Search Results (25)

In the present study, our emphasis was directed towards the fabrication process of long multi-core superconducting wires, each spanning several hundred meters. These wires feature an in situ MgB₂ core, an ex situ MgB₂ barrier, and a copper shield. The cost-effectiveness of these constituent materials, coupled with a judicious arrangement of internal components, facilitates the utilization of an economical shielding material for the resulting wire. Our ongoing efforts have successfully yielded several hundred-meter-long wire sections possessing favorable superconducting characteristics, making them suitable for self-field applications, such as direct current (DC) power lines. Full article

In the present study, composites incorporating NiO-Co₃O₄ (NC) and CuO-NiO-Co₃O₄ (CNC) as active electrode materials were produced through the hydrothermal method and their performance was investigated systematically. The composition, formation, and nanocomposite structure of the fabricated material were characterized by XRD, FTIR, and UV–Vis. The FE-SEM analysis revealed the presence of rod and spherical mixed morphologies. The prepared NC and CNC samples were utilized as supercapacitor electrodes, demonstrating specific capacitances of 262 Fg⁻¹ at a current density of 1 Ag⁻¹. Interestingly, the CNC composite displayed a notable long-term cyclic stability 84.9%, which was observed even after 5000 charge–discharge cycles. The exceptional electrochemical properties observed can be accredited to the harmonious effects of copper oxide addition, the hollow structure, and various metal oxides. This approach holds promise for the development of supercapacitor electrodes. These findings collectively indicate that the hydrothermally synthesized NC and CNC nanocomposites exhibit potential as high-performance electrodes for supercapacitor applications. Full article

The conversion efficiency of 800 nm, 65 fs radiation toward high-order harmonic generation (HHG) in laser-induced plasmas containing spherical and non-spherical nanoparticles (NPs) produced during the laser ablation of different metals in water using 1064 nm, 70 ps pulses was analyzed. Non-spherical NPs of different forms (triangle, cubic, bowtie, rod, rectangular, ellipsoid, etc.) were synthesized during the aging of some spherical NPs (In, Al, and Cu) in water. These NPs were then dried on the glass substrates and ablated to produce plasmas comprising nanostructured species of different morphologies. It was shown that harmonic generation in all synthesized non-spherical NPs was less efficient by a factor of at least five than in the initial spherical NP. Meanwhile, the spherical NPs that maintained the morphology state during aging (Ni, Ag, Mn, and Au) showed almost similar HHG conversion efficiency compared to the fresh spherical NPs. In all cases, the HHG conversion efficiency using spherical and non-spherical nanoparticles was notably larger compared to the atomic and ionic single-particle plasmas of the same elemental composition. NP plasmas demonstrated featureless harmonic distributions, contrary to the indium and manganese atomic/ionic plasmas, when the resonance enhancement of harmonics was observed. Full article

Bacterial pathogens cause pain and death, add significantly to the expense of healthcare globally, and pose a serious concern in many aspects of daily life. Additionally, they raise significant issues in other industries, including pharmaceuticals, clothing, and food packaging. Due to their unique properties, a great deal of attention has been given to biogenic metal nanoparticles, nanocomposites, and their applications against pathogenic bacteria. This study is focused on biogenic silver and copper nanoparticles and their composites (UL/Ag₂ O-NPS, Ul/CuO-NPs, and Ul/Ag/Cu-NCMs) produced by the marine green alga Ulva lactuca. The characterization of biogenic nanoparticles UL/Ag₂ O-NPS and Ul/CuO-NPs and their composites Ul/Ag/Cu-NCMs has been accomplished by FT-IR, SEM, TEM, EDS, XRD, and the zeta potential. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) experiments were conducted to prove antibacterial activity against both Gram-positive and Gram-negative bacteria and anti-biofilm. The FTIR spectroscopy results indicate the exiting band at 1633 cm⁻¹, which represents N–H stretching in nanocomposites, with a small shift in both copper and silver nanoparticles, which is responsible for the bio-reduction of nanoparticles. The TEM image reveals that the Ul/Ag/Cu-NCMs were hexagonal, and the size distribution ranged from 10 to 35 nm. Meanwhile, Ul/CuO-NPs are rod-shaped, whereas UL/Ag₂ O-NPS are spherical. The EDX analysis shows that Cu metal was present in a high weight percentage over Ag in the case of bio-Ag/Cu-NCMs. The X-ray diffraction denotes that Ul/Ag/Cu-NCMs, UL/CuO-NPs, and UL/Ag₂ O-NPS were crystalline. The results predicted by the zeta potential demonstrate that Ul/Ag/Cu-NCMs were more stable than Ul/CuO-NPs. The antibacterial activity of UL/Ag₂ O-NPS, Ul/Ag/Cu-NCMs, and UL/CuO-NPs was studied against eleven Gram-negative and Gram-positive multidrug-resistant bacterial species. The maximum inhibition zones were obtained with UL/Ag₂ O-NPS, followed by Ul/Ag/Cu-NCMs and Ul/CuO-NPs in all the tested bacteria. The maximum anti-biofilm percentage formed by E. coli KY856933 was obtained with UL/Ag₂ O-NPS. These findings suggest that the synthesized nanoparticles might be a great alternative for use as an antibacterial agent against different multidrug-resistant bacterial strains. Full article

The present investigation delves into the potential of vertical zone refining as an effective purification technique for achieving high-purity tin (Sn) metal. The utilization of vertical zone refining offers distinct advantages over traditional horizontal zone refining, as it allows for enhanced control over the molten zone and solid–liquid interface, ultimately leading to superior impurity separation efficiency. The present study reveals that the solute partition coefficients (k₀) of various impurity elements, such as Zn, Ag, Al, Mg, Ca, Ni, In, Co, Cu, As, Pb, Fe, and Bi, during the vertical zone refining process consistently demonstrate values below one. Notably, the partition coefficient of Sb deviates slightly from the others, being greater than one but approaching one. The authors achieve exceptional levels of purity in both the bottom and middle regions of the rod by subjecting the Sn melt to nine passes of vertical zone refining at a heating temperature of 405 °C and a downward pulling rate of 10 µm/s, resulting in purities exceeding 6N4. Furthermore, by evaluating the effective partition coefficients (k_eff), it was determined that impurity elements, such as Cu and Bi, closely approach their equilibrium partition coefficients, reaching values of approximately 0.492 and 0.327, respectively. To further enhance the purity of Sn metal and maximize product yield, we propose the utilization of electrolytic refining and vacuum distillation, with particular emphasis on the efficient separation of five specific elements, including Cu, Fe, As, Pb, and Sb. By elucidating these findings, this study not only contributes valuable insights into the efficacy of vertical zone refining as a purification technique for high-purity tin metal, but also offers important recommendations for refining strategies and impurity element separation. Full article

Investigating the relationship between the glass-forming ability (GFA), mechanical properties, and structure of metallic glasses is crucial to understanding the nature of the metallic glass state. In this study, the correlation among the atomic structure, electronic valence band, and properties have been studied using Zr₅₀Cu_44.5−xAl_5.5Ag_x (x = 0, 1.5, 3 at.%) bulk metallic glasses (BMGs). The results reveal that through the micro-addition of Ag, the GFA of Zr₅₀Cu_44.5Al_5.5 BMG can be enhanced; meanwhile, the critical diameter of Zr₅₀Cu_44.5Al_5.5 glass rods increases from approximately 2.5 mm to 5.0 mm with the addition of 3% Ag. Through the addition of Ag, the thermal stability of Zr₅₀Cu_44.5Al_5.5 BMG is improved, and the proportion of icosahedral-like clusters increases. The plasticity of the Zr₅₀Cu_44.5−xAl_5.5Ag_x (x = 0, 1.5, 3 at.%) BMGs decreased from 4.6% to 0.8% with the addition of Ag. The valence band spectrum of the Zr₅₀Cu_44.5−xAl_5.5Ag_x (x = 0, 1.5, 3 at.%) BMGs indicates that with the addition of Ag, the p-d hybridization near the Fermi level is enhanced, and the binding energy will move to a lower value. Full article

The luminescent properties of epitaxial Cu₂O thin films were studied in 10–300 K temperature range and compared with the luminescent properties of Cu₂O single crystals. Cu₂O thin films were deposited epitaxially via the electrodeposition method on either Cu or Ag substrates at different processing parameters, which determined the epitaxial orientation relationships. Cu₂O (100) and (111) single crystal samples were cut from a crystal rod grown using the floating zone method. Luminescence spectra of thin films contain the same emission bands as single crystals around 720, 810 and 910 nm, characterizing ${\mathrm{V}}_{\mathrm{O}}^{2+}$, ${\mathrm{V}}_{\mathrm{O}}^{+}$ and ${\mathrm{V}}_{\mathrm{Cu}}$ defects, correspondingly. Additional emission bands, whose origin is under discussion, are observed around 650–680 nm, while the exciton features are negligibly small. The relative mutual contribution of the emission bands varies depending on the thin film sample. The existence of the domains of crystallites with different orientations determines the polarization of luminescence. The PL of both Cu₂O thin films and single crystals is characterized by negative thermal quenching in the low-temperature region; the reason of this phenomenon is discussed. Full article

The demand for high-performance aluminum components drives research into the design of novel alloys that can be processed by laser-based additive manufacturing. In recent years, the addition of grain refiners proved to be an effective strategy to reduce the hot-cracking of high-strength Al alloys. In this study, the solidification and aging behavior of an Al2139 alloy doped with additions of Zr and Ti for L-PBF was investigated. These elements favored the formation of a fine-grained structure free of cracks. The formation of Al₃(Zr,Ti) inoculants was predicted by Scheil simulations and observed as cuboidal particles in the center of α-Al grains. The microstructure of the as-built material featured fine and fully equiaxed grains, which appeared comparatively finer at the edge (300–600 nm) and coarser (0.8–2.0 μm) at the center of the molten pools. In both cases, there was evidence of Cu and Mg micro-segregations at the grain boundaries. The microhardness of 109.7 HV_0.5 in the as-built state was increased to 186.1 HV_0.5 after optimized T4 heat treatment, responsible for the precipitation of many rod-shaped Zr- and Ti-based second phases and quasi-spherical Cu-, Mn-, and Fe-rich particles. Prolonged exposure carried out to simulate high-temperature service caused a drop in microhardness and marked modification of the microstructure, evidenced by the rearrangement and subsequent spheroidization of Cu- and Mg-rich particles at the grain boundaries. Full article

The precipitation behavior and mechanical properties for conventionally solidified Al-2.0wt.%Cu-2.0wt.%Mn alloy were studied. The supersaturated aluminum-based solid solution, CuAl₂, Al₆Mn and Al₂₀Cu₂Mn₃ phases of solidification origin were identified after casting. The high temperature ageing of as-cast samples (T5 treatment) in a temperature range of 300–350 °C led to the formation of the metastable θ′ phase and equiaxed precipitates of the quasicrystalline-structured I-phase. The θ′ phase demonstrated a high size stability in a studied temperature range with a mean length of ~300 nm and a mean thickness of ~24 nm. A mean size of the I-phase precipitates varied in a range of ~30–50 nm depending on the treatment regimes. The rod-shaped T-phase precipitates were formed with an increase in ageing temperature to 400 °C. Mechanical properties were analyzed at room temperature in a solid solution-treated state. The increased yield strength at room temperature and 200–300 °C were observed after ageing at 300 °C for 148 h. Full article

The present work studies a severe smog event that occurred in Delhi (India) in 2017, targeting the characterization of PM_2.5 and its deposition potential in human respiratory tract of different population groups in which the PM_2.5 levels raised from 124.0 µg/m³ (pre-smog period) to 717.2 µg/m³ (during smog period). Higher concentration of elements such as C, N, O, Na, Mg, Al, Si, S, Fe, Cl, Ca, Ti, Cr, Pb, Fe, K, Cu, Cl, P, and F were observed during the smog along with dominant organic functional groups (aldehyde, ketones, alkyl halides (R-F; R-Br; R-Cl), ether, etc.), which supported potential contribution from transboundary biomass-burning activities along with local pollution sources and favorable meteorological conditions. The morphology of individual particles were found mostly as non-spherical, including carbon fractals, aggregates, sharp-edged, rod-shaped, and flaky structures. A multiple path particle dosimetry (MPPD) model showed significant deposition potential of PM_2.5 in terms of deposition fraction, mass rate, and mass flux during smog conditions in all age groups. The highest PM_2.5 deposition fraction and mass rate were found for the head region followed by the alveolar region of the human respiratory tract. The highest mass flux was reported for 21-month-old (4.7 × 10² µg/min/m²), followed by 3-month-old (49.2 µg/min/m²) children, whereas it was lowest for 21-year-old adults (6.8 µg/min/m²), indicating babies and children were more vulnerable to PM_2.5 pollution than adults during smog. Deposition doses of toxic elements such as Cr, Fe, Zn, Pb, Cu, Mn, and Ni were also found to be higher (up to 1 × 10⁻⁷ µg/kg/day) for children than adults. Full article

Bimetallic solutions play a vital role in the growth and functionality of copper trimesate (Cu-BTC) metal–organic frameworks (MOFs). The effect of Ag⁺, Ca²⁺, Mn²⁺, Co²⁺, and Zn²⁺ on the growth of Cu-BTC was studied by fabricating M-Cu-BTC MOFs at room temperature using bimetallic M-Cu solutions. While Ag⁺ in the MOF had a rod-like morphology and surface properties, divalent cations deteriorated it. Moreover, unconventional Cu⁺ presence in the MOF formed a new building unit, which was confirmed in all the MOFs. Apart from Ag and Mn, no other MOF showed any presence of secondary cations in the structure. While Ag-Cu-BTC showed an improved H₂S uptake capacity, other M-Cu-BTC MOFs had superior organic pollutant adsorption behavior. Thus, we have demonstrated that the physicochemical properties of Cu-BTC could be modified by growing it in bimetallic solutions. Full article

The high cracking sensitivity of Al-Cu-Mg alloy limits its application in wire + arc additive manufacturing (WAAM). In this paper, a double-wire cold metal transfer (CMT) arc additive manufacturing system was applied. ER2319 and ER5183 wires were selected as feedstocks and a new type of high-strength, crack-free Al-Cu-Mg alloy was manufactured. T6 (solution and artificial aging) heat treatment was conducted to further improve the mechanical properties. The microstructure, the second phase, distribution of main alloy elements and fracture morphology of Al-Cu-Mg alloys in both as-deposited and T6 heat-treated conditions were analyzed by optical micrographs (OM), X-ray diffraction (XRD), and scanning electron microscopy (SEM), respectively. The micro-hardness and tensile properties of WAAM Al-Cu-Mg alloy in both as-deposited and T6 heat-treated conditions were tested. The results demonstrated that the microstructure of the as-deposited Al-Cu-Mg alloy was composed of short rod-shaped columnar grains, equiaxed grains in the inter-layer region, and coarsen equiaxed grains in the inner-layer region; most of the second phases were continuously distributed along the grain boundaries. After the T6 heat treatment, α(Al) grains became coarsened, most of second phases were dissolved, and the Cu and Mg elements were distributed homogeneously in the aluminum matrix. The micro-hardness and strength were significantly improved but the elongation was reduced. Full article

The study was designed to investigate the synergic effect of Ti and Sn in the active metal brazing of Al₂O₃ ceramic to copper brazed, using the multicomponent Ag-Cu-Zr filler alloy. Numerous fine and hexagonal-shaped rod-like ternary intermetallic (Zr, Ti)₅Sn₃ phase (L/D = 5.1 ± 0.8, measured in microns) were found dispersed in the Ag-Cu matrix of Ag-18Cu-6Sn-3Zr-1Ti alloy, along with the ternary CuZrSn intermetallic phases. An approximate 15° reduction in contact angle and 3.1 °C reduction in melting point are observed upon the incorporation of Ti and Sn in Ag-18Cu-3Zr filler. Interestingly, the interface microstructure of Al₂O₃/Cu joints brazed by using Ag-18Cu-6Sn-3Zr-1Ti filler shows a double reaction layer: a discontinuous Ti-rich layer consisting of (Cu, Al)₃(Ti, Zr)₃O, TiO, and in-situ Cu-(Ti, Zr) precipitates on the Al₂O₃ side and continuous Zr-rich layer consisting of ZrO₂ on the filler side. The shear strength achieved in Al₂O₃/Cu joints brazed with Ag-18Cu-6Sn-3Zr-1Ti filler is 31% higher, compared to the joints brazed with Ag-18Cu-6Sn-3Zr filler. Failure analysis reveals a composite fracture mode indicating a strong interface bonding in Al₂O₃/Ag-18Cu-6Sn-3Zr-1Ti filler/Cu joints. The findings will be helpful towards the development of high entropy brazing fillers in the future. Full article

In this study, a unified constitutive model has been developed for both yield strength and work hardening behaviour prediction of aluminium alloys with different types of precipitates during and after artificial ageing. The different type and dimensions of general precipitate shapes (sphere, plate, rod) have been classified and modelled by a primary dimension and aspect ratio, with which a general set of equations has been utilised to model the precipitates evolutions during ageing of various aluminium alloys. In addition, the effects of main microstructures on not only yield strength but also work-hardening behaviour of artificially aged aluminium alloys have been considered and modelled, based on which, a whole set of unified constitutive model considering both micro- and macro-properties for long-term artificial ageing of aluminium alloys has been proposed. Artificial ageing of two representative aluminium alloys (an Al-Mg-Si alloy AA6063 and an Al-Cu-Li alloy AA2198) has been adopted to show the capability and effectiveness of the developed model. The results show that the model can successfully predict the microstructures, yield strength and work hardening behaviour of various aluminium alloys with different precipitate types after long-term artificial ageing process, e.g., from 0 h to 500 h. It is believed that the model can be used for ageing of other aluminium alloys with dominant sphere, plate or rod-shaped precipitates. Full article

The paper reviews the results of the authors on the production of hybrid nanosystems based on liquid crystalline (LC) long-chain cyano(alkyl and alkoxy)biphenyls (5CB, 5OCB, and 8CCB) including nanosized metal species. The samples were obtained through the direct incorporation of metal (silver and copper) atoms and small clusters into mesogenic CB matrices via a low temperature co-condensation technique, and the formation of biligand metal complexes were revealed by FTIR and ESR-spectroscopy. The heating of the systems led to the controlled growth of metal clusters and nanosized metal particles of the definite size beginning from 1 up to 200 nanometers, and their highly-ordered assemblies stabilized in the solid and liquid crystalline phases. It is shown that supramolecular ordering in different LC phases of cyanobiphenyl matrices determines the size and shape of nanosized metal species that are formed in the systems under investigation, as well as the morphology of their aggregates. TEM and atomic force microscopy (AFM) data revealed the existence of orientationally-ordered nanostructures in the nematic phases of 5CB and 5OCB. The growth of quasi-fractal 2D-aggregates was shown for layer-structured smectic mesophase of 8CB. The UV–Visible spectra of hybrid metal–mesogenic nanosystems Ag-5CB and Cu-5CB that were incorporated into polymeric films revealed intensive plasmonic bands at 400–450 nm, similar to silver nanoparticles, and 540–650 nm, similar to copper nanoparticles. The increasing of the metal contents in the samples caused the growth of highly anisometric shaped metal rods, with the ratio of the length to the diameter being more than 10 and plasmonic bands at region of λ ≥ 650 nm. Full article