Severe wear is a frequent cause of failure in industrial machinery that lacks adequate surface protection. Iron-based alloys offer an attractive combination of hardness, fracture toughness, and low cost for addressing this problem. In this study, a CALPHAD-based thermodynamic approach was employed to design a novel Fe-M(Nb,Mo,Cr)-C-B alloy, which was cast and subsequently processed into powders by gas atomization. The powders showed a Hall flow rate of 27 s/50 g and an angle of repose of 26°. The alloy composition was determined by optical emission spectroscopy, X-ray fluorescence (Nb), and inductively coupled plasma mass spectrometry (B), while X-ray diffraction confirmed the presence of α-iron and complex borocarbide phases. SEM/EDS analysis revealed a spherical powder morphology and a refined, uniformly distributed borocarbide microstructure induced by rapid solidification. Electron backscatter diffraction indicated a near-random crystallographic texture, and grain orientation spread maps revealed increasing internal strain with decreasing particle size. Nanoindentation gave localized hardness values of approximately 1330–1590 HV0.0005, which decreased with increasing particle size. The refined borocarbide-reinforced microstructure, high localized hardness, and good flowability suggest that the developed powder is a candidate feedstock for wear-resistant coating applications, although its coating and wear performance remain to be verified.
Developing solid electrolytes with high rubidium (Rb) ion transport activity and reversible exchange capability is a crucial material pathway for electrically controlled alkali-metal atom supply in compact atomic clocks and atomic magnetometers. In this research, Rb was introduced into Na3Zr2Si2PO12 ceramics via molten-salt exchange and mixed-powder sintering to construct a Rb-functionalized NASICON solid electrolyte (Rb-ex NASICON). Its overall electrical transport was examined by electrochemical impedance spectroscopy, while its field-driven Rb migration and reversible electrochemical activity were evaluated in an electrochemical Rb atom source device using Rb-specific atomic absorption spectroscopy. Although Rb-ex NASICON exhibits a lower overall apparent conductivity than pristine NASICON (apparent activation energy: 0.44 eV), it generated a net Rb vapor density increment exceeding 2 × 1010 cm−3 under release bias—nearly two orders of magnitude higher than that of the pristine device (2.3 × 108 cm−3) under identical conditions. After sufficient Rb recovery loading, +5 V actuation yielded rapid net Rb density increments of 9 × 109 cm−3 at 1 s and 3.8 × 1010 cm−3 at 4 s, alongside stable release–recovery cycling via polarity switching. The results demonstrate that the Rb incorporated into NASICON is electrochemically active and capable of rapid, reversible transport, establishing Rb-ex NASICON as an effective solid electrolyte for electrochemical Rb atom source devices.
Monometallic metal–organic frameworks, MOF-2-Cu and MOF-2-Zn, were synthesized at room temperature and evaluated as heterogeneous catalysts for the esterification of isoamyl alcohol with acetic acid to produce isoamyl acetate. The materials were characterized by X-ray diffraction (XRD), FT-IR spectroscopy, nitrogen adsorption (BET), X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA). The analyses confirmed the formation of crystalline, porous MOF-2 materials, with an additional crystalline phase present in MOF-2-Cu. Catalytic performance was assessed at temperatures ranging from 95 to 115 °C. Both MOFs exhibited substantial catalytic activity, achieving maximum isoamyl alcohol conversions of 54.5% for MOF-2-Cu and 51.1% for MOF-2-Zn at 105 °C. Without a catalyst, conversion and yield did not exceed 22.2% and 16.5%, whereas Amberlyst 16 reached 76.9% and 71.4% at 115 °C, showing higher activity than the MOFs. The highest isoamyl acetate yields were observed at 115 °C, reaching 40.5% for MOF-2-Zn and 42.8% for MOF-2-Cu. Reusability studies indicated that both catalysts retained over 80% of their initial activity after three regeneration cycles. These results underscore the potential of MOF-2-Zn and MOF-2-Cu as heterogeneous catalysts for sustainable esterification processes.
Cu/Eu co-doped ZnO nanoparticles with the nominal composition Zn0.99−xCu0.01EuxO (x = 0.00–0.05) were synthesized using the sol–gel method to systematically investigate the influence of Eu incorporation on their structural, microstructural, and magnetic properties. X-ray diffraction (XRD) analysis combined with Rietveld refinement confirmed the predominance of the hexagonal wurtzite ZnO structure, with no detectable secondary crystalline phases within the detection limits of XRD. Crystallite size, lattice strain, stress, and deformation energy density were evaluated using the Debye–Scherrer method and three Williamson–Hall approaches: the Uniform Deformation Model (UDM), Uniform Stress Deformation Model (USDM), and Uniform Deformation Energy Density Model (UDEDM). The crystallite size estimated using the Debye–Scherrer method decreased from 41.13 nm at x = 0.00 to 34.35 nm at x = 0.04, indicating composition-dependent changes in crystal growth. Magnetization–field (M–H) and magnetization–temperature (M–T) measurements were performed between 10 and 300 K using a Physical Property Measurement System (PPMS). The magnetic measurements revealed predominantly paramagnetic behavior at room temperature and enhanced ferromagnetic-like interactions at low temperatures with increasing Eu incorporation. The novelty of this study lies in the combined evaluation of concentration-dependent lattice distortion, microstructural parameters, and magnetic behavior in Cu/Eu co-doped ZnO nanoparticles using complementary structural and magnetic characterization approaches. These findings provide insight into the relationship between dopant concentration, crystal defects, and magnetic interactions, which may inform the development of ZnO-based functional magnetic nanomaterials and their potential use in spintronic applications.
Al-modified V–Fe–O oxides were synthesized by a co-precipitation route followed by calcination to investigate the effect of controlled Al incorporation on phase evolution, microstructure, optical properties, electronic structure, and visible-light-assisted photocatalytic activity. X-ray diffraction revealed a pronounced non-linear evolution of the V–Fe–O framework with increasing Al content, with intermediate Al incorporation promoting enhanced crystallinity and the development of additional diffraction features tentatively associated with a V2O3-related secondary phase. The corresponding microstructural evolution was confirmed by scanning electron microscopy, where the intermediate composition exhibited a distinct morphology characterized by well-developed crystalline domains. This sample also displayed the highest Brunauer–Emmett–Teller (BET) surface area (80 m2 g−1), indicating substantial modification of the textural properties. Diffuse reflectance measurements showed a reduction in the optical band gap from 2.50 eV for the undoped sample to 2.27 eV at the intermediate Al content, extending the optical response toward the visible region. Electron spin resonance (ESR) measurements further revealed pronounced changes in resonance linewidth and line shape, consistent with modifications in the local magnetic environment and the possible stabilization of mixed vanadium oxidation states. Under visible-light irradiation from commercial light-emitting diode (LED) sources, the intermediate Al-modified sample exhibited the highest photocatalytic activity, achieving approximately 95% degradation of Methyl Green within 120 min, compared with about 28% for the undoped oxide. The enhanced photocatalytic response is attributed to the combined effects of improved crystallinity, increased accessible surface area, band-gap narrowing, and Al-induced phase and electronic-structure reconstruction. These findings demonstrate that controlled Al incorporation provides an effective route for tuning the structure–property relationships of V–Fe–O oxides and enhancing their visible-light-assisted photocatalytic performance.
