Applied Physics A最新文献

Modification of titanium surfaces using a nanosecond Nd:YAG laser (λ = 532 nm) was performed in an aqueous medium. The influence of water compared to air was investigated. Standalone lines of laser impacts with different scanning rates, and laser-treated surfaces with a constant hatch between lines were studied by optical microscopy, SEM–EDS, Raman spectroscopy and XRD. Static contact angles of water and ethylene glycol in laser-treated surfaces were also measured. The standalone laser lines developed a wavy topography with erased contours of the melted zones. A TiO surface layer formed under all the conditions tested, while Ti₂O₃ formed progressively with decreasing scanning rates. EDS analysis of standalone lines showed a higher amount of oxygen compared to treatments in air. Laser-treated surfaces evolved, by decreasing the scanning rate, from goldish TiO-covered to dark surfaces covered with a Ti₂O₃–TiO mixture. TiO₂ was not found in any case in surfaces treated in water, while it is commonly found for treatments in air. Amorphous TiO₂ nanoparticles formed in the laser plume remained in the water medium. The roughness of laser-treated surfaces in water was much lower than in air. Their wettability was controlled by the surface chemical composition. The lowest static contact angles, 5° for water and 0° for ethylene glycol, were found for surfaces containing a Ti₂O₃–TiO mixture. Thermodynamic calculations carried out with the CEA2 program enabled to propose a scenario for the oxidation process in aqueous medium, which explains the dominance of TiO and Ti₂O₃ phases in laser-treated surfaces.

In this study, a one-dimensional ternary photonic crystal (1D TPC) with a defect layer is proposed and theoretically demonstrated as a sensor for detecting seawater salinity. Seawater is introduced as a defect layer inserted at the middle of 1D TPC, breaking the structural symmetry and thereby generating a defect mode within the photonic band gap. By utilizing the transfer matrix method (TMM), theoretical results indicate that the peak wavelength of the defect mode in the band gap is linearly proportional to salinity, namely, the resonant peak is red-shift (blue-shift) with increasing (decreasing) the salinity. Consequently, seawater salinity is accurately determined by tracking the peak wavelength of the defect mode. Under conditions of a defect layer thickness of 850 nm, a temperature of 25 °C, and normal incidence, an ultrahigh sensitivity of 2.687ⅹ10⁵ nm/RIU is achieved when the salinity alternates between 35‰ and 25‰. Additional performance parameters such as a quality factor (Q) of 1.135ⅹ10⁸, a figure of merit (FOM) of 1.675ⅹ10¹⁰ RIU^− 1, and a limit of detection (LOD) of 2.985ⅹ10^− 12 RIU are achieved at 35‰ salinity. Under oblique incidence, the defect mode induced by the seawater defect layer shifts to shorter wavelength as the incident angle increases. While the incident angle varies from 0⁰ to 80⁰, the Q factor of the defect mode remains on the order of 10⁸ for the TE polarized mode. In contrast, the Q value gradually decreases with increasing incident angle for the TM polarized mode. This research demonstrates that the 1D TPC based sensor for salinity detection offers significant advantages for advancing ocean engineering development.

This study develops a two-phase lattice Boltzmann model (LBM) to investigate the multiphysics coupling behavior of TiC/Ti6Al4V metal matrix nanocomposites (MMNCs) subjected to a moving annular laser heat source. The model integrates nanoparticle–fluid interactions and heat transfer to elucidate the influence of nanoparticles on molten pool. An innovative formulation is proposed for calculating the nanoparticle-induced dynamic viscosity, while an improved estimation method is adopted for the surface tension coefficient; moreover, a local nanoparticle volume fraction model is introduced to enhance the spatial accuracy of particle–melt interaction representation. The simulation results reveal that the annular laser generates a characteristic saddle-shaped molten pool, where the rear zone exhibits enhanced depth due to localized heat accumulation and convective recirculation. Incorporating TiC nanoparticles increases the melt zone (MZ) size while suppressing the heat-affected zone (HAZ), attributed to interfacial thermal resistance and viscosity-induced flow retardation. Force analysis indicates that the drag force dominates nanoparticle motion, whereas the thermophoretic force—though weaker—plays a crucial role in modulating migration near regions of steep temperature gradients. Nanoparticles exhibit a pronounced tendency to accumulate on the lateral sides of the laser-irradiated region, governed by the stronger drag force and weakened thermophoretic drive in these peripheral zones relative to the low-drag, high-thermophoresis core. These findings provide a fundamental understanding of particle–melt interactions under annular laser irradiation and establish a theoretical framework for optimizing process parameters in additive manufacturing of nanoparticle-reinforced metal composites.

We have effectively developed a strategy to significantly alter the nonlinear SA (SA) behavior and achieve a transition from negative to positive photoresponse (NPR to PPR) in nanocomposite films (NCFs) composed of Molybdenum disulfide (MoS₂), ZnS, and poly(3,4-ethylenedioxythiophene): poly(4-styrenesulfonate) (PEDOT: PSS). This was achieved by controlling the concentration of ZnS. Different concentrations of ZnS are introduced into NCF to create films using a straightforward drop-casting procedure on the glass substrate. The refractive index (n) and extinction coefficient (k) of the fabricated NCFs were determined through analysis based on the Kramers-Kronig relations. Nonlinear optical studies indicate significant changes in the optical nonlinearity of pristine PEDOT: PSS when combined with MoS₂ and ZnS. In particular, the ZnS/MoS₂/PEDOT: PSS NCFs exhibit evidence of Pauli blocking, which contributes to an enhanced SA response within the composite system. It also noted a NPR to UV light exposure. This unique response is linked to the trapping and confinement of charges generated by the radiation. These results underscore the pronounced Saturable Absorption (SA) behavior and NPR, indicating strong potential for advancing research into the photoresponsive and nonlinear optical properties of NCFs.

Eu³⁺-doped borate and silicate glasses were synthesized via the melt-quenching method to explore their potential for advanced optoelectronic applications. Structural and optical analyses confirmed the amorphous nature and uniform Eu³⁺ distribution in both systems. Borate glasses exhibited stronger red emission, higher optical basicity, and better thermal stability, while silicate glasses showed longer lifetimes, higher refractive index, and broader gain bandwidths. Judd–Ofelt analysis revealed that Eu³⁺ concentration strongly influences emission intensity, asymmetry, and quantum efficiency. Co-modifiers such as ZnO, Li₂CO₃, and Pb₃O₄ enhanced Eu³⁺ dispersion and reduced non-radiative losses. These results indicate that borate glasses are promising for red LEDs and sensors, whereas silicate glasses are ideal for optical amplifiers, lasers, and white-light devices. The established structure property correlations provide a framework for designing efficient and the applications specific photonic materials for next generation optoelectronic technologies.

Lithium-sulphur batteries (Li-S) provide a higher capacity and energy density and their commercialization is limited by challenges such as poor cycling stability and rapid capacity degradation. In this study, sulphur/heteroatom-doped reduced graphene oxide/ (S-N, S-r GO) composite material is used to fabricate the cathode for Li-S batteries. Fourier transform infrared spectroscopy, X-ray diffraction, Scanning electron microscopy were used to analyse the materials. Electrochemical behaviour is tested in the workstation through different techniques. The fabricated CR2032 coin cell demonstrated a high voltage of 3.53 V and delivered specific capacity of 890.47 mA h/g at C/5 with a minimal polarization. The capacity is retained up to 74.96% for more than 50 cycles, while coulombic efficiency of 85.42%, suggesting incomplete charge transfer. These results highlight that S-N, S-r GO is more suitable to make the cathode for Li-S batteries, with further optimization required to enhance long-term stability and overall performance.

In this study, Ni₁₋ₓCuₓFe₂O₄ (x = 0.0, 0.2, 0.4) ferrites were synthesized by the conventional solid-state reaction method, sintered at 1100 °C for 10 h, and examined for their structural, magnetic, optical, and electrical properties. XRD confirmed the formation of a single-phase spinel structure, while SEM revealed grain morphology and porosity. FTIR spectra showed characteristic tetrahedral and octahedral vibrational bands, aiding in the evaluation of elastic properties. The optical band gap was determined from UV–Vis spectroscopy. VSM measurements indicated a decrease in saturation magnetization with increasing Cu content. AC conductivity exhibited normal dispersion behaviour, with small polaron hopping governing charge transport at higher frequencies, whereas DC conductivity increased with temperature, confirming semiconducting behaviour. A reduction in Curie temperature and activation energy with Cu substitution was observed. These findings provide insight into tuning the magnetic and semiconducting properties of Ni–Cu ferrites for potential device applications. The systematic analysis highlights how Cu substitution influences cation distribution, magnetic ordering, band gap tuning, and conduction mechanisms, thereby providing new insights into tailoring Ni–Cu ferrites for multifunctional device applications such as magnetic sensors and spintronic components. A comprehensive understanding is crucial for designing ferrites with tunable magnetic and semiconducting behavior, which is less explored in existing literature for this composition range.

To avoid the failure of silicon nitride (Si₃N₄) materials caused by cracks or excessive friction, diamond films with Micron/Submicron/Nanometer multilayer structures were successfully prepared on Si₃N₄ substrate by hot filament chemical vapor deposition (HFCVD). Subsequently, MoS₂ films were deposited on the surface using RF magnetron sputtering technology to construct a multilayer diamond/MoS₂ self-lubricating film structure. The effects of Ar flow rate, sputtering power, and substrate temperature on the growth behavior of composite self-lubricating films were studied. By optimizing the sputtering parameters, the mechanical and friction properties of the films were optimized. Raman spectroscopy (Raman), X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM) were employed to characterize the structural quality, composition, surface morphology, and surface roughness of the material. At the same time, the tribological properties of the films were evaluated by friction and wear experiments. The experimental results indicate that a 40 sccm Ar flow, 250 W sputtering power, and a substrate temperature of 300 °C are the optimal combination of process parameters. The multilayer diamond/MoS₂ self-lubricating film prepared under these conditions exhibits high crystallinity, low surface roughness, and good interfacial bonding ability, resulting in a high hardness (21.16 MPa), elastic modulus (176.33 MPa), low friction coefficient (0.042) and a low wear rate (1.931 ± 0.043 × 10^− 6 mm³/N·m). Under a load of 15 N, the wear resistance remains stable after friction for 45 min, indicating a promising application prospect for wear-resistant, self-lubricating Si₃N₄ bearings. The performance control of multilayer diamond/MoS₂ self-lubricating film on Si₃N₄ substrate has important theoretical significance and engineering application value.

Rare-earth-doped glasses are at the forefront of photonic applications due to their outstanding optical tunability, yet the challenge of achieving efficient white light emission through eco-friendly and cost-effective glass hosts has persisted. Here in the present investigation, (Ce³⁺, Dy³⁺) co-doped Li₂O + CaO + B₂O₃ glasses have been fabricated via the melt-quenching method and systematically studied to achieve white light emission. The structural studies by XRD and Raman demonstrate the amorphous nature of the prepared glasses. The physical properties of the glass matrix were significantly improved by the addition of Dy³⁺ ions, as demonstrated by a decrease in interionic distance, an increase in density from 2.72 to 2.80 g/cm³ and refractive index from 1.615 to 1.6215. The UV-visible-NIR optical absorption spectra showed characteristic Dy³⁺ absorption bands, a significant rise in the indirect band gap from 2.79 to 2.86 eV, and a drop in Urbach energy from 0.181 to 0.164 eV, all of which suggested less structural disorder in the glass network. The PL analysis exhibits distinctive emissions under UV excitation, with dominating yellow (∼575 nm) and blue (∼480 nm) emission peaks, which get stronger as the concentration of Dy₂O₃ increases. This also demonstrates an efficient energy transfer (ET) between Ce³⁺ ions as sensitisers to Dy³⁺ ions as acceptors, supported by the fluorescence lifetime decay studies, which show the reduced lifetime ascribed to dipole–dipole interactions as outlined by the Inokuti–Hirayama model (S = 6). In essence, (Ce³⁺, Dy³⁺) co-doped glasses with a matrix of Li₂O + CaO + B₂O₃ exhibit effective white light emission under UV light exposure. Among the investigated glasses, the glass composition featuring 0.5 mol% Ce³⁺ and 1.0 mol% Dy³⁺ demonstrates exceptionally well-balanced chromaticity coordinates, leading to a suitable choice for white light-emitting device applications.

Doping GaS single crystals with Yb atoms introduces donor and acceptor levels, which dramatically change the electrical conductivity in the temperature range 125–300 K. Additional defect levels are added by gamma irradiation; at lower doses (20 krad), it reduces conductivity and shifts the thermal quenching temperature where conductivity decreases due to non-radiative recombination of carriers, while at larger doses (50 krad and above), it significantly alters both conductivity and activation energies. Conductivity is enhanced by light exposure (λ = 445 nm), demonstrating the intricate relationships between radiation-induced defects, temperature effects, and Yb doping.