Literature studies have not reported an applicable model for electrical conductivity of carbon nanofiber (CNF) polymer composites. This study presents a theoretical methodology for conductivity of carbon nanofiber (CNF) polymer composites by CNF effective volume fraction, interphase thickness, percolation onset, CNF dimensions, CNF waviness, fraction of networked CNF, and tunneling size. The suggested model has been approved by comparing the experimental outputs with calculations. The predictions depict good agreement with the experimental data of several samples. In addition, the impressions of the main factors on the conductivity have been confirmed to justify the proposed model. Some terms, such as the percentage of percolated CNF, filler volume fraction, and tunneling distance, significantly control the conductivity, while percolation onset and CNF waviness unimportantly affect the electrical conductivity of CNF-filled composites.

The microstructure evolution of Al-1 wt% Si alloy wires with a diameter of 50.8 μm bonded on Cu metallization was investigated under electromigration (EM) tests with a current density of 7 × 104 A/cm2 at an ambient temperature of 150 °C. After the EM tests, microstructure of the wire evolved from submicron slender grains into bamboo-type grains with diameters 100 times larger than the original ones because of anisotropic grain growth (AGG) in the radial direction of wire. The orientations of grains also changed from highly [111] oriented into random distribution. In addition, bamboo nodes created by distortion of bamboo-type grains were found near cathodes while protrusions were observed near anodes of the wire. The mechanisms of AGG as well as the orientation change are proposed and delineated in this study.

The content of Ce plays an important role in balancing the strength and plasticity of Al-Ce alloys, because it seriously affects the morphology and distribution of Ce-rich phase. Electromagnetic stirring (EMS) is an effective process for controlling Ce-rich phase. The effects of EMS on Ce-rich phase in hypoeutectic, eutectic and hypereutectic Al-Ce alloys were mainly studied. The results show that eutectic Al11Ce3 phase transits from lamellar-like to fibrous-like in Al-8Ce alloy and Al-12Ce alloy after EMS. The refinement of the lamellar spacings and eutectic Al11Ce3 fibres is insignificant, and the effect of load transfer strengthening and grain refining strengthening is unsatisfactory. Coarser primary Al11Ce3 phase is broken and eutectic Al11Ce3 phase is refined and spheroidized in Al-14Ce alloy after EMS. The lamellar spacing and eutectic Al11Ce3 fibre size greatly decrease in Al-14Ce alloy, from 2.14 μm to 1.28 μm and 0.94 μm to 0.43 μm, respectively. The load transfer strengthening and fine grain strengthening are enhanced. The tensile strength increases from 116.8 MPa to 184.6 MPa, the yield strength increases from 74.5 MPa to 107.6 MPa, and the elongation increases from 1.4% to 7.1%. This reflects that EMS play a more beneficial role in Al-14Ce alloy.

The Ti-7Al-1Mo-0.5V-0.1C alloy exhibits low density and good mechanical properties, and has potential applications in aerospace industries. The microstructure features of titanium alloys, such as the morphology and volume fraction of the primary α phase (αp) and the precipitation of the secondary α phase (αs), are sensitive to heat treatment parameters, especially the cooling rate from the two-phase region. In this work, we have characterized the precipitation of the secondary α phase and ordered α2 phase in Ti-7Al-1Mo-0.5V-0.1C alloy under water quenching, air cooling, and furnace cooling, and have investigated their effects on the mechanical properties of the Ti-7Al-1Mo-0.5V-0.1C alloy. The results show that the secondary α phase is significantly coarsened in the air-cooled alloy and leads to an increase in the strength but decrease in the ductility of the alloy, while the equiaxed microstructure generated in the furnace-cooled alloy, with no precipitation of the secondary α phase and an increase in size of the ordered α2 precipitation phase within the primary α phase, contributes to a further increase in ductility.

A novel co-modification method between BOF slag and copper slag is proposed for the effective recovery of valuable metals in the metallurgical slags. The co-modification reactions between the Ca-containing phases in BOF slag and fayalite in copper slag are discussed on the basis of thermodynamic analysis, and the co-modification effect on the phase reconstruction and separation of iron oxides from Ca-containing and Si-containing complex compounds in the co-modified slag are investigated by a laboratory experiment. The effects of carbothermal reduction conditions, including the basicity of co-modified slag, reduction temperature, and C/O molar ratio, on the metal recovery rate are evaluated and optimized. The results under optimal process conditions show that it is possible to extract metals in the co-modified slag as Fe-Cu-Mn alloy with a lower P content, and to realize the stabilization of the secondary slag without free lime and periclase.

Cathodic plasma electrolytic nitriding (c-PEN) technique has been utilized to modify a low-alloy ferritic steel (2.25Cr-1Mo) surface and assess the effect of the c-PEN layer on corrosion, hydrogen permeation, and tribological behavior of the steel. The surface morphology and phase composition of the c-PEN-treated surface were analyzed, and it was found that the surface exhibits a globular network morphology of iron nitride and expanded ferrite. The potentiodynamic polarization results showed that the c-PEN treatment created an electrochemically noble surface compared to the untreated steel. Next, electrochemical hydrogen permeation experiments carried out on the nitrided surface exhibited a noticeable drop in hydrogen permeability, diffusivity, and reversible trap density of the steel. Furthermore, based on nanomechanical and tribological characterization, the c-PEN treatment was found to create a noticeably harder and wear-resistant surface. Overall, these findings demonstrate the applicability of c-PEN treatment to create a multi-functional coating for low-alloy steels that can assist in mitigating the effect of various harsh environments.

In the present study, molten Al 2024 alloy was subjected to two different electromagnetic flow directions, i.e., (1) irreversible clockwise (CW) and (2) reversible clockwise–anticlockwise (CW-ACW) direction rotational magnetic fields (RMF) at constant and varying intervals. The construction allows the aluminum melt to solidify in the TP-1 mold under a combination of directional solidification with a forced convection mechanism. With the help of computer-based simulation, secondary flow and variation in temperature profiles have been evaluated. The effect of the electromagnetic stirring current and pouring temperature on the microstructural morphology of the Al 2024 alloy has been analyzed by experimental work. It was found that at a low pouring temperature (913 K) with an increase in current value (6–9 A), when CW-ACW RMF is applied, the grain size of the sample was finer compared to the CW RMF. In contras, at higher pouring temperatures (943–993 K) and the same current value, better grain size refinement was observed in the case of the CW RMF samples. However, deviation in the grain refinement trend was observed at a current of 11 A at low and higher pouring temperature. The best grain refinement was achieved at a pouring temperature of 993 K with a 7.5-A current in an irreversible direction.

This study aimed to increase the recovery efficiency of nickel metal and reduce smelting energy consumption by analyzing the effect of adding B2O3 on the melting characteristics of nickel flash melting slag and the separation of slag and matte. In particular, thermodynamic analysis and high-temperature experimental investigations showed that adding B2O3 decreased the melting temperature of the slag system and enhanced the slag flow characteristics. Furthermore, the primary process parameters required for slag and nickel matte separation were predicted and optimized using single-factor experiments and the response surface method. The degree of the effect on the slag-matte separation was as follows: temperature > MgO content > FeO/SiO2 > B2O3 content. The optimal separation conditions were settling temperature 1300°C, MgO content 8 wt.%, FeO/SiO2 1.55, and B2O3 content 2.4 wt.%. The mechanism demonstrated that adding B2O3 could significantly reduce the impact of low-quality nickel ore on smelting. Moreover, the separation and recovery of the matte and slag were both successful. Findings indicate that an efficient way to optimize the smelting process is adding B2O3, which is expected to improve the development of metal recovery technologies.

Asymmetric porous filter elements can reach a high filtering accuracy with a larger filtration flux, which can enhance the filtration efficiency and reduce the energy consumption when applied in separation equipment. A novel porous material of Ti-Si intermetallic compound micro-porous membrane has been successfully synthesized with Fe-doped Ti mixed powder and SiO2 by the in situ reactive sintering process. The effects of Fe doping amount on the formation of the membrane has been systemically studied. The results show that increasing the Fe doping amount can improve the in situ reactive process and promote membrane formation. The synthesized granules on the membrane are well distributed, with an average size of 1–3 µm, and the average thickness of the membranes is 4–7 µm. The relative air permeability coefficient of the porous membrane reduces with the increasing Fe doping amount. All the synthesized membranes show the presence of Ti5Si3 and Ti phases, with small amounts of FeTi and FeO. The membrane formation mechanism is due to the large reduction reactivity of Fe-doped Ti powder with SiO2, and, finally, the asymmetric porous structure of Ti5Si3/Ti was obtained.

In the present investigation, H13 tool steels were repeatedly exposed to thermal shock at 5000, 10,000, and 15,000 cycles, similar to actual industrial operations, using an in-house-built thermal shock fatigue cyclic (TSFC) treatment machine. The thermally shocked specimens were then subjected to a novel enhancement heat-treatment process using tempering and quenching techniques. All the TSFC-treated specimens and the enhanced heat-treated specimens were characterized by hardness, tensile, X-ray diffraction, microscopy, magnetic, and wear tests. The intriguing shifts in the values of hardness, mechanical properties, crystal structures, and crack initiations were observed before and after the enhancement heat-treatment process. Superior mechanical properties were obtained at 10,000 cycles of the TSFC H13 steel specimens where the crack initiation was also minimal. Loss in magnetic properties was also observed for TSFC H13 tool steel specimens. Interestingly, after the enhancement heat-treatment process, all the TSFC H13 steel specimens significantly recovered their mechanical properties. Thus, the present thermal fatigue cycles up to 15,000 cycles of 30 s at 670°C would be worthy of failure prediction. On the other hand, the novel enhancement heat-treatment process helped to recover the lost mechanical properties of the samples. Therefore, the present study will prolong the life of the die-casting components and significantly cut down the production cost.

The femtosecond laser ablation of a wide bandgap semiconductor is characterized by a complicated energy transfer and rarely explored process. A coupled two-temperature-Fourier heat conduction model is developed to investigate the energy deposition and material removal mechanisms of femtosecond laser ablating silicon carbide (SiC). Absorption mechanisms, temperature distribution, and threshold fluence are investigated. Non-thermal melting and thermal melting processes are calculated. The results show that during the interaction between laser and SiC, the main absorption mechanism was governed by multiphoton absorption and Auger recombination. Simulation results of the new model show that the influence of latent heat on lattice temperature is insignificant and the heat accumulation on the surface is little. The obtained damage threshold represents reasonable prediction, based on comparison with experimental and literature data. The damage threshold and the non-thermal melting threshold for 800 nm increase with the pulse duration. The thermal melting occurs immediately after non-thermal melting at high fluence. The molten layer thickens logarithmically with the increase of the fluence.

In this research, directed energy deposition (DED) experiments were conducted for the first time near freezing point temperature of 0°C. The objective was to demonstrate the on-site repair and remanufacturing capabilities using the DED process in cold environments like in the Northern Hemisphere in winter. The DED ambient and substrate temperatures were reduced to mimic the on-site DED process performed near freezing point temperature. Six single-track samples were printed at two different ambient temperatures (three samples printed at 20°C and another three samples printed at − 3°C) with 316L stainless steel powder. The molten pool evolution, sample geometries, internal crack, and hardness were investigated. It is found that at cold ambient temperatures, the DED process can be performed smoothly, and there was no obvious crack in the samples printed near the freezing point. The DED deposition at − 3°C had a larger melt pool zone and generated greater deposition height. In addition, at the temperature of − 3°C, the deposited samples had higher hardness values. Based on these experimental findings, it was concluded that the DED process can be performed near freezing point temperature, and the printed part is larger in size with better mechanical strength.

In this study, a roasting-water leaching green process for highly selective lithium extraction from the cathode material of spent lithium iron phosphate (LiFePO4) battery was proposed. Using spent LiFePO4 as raw material and sodium bisulfate (NaHSO4) as an additive, the best roasting parameters were determined as follows: molar ratio of LiFePO4/NaHSO4 1:1.25, roasting temperature 400°C and roasting time 5 h. Under this condition, using pure water as a leaching agent, with leaching efficiency of 99.08% for Li and 0.12% for Fe, achieved the goal of high-selective leaching of Li. The study of the roasting mechanism shows that H and Li have similar external electron arrangements and coordination environments. Under the influence of temperature, the reactivity of the solid is improved, and the thermal, chemical reaction is initiated at the nanometer scale, resulting in the local rearrangement of particles, resulting in the reaction of LiFePO4 and NaHSO4 to generate LiNaSO4, which is helpful for subsequent leaching. This study can provide a process reference for high-selective recovery of Li in spent LiFePO4 batteries.

During sinter pot tests, Ni-containing sinter indices are greatly improved by the appropriate proportioning of different types of limonitic nickel laterite and application of sintering strengthening technology. After optimization, tumble index and productivity of Ni-containing sinter are increased by 27.17% and 20.62%, respectively, and solid fuel rate is reduced by 27.63% compared with the base case. In addition, the metallurgical performance is overall better with higher RI, similar RDI and narrower softening and melting drop intervals. The appropriate proportioning of different types of limonitic nickel laterite and the application of multi-force field strengthening technology contribute to the reduction of (MgO + Al2O3)/SiO2 mass ratio, further densification of sinter layer and extension of holding time of high temperature during sintering. Compared with the base case, sinter porosity is reduced from 48.92% to 20.18% and SFCA amount is increased from 8.78% to 27.12%. Much better quality Ni-containing sinter is consequently obtained.

The crystalline structure, magnetic properties, and magnetocaloric effect (MCE) of MnCo1−xCrxGe (x = 0.01, 0.03, 0.05, 0.07) alloys have been investigated using x-ray powder diffraction (XRD) analysis and physical property measurement system magnetic measurements. With a small portion of substitution of the Co by Cr, the crystalline structure is renovated from the coexistent phase of orthorhombic–hexagonal to complete hexagonal phase. For \({ }0.01 \le \;x\;{ } \le 0.03\), magnetic transition and structural transition couple, leading to first-order magnetostructural transition (MST). With the increment of the Cr concentration, the results of XRD patterns and magnetization versus temperature curves show a reduction of the structural transition temperature (TM). When x = 0.05, structural transition and the magnetic transition decouple, which correspond to a structurally driven first-order structural transition between two large magnetization states and second-order magnetic transition (SOMT), respectively. The large magnetic entropy change \(\left| {\Delta S_{{\text{M}}} } \right|\) and refrigerant capacity (RC) are about 11.58 J kg−1 K−1 with x = 0.01 and 209.21 J kg−1 with x = 0.03 under the applied magnetic field of 5 T, which means that Mn-Co-Cr-Ge alloys have a latent foreground in magnetic refrigeration in the vicinity of room temperature.

The essence of particle motion is stress, and different stress is the reason for different particle motion trajectories. Based on this theory, the magnetite particle stress at six typical representative points of the three-product magnetic separation column is studied, and the relationship between the rising-water flow velocity and the magnetic field strength suitable for the separation of different components is obtained. The friction between the particles and the swirl cone is introduced to explain the reason why the particles with different particle sizes flow to different separation areas at the swirl cone. Analyzing the force on the particles to predict their trajectory, and accurately adjusting the parameters to optimize the magnetic separation process.

In this study, we report the deposition of thin layers of erbium-doped silica onto silicon substrates using the sol–gel method. Deposition was performed by spin coating, followed by drying and heat treatment in the range of 500°C up to 900°C. Different acid catalysts with various erbium doping concentrations were investigated to assess their impact on the film properties including thickness and refractive index. Under the same experimental conditions, the acid catalyst used significantly influenced the thickness and shrinkage of the films, irrespective of the erbium doping concentration. The key factors for this behavior are the viscosity of the sols and the gelation time, which vary tremendously depending on the acid used and the doping concentration. Strong acids were found to produce films with the highest resistance to shrinkage during annealing compared to weak acids. From the elliposometric investigation, the interplay among the doping concentration, pore formation, and annealing was found to affect the refractive index of the synthesized film.

In the current work, the thermal stability of the eutectic regions and precipitation and mechanical behaviour of near eutectic high-entropy alloy is studied. The alloy solidified as FCC and underwent sequential ordering to L12 with order–disorder transition temperature between 700°C and 1000°C. Cooling rate, variation in the concentration boundary layer, thermal gradient and interfacial energy were attributed to define the eutectic morphology (L12 and B2). Thermal exposure resulted in homogeneous precipitation of acicular Al-Ni-rich B2 phase within the proeutectic and irregular eutectic regions. The preferential B2 precipitation within the irregular eutectic regions was attributed to the lower stability and higher lattice strain associated with these regions. The FCC: B2 phase fraction after heat treatment was similar to that of the eutectic alloy. Furthermore, lamellar degradation, globularization and Ostwald ripening of the B2 phase were observed after heat treatment. Lamellar degradation occurred via mechanisms like cylinderization, edge spheroidization, termination migration and boundary splitting. The experimental observations on the phase evolution, stability and order–disorder transformation matched well with the CALPHAD predictions except for the σ phase formation. B2 precipitation during heat treatment enhanced the mechanical behaviour of the alloy. However, the work hardening rate was superior for as-cast alloy.

The ultrasound-assisted electrical discharge is a low-cost and simple-operating method to prepare raw metallic powder for sintering micro-components. The powder size distribution plays a role in the sintering performance and the mechanical property of as-sintered components. Electrical parameters (current, voltage and pulse width) and ultrasonic power govern the size distribution of powder. Based on the iSIGHT platform, the orthogonal experiment is designed to investigate the main effect and interaction effect of four main parameters on the average particle size (D50). It was found that pulse width, current and ultrasonic power have a significant impact on reducing the D50 value. Then, a regression equation was built to achieve the prediction of the D50 value. The multi-physical field sintering method was used to realize the solidification of the as-synthesized metallic powder. When the sintering temperature was 900°C, the nearly full-density (8.61 g/cm3 relative density: 96.73%) micro-cylinder parts were obtained with a high bonding force and good compression resistance due to the mixture of micron and nano-size powder. Nano-sized powder first occurred in low-temperature sintering, and the combination of powder became denser with increasing sintering temperature.

Anticorrosive coatings for corrosion protection on aluminum alloy remain challenges in high protection efficiency and stability with facile design. Here, a stable superhydrophobic film is successfully prepared on 5052 aluminum alloy (AA5052) by electrodeposition to enhance its corrosion resistance in 3.5 wt% NaCl solution. The contact angle reaches 157° at the electrodeposition voltage of 10 V. Electrochemical tests confirm that it can serve as a highly effective and stable coating for corrosion protection with an inhibition efficiency (η) of 99.1%. The charge transfer resistance of the coated Al alloy increases remarkably from 8.955 kΩ cm2 to 366.1 kΩ cm2. Besides, the superhydrophobic surface shows good stability when it is exposed to air and NaCl solution for a long time. After immersion for 12 days in 3.5 wt% NaCl solution, the superhydrophobic coating still exhibits a low corrosion current density of 3.309 × 10-7A/cm2. The synergy effects of the superhydrophobicity and the Ce3+ endow the coating with remarkably enhancing corrosion resistance. This facile strategy can provide new ideas for designing highly effective and stable anti-corrosion coatings on aluminum alloy.