物理最新文献

This study investigates the effects of thermal and thermomechanical post-processing on the microstructure of laser powder bed fusion (LPBF)-fabricated 17 − 4 PH stainless steel. Three conditions were examined: as-built (AB), H900 aged, and combined hot-isostatic pressing (HIP) with H900 ageing (HIP+H900). The AB condition had exhibited columnar prior austenite grains, cellular solidification substructure, lath martensite, retained austenite, and a pronounced heterogeneous crystallographic texture. H900 ageing had promoted dislocation recovery, grain boundary stabilisation, and the formation of Cu-rich precipitates consistent with established precipitation behaviour reported in literature for this alloy. The HIP+H900 condition exhibited a predominantly martensitic microstructure containing approximately 7.5% FCC retained austenite as measured by EBSD, the remaining approximately 92.5% was indexed as BCC phase encompassing lath martensite and residual δ-ferrite. The increased retained austenite fraction in HIP+H900 relative to AB and H900 conditions was attributed to partial austenite retention on cooling from the HIP thermal cycle at 1160 °C. Among the conditions examined, HIP+H900 exhibited the most homogenous microstructure, with near-complete pore elimination, reduced crystallographic texture, and the lowest local lattice, making it suitable for applications demanding structural integrity and microstructural stability, including gun barrels, exhaust systems, and advanced automotive components.

Developing semiconductor heterojunctions with efficient interfacial charge transport is an important strategy for improving visible-light-driven photocatalysis. In this work, a Co₃O₄/g-C₃N₄ heterojunction was constructed through a hydrothermal–ultrasonic interfacial assembly approach to combine the complementary optical and electronic properties of spinel Co₃O₄ and polymeric g-C₃N₄. The primary scientific significance of the designed heterojunction lies in the modulation of interfacial charge transport and the extension of visible-light utilization, which collectively facilitate the generation and separation of photogenerated charge carriers. The structural, chemical, morphological, optical, and charge transport properties of the Co₃O₄/g-C₃N₄ were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible (UV-vis) spectroscopy, photoluminescence spectroscopy (PL), and transient photocurrent density measurements under visible light on/off cycles. The XRD, SEM, and XPS results confirm the formation of Co₃O₄/g-C₃N₄ with physical interfacial contact of spinel Co₃O₄ nanoparticles anchored over g-C₃N₄ flakes. The optical (UV-vis and PL) and photoelectrochemical investigations indicate the notable enhancement in visible-light response and photogenerated carrier transport, evidenced by the red-shifting of the absorption edge, a decreased optical bandgap, quenched PL intensity, and high photocurrent density for Co₃O₄/g-C₃N₄. The photocatalytic efficiency was evaluated by degrading the textile dye methylene blue (MB) and fluoroquinolone antibiotic levofloxacin (LF) as typical pollutants over the catalysts Co₃O₄, g-C₃N₄, and Co₃O₄/g-C₃N₄. The heterojunction demonstrated 95.6% MB (0.0428 min^− 1) and 91.4% LF (0.0411 min^− 1) degradation outperforming the pristine Co₃O₄ (56.2% MB degradation with k_MB = 0.0121 min^− 1 and 47.8% LF degradation with k_LF = 0.0084 min^− 1) and g-C₃N₄ (45.6% MB degradation with k_MB = 0.0077 min^− 1 and 30.7% LF degradation with k_MB = 0.005 min^− 1). The excellent reusability of Co₃O₄/g-C₃N₄ evaluated from five cycles of MB and LF degradation highlights the photocorrosion resistance and practical applicability of the fabricated heterojunction for the mineralization of organic compounds.

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We investigated the structural, mechanical, vibrational, thermal, electronic, and optical properties of amorphous Ge₂₅Sb₁₀Se₆₅ and Agₓ(Ge₂₅Sb₁₀Se₆₅)₁₀₀₋ₓ (x = 5, 10, and 15 at%) glasses using first-principles calculations. Structural analysis shows that increasing Ag concentration increases the cell volume, average bond length, and coordination number, accompanied by systematic changes in the local atomic environment. The effective bulk, shear, and Young’s moduli decrease with Ag incorporation, indicating reduced resistance to elastic deformation within the adopted approximation. The calculated sound velocities and Debye temperature also decrease across the composition series. Vibrational density-of-states analysis reveals a redistribution of vibrational spectral weight as Ag content increases. Electronic calculations using PBE/GGA and HSE06 show progressive narrowing of the calculated energy gap, with HSE06 values decreasing from 1.80 eV for the undoped model to 0.98 eV at 15 at% Ag. The optical response exhibits corresponding composition-dependent changes. The static dielectric constant, refractive index, and reflectivity decrease with increasing Ag concentration, while the optical band edge, principal absorption peak, and energy-loss peak shift toward lower photon energies. Overall, the calculations show correlated, composition-dependent changes in the structural, mechanical, vibrational, electronic, and optical responses of the investigated amorphous Ag–Ge–Sb–Se models, making them suitable for Infrared Photonic and Memory Applications.

In this study, a sulfur-containing lithium borophosphate glass system, 48 Li₂B₄O₇ + (50 − x) P₂O₅ + x Mn₂O₃ + 2S (x = 0–4 mol%), was prepared by the melt-quenching technique to investigate the effect of Mn₂O₃ incorporation on its structural, optical, and gamma-ray shielding properties. Structural modifications were examined by FTIR spectroscopy in the rang 4000 –400 cm^− 1, while optical properties were evaluated from UV–Vis measurements in the 200–750 nm range. Gamma-ray attenuation parameters were calculated using the XCOM database. Increasing Mn₂O₃ content results in higher glass density and systematic modifications of the borate–phosphate network, including an increase in the relative BO₃ contribution. The optical band gaps decrease with increasing Mn₂O₃ content, whereas the Urbach energy increases, indicating enhanced localized disorder and modification of the electronic structure. At 0.662 MeV, the mass attenuation coefficient increases from 0.0817 to 0.0906 cm²/ g, while the half-value layer decreases from 3.67 to 3.17 cm. These results demonstrate that Mn₂O₃ incorporation provides an effective means of tuning the structural, optical, and radiation-shielding characteristics of sulfur-containing lithium borophosphate glasses, highlighting their potential for multifunctional optical and transparent radiation-shielding applications.

Cobalt-based oxides are promising candidates for advanced dielectric applications due to their versatile structural and electronic properties. In this work, we investigate the effect of antimony (Sb) doping on the structural and dielectric characteristics of Co₃O₄. A series of Sb-doped Co₃O₄ compounds was synthesized via solid-state reaction and characterized using X-ray diffraction, dielectric spectroscopy, and X-ray absorption techniques. X-ray diffraction analysis indicates that the solubility limit of Sb in Co₃O₄ is reached for dopant concentrations exceeding x = 0.3. Dielectric measurements reveal a significant increase in permittivity with temperature, accompanied by Maxwell-Wagner-type relaxation. X-ray absorption near-edge structure (XANES) analysis suggests that Sb incorporation modifies the local electronic environment due to the formation of oxygen vacancies, while extended X-ray absorption fine structure (EXAFS) results confirm the preservation of the Co₃O₄ framework with subtle changes in bond lengths and local disorder. Notably, Sb doping alters Co-O-Co bonding by inducing changes in bond distances. Overall, the dielectric response is strongly tuneable with Sb content, frequency, and temperature, highlighting the potential of Sb-doped Co₃O₄ for the design of functional dielectric materials.

Vector-like leptons (VLLs) are well-motivated candidates for physics beyond the standard model. We investigate the sensitivity of the 6 TeV muon collider to the neutral doublet VLL (denoted by N) via its pair production in an SU(2)(_L) doublet model with hypercharge (Y=-frac{1}{2}). Assuming mixing with muons, we study the subsequent decay (Nrightarrow W^+ mu ^-) and analyze two representative signals, namely (4j2mu ) and (2ell 2mu Ehspace{-5.83328pt}/), arising from the hadronic and leptonic decays of the W boson, respectively. The signal and background events are simulated within a Monte Carlo framework, and a cut-based analysis is performed at the 6 TeV muon collider with an integrated luminosity (mathcal {L}=4) ab(^{-1}) for the unpolarized and polarized beam configurations, ((P_{mu ^+},P_{mu ^-})=(0,0)) and ((P_{mu ^+},P_{mu ^-})=(-1,1)). We consider VLL masses in the range of (1300{-}2980) GeV and evaluate the corresponding search sensitivity. Our results show that the 6 TeV muon collider could provide strong sensitivity to neutral doublet VLLs through the (4j2mu ) and (2ell 2mu Ehspace{-5.83328pt}/) signals, particularly for the idealized fully polarized beam configuration, under the detector, polarization, luminosity and background assumptions adopted in this analysis.

The klystron amplifier driven by an intense relativistic electron beam (IREB) is a crucial technological approach for generating high-power microwave (HPM) radiation. However, a fundamental conflict exists between low-magnetic-field operation and high-power output: increasing the radiation power requires enhancing the beam power and modulation depth, which imposes stringent demands on both the guiding magnetic field strength and the device’s power handling capacity. To address this conflict, this paper optimizes the design of a coaxial multi-beam relativistic klystron amplifier by focusing on the beam-wave interaction process between the IREB and the high-frequency structure. Through the synergistic design of cascaded single-gap bunching cavities and a non-uniform output cavity, simultaneous improvements in electron beam modulation depth and microwave extraction efficiency are achieved. Three-dimensional PIC simulation results show that under the conditions of an injection power of 19.7 kW, a guiding magnetic field of 0.37 T, a beam voltage of 780 kV, and a beam current of 13 kA, the device generates HPM radiation with an output power of 3.97 GW, an efficiency of 39.2%, and a gain of approximately 53 dB. Parameter sensitivity analyses demonstrate typical amplifier characteristics and stable operation under low magnetic field conditions. The results offer a potential new technical path for the development of compact HPM radiation sources.

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