Selective laser melting (SLM), an additive manufacturing process mostly applied in the metal material field, can fabricate complex-shaped metal objects with high precision. Nickel-based superalloy exhibits excellent mechanical properties at elevated temperatures and plays an important role in the aviation industry. This paper emphasizes the research of SLM processed Inconel 718, Inconel 625, CM247LC, and Hastelloy X, which are typical alloys with different strengthening mechanisms and operating temperatures. The strengthening mechanism and phase change evolution of different nickel-based superalloys under laser irradiation are discussed. The influence of laser parameters and the heat-treatment process on mechanical properties of SLM nickel-based superalloys are systematically introduced. Moreover, the attractive industrial applications of SLM nickel-based superalloy and printed components are presented. Finally, the prospects for nickel-based superalloy materials for SLM technology are presented.

Tribology, which is the study of friction, wear, and lubrication, largely deals with the service performance of structural materials. For example, newly emerging high-entropy alloys (HEAs), which exhibit excellent hardness, anti-oxidation, anti-softening ability, and other properties, enrich the wear-resistance alloy family. To demonstrate the tribological behavior of HEAs systematically, this review first describes the basic tribological characteristics of single-, dual-, and multi-phase HEAs and HEA composites at room temperature. Then, it summarizes the strategies that improve the tribological property of HEAs. This review also discusses the tribological performance at elevated temperatures and provides a brief perspective on the future development of HEAs for tribological applications.

Current electronic technology based on silicon is approaching its physical and scientific limits. Carbon-based devices have numerous advantages for next generation electronics (e.g., fast speed, low power consumption and simple process), that when combined with the unique nature of the versatile allotropes of carbon elements, are creating an electronics revolution. Carbon electronics are greatly advancing with new preparations and sophisticated designs. In this perspective, representatives with various dimensions, e.g., carbon nanotubes, graphene, bulk diamond, and their extraordinary performance, are reviewed. The associated state-of-the-art devices and composite hybrid all-carbon structures are also emphasized to reveal their potential in the electronics field. Advances in commercial production have improved the cost efficiency, material quality, and device design, accelerating the promise of carbon materials.

Porous materials have promise as sound insulation, heat barrier, vibration attenuation, and catalysts. Most industrial solid wastes, such as tailings, coal gangue, and fly ash are rich in silicon. Additionally, a high silicon content waste is a potential raw material for the synthesis of silicon-based, multi-porous materials such as zeolites, mesoporous silica, glass–ceramics, and geopolymer foams. Representative silicon-rich industrial solid wastes (SRISWs) are the focus of this mini review of the processing and application of porous silicon materials with respect to the physical and chemical properties of the SRISW. The transformation methods of preparing porous materials from SRISWs are summarized, and their research status in micro-, meso-, and macro-scale porous materials are described. Possible problems in the application of SRISWs and in the preparation of functional porous materials are analyzed, and their development prospects are discussed. This review should provide a typical reference for the recycling and use of industrial solid wastes to develop sustainable “green materials.”

The interface characteristics of cyanide tailings are different from those of the raw ore. In this study, valuable elements could not be thoroughly recovered via the flotation of cyanide tailings from Shandong, China. The interface and floatability of these tailings were investigated by phase analysis and flotation tests. The chalcopyrite in the cyanide tailings was fine and had a porous surface. The floatability of 68% chalcopyrite was similar to that of galena in the presence of a collector. A layer of fine galena particles compactly wrapped the chalcopyrite. The chalcopyrite recovery sharply decreased as the nonpolar oil residue in cyanide tailings was extracted using alcohol; however, this removal had no effect on the galena. The remaining chalcopyrite in the flotation tailings was covered with an oxidation layer consisting of O, Fe, S, Pb, Cu, Zn, and Si.

Reverse flotation desilication is an indispensable step for obtaining high-grade fluorapatite. In this work, dodecyltrimethylammonium bromide (DTAB) is recommended as an efficient collector for the reverse flotation separation of quartz from fluorapatite. Its collectivity for quartz and selectivity for fluorapatite were also compared with figures corresponding to the conventional collector dodecylamine hydrochloride (DAC) via microflotation experiments. The adsorption behaviors of DTAB and DAC on minerals were systematically investigated with surface chemical analyses, such as contact angle determination, zeta potential detection, and adsorption density measurement. The results revealed that compared to DAC, DTAB displayed a similar and strong collectivity for quartz, and it showed a better selectivity (or worse collectivity) for fluorapatite, resulting in a high-efficiency separation of the two minerals. The surface chemical analysis results showed that the adsorption ability of DTAB on the quartz surface was as strong as that of DAC, whereas the adsorption amount of DTAB on the fluorapatite surface was much lower than that of DAC, which is associated with the flotation performance. During the floatation separation of the actual ore, 8wt% fluorapatite with a higher grade can be obtained using DTAB in contrast to DAC. Therefore, DTAB is a promising collector for the high-efficiency purification and sustainable utilization of valuable fluorapatite recourses.

Petroleum coke is industrial solid wastes and its disposal and storage has been a great challenge to the environment. In this study, petroleum coke was utilized as a novel co-reduction reductant of low-grade laterite ore and red mud. A ferronickel product of 1.98wt% nickel and 87.98wt% iron was obtained with 20wt% petroleum coke, when the roasting temperature and time was 1250°C and 60 min, respectively. The corresponding recoveries of nickel and total iron were 99.54wt% and 95.59wt%, respectively. Scanning electron microscopy–energy dispersive spectrometry (SEM–EDS) analysis showed metallic nickel and iron mainly existed in the form of ferronickel particles which distributed uniformly at a size of approximately 30 μm with high purity. This study demonstrated that petroleum coke is a promising reductant in the co-reduction of laterite ore and red mud. Compared to other alternatives, petroleum coke is advantageous with reduced production cost and high applicability in anthracite-deficient areas.

Combustion kinetics of the hydrochar was investigated using a multi-Gaussian-distributed activation energy model (DAEM) to expand the knowledge on the combustion mechanisms. The results demonstrated that the kinetic parameters calculated by the multi-Gaussian-DAEM accurately represented the experimental conversion rate curves. Overall, the feedstock combustion could be divided into four stages: the decomposition of hemicellulose, cellulose, lignin, and char combustion. The hydrochar combustion could in turn be divided into three stages: the combustion of cellulose, lignin, and char. The mean activation energy ranges obtained for the cellulose, lignin, and char were 273.7–292.8, 315.1–334.5, and 354.4–370 kJ/mol, respectively, with the standard deviations of 2.1–23.1, 9.5–27.4, and 12.1–22.9 kJ/mol, respectively. The cellulose and lignin contents first increased and then decreased with increasing hydrothermal carbonization (HTC) temperature, while the mass fraction of char gradually increased.

A new method is proposed for the recovery of Mn via the direct electrochemical reduction of LiMn₂O₄ from the waste of lithium-ion batteries in NaCl−CaCl₂ melts at 750°C. The results show that the LiMn₂O₄ reduction process by the electrochemical method on the coated electrode surface occurs in three steps: Mn(IV) → Mn(III) → Mn(II) → Mn. The products of this electro-deoxidation are CaMn₂O₄, MnO, (MnO)_x(CaO)_1−x, and Mn. Metal Mn appears when the electrolytic voltage increases to 2.6 V, which indicates that increasing the voltage may promote the deoxidation reaction process. With the advancement of the three-phase interline (3PI), electric deoxygenation gradually proceeds from the outer area of the crucible to the core. At high voltage, the kinetic process of the reduction reaction is accelerated, which generates double 3PIs at different stages.

The effect of extrusion temperature and ratio on the microstructure, hardness, compression, and corrosion behavior of Mg–5Zn–1.5Y alloy were analyzed in this study. The microstructural observations revealed that the cast alloy consists of α-Mg grains, and Mg₃Zn₆Y and Mg₃Zn₃Y₂ intermetallic compounds, mostly located on the α-Mg grain boundaries. Extruded alloy at higher temperatures showed coarser grain microstructures, whereas those extruded at higher ratios contained finer ones, although more dynamic recrystalized grains with lower intermetallics were measured at both conditions. Combined conditions of the lower temperature (340°C) and higher ratio (1:11.5) provided higher compressive strengths. However, no significant hardness improvement was achieved. The extrusion process could decrease the corrosion rate of the cast alloy in simulated body fluid for over 80% due to primarily the refined microstructure. The extrusion temperature showed a more pronounced effect on corrosion resistance compared to the extrusion ratio, and the higher the extrusion temperature, the higher the corrosion resistance.

Transition metal phosphides (TMPs) have exhibited decent performance in an oxygen evolution reaction (OER), which is a kinetic bottleneck in many energy storages and conversion systems. Most reported catalysts are composed of three or fewer metallic components. The inherent complexity of multicomponent TMPs with more than four metallic components hinders their investigation in rationally designing the structure and, more importantly, comprehending the component-activity correlation. Through hydrothermal growth and subsequent phosphorization, we reported a facile strategy for combining TMPs with tunable elemental compositions (Ni, Fe, Mn, Co, Cu) on a two-dimensional titanium carbide (MXene) flake. The obtained TMPs/MXene hybrid nanostructures demonstrate homogeneously distributed elements. They exhibit high electrical conductivity and strong interfacial interaction, resulting in an accelerated reaction kinetics and long-term stability. The results of different component catalysts’ OER performance show that NiFeMnCoP/MXene is the most active catalyst, with a low overpotential of 240 mV at 10 mA·cm⁻², a small Tafel slope of 41.43 mV·dec⁻¹, and a robust long-term electrochemical stability. According to the electrocatalytic mechanism investigation, the enhanced NiFeMnCoP/MXene OER performance is due to the strong synergistic effect of the multi-elemental composition. Our work, therefore, provides a scalable synthesis route for multi-elemental TMPs and a valuable guideline for efficient MXene-supported catalysts design.

Frequent offshore oil spill accidents, industrial oily sewage, and the indiscriminate disposal of urban oily sewage have caused serious impacts on the human living environment and health. The traditional oil–water separation methods not only cause easily environmental secondary pollution but also a waste of limited resources. Therefore, in this work, three-dimensional (3D) graphitic carbon sphere (GCS) foams (collectively referred hereafter as 3D foams) with a 3D porous structure, pore size distribution of 25–200 μm, and high porosity of 62vol% were prepared for oil adsorption via gel casting using GCS as the starting materials. The results indicate that the water contact angle (WCA) of the as-prepared 3D foams is 130°. The contents of GCS greatly influenced the hydrophobicity, WCA, and microstructure of the as-prepared samples. The adsorption capacities of the as-prepared 3D foams for paraffin oil, vegetable oil, and vacuum pump oil were approximately 12–15 g/g, which were 10 times that of GCS powder. The as-prepared foams are desirable characteristics of a good sorbent and could be widely used in oil spill accidents.

ZrC and ZrB₂ are both typical ultra-high temperature ceramics, which can be used in the hyperthermal environment. In this study, a method for preparing ultrafine ZrC–ZrB₂ composite powder was provided, by using the raw materials of nano ZrO₂, carbon black, B₄C, and metallic Ca. It is worth pointing out that ZrC–ZrB₂ composite powder with any proportion of ZrC to ZrB₂ could be synthesized by this method. Firstly, a mixture of ZrC and C was prepared by carbothermal reduction of ZrO₂. By adjusting the addition amount of B₄C, ZrC was boronized by B₄C to generate ZrC–ZrB₂ composite powder with different compositions. Using this method, five composite powders with different molar ratios of ZrC and ZrB₂ (100ZrC, 75ZrC–25ZrB₂, 50ZrC–50ZrB₂, 25ZrC–75ZrB₂, and 100ZrB₂) were prepared. When the temperature of boronization and decarburization process was 1473 K, the particle size of product was only tens of nanometres. Finally, the oxidation characteristics of different composite powders were investigated through oxidation experiments. The oxidation resistance of ZrC–ZrB₂ composite powder continued to increase as the content of ZrB₂ increased.

Hexavalent chromium (Cr(VI)) compound is useful to various industries but is toxic and carcinogenic. In this research work, we fabricate an amperometric sensor for the determination of Cr(VI), using a titanium dioxide (TiO₂)-reduced graphene oxide (rGO) composite as the sensing element. The composite was synthesized following sol−gel chemistry, yielding TiO₂ nanoparticles of ~50 nm in size, immobilized on chemically exfoliated rGO sheets. The composite was employed in a 3-electrode electrochemical cell and operated in an amperometric mode, exhibiting good responses to the 50 to 500 ppb Cr(VI). Our best result from pH 3 Mcilvane’s buffer medium reveals the sensitivity of 9.12 × 10⁻⁴ ppb⁻¹ and a detection limit of 6 ppb with no signal interference from 200 ppm Ca(II), 150 ppm Mg(II), and 50 ppb Pb(II). The excellent results of the TiO₂-rGO sensor can be attributed to synergic effects between TiO₂ and rGO, resulting from the presence of n-p heterojunctions and the formation of the TiO₂ nanoparticles on rGO.

8-hydroxyquinoline (8-HQ) intercalated layered double hydroxides (LDH) film as underlayer and sol–gel layer was combined for active corrosion protection of the AM60B magnesium alloy. The LDH, LDH/sol–gel, and LDH@HQ/sol–gel coatings were analyzed using the scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), atomic force microscopy (AFM), and electrochemical impedance spectroscopy (EIS) methods. The SEM images showed that the surface was entirely coated by the LDH film composed of vertically-grown nanosheets. The same morphology was observed for the LDH/sol–gel and LDH@HQ/sol–gel coatings. Also, almost the same topography was observed for both composite coatings except that the LDH@HQ/sol–gel coating had relatively higher surface roughness. Although the LDH film had the same impedance behavior as the alloy sample in 3.5wt% NaCl solution, its corrosion resistance was much higher, which could be due to its barrier properties as well as to the trapping of the chloride ions. Similar to the LDH film, the corrosion resistance of the LDH/sol–gel composite diminished with increasing the exposure time. However, its values were much higher than that of the LDH film, which was mainly related to the sealing of the solution pathways. The LDH@HQ/sol–gel composite showed much better anti-corrosion properties than the LDH/sol–gel coating due to the adsorption of the 8-HQ on the damaged areas through the complexation.

The composition and structure of substrate materials have important influences on coating performance, especially in terms of bonding strength and coating hardness, which determine whether the coating can be used for a given application. In this study, a TiAlN coating is deposited on Ti(C,N)-based cermet (TC) substrates with 0wt%–20wt% WC by arc ion plating. The influence of cermet substrate characteristics on the structure and properties of the TiAlN coating is then researched. Results show that the TiAlN coating deposited on the TC substrate has a columnar grain structure. As WC increases, the strength ratio of I₍₁₁₁₎/I₍₂₀₀₎ and adhesive strength of TiAlN gradually increases. In the absence of WC in the substrate, the preferred orientation of the TiAlN coating is (200). As WC increases, the preferred orientation of the TiAlN coating becomes (111) and (200). Notable differences in adhesive strength between the coating and substrate could be attributed to the microstructure and composition of the latter. Scratching results show that the adhesive strengths of the TiAlN coating on the 0wt%–20wt% WC cermet substrate are 52–65 N. Among the coatings obtained that on the TC substrate with 15wt% WC presents the highest H/E and H³/E², which indicates that this coating also features the best wear resistance. The failure mechanisms of the coated tools include coating peeling, adhesive wear, and abrasive wear. As the cutting speed increases, the degree of flank wear increases and the durability of the coating decreases accordingly. Increases in WC result in an initial decrease followed by a gradual increase in the flank wear of the coated cermet inserts.

Copper nanowires (CuNWs) are promising electrode materials, especially for used in flexible and transparent electrodes, due to their advantages of earth-abundant, low-cost, high conductivity and flexibility. However, the poor stability of CuNWs against oxidation and chemical corrosion seriously hinders their practical applications. Herein, we propose a facile strategy to improve the chemical stability of CuNWs by in situ coating of carbon protective layer on top of them through hydrothermal carbonization method. The influential factors on the growth of carbon film including the concentration of the glucose precursor (carbon source), hydrothermal temperature, and hydrothermal time are systematically studied. By tailoring these factors, carbon layers with thickness of 3–8 nm can be uniformly grown on CuNWs with appropriate glucose concentration around 80 mg·mL⁻¹, hydrothermal temperature of 160–170°C, and hydrothermal time of 1–3 h. The as-prepared carbon-coated CuNWs show excellent resistance against corrosion and oxidation, and are of great potential to use broadly in various optoelectronic devices.

Municipal solid waste incineration products of bottom ash (BA), fly ash (FA), and pickling sludge (PS), causing severe environmental pollution, were transformed into glass ceramic foams with the aid of CaCO₃ as a pore-foaming agent during sintering. The effect of the BA/FA mass ratio on the phase composition, pore morphology, pore size distribution, physical properties, and glass structure was investigated, with results showing that with the increase in the BA/FA ratio, the content of the glass phase, Si–O–Si, and Q³Si units decrease gradually. The glass transmission temperature of the mixture was also reduced. When combined, the glass viscosity decreases, causing bubble coalescence and uneven pore distribution. Glass ceramic foams with uniform spherical pores are fabricated. When the content of BA, FA, and PS are 35wt%, 45wt%, and 20wt%, respectively, contributing to high performance glass ceramic foams with a bulk density of 1.76 g/cm³, porosity of 56.01%, and compressive strength exceeding 16.23 MPa. This versatile and low-cost approach provides new insight into synergistically recycling solid wastes.