Search Results (143)

The present article aims to develop a technological scheme for processing zinc ferrite residue, which typically forms during the leaching of zinc calcine. This semi-product is currently processed through the Waelz process, the main disadvantage of which is the loss of precious metals with the Waelz clinker. The experimental results of numerous experiments and analyses have verified a technological scheme including the following operations: sulfuric acid leaching of zinc ferrite residue under atmospheric conditions; autoclave purification of the resulting productive solution to obtain hematite; chloride leaching of lead and silver from the insoluble residue, which was produced in the initial operation; and cementation with zinc powder of lead and silver from the chloride solution. Utilizing such an advanced methodology, the degree of zinc leaching is 98.30% at a sulfuric acid concentration of 200 g/L, with a solid-to-liquid ratio of 1:10 and a temperature of 90 °C. Under these conditions, 96.40% Cu and 92.72% Fe form a solution. Trivalent iron in the presence of seeds at a temperature of 200 °C precipitates as hematite. In chloride extraction with 250 g/L NaCl, 1 M HCl, and a temperature of 60 °C, the leaching degree of lead is 96.79%, while that of silver is 84.55%. In the process of cementation with zinc powder, the degree of extraction of lead and silver in the cement precipitate is 98.72% and 97.27%, respectively. When implementing this scheme, approximately 15% of the insoluble residue remains, containing 1.6% Pb and 0.016% Ag. Full article

This study systematically evaluates the influence of copper (Cu) addition in gas-shielded solid wires on the microstructure and cryogenic toughness of X80 pipeline steel welds. Welds were fabricated using solid wires with varying Cu contents (0.13–0.34 wt.%) under identical gas metal arc welding (GMAW) parameters. The mechanical capacities were assessed via tensile testing, Charpy V-notch impact tests at −20 °C and Vickers hardness measurements. Microstructural evolution was characterized through optical microscopy (OM), scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). Key findings reveal that increasing the Cu content from 0.13 wt.% to 0.34 wt.% reduces the volume percentage of acicular ferrite (AF) in the weld metal by approximately 20%, accompanied by a significant decline in cryogenic toughness, with the average impact energy decreasing from 221.08 J to 151.59 J. Mechanistic analysis demonstrates that the trace increase in the Cu element. The phase transition temperature and inclusions is not significant but can refine the prior austenite grain size of the weld, so that the total surface area of the grain boundary increases, and the surface area of the inclusions within the grain is relatively small, resulting in the nucleation of acicular ferrite within the grain being weak. This microstructural transition lowers the critical crack size and diminishes the density for high-angle grain boundaries (HAGBs > 45°), which weakens crack deflection capability. Consequently, the crack propagation angle decreases from 54.73° to 45°, substantially reducing the energy required for stable crack growth and deteriorating low-temperature toughness. Full article

This study investigates the hot tensile behavior and fracture characteristics of 05Cr17Ni4Cu4Nb stainless steel through isothermal tensile tests conducted under various deformation parameters. An improved Cockroft & Latham (C&L) damage model, incorporating the effects of temperature and strain rate, was developed to quantitatively evaluate the influence of these parameters on the high-temperature deformation behavior of 05Cr17Ni4Cu4Nb stainless steel. Microstructural analysis revealed the features of ductile fracture and provided insights into the mechanism by which δ-ferrite influences microvoid evolution. These findings contribute to a deeper understanding of the high-temperature deformation behavior of 05Cr17Ni4Cu4Nb stainless steel and provide practical guidance for optimizing hot forming parameters in industrial applications. Full article

The CASTRIP process is an innovative method for producing flat rolled low-carbon and low-alloy steel at very thin thicknesses. By casting steel close to its final dimensions, enormous savings in time and energy can be realized. In this paper, an ultra-high-strength low-alloy corrosion-resistant steel was produced through the CASTRIP process. Microstructure and properties were investigated by means of optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), laser confocal microscopy (LSCM), electron backscattered diffraction (EBSD), and tensile testing. The results show that the microstructure is mainly composed of polygonal ferrite, bainite ferrite, and acicular ferrite. The bainite ferrite forms parallel lath bundles nucleating at austenite grain boundaries, propagating perpendicularly into the parent grains. The acicular ferrite exhibits a cross-interlocked morphology preferentially nucleating at oxide/sulfide inclusions. Microstructural characterization confirms that the phase transformation of acicular ferrite and bainite ferrite introduces high-density dislocations, identified as the primary strengthening mechanism. Under the CASTRIP process, corrosion-resistant elements such as Cu, P, Sb, and Nb are completely dissolved in the matrix without grain boundary segregation, thereby contributing to solid solution strengthening. Full article

This study investigates the influence of calcination temperature on the structural, morphological, and optical properties of Cd_0.6Mg_0.2Cu_0.2Fe₂O₄ spinel ferrites synthesized via the sol–gel method. By varying the calcination temperatures (950 °C and 1050 °C), we analyze changes in crystallinity, cation distribution, and energy band gap using X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and UV–visible spectroscopy. The results indicate that increasing calcination temperature enhances crystallinity and increases particle size while reducing the optical band gap energy. XPS analysis confirms shifts in cation site occupancy and an increase in oxygen vacancies at higher temperatures, which are crucial for charge carrier dynamics. Photocatalytic performance, evaluated through methylene blue degradation under UV light, improves with increasing calcination temperature due to enhanced charge separation and reduced recombination. These findings underscore the critical role of calcination temperature in optimizing spinel ferrites for environmental applications, particularly in wastewater treatment. Full article

In this study, copper ferrite nanoparticles, a type of ferrimagnetic spinel ferrite, were synthesized using the sol-gel auto-combustion method with three different fuels: citric acid, urea, and ethylene glycol. The crystal structures of the synthesized samples were analyzed using X-ray diffraction (XRD), and the growth of secondary phases like Fe₂O₃ and CuO for samples prepared with urea and ethylene glycol indicated the presence of impurities. Additionally, we observed that the particle size varied significantly with the type of fuel, being the smallest for citric acid and the largest for urea. The electrical and magnetic properties showed strong correlations with the particle size and the presence of impurities. In particular, the optical band gap values, derived from UV-Vis spectroscopy, varied significantly with the choice of fuel, ranging from 2.06 to 3.75 eV. The highest band gap of 3.75 eV was observed in samples synthesized with citric acid. Magnetic properties were measured using a vibrating sample magnetometer (VSM), and it was found that the copper ferrite synthesized with citric acid exhibited the highest values of magnetic saturation and coercivity. These findings demonstrate that the choice of fuel during the synthesis process has substantial impacts on the structural, optical, and magnetic properties of CuFe₂O₄ nanoparticles. Full article

With the global shift in energy structure and the advancement of the “double carbon” strategy, methanol has gained attention as a clean low-carbon fuel in the engine sector. However, the corrosion–wear coupling failure caused by acidic byproducts, such as methanoic acid and formaldehyde, generated during combustion severely limits the durability of methanol engines. In this study, we employed a systematic approach combining the construction of a corrosion liquid concentration gradient experiment with a full-load and full-speed bench test to elucidate the synergistic corrosion–wear mechanism of core friction pairs (cylinder liner, piston, and piston ring) in methanol-fueled engines. The experiment employed corrosion-resistant gray cast iron (CRGCI), high chromium cast iron (HCCI), and nodular cast iron (NCI) cylinder liners, along with F38MnVS steel and ZL109 aluminum alloy pistons. Piston rings with DLC, PVD, and CKS coatings were also tested. Corrosion kinetic analysis was conducted in a formaldehyde/methanoic acid gradient corrosion solution, with a concentration range of 0.5–2.5% for formaldehyde and 0.01–0.10% for methanoic acid, simulating the combustion products of methanol. The results showed that the corrosion depth of CRGCI was the lowest in low-concentration corrosion solutions, measuring 0.042 and 0.055 μm. The presence of microalloyed Cr/Sn/Cu within its pearlite matrix, along with the directional distribution of flake graphite, effectively inhibited the micro-cell effect. In high-concentration corrosion solutions (#3), HCCI reduced the corrosion depth by 60.7%, resulting in a measurement of 0.232 μm, attributed to the dynamic reconstruction of the Cr₂O₃-Fe₂O₃ composite passive film. Conversely, galvanic action between spherical graphite and the surrounding matrix caused significant corrosion in NCI, with a depth reaching 1.241 μm. The DLC piston coating obstructed the permeation pathway of formate ions due to its amorphous carbon structure. In corrosion solution #3, the recorded weight loss was 0.982 mg, which accounted for only 11.7% of the weight loss observed with the CKS piston coating. Following a 1500 h bench test, the combination of the HCCI cylinder liner and DLC-coated piston ring significantly reduced the wear depth. The average wear amounts at the top and bottom dead centers were 5.537 and 1.337 μm, respectively, representing a reduction of 67.7% compared with CRGCI, where the wear amounts were 17.152 and 4.244 μm. This research confirmed that the HCCI ferrite–Cr carbide matrix eliminated electrochemical heterogeneity, while the DLC piston coating inhibited abrasive wear. Together, these components reduced the wear amount at the top dead center on the push side by 80.1%. Furthermore, mismatches between the thermal expansion coefficients of the F38MnVS steel piston (12–14 × 10⁻⁶/°C) and gray cast iron (11 × 10⁻⁶/°C) resulted in a tolerance exceeding 0.105 mm in the cylinder fitting gap after 3500 h of testing. Notably, the combination of a HCCI matrix and DLC coating successfully maintained the gap within the required range of 50–95 μm. Full article

Based on the flexible adjustment of the seven-wire, this study will assemble a new toughened seven-wire which is combined with a common single welding wire and the existing welding wire containing ductile alloy element (Ni element), and the microstructure properties, mechanical properties and toughening mechanism of the welding seams were studied. The results show that the microstructure of the four combinatorial seven-wire welding seams is mainly composed of coarse proeutectoid ferrite (PF) and fine acicular ferrite (AF). Among them, the core of inclusions that induce AF nucleation and growth are mainly composed of Al, Ti, Si, and Mn-based oxides, and the edge of inclusions is mainly composed of Mn and Cu sulfides (MnS, CuS). The addition of Ti compounds further promotes AF nucleation. This is also a reason why the impact toughness of the combinatorial seven-wire W2/W3 welding seams is higher than that of other combinatorial seven-wire welding seams, but the impact toughness of the rich Ni seven-wire can meet the standard requirements of the China Classification Society (CCS). Among the four combinatorial seven-wire welding seams, the proportions of large angle grain boundaries (grain orientation difference ≥ 15°) that improve the ability of materials to prevent brittle fracture are 65.9%, 68.8%, 66.0%, 61.7%, respectively, that is, the larger proportion of large angle grain boundaries in combinatorial seven-wire W2 welding seams (Ni content is 0.0897%) is one of the reasons for the higher impact toughness of the welding seams. With the increase of Ni content in the welding seam, the AF content first increased and then decreased, the yield strength and tensile strength increased, and the elongation and section shrinkage first increased and then decreased. When the combinatorial seven-wire W2/W3 was used, the welding seam plasticity was the best. Full article

The reduction of unfriendly 4-nitrophenol to make it unimpactful with the environment (4-aminophenol) was carried out using the metastable form of copper ferrite (CuFe₅O₈) synthesized by the co-precipitation of metal nitrate salts, an efficient method with inexpensive and abundant starting materials. The samples were obtained by calcination at various temperatures ranging from 600 °C to 900 °C. The material characterizations, including X-ray diffraction, N₂ adsorption/desorption, scanning electron microscope, X-ray absorption spectroscopy, and ultraviolet–visible spectrometry, were employed to identify the detailed structures and describe their correlations with catalytic activities. The X-ray diffraction and X-ray absorption spectroscopy analyses revealed the presence of mixed CuFe₅O₈ and copper oxide phases, where the formers are rich in Cu²⁺, Fe²⁺, and Fe³⁺ ions. The electron transfer between Cu²⁺, Fe²⁺, and Fe³⁺ led to the high efficiency of the catalytic reaction of the synthesized copper ferrites. Especially for the sample calcined at 600 °C, the apparent kinetic constant (k) for a reduction of 4-nitrophenol was equal to 0.25 min⁻¹, illustrating nearly 100% conversion of 4-nitrophenol to 4-aminophenol within less than 9 min. Regarding the N₂ adsorption/desorption isotherms, the samples calcined at 600 °C have the highest specific Brunauer–Emmett–Teller (BET) surface area (15.93 m² g⁻¹) among the others in the series, which may imply the most effective catalytic performance investigated herein. The post-catalytic X-ray diffraction investigation indicated the stability of the prepared catalysts. Furthermore, the chemical stability of the prepared catalysts was confirmed by its reusability in five consecutive cycles. Full article

The dominant treatment process for removing heavy metals from industrial wastewater is chemical neutralisation precipitation using lime milk as a precipitation agent, resulting in a highly voluminous hydroxide sludge with a low heavy metal concentration. These sludges are predominantly landfilled, and the metals are lost to the circular economy. At the same time, metals are urgently needed as raw materials. A new approach is represented by the low-pressure, low-energy Specific Product-Oriented Precipitation process (SPOP). This approach, however, requires the adjustment of various reaction parameters for optimal operation. This study presents the impacts of the stirring rate during the reaction and the Fe concentration in the solution on the recovery of Cu from Cu-enriched electroplating wastewater. Three different recovery options are described: Option (1), the formation of CuO; Option (2), the generation of brochantite, a Cu-hydroxysulphate; and Option (3), the incorporation of Cu into ferrite. Tenorite (CuO) is precipitated at 40 °C reaction temperature at a low stirring rate of 100–200 rpm. At an accelerated stirring rate of 400–500 rpm, brochantite (Cu₄(OH)₆SO₄) is formed. With high Fe concentrations and a molar ratio of Cu:Fe of 1:2, Cu-ferrite (CuFe₂O₄) is the precipitation product. In any case, the achieved recovery rates in the treated wastewater are better than 99.9%. Full article

We have investigated the phase formation, microstructure, and permeability of stoichiometric and Fe-deficient Ni-Cu-Zn ferrites of composition Ni_0.30Cu_0.20Zn_0.50+zFe_2−zO_4−(z/2) with 0 ≤ z ≤ 0.06 sintered at 1000 °C in various oxygen partial pressures p_O2, which range from 0.21 atm down to 10⁻⁵ atm. The density of the sintered samples is almost independent of the p_O2, whereas the grain size of the Fe-deficient ferrites decreases in more reducing atmospheres. Stoichiometric ferrites show a regular growth of single-phase ferrite grains if sintered in air. Sintering at p_O2 ≤ 10⁻² atm leads to the formation of a small amount of Cu₂O at grain boundaries and triple points. Fe-deficient compositions (z > 0) form Cu-poor stoichiometric ferrites, which coexist with a minority CuO phase homogeneously distributed between the grains after sintering in air. At p_O2 ≤ 10⁻² atm, the CuO grain boundary phase starts to transform into Cu₂O, which concentrates at some triple points at p_O2 = 10⁻² atm, and it is more homogeneously distributed between the ferrite grains at the lower p_O2. Formation of the Cu oxide second phases is investigated using XRD, SEM, and EDX. The permeability at 1 MHz of the stoichiometric ferrites (z = 0) is between µ′ = 200 and µ′ = 300 within the studied range of the p_O2. The permeability at 1 MHz of the Fe-deficient samples decreases with the p_O2, e.g., from µ′ = 750 at p_O2 = 0.21 atm to µ′ = 320 at p_O2 = 10⁻⁵ atm for z = 0.02, respectively. Full article

To investigate the evolution of microstructure and mechanical properties in cold-rolled sheets of Ferritic Stainless Steel (FSS) during annealing, a series of annealing tests were performed on 00Cr21CuTi at different temperatures of 930, 990, and 1050 °C. The changes in microstructure at these annealing temperatures were characterized by optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electron back-scattered diffraction (EBSD). The influence of annealing temperature on mechanical properties was assessed utilizing a universal tensile testing machine and a laser confocal microscope. The results indicated a gradual decrease in yield strength and tensile strength with increasing annealing temperature, whereas elongation exhibited an upward trend. At an annealing temperature of 930 °C, the yield strength, tensile strength, and elongation of the steel were 251 MPa, 409 MPa, and 30.9%, respectively, with a high product of strength plastic 12.64 GPa·%. This result represented an optimal balance between comprehensive strength and plasticity. Full article

In this study, magnetic binary/ternary Zn_xCo_1−xFe₂O₄ (x = 0, 0.5, 1) nanoparticles were synthesized using a straightforward one-step microwave technique. To produce the Zn_xCo_1−xFe₂O₄ nanoparticles, iron (III) nitrate nonahydrate, zinc nitrate hexahydrate, and cobalt nitrate hexahydrate were used as metal sources, with urea used as the fuel and ammonium nitrate as the oxidizer. These materials were combined in an alumina crucible covered by a CuO jacket to absorb microwave energy and facilitate calcination. The thermal treatment involved placing the alumina crucible in a domestic microwave oven at 450 W for 30 min. The key strengths of this experimental strategy include its simplicity, cost-effectiveness, and rapidity, aligning with green chemistry principles. The synthesized nanoparticles were characterized using X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, a vibrating sample magnetometer (VSM), and Brunauer–Emmett–Teller (BET) analysis. XRD analysis confirmed the presence of the pure ferrite nanocrystalline phase. Scanning electron microscopy (SEM), employed with energy-dispersive X-ray spectroscopy (EDS), was used to study the surface morphology and analyze the elemental composition. The SEM analysis revealed that the synthesized magnetic nanoparticles had particle sizes ranging from 30 to 50 nm. Furthermore, we explored the potential use of these magnetic nanoparticles as photocatalysts for degrading organic pollutants such as methylene blue in aqueous solutions. Full article

Large-scale superconductor applications necessitate a superconducting matrix with pinning sites (PSs) that immobilize vortices at elevated temperatures and magnetic fields. While previous works focused on the single addition of nanoparticles, the simultaneous inclusion of different nanoparticles into a superconducting matrix can be an effective way to achieve an improved flux pinning capacity. The purpose of this study is to explore the influence of mixed-nanoparticle pinning, with the co-addition of non-magnetic (BaTiO₃; BT) and various types of magnetic spinel ferrite (MFe₂O₄, abbreviated as MFO, where M = Mn, Co, Cu, Zn, and Ni) nanoparticles, on the superconductivity and flux pinning performances of the high-temperature superconductor YBa₂Cu₃O_y (YBCO). An analysis of X-Ray diffraction (XRD) data of BT–MFe₂O₄-co-added YBCO samples showed the formation of an orthorhombic structure with Pmmm symmetry. According to electrical resistivity measurements, the emergence of the superconducting state below $T_c^{offset}$ (zero-resistivity temperature) was proven for all samples. The highest $T_c^{offset}$ value was recorded for the Y-BT-MnFO sample, while the minimum value was obtained for the Y-BT-ZnFO sample. Direct current (DC) magnetization results showed good magnetic flux pinning performance for all the co-added samples compared to the pristine sample but with some discrepancies. At 77 K, the values of the self-critical current density (self-$J_{cm}$) and maximum pinning force ($F_{pmax}$) for the Y-BT-MnFO sample were found to be eight times higher and seventeen times greater than those for the pristine sample, respectively. The results acquired suggested that mixing the BT phase with an appropriate type of spinel ferrite nanoparticles can be a practical solution to the problem of degradation of the critical current density of the YBCO material. Full article

Adsorption has emerged as a promising method for removing polyphenols in water remediation. This work explores chlorogenic acid (CGA) adsorption on zeolite-based magnetic nanocomposites synthesized from rice husk waste. In particular, enhanced adsorbing materials were attained using a hydrothermal zeolite precursor (Z18) synthesized from rice husk and possessing a remarkable specific surface area (217.69 m² g⁻¹). A composite material was prepared by immobilizing magnetic copper ferrite on Z18 (Z18:CuFe₂O₄) to recover the zeolite adsorbent. In addition, Z18 was modified (Z18 M) with a mixture of 3-aminopropyltriethoxysilane (APTES) and trimethylchlorosilane (TMCS) to improve the affinity towards organic compounds in the final nanocomposite system (Z18 M:CuFe₂O₄). While the unmodified composite demonstrated inconsequential CGA removal rates, Z18 M:CuFe₂O₄ could adsorb 89.35% of CGA within the first hour of operation. Z18 M:CuFe₂O₄ showed no toxicity for seed germination and achieved a mass recovery of 85% (due to a saturation magnetization of 4.1 emu g⁻¹) when an external magnetic field was applied. These results suggest that adsorbing magnetic nanocomposites are amenable to CGA polyphenol removal from wastewater. Furthermore, the reuse, revalorization, and conversion into value-added materials of agro-industrial waste may allow the opportunity to implement sustainability and work towards a circular economy. Full article