Search Results (54)

Fly ash and slag powder, as two of the most widely utilized industrial solid waste-based mineral admixtures, have demonstrated through extensive validation that their combined incorporation technology effectively enhances the mechanical properties and microstructural characteristics of concrete. Systematic investigations remain imperative regarding material response mechanisms under dynamic loading conditions. This study conducted microstructural analysis, static compression tests, and dynamic Split Hopkinson Pressure Bar (SHPB) impact compression tests on concrete specimens, complemented by dynamic impact simulations employing an established three-dimensional mesoscale concrete aggregate model. Through integrated analysis of macroscopic mechanical test results, mesoscale numerical simulations, and microstructural characterization data, the research systematically elucidated the influence mechanisms of different mineral admixture combinations on concrete’s dynamic mechanical behavior, energy dissipation characteristics, and fracture mechanisms. The results showed that all specimens exhibited strain rate enhancement characteristics as the strain rate increased. As the admixture approach transitioned from non-admixture to single admixture and subsequently to binary admixture, the dynamic strength, elastic modulus, and DIF of concrete increased progressively. Both the energy dissipation capacity and its proportion relative to total energy absorption showed continuous enhancement. The simulated stress–strain curves, failure modes, and fracture processes show good agreement with experimental results, this effectively verifies both the scientific validity of the mesoscale concrete model’s multiscale modeling approach and the reliability of the numerical simulations. Compared to FHC1, FMHC1’s mesoscale structure can more effectively convert externally applied energy into stored internal energy, thereby achieving superior dynamic compressive energy dissipation capacity. Full article

Rapid progress in lithium-ion batteries and AI-powered autonomous driving is poised to propel electric vehicles to a 50% share of the global automotive market by the year 2035. Today, there is a major focus on recycling electric vehicle motors, particularly on extracting rare earth elements (REEs) from NdFeB permanent magnets (PMs). This research is based on a single-furnace process concept designed to separate metal components within PM motors by exploiting the varying melting points of the constituent materials, simultaneously extracting REEs present within the PMs and transferring them into the slag phase. Thermodynamic modeling, via Factsage Equilib stream calculations, optimized the experimental process. Simulated materials substituted the PM motor, which optimized modeling-directed melting within an induction furnace. The 2FeO·SiO₂ fayalite flux can oxidize rare earth elements, resulting in slag. The neodymium oxidation reaction by fayalite exhibits a ΔG° of −427 kJ when subjected to an oxygen partial pressure ($P_{O_2}$) of 1.8 × 10⁻⁹, which is lower than that required for FeO decomposition. Concerning the FeO–SiO₂ system, neodymium, in Nd³⁺, exhibits a strong bonding with the ${\mathrm{S}\mathrm{i}\mathrm{O}}_4^{4^{-}}$ matrix, leading to its incorporation within the slag as the silicate compound, Nd₂Si₂O₇. When 30 wt.% fayalite flux was added, the resulting experiment yielded a neodymium extraction degree of 91%, showcasing the effectiveness of this fluxing agent in the extraction process. Full article

SiC_f/SiC ceramic matrix composite (CMC), a hard and brittle material, faces significant challenges in efficient and high-quality processing of small-sized shapes. To address these challenges, the nanosecond laser was used to process micro-holes in the SiC_f/SiC CMC using a two-step drilling method, including laser pre-drilling in air and laser final-drilling with a water jet. The results of the single-parameter variation and optimized orthogonal experiments reveal that the optimal parameters for laser pre-drilling in air to process micro-holes are as follows: 1000 processing cycles, 0.7 mJ single-pulse energy, −4 mm defocus, 15 kHz pulse-repetition frequency, and 85% overlap rate. With these settings, a micro-hole with an entrance diameter of 343 μm and a taper angle of 1.19° can be processed in 100 s, demonstrating high processing efficiency. However, the entrance region exhibits spattering slags with oxidation, while the sidewall is covered by the recast layer with a wrinkled morphology and attached oxides. These effects are primarily attributed to the presence of oxygen, which enhances processing efficiency but promotes oxidation. For the laser final-drilling with a water jet, the balanced parameters for micro-hole processing are as follows: 2000 processing cycles, 0.6 mJ single-pulse energy, −4 mm defocus, 10 kHz pulse-repetition frequency, 85% overlap rate, and a 4.03 m/s water jet velocity. Using these parameters, the pre-drilled micro-hole can be finally processed in 96 s, yielding an entrance diameter of 423 μm and a taper angle of 0.36°. Due to the effective elimination of spattering slags and oxides by the water jet, the final micro-hole exhibits a clean sidewall with microgrooves, indicating high-quality micro-hole processing. The sidewall morphology could be ascribed to the different physical properties of SiC fiber and matrix, with steam explosion and cavitation erosion. This two-step laser drilling may provide new insights into the high-quality and efficient processing of SiC_f/SiC CMC with small-sized holes. Full article

This study explored the behavior of lead, copper, and iron during the leaching process of flash smelting slag from direct-to-blister copper flash smelting using l-ascorbic acid solutions. Flash smelting slag is generated in considerable quantities by various copper smelters worldwide. One drawback of the single-stage flash smelting technology for copper concentrates is the production of large quantities of metal-rich by-products. However, through appropriate management of postprocess waste, valuable components such as copper or lead can be recovered. In practice, the slag is typically subjected to decoppering processes involving electric and converter furnaces. The hydrometallurgical process proposed in this study is aimed at replacing high-temperature recovery methods. The primary objective of the experiments was to investigate the effects of variations in specific leaching parameters and the addition of auxiliary substances on the leaching efficiency of lead, copper, and iron. Four parameters were adjusted during the tests: concentration of l-ascorbic acid, liquid-to-solid phase ratio, temperature, and time. An oxidizing agent in the form of perhydrol and citric acid with an oxidant were used as additives. Optimal process conditions were determined to achieve maximum lead leaching efficiency while maintaining relatively low leaching of copper and iron. The experiments indicated that leaching in ascorbic acid solutions resulted in lead extraction efficiencies ranging from approximately 68% to more than 88%, depending on the conditions. Conversely, relatively low leaching efficiencies of iron (4–12%) and copper (0–29%) were observed. Full article

Laser cutting is an established, multi-physical process widely adopted by the metallurgical industry. However, this fast industrialisation has had a significant impact on quality control. Reviews from 2008 to 2022 primarily focus on single-criterion quality approaches, targeting defects like the Heat-Affected Zone, surface roughness, or kerf geometry, rather than adopting comprehensive methods. In addition, these studies show that cutting quality can be improved by selecting laser manufacturing parameters and part parameters such as thickness or material. However, the influence of part morphology remains underexplored. Following this observation, this study proposes a generic and complete method adapted from the Failure Modes, Effects and Criticality Analysis, allowing the evaluation of the criticality of all cutting defects in a part. It focuses on six laser cutting defects defined in an international standard and three types of morphology: arcs, angles and segments. The aim is to establish a holistic approach linking morphologies to all defect types. Industrial application reveals that thermal defects are highly influenced by morphology. Burrs and adherent slag are particularly critical in arcs and angles, while segments are less sensitive. This analysis establishes design limits and offers practical tools to improve industrial laser cutting through detailed quality assessments. Full article

The lepidolite slag from Jiangxi contains 0.51% rubidium. Utilizing lepidolite slag in cement production does not enable the efficient recovery of the rubidium it contains. This study investigates the feasibility of extracting rubidium from lepidolite slag through sulfuric acid leaching. The research method involved initially conducting single-factor experiments, followed by the application of response surface methodology to determine the optimal conditions. The optimization results revealed that the leaching rate of rubidium could reach 86.26% under the following conditions: a temperature of 85 °C, a rotational speed of 480 r/min, a sulfuric acid concentration of 3.53 mol/L, a duration of 91.64 min, and a liquid–solid ratio of 5.86. The experimental results closely matched the model’s predicted value of 86.32%. The results demonstrate the effectiveness of the response surface methodology in modeling the rubidium leaching process and provide a reference for the recycling of rubidium from lepidolite slag. Full article

Currently, the environment and its natural resources face many issues related to the depletion of natural resources, in addition to the increase in environmental pollution resulting from uncontrolled waste disposal. Therefore, it is crucial to identify practical and effective ways to utilize these wastes, such as transforming them into environmentally friendly concrete. Artificial lightweight aggregates (ALWAs) are gaining interest because of their shift in focus from natural aggregates. Researchers have developed numerous ALWAs to eliminate the need for natural aggregates. This article explores the diverse applications of ALWAs across different industries. ALWAs are currently in the research phase due to various limitations compared to the availability of the various natural aggregates that form more durable solutions. However, researchers have discovered that certain artificial aggregates prioritize weight over strength, allowing for the effective use of ALWAs in applications like pavements. We thoroughly studied the various ALWAs discussed in this article and found that fly ash and construction waste are the most diverse sources of primary material for ALWAs. However, the production of these aggregates also presents challenges in terms of processing and optimization. This article’s case study reveals that ALWAs, consisting of 80% fly ash, 5% blast-furnace slag, and only 15% cement, can yield a sustainable solution. In the single- and double-step palletization, the aggregate proved to be less environmentally harmful. Additionally, the production of ALWAs has a reduced carbon footprint due to the recycling of various waste materials, including aggregates derived from fly ash, marble sludge, and ground granulated blast-furnace slag. Despite their limited mechanical strength, the aggregates exhibit superior performance, making them suitable for use in high-rise buildings and landscapes. Researchers have found that composition plays a key role in determining the application-based properties of aggregates. This article also discusses environmental and sustainability considerations, as well as future trends in the LWA field. Simultaneously, recycling ALWAs can reduce waste and promote sustainable construction. However, this article discusses and researches the challenges associated with the production and processing of ALWAs. Full article

The thermodynamic properties of the CaO-Al₂O₃-VO_x slag system are of great significance to the direct alloying of vanadium in the smelting process of vanadium steel. In this paper, the phase equilibrium relationship of the CaO-Al₂O₃-VO_x system under argon atmosphere at 1500 °C was studied with a high-temperature phase equilibrium experiment. Combined with SEM-EDS, XRD, and XPS, the types and compositions of each phase of the equilibrium slag samples and the content of different valence states of the vanadium element were determined. The result shows that under argon atmosphere (p(O₂) = 10⁻³ atm) at 1500 °C, the CaO-Al₂O₃-VO_x slag system contains four three-phase regions, seven two-phase regions, and a single-phase region (glass phase). The phase equilibrium results were plotted in a CaO-Al₂O₃-V₂O₅-VO₂ spatial phase diagram, and the phase equilibrium results were projected on the CaO-Al₂O₃-V₂O₅ and CaO-Al₂O₃-VO₂ pseudo-ternary phase diagrams, respectively. In the end, the rationality of projecting the phase equilibrium results to the pseudo-ternary phase diagram was quantitatively evaluated. Full article

With the advent of the COVID-19 pandemic, the global consumption of single-use surgical masks has risen immensely, and it is expected to grow in the coming years. Simultaneously, the disposal of surgical masks in the environment has caused plastic pollution, and therefore, it is exigent to find innovative ways to handle this problem. In this study, surgical masks were processed in a laboratory using the mechanical grinding method to obtain recycled surgical masks (RSM). The RSM was added in doses of 0%, 1%, 2%, 3%, and 4% by volume of geopolymer bricks, which were synthesized with ground granulated blast furnace slag (GGBS), rice husk ash (RHA), sand, and sodium silicate (Na₂SiO₃) at ambient conditions for a duration of 28 days. The developed bricks were tested for compressive strength, flexural strength, density, water absorption, efflorescence, and drying shrinkage. The results of the study reveal that compressive strength and flexural strength improved with the inclusion of RSM in the bricks. The highest values of compressive strength and flexural strength were 5.97 MPa and 1.62 MPa for bricks with 4% RSM, respectively. Further, a reduction in the self-weight of the bricks was noticed with an increase in RSM. There was no pronounced effect of RSM on the water absorption and efflorescence properties. However, the RSM played a role in reducing the drying shrinkage of the bricks. The sustainability analysis divulges the catalytic role of RSM in improving material performance, thereby proving to be a potential candidate for low-carbon material in the construction industry. Full article

Magnesium slag-based porous materials (MSBPM) were successfully synthesized using alkali activation and foaming methods as an effective adsorbent for Pb²⁺ in solution. The effects of foaming agent type, foaming agent dosage, alkali dosage, and water glass modulus on the properties of the MSBPM were studied, and the micromorphology and porosity of the MSBPM were observed using microscopy. The influence of pH value, initial concentration, and adsorbent dosage on the Pb²⁺ adsorption was investigated. The results showed that a porous material (MSBPM-H₂O₂) with high compressive strength (8.46 MPa) and excellent Pb²⁺ adsorption capacity (396.11 mg·g⁻¹) was obtained under the optimal conditions: a H₂O₂ dosage of 3%, an alkali dosage of 9%, a water glass modulus of 1.3, and a liquid–solid ratio of 0.5. Another porous material (MSBPM-Al) with a compressive strength of 5.27 MPa and the Pb²⁺ adsorption capacity of 424.89 mg·g⁻¹ was obtained under the optimal conditions: an aluminum powder dosage of 1.5‰, an alkali dosage of 8%, a water glass modulus of 1.0, and a liquid–solid ratio of 0.5. When the pH of the aqueous solution is 6 and the initial Pb²⁺ concentrations are 200~500 mg·L⁻¹, the MSBPM-H₂O₂ and MSBPM-Al can remove more than 99% of Pb²⁺ in the solution. The adsorption process of both materials followed the Langmuir isotherm model and pseudo-second-order kinetic model, indicating that the adsorption process was a single-molecule layer chemical adsorption. Full article

With the rapid growth of road transportation, the increase in road subgrade and pavement diseases has become a pressing issue, requiring the development of cost-effective filling materials that meet both strength and economic requirements. Foam lightweight soil, as a novel construction material, offers excellent characteristics such as adjustability in density and strength, high fluidity, and self-supporting capabilities. It has been widely utilized in various engineering applications, including road subgrade backfilling and retaining wall fillings. However, the conventional application of foam lightweight soil, predominantly cement-based, has raised concerns about pollution and high energy consumption due to large cement dosages. To address this issue, this study proposes the integration of phosphogypsum, a byproduct of wet-process phosphoric acid production, into foam lightweight soil. Phosphogypsum has a significant annual discharge and accumulation, but its comprehensive utilization rate remains relatively low. The research investigates the combination of phosphogypsum and foam lightweight soil by introducing mineral admixtures such as microsilica and slag powder to improve early strength development and reduce the influence of fluoride impurities on early strength. The optimal mix proportions for two types of foam lightweight soil, namely phosphogypsum cement microsilica foam (PGCF) and phosphogypsum cement slag powder foam (PGCS), were determined based on single-factor tests. The key parameters considered for optimization were water–binder ratio, foam content, and phosphogypsum dosage. The findings indicate that both PGCF and PGCS foam lightweight soil possess superior mechanical properties and thermal conductivity. By incorporating phosphogypsum into the mix, the early strength development of foam lightweight soil is effectively improved. Moreover, with suitable mix proportions, the maximum phosphogypsum dosage can be achieved, demonstrating potential economic and environmental benefits. In conclusion, this research provides valuable insights into the effective utilization of phosphogypsum in foam lightweight soil, offering a promising solution for the challenges associated with phosphogypsum disposal and the demand for sustainable construction materials in highway engineering. Full article

In the process of electroslag remelting (ESR) for large-sized slab ingots, controlling the surface quality of the slab ingot is challenging due to its relatively high width-to-thickness ratio. In this study, a three-dimensional dynamic mathematical model for single-electrode ESR slab ingots was developed using dynamic mesh technology, with the aid of the commercial software FLUENT. The model is based on the electromagnetic field equation, flow field equation, and energy equation. A detailed analysis of various physical fields and the distribution law of the metal pool shape was conducted. According to the calculation results, the maximum flow velocity of the molten slag was found below the consumable electrode, with the range of maximum velocity at different time points varying between 4.35 × 10⁻² and 4.88 × 10⁻² m/s. The range of the maximum temperature for the slag bath at different time points was between 2118 and 2122 K. As the remelting continued, the impact of the forced cooling of the bottom plate on the temperature of the metal pool weakened. Consequently, the temperature gradient of the electroslag ingot gradually decreased, the depth of the metal pool increased, and the height of the metal liquid head in the metal pool rose. The effects of different voltages, filling ratios, and mold chamfers on the shape of the metal pool were investigated using the established mathematical model. Based on the research findings from the mathematical model, the technical processes for ESR J80 large-sized slab ingots were improved, providing solutions to improve the surface quality of the ESR large-sized slab ingots. Full article

In the oxygen-enriched side-blown smelting furnace for the treatment of electroplating sludge, fluent was used to simulate the gas–liquid two-phase flow process. The relationship between the lance diameter, lance inclination, bath depth, and the bath evaluation indicators were studied, and the oxygen lance spacing was optimized. The results show that the high velocity and high gas rate areas were near the oxygen lance, while the stirring dead zones with low velocity appeared in the central and bottom areas of the molten pool. The key parameters were optimized using single-factor analysis and multifactor comprehensive optimization. The results showed that the bath evaluation indicators were all at good levels under the optimal parameter conditions. These were comprehensively obtained as the following: the lance diameter was 25 mm, the lance inclination was 15°, the lance spacing was 1050 mm, and the bath depth was 1500 mm. The industrial test carried out in an environmental protection enterprise in Guangdong achieved satisfactory results. The test shows that the electroplating sludge containing 7.24% Cu can be melted at 1300~1400 °C to obtain matte. Compared with industrial copper slag, the smelting slag has a higher CaO and a lower Fe content. Full article

The influence of different carbon sources, including anthracite, calcined petroleum coke, three samples of high-temperature coke, biochar, and a mixture of 50 wt.% biochar and 50 wt.% coke, on slag foaming behavior was studied. The slag’s composition was set to FeO-CaO-Al₂O₃-MgO-SiO₂, and the temperature for slag foaming was 1600 °C. The effect of the carbon sources was evaluated using foaming characteristics (foam height, foam volume, relative foaming height, and gas fraction), X-ray diffraction (XRD), chemical analysis of the slag foams, Mossbauer spectroscopy, observation by scanning electron microscope (SEM), and energy-dispersive spectroscopy (EDS) mapping. Different foaming phenomena were found among conventional sources, biochar as a single source, and the mixture of coke and biochar. Biochar showed the most inferior foaming characteristics compared to the other studied carbon sources. Nevertheless, the slag foaming process was improved and showed slag foaming characteristics similar to results obtained using conventional carbon sources when the mixture of 50 wt.% coke and 50 wt.% biochar was used. The XRD analysis revealed a difference between the top and bottom of the slag foams. In almost all cases, a maghemite crystalline phase was detected at the top of the slag foams, indicating oxidation; metallic iron was found at the bottom. Furthermore, a difference in the slag foam (mixture of coke and biochar) was found in the presence of such crystalline phases as magnesium iron oxide (Fe₂MgO₄) and magnetite (Mg₀.₄Fe₂.₉₆O₄). Notwithstanding the carbon source applied, a layer between the foam slag and the crucible wall was found in many samples. Based on the SEM/EDS and XRD results, it was assumed this layer consists of gehlenite (Ca₂(Al(AlSi)O₇) and two spinels: magnesium aluminate (MgAl₂O₄) and magnesium iron oxide (Fe₂MgO₄). Full article

Argon bottom stirring is commonly practiced in secondary steelmaking processes due to its positive effects on achieving uniform temperatures and chemical compositions throughout a steel melt. It can also be used to facilitate slag metal refining reactions. The inter-mixing phenomena associated with argon gas injection through porous plugs set in the bottom and its stirring efficiency can be summarized by evaluations of 95% mixing times. This study focuses on investigating the impact of different plug positions and ratios of argon flow rates from two plugs on mixing behavior within a 110-tonne, elliptical-shaped industrial ladle. A quasi-single-phase modeling technique was employed for this purpose. The CFD findings revealed that the optimal position of the second plug is to be placed diametrically opposite the existing one at an equal mid-radius distance (R/2). An equal distribution of argon flow rates yielded the best results in terms of refractory erosion. A comparative study was conducted between single- and dual-plug-configured ladles based on flow behavior and wall shear stresses using this method. Furthermore, a transient multiphase model was developed to examine the formation of slag open eyes (SOE) for both single- and dual-plug configurations using a volume of fluid (VOF) model. The results indicated that the dual-plug configuration outperformed the current single-plug configuration. Full article