The dendrite growth behaviours of high-strength steel during slab continuous casting with travelling-wave magnetic field was studied in this paper. The morphology of solidification structure and composition distribution were analysed in detail. The results showed that the columnar crystals could deflect and break when travelling-wave magnetic field worked with low current intensity. With the increase of current intensity, the secondary dendrite arm spacing and solute permeability decreased, and the columnar crystal transformed to equiaxed crystal. Electromagnetic force caused by travelling-wave magnetic field changed the temperature gradient and velocity magnitude, and promoted the breaking and fusing of dendrites. The order of dendrite compactness and composition uniformity from good to bad was columnar-to-equiaxed transition (high current intensity), columnar crystal zone (low current intensity), columnar-to-equiaxed transition (low current intensity) and equiaxed crystal zone (high current intensity). Additionally, combined with the verified numerical simulation results, as well as the boundary layer theory of solidification front and the dendrite breaking-fusing model, the dendrite deflection mechanism and growth process are revealed. When thermal stress is not considered and there is no obvious narrow segment in dendrite, the velocity magnitude on the solidification front of liquid steel need to reach 0.041 m/s before dendrites can break.

Satellited CoNiCrAlY-Al₂O₃ feedstocks with 2, 4, and 6 wt.% of oxide nanoparticles and pure CoNiCrAlY powder were deposited by the HVOF process on Inconel738 superalloy substrate. Oxidation test was done at 1050 ℃ for 5, 50, 100, 150, 200, and 400 h. Microstructure and phase composition of powders and coatings were characterized by scanning electron microscopy and X-ray diffraction, respectively. The bonding strength of the coatings was also evaluated. The results proved that with the increase in the percentage of nanoparticles (from 2 to 6 wt.%), the amount of porosity (from 1 to 4.7 vol.%), unmelted particles, and the roughness of the coating (from 4.8 to 8.8 µm) increased and the bonding strength decreased (from 71 to 48 MPa). The thickness of the TGO layer of pure coating and composite coatings (2, 4, and 6%) after 400 h oxidation was measured as 6.5, 5.5, 7.6, and 8.1 µm, respectively. The CoNiCrAlY-2% Al₂O₃ coating showed the highest oxidation resistance due to the well-dispersed nanoparticles. The CoNiCrAlY-6% Al₂O₃ coating had the lowest oxidation resistance caused by its rough surface morphology and porous microstructure.

Goethitic bauxite is a widely used raw materials in the alumina industry. Clarifying the effect of Ti- and Si-containing minerals on goethite transformation in the Bayer digestion process is an essential prerequisite for efficiently utilizing the Fe- and Al-containing minerals in goethitic bauxite. In this work, the interactions between anatase or kaolinite with goethite under various Bayer digestion process were investigated using X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscope, scanning electron microscope. The results show that anatase and kaolinite hindered the transformation of goethite. Anatase caused more significant effects by producing a dense sodium titanate layer on the goethite surface after reacting with sodium aluminate solution. While for the case of kaolinite, a loose desilication product adhered to the goethite surface due to the reaction of kaolinite with sodium aluminate solution. Adding the reductants (hydrazine hydrate) could eliminate the retard effect by inducing the transformation of goethite to magnetite, in which titanium is embedded in the magnetite lattice to form Ti-containing magnetite. In contrast, the weakening of the interaction between magnetite and DSP further reduced the influence of kaolinite. As a validation, a reductive Bayer method achieved the transformation of goethite in goethitic bauxite with a 98.87% relative alumina digestion rate. The obtained red mud with a 72.99wt% Fe₂O₃ content could be further utilized in the steel industry. This work provided a clear understanding of the transformative effects of Ti- and Si-containing minerals to iron minerals transformation and helped with the comprehensive use of iron and aluminum in goethitic bauxite by the reductive Bayer method.

Sepiolite (ST) was used as a supporting matrix in compiste phase change materials (PCMs) due to its unique microstructure, good thermal stability and other raw material advantages. In this paper, microwave acid treatment were innovatively used in the modification of sepiolite. The modified sepiolite (ST_m) obtained in different hydrochloric acid concentration (0.25 mol L^-1, 0.5 mol L^-1, 0.75 mol L^-1,and 1.0 mol L^-1) treament were added to stearic acid (SA) via vacuum impregnation method. The thermophysical properties of the composites were changed by varying the hydrochloric acid concentration. The SA-ST_m0.5 obtained by microwave acid treatment at 0.5 mol L^-1 hydrochloric acid concentration showed a higher loading capacity (82.63%) than other composites according to the DSC analysis. The melting and freezing enthalpies of SA-ST_m0.5 were of 152.30 J g^-1 and 148.90 J g^-1, respectively. The thermal conductivity of SA-ST_m0.5 was as high as 1.52 times that of pure SA. In addition, the crystal structure, surface morphology and microporous structure of modified sepiolite were studied, and the mechanism of SA-ST_m0.5 performance enhancement was further revealed by BET analysis. Leakage experiment showed that SA-ST_m0.5 have good morphological stability. These results demostrate that SA-ST_m0.5 have potential application in thermal energy storage.

The one-ladle technology requires higher ironmaking and steelmaking interface technology. The scheduling of the hot metal ladle in the steel plant determines the overall operation efficiency of the interface. Considering the strong uncertainties of the real-world production environments, the paper studies the dynamic scheduling problem of hot metal ladles and develops a data-driven based three-layer approach to cope with the problem. In the approach, a dynamic scheduling optimization model of the hot metal ladle operation with the minimum average turnover time as the optimization objective is constructed. Further, the intelligent perception of industrial scenes and autonomous identification of disturbances, the adaptive configuration of dynamic scheduling strategies, and real-time adjustment of schedules can be realized. To be specific, the upper layer generates a demand-oriented pre-scheduling scheme for hot metal ladles. The middle layer adaptively adjusts it to obtain an executable schedule according to the actual supply-demand relationship. In the lower layer, three types of dynamic scheduling strategies are designed from the characteristics of the dynamic disturbance in the model: real-time flexible fine-tuning, local machine adjustment and global rescheduling. The case test using 24-hour production data of a certain day during the system operation of a steel plant shows that the method and system can effectively reduce the hot metal ladle operation time and its fluctuation, and improve the stability of the ironmaking and steelmaking interface production rhythm. The data-driven dynamic scheduling strategy is feasible and effective, which shows that the method can obviously improve the operation efficiency of hot metal ladles.

Metal corrosion brings billions of dollars of economic losses each year. As a smart and new energy harvesting device, triboelectric nanogenerators (TENGs) are able to convert almost all mechanical energies into electricity, leading to great prospects in metal corrosion prevention, cathodic protection, etc. In this work, flexible TENGs were designed utilizing the energy harvested by flexible PDMS films with ZrB₂ nanoparticles, dielectric constant was effectively improved by ZrB₂, the open-circuit voltage and short-circuit current are 264 V and 22.9 μA, respectively, and the power density of the TENG reaches 6 W/m². Furthermore, a self-powered anti-corrosion system is designed by the rectifier circuit integrated with the TENGs, and the open circuit potential (OCP) and Tafel curves show that the system has excellent anti-corrosion effect on carbon steel, indicating that the system has broad application prospects in metal cultural relics, ocean engineering, industry and so on.

Seawater splitting is a prospective approach to yield renewable and sustainable hydrogen energy. Currently, complex preparation process and poor repeatability are generally considered to be an insuperable impediment to promote the large-scale production and application of electrocatalysts. Corrosion engineering, avoiding use of the intricate instruments, is an intriguing strategy to reduce the cost and present great potential for electrodes with catalytic performance. In this work, we propose an anode consisting of quinary AlCoCrFeNi layered double hydroxides uniformly decorated on AlCoCrFeNi high entropy alloy via a one-step corrosion engineering method, which directly serves as an extremely active catalyst for boosting oxygen evolution reaction in alkaline seawater. Notably, the best-performing catalyst exhibit the OER activity with overpotential values of 272.3 mV and 332 mV to achieve the current densities of 10 mA cm^-2 and 100 mA cm^-2, respectively. Deeply, the failure mechanism of obtained catalyst was found for advancing the development of multi-component catalyst.

The effect of Li₂O instead of B₂O₃ on the viscosity and the melting temperature of the low-reactive mold flux was investigated. The melt structure and precipitation of the crystalline phase were studied using the Raman spectrum and X-ray diffraction to better understand the evolution of viscosity. The viscosity of the mold flux with 2wt% Li₂O and 6wt% B₂O₃ reached the minimum value of 0.07 Pa·s. The break temperature and melting temperature showed a similar trend with the viscosity. With the increase of Li₂O content in the mold flux from 0wt% to 6wt%, the degree of polymerization of aluminate and aluminosilicate network structure increased due to the increasing Li+ released by Li₂O. The addition of Li₂O preferred to associate with Al³⁺ as a charge compensator. The precipitation of the LiAlO₂ crystalline phase led to an increase in mold flux viscosity. Therefore, the content of Li₂O should be controlled below 2wt% to avoid the precipitation of LiAlO₂, which was harmful to the continuous casting of high-aluminum steels.  

Mold flux serves a crucial metallurgical function of absorbing inclusions, which has a direct impact on the smooth of casting process and the casted slab quality. In this study, the dissolution behavior and mechanism of TiO₂ and TiN inclusions in molten CaO-SiO₂-B₂O₃ based fluorine-free mold flux were explored by in-situ Single Hot Thermocouple Technology combined with X-ray Photoelectron Spectroscopy. The results showed that the rutile TiO₂ inclusion was effectively dissolved by the molten slag within 76 s, which the original [TiO₆] octahedral structure was destroyed and converted to the network former [TiO₄] tetrahedral. However, the dissolution rate of TiN inclusion was significantly lower than that of the TiO₂ inclusion. This was primarily due to that, during the dissolution process of TiN inclusion, the TiN particle needed to be first oxidized and then dissolved in the molten slag into [TiO₄] tetrahedral and [TiO₆] octahedral structures, accompanied by the generation of a large amount of N₂ gas. Besides, CaTiO₃ crystals tended to nucleate and grow on the surface of the bubbles with sufficient [TiO₆] octahedral and Ca²⁺ ions, resulting in the molten slag to be in a solid-liquid mixed state eventually.

The mechanical properties of cemented paste backfill (CPB) determine its control effect on the goaf roof. In this study, the mechanical strength of polymer-modified cemented paste backfill (PCPB) samples was tested by uniaxial compression tests, and the failure characteristics of PCPB under the compression were analyzed. At the same time, acoustic emission (AE) technology was used to monitor and record the cracking process of the PCPB sample with a curing age of 28 d in real time, and two AE indexes methods (RA and AF values) were used to classify the failure modes of samples under different loading processes. The results show that waterborne epoxy resin can significantly enhance the mechanical strength of PCPB samples (when the PU-C ratio is 0.25, the strength of PCPB samples with a curing age of 28 d is increased by 102.6%); with the increase of polymer content, the mechanical strength of PCPB samples is improved significantly, and the increase of mechanical strength is the most obvious in the early and middle period of curing. Under uniaxial load, the macro cracks of PCPB samples are mostly generated along the axial direction, the main crack runs through the sample, and a large number of small cracks are distributed around the main crack. The AE response of PCPB samples during the whole loading process can be divided into four periods: quiet period, slow growth period, rapid growth period and remission period, which are synchronized with the micro-pore compaction stage, elastic deformation stage, plastic deformation stage and failure instability stage of the sample’s stress-strain curve. The AE events are mainly concentrated in the plastic deformation stage; both shear failure and tensile failure occur in the above four stages, while tensile failure is dominant for PCPB samples. The results of this study can improve the safety of coal pillar recovery in pillar goaf.

In this work, a polymer-derived ZrC ceramic with excellent electromagnetic interference (EMI) shielding performance was developed to meet the requirement in ultra-high temperature. Thermal decomposition process of ZrC ceramic organic precursor was studied, and the evolution of phase composition, microstructure, and EMI shielding performance was revealed. The carbothermal reduction reaction begins to occur at 1300℃, and the transformation from ZrO₂ to ZrC was completely at 1700℃. With the increase of annealing temperature, the tetragonal zirconia (t-ZrO₂) gradually transforms into monoclinic zirconia (m-ZrO₂), and the transformation is complete at annealing temperature of 1500℃ due to the consumption of large amount of carbon phase. The average total shielding effectiveness was 11.63, 22.67, 22.91, 22.81 and 34.73 dB when the polymer-derived ZrC (PDC-ZrC) was annealed at 900, 1100, 1300, 1500 and 1700℃, respectively. In the thermal decomposition process, the graphitization degree and phase distribution of free carbon plays the dominant role to affect the shielding performance. The typical core-shell structure, composed of carbon and ZrC, can be formed at the annealing temperature of 1700℃, resulting in the excellent shielding performance.

Novel g-C₃N₄ nanosheet/Bi₅O₇Br/NH₂-MIL-88B(Fe) photocatalysts (denoted as GCN-NSh/Bi₅O₇Br/Fe-MOF) with a double S-scheme heterojunctions were synthesized by a facile solvothermal route. The resultant materials were examined by XPS, XRD, SEM, TEM, HRTEM, PL, EDX, FT-IR, UV-vis DRS, photocurrent density, EIS, and BET analyses. After integration of Fe-MOF with GCN-NSh/Bi₅O₇Br, the removal constant of tetracycline over the optimal GCN-NSh/Bi₅O₇Br/Fe-MOF (15%) nanocomposite was promoted 33-times in comparison with the pristine GCN. Furthermore, compared to the pure GCN, the GCN-NSh/Bi₅O₇Br/Fe-MOF (15%) nanocomposite showed supreme photoactivity to azithromycin, metronidazole, and cephalexin removal, which were 36.4, 20.2, and 14.6 times as high as the GCN, respectively. The radical quenching tests showed that ⦁O⁻₂ and h⁺ mainly contributed in the elimination reaction. In addition, the nanocomposite had excellent activity after four successive cycles. According to the developed n-n heterojunctions amongst n-GCN-NSh, n-Bi₅O₇Br, and n-Fe-MOF semiconductors, a double S-scheme charge transfer mechanism was proposed for destruction of the selected antibiotics.

Tetragonal barium titanate was synthesized from barium hydroxide octahydrate and titanium tetrachloride through a simple one-step hydrothermal method. The effect of different solvents on the crystal structure and morphology of barium titanate nanoparticles in the hydrothermal process was investigated. Except for ethylene glycol/water solvent, impurity-free barium titanate is synthesized in pure water, methanol/water, ethanol/water and isopropyl alcohol/water mixed solvents. Compared with other alcohols, ethanol is favorable to the formation of tetragonal structure. In addition, characterization studies confirm that particles synthesized in methanol/water, ethanol/water, isopropyl alcohol/water mixed solvents are smaller in size than those in pure water. In the case of alcohol-containing solvents, the particle size decreases in the order of isopropanol, ethanol and methanol. Among all the media employed, ethanol/water is the optimum reaction media for barium titanate in terms of high tetragonality (c/a=1.0088) and small average particle size (82 nm), which has great potential for practical application in multilayer ceramic capacitors.

Performance degradation of the solid oxide fuel cell (SOFC) shortens the cell life in practical applications. Revealing the degradation mechanism is crucial for continuous improvement in cell durability. In this work, the effects of cell operating conditions on the terminal voltage and anode microstructure of the Ni-YSZ (yttria-stabilized zirconia) anode-supported single cell are investigated. The microstructure of the anode active area near the electrolyte is characterized by laser optical microscope and focused ion beam-scanning electron microscopy. Ni depletion at the anode/electrolyte interface region is observed after the 100 h discharge tests. In addition, the long-term stability of the single cell is evaluated at 700°C for 3000 h. After the initial decline, the anode-supported single cell exhibits a good durability with a voltage decay rate of 0.72%/kh and an electrode polarization resistance decay rate of 0.17%/kh. The main performance loss of the cells comes from the initial degradation.

In the past few decades, microbubble flotation has been widely studied in the separation and beneficiation of fine minerals. Compared with conventional flotation, microbubble flotation has obvious advantages such as high grade and recovery, and low consumption of flotation reagents. Hereby, we systematically review the latest advances and research progress in the flotation of fine mineral particles by microbubbles. In general, microbubbles are characteristic of small bubble size, large specific surface area, high surface energy, good selectivity, and are easy to attach to the surface of hydrophobic particles or large bubbles, greatly reducing the detaching probability of particles from bubbles. Microbubbles can be prepared by pressurized aeration and dissolved air (PADA), electrolysis, ultrasonic cavitation, photocatalysis, solvent exchange, temperature difference method (TDM), venturi tube and membrane method, etc. Correspondingly, equipment for fine particle flotation is categorized as microbubble release flotation machine, centrifugal flotation column, packed flotation column, and magnetic flotation machine, etc. In practice, microbubble flotation has been widely studied in the beneficiation of ultrafine coals, metallic minerals, non-metallic minerals, and exhibited superiority than the conventional flotation machine. Mechanisms underpinning the promotion of fine particle flotation by nanobubbles include the agglomeration of fine particles, the high stability of nanobubbles in aqueous solution, the enhancement of particle hydrophobicity and flotation dynamics.

Due to the depletion of wolframite resources, the development focus of tungsten resources has gradually shifted to scheelite, making the recycling of scheelite resources a hot research topic. Researchers are particularly concerned about the separation of scheelite from calcium-bearing minerals. Because calcium-bearing gangue minerals associated with scheelite (such as apatite, fluorite, and calcite) have similar surface physicochemical properties to scheelite in pulp, it is impossible to separate scheelite from them using oleate collectors selectively. Researchers have made significant progress in recent years by using depressants as a breakthrough in their research. The development status, mechanism, reagent combination, and application of depressants in calcium-containing minerals were reviewed in this research. Their benefits and drawbacks were objectively assessed to offer a theoretical foundation for the future development of scheelite flotation depressants.

The activation of CO on iron-based materials is a key elementary reaction for many chemical processes. In this work, we investigate CO adsorption and dissociation on a series of Fe, Fe₃C, Fe₅C₂, and Fe₂C catalysts through density functional theory calculations. We detect dramatically different performances for CO adsorption and activation on diverse surfaces and sites. The activation of CO is dependent not only on the local coordination of the molecule to the surface but also the bulk phase of the underlying catalyst. The different local bonding environment affects the bulk properties leading to varying interactions between the adsorbed CO and the surface, thus yielding different activation levels of the C-O bond. We also examine the prediction of CO adsorption upon different types of Fe-based catalysts by performing machine learning through linear regression models. We combine the features originating from both surfaces and bulk phases to enhance the prediction of the activation energies. Eight different linear regressions utilizing feature engineering of polynomial representations were performed. Among them, a ridge linear regression with 2nd-degree polynomial feature generation predicted the best CO activation energy with a mean absolute error of 0.269 eV.

The synthesis of oxygen vacancies (OVs) modified TiO₂ under mild conditions is attractive. In this work, OVs were easily introduced in TiO₂ lattice during the hydrothermal doping process of trivalent iron ions. Theoretical calculations based on a novel charge-compensation structure model were employed with experimental methods to reveal the intrinsic photocatalytic mechanisms of Fe doped TiO₂ (Fe-TiO₂). The OVs’ formation energy in Fe-TiO₂ (1.12 eV) was only 23.6% of that in TiO₂ (4.74 eV), explaining why Fe³⁺ doping could introduce OVs concentration in TiO₂ lattice. The calculation results also indicated that impurity states introduced by Fe³⁺ and OVs enhanced the light absorption activity of TiO₂. Additionally, the charge carriers’ transport was investigated by carriers’ lifetime and relative mass. The carriers’ lifetime of Fe-TiO₂ (4.00 ns, 4.10 ns and 3.34 ns for 1%, 2% and 3% doping concentration, respectively) was longer than that of undoped TiO₂ (3.22 ns), indicating Fe³⁺ and OVs could promote the separation of charge carriers, which can be attributed to the bigger relative effective mass of electrons and holes. Herein, the Fe-TiO₂ has higher photocatalytic indoor NO removal activity compared with other photocatalysts because it has strong light absorption activity and high carriers’ separation efficiency.

Wall slip is a microscopic phenomenon of cemented paste backfill (CPB) slurry near the pipe wall, which has an important influence on the form of slurry pipe transport flow and velocity distribution. Directly probe the wall slip characteristics by conventional experimental methods is difficult. This paper built a non-contact experimental platform for monitoring the microscopic slip layer of CPB pipeline transport independently based on particle image velocimetry (PIV), analyzed the effects of slurry temperature, pipe diameter, solid concentration and slurry flow on the wall slip velocity of CPB slurry, which refined the theory of the effect of wall slip characteristics on pipeline transport. The results showed that CPB slurry had an extensive slip layer at the pipe wall, with significant wall slip. High slurry temperature improved the degree of particle Brownian motion within the slurry and enhances the wall-slip effect. Increasing pipe diameter was not conducive to the formation of the slurry slip layer and led to a transition in the CPB slurry flow pattern. The increase in solid concentration increased the interlayer shear effect of CPB slurry flow and the slip velocity. The slip velocity value increased from 0.025 m·s^-1 to 0.056 m·s^-1 when the solids content improved from 55wt% to 65wt%. when slurry flow increased, CPB slurry flocculation structure changed, which affected the slip velocity, and the best effect of slip layer resistance reduction was achieved when the transported flow rate was 1.01 m3·h^-1. The results had important theoretical significance for improving the stability and economy of CPB slurry in pipeline.

The development of industry is inseparable from the support of mining, but mining processes consume huge energy, and huge tailings emissions can make a significant impact on the environment. In the past decades, mining industry has also developed many technologies that are related to mineral energy management, of which cemented paste backfill (CPB) is one of the representative technologies. CPB has been successfully applied to mine ground control and tailings management. In the CPB technology, the mixing process is key to achieving materials with a good final quality and controlled properties. However, in the preparation process, mixed homogeneity of the CPB is hard to achieve due to fine tailings, high solid volume fraction, and high viscosity. Most of the research focused on the effect of mixing ingredients on CPB properties rather than on the preparation process of the CPB. Therefor, it is vital to improve the performance and reduce the production cost of CPB by optimizing the mixing process. This review summarizes the current studies on the mixing technology of the CPB and its application status in China. Then it compares the advantages and disadvantages of various mixing equipment and discusses the latest research findings and research hotspots in paste preparation. Finally, the challenges and development trends of mixing technology are concluded based on the relevant application cases in China for the purpose of promoting cement-based material mixing technology development.

The macroscopic characteristics of the molten salt are governed by its microstructure. Research on the structure of molten salt provides the foundation for a full understanding of the physicochemical properties of molten salt as well as a deeper analysis of the microscopic electrolysis process in molten salt. Individuals can obtain information about the microstructure of matter with the help of several speculative and experimental procedures. The advantages and disadvantages of the various test procedures used to determine the microstructure of molten salt are compared in this paper. In the molten salt system, the typical coordination configurations of metal ions are also summarized. Furthermore, the impact of temperature, anion, cation, and metal oxide (O^2-) on the structure of molten salt is discussed in detail. It was suggested that the accuracy and completeness of molten salts' structure information need to be investigated by the integration of multiple methods and interdisciplinary. The microstructure and coordination of molten salt deepens the understanding of the elementary elements of the microstructure of matter. This paper, based on the review of coordination states of metal ions in molten salts, is hoped that it can inspire researchers to explore the interrelationship between microstructure and macroscopic properties of materials.

Understanding the in situ stress state is crucial in many engineering problems and Earth science research. The object of the present article is to present new insights into the interaction mechanism between stress state and faults. In situ stresses can be influenced by various factors, one of the most important being the existence of faults. A fault could significantly affect the value and direction of the stress components. Reorientation and magnitude changes of stresses exist adjacent to faults and stress jumps/discontinuities across the fault. In contrast, the change of stress state may lead to the transformation of faulting type and potential fault reactivation. Qualitative fault reactivation assessment using characteristic parameters under the current stress environment provides a method to assess the slip tendency of faults. The correlation between in situ stresses and fault properties enhances the ability to predict fault slip tendency via stress measurements, which can be used to further refine the assessment of fault reactivation risk. In the future, stress measurements at greater depths and long-term continuous real-time stress monitoring near/on key parts of faults are essential. In addition, much attention needs to be paid to distinguishing the genetic mechanisms of abnormal stress states and the type and scale of stress variations, as well as exploring the mechanisms of pre-faulting anomaly and fault reactivation.

As a heat-resistant wave-absorbing material, silicon carbide (SiC) aerogel has become a research hotspot at present. However, the most common silicon sources are organosilanes, which are costly and toxic. In this work, SiC aerogels were successfully prepared by using water glass as the silicon source. Specifically, the microstructure and chemical composition of SiC aerogels were controlled by adjusting the Si to C molar ratio during the sol-gel process, and the effect on SiC aerogel microwave absorption properties was investigated. The SiC aerogels prepared with the Si:C molar ratio of 1:1 have an effective electromagnetic wave absorption capacity, with a minimum reflection loss value of -46.30 dB at 12.88 GHz, and an effective frequency bandwidth of 4.02 GHz. They also have good physical properties, such as the density of 0.0444 g/cm3, the thermal conductivity of 0.0621 W/(m∙K), and the specific surface area of 1099 m²/g. These lightweight composites with microwave-absorbing properties and low thermal conductivity can be used as thermal protection materials for space shuttles and reusable carriers.

It is significant for the commercial viability of perovskite solar cells to develop tin-based devices with low toxicity. However, tin halide is a stronger Lewis acid, so that its crystallization rate is very fast, which leads to the formation of many defects that influence the device performance of tin-based perovskite solar cells. In this work, Propylamine hydrobromide (PABr) is introduced into the perovskite precursor solution as an additive to passivate defects, fabricating more uniform and dense perovskite films. Because they are too large to enter the perovskite lattices, propylamine cations just exist in the grain boundary to passivate surface defects and to promotes crystal growth in a favored orientation. The average short circuit current density is enhanced from 19.45 to 25.47 mA per square centimeter due to PABr additive because carrier recombination induced by defects is substantially decreased. In addition, the long-term illumination stability of the device is enhanced after optimization, and the hysteresis effect is negligible. Attributing to the addition of PABr, a power conversion efficiency of 9.35 percent is achieved.

The corrosion behavior of 304L stainless steel (SS) in 3.5 wt.% NaCl solution after different cavitation erosion (CE) times was evaluated by electrochemical noise and potentiostatic polarization techniques. It was found that the antagonism effect between passivation and depassivation of 304L SS presented significant distinctions in different CE periods. The passivation behavior was predominant in the incubation period of CE, and the surface of 304L SS was mainly characterized by pitting initiation. During the rising period of CE, the steel experienced a process from passivation to depassivation, and a large number of metastable pitting developed into steady-state pitting. The depassivation performance is dominant in the stable period of CE, and serious local corrosion occurred on the surface of the sample.

CoFe₂O₄ has been widely used for electromagnetic wave absorption by virtue of high Snoek limit, strong anisotropy and suitable saturation magnetization, yet the inherent shortcomings such as low dielectric loss, high density and magnetic agglomeration limit the pursuit for ideal absorbents. In this study, a microstructure regulation strategy is recommended to resolve the inherent disadvantages of pristine CoFe₂O₄ via a sol-gel auto-combustion method. A series of CoFe₂O₄ foams (S0.5, S1.0 and S1.5) constructed by 2D curved surfaces were obtained by changing the ratio of citric acid to Fe³⁺, in which the electromagnetic parameters were adjusted by morphology regulation. Thanks to the proper impedance matching and conductance loss provided by moderate complex permittivity, the effective absorption bandwidth (EAB) of S0.5 is as high as 7.3 GHz, exceeding most of CoFe₂O₄-based absorbents. Moreover, the EAB of S1.5 reaches 5.0 GHz (8.9-13.9 GHz) covering most of X band, which is ascribed to intense polarization proffered by lattice defects and heterogeneous interface. The 3D foam structure overcomes the high density and magnetic agglomeration issues of CoFe₂O₄ nanoparticles, and meanwhile, the good conductivity of 2D curved surfaces can effectively elevate the complex permittivity so as to ameliorate the dielectric loss of pure CoFe₂O₄. This study provides a fresh idea for the theoretical design and practical production of lightweight and broadband pure ferrite.

Fe–S compounds with hexagonal crystal structure are potential hydrogen permeation barrier during H₂S corrosion. Hexagonal system Fe–S films were prepared on carbon steel through corrosion and CVD deposition, and the barrier effect of different Fe-S films on hydrogen permeation was tested using electrochemical hydrogen permeation method. After that, the electrical properties of Fe–S compound during phase transformation were measured using thermoelectric measurement system. Results show that the mackinawite has no obvious barrier effect on hydrogen penetration, as a p-type semiconductor, and pyrrhotite (including troilite) has obvious barrier effect on hydrogen penetration, as an n-type semiconductor. Hydrogen permeation tests showed peak permeation performance when the surface was deposited with a continuous film of pyrrhotite (Fe_(1-x)S) and troilite. The FeS compounds suppressed hydrogen permeation by the promotion of the hydrogen evolution reaction, semiconducting inversion from p- to n-type, and the migration of ions at the interface.

Manganese substituted magnetite ferrofluids Mn_xFe_1-xFe₂O₄ (x=0 to 0.8) are prepared in this work by chemical co-precipitation reaction. The controlled growth of ferrofluids nanomaterials for antibacterial activities is challenging and therefore very few reports are available on the topic. This research focus on stabilizing the aqueous ferrofluids with tetramethylammonium hydroxide (TMAH) surfactant for high homogeneity. Morphological characterization reveals nanoparticles of 5-11 nm formed by the chemical reaction and the nanocrystalline nature as evident from the structural investigation. Mn-substituted magnetic ferrofluids are analyzed for their structural, functional and antibacterial performance according to the concentration of Mn-substituent concentration. Optical studies showed higher blue shift for Mn²⁺ substituted Mn_xFe_1−xFe₂O₄ with theoretical correlation of optical band gaps with Mn-concentration. Super paramagnetic nature of substituted ferrofluids causes zero coercivity and remanance, and this influence the particle size, cation distribution and spin canting. The structural and functional performance of the ferrofluids are correlated with the antibacterial activity finally demonstrating the highest inhibition zone formation for Mn_xFe_1-xFe₂O₄ ferrofluids.

Water-locking flocs formed by ultrafine tailings particles are detrimental to the thickener underflow concentration in the process of gravity thickening operation for paste preparation. The relationship between mesostructure and seepage characteristics of tail mortar is typically ignored in the investigation of deep dehydration stage. Shearing seepage test of unclassified tailings sedimentation bed is carried out with copper tailings, morphology and geometric distribution of micropores are analyzed via computed X-ray tomography technology, and shearing evolution of micropore structure and seepage channel are investigated to evaluate the dewatering performance of underflow slurry using a three-dimensional reconstruction approach. Results showed that porosity decreases significantly with the occurrence of shearing action. Connected pore ratio and the average radius of throat channel obtain a peak value of 0.79 and 31.38 μm, respectively, when the shearing act is adopted for 10 min. However, reverse seepage velocity and absolute permeability in bed decrease in various ranges after the shearing action. Meanwhile, the maximum flow rate reached 1.537 μm/s and absolute permeability increased by 14.16%. Shearing action changes the formation process and pore structure of the seepage channel. Isolated pores relate to the surrounding flocs to form branch channels, which then become the main seepage channel and create the dominant water seepage flow channel.

The development of solid waste resources as constituent materials for wet shotcrete has significant economic and environmental advantages. In this study, the concept of using tailings as aggregate and fly ash and slag powder as auxiliary cementitious material is proposed and experiments are carried out by response surface methodology (RSM). Multivariate nonlinear response models are constructed to investigate the effect of factors on the uniaxial compressive strength (UCS) of tailings wet shotcrete (TWSC). The UCS of TWSC is predicted and optimized by constructing gaussian process regression (GPR) and genetic algorithm (GA).  The UCS of TWSC is gradually enhanced with the increase of slag powder dosage and fineness modulus, and it is enhanced first and then decreased with the increase of fly ash dosage. The microstructure of TWSC has the highest gray value and the highest UCS when the fly ash dosage at about 120 kg/m³. The GRP-GA model constructed in this study achieves high accuracy prediction and optimization of the UCS of TWSC under multi-factor conditions.

Detecting the pipeline abnormal status, typically blockage and leakage accident, is significant for the continuity and safety of mine backfill. The pipeline system for gravity-transport high-density backfill (GHB) is of complexity. There is rarely a specifically designed, efficient, and accurate pipeline abnormal detection method for GHB. This work presents a Long Short-Term Memory based deep learning (LSTM-DL) model for GHB pipeline blockage and leakage diagnosis. First, an industrial pipeline monitoring system was introduced using pressure and flow sensors. Second, blockage and leakage field experiments were designed to solve the problem of negative sample deficiency. The pipeline statistical characteristics with different working statuses were analyzed to show its complexity. Third, the architecture of the LSTM-DL model was elaborated and evaluated. Finally, the LSTM-DL model was compared with some state-of-the-art (SOTA) learning algorithms. Results show that the backfilling cycle consists of multiple working phases and is intermittent. Although pressure and flow signals fluctuate stably in a normal cycle, their values are diverse in different cycles. Plugging causes a sudden change in interval signal features; leakage results in long variation duration and wide fluctuation range. Among the SOTA models, the LSTM-DL model has the highest detection accuracy of 98.31% for all states and the lowest misjudgment or false positive rate (FPR) of 3.21% for blockage and leakage states. The proposed model can accurately recognize various pipeline statuses for complex GHB systems.

Cemented paste backfill (CPB) is considered as one of the effective methods for resource utilization of tailings, while the high cost of ordinary Portland cement (OPC) limits its utilization. Considering the poor performance of Na₂CO₃-activated binders, in this work, supplementary materials including CaO, MgO, and calcined layered double hydroxide (CLDH) were used to modify their properties with the aim of finding an alternative binder to OPC. Isothermal calorimetric, X-Ray Diffraction (XRD) and thermogravimetry (TG) analysis were conducted to explore the reaction kinetics and phase assembles of the binder. Properties of CPB samples such as flowability, strength development and heavy metals immobilization effects were then investigated. The results showed that coupling utilization of MgO and CLDH showed better performance. The strength of sample Mg2-CLDH3 was about 2.94 MPa after curing for 56 days, which was higher than OPC-based sample. Besides, the cost of modified Na₂CO₃-activated binder was lower than OPC-based binder. Additionally, supplementary materials modified sample showed satisfactory heavy metals immobilization effects.