Column leaching experiments with ion adsorption-type rare earth ores for different lixiviant concentrations and different column heights were carried out. A mathematical model of column leaching was constructed based on the experimental data. Two parameters (a and b) in the model were determined according to the following methodology: the ore column was divided into several units; each unit was treated with multiple leaching steps. The leaching process was simulated as a series of batch leaching experiments. Parameter a of the model was determined based on the selectivity coefficient of the balanced batch leaching experiment. Further, the influences of ammonium sulfate concentration, rare earth grade, column height, permeability coefficient, and hydrodynamic dispersion coefficient on the extraction were analyzed. Relationships between parameter b, the ammonium sulfate concentration, and the physical and mechanical properties of the ore column, were examined using dimensional analysis. It was determined that the optimal ammonium sulfate concentration for different column heights (2.5, 5.0, 7.5, and 10.0 cm) using the mathematical model were 5.9, 6.2, 7.3, and 7.7 g/L, respectively. The mathematical model can be used to estimate the breakthrough curve, leaching rate, and leaching period of rare earth ores, to achieve optimal extraction.

Abstract To improve the electrochemical kinetics of Nd–Mg–Ni alloy electrodes, the alloy surface was modified with highly conductive reduced graphene oxide (rGO) via a chemical reduction process. Results indicated that rGO sheets uniformly coated on the alloy surface, yielding a threedimensional network layer. The coated surfaces contained numerous hydrophilic functional groups, leading to better wettability of the alloy in aqueous alkaline media. This, in turn, increased the concentration of electro-active species at the interface between the electrode and the electrolyte, improving the electrochemical kinetics and the rate discharge of the electrodes. The high rate dischargeability at 1500 mA·g−1 increased from 53.2% to 83.9% after modification. In addition, the modification layer remained stable and introduced a dense metal oxide layer to the alloy surface after a long cycling process. Therefore, the protective layer prevented the discharge capacity from quickly decreasing and improved cycling stability.

Effects of calcium compounds on the carbothermic reduction of vanadium titanomagnetite concentrate (VTC) were investigated. It was found that calcium compounds had great effects on the metallization rate of the reduction product, the order of the metallization rate of reduction product being CaCO3 > no additive > CaSO4 > CaCl2, which indicated that the addition of CaCO3 was more conducive to promoting the reduction of iron than other calcium compounds. Gas analysis showed that there were mainly two processes in the carbothermic reduction of VTC, a solid-solid and a solid-gas reaction. The concentrations of CO and C02 were highest when CaC03 was added, while that in a roasting system decreased the most when CaCl2 was added. X-ray diffraction (XRD) analysis showed that calcium compounds could change the reduction process of ilmenite in VTC. The phase compositions of the reduction products were changed from metallic iron (Fe) and anosovite (FeTi205) to metallic iron (Fe) and perovekite (CaTi03) when calcium compounds were added. Additionally, CaSO4 and CaCl2 could significantly promote the growth of metallic iron particles, though the existence of Fe-bearing Mg2TiO4 in reduction products was not conducive to the reduction of iron. The formation of FeS would further hinder the reduction of iron after adding CaSO4.

The acknowledgements of this article unfortunately contained a mistake. The grant number of the National Natural Science Foundation of China was incorrect.

The original version of this article unfortunately contained a mistake.

Abstract 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.

Abstract 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.

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.

Abstract 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.

Abstract 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 microal-loying 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.

UNS S32205 duplex stainless steel plates were welded to AISI 316L stainless steel using the pulsed gas tungsten arc welding process with three different filler metals: ER2594, ER312, and ER385. The microstructures of the welds were characterized using optical and scanning electron microscopy, and all of the specimens were evaluated by ferrite measurements. The mechanical properties were studied through hardness, tensile, and impact tests. In addition, the pitting resistance equivalent number was calculated and cyclic polarization tests were performed to evaluate the corrosion resistance of the weld metal. The results showed that chromium nitride was formed in the heat-affected zone of the duplex side, whereas no sigma phase was detected in any of the specimens. The ferrite number increased from the root pass to the final pass. The absorbed energies of the impact test decreased with increasing ferrite number, whereas the tensile strength was enhanced. The fully austenitic microstructure of the specimen welded with ER385 exhibited the highest resistance to pitting corrosion at 25°C, and the super-duplex weld metal presented superior corrosion resistance at 50°C.

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.

Abstract 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 Fematrix 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.

Abstract 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.

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 (FUR) 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 \({\rm{SiO}}_3^{2-}\) 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.

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 K2MgSi04 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 K2MgSi04 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 K2MgSi04.

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.

Abstract 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.

Abstract 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.

In this study, we prepared Ti/IrO2-ZrO2 electrodes with different ZrO2 contents using zirconium-n-butoxide (C16H36O4Zr) and chloroiridic acid (H2IrCl6) via a sol-gel route. To explore the effect of ZrO2 content on the surface properties and electrochemical behavior of electrodes, we performed physical characterizations and electrochemical measurements. The obtained results revealed that the binary oxide coating was composed of rutile IrO2, amorphous ZrO2, and an IrO2-ZrO2 solid solution. The IrO2-ZrO2 binary oxide coatings exhibited cracked structures with flat regions. A slight incorporation of ZrO2 promoted the crystallization of the active component IrO2. However, the crystallization of IrO2 was hindered when the added ZrO2 content was greater than 30at%. The appropriate incorporation of ZrO2 enhanced the electrocatalytic performance of the pure IrO2 coating. The Ti/70at%IrO2-30at%ZrO2 electrode, with its large active surface area, improved electrocatalytic activity, long service lifetime, and especially, lower cost, is the most effective for promoting oxygen evolution in sulfuric acid solution.

Abstract A study on the melting and viscosity properties of the chromium-containing high-titanium melting slag (CaO-SiO2-MgO-Al2O3-TiO2-Cr2O3) with TiO2 contents ranging from 38.63wt% to 42.63wt% was conducted. The melting properties were investigated with a melting-point apparatus, and viscosity was measured using the rotating cylinder method. The FactSage 7.1 software and X-ray diffraction, in combination with scanning electron microscopy-energy-dispersive spectroscopy (SEM-EDS), were used to characterize the phase equilibrium and micro-structure of chromium-containing high-titanium melting slags. The results indicated that an increase in the TiO2 content led to a decrease in the viscosity of the chromium-containing high-titanium melting slag. In addition, the softening temperature, hemispheric temperature, and flowing temperature decreased with increasing TiO2 content. The amount of crystallized anosovite and sphene phases gradually increased with increasing TiO2 content, whereas the amount of perovskite phase decreased. SEM observations revealed that the distribution of the anosovite phase was dominantly influenced by TiO2.

The co-oxidation of As(III) and Fe(II) in acidic solutions by pressured oxygen was studied under an oxygen pressure between 0.5 and 2.0 MPa at a temperature of 150°C. It was confirmed that without Fe(II) ions, As(III) ions in the solutions are virtually non-oxidizable by pressured oxygen even at a temperature as high as 200°C and an oxygen pressure up to 2.0 MPa. Fe(II) ions in the solutions did have a catalysis effect on the oxidation of As(III), possibly attributable to the production of such strong oxidants as hydroxyl free radicals (OH·) and Fe(IV) in the oxidation process of Fe(II). The effects of such factors as the initial molar ratio of Fe(II)/As(III), initial pH value of the solution, oxygen pressure, and the addition of radical scavengers on the oxidation efficiencies of As(III) and Fe(II) were studied. It was found that the oxidation of As(III) was limited in the co-oxidation process due to the accumulation of the As(III) oxidation product, As(V), in the solutions.

An efficient approach for lead extraction from waste funnel glass through the lead smelting process has been proposed. To clarify the effect of funnel glass addition on the degradation of magnesia-chromite refractories by ZnO-containing fayalite slag, the corrosion behavior of magnesia-chromite refractories in lead smelting slags with different funnel glass additions from 0wt% to 40wt% was tested. Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS) was used to acquire the microstructural information of the worn refractory samples. Experimental results showed that the corrosion of magnesia-chromite refractory consisted predominantly of the dissolution of MgO into slag. ZnO and FeO reacted with periclase and chromite to form (Zn,Fe,Mg)O solid solution and (Zn,Fe,Mg)(Fe,Al,Cr)2O4 spinel, respectively. With the addition of funnel glass, the solubility of MgO increased whereas ZnO levels remained stable, thereby resulting in a reduced Mg content and an elevated Zn and Fe content in the (Zn,Fe,Mg)O solid solution and the (Zn,Fe,Mg)(Fe,Al,Cr)2O4 spinel. Considering the stability of the (Zn,Fe,Mg)O solid solution layer and the penetration depth of the slag, the optimal funnel glass addition for lead smelting was found to be 20wt%.

Mineral processing plants generally have narrow tolerances for the grades of their input raw materials, so stockpiles are often maintained to reduce material variance and ensure consistency. However, designing stockpiles has often proven difficult when the input material consists of multiple sub-materials that have different levels of variances in their grades. In this paper, we address this issue by applying principal component analysis (PCA) to reduce the dimensions of the input data. The study was conducted in three steps. First, we applied PCA to the input data to transform them into a lower-dimension space while retaining 80% of the original variance. Next, we simulated a stockpile operation with various geometric stockpile configurations using a stockpile simulator in MATLAB. We used the variance reduction ratio as the primary criterion for evaluating the efficiency of the stockpiles. Finally, we used multiple regression to identify the relationships between stockpile efficiency and various design parameters and analyzed the regression results based on the original input variables and principal components. The results showed that PCA is indeed useful in solving a stockpile design problem that involves multiple correlated input-material grades.

This paper describes the investigation of the secretion of extracellular polymeric substances (EPS) by an extremely thermoacidophilic archaea, Metallosphaera sedula (M. sedula), during the bioleaching of pyrite under different temperatures and discusses the relationship among the EPS secretion, its heat resistance, and its ability to bioleach pyrite. The investigation results indicate that the amount of extracellular proteins is significantly higher than the amount of extracellular polysaccharides in the extracted EPS whether free cells or attached cells; these results are quite different from the behavior of mesophilic Acidithiobacillus ferrooxidans. Although the growth of M. sedula is inhibited at 80°C, the bioleaching ability of M. sedula is only slightly lower than that at the optimum growth temperature of 72°C because of the heat resistance mechanism based on EPS secretion. The secretion of more extracellular proteins is an important heat resistance mechanism of M. sedula.

Hardfacing coatings involve hard carbide/boride phases dispersed in a relatively soft steel matrix. For the hardness measurements of hardfacing coatings, depending on the micro structure, both the hardness test method and the applied load affect the hardness results; therefore, they affect the wear performance predictions of the coating. For this reason, the proper hardness test method should be determined according to the microstructure of the coating, and the reliability of the obtained hardness data should be established. This study aimed to determine the most suitable hardness test method for hypoeutectic and hypereutectic microstructures of hardfacing coatings by analyzing the reliability of Rockwell-C and Vickers hardness test results. Reliability analyses showed that Rockwell-C is not a suitable hardness test method for hypereutectic hardfacing coatings. Based on the relationship between wear resistance and hardness, Vickers hardness method was found more suitable for the considered materials.

The effects of Sc and Zr microalloying on the microstructure and mechanical properties of a 7xxx Al alloy with high Cu content (7055) during casting, deformation, and heat treatment were investigated. The addition of Sc and Zr not only refined the grains but also transformed the θ-phase into the W-phase in the 7055 alloy. Minor Sc and Zr additions enhanced the hardness and yield strength of the 7055-T6 alloy by strengthening the grain boundaries and Al3(Sc,Zr) precipitates. However, a further increase in the Sc and Zr fractions did not refine the grains but instead resulted in the formation of the large-sized W-phase and primary coarse Al3(Sc,Zr) phase and subsequently deteriorated the mechanical properties of the alloys. The 7055 alloy with 0.25Sc addition exhibited the best mechanical property among the prepared alloys.

The main problems with the liquid-phase technology of carbon fiber/aluminum matrix composites include poor wetting of the fiber with liquid aluminum and formation of aluminum carbide on the fibers’ surface. This paper aims to solve these problems. The theoretical and experimental dependence of porosity on the applied pressure were determined. The possibility of obtaining a carbon fiber/aluminum matrix composite wire with a strength value of about 1500 MPa was shown. The correlation among the strength of the carbon fiber reinforced aluminum matrix composite, the fracture surface, and the degradation of the carbon fiber surface was discussed.

Based on stress- and strain-controlled cyclic tension-unloading-heat-cooling tests, cyclic degradation of the one-way shape memory effect (OWSME) of NiTi shape memory alloys (SMAs) was investigated. It was seen, in thermo-mechanical coupled cyclic tests, that residual strain after each cycle accumulated, but the martensite reorientation stress and dissipation energy-per-cycle decreased as the number of cycles increased. Meanwhile, the cyclic degradation of OWSME was aggravated by increasing the stress/strain amplitude. In addition, the stress-strain response of NiTi SMAs was further investigated by performing simultaneous thermo-mechanical coupled cyclic tests with various phase-angle differences between the mechanical and thermal cyclic loadings. It can be concluded that such cyclic response depends significantly on prescribed phase-angle differences. Obtained experimental results are helpful for both the development of constitutive models and engineering applications of NiTi SMAs.

The effect of Cr content and cooling rate on the microstructure of Al-Mn alloy was studied using well resistance furnace melting, and the alloy was analyzed using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The experimental results showed that adding Cr could significantly improve the morphology of the primary phase in the Al-2.5Mn alloy. Without Cr, the primary phase in the alloy was thick, needle-like, and strip-like structure. After adding 0.2wt%-0.5wt% Cr, the primary phase in the upper part of the alloy was gradually fined and reached the best effect at 0.35wt% Cr. When the content of Cr was 0.5wt%, the microstructure of the primary phase in the upper part began to coarsen. The bottom of the alloy was a large bulk phase, but still much finer than that without adding Cr. XRD and SEM analysis showed that the precipitation phase at the bottom was mainly Al85Mn7Cr8, while the fine microstructure at the top was Al6Mn and Al3Mn. The results of the cooling rate experiments showed that the primary phase of Al-2.5Mn-0.35Cr was further refined, and the eu-tectic microstructure was partly achieved, under air-cooling condition. And when the cooling method was iron die-cooling, the microstructure of the Al-2.5Mn-0.35Cr alloy was changed into a eutectic microstructure.

The use of seaweed glue (SEG) as a novel polymer depressant for the separation of chalcopyrite from galena with butyl xanthate (BX) as a collector was studied through microflotation experiments. Contact angle, adsorption, dynamic potential, and infrared spectral analyses were conducted to clarify the mechanism underlying the action of SEG on minerals. The results of microflotation experiments indicated that chalcopyrite could be selectively separated from galena by using a SEG depressant concentration of 15 mg·L−1, BX concentration of 10 mg·L−1, and methyl isobutyl carbinol concentration of 8.5 mg·L−1 at pH 8.0. A Cu concentrate with a grading of 23.68wt% was obtained at a recovery rate of 81.52% from mixed minerals with 8.29wt% Cu content. Contact angle analysis showed that the effect of SEG on the wettability of galena was stronger than that on the wettability of chalcopyrite. Adsorption, zeta potential, and FT-IR spectral analyses revealed that SEG and BX were coadsorbed on the surfaces of galena. SEG depressed galena by covering xanthate ions in the functional groups of -COO and mainly underwent weak physisorption on chalcopyrite. These mechanisms account for the ability of SEG to depress galena effectively while enabling chalcopyrite flotation.

The production of low-temperature reheated grain-oriented silicon steel is mainly based on the acquired inhibitor method. Due to the additional nitriding process, a high nitrogen content exists in the oxide layer, which changes the structure of the oxide layer. In this study, the structure of the surface oxide layer after nitriding was analyzed by scanning electron microscopy (SEM), electron back-scattered diffraction (EBSD), glow discharge spectrometry (GDS), and X-ray diffraction (XRD). The size and orientation of ferritic grains in the oxide layer were characterized, and the distribution characteristics of the key elements along the thickness direction were determined. The results show that the oxide layer of the steel sample mainly comprised particles of Fe2SiO4 and spherical and lamellar SiO2, and Fe4N and fcc-Fe phases were also detected. Moreover, the size and orientation of ferritic grains in the oxide layer were different from those of coarse matrix ferritic grains beneath the oxide layer; however, some ferritic grains exhibited same orientations as those in the neighboring matrix. Higher nitrogen content was detected in the oxide layer than that in the matrix beneath the oxide layer. The form of nitrogen enrichment in the oxide layer was analyzed, and the growth mechanism of ferritic grains during the oxide layer formation is proposed.

Zinc borate (ZB) particles dispersed in silicone oil (SO) at concentrations of ϕ = 5vol%-20vol% were subjected to dielectric analysis to elucidate their polarization strength, time, and mechanism. Results revealed that all virgin dispersions lacked polarization. Triton X-100, a non-ionic surfactant, was added to ZB/SO dispersions to enhance the polarizability of ZB particles. The addition of 1vol% Triton X-100 enhanced the polarizability of ZB/SO dispersions, and the 15vol%ZB/SO system provided the highest dielectric difference Δε′ (the difference in ε′ values at zero and infinite frequency, Δε′ = ε0 - ε221D) of 3.64. The electrorheological (ER) activities of the ZB/SO/Triton-X dispersion system were determined through the ER response test, and viscoelastic behaviors were investigated via oscillation tests. A recoverable deformation of 36% under an applied electrical field strength of 1.5 kV/mm was detected through creep and creep recovery tests.

Germanium (Ge), a waste residue leaching from zinc (Zn) smelting process, has potential cementitious properties and could be recycled as a cement supplement activated by chemical reagents. In this work, a test was conducted to determine the hydration properties of Ge slag-cement-based composites with Ge slag (GS)/ordinary Portland cement (PC) contents of 0wt%, 5wt%, 10wt%, 15wt%, 20wt%, and 25wt% and water-to-binder ratio (w/b) of 0.4. The activators Ca(OH)2, AlCl3, NaAlO2, and Na2CO3 were mixed under 1wt%, 2wt%, 3wt%, and 4wt% dosages of GS weight. The composition and microstructure of the hydration products were investigated by the combined approaches of X-ray diffraction (XRD), thermogravimetry–differential scanning calorimetry (TG-DSC), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). First, the GS cementitious property is attributed to the high content of CaSO4•2H2O. Second, the activators affected the acceleration performance in the following order: NaAlO2, Na2CO3, AlCl3, and Ca(OH)2. More importantly, the 28-day unconfined compressive strength (UCS) is 45.34 MPa at the optimum formula of 0.6wt% NaAlO2, 15wt% GS, and 85wt% PC, which is 9.16% higher than the control. Thus, NaAlO2 is beneficial for the ettringite (AFt) generation, resulting in the C–S–H structure compaction. However, the Zn2+ residue inhibited the AFt formation, representing an important challenge to the strength growth with curing age. Consequently, the GS could be recycled as a supplement to the cement under the activator NaAlO2.

A MgAl-layered double hydroxide (MgAl-LDH) protective film was developed on AA6082 substrates via the in situ hydrothermal growth method to obtain a distinct cauliflower-like LDH structure, and coated substrates were further heat-treated in air at temperatures from 100 to 250°C to further improve the corrosion resistance of MgAl-LDH by taking advantage of the LDH memory effect; also, the effect of calcination on MgAl-LDH structural stability and the corresponding corrosion resistance properties were investigated. The structural characterization of uncalcined and calcined LDH films were examined using scanning electron microscopy, energy-dispersive spectroscopy, X-ray diffraction, thermogravimetric analysis, differential scanning calorimetry, and Fourier transform infrared spectroscopy. The corresponding corrosion protection efficiency of the developed coating was studied through potentiodynamic polarization experiments and by electrochemical impedance spectroscopy. Compared with uncalcined MgAl-LDH, the calcined film showed a relatively lower corrosion current density and a higher impedance value, especially after heat treatment at 250°C. The findings demonstrate that calcination strongly affects the oriented growth of the LDH and causes an increase in the surface area and contraction of the basal spacing, which in turn caused a compact structure that substantially influenced the LDH corrosion resistance properties.

The high-value utilization of low-rank coal would allow for expanding energy sources, improving energy efficiencies, and alleviating environmental issues. In order to use low-rank coal effectively, the hypercoals (HPCs) were co-extracted from two types of low-rank coal and biomass via N-methyl-2-purrolidinone (NMP) under mild conditions. The structures of the HPCs and residues were characterized by proximate and ultimate analysis, Raman spectra, and Fourier transform infrared (FT-IR) spectra. The carbon structure changes within the raw coals and HPCs were discussed. The individual thermal dissolution of Xibu (XB) coal, Guandi (GD) coal, and the biomass demonstrated that the biomass provided the lowest thermal dissolution yield Y1 and the highest thermal soluble yield Y2 at 280°C, and the ash content of three HPCs decreased as the extraction temperature rose. Co-thermal extractions in NMP at various coal/biomass mass ratios were performed, demonstrating a positive synergic effect for Y2 in the whole coal/biomass mass ratios. The maximum value of Y2 was 52.25wt% for XB coal obtained with a XB coal/biomass of 50wt% biomass. The maximum value of Y2 was 50.77wt% for GD coal obtained with a GD coal/biomass of 1:4. The difference for the optimal coal/biomass mass ratios between XB and GD coals could be attributed to the different co-extraction mechanisms for this two type coals.

For a long time, coalbed gas has brought about various problems to the safety of coal mine production. In addition, the mining of gas and coalbed methane (CBM) has attracted much attention. The occurrence and migration of CBM are believed to be closely related to the micro-surface properties of coal. To further explore the characteristics of CBM occurrence and migration, in this study, the micro-surface topography, adhesion, and elastic modulus of five metamorphic coals were measured by atomic force microscopy (AFM). The results show that the microtopography of coal fluctuates around 40 nm, reaching a maximum of 66.5 nm and the roughness of the surface decreases with the increase of metamorphism. The elastic modulus of coal micro-surface varies from 95.40 to 9626.41 MPa, while the adhesion varies from 15.08 to 436.22 nN, and they both exhibit a trend of “M” shape with the increase of metamorphism. Furthermore, a high correlation exists between adhesion and microtopography fluctuation. In most cases, the adhesion is larger in the concavity area and smaller in the convexity area. The research results may provide a new method for revealing the occurrence and migration of CBM and ensure efficient and safe CBM exploitation.

The cathodic reaction mechanisms in CO2 corrosion of low-Cr steels were investigated by potentiodynamic polarization and galvanostatic measurements. Distinct but different dominant cathodic reactions were observed at different pH levels. At the higher pH level (pH > ~5), H2CO3 reduction was the dominant cathodic reaction. The reaction was under activation control. At the lower pH level (pH < ~3.5), H+ reduction became the dominant one and the reaction was under diffusion control. In the intermediate area, there was a transition region leading from one cathodic reaction to another. The measured electrochemical impedance spectrum corresponded to the proposed cathodic reaction mechanisms.

The effect of Ca addition on the elemental composition, microstructure, Brinell hardness and tensile properties of Al-7Si-0.3Mg alloy were investigated. The residual content of Ca in the alloy linearly increased with the amount of Ca added to the melt. The optimal microstructure and properties were obtained by adding 0.06wt% Ca to Al-7Si-0.3Mg alloy. The secondary dendrite arm spacing (SDAS) of the primary α phase decreased from 44.41 μm to 19.4 μm, and the eutectic Si changed from coarse plates to fine coral. The length of the Fe-rich phase (β-Al5FeSi) decreased from 30.2 μm to 3.8 um, and the Brinell hardness can reach to 66.9. The ultimate tensile strength, yield strength, and elongation of the resulting alloy increased from 159.5 MPa, 79 MPa, and 2.5% to 212 MPa, 86.5 MPa, and 4.5%, respectively. The addition of Ca can effectively refine the primary α phase and modify the eutectic Si phase, likely because Ca enrichment at the front of the solid-liquid interface led to undercooling of the alloy, reduced the growth rate of the primary α phase, and refined the grain size. Also, it could increase the latent heat of crystallization, undercooling, and the nucleation rate of eutectic Si, which was beneficial to the improvement of the morphology of eutectic Si.

Cu–Zn–Sn shape memory alloys (SMAs) with an average composition of 56.0at%, 36.1at%, and 7.9at% for Cu, Zn, and Sn, respectively, were successfully fabricated via an electrodeposition–annealing route. The produced SMAs were assessed for shape memory response in terms of percent displacement (martensite phase recovery) by subjecting the ternary alloys to flame tests and subsequently characterizing them via differential scanning calorimetry (DSC), optical microscopy, scanning electron microscopy in conjunction with energy- dispersive spectroscopy (SEM-EDS), and X-ray diffraction (XRD) analysis. The flame tests showed that the highest displacement was ca. 93%, with average austenite and martensitic start transformation temperature of 225°C and 222°C, respectively. XRD analysis revealed that the intermetallic phases responsible for the observed shape memory properties have substitutional Zn in the lattice occupied by Cu and Sn, leading to the formation of Cu(Zn,Sn) and Cu6(Zn,Sn)5 variants. The formation of these variants was attributed to the faster interdiffusion of Cu into Sn, driven by an activation energy of 34.82 kJ·mol−1. Five cycles of repeated torching–annealing revealed an essentially constant shape memory response, suggesting that the fabricated SMAs were consistent and sufficiently reliable for their intended service application.

Compared with the traditional pyrometallurgical process, copper bioleaching has distinctive advantages of high efficiency and lower cost, enabling efficiently extracts of valuable metal resources from copper sulfides. Moreover, during long-term industrial applications of bioleaching, many regulatory enhancements and technological methods are used to accelerate the interfacial reactions. With advances in microbial genetic and sequencing technologies, bacterial communities and their mechanisms in bioleaching systems have been revealed gradually. The bacterial proliferation and dissolution of sulfide ores by a bacterial community depends on the pH, temperature, oxygen, reaction product regulation, additives, and passivation substances, among other factors. The internal relationship among the influencing factors and the succession of microorganism diversity are discussed and reviewed in this paper. This paper is intended to provide a good reference for studies related to enhanced bioleaching.

k]The formation mechanism of acicular ferrite and its microstructural characteristics in 430 ferrite stainless steel with TiC additions were studied by theory and experiment. Using an “edge-to-edge matching” model, a 5.25 mismatch between TiC (FCC structure) and fer-ritic stainless steel (BCC structure) was identified, which met the mismatch requirement for the heterogeneous nucleation of 430 ferritic stainless steel. TiC was found to be an effective nucleation site for the formation of acicular ferrite in a smelting experiment, as analyzed by metallographic examination, Image-Pro Plus 6.0 analysis software, and SEM-EDS. Furthermore, small inclusions in the size of 2–4 μm increased the probability of acicular ferrite nucleation, and the secondary acicular ferrite would grow sympathetically from the initial acicular ferrite to produce multi-dimensional acicular ferrites. Moreover, the addition of TiC can increase the average microstrain and dislocation density of 430 ferrite stainless steel, as calculated by Williamson-Hall (WH) method, which could play some role in strengthening the dislocation.