Zeolite derived from coal-based solid wastes (coal gangue and coal fly ash) can overcome the environmental problems caused by coal-based solid wastes and achieve valuable utilization. In this paper, the physicochemical properties of coal gangue and coal fly ash are introduced. The mechanism and application characteristics of the pretreatment processes for zeolite synthesis from coal-based solid wastes are also introduced. The synthesis processes of coal-based solid waste zeolite and their advantages and disadvantages are summarized. Furthermore, the application characteristics of various coal-based solid waste zeolites and their common application fields are illustrated. Finally, we propose an alkaline fusion-assisted supercritical hydrothermal crystallization as an efficient method for synthesizing coal-based solid waste zeolites. In addition, more attention should be given to the recycling of alkaline waste liquid and the application of coal-based solid waste zeolites in the field of volatile organic compound adsorption removal.

Titanium-bearing blast furnace slag (BFS) has valuable compositions and potential environmental hazardousness. Thus, developing efficient and green approaches to utilize BFS is highly desired for resource economization and environmental protection. In the past decades, many attempts have been adopted to reuse BFS efficiently, and significant advances in understanding the fundamental features and the development of efficient approaches have been achieved. This review provides a comprehensive overview of the latest progress on the efficient utilization of BFS and discusses the mechanism and characteristics of various approaches, along with their application prospects. In particular, the extraction and enrichment of titanium-bearing phases from BFS are highlighted because of the high availability of titanium resources. This systemic and comprehensive review may benefit the design of new and green utilization routes with high efficiency and low cost.

High hydrogen absorption and desorption rates are two significant index parameters for the applications of hydrogen storage tanks. The analysis of the hydrogen absorption and desorption behavior using the isothermal kinetic models is an efficient way to investigate the kinetic mechanism. Multitudinous kinetic models have been developed to describe the kinetic process. However, these kinetic models were deduced based on some assumptions and only appropriate for specific kinetic measurement methods and rate-controlling steps (RCSs), which sometimes lead to confusion during application. The kinetic analysis procedures using these kinetic models, as well as the key kinetic parameters, are unclear for many researchers who are unfamiliar with this field. These problems will prevent the kinetic models and their analysis methods from revealing the kinetic mechanism of hydrogen storage alloys. Thus, this review mainly focuses on the summarization of kinetic models based on different kinetic measurement methods and RCSs for the chemisorption, surface penetration, diffusion of hydrogen, nucleation and growth, and chemical reaction processes. The analysis procedures of kinetic experimental data are expounded, as well as the effects of temperature, hydrogen pressure, and particle radius. The applications of the kinetic models for different hydrogen storage alloys are also introduced.

Metal halide perovskite solar cells have attracted considerable attention because of their high-power conversion efficiency and cost-effective solution-processable fabrication; however, they exhibit poor structural stability. Two-dimensional (2D) Ruddlesden–Popper (RP) perovskites could address the aforementioned issue and present excellent stability because of their hydrophobic organic spacer cations. However, the crystallographic orientation of 2D crystals should be perpendicular to the bottom substrates for charges to transport fast and be collected in solar cells. Moreover, controlling the crystallographic orientation of the 2D RP perovskites prepared by the solution process is difficult. Herein, we reviewed the progress of recent research regarding 2D RP perovskite films with the focus on the crystallographic orientation mechanism and orientation controlling methods. Furthermore, the current issues and prospects of 2D RP perovskites in the photovoltaic field were discussed to elucidate their development and application in the future.

Bacterial community dynamics and copper leaching with applied forced aeration were investigated during low-grade copper sulphide bioleaching to obtain better bioleaching efficiency. Results illustrated that appropriate aeration improved bacterial concentrations and leaching efficiencies. The highest bacterial concentration and Cu²⁺ concentration after 14-d leaching were 7.61 × 10⁷ cells·mL⁻¹ and 704.9 mg·L⁻¹, respectively, at aeration duration of 4 h·d⁻¹. The attached bacteria played a significant role during bioleaching from 1 to 7 d. However, free bacteria dominated the bioleaching processes from 8 to 14 d. This phenomenon was mainly caused by the formation of passivation layer through Fe³⁺ hydrolysis along with bioleaching, which inhibited the contact between the attached bacteria and ore. Meanwhile, 16S rDNA analysis verified the effect of Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans on the bioleaching process. The results demonstrate the importance of free and attached bacteria in bioleaching.

Peirce–Smith copper converting involves complex multiphase flow and mixing. In this work, the flow zone distribution and mixing time in a Peirce–Smith copper converter were investigated in a 1:5 scaled cold model. Flow field distribution, including dead, splashing, and strong-loop zones, were measured, and a dimensionless equation was established to determine the correlation of the effects of stirring and mixing energy with an error of <5%. Four positions in the bath, namely, injection, splashing, strong-loop, and dead zones, were selected to add a hollow salt powder tracer and measure the mixing time. Injecting a quartz flux through tuyeres or into the backflow point of the splashing wave through a chute was recommended instead of adding it through a crane hopper from the top of the furnace to improve the slag-making reaction.

The novel cast irons of chemical composition (wt%) 0.7C–5W–5Mo–5V–10Cr–2.5Ti were invented with the additions of 1.6wt% B and 2.7wt% B. The aim of this work was to study the effect of boron on the structural state of the alloys and phase elemental distribution with respect to the formation of wear-resistant structural constituents. It was found that the alloy containing 1.6wt% B was composed of three eutectics: (a) “M₂(C,B)₅+ferrite” having a “Chinese Script” morphology (89.8vol%), (b) “M₇(C,B)₃+Austenite” having a “Rosette” morphology, and (c) “M₃C+Austenite” having a “Ledeburite”-shaped morphology (2.7vol%). With 2.7wt% of boron content, the bulk hardness increased from HRC 31 to HRC 38.5. The primary carboborides M₂(C,B)₅ with average microhardness of HV 2797 appeared in the structure with a volume fraction of 17.6vol%. The volume fraction of eutectics (a) and (b, c) decreased to 71.2vol% and 3.9vol%, respectively. The matrix was “ferrite/austenite” for 1.6wt% B and “ferrite/pearlite” for 2.7wt% B. Both cast irons contained compact precipitates of carbide (Ti,M)C and carboboride (Ti,M)(C,В) with a volume fraction of 7.3%–7.5%. Based on the energy-dispersive X-ray spectroscopy, the elemental phase distributions and the appropriate phase formulas are presented in this work.

With the rapid development of 3C industries, the demand for high-thermal-conductivity magnesium alloys with high mechanical performance is increasing quickly. However, the thermal conductivities of most common Mg foundry alloys (such as Mg–9wt%–1wt%Zn) are still relatively low. In this study, we developed a high-thermal-conductivity Mg–4Al–4Zn–4RE–1Ca (wt%, AZEX4441) alloy with good mechanical properties for ultrathin-walled cellphone components via high-pressure die casting (HPDC). The HPDC AZEX4441 alloy exhibited a fine homogeneous microstructure (average grain size of 2.8 μm) with granular Al₁₁RE₃, fibrous Al₂REZn₂, and networked Ca₆Mg₂Zn₃ phases distributed at the grain boundaries. The room-temperature thermal conductivity of the HPDC AZEX4441 alloy was 94.4 W·m^–1·K^–1, which was much higher than 53.7 W·m^–1·K^–1 of the HPDC AZ91D alloy. Al and Zn in the AZEX4441 alloy were largely consumed by the formation of Al₁₁RE₃, Al₂REZn₂, and Ca₂Mg₆Zn₃ phases because of the addition of RE and Ca. Therefore, the lattice distortion induced by solute atoms of the AZEX4441 alloy (0.171%) was much lower than that of the AZ91D alloy (0.441%), which was responsible for the high thermal conductivity of the AZEX4441 alloy. The AZEX4441 alloy exhibited a high yield strength of ~185 MPa, an ultimate tensile strength of ~233 MPa, and an elongation of ~4.2%. This result indicated that the tensile properties were comparable with those of the AZ91D alloy. Therefore, this study contributed to the development of high-performance Mg alloys with a combination of high thermal conductivity, high strength, and good castability.

The effects of multipass friction stir processing (FSP) and Mg powder addition on the different microstructure parts, including the stir zone (SZ), heat-affected zone (HAZ), and thermomechanically affected zone (TMAZ) of Al 1050 alloy were investigated. Microstructural observations revealed that with the increase in the number of FSP passes, the grain size of the SZ decreased in the non-composite and composite samples, whereas that of the TMAZ and HAZ increased in the non-composite sample. Furthermore, the addition of Mg powder resulted in considerable grain refinement, and increasing the number of the FSP passes resulted in a more uniform distribution of Al–Mg intermetallic compounds in the in-situ composite sample. Results of the tensile test showed that the non-composite sample that underwent four passes of FSP exhibited a higher elongation percentage and a ductile fracture in comparison with those of the base metal and the composite sample. However, this sample exhibited a brittle fracture and a higher tensile strength in comparison with the base metal and the non-composite sample. The fabrication of composite samples resulted in a remarkable enhancement in hardness in comparison with the base metal and the non-composite samples that underwent FSP.

Al–Mg alloys are an important class of non-heat treatable alloys in which Mg solute and grain size play essential role in their mechanical properties and plastic deformation behaviors. In this work, a cyclical continuous expanded extrusion and drawing (CCEED) process was proposed and implemented on an Al–3Mg alloy to introduce large plastic deformation. The results showed that the continuous expanded extrusion mainly improved the ductility, while the cold drawing enhanced the strength of the alloy. With the increased processing CCEED passes, the multi-pass cross shear deformation mechanism progressively improved the homogeneity of the hardness distributions and refined grain size. Continuous dynamic recrystallization played an important role in the grain refinement of the processed Al–3Mg alloy rods. Besides, the microstructural evolution was basically influenced by the special thermomechanical deformation conditions during the CCEED process.

Multicomponent Al₂₀Cr₂₀Fe₂₅Ni₂₅Mn₁₀ alloys were synthesized using spark plasma sintering at different temperatures (800, 900, and 1000°C) and holding times (4, 8, and 12 min) to develop a high entropy alloy (HEA). The characteristics of spark plasma-synthesized (SPSed) alloys were experimentally explored through investigation of microstructures, microhardness, and corrosion using scanning electron microscopy coupled with energy dispersive spectroscopy (EDS), Vickers microhardness tester, and potentiodynamic polarization, respectively. X-ray diffraction (XRD) characterization was employed to identify the phases formed on the developed alloys. The EDS results revealed that the alloys consisted of elements selected in this work irrespective of varying sintering parameters. The XRD, EDS, and scanning electron microscopy collectively provided evidence that the fabricated alloys were characterized by globular microstructures exhibiting face-centered cubic phase, which was formed on a basis of solid solution mechanism. This finding implies that the SPSed alloy showed the features of HEAs. The alloy produced at 1000°C and holding time of 12 min portrayed an optimal microhardness of HV 447.97, but the value decreased to HV 329.47 after heat treatment. The same alloy showed an outstanding corrosion resistance performance. The increase in temperature resulted in an Al₂₀Cr₂₀Fe₂₅Ni₂₅Mn₁₀ alloy with superior density, microhardness, and corrosion resistance over the other alloys developed at different parameters.

Nanoparticles of potassium ferrite (KFeO₂) in this work were synthesized by a simple egg white solution method upon calcination in air at 773, 873, and 973 K for 2 h. The effects of calcination temperature on the structural and magnetic properties of the synthesized KFeO₂ nanoparticles were investigated. By varying the calcination temperature, X-ray diffraction and transmission electron microscopy results indicated the changes in crystallinity and morphology including particle size, respectively. Notably, the reduction in particle size of the synthesized KFeO₂ was found to have a remarkable influence on the magnetic properties. At room temperature, the synthesized KFeO₂ nanoparticles prepared at 873 K exhibited the highest saturation magnetization (M_S) of 2.07 × 10⁴ A·m⁻¹. In addition, the coercivity (H_C) increased from 3.51 to 16.89 kA·m⁻¹ as the calcination temperature increased to 973 K. The zero-field cooled (ZFC) results showed that the blocking temperatures (T_B) of about 125 and 85 K were observed in the samples calcined at 773 and 873 K, respectively. Therefore, this work showed that the egg white solution method is simple, cost effective, and environmentally friendly for the preparation of KFeO₂ nanoparticles.

The optimized growth parameters of graphene with different morphologies, such as dendrites, rectangle, and hexagon, have been obtained by low-pressure chemical vapor deposition on polycrystalline copper substrates. The evolution of fractal graphene, which grew on the polycrystalline copper substrate, has also been observed. When the equilibrium growth state of graphene is disrupted, its intrinsic hexagonal symmetry structure will change into a non-hexagonal symmetry structure. Then, we present a systematic and comprehensive study of the evolution of graphene with different morphologies grown on solid copper as a function of the volume ratio of methane to hydrogen in a controllable manner. Moreover, the phenomena of stitching snow-like graphene together and stacking graphene with different angles was also observed.

This study explores the fabrication of Fe-based amorphous/crystalline coating by air plasma spraying and its dependency on the coating parameters (plasma power, primary gas flow rate, powder feed rate, and stand-off distance). X-ray diffraction of the coatings deposited at optimized spray parameters showed the presence of amorphous/crystalline phase. Coatings deposited at a lower plasma power and highest gas flow rate exhibited better density, hardness, and wear resistance. All coatings demonstrated equally good resistance against the corrosive environment (3.5wt% NaCl solution). Mechanical, wear, and tribological studies indicated that a single process parameter optimization cannot provide good coating performance; instead, all process parameters have a unique role in defining better properties for the coating by controlling the in-flight particle temperature and velocity profile, followed by the cooling pattern of molten droplet before impingement on the substrate.

Ni-based composite coatings incorporated with nano/micron SiC particles were fabricated via electrochemical co-deposition in Watts bath, followed by the evaluation of their mechanical and anti-corrosion properties. The micrographic observations suggest that the SiC particles with various sizes can be well incorporated to the Ni substrate. X-ray diffraction (XRD) patterns indicate that SiC particles with smaller sizes could weaken the preferential growth of Ni along (200) facet. In addition, it is found that the incorporated SiC particles with medium micron sizes (8 and 1.5 μm) could significantly enhance the micro-hardness of the Ni composite coatings. Nevertheless, electrochemical measurements demonstrate that micron-sized SiC particles would weaken the corrosion resistance of Ni composite coatings ascribed to the structure defects induced. In contrast, the combined incorporation of nanosized (50 nm) SiC particles with medium micron (1.5 μm) ones is capable of promoting the compactness of the composite coatings, which is beneficial to the long-term corrosion resistance with negligible micro-hardness loss.

This paper presents an experimental investigation of the mechanical and tribological properties of Cu–graphene nanosheets (GN) nanocomposites. We employed the electroless coating process to coat GNs with Ag particles to avoid its reaction with Cu and the formation of intermetallic phases. We analyzed the effect of GN content on the structural, mechanical, and tribological properties of the produced nanocomposites. Results showed that the electroless coating process is an efficient technique to avoid the reaction between Cu and C and the formation of intermetallic phases. The addition of GNs significantly improves the mechanical and tribological properties of Cu nanocomposites. However, the addition of GNs needs to be done carefully because, after a certain threshold value, the mechanical and tribological properties are negatively affected. The optimum GN content is determined to be 0.5vol%, at which hardness, wear rate, and coefficient of friction are improved by 13%, 81.9%, and 49.8%, respectively, compared with Cu nanocomposites. These improved properties are due to the reduced crystallite size, presence of GNs, and homogenous distribution of the composite constituents.

Mica was used as a supporting matrix for composite phase change materials (PCMs) in this work because of its distinctive morphology and structure. Composite PCMs were prepared using the vacuum impregnation method, in which mica served as the supporting material and polyethylene glycol (PEG) served as the PCM. Fourier transform infrared and X-ray diffraction analysis confirmed that the addition of PEG had no effect on the crystal structure of mica. Moreover, no chemical reaction occurred between PEG and mica during the vacuum impregnation process, and no new substance was formed. The maximum load of mica-stabilized PEG was 46.24%, the phase change temperature of M₄₀₀/PEG was 46.03°C, and the latent heat values of melting and cooling were 77.75 and 77.73 J·g⁻¹, respectively. The thermal conductivity of M₄₀₀/PEG was 2.4 times that of pure PEG. The thermal infrared images indicated that the thermal response of M₄₀₀/PEG improved relative to that of pure PEG. The leakage test confirmed that mica could stabilize PEG and that M₄₀₀/PEG had great form-stabilized property. These results demonstrate that M₄₀₀/PEG has potential in the field of building energy conservation.

The aim of this investigation was to prepare geopolymeric precursor from vanadium tailing (VT) by thermal activation and modification. For activation, a homogeneous blend of VT and sodium hydroxide was calcinated at an elevated temperature and then modified with metakaolin to produce a geopolymeric precursor. During the thermal activation, the VT was corroded by sodium hydroxide and then sodium silicate formed on the particle surfaces. After water was added, the sodium silicate coating dissolved to release silicon species, which created an alkaline solution environment. The metakaolin then dissolved in the alkaline environment to generate aluminum species, which was followed by geopolymerization. The VT particles were connected by a gel produced during geopolymerization, which yielded a geopolymer with excellent mechanical performance. This investigation not only improves the feasibility of using geopolymer technology for large-scale and in-situ applications, but also promotes the utilization of VT and other silica-rich solid wastes.