The combination of electrospinning and hot pressing, namely the electrospinning-hot pressing technique (EHPT), is an efficient and convenient method for preparing nanofibrous composite materials with good energy storage performance. The emerging composite membrane prepared by EHPT, which exhibits the advantages of large surface area, controllable morphology, and compact structure, has attracted immense attention. In this paper, the conduction mechanism of composite membranes in thermal and electrical energy storage and the performance enhancement method based on the fabrication process of EHPT are systematically discussed. Moreover, the state-of-the-art applications of composite membranes in these two fields are introduced. In particular, in the field of thermal energy storage, EHPT-prepared membranes have longitudinal and transverse nanofibers, which generate unique thermal conductivity pathways; also, these nanofibers offer enough space for the filling of functional materials. Moreover, EHPT-prepared membranes are beneficial in thermal management systems, building energy conservation, and electrical energy storage, e.g., improving the electrochemical properties of the separators as well as their mechanical and thermal stability. The application of electrospinning-hot pressing membranes on capacitors, lithium-ion batteries (LIBs), fuel cells, sodium-ion batteries (SIBs), and hydrogen bromine flow batteries (HBFBs) still requires examination. In the future, EHPT is expected to make the field more exciting through its own technological breakthroughs or be combined with other technologies to produce intelligent materials.
The macroscopic flow behavior and rheological properties of cemented paste backfill (CPB) are highly impacted by the inherent structure of the paste matrix. In this study, the effects of shear-induced forces and proportioning parameters on the microstructure of fresh CPB were studied. The size evolution and distribution of floc/agglomerate/particles of paste were monitored by focused beam reflection measuring (FBRM) technique, and the influencing factors of aggregation and breakage kinetics of CPB were discussed. The results indicate that influenced by both internal and external factors, the paste kinetics evolution covers the dynamic phase and the stable phase. Increasing the mass content or the cement–tailings ratio can accelerate aggregation kinetics, which is advantageous for the rise of average floc size. Besides, the admixture and high shear can improve breaking kinetics, which is beneficial to reduce the average floc size. The chord length resembles a normal distribution somewhat, with a peak value of approximate 20 µm. The particle disaggregation constant (k 2) is positively correlated with the agitation rate, and k 2 is five orders of magnitude greater than the particle aggregation constant (k 1). The kinetics model depicts the evolution law of particles over time quantitatively and provides a theoretical foundation for the micromechanics of complicated rheological behavior of paste.
As a cornerstone of the national economy, the iron and steel industry generates a significant amount of sintering dust containing both valuable lead resources and deleterious elements. Flotation is a promising technique for lead recovery from sintering dust, but efficient separation from Fe2O3 is still challenging. This study investigated the cooperative effect of sodium lauryl sulfate (SLS, C12H25SO4Na) and sodium pyrophosphate (SPP, Na4P2O7) on the selective flotation of lead oxide minerals (PbOHCl and PbSO4) from hematite (Fe2O3). Optimal flotation conditions were first identified, resulting in high recovery of lead oxide minerals while inhibiting Fe2O3 flotation. Zeta potential measurements, Fourier transform infrared spectroscopy (FT-IR) analysis, adsorption capacity analysis, and X-ray photoelectron spectroscopy (XPS) studies offer insights into the adsorption behaviors of the reagents on mineral surfaces, revealing strong adsorption of SLS on PbOHCl and PbSO4 surfaces and remarkable adsorption of SPP on Fe2O3. The proposed model of reagent adsorption on mineral surfaces illustrates the selective adsorption behavior, highlighting the pivotal role of reagent adsorption in the separation process. These findings contribute to the efficient and environmentally friendly utilization of iron ore sintering dust for lead recovery, paving the way for sustainable resource management in the iron and steel industry.
Inhibitors are important for flotation separation of quartz and feldspar. In this study, a novel combined inhibitor was used to separate quartz and feldspar in near-neutral pulp. Selective inhibition of the combined inhibitor was assessed by micro-flotation experiments. And a series of detection methods were used to detect differences in the surface properties of feldspars and quartz after flotation reagents and put forward the synergistic strengthening mechanism. The outcomes were pointed out that pre-mixing combined inhibitors were more effective than the addition of Ca2+ and SS in sequence under the optimal proportion of 1:5. A concentrate from artificial mixed minerals that was characterized by a high quartz grade and a high recovery was acquired, and was found to be 90.70wt% and 83.70%, respectively. It was demonstrated that the combined inhibitor selectively prevented the action of the collector and feldspar from Fourier-transform infrared (FT-IR) and adsorption capacity tests. The results of X-ray photoelectron spectroscopy (XPS) indicated that Ca2+ directly interacts with the surface of quartz to increase the adsorption of collectors. In contrast, the chemistry property of Al on the feldspar surface was altered by combined inhibitor due to Na+ and Ca2+ taking the place of K+, resulting in the composite inhibitor forms a hydrophilic structure, which prevents the adsorption of the collector on the surface of feldspar by interacting with the Al active site. The combination of Ca2+ and SS synergically strengthens the difference of collecting property between quartz and feldspar by collector, thus achieving the effect of efficient separation. A new strategy for flotation to separate quartz from feldspar in near-neutral pulp was provided.
The toxic cyanides in cyanide residues produced from cyanidation process for gold extraction are harmful to the environment. Pyrite is one of the main minerals existing in cyanide residues. In this work, the interaction of cyanide with pyrite and the decyanation of pyrite cyanide residue were analyzed. Results revealed that high pH value, high cyanide concentration, and high pyrite dosage promoted the interaction of cyanide with pyrite. The cyanidation of pyrite was pseudo-second-order with respect to cyanide. The decyanation of pyrite cyanide residue by Na2SO3/air oxidation was performed. The cyanide removal efficiency was 83.9% after 1 h of reaction time under the optimal conditions of pH value of 11.2, dosage of 22 mg·g−1, and air flow rate of 1.46 L·min−1. X-ray photoelectron spectroscopy analysis of the pyrite samples showed the formation of Fe(III) and FeSO4 during the cyanidation process. The cyanide that adsorbed on the pyrite surface after cyanidation mainly existed in the forms of free cyanide (CN−) and ferrocyanide (Fe(CN)6 4−), which were effectively removed by Na2SO3/air oxidation. During the decyanation process, air intake promoted pyrite oxidation and weakened cyanide adsorption on the pyrite surface. This study has practical significance for gold enterprises aiming to mitigate the environmental impact related to cyanide residues.
Slurry electrolysis (SE), as a hydrometallurgical process, has the characteristic of a multitank series connection, which leads to various stirring conditions and a complex solid suspension state. The computational fluid dynamics (CFD), which requires high computing resources, and a combination with machine learning was proposed to construct a rapid prediction model for the liquid flow and solid concentration fields in a SE tank. Through scientific selection of calculation samples via orthogonal experiments, a comprehensive dataset covering a wide range of conditions was established while effectively reducing the number of simulations and providing reasonable weights for each factor. Then, a prediction model of the SE tank was constructed using the K-nearest neighbor algorithm. The results show that with the increase in levels of orthogonal experiments, the prediction accuracy of the model improved remarkably. The model established with four factors and nine levels can accurately predict the flow and concentration fields, and the regression coefficients of average velocity and solid concentration were 0.926 and 0.937, respectively. Compared with traditional CFD, the response time of field information prediction in this model was reduced from 75 h to 20 s, which solves the problem of serious lag in CFD applied alone to actual production and meets real-time production control requirements.
The efficient recycling of vanadium from converter vanadium-bearing slag is highly significant for sustainable development and circular economy. The key to developing novel processes and improving traditional routes lies in the thermodynamic data. In this study, the equilibrium phase relations for the Fe2O3-TiO2-V2O5 system at 1200°C in air were investigated using a high-temperature equilibrium-quenching technique, followed by analysis using scanning electron microscopy-energy dispersive X-ray spectrometer and X-ray photoelectron spectroscopy. One liquid-phase region, two two-phase regions (liquid-rutile and liquid-ferropseudobrookite), and one three-phase region (liquid-rutile-ferropseudobrookite) were determined. The variation in the TiO2 and V2O5 contents with the Fe2O3 content was examined for rutile and ferropseudobrookite solid solutions. However, on further comparison with the predictions of FactSage 8.1, significant discrepancies were identified, highlighting that greater attention must be paid to updating the current thermodynamic database related to vanadium-bearing slag systems.
In the present work, plastic deformation mechanisms were initially tailored by adjusting the deformation temperature in the range of 0 to 200°C in AISI 304L austenitic stainless steel, aiming to optimize the strength-ductility synergy. It was shown that the combined twinning-induced plasticity (TWIP)/transformation-induced plasticity (TRIP) effects and a wider strain range for the TRIP effect up to higher strains by adjusting the deformation temperature are good strategies to improve the strength-ductility synergy of this metastable stainless steel. In this regard, by consideration of the observed temperature-dependency of plastic deformation, the controlled sequence of TWIP and TRIP effects for archiving superior strength-ductility trade-off was intended by the pre-designed temperature jump tensile tests. Accordingly, the optimum tensile toughness of 846 MJ/m3 and total elongation to 133% were obtained by this strategy via exploiting the advantages of the TWIP effect at 100°C and the TRIP effect at 25°C at the later stages of the straining. Consequently, a deformation-temperature-transformation (DTT) diagram was developed for this metastable alloy. Moreover, based on work-hardening analysis, it was found that the main phenomenon constraining further improvement in the ductility and strengthening was the yielding of the deformation-induced α′-martensite.
The structure of the oxide film on FGH96 alloy powders significantly influences the mechanical properties of superalloys. In this study, FGH96 alloy powders with various oxygen contents were investigated using high-resolution transmission electron microscopy and atomic probe technology to elucidate the structure evolution of the oxide film. Energy dispersive spectrometer analysis revealed the presence of two distinct components in the oxide film of the alloy powders: amorphous oxide layer covering the γ matrix and amorphous oxide particles above the carbide. The alloying elements within the oxide layer showed a laminated distribution, with Ni, Co, Cr, and Al/Ti, which was attributed to the decreasing oxygen equilibrium pressure as oxygen diffused from the surface into the γ matrix. On the other hand, Ti enrichment was observed in the oxide particles caused by the oxidation and decomposition of the carbide phase. Comparative analysis of the oxide film with oxygen contents of 140, 280, and 340 ppm showed similar element distributions, while the thickness of the oxide film varies approximately at 9, 14, and 30 nm, respectively. These findings provide valuable insights into the structural analysis of the oxide film on FGH96 alloy powders.
To enhance the long-term corrosion resistance of the plasma electrolytic oxidation (PEO) coating on the magnesium (Mg) alloy, an inorganic salt combined with corrosion inhibitors was used for posttreatment of the coating. In this study, the corrosion performance of PEO-coated AM50 Mg was significantly improved by loading sodium lauryl sulfonate (SDS) and sodium dodecyl benzene sulfonate into Ba(NO3)2 post-sealing solutions. Scanning electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, Fourier transform infrared spectrometer, and ultraviolet–visible analyses showed that the inhibitors enhanced the incorporation of BaO2 into PEO coatings. Electrochemical impedance showed that post-sealing in Ba(NO3)2/SDS treatment enhanced corrosion resistance by three orders of magnitude. The total impedance value remained at 926 Ω·cm2 after immersing in a 0.5wt% NaCl solution for 768 h. A salt spray test for 40 days did not show any obvious region of corrosion, proving excellent post-sealing by Ba(NO3)2/SDS treatment. The corrosion resistance of the coating was enhanced through the synergistic effect of BaO2 pore sealing and SDS adsorption.
Magnesium (Mg) alloys are gaining great consideration as body implant materials due to their high biodegradability and biocompatibility. However, they suffer from low corrosion resistance and antibacterial activity. In this research, semi-powder metallurgy followed by hot extrusion was utilized to produce the magnesium oxide@graphene nanosheets/magnesium (MgO@GNS/Mg) composite to improve mechanical, corrosion and cytocompatibility characteristics. Investigations have revealed that the incorporation of MgO@GNS nanohybrids into Mg-based composite enhanced microhardness and compressive strength. In vitro, osteoblast cell culture tests show that using MgO@GNS nanohybrid fillers enhances osteoblast adhesion and apatite mineralization. The presence of MgO@GNS nanoparticles in the composites decreased the opening defects, micro-cracks and micro-pores of the composites thus preventing the penetration of the corrosive solution into the matrix. Studies demonstrated that the MgO@GNS/Mg composite possesses excellent antibacterial properties because of the combination of the release of MgO and physical damage to bacterium membranes caused by the sharp edges of graphene nanosheets that can effectively damage the cell wall thereby facilitating penetration into the bacterial lipid bilayer. Therefore, the MgO@GNS/Mg composite with high mechanical strength, antibacterial activity and corrosion resistance is considered to be a promising material for load-bearing implant applications.
Resin-bonded Al-SiC composite was sintered at 1100, 1300, and 1500°C in the air, the oxidation mechanism was investigated. The reaction models were also established. The oxidation resistance of the Al-SiC composite was significantly enhanced with temperature increase. SiC in the exterior of the composite was partially oxidized slightly, while the transformation of metastable Al4C3 to stable Al4SiC4 existed in the interior. At 1100°C, Al in the interior reacted with residual C to form Al4C3. With increasing to 1300°C, high temperature and low oxygen partial pressure lead to active oxidation of SiC, and internal gas composition transforms to Al2O(g) + CO(g) + SiO(g) as the reaction proceeds. After Al4C3 is formed, CO(g) and SiO(g) are continuously deposited on its surface, transforming to Al4SiC4. At 1500°C, a dense layer consisting of SiC and Al4SiC4 whiskers is formed which cuts off the diffusion channel of oxygen. The active oxidation of SiC is accelerated, enabling more gas to participate in the synthesis of Al4SiC4, eventually forming hexagonal lamellar Al4SiC4 with mutual accumulation between SiC particles. Introducing Al enhances the oxidation resistance of SiC. In addition, the in situ generated non-oxide is uniformly dispersed on a micro-scale and bonds SiC stably.
To enhance the Young’s modulus (E) and strength of titanium alloys, we designed titanium matrix composites with interconnected microstructure based on the Hashin-Shtrikman theory. According to the results, the in-situ reaction yielded an interconnected microstructure composed of Ti2C particles when the Ti2C content reached 50vol%. With widths of 10 and 230 nm, the intraparticle Ti lamellae in the prepared composite exhibited a bimodal size distribution due to precipitation and the unreacted Ti phase within the grown Ti2C particles. The composites with interconnected microstructure attained superior properties, including E of 174.3 GPa and ultimate flexural strength of 1014 GPa. Compared with that of pure Ti, the E of the composite was increased by 55% due to the high Ti2C content and interconnected microstructure. The outstanding strength resulted from the strong interfacial bonding, load-bearing capacity of interconnected Ti2C particles, and bimodal intraparticle Ti lamellae, which minimized the average crack driving force. Interrupted flexural tests revealed preferential crack initiation along the {001} cleavage plane and grain boundary of Ti2C in the region with the highest tensile stress. In addition, the propagation can be efficiently inhibited by interparticle Ti grains, which prevented the brittle fracture of the composites.
To explore highly active and thermomechanical stable air electrodes for intermediate-temperature solid oxide fuel cells (IT-SOFCs), 10mol% Ta5+ doped in the B site of strontium ferrite perovskite oxide (SrTa0.1Fe0.9O3−δ, STF) is investigated and optimized. The effects of Ta5+ doping on structure, transition metal reduction, oxygen nonstoichiometry, thermal expansion, and electrical performance are evaluated systematically. Via 10mol% Ta5+ doping, the thermal expansion coefficient (TEC) decreased from 34.1 × 10−6 (SrFeO3−δ) to 14.6 × 10−6 K−1 (STF), which is near the TEC of electrolyte (13.3 × 10−6 K−1 for Sm0.2Ce0.8O1.9, SDC), indicates excellent thermomechanical compatibility. At 550–750°C, STF shows superior oxygen vacancy concentrations (0.262 to 0.331), which is critical in the oxygen-reduction reaction (ORR). Oxygen temperature-programmed desorption (O2-TPD) indicated the thermal reduction onset temperature of iron ion is around 420°C, which matched well with the inflection points on the thermos-gravimetric analysis and electrical conductivity curves. At 600°C, the STF electrode shows area-specific resistance (ASR) of 0.152 Ω·cm2 and peak power density (PPD) of 749 mW·cm−2. ORR activity of STF was further improved by introducing 30wt% Sm0.2Ce0.8O1.9 (SDC) powder, STF + SDC composite cathode achieving outstanding ASR value of 0.115 Ω·cm2 at 600°C, even comparable with benchmark cobalt-containing cathode, Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF). Distribution of relaxation time (DRT) analysis revealed that the oxygen surface exchange and bulk diffusion were improved by forming a composite cathode. At 650°C, STF + SDC composite cathode achieving an outstanding PPD of 1117 mW·cm−2. The excellent results suggest that STF and STF + SDC are promising air electrodes for IT-SOFCs.
A novel method was developed to enhance the utilization rate of steel slag (SS). Through treatment of SS with phosphoric acid and aminopropyl triethoxysilane (KH550), we obtained modified SS (MSS), which was used to prepare MSS/wood-plastic composites (MSS/WPCs) by replacing talcum powder (TP). The composites were fabricated through melting blending and hot pressing. Their mechanical and combustion properties, which comprise heat release, smoke release, and thermal stability, were systematically investigated. MSS can improve the mechanical strength of the composites through grafting reactions between wood powder and thermoplastics. Notably, MSS/WPC#50 (16wt% MSS) with an MSS-to-TP mass ratio of 1:1 exhibited optimal comprehensive performance. Compared with those of WPC#0 without MSS, the tensile, flexural, and impact strengths of MSS/WPC#50 were increased by 18.5%, 12.8%, and 18.0%, respectively. Moreover, the MSS/WPC#50 sample achieved the highest limited oxygen index of 22.5%, the highest vertical burning rating at the V-1 level, and the lowest horizontal burning rate at 44.2 mm/min. The formation of a dense and stable char layer led to improved thermal stability and a considerable reduction in heat and smoke releases of MSS/WPC#50. However, the partial replacement of TP with MSS slightly compromised the mechanical and flame-retardant properties, possibly due to the weak grafting caused by SS powder agglomeration. These findings suggest the suitability of MSS/WPCs for high-value-added applications as decorative panels indoors or outdoors.