Applied Physics A最新文献

In this work, impurities-induced ZnO nanostructured powders were prepared via a benign, ultrasonicated low-temperature solution immersion method. The humidity sensor was constructed utilizing the nanocomposite consisting of the synthesized impurities-induced ZnO nanostructured powders with reduced graphene oxide by a facile brush printing procedure. This work intended to evaluate the effect of impurities on the formation of nanocomposite heterostructures for optimal humidity sensing properties and investigate their correlation with morphological, chemical, optical, and electrical characteristics. The characterization for morphological, chemical, and optical changes induced by Al and W impurities in the nanocomposites was conducted through XRD, HRTEM, EDS, Raman spectroscopy, XPS and DRS. The fabricated humidity sensors have been evaluated at room temperature to assess their sensor resistance ratio, sensitivity, sensing response, and other related humidity sensing performance at relative humidity levels ranging from 40 to 90%. The humidity sensor utilizing rGO/W:ZnO nanocomposite exhibited better resistance changes compared to rGO/ZnO. Corresponding to the nanocomposite formation between W:ZnO and rGO, the sensor resistance ratio and sensitivity improved significantly to 249.61 ± 0.97 and 12.67 ± 0.06 MΩ/%RH, respectively with the sensor establishing a maximum sensing response of 99.61 ± 0.02. Furthermore, the rGO/W:ZnO heterostructure-based humidity sensor demonstrated improved and lowest hysteresis error, long-term stability over 30 days, and reliable repeatability compared to other tested samples within the tested relative humidity range. The utilization of W:ZnO with rGO as sensing material provides a novel direction for designing a cost-effective and highly sensitive humidity monitoring sensor.

La_0.67Sr_0.33MnO₃ (i.e., LSMO), a perovskite semi-metal oxide, is renowned for its high spin polarization, elevated Curie temperature, and notably low Gilbert damping, making it a promising candidate for spintronics applications. In this study, anisotropic Gilbert damping was experimentally observed in a 20-nm thick epitaxial single-crystal LSMO/STO (sub.) film deposited by using pulsed laser deposition (PLD), exhibiting a combination of uniaxial and fourfold anisotropies, using broadband ferromagnetic resonance (FMR) at 300 K. The behavior of the damping coefficient α, suggests that Gilbert damping in the LSMO film predominantly arises from two-magnon scattering. Remarkably, the anisotropic effective damping showed a significant increase, from 125 to 229%, across the easy and hard magnetic axes as the temperature decreased from 300 K to 100 K. Additionally, an enhanced peak of the Gilbert damping is observed as the temperature rises to approximately 150 K, likely due to a spin reorientation transition at the LSMO/STO interface. These findings underscore the potential of LSMO thin films in spintronic devices requiring tunable magnetic damping properties.

The smallest computer chip structures currently available are produced using state-of-the-art EUV radiation. The established concept utilizes CO₂ lasers to pump a laser-induced plasma, generating 13 nm EUV radiation. In diffusion-cooled carbon dioxide lasers, long-term stability of the gas mixture is extremely important for stable performance because there is no gas exchange. Minimal amounts of water disturb the gas equilibrium. Molecular sieves enable rapid drying of the resonator and long-term water adsorption. However, conventional 3 Å molecular sieves and molecular sieves from previously published studies adsorb not only water molecules but also other laser gas components such as carbon dioxide in parallel. This leads to both a drop in pressure and a loss of laser power making them inappropriate for use in a diffusion-cooled laser. In this work, the chemical and selectivity properties with regard to water and carbon dioxide molecules of specially manufactured cesium-ion exchanged 3Å LTA molecular sieves were systematically investigated and their suitability for the laser was tested. Applying molecular sieves with an optimum exchange rate of 40.5% cesium content prepared with a high regeneration temperature of 673.2 K, a condition was finally found in which the water from the laser gas is adsorbed in sufficient quantity (15.9% of the molecular sieve’s self-weight), even the adsorption of carbon dioxide was prevented to a negligible extent. Despite a very small difference in molecular diameter between water and carbon dioxide of only 0.2 Å, long-term continuous operation of the system became possible.

The principle objective of this manuscript is to investigate the propagation of time-harmonic plane as well as surface wave in an infinite linear nonlocal thermoelastic medium occupied the whole space, assuming a known wavelength. For the thermodynamic response, we adopt the dual-phase-lag (DPL) heat conduction model of generalized thermoelasticity. The study aims to analyze wave characteristics, including dispersion, damping, and coupling effects, under these advanced thermoelastic theories. Our analysis reveals six possible plane harmonic in time waves: two uncoupled transverse waves and four coupled longitudinal waves. The transverse waves propagate independently, remain undamped over time, and exhibit dispersion due to size-dependent effects, resulting in reduced wave speeds. The longitudinal waves, influenced by thermal effects, experience dispersion and temporal damping. Among these, a quasi-elastic wave and a stationary quasi-thermal wave decay exponentially to zero over time, while the presence of one or two dilatational quasi-thermal waves depends on the phase-lag parameters. For surface waves in a semi-infinite nonlocal thermoelastic medium, we derive the dispersion relation and the secular equation under a traction-free boundary condition allowing heat exchange. Numerical simulations illustrate the influence of nonlocality and DPL effects on wave behavior. The results provide deeper insights into wave propagation characteristics in advanced thermoelastic media, which may have implications for material design and wave-based applications.

The Y-type hexaferrite Ba₂CoZnFe_12 − xHo_xO₂₂ at x = 0.0, 0.025, 0.050, 0,075, and 0.1 was synthesized by using sol-gel auto-combustion method. The physical and dielectric characteristics of all hexagonal ferrites were investigated. Through XRD analysis the single-phase hexagonal structure without any impurities was identified. The crystallite size ranges from 39.27 nm to 56.11 nm. The production of the Y-type hexaferrites was confirmed by the Fourier-transform infrared (FTIR) study. Various dielectric parameters were evaluated at room temperature from 1 GHz to 6 GHz. These included dielectric constant, dielectric loss, AC conductivity, Quality Factor, Impedance, and Cole-Cole parameters. Ho-doped Y-type hexagonal ferrites’ conduction process was evaluated using Cole-Cole analysis. Until a certain point, holmium-substituted Y-type hexaferrites showed constant trends with frequency; after that, resonance-like behavior was seen. The dielectric properties of all hexaferrites initially decreased with frequency, followed by a nearly constant phase, and subsequently resonance-like behavior. As the Holmium content rose, the dielectric parameters initially dropped, but they eventually rose to the maximum substitution level. The dielectric experiments showed that all of the samples were insulators and that the AC conductivity dropped as the holmium concentration increased. Additionally, for a constant bias voltage supplied, the real component of the dielectric constant demonstrated a considerable reduction with increasing frequency. Ho-doped Y-type hexa ferrite at x = 0.025,0.050 and 0.1 was found to have the most promising properties for high-frequency applications because of their crystallite size.

Optimizing the phase structure is critical for enhancing the mechanical properties of multi-principal element alloys (MPEAs). This study employed a stacking strategy within machine learning to build an ensemble model aimed at improving the accuracy of MPEA phase structure prediction, with an emphasis on the interpretability of the results. By utilizing Pearson correlation coefficients and mutual information scores, the importance of five key features was analyzed: valence electron concentration, difference in electronegativity, difference in atomic radius, mixing entropy, and mixing enthalpy, and weights were assigned accordingly. These features were used as the input variables to train the ensemble learning models. After comparing various models, it was found that an ensemble comprising Random Forest, XGBoost, CatBoost, and logistic regression performed optimally, achieving an accuracy of 0.875 and F1 score of 0.8731. Experimental validation confirmed the reliability of the ensemble model’s predictions. Furthermore, to demonstrate the applicability of the proposed ensemble model to continuous datasets, experiments were conducted to predict the MPEA hardness. The results show that the model also predicted the MPEA hardness, indicating that ensemble learning algorithms can effectively handle different types of data in material property predictions. In summary, this study highlights the potential value of ensemble learning in material science. Finally, the method of the ensemble learning model guiding material composition design is discussed in detail, which provides technical support for MPEA design and broadens the application scope of such algorithms.

Vanadium dioxide (VO₂) is commonly employed in smart windows for its excellent thermochromic properties. However, its limited luminous transmittance (T_lum) and insufficient solar modulation capability (ΔT_sol) have severely limited its commercial application. In this study, the VO₂ films are prepared through rapid thermal annealing of the sputtered vanadium film on the quartz glass substrate. Then the wrinkled ZnO films are prepared as the antireflection layer on top of the VO₂ films using the sol-gel method. The light propagation path on the films surface is altered by the wrinkled topology, trapping most light within the ridges and valleys, while reducing reflection and increasing light transmittance. Compared with single-layer VO₂ films, the wrinkled ZnO/VO₂ bilayer structure can significantly increase T_lum from 33.3 to 47.7%, ΔT_sol from 5.6 to 7.9%, and decreases phase transition temperature (T_t) from 57.35 °C to 50.34 °C, the thermal hysteresis width (ΔT) from 14.8 °C to 12.78 °C. Furthermore, this structure exhibits an excellent water contact angle of 97.36 °, with its hydrophobic properties allowing ZnO films to function as a protective layer. Even after being exposed to air at room temperature for 60 days, the bilayer structure can still maintain its initial thermochromic performance. The results of this study provide new possibilities for improving the performance of smart windows.

Supercapacitors (SCs) are ideal for high-power applications due to their rapid power delivery. The performance of SCs hinges on innovative electrode materials. This study presents the fabrication of a CuZrO₃ and graphene nanoplatelets (GNP) composite via a microwave-assisted, eco-friendly method. Structural and morphological analyses were conducted using XRD, FT-IR, FT-Raman, UV-DRS, SEM, EDX, HRTEM and N₂ adsorption/desorption. Electrochemical tests on CuZrO₃ and CuZrO₃@GNP revealed high capacitance (405.5 Fg ⁻¹), excellent rate performance, and good cyclic stability. An asymmetric supercapacitor using CuZrO₃@GNP was also fabricated and tested, showing a specific capacitance of 38.01 Fg ⁻¹, low charge transfer resistance, and robust cyclic performance. Comparative analysis with existing literature highlights the superior performance of this composite material in terms of specific capacitance and stability. This study demonstrates the potential of the CuZrO₃@GNP nanocomposite for developing advanced SCs electrode materials.

The main objective of this manuscript is to conduct a comprehensive analysis of the intricate interaction between rotation and initial stress in a nonlocal elastic spherical structure characterized by dual porosity. The influence of rotation and initial stress is examined both in the presence and absence of the nonlocal elasticity effect on the elastic sphere with dual porosity. A technique based on time-harmonic variations is applied to the governing equations, simplifying them into ordinary differential equations. The analytical results, computed using MATLAB software, provide a detailed examination of the response of the nonlocal elastic sphere to rotation and initial stress. A numerical iteration method is employed for the free vibration analysis, presenting the natural frequencies in tabular form according to mode numbers. Computer simulations offer graphical representations of frequency shifts in relation to mode numbers, comparing nonlocal and local elastic spheres. The study illustrates the variations in field functions with respect to the radius, considering the effects of rotation and initial stress. Graphical presentations indicate that as the rotation factor increases, the variations exhibit more pronounced behaviors. Motivated by its relevance to engineering and geotechnical applications, this research aims to deepen our understanding of these interactions, contributing valuable insights for the optimization and design of structures across various fields.