgSiO₄ formation. All the materials showed catalytic activity for the transesterification of soybean oil (1:6 of oil : methanol molar ratio, 5wt% of catalyst, 60°C). However, the best results were obtained for the antigorite and chrysotile precursors, which are discussed in terms of mineral structure and the more efficient formation of the active phase K₂MgSiO₄.

Hydro-sodalites are zeolitic materials with a wide variety of applications. Fly ash is an abundant industrial solid waste, rich in silicon and aluminum, from which hydro-sodalite can be synthesized. However, traditional hydrothermal synthesis methods are complex and cannot produce high-purity products. Therefore, there is a demand for processing routes to obtain high-purity hydro-sodalites. In the present study, high-purity hydro-sodalite (90.2wt%) was prepared from fly ash by applying a hydrothermal method to a submolten salt system. Samples were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetry and differential thermal analysis (TG–DTA), and Fourier transform infrared spectroscopy (FTIR) to confirm and quantify conversion of the raw material into the product phase. Purity of the samples prepared with an H₂O/NaOH mass ratio of 1.5 and an H₂O/fly ash mass ratio of 10 was calculated and the conversion process of the product phase was studied. Crystallinity of the product was influenced more by the NaOH concentration, less by the H₂O/fly ash mass ratio. The main reaction process of the system is that the SiO

ions produced by dissolution of the vitreous body in the fly ash and Na⁺ ions in the solution reacted on the destroyed mullite skeleton to produce hydro-sodalite. This processing route could help mitigate processing difficulties, while producing high-purity hydro-sodalite from fly ash.

This study investigated the susceptibility of X80 pipeline steel to hydrogen embrittlement given different hydrogen pre-charging times and hydrogen charging–releasing–recharging cycles in H₂S environment. The fracture strain of the steel samples decreased with increasing hydrogen pre-charging time; this steel degradation could almost be recovered after diffusible hydrogen was removed when the hydrogen pre-charging time was<8 d. However, unrecoverable degeneration occurred when the hydrogen pre-charging time extended to 16–30 d. Moreover, nanovoid formation meant that the hydrogen damage to the steel under intermittent hydrogen pre-charging–releasing–recharging conditions was more serious than that under continuous hydrogen pre-charging conditions. This study illustrated that the mechanical degradation of steel is inevitable in an H₂S environment even if diffusible hydrogen is removed or visible hydrogen-induced cracking is neglected. Furthermore, the steel samples showed premature fractures and exhibited a hydrogen fatigue effect because the repeated entry and release of diffusible hydrogen promoted the formation of vacancies that aggregated into nanovoids. Our results provide valuable information on the mechanical degradation of steel in an H₂S environment, regarding the change rules of steel mechanical properties under different hydrogen pre-charging times and hydrogen charging–releasing–recharging cycles.

Nine distinct zinc−nickel−tin films with different compositions have been galvanostatically electrodeposited. The films have been characterized by scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). Their corrosion potentials and densities have been estimated using Tafel extrapolation. Next, the electrochemical behaviors of the films (deposited through the electrolytes containing 0, 6, 8, and 10 g/L SnCl₂∙6H₂O) have been examined based on cyclic voltammetry (CV) measurements. Further, these films have been immersed in 3.5wt% NaCl solution for 1 h, 1 d, 7 d, 14 d, 28 d, and 42 d followed by application of Tafel extrapolation and electrochemical impedance spectroscopy (EIS) tests on each aged sample. Finally, to analyze the morphologies and the compositions of the oxide films covering the surfaces of the 42-d aged films, FT-IR and SEM analyses have been performed. The results indicated that the Zn–Ni–Sn film produced through the bath including 6 g/L SnCl₂∙6H₂O exhibits superior corrosion resistance because of the high Ni content in the presence of Sn that promotes the barrier protection capability of the deposit.

The effect of single overload on the fatigue crack growth in 2024-T3 and 7075-T6 Al alloys was analyzed. Fatigue tests under constant-amplitude loading with overload peak were carried out on V-notched specimens. Fractographic analysis was used as a principal approach to explain the crack growth retardation due to the overload. Scanning electron microscopy (SEM) analyses were conducted on the fractured surface of failed specimens to study the retardation effect. The obtained results show that the overload application generates a plastic zone in both aluminum alloys. The generated plastic zone is three times larger in the case of 2024-T3 compared to 7075-T6, and thus, a significant crack retardation was induced for 2024-T3. The retardation effect due to the overload for 2024-T3 and 7075-T6 lasted for about 10 mm and 1 mm, respectively, from the point of overload application.

Highly sensitive methods are important for monitoring the concentration of metal ions in industrial wastewater. Here, we developed a new probe for the determination of metal ions by fluorescence quenching. The probe consists of hydroxylated graphene quantum dots (H-GQDs), prepared from GQDs by electrochemical method followed by surface hydroxylation. It is a non-reactive indicator with high sensitivity and detection limits of 0.01 μM for Cu²⁺, 0.005 μM for Al³⁺, 0.04 μM for Fe³⁺, and 0.02 μM for Cr³⁺. In addition, the low biotoxicity and excellent solubility of H-GQDs make them promising for application in wastewater metal ion detection.

The wear resistance of iron (Fe)-matrix materials could be improved through the in situ formation of vanadium carbide particles (VCp) with high hardness. However, brittleness and low impact toughness limit their application in several industries due to addition of higher carbon content. Carbon-partitioning treatment plays an important role in tuning the microstructure and mechanical properties of in situ VCp-reinforced Fe-matrix composite. In this study, the influences of carbon-partitioning temperatures and times on the microstructure, mechanical properties, and wear resistance of in situ VCp-reinforced Fe-matrix composite were investigated. The experimental results indicated that a certain amount of retained austenite could be stabilized at room temperature through the carbon-partitioning treatment. Microhardness of in situ VCp-reinforced Fe-matrix composite under carbon-partitioning treatment could be decreased, but impact toughness was improved accordingly when wear resistance was enhanced. In addition, the enhancement of wear resistance could be attributed to transformation-induced plasticity (TRIP) effect, and phase transformation was caused from γ-Fe (face-centered cubic structure, fcc) to α-Fe (body-centered cubic structure, bcc) under a certain load.

Thermochemical heat storage (THS) systems have recently attracted a lot of attention in research and development. In this study, an anodic aluminum oxide (AAO) template, fabricated by a two-step anodization method, was used for the first time as the matrix material for a THS system. Different salts were studied as thermochemical materials for their suitability in low-grade heat storage application driven by solar energy for an open system. Compositions were prepared by absorbing CaCl₂, MgCl₂, LiCl, LiNO₃ and mixtures of these salts under a vacuum in an AAO matrix. Field Emission Scanning Electron Microscopy was used to examine the morphology of the produced AAO composites. Thermal energy storage capacities of the composites were characterized using a differential scanning calorimeter. Characterization analysis showed that anodized Al plates were suitable matrix materials for THS systems, and composite sorbent prepared with a 1:1 ratio LiCl/LiNO₃ salt mixture had the highest energy value among all composites, with an energy density of 468.1 kJ·kg⁻¹.