Applied Physics A最新文献

This study investigates the synthesis and characterization of a thioglycolic acid (TGA) functionalized magnetic graphene oxide nanocomposite (TGA/Fe₃O₄/GO) with enhanced nonlinear optical (NLO) properties for advanced optical applications. Comprehensive characterization confirmed the successful preparation of graphene oxide (GO) nanosheets, the incorporation of Fe₃O₄ nanoparticles onto the GO surface, and the effective attachment of a TGA ligand. Field-emission scanning electron microscopy (FESEM) images confirmed the formation of well-defined nanostructures, At the same time, X-ray diffraction (XRD) patterns verified the presence of the face-centered cubic (fcc) spinel phase of Fe₃O₄, with an average nanoparticle crystal size of approximately 10 nm. Raman spectroscopy indicated an increased I_D/I_G ratio (in both Fe₃O₄/GO and TGA/Fe₃O₄/GO) compared to GO affirming increased defect density induced by Fe₃O₄ decoration and subsequent TGA functionalization. The measured surface area and the saturation magnetization values of TGA/Fe₃O₄/GO nanocomposite were 57.24 m²/g and 11.90 emu/g, respectively. Furthermore, NLO characterization of the TGA/Fe₃O₄/GO nanocomposite using the Z-scan technique under continuous-wave (CW) 532 nm excitation reveals strong third-order nonlinear behavior. The open-aperture (OA) traces exhibit pronounced two photon absorption (TPA), reflected in nonlinear absorption (NLA) coefficients, (:beta:) on the order of (:{10}^{-3}:cm/W). Closed-aperture (CA) measurements show a clear peak–valley signature that increases with both power and concentration, confirming a positive nonlinear refractive (NLR) response and the occurrence of self-focusing, with (:{n}_{2}) values in the (:{10}^{-7}{cm}^{2}/W) range. The corresponding third-order susceptibilities (:left|{chi:}^{left(3right)}right|) in the range of (:{10}^{-6}left(esuright))indicate a highly responsive nonlinear system. The figures of merit ((:W>:1:)and (:T<:1)) further verify that the nanocomposite meets the criteria required for effective CW optical limiting and switching.

Graphical Abstract

The graphoepitaxial seeding provides a possibility of fabrication of epitaxial thin films of anisotropic materials with unusual orientation. This technique allows preparation of YBa₂Cu₃O_x (YBCO) thin films with c axis position close to the substrate plane - the high-tilt YBCO films - that may be applied for fabrication of scalable intrinsic Josephson structures. The structure of YBCO films deposited on 14–23º tilted-axes NdGaO₃ (NGO) substrates with pulsed laser deposition was studied with the X-ray diffraction techniques. Two orientations of YBCO grains, pseudo-c (001)_YBCO||(110)_NGO and pseudo-a (100)_YBCO||(110)_NGO (the high-tilt orientation), were observed. The dominant orientation of the film is set in the very beginning of deposition with overgrowth of the pseudo-c seeds with the pseudo-a grains or vice versa. The disorder in the top layer of the film rapidly increases with the volume part of pseudo-a grains, while the crystallinity and the mosaicity of the main layer are not affected by the film orientation. Symmetric (103) grain boundaries between the pseudo-c and pseudo-a grains dominate in the top layer. The pseudo-c grains experience a significant effect of the substrate-induced strain; the introduction of pseudo-a grains results in a relaxed structure. Secondary seeding of the pseudo-c grains is observed in thick films, grown with the vapor-liquid-solid mechanism. The lattice of such grains is completely strained by the bottom pseudo-a oriented layer.

The increasing demand for sustainable electronic devices requires biodegradable and flexible substrates. Conventional materials such as PI and PDMS are non-degradable and contribute to electronic waste (e-waste), highlighting the need for an eco-friendly alternative with high electrical conductivity and mechanical flexibility. In this study, konjac-glucomannan (KGM)-based laser-induced graphene (LIG) was used to demonstrate the feasibility of a fully degradable, flexible, and transparent substrate for sensors. LIG is synthesized by laser irradiation, to form a conductive graphene network. In addition, the formation mechanism of LIG was investigated by analyzing the carbon ring structure and gas evolution through ReaxFF molecular dynamics (MD) simulations in the temperature from 2000 to 3500 K. The simulation results confirmed the generation of gases such as CO, (:{text{H}}_{2}), and (:{text{H}}_{2}text{O}), while the carbon ring structure analysis revealed the formation of 5-, 6-, and 7-membered rings within LIG. This distribution of carbon rings was experimentally validated using transmission electron microscopy (TEM). Additionally, water solubility test showed that the substrate completely degraded within 2 days under specific environmental conditions. This study highlights KGM-based LIG as a promising alternative for sustainable electronics that provides a viable solution to e-waste while maintaining the functionality for sensing applications.

HT250 gray cast irons were processed by laser cavitation peening (LCP). The electrochemical corrosion performance of HT250 gray cast iron subjected to massive LCP treatment under various electrolyte concentration and immersion was systemically studied. The residual stress distribution and microstructure evolutionof LCP treated HT250 were investigated. Based on the experiment results, the effect of LCP and the corrosion mechanism were discussed. LCP processing significantly enhances the corrosion resistance of HT250. The corrosion potential in a 3.5% NaCl solution shifted positively from − 1.153 V (substrate) to -1.126 V after four LCP impacts, while the corrosion current density decreased. The improvement was more pronounced with an increasing number of impacts. Furthermore, LCP introduced considerable compressive residual stress on the surface, reaching a maximum of -302 MPa after four impacts, and led to progressive grain refinement. However, in high-concentration NaCl solutions (14%), long-term immersion (120 min) diminished this advantage, with the corrosion resistance of LCP-treated specimens becoming comparable to the substrate. The impact of LCP induces residual compressive stress on the HT250 surface and refines the grains.

Zinc oxide (ZnO) nanorods, synthesized using a hydrothermal method, were etched in a solution containing ZnO nanopowder for varying durations. The morphological and structural features of the etched ZnO nanorods were characterized using field-emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD). FESEM images showed a reduction in both the diameter and length of the nanorods with increasing etching time. Additionally, XRD results revealed a significant decrease in the intensity of the (002) peak as etching time increased. Furthermore, the electrical resistance of the sensors exhibited a substantial increase with prolonged etching time. The sensing properties were enhanced by the etching process; notably, the ZnO nanorods etched for 3 h showed excellent UV photoresponsivity and sensitivity, with values of 6.52 A/W and 2.4 × 10⁵, respectively. This represents a significant improvement over the unetched nanorods, which exhibited values of 0.67 A/W and 420.

Due to its low cost, non-toxicity, and ease of availability, zinc oxide (ZnO) thin film is a promising substitute for ITO in optoelectronic applications. We have used RF sputtering to deposit ZnO thin films as transparent conducting oxide (TCO) films on glass substrates at varying substrate temperatures. It was examined how the substrate temperature affected the optical, morphological, and structural characteristics of ZnO thin films. A strong preferred orientation along the (002) plane, which is highly dependent on substrate temperature, is revealed by X-ray diffraction (XRD) measurements. Additionally, as the substrate temperature rises, grain size increases. Scanning electron microscope (SEM) micrographs show how the structure grows and how the surface roughness changes as the substrate temperature rises. With a sharp absorption edge at 375 nm, which closely matches the intrinsic band gap of ZnO (~ 3.3 eV), optical absorption spectra reveal high transparency of the film (95% transmission) in the visible region. As per photoluminescence (PL), the UV PL emission in ZnO thin films can be affected by both crystal quality and stoichiometry. When compared to other substrate temperatures, samples deposited at 175 °C exhibit superior properties. We annealed (post-deposition) the sample, which had excellent characteristics (ZnO thin film deposited at 175 °C), at four different temperatures to observe the further impact of the thermal process on the structural, morphological, and optical properties of ZnO thin film. At last, the I-V curve for the fabricated device at different substrate temperature were shown.

Laser cladding (LC) technology has been widely applied in the manufacturing and remanufacturing of high-integrity surface coatings. However, the performance of the coatings is significantly affected by process parameters. To obtain coatings with optimal geometry and microhardness, this study employed response surface methodology (RSM) to explore the mechanism by which LC process parameters regulate coating performance. Single-track coatings of 316 L alloy were deposited on a 30CrNiMo8 alloy steel substrate following a design of experiments. Regression equations were established to describe the relationships between laser power, scanning speed, powder feeding speed, and the geometrical characteristics as well as microhardness of the coatings. The accuracy and reliability of the models were verified using analysis of variance (ANOVA). The results show that laser power exerts a significant influence on the formation and depth of the melt pool, with distinct melt pools forming on the substrate surface when the laser power exceeds 700 W. Moreover, process parameters affect the geometrical and mechanical properties of the coatings to varying extents. Among them, scanning speed has the most significant impact on the surface integrity of the coatings, particularly the width-to-height (W/H) ratio of the cladding track and the coating microhardness. In contrast, the width-to-depth (w/d) ratio of the melt pool and the microhardness at the interface are primarily affected by the interaction between scanning speed and powder feeding speed. This study proposes a robust experimental design and manufacturing method, demonstrating that the properties of LC coatings can be accurately predicted and controlled by adjusting key process parameters.

The magnetic nanoparticles of Y³⁺ doped cobalt ferrite (CoFe_2 − xY_xO₄, x = 0.00, 0.01, 0.02, 0.03, 0.04, 0.05) were synthesized by sol-gel auto combustion method using green synthesis approach by utilizing Piper Nigrum (black pepper) extract. The structural, surface, thermo-elastic and mechano-elastic properties were investigated using Rietveld X-ray diffraction analysis, transmission electron microscopy (TEM), Brunauer Emmitt Teller (BET) and Fourier Transform Infrared Spectroscopy (FTIR) techniques. The X-ray diffraction analysis confirmed the single phase production of the nanoparticles. The XRD patterns of all the samples were successfully refined using Rietveld analysis, yielding goodness-of-fit (χ²) values in the range of1.83-3.03.The average particle sizeobtained from histogram plots was in the range of 45 –47 nm. The surface area calculated through BET analysis was found to be 1.555 m²/g, 8.796 m²/g and 17.509 m²/g for x = 0.00, 0.03 and 0.05 respectively. The thermo-elastic properties namely Debye temperature found todecreases from 690 K to 675 K with Y³⁺ doping. The mechano-elastic properties such as Young’s modulus decreases from 149.31 GPa to 143.31 GPa, bulk modulus decreases from 106.11 GPa to 101.85 GPa, the modulus of rigidity decreases from 71.87 GPa to 68.98 GPa on doping Y³⁺ ions. However, thePoisson’s ratio remains almost constant to 0.224. Thus, the doping of Y³⁺ ions in cobalt ferrite strongly affects the structural, surface, thermo-elastic, mechano-elastic properties.

Multiferroic composite system, (x)BaTiO₃-(1-x)CoFe₂O₄ (x = 0.2, 0.4, 0.6, 0.8), developed using solid-state reaction technique to explore their potential applications, primarily in magnetic field sensing. X-ray diffraction and Rietveld refinement confirmed co-occurrence of both ferromagnetic CoFe₂O₄ (CFO) and ferroelectric BaTiO₃ (BT) phases within synthesized composites. Dielectric measurements highlighted frequency-dependent dispersive behavior of both dielectric constant and loss tangent. 0.4BT-0.6CFO composite exhibited the highest dielectric constant (~ 1200) at 1 kHz and 400 °C, suggesting its potential for energy storage and tunable device applications. AC conductivity showed an increasing trend with both frequency and temperature. The activation energies varied from 0.69 eV to 0.80 eV, where 0.2BT-0.8CFO composite attained the highest DC conductivity (~ 11.40 × 10^− 3 S/m) with an activation energy of 0.72 eV. UV-Vis spectroscopy revealed band gaps ranging from 2.14 eV to 2.59 eV, showing an increasing trend upon increasing BT content, suggesting a semiconducting nature. Saturation magnetization showed an inverse relation with BT concentration, declining from 55.18 emu/g for 0.2BT-0.8CFO to 15.18 emu/g for 0.8BT-0.2CFO. The synthesized composites showed good values of magnetoelectric (ME) coupling coefficient ranging from 0.54 to 0.98 mV/cm.Oe, where the highest ME coefficient was observed in 0.8BT-0.2CFO, highlighting the practical applications of these multiferroic composites in magnetic field sensing devices.

In this study, ZnO and CdS thin films were synthesized using the nebulizer spray method, and their structural, optical, and electrical properties were systematically investigated. X-ray diffraction (XRD) analysis confirmed the formation of high-purity hexagonal wurtzite phases for both ZnO and CdS. Optical measurements revealed wide band gaps of 3.30 eV for ZnO and 2.43 eV for CdS, along with high transmittance in the visible range. Scanning electron microscopy (SEM) images showed that both films consisted of uniformly distributed and densely packed nanostructures. The current–voltage (I–V) characteristics of the Ag/CdS/ZnO/ITO heterojunction were measured to evaluate its rectifying behavior. The estimated ideality factor, barrier height, and saturation current were 1.88, 0.72 eV, and 4.26 × 10⁻⁸ A, respectively, indicating typical Schottky diode behavior. Compared to individual ZnO and CdS metal–semiconductor (MS) photodetectors, the heterostructure demonstrated significantly improved optoelectronic performance, with a high photosensitivity of approximately 525 and a photoresponsivity of 0.72 A/W. The ITO/ZnO/CdS/Ag heterostructure, which showed the best performance under visible light, also exhibited the highest optoelectronic performance in measurements under single wavelength light (532 nm), reaching 0.34 A/W photoresponsivity, 78.5% EQE and 5.1 × 10¹¹ Jones detectivity values ​​and also gave a very fast response with 0.15 s rise time and 0.23 s decay time. These results highlight the potential of the Ag/CdS/ZnO/ITO structure for broadband and low-intensity light detection applications.