Search Results (285)

The potential of utilizing inorganic constituents in processed animal proteins (PAPs) for species identification in animal feeds was investigated, with the aim of using these constituents to ensure the quality and authenticity of the products. This study aimed to quantify the inorganic content across various PAP species and assess whether inorganic analysis could effectively differentiate between PAP species, ultimately aiding in the identification of PAP fractions in animal feeds. Four types of PAPs, namely bovine, swine, poultry, and fish-based, were analyzed and compared to others made up of feathers of vegetal-based feed. Also, three insect-based PAPs (Cricket, Silkworm, Flour Moth) were considered in this study to evaluate the differences in terms of the nutrients present in this type of feed. Ionic chromatography (IC) was used to reveal the concentrations of NO₃⁻, NO₂, Cl⁻, and SO₄²⁻, and inductively coupled plasma optical emission spectroscopy (ICP-OES) to detect Al, Ca, Cd, Cr, Cu, Fe, K, Mg, Mn, Mo, Na, Ni, P, Si, Sr, Ti, and Zn. The application of multivariate chemometric techniques to the experimental results allowed us to determine the identification capability of the inorganic composition to identify correlations among the variables and to reveal similarities and differences among the different species. The results show the possibility of using this component for discriminating between different PAPS; in particular, fish PAPs are high in Cd, Sr, Na, and Mg content; swine PAPs have lower metal content due to high fat; feathers and vegetal feed have similar Al, Si, and Ni, but feathers are higher in Fe and Zn; and insect PATs have nutrient levels comparable to PAPs of other origins but are very high in Zn, Cu, and K. Full article

In this study, the thermodynamic simulation model and system of the copper side-blown smelting process were established using the chemical equilibrium constant method, based on the process reaction mechanism, multiphase equilibrium principle, and MetCal software platform (MetCal v7.81). Under typical production conditions, the composition of the product and the distribution behavior of impurity elements were simulated. The results indicate that the average relative error between the calculated mass fractions of major elements such as Cu, S, Fe, SiO₂, CaO, MgO, and Al₂O₃ in copper matte and smelting slag, and the actual production values, is 4.25%. Additionally, the average relative error between the calculated distribution ratios of impurity elements such as Pb, Zn, As, Bi, Mo, Au, and Ag in copper matte and smelting slag, and the actual production data, is 6.74%. Therefore, this model and calculation system accurately reflects the actual production situation of the copper side-blown smelting process well and has potential to predict process output accurately while optimizing process parameters, effectively guiding production practice. Full article

An innovative technology for the direct reduction of copper slag was studied while smelting Cu-Fe alloy by carbon to recover the main valuable elements from the copper smelting slag. The melting temperature of samples first decreased, followed by an increase in Fe₃O₄ content in slag. The melting temperature reached the minimum temperature of 1157 °C once the Fe₃O₄ content was about 8 wt%. The recovery rate of copper and iron first increased gradually, followed by a rapid increase in the modifier (CaO). Subsequently, the rise in the recovery rate slowed down. The reduction rate of copper and iron only increased by 1.61% and 1.05% from 5 wt% CaO to 10 wt% CaO, but significantly increased by 8.89% and 14.21% from 10 wt% CaO to 25 wt% CaO, and remained almost unchanged beyond 25 wt% CaO. This could be attributed to the reaction between modifier (CaO) and silicate in acidic copper slag to generate low melting point composite oxide while replacing free iron oxides, improving the melting properties and reduction reaction. Meanwhile, the recovery rates of copper and iron increased with the increase of reaction time, reaction temperature, and reduction agent in a certain range. To obtain good element yield, the optimum conditions for reducing copper and iron from the molten copper slag were determined to be 1500 °C, 14 wt% C, 20–25 wt% CaO, and 60–80 min. The recovery rates of iron and copper reached about 90% and 85%, and the contents of iron and copper in alloy reached about 91–93 wt% and 5–7 wt%, respectively. The tailing was mainly composed of Ca₃Si₃O₉, Ca(Mg,Al)(Si,Al)₂O₆, and SiO₂, which could be used as a raw material for cement and pelletizing. Full article

The growing use of aluminum and its compounds has increased the volume of aluminum waste. To mitigate environmental impacts and cut down on manufacturing expenses, extensive investigations have recently been undertaken to recycle aluminum compounds. This paper outlines the outcomes of a study on fabricating standard EN AW-2007 alloy using industrial and secondary scrap through continuous casting. The resultant recycled bars were analyzed for their chemical makeup and examined for microstructural features in both the cast and T4 states, undergoing mechanical property evaluations. The study identified several phases in the cast form through LM, SEM + EDS, and XRD techniques: Al₇Cu₂Fe, θ-Al₂Cu, β-Mg₂Si, Q-Al₄Cu₂Mg₈Si₇, and α-Al₁₅(FeMn)₃ (SiCu)_2, along with Pb particles. Most primary intermetallic precipitates such as θ-Al₂Cu, β-Mg₂Si, and Q-Al₄Cu₂Mg₈Si₇ dissolved into the α-Al solid solution during the solution heat treatment. In the subsequent natural aging process, the θ-Al₂Cu phase predominantly emerged as a finely dispersed hardening phase. The peak hardness achieved in the EN AW-2007 alloy was 124.8 HB, following a solution heat treatment at 500 °C and aging at 25 °C for 80 h. The static tensile test assessed the mechanical and ductility properties of the EN AW-2007 alloy in both the cast and T4 heat-treated states. Superior strength parameters were achieved after solution heat treatment at 500 °C for 6 h, followed by water quenching and natural aging at 25 °C/9 h, with a tensile strength of 435.0 MPa, a yield strength of 240.5 MPa, and an appreciable elongation of 18.1% at break. The findings demonstrate the feasibility of producing defect-free EN AW-2007 alloy ingots with excellent mechanical properties from recycled scrap using the continuous casting technique. Full article

The main aim of this research was to investigate the aluminum AlSi9Cu3(Fe) machining chips recycling possibility utilizing a direct hot extrusion process and thixoforming. The thixo feedstock was prepared directly from the aluminum alloy AlSi9Cu3(Fe) machining chips waste without any remelting step. The machining chips were compacted, and direct hot extruded to create the solid samples and thixo feedstock. The aluminum alloy AlSi9Cu3(Fe) machining chips had a high degree of plastic deformation and after extrusion and heating in the semisolid temperature range, the suitable globular microstructure was achieved, which is a precondition for a successful thixoforming process. This approach can be characterized as a semisolid recycling process with a lower energy consumption, a higher material yield, and reduced greenhouse gas emissions into the atmosphere compared with conventional casting and recycling. Optical metallography, scanning electron microscopy accompanied with energy dispersive spectroscopy, electrical conductivity, and mechanical properties investigation were performed on the reference casted sample with a dendritic microstructure, the extruded sample with a severely deformed microstructure, and finally the thixoformed samples with a globular microstructure produced with different parameters, according to the Taguchi L4 (2³) experimental plan. Full article

This study investigates the impact of varying extrusion ratios on the microstructure and mechanical properties of AlSiCuFeMnYb alloy. Following hot extrusion, significant enhancements are observed in the microstructure of the cast rare earth aluminium alloy. Within the cross-sectional microstructure, the α-Al phase is reduced in size, and its dendritic morphology is eliminated. The morphology of the eutectic Si phase transitions from long strips to short rods, fine fibres, or granular forms. Similarly, the Fe-rich phase changes from a coarse skeletal and flat noodle shape to small strips and short skeletal forms resembling Chinese characters. The CuAl₂ phase evolves from large blocks to smaller blocks and granular forms, while the Yb (Ytterbium)-rich rare earth phase shifts from large blocks to smaller, more uniformly distributed blocks. In the longitudinal section, the structure aligns into strips along the extrusion direction, with the spacing between these strips decreasing as the extrusion ratio increases. At an extrusion ratio of 22.56, the alloy demonstrates superior mechanical properties with a tensile strength of 325.50 MPa, a yield strength of 254.44 MPa, a hardness of 143.90 HV, and an elongation of 15.47%. These represent improvements of 27.8%, 36.5%, 38.9%, and 236.4%, respectively, compared with the as-cast rare earth alloy. In addition, the fracture surface of the extruded rare earth alloy exhibits obvious ductile fracture characteristics. Additionally, the alloy undergoes dynamic recrystallisation and dislocation entanglement during hot extrusion. The emergence of a twinned Si phase and a dynamically precipitated nanoscale CuAl₂ phase are critical for enhancing deformation strengthening, modification strengthening, and dynamic precipitation strengthening of the extruded alloys. Full article

The study aimed to evaluate for the first time the degree of contamination of soil and crops with major and trace elements (Cd, Co, Cr, Cu, Ni, Pb, Zn, F, Na, Mg, Si, P, Cl, Fe, Al) in agricultural lands situated in the Lower Danube Basin, Galati and Braila counties (SE Romania), impacted by the steel industry. Soil samples, as well as leaves and seeds of wheat, corn, and sunflower, were collected from two depths in 11 different sites. Along with elemental and mineralogical analyses, performed by HR-CS AAS, PIGE, SEM-EDX, and ATR-FTIR, the soil pH, texture, organic matter, electric conductivity, and CaCO₃ content were investigated. The results showed that the levels of Cr (83.27–383.10 mg kg⁻¹), Cu (17.11–68.15 mg kg⁻¹), Ni (30.16–55.66 mg kg⁻¹), and F (319–544 mg kg⁻¹) in soil exceeded the Romanian regulations for sensitive use of the land. Igeo, EF, PI, and PERI pollution indices indicate that the soil is moderate to highly contaminated with Cr, Ni, and Cu, while the CSI and mERM_Q indices suggested a relatively low risk for metal contamination. The elemental concentrations in plant tissues and bioaccumulation factors (BFs) provide valuable insights into the soil–plant relationship, health risks, and the selectivity of plant compartments for different elements. Thus, the results revealed that the wheat plants tended to exclude the bioaccumulation of particular elements in their tissues, while exhibiting a different bioaccumulation pattern for Zn and Cu. In the case of corn, most BFs were below one, indicating a limited phytoaccumulation capacity. However, exceptions were observed for Cd, Zn, and Cu with the sunflower BFs indicating higher bioconcentration of these elements in leaves and seeds compared to other elements. Chromium (Cr) contributes to non-carcinogenic dermal contact and ingestion hazards, children being more susceptible to the adverse effects of this contaminant. Full article

The rupture of an iron mining tailing dam in Brumadinho, Brazil, released around 10 million cubic meters of tailings, of which 1.6 Mm³ reached the Paraopeba River. In this work, a total of 30 samples from three bottom sediment cores were collected in the lower course of the Paraopeba River basin and analyzed for major, trace and rare earth elements by ICP-OES and ICP-MS. The sediments presented a range of compositions with different weathering histories, overall marked by depleted Ca²⁺, Na⁺ and K⁺ compared with the average UCC, PAAS and NASC and some advanced weathering trends. The samples presented a fractionation pattern characterized by a continuous depletion of light REEs from La to Sm and a regular decreased distribution of heavy REEs from Gd to Yb, and the Co/Th vs. La/Sc diagram indicates a predominant intermediate source. The upper samples presented the highest contents of REEs, probably due to the higher presence of iron and aluminum oxides and hydroxides, which can be related to more advanced weathering. The Al, Cu, Ni, V, Zn, Co, Mn, Ti, Fe and Si concentrations and the CF, EF and Igeo index values varied across the sediment core samples, demonstrating that there were long periods of geogenic or anthropogenic contributions. Full article

Peatland hydrology plays an important role in preserving or changing the record in any consideration of past atmospheric deposition records in peat bogs. The Šijec bog, located on the Pokljuka plateau in Slovenia, is one of the largest ombrotrophic peatlands. We sampled the surface pools, pore water, drainage from the peatland, and karst streams not connected to the peatland. Additionally, we sampled the precipitation, as ombrotrophic peatlands receive mineral matter solely from the atmosphere. The results of the evaluation of the chemical and isotopic composition indicated different origins of dissolved mineral matter in different water types. The components originating from the bedrock and surrounding soils (Ca, Mg, Al, Si, Sr) predominated in the streams. The chemical composition of the peatland drainage water revealed the significant removal of major components from the peatland, particularly elements like Al, Fe, and REE, and metals that are readily dissolved in an acidic environment or mobile in their reduced state. Despite their solubility, concentrations of metals (As, Cr, Cu, Fe, Ni, Pb, Ti) and REE in surface pools remained higher than in the drainage due to incomplete elimination from the peatland. The composition of pore water reflects variations among the W and E parts of the peatland, indicating a heterogenous hydrological structure with different dynamics, such as an additional source of water at approximately 90 cm depth in the NW part. The chemical composition and isotope signature (¹⁸O and ²H) of pore water additionally indicated a heterogeneous recharge with residence times of less than a year. The overall analysis indicated a predominantly ombrotrophic type and a small part in the NW area of the peatland as a minerotrophic type of peat. Full article

FeCoNiCrAl0.8Cu0.5Si0.5 high-entropy alloys were fabricated using vacuum induction melting and laser deposition processes, followed by a comparison of the structural and mechanical properties of two distinct sample types. The as-cast FeCoNiCrAl0.8Cu0.5Si0.5 alloy is comprised of BCC1, BCC2, and Cr3Si phases, while the laser-deposited alloy primarily features BCC1 and BCC2 phases. Microstructural analysis revealed that the as-cast alloy exhibits a dendritic morphology with secondary dendritic arms and densely packed grains, and the laser-deposited alloy displays a dendritic structure without the formation of granular interdendritic regions. For mechanical properties, the as-cast FeCoNiCrAl0.8Cu0.5Si0.5 alloy demonstrated higher hardness than the as-deposited alloy, with values of 586 HV0.2 and 557 HV0.2, respectively. The wear rate for the as-cast alloy was observed at 3.5 × 10⁻⁷ mm³/Nm, with abrasive wear being the primary wear mechanism. Conversely, the as-deposited alloy had a wear rate of 9.0 × 10⁻⁷ mm³/Nm, characterized by adhesive wear. The cast alloy exhibited an icorr of 4.062 μA·cm⁻², with pitting as the form of corrosion. The laser-deposited alloy showed an icorr of 3.621 μA·cm⁻², with both pitting and intergranular corrosion observed. The laser-deposited alloy demonstrated improved corrosion resistance. The investigation of their microstructure and mechanical properties demonstrates the application potential of FeCoNiCrAl0.8Cu0.5Si0.5 alloys in scenarios requiring high hardness and enhanced wear resistance. Full article

The exploitation of iron ore could cause heavy metals pollution in the soils, which threatens the ecosystem and human health. In this study, soil, stream sediment, tailings, rock, and atmospheric deposition samples were collected from an iron mine in Baotou City. The concentrations of As, Cd, Cr, Cu, Hg, Ni, Pb, Zn, Al₂O₃, CaO, K₂O, MgO, Na₂O, SiO₂, and Fe₂O₃, as well as the mineral composition and heavy metal speciation of the samples, were analyzed for pollution assessment and source identification of heavy metals. The results reveal that the concentration of Cu in the soils was significantly higher than the background value, and an unpolluted to moderately polluted state was the main pollution level. By analyzing the relationship between Cu/Al₂O₃ and CaO in different samples, as well as the characteristics of the chemical index of alteration (CIA), mineral composition, and the chemical speciation of Cu in soils and profiles, the results suggest that tailings were the source of Cu pollution in soils. The distribution characteristics of Cu and CaO in stream sediments indicated that hydraulic transport may be one of the main migration pathways. In addition, wind transport may also be a pathway of migration. Full article

The phenomenon of spontaneous dispersion is considered as the cause of the microstratification of metal melts. In a microstratification melt, a violation of long-range order in the arrangement of atoms (LRO) is observed, which corresponds to a dispersed particle size of more than 2 nm. Microseparation occurs due to spontaneous dispersion upon contact of liquid and solid metal or the mixing of two liquid metals. The possibility of spontaneous dispersion was assessed using three different criteria: Volmer’s cr iterion, Rehbinder’s criterion and the diffusion rate criterion. The diffusion rate criterion was obtained on the basis of the theory of rate processes, which describes how diffusing atoms overcome the interphase boundary. It has been established that Al–Sn melts contain colloidal-scale particles (4 nm), and Al–Si and Al–Ge melts contain atomic-scale particles (0.1 nm). For a system with a continuous series of Cu–Ni solid solutions in dispersion (Cu10Ni90—Cu20Ni80), the particle size is 2 nm. The particle size of the ternary eutectic GaInSn in the dispersion (Ga50In50—Ga50Sn50) is 5.6 nm, and the size of immiscible Cu–Fe melts in the dispersion (Cu80Fe20—Cu60Fe40) is 4.8 nm. Long-range order violations (LRO) and the presence of microlayering with colloidal particles larger than 20 nm were observed in the GaInSn ternary eutectic, in the Al–Sn simple eutectic with the preferential interaction of similar atoms, and in Cu–Fe melts with a monotectic phase diagram. Full article

Printed circuit boards (PCBs) are the main components of e-waste. In order to reduce the negative impact of waste PCBs on human health and the environment, they must be properly disposed of. A new method is demonstrated for recycling waste PCBs. It is referred to as the high-temperature thermo-mechano-chemical gasification (TMCG) of PCBs by the detonation-born gasification agent (GA), which is a blend of H₂O and CO₂ heated to a temperature above 2000 °C. The GA is produced in a pulsed detonation gun (PDG) operating on a near-stoichiometric methane–oxygen mixture. The PDG operates in a pulsed mode producing pulsed supersonic jets of GA and pulsed shock waves possessing a huge destructive power. When the PDG is attached to a compact flow reactor filled with waste PCBs, the PCBs are subject to the intense thermo-mechano-chemical action of both strong shock waves and high-temperature supersonic jets of GA in powerful vortical structures established in the flow reactor. The shock waves grind waste PCBs into fine particles, which undergo repeated involvement and gasification in the high-temperature vortical structures of the GA. Demonstration experiments show full (above 98%) gasification of the 1 kg batch of organic matter in a setup operation time of less than 350 s. The gaseous products of PCB gasification are mainly composed of CO₂, CO, H₂, N₂, and CH₄, with the share of flammable gas components reaching about 45 vol%. The solid residues appear in the form of fine powder with visible metal inclusions of different sizes. All particles in the powder freed from the visible metal inclusions possess a size less than 300–400 μm, including a large fraction of sizes less than 100 μm. The powder contains Sn, Pb, Cu, Ni, Fe, In, Cd, Zn, Ca, Si, Al, Ti, Ni, and Cl. Among these substances, Sn (10–20 wt%), Pb (5–10 wt%), and Cu (up to 1.5 wt%) are detected in the maximum amounts. In the powder submitted for analysis, precious elements Ag, Au, and Pt are not detected. Some solid mass (about 20 wt% of the processed PCBs) is removed from the flow reactor with the escaping gas and is partly (about 10 wt%) trapped by the cyclones in the exhaust cleaning system. Metal inclusions of all visible sizes accumulate only in the flow reactor and are not detected in powder samples extracted from the cyclones. The gasification degree of the solid residues extracted from the cyclones ranges from 76 to 91 wt%, i.e., they are gasified only partly. This problem will be eliminated in future work. Full article

This study investigates the impact of the surface characteristics and the inner close-to-surface characteristics of die-cast Al-Si-Cu alloy on the anodizing process under steady-state voltage and current modes. Samples of industrial-pressure die-cast aluminium–silicon alloy AlSi12Cu1(Fe) underwent anodization in as-die-cast surface conditions and after surface-grinding operations with material removal of 0.1, 0.5, and 1 mm. After surface grinding operations, the anodic layer thickness was significantly greater when subjected to a steady-state voltage of 35 V compared to that formed under a steady-state voltage of 20 V, showing an increase in the range of 2 to 2.5 times more than the thickness at 20 V. Additionally, anodizing under steady-state current mode (1.6 A·dm⁻²) yielded thicker layers compared to steady-state voltage mode (35 V, 1.6 A·dm⁻² max) across all surface states (as-cast, ground). SEM-EDS analysis with element mapping revealed the subsequent effects of element distribution on anodic layer growth and structure. Grinding prior to anodization resulted in larger cavity sizes and lengths, attributed to microstructural variations induced by grinding. Grinding also exposed areas with slower solidification rates, fostering a homogeneous Al phase that facilitated enhanced oxide growth. Moreover, the formation of oxide was directly correlated with the presence of alloying elements, particularly silicon particles, which influenced the presence of the unanodized aluminium regions. Full article

SiCp/Al composites offer the advantages of lightweight construction, high strength, and corrosion resistance, rendering them extensively applicable across various domains such as aerospace and precision instrumentation. Nonetheless, the interfacial reaction between SiC and Al under high temperatures leads to degradation in material properties. In this study, the interface segregation energy and interface binding energy subsequent to the inclusion of alloying elements were computed through a first-principle methodology, serving as a dataset for machine learning. Feature descriptors for machine learning undergo refinement via feature engineering. Leveraging the theory of machine-learning-accelerated first-principle computation, six machine learning models—RBF, SVM, BPNN, ENS, ANN, and RF—were developed to train the dataset, with the ANN model selected based on R² and MSE metrics. Through this model, the accelerated computation of interface segregation energy and interface binding energy was achieved for 89 elements. The results indicate that elements including B, Si, Fe, Co, Ni, Cu, Zn, Ga, and Ge exhibit dual functionality, inhibiting interfacial reactions while bolstering interfacial binding. Furthermore, the atomic-scale mechanism elucidates the interfacial modulation of these elements. This investigation furnishes a theoretical framework for the compositional design of SiCp/Al composites. Full article