Search

Millimeter wave components, such as circulators and isolators, frequently use magnetic fields to break symmetry of the signal propagation and provide unidirectional signal transmission. While effective, these components have not seen the level of miniaturization of other millimeter wave components, primarily due to the discrete nature of the magnets used in the components. Using circulators in the 40-50 GHz range as a motivating application, requirements arise for the deposited films, namely immunity to eddy currents, sufficient magnetization to act as self-biasing magnets, and out-of-plane orientation of the self-biasing field. Based on these required properties, hexaferrite materials are selected for their strong magnetocrystalline anisotropy (MCA) and low conductance. The difficulty of integrating these components monolithically with monolithic microwave integrated circuits (MMIC) originates from the incompatibility of crystal structure with standard semiconductor materials and process conditions. Additive manufacturing using a composite of strontium hexaferrite (SrFe12O19) particles and photoresist has been chosen as a method to overcome the difficulties of integrating hexaferrite material to semiconductor substrates. Due to their large internal anisotropy field, the particles of strontium hexaferrite tend to rotate to the field direction instead of changing magnetization direction under application of an external magnetic field (less than the anisotropy field). We have developed a method for 3D printing composites of high strontium hexaferrite concentration (up to 20% by volume) in a liquid photoresist, SU8. Rotation of hexaferrite particles in polymer matrix and thus magnetic anisotropy has been demonstrated in the composite, which is subsequently cured to hold the physical position and orientation of the particles. The anisotropy of the self-biasing field provided by the films has been experimentally characterized, and a ferromagnetic resonance (FMR) frequency ~43 GHz has been observed. We have also characterized the viscosity of the particle-laden polymer at different particle concentrations. 3D printing of this composite with poling will make it possible to directly print magnetic components that require out-of-plane anisotropic magnetization.

Magnetic circuit components have long been the largest and most difficult components to miniaturize. Printed circuit board (PCB) fabrication methods cannot achieve small diameter, high aspect-ratio vias for high winding turn numbers to achieve high inductance, and microelectronics methods cannot achieve the high-quality and thick ferrite core materials. In this paper, we present an alternative breakthrough method of printed circuit fabrication to significantly reduce the effective via diameter for embedded magnetic devices, boosting the inductance per unit area. To reduce the effective via diameter, high-density via plugs are ex-situ fabricated and shaped, and then embedded into PCB substrate in the same process as standard magnetic core embedding. The structure of the plug is such that precise placement within the substrate, or alignment to the plug with the winding pattern, is not necessary. Devices presented in this paper use via plugs with an effective diameter of 40 μm and a theoretically unlimited aspect ratio, though refinements in the plug fabrication process are expected to reduce the via diameter down to 10μm. The process is experimentally demonstrated with a 14-turn racetrack shaped transformer; novel diagnostic methods using magneto-optic garnet films to image current paths are also demonstrated.

Based on thermoelectric analogy method, a thermal network model coupled with electromagnetic loss is presented. According to the actual structure of dry-type transformer windings, an accurate thermal network is established. Considering the distribution characteristics of heat source along cooling ducts inside the dry-type transformer, the thermal parameters such as heat flux and convective heat transfer coefficients are calculated by finite element method analysis (FEM) and computational fluid dynamics (CFD). Based on temperature rise experiment, the hottest spot located at the top of outmost high voltage winding is 151.8 °C, which verified the correctness of thermal network model.

Efficient bandwidth utilization is significant in new communication systems where secondary users can be used besides of primary users considering interference issues and idle state of primary users. Using secondary users as relays to transmit their own signals in addition to the primary signals can be applied for more reliability of the system where opportunistic relay selection can significantly enhance the performance of the system. The best-condition secondary user is selected as the optimum relay for retransmission of primary/secondary signal. Outage probability is analyzed in this paper based on decode and forward techniques in secondary users while the closed-form statement for outage probability is provided and verified by numerical evaluations.

The power transmission tower’s ground electrode defect will affect its normal current dispersion function and threaten the power system’s safe and stable operation and even personal safety. Aiming at the problem that the buried grounding grid is difficult to be detected, this paper proposes a method for identifying the ground electrode defects of transmission towers based on single-side multi-point excited ultrasonic guided waves. The geometric model, ultrasonic excitation model, and physical model are established, and the feasibility of ultrasonic guided wave detection is verified through the simulation and experiment. In actual inspection, it is equally important to determine the specific location of the defect. Therefore, a multi-point excitation method is proposed to determine the defect’s actual position by combining the ultrasonic guided wave signals at different excitation positions. Besides, the precise quantification of flat steel grounding electrode defects is achieved through the feature extraction-neural network method. Field test results show that, compared with the commercial double-sided excitation transducer, the single-sided excitation transducer proposed in this paper has a lower defect quantization error in defect quantification. The average quantization error is reduced by approximately 76%.

A high-precision tunable single-frequency fiber laser (T-SFFL) at 1.5 μm based on self-injection locking is experimentally demonstrated. By virtue of an effective filtering and self-injection locking scheme, a stable single-longitudinal-mode operation of the fiber laser is obtained. The fine wavelength tunability is implemented by stretching a uniform fiber Bragg grating in the self-injection loop, and the laser wavelength is tuned from 1550.28 to 1560.40 nm with a tuning accuracy of less than 54 pm. In the whole tuning range of 10.12 nm, an output power of approximately 5 mW and an optical signal-to-noise ratio of 71 dB are synchronously obtained with this laser system. Additionally, the measured laser linewidth is less than 630 Hz and the relative intensity noise is lower than -149 dB/Hz at frequencies from 0.4 to 7.5 MHz. It is believed that this 1.5 μm high-precision T-SFFL can be a promising candidate for the optical communications system applications.

Displacement damage effects in backside illuminated CMOS image sensors (BSI CISs) are investigated. Several BSI CISs with distinct epitaxial layer thicknesses are irradiated by several protons and neutrons to study the influence of technology parameters and radiation parameters on the radiation response of these imagers. A significant degradation in quantum efficiency (QE) is observed for thick epitaxial layer at the absorbed dose of 1230 TeV/g. Dark-current damage factor of 0.141 e⁻·s⁻¹·μ m⁻³·(TeV/g)⁻¹ is determined in BSI CIS. The influence of particle types, particle energy, and radiation fluence on dark current distributions is presented at the same displacement damage dose (DDD). Dark current random telegraph signal (DC-RTS) is reported and the variation in epitaxial layer thickness has no influence on DC-RTS behavior. This work highlights the relationship between key parameters and DDD: the limiting factors of the imager performance are single pixel [hot pixel and random telegraph signal (RTS) pixel] at a low DDD range, mean dark current and single pixel at a medium DDD range, and mean dark current in the high DDD case, respectively.

This paper proposes a method for generating RSFQ logic circuits utilizing special RSFQ gates in logic synthesis. It is suited for the standard technology mapping flow used in logic synthesis tools and enables generating RSFQ circuits utilizing confluence buffers (CBs) and resettable DFFs (RDFFs), to reduce the number of clocked gates by reduction of logic depth. A library of supergates, each consisting of several gates, is used to compose a resultant circuit in the technology mapping. In this paper, a library containing supergates including those special gates is generated and is utilized to design circuits with the gates. First, a generation of a supergate library is proposed to introduce CBs and RDFFs, which realize logic OR without clock pulses and a fused function of logic AND and NOT, respectively. The generated library contains supergates including the special gates and they are used to compose the resultant circuits with the special gates. A mapping approach is also proposed. It distinguishes non-clocked gates such as CBs and clocked gates. It takes the number of inserted DFFs for path balancing into account to reduce the number of clocked gates. The method was implemented into the state-of-the-art academic EDA tool, i.e., ABC, and was evaluated. Evaluation results show that the number of clocked gates is reduced by about 30% from the original ABC with path-balancing DFFs.

The evolution of CMOS image sensors and their prospects using advanced imaging technologies are promising candidates to improve the quality of life. With the rapid advent of parallel analog-to-digital converters (ADCs) and back-illuminated (BI) technology, CMOS image sensors currently dominate the market for digital cameras, and stacked CMOS image sensors continue to provide enhanced functionality and user experience in mobile devices. This article reviews the latest achievements in stacked image sensors with respect to the evolution of image sensor architecture for accelerating performance improvements, extending sensing capabilities, and integrating edge computing with various stacked device technologies.

Josephson junctions (JJs) with non-hysteretic I-V characteristic and high critical parameters are required for many applications; in particular, they are needed to create tunable THz range oscillators. We fabricated and studied shunted superconductor-insulator-superconductor (SIS) Nb-AlOx-Nb tunnel junctions with an area of about 1m2, estimated their parameters, and compared them with theoretical models. To assess the performance of shunted junctions in the terahertz range, their characteristics were studied under the influence of a high-frequency signal; the estimated value of the characteristic voltage for the shunted junction at a high frequency is about 1 mV. To improve the circuit parameters, a new type of the shunting based on application of NIS junctions was proposed, which reduces the influence of parasitic inductance, expands the frequency range of the generator, and decreases the size of the structure. The JJs with a new type of shunting have been fabricated and studied. The niobium integrated circuits intended for matching the superconducting oscillator and an SIS junction as a microwave detector were designed, fabricated, and tested. Such structures are required for studying the spectral characteristics and analyzing the operation of the oscillator. The developed circuits have demonstrated efficient operation at frequencies from 300 to 700 GHz; the experimental results are in good agreement with the simulated characteristics. The results obtained will be implemented for further development of the THz range oscillators.

A 320 x 240 indirect time-of-flight (i-ToF) image sensor with a 5.6-μm two-tap 1.5-V pump gate modulation pixel has been designed. Novel characteristics, such as the optimized pinned layer doping and potential buffer region (PBR) structure with pump gate modulator (PGM), are proposed to achieve a maximum lateral modulation electric field of 1500 V/cm under the front-side illumination (FSI) process. As a result, the proposed time-of-flight (ToF) sensor shows 200-mW power consumption and 54% demodulation contrast (DC) at 50-MHz modulation frequency, depth noise less than 1% with 940-nm illuminator from 0.3 to 3 m.

This paper proposes a novel approach to the modelling of HTS transformer-rectifier flux pumps that can charge HTS magnet-ic loads without the need for bulky current leads or expensive cryogenic requirements. The model was built in MATLAB/Simulink for a flux pump with 2 HTS switches, an HTS transformer with a primary inductance of 15 mH, second-ary inductance of 50 H and an HTS magnetic load with an in-ductance of 2 mH. With a 5 A pk-pk triangular current wave-form at 2 Hz the system can load the HTS load to 34.63 A in 5 s. This incremental addition of flux to the load demonstrates the advantage of flux pumps as they can charge high-field magnets without the need for large power sources. The speed of flux pumping is improved by increasing the system frequency, the magnitude of the dynamic voltage developed in the HTS switches and by increasing the primary inductance of the trans-former. This has widespread industrial applicability in fields such as the charging of high-field magnets for MRI systems.

Theoretical and numerical mode estimation performed on Silicon Nanowire Optical Rectangular Waveguide (SNORW) is presented for on-chip communication in photonic integrated circuits. The propagation behavior of electric and magnetic fields is investigated, where zeroth order mode is found dominating inside the nanoslot region of SNORW for the circularly symmetric quasi-TE mode to propagate. This SNORW structure supports hybrid mode, which derives its behavioral root from the rectangular waveguide and functional root from the slot waveguide. In periodic silicon nanowire-based waveguide, it is found that the envelope of mode field intensity closely matches with rectangular waveguide and the guiding properties closely matches with slot waveguide. The type of mode is analyzed by full vectorial Finite Element Method (FEM) and the analytical expression is derived using Effective Index Method (EIM). Analytical expressions are used to express Quasi-TE mode in term of material profile and waveguide physical parameters. The results obtained for SNORW in S, C and L wavelength bands are compared with the earlier reported work on slot waveguide, and the field intensity obtained with the theoretical equations is also compared with that of FEM results.

Sensors are crucial in the understanding of machines working under high temperatures and high-pressure conditions. Current devices utilize polymeric materials as electrical insulators which pose a challenge in the device’s lifespan. Ceramics, on the other hand, is robust and able to withstand high temperature and pressure. For such applications, a co-fired ceramic device which can provide both electrical conductivity and insulation is beneficial and acts as a superior candidate for sensor devices. In this paper, we propose a novel fabrication technique of complex multi-ceramics structures via 3D printing. This fabrication methodology increases both the geometrical complexity and the device’s shape precision. Structural ceramics (alumina) was employed as the electrical insulator whilst providing mechanical rigidity while a functional ceramic (alumina-doped zinc oxide) was employed as the electrically conductive material. The addition of sintering additives, tailoring the printing pastes’ solid loadings and heat treatment profile resolves multi-materials printing challenges such as shrinkage disparity and densification matching. Through high-temperature co-firing of ceramics (HTCC) technology, dense high quality functional multi-ceramics structures are achieved. The proposed fabrication methodology paves the way for multi-ceramics sensors to be utilized in high temperature and pressure systems in the near future.

The application of machine learning (ML)-based methods to the study of thermoelectric (TE) materials is promising. Although conventional ML algorithms can achieve high prediction performance, their lack of interpretability severely obstructs researchers from extracting material-oriented insights from ML models. In this work, high ML-based prediction performance was achieved with respect to TE power factors (PFs), and the results were well understood by the SHapley Additive exPlanations (SHAP), a method to identify the correlations between targets and descriptors. We designed a robust PF prediction model for diamond-like compounds via a stacking technique, and the model achieved a coefficient of determination value above 0.95 on the test set. From the SHAP analysis, the PFs were negatively correlated with electronegativity and positively correlated with the descriptor “volume per atom” based on the previously reported dataset. TE domain knowledge was adopted to understand these correlations. This work shows that ML models can achieve high accuracy while exhibiting good interpretability, making them useful for materials scientists.

In this work, a machine learning (ML) model was created to predict intrinsic hardness of various compounds using their crystal chemistry. For this purpose, an initial dataset, containing the hardness values of 270 compounds and counterpart applied loads, was employed in the learning process. Based on various features generated using crystal information, an ML model, with a high accuracy (R2=0.942), was built using extreme gradient boosting (XGB) algorithm. Experimental validations conducted by hardness measurements of various compounds, including MSi2 (M= Nb, Ce, V, and Ta), Al2O3, and FeB4, showed that the XGB model was able to reproduce load-dependent hardness behaviors of these compounds. In addition, this model was also used to predict the behavior based on prototype crystal structures that are randomly substituted with elements.

ABSTRCT Sustainable light energy from ambient environment has attracted particular attention to meet the ever-growing need of small-scale electronics. The modulation of intercorrelated thermal and electronic transport is one of the crucial aspects for reliable photothermoelectric electronics. Herein, a defect-promoted photothermoelectric effect is demonstrated in densely aligned ZnO nanorod array with rich lattice defects. The defect-rich ZnO device delivers high electrical conductivity and large Seebeck coefficient to enable significant improvement of photothermoelectric energy conversion and self-powered photodetection. The position sensitivity reaches approximately 0.19 mV·mm-1, and the temperature gradient induced electric field makes up for the suppression in the photothermoelectric process. The synergism between intrinsic defects and extra temperature field plays an important role in promoting the photothermoelectric properties of dense ZnO nanorod array. This study is interesting for interpreting the thermo-phototronic phenomena as well as demonstrating the possibility of defect engineering and phonon engineering to enable highly efficient light energy scavenging and self-powered photodetection.

There is a strong interest in using physical waves for artificial neural computing because of their unique advantages in fast speed and intrinsic parallelism. Resonance, as a ubiquitous feature across many wave systems, is a natural candidate for analog computing in temporal signals. We demonstrate that resonance can be used to construct stable and scalable recurrent neural networks. By including resonators with different lifetimes, the computing system develops both short-term and long-term memory simultaneously.

Silicene, a zero-gap semi-metallic advanced material, has received much attention due to its extraordinary electronic and optical characteristics, which could be used in plasmonics nano-devices. This material presenting as a tunable material without degrading its high carrier mobility. By applying the rigorous numerical techniques, the optical and electrical properties of silicene at high terahertz frequencies are calculated here. Beneath the influence of environmental effects such as the Fermi level, temperature, and external electric field, on the optical conductivity and refractive index of silicene are investigated using the tight-binding model. The effect of Fermi level from zero to 1 eV, external electric field from zero to 2.5 eV, and temperature from 5 to 400 K are investigated on the optical properties of silicene. One of the interesting features of Silicene is its adjustable bandgap, which we are present here.

In this proposed work, performance of junctionless transistor with the use of spacers has been evaluated at 15nm gate length in Cogenda TCAD tool. This work is implemented as variation in four parts: changing the spacer extension length, placement of spacers having dual-κ, proportion of low and high-κ spacers, and value of high-κ dielectric constant. Impact of all these parameters is considered on the output of proposed device in terms of various output parameters like on-current (ION), off-current (IOFF), subthreshold swing (SS), drain induced barrier lowering (DIBL), transconductance (gm), transconductance generation factor (TGF), output conductance (gd), early voltage (Vea) and intrinsic gain (Av). From the simulations, it has been observed that placing spacers of dual-κ along the left and right sides of gate region has improved device performance in terms of output parameters. Due to increased gate capacitances, the increase in dielectric constant value has degraded the device performance for longer spacer extension length. However, for shorter spacer extension length, the device characteristics are improved as the value of dielectric constant is increased. Therefore a trade-off is required to get the optimum results of the device.

In this study, influence of magnetron sputtering on indium gallium zinc oxide (IGZO) ceramic target was studied to improve its performance and utilization. Results indicated that state of the target such as target grain uniformity, micro defects, C element pollution, and secondary phase showed significant influence on magnetron sputtering process. Atoms located in small grains were easily bombarded out of IGZO target, and grains with slow sputtering rate protruded from target surface. Porous microstructure of IGZO ceramic created abnormal electric field of the target during sputtering, resulting in the poisoning of target. Moreover, more indium atoms were sputtered from the target, and the proportion of In after sputtering decreased by 0.62–0.97%. The difference in sputtering rates between secondary phase and main phase led to the formation of IGZO cladding layer with poor conductivity under the combined action of sputtering and re-sputtering. In sum, these findings may provide strong guidance for further improvement and performance enhancement of IGZO sputtering target.

The rapid recombination of photoinduced charge carriers and low selectivity are still challenges for the CO2 photoreduction. Herein, we proposed that ZIF-67-derived Co3O4 hollow polyhedrons (CoHP) were embedded into NaCl-template-assisted synthesized 3D graphitic carbon nitride (NCN), subsequently, loading Ag by photo-deposition as efficient composites (CoHP@NCN@Ag) for CO2 photoreduction. This integration simultaneously constructs two heterojunctions: p-n junction between Co3O4 and g-C3N4 and metal-semiconductor junction between Ag and g-C3N4, in which Co3O4 and Ag serve as hole (h+) trapping sites and electron (e-) sinks, respectively, achieving spatial separation of charge carriers. The donor-acceptor structure design of NCN realize a good photogenerated e--h+ separation efficiency. The mesoporous structure of hollow Co3O4 facilitate gas-diffusion efficiency, light scattering and harvesting. And the introduction of plasmonic Ag further strengthens the light-harvesting and charge migration. Benefiting from the rational design, the optimized ternary heterostructures exhibit a high CO2-CO yield (562 μmol g-1), which is about 4-fold as high as that of the NCN (151 μmol g-1). Moreover, the conjectural mechanism was systematically summarized. We hope this study provides a promising strategy for designing efficient g-C3N4 systems for the CO2 photoreduction.

SrFBiS2 is a quaternary n-type semiconductor with rock-salt-type BiS2 and fluorite-type SrF layers alternately stacked along the c axis. The tunability of the crystal and electronic structures as well as the intrinsically low thermal conductivity make this compound a promising parent material for thermoelectric applications. In the current work, we show that alloying of Se and S in SrFBiS2 reduces the optical band gap with the second conduction band serving as an electron-transport medium, simultaneously increasing the electron concentration and effective mass. In addition, the raw material Bi2Se3 is shown to act as liquid adjuvant during the annealing process, favoring preferred-orientation grain growth and forming strengthen microstructural texturing in bulk samples after hot-pressed sintering. Highly ordered lamellar grains are stacked perpendicular to the pressure direction, leading to enhanced mobility along this direction. The synthetic effect results in a maximum power factor of 5.58 μW cm-1 K-2 at 523 K for SrFBiSSe and a peak zT = 0.34 at 773 K, enhancements of 180% compared with those of pristine SrFBiS2.

In this study, we demonstrate for the first time the construction of a ternary BiVO4/FeVO4/Cu2O nanorod array (NRA) photoelectrode via seed-assisted refluxing, hydrothermal and successive ionic-layer adsorption and reaction (SILAR) method and its photoelectrochemical (PEC) water oxidation performance. The energy band structures of the BiVO4, FeVO4 and Cu2O show that two type-II band alignments with a ladder-like structure are formed in the constructed ternary BiVO4/FeVO4/Cu2O NRA photoelectrode, enabling the photoelectrode to display substantially enhanced PEC performance. The constructed ternary photoelectrode loaded with the optimized Cu2O nanoparticles achieves a zero-bias photocurrent density of 50 μA cm−2, 5 times higher than that of the pure BiVO4 NRA photoelectrode. The measurements of optical property reveal that the constructed BiVO4/FeVO4/Cu2O nanorod arrays (NRAs) demonstrate improved light absorption capability. The electrochemical impedance and photoluminescence measurements confirm that the charge carriers of the BiVO4/FeVO4/Cu2O heterojunction NRAs are transferred and separated effectively. The substantially boosted PEC water oxidation activity of the constructed ternary BiVO4/FeVO4/Cu2O heterojunction NRA photoelectrode is ascribed to the improved light harvesting and effective charge separation.

Rapid heat loss and fast charge carrier recombination constitute two crucial issues that hinder the development of efficient solar energy utilization and conversion over the semiconductor in a photothermal catalytic system. Inspired by energy production from waste water, we designed an advanced 3D C@TiO2 multishell nanoframe (MNF) photocatalyst. Its unique structural features of heat confinement and vibrant photocarrier kinetics lead to excellent photo-thermal conversion for synchronous superior photocatalytic H2 evolution (503 μmol g-1 h-1) and 98.2% RhB removal without the use of any co-catalyst and sacrificial reagent under simulated sunlight irradiation (AM 1.5G). Mechanism exploration reveals that the difference between the inner and outer gas pressure formed inside C@TiO2 precursor facilitates the selective cleavage of outer TiO2 layers at selected temperatures during calcination. Synergistic effects between residual carbon core and multi-shelled TiO2 framework endow C@TiO2 MNF with excellent heat confinement and vibrant photocarrier kinetics. Such MNF photo-thermocatalyst concept provides a novel strategy for effective utilization of solar energy, and this work may open a novel avenue towards advanced nanostructures for efficient waste-to-energy conversion.

International audience; Producing ultrathin light absorber layers is attractive towards the integration of lightweight planar components in electronic, photonic, and sensor devices. In this work, we report the experimental demonstration of a thin gold (Au) metallic metasurface with near-perfect visible absorption (~ 95 %). Au nanoresonators possessing heights from 5-15 nm with sub-50 nm diameters were engineered by block copolymer (BCP) templating. The Au nanoresonators were fabricated on an alumina (Al2O3) spacer layer and a reflecting Au mirror, in a film-coupled nanoparticle design. The BCP nanopatterning strategy to produce desired heights of Au nanoresonators was tailored to achieve nearperfect absorption at ≈ 600 nm. The experimental insight described in this work is a step forward towards realizing large area flat optics applications derived from subwavelengththin metasurfaces.

In the last few decades, smart windows made from VO2-based thermochromic films have attracted extensive attention, but their actual commercial applications are limited by low luminous transmittance (Tlum), low solar modulation ability (ΔTsol), high phase transition temperature (Tc), and poor durability. In this study, glass/HfO2/VO2/HfO2 tri-layer films were designed and deposited on glass substrates by pulse laser deposition. Crystal structures, surface morphology, surface roughness, electrical properties, and optical properties of as-prepared sandwich structure films were analyzed. Results showed that both HfO2 buffer layer and antireflection layer (ARL) were monoclinic phase and grew along the (020) and (−111) crystal planes, respectively. HfO2 buffer layer not only reduced Tc of VO2 film by about 20 °C, but also played an important role in regulating crystal quality and surface morphology of VO2 films. More importantly, by covering films with HfO2 ARL, Tlum and ΔTsol of VO2 film were greatly improved. In particular, when the thicknesses of HfO2 buffer layer and ARL were 80 nm and 120 nm, the obtained HfO2/VO2/HfO2 tri-layer film reached a balance between high Tlum (∼47.2%), high ΔTsol (∼9.1%) and low Tc (∼49.1 °C). In addition, after 216 h of boiling water treatment, Tlum and ΔTsol of HfO2/VO2/HfO2 film covered with 120 nm thick ARL still remained at 49.3% and 7.0%, showing excellent durability. This research provides a new strategy for designing VO2-based smart windows with high performance and good durability.

As a representative transition metal oxide, cupric oxide (CuO) has attracted a lot of interest in miscellaneous fields. In the present work, the prominent third-order nonlinear optical (NLO) features of CuO nanosheets were demonstrated via the typical Z-scan technique at 1 μm. The open-aperture (OA) Z-scan measurements at different intensities clearly showed that CuO nanosheets possessed the saturable absorption (SA), reverse saturable absorption (RSA) and optical limiting behaviors. The closed-aperture (CA) Z-scan technology was implanted to investigate the nonlinear refractive index and the third-order nonlinear susceptibility. In virtue of the strong nonlinear optical absorption properties of CuO nanosheets, a stable all-solid-state mode-locked laser with the as-prepared CuO nanosheets as saturable absorber at 1.06 μm was realized for the first time. Our work confirmed that CuO nanosheets exhibited outstanding NLO properties, which might stimulate the development in ultrafast photonics and nonlinear optics.

Micromechanics model, finite element (FE) simulation of microindentation and machine learning were deployed to predict the mechanical properties of Cu–Al2O3 nanocomposites. The micromechanical model was developed based on the rule of mixture and grain and grain boundary sizes evolution to predict the elastic modulus of the produced nanocomposites. Then, a FE model was developed to simulate the microindentation test. The input for the FE model was the elastic modulus that was computed using the micromechanics model and wide range of yield and tangent stresses values. Finally, the output load-displacement response from the FE model, the elastic modulus, the yield and tangent strengths used for the FE simulations, and the residual indentation depth were used to train the machine learning model (Random vector functional link network) for the prediction of the yield and tangent stresses of the produced nanocomposites. Cu–Al2O3 nanocomposites with different Al2O3 concentration were manufactured using insitu chemical method to validate the proposed model. After training the model, the microindentation experimental load-displacement curve for Cu–Al2O3 nanocomposites was fed to the machine learning model and the mechanical properties were obtained. The obtained mechanical properties were in very good agreement with the experimental ones achieving 0.99 coefficient of determination R2 for the yield strength.

Thin film of WO3 has been deposited on conductive fluorine tin oxide substrate using the hydrothermal technique. The film's microstructural, morphological and optical properties have been identified using X-ray diffraction, atomic force microscope, and spectrophotometer. The obtained results have confirmed the nanocrystalline structure of the as-received WO3 thin film with crystallite size ≈63.4 nm. Analysis of the absorption coefficient using Tauc's model shows the possibility of direct and/or indirect allowed transition with energy gaps 3.95 and/or 3.45 eV, respectively. The refractive index has been determined by different methods showing the average value (2.2 and 2.3 corresponding to the direct and indirect transitions, respectively). The nonlinear refractive index and third-order nonlinear optical susceptibility have been determined, showing the high polarizability of WO3/FTO with radiation to be promising for different optical devices and applications.

Advances in flexible electronics are driving dielectric capacitors with high energy storage density toward flexibility and miniaturization. In the present work, an all-inorganic thin film dielectric capacitor with the coexistence of ferroelectric (FE) and antiferroelectric (AFE) phases based on Pb0.96La0.04(Zr0.95Ti0.05)O3 (PLZT) was prepared on a 2D fluorophlogopite mica substrate via a simple one-step process. The flexible capacitor exhibits a high recoverable energy density (Urec) of ≈ 44.2 J/cm3, a large electric breakdown strength (EBDS) of 3011 kV/cm, excellent frequency stability (500 Hz-20 kHz) and high thermal stability over 30–190 °C. It also demonstrates an outstanding bending endurance, which can maintain a high energy storage performance under various bending radii (R = 2–10 mm) or 103 repeated bends at 4 mm. The FE phase is stable near the film surface and the interface with the bottom electrode. The AFE phase with multi-domains has incommensurate modulation structures with super-periodicity of 6.5, 6.9 and 5.2. It indicates that the PLZT/LNO/F-Mica capacitor has high potential for energy storage application and may provide great opportunities for exploring new energy storage materials.

Carbon aerogels with nanoporous structure are attractive for thermal insulation under extreme conditions, but their practical applications are usually plagued by the inherent brittleness and easy-oxidation characteristic at high temperature. Herein, silica-modified carbon aerogels (SCAs) with extraordinarily high strength are prepared via a facile sol-gel polymerization of phenolic resin and siloxane, followed by ambient pressure drying and carbonization. The resulting SCAs possess medium-high density of ∼ 0.5 g·cm-3 and mesoporous structure with the mean pore size of 33 nm. During carbonization process, the siloxane could be gradually transformed into the amorphous SiO2 particles and crystalline SiC particles, which are coated on the surface of carbon nanoparticle and consequently improve the oxidation-resistance of carbon aerogels. Due to the density-porosity trade-off, the SCAs have high compressive strength of 10.0 MPa and satisfied thermal conductivities of 0.118 W·m-1·K-1 at 25 °C and 0.263 W·m-1·K-1 at 1000 °C. Furthermore, needled carbon fiber-reinforced SCAs (CF-SCAs) with ultrahigh compressive strength of 210.5 MPa are prepared, which exhibit good thermal conductivities of 0.207 W·m-1·K-1 at 25 °C and 0.407 W·m-1·K-1 at 1000 °C. The ultrahigh mechanical strength, good oxidation-resistance, good thermal insulation as well as the facile preparation make the SACs great promising in high-temperature insulations especially under harsh conditions.

With the development of high power converters, the safe operation of large IGBT modules with parallel chips is of increasing importance. In a multichip module, uneven solder layer degradation translates into higher thermal resistance for some of the chips, leading to junction temperature differences between them. However, the specific meaning of a virtual junction temperature extracted from any external electric characteristic parameter of the module is not yet clear. This paper studies the physical meanings of the temperatures estimated by the threshold voltage and the Miller platform duration as well as the quasi turn-off delay time. Experimental results show that the temperature estimated from the threshold voltage is close to the highest temperature of all the chips, while that estimated from the Miller platform duration or quasi turn-off delay time is close to the average chip temperature. Making use of the difference between the two, this paper proposes a new method to monitor the initial solder layer degradation in the multichip IGBT module. Such a method using combined temperature sensitive electric parameters (TSEPs) is verified for different levels of degradation.

Highly-sensitive and stable ozone and hydrogen sensing elements were fabricated based on well-crystalline rounded cube-shaped CsPbBr3 microcrystals, synthesized by a facile solution process performed under ambient conditions. It is shown that such elements demonstrate enhanced room temperature gas sensing ability compared to the previously reported metal halide and oxide-based ones. Electrical measurements performed on these sensing components revealed high sensitivity to ultra-low ozone and hydrogen concentrations, namely 4 ppb and 1 ppm respectively, as well as a remarkable repeatability, even after a few months of storage in ambient conditions. Both ozone and hydrogen sensors were self-activated, as they did not require the use of UV or heating external stimuli to operate, and exhibited fast detection and short restoration times. All such attractive properties along with the simple fabrication process could provide an easy, efficient and low-cost technology for the realization of future gas sensing devices.

To realize a stable and efficient wireless power transfer (WPT) system that can be used in any environment, it is necessary to inspect the influence of environmental interference along the power transmission path of the WPT system. In this paper, attempts have been made to reduce the influence of the medium with a dielectric and conductive loss on the WPT system using spiral resonators for resonator-coupled type wireless power transfer (RC-WPT) system. An important element of the RC-WPT system is the resonators because they improve resonant characteristics by changing the shape or combination of spiral resonators to confine the electric field that mainly causes electrical loss in the system as much as possible inside the resonator. We proposed a novel dual-spiral resonator as a candidate and compared the basic characteristics of the RC-WPT system with conventional single-spiral and dual-spiral resonators. The parametric values of the spiral resonators, such as the quality factors and the coupling coefficients between resonators with and without a lossy medium in the power transmission path, were examined. For the lossy mediums, pure water or tap water filled with acryl bases was used. The maximum transmission efficiency of the RC-WPT system was then observed by tuning the matching condition of the system. Following that, the transmission efficiency of the system with and without lossy medium was investigated. These inspections revealed that the performance of the RC-WPT system with the lossy medium using the modified shape spiral resonator, which is the dual-spiral resonator proposed in our laboratory, outperformed the system using the conventional single-spiral resonator.