Insulator Devices Research Articles

The electronic, structural, ferroelectric and optical properties of strontium and zirconium co-doped BaTiO[formula omitted]: First-principles calculations

Based on the first-principles calculations, we investigated the electronic, structural, ferroelectric and optical properties of (Ba0.875Sr0.125)(Zr0.125Ti0.875)O3(BSZT). The optimized structure and electron charge density analysis show that the tetragonal structure of BaTiO3 is distorted after doping with Sr and Zr, and the displacement of Zr atoms in the same layer is observed to be smaller than that of Ti atoms. The double potential well curves of pure BaTiO3 and BSZT fit well with the Landau–Ginzburg model. Meanwhile, the spontaneous polarization of BSZT is smaller than that of pure BaTiO3. Furthermore, the analysis of the density of states demonstrates that the ferroelectric properties of the BSZT material are derived from the strong hybridization between Ti 3d, Zr 4d and O 2p orbitals. Finally, we calculated the optical properties such as the real ϵ1(ω) and imaginary ϵ2(ω) part of the complex dielectric function, absorption coefficient α(ω), energy loss function L(ω), reflectivity R(ω) and refractive index n(ω) of BSZT and pure BaTiO3. The results show that the optical properties of BSZT are blue-shifted and exhibit good optical response in the UV region with the appearance of new peaks. The increase of band gap and the change of optical properties suggest that BSZT can be effectively used in ceramic capacitors, resistors with high dielectric insulation and optoelectronic devices.

Preparation of aromatic polyamide with ultra-high intrinsic breakdown strength via layered stacking structure induced by coplanar monomer

Dielectric polymers with high breakdown strength (Eb) and high retention rate of breakdown strength at elevated temperature have important application potential in advanced electrical insulation devices. Herein, the aromatic heterocyclic diamine monomer, 5-amino-2-(2-hydroxy-4-aminobenzene)-benzoxazole (HBOA), was synthesized. Theoretical calculation and single crystal date demonstrated fully the formation of intramolecular H-bond of OH⋯N]C between benzoxazole and benzene ring in HBOA, which endows the monomer a coplanar geometry. Moreover, the aromatic polyamide films were prepared by polycondensation of HBOA, and the in-plane orientation of films increases with increasing the coplanar HBOA content, which reduces the orientation confusion and cavity of chains packing. When the HBOA content is over 70%, the films exhibit dense-layered stacking structure with high crystallinity. It is found that the dense-layered stacking structure can prevent the films breakdown and failure effectively, which endows the homopolymerization (HBOA-100) film with Eb of 771 kV/mm. Moreover, the Eb of the HBOA-100 film is still as high as 634 kV/mm at 150 °C, and its retention rate of Eb reaches 82% in high temperature environment. In addition, tensile strength of the HBOA-100 film is nearly 343 MPa, glass transition temperature is about 334 °C and the thermal stability up to 487 °C. • HBOA and BOA single crystals were obtained, suggesting that the intramolecular hydrogen bond leads to coplanar geometry. • The HBOA monomer and its model compound present layered stacking pattern arising from the coplanar structure. • The dense-layered stacking structure can be constructed in the aromatic polyamide film by the coplanar monomer. • The intrinsic breakdown strength of the homopolymerization film reaches 771 kV/mm and still as high as 634 kV/mm at 150 °C. • This work provides a promising strategy of molecular structure design for high-temperature dielectric polymers.

Cryo-fluorescence micro-optical sectioning tomography for volumetric imaging of various whole organs with subcellular resolution

SummaryOptical visualization of complex microstructures in the entire organ is essential for biomedical research. However, the existing methods fail to accurately acquire the detailed microstructures of whole organs with good morphological and biochemical preservation. This study proposes a cryo-fluorescence micro-optical sectioning tomography (cryo-fMOST) to image whole organs in three dimensions (3D) with submicron resolution. The system comprises a line-illumination microscope module, cryo-microtome, three-stage refrigeration module, and heat insulation device. To demonstrate the imaging capacity and wide applicability of the system, we imaged and reconstructed various organs of mice in 3D, including the healthy tongue, kidney, and brain, as well as the infarcted heart. More importantly, imaged brain slices were performed sugar phosphates determination and fluorescence in situ hybridization imaging to verify the compatibility of multi-omics measurements. The results demonstrated that cryo-fMOST is capable of acquiring high-resolution morphological details of various whole organs and may be potentially useful for spatial multi-omics.

Chitosan-based thermal insulation compressible foam enhanced with high performance of piezoelectric generation and sensing

A series of chitosan (CS)-konjac glucomannan (KGM) foams with excellent thermal insulation property has been prepared using a directional freezing method, which exhibit high strain recovery, excellent piezoelectric generation and sensing properties. Layered lamellar or honeycomb morphologies in CS-KGM foams attributes a low thermal conductivity coefficient of ca. 0.03 W/(m·K). Bridge-like structure that mainly observed in CS-KGM foams from horizontal freezing endows them with excellent compression recovery performance even after 200 compression cycles. This along with piezoelectricity of CS contributes a long-lasting piezoelectric generation performance, ranging from 0.809 to 2.460 V during compression cycle process. Piezoelectric signals generated from pressing with certain strain and rate, finger taping and hand grasping can be sensed profoundly by CS-KGM. As thus, fully renewable source-based CS-KGM foams with outstanding thermal insulation and piezoelectric performance shows great potential in application as wearable thermal insulation and piezoelectric devices.

Experimental investigation of gamma stirling engine coupling to convert thermal to cooling energy in different laboratory conditions

The main aim of this research is to experimentally investigate the two coupled identical ST500 gamma-type Stirling engines and convert thermal energy to cooling energy. Using a new structure and two coupled Stirling engines at different temperatures and pressures and the use of biomass fuel within the 4 -8 bar average pressure range of the first engine heat source, the 1-4 bar average pressure range of the second engine heat sink, and Stirling heat engine temperature range of 480-580 ºC, the effective cooling is obtained in the cooling engine. In doing tests, attempts were made to reach lower than 9 percent error results in different parts of the engine, including insulation, fluid leakage, belt loss, and measurement devices. According to the obtained results, 8 bars increase in the average pressure range of the gas in the first engine heat source, a 1 bar reduction in the average pressure range of the gas in the second engine heat sink, the increased temperature of the heat source up to 580ºC, and the use of the light operating fluid such as helium will affect the generation of cooling up to-16ºC.

Electric control of a canted-antiferromagnetic Chern insulator

The interplay between band topology and magnetism can give rise to exotic states of matter. For example, magnetically doped topological insulators can realize a Chern insulator that exhibits quantized Hall resistance at zero magnetic field. While prior works have focused on ferromagnetic systems, little is known about band topology and its manipulation in antiferromagnets. Here, we report that MnBi2Te4 is a rare platform for realizing a canted-antiferromagnetic (cAFM) Chern insulator with electrical control. We show that the Chern insulator state with Chern number C = 1 appears as the AFM to canted-AFM phase transition happens. The Chern insulator state is further confirmed by observing the unusual transition of the C = 1 state in the cAFM phase to the C = 2 orbital quantum Hall states in the magnetic field induced ferromagnetic phase. Near the cAFM-AFM phase boundary, we show that the dissipationless chiral edge transport can be toggled on and off by applying an electric field alone. We attribute this switching effect to the electrical field tuning of the exchange gap alignment between the top and bottom surfaces. Our work paves the way for future studies on topological cAFM spintronics and facilitates the development of proof-of-concept Chern insulator devices.

The Convective Heat Transfer Performance and Structural Optimization of the Cavity in Energy-Saving Thermal Insulation Windows under Cold Air Penetration Condition

In buildings with the solar heat collection/insulation energy-saving window (SHC/IESW), when the insulation device is placed at night in winter, a double-wall structure façade (DSF) is formed between the glass and the insulation curtain, and the existence of air inlet and outlet leads to cold air penetration. In this paper, the Nusselt number (Nu) correlation and convective heat transfer coefficient (CHTC) of the cavity in SHC/IESW were calculated through an experiment combined with a theoretical analysis. Then, numerical simulation was performed on the fluid dynamics and thermal characteristics caused by air convection in an asymmetrically heated cavity under uniform heat flow conditions, to optimize the SHC/IESW structure and analyze its heat transfer mechanism to solve the problem of convection heat transfer between plates under cold air infiltration. Using the calculation formulas obtained from the experiment, the heat transfer coefficient of SHC/IESW is 1.71 W·m−2·K−1. The numerical simulation results showed that with the increase of air layer thickness, the outlet temperature, the average air velocity of the cavity, and the surface temperature of thermal insulation curtain all decrease; with the increase of inlet width, the outlet temperature and the surface temperature of thermal insulation curtain decreases significantly, while the average air velocity of cavity increases. It can help to weaken the convective heat transfer in the cavity and thus, reduce the total heat transfer coefficient to 1.28 W·m−2·K−1 when the air layer thickness is 12 mm and the inlet width is 1 mm.

Pd-doped PtSe2 monolayer with strain-modulated effect for sensing SF6 decomposed species: a first-principles study

This work employing the first-principles theory investigated the potential of Pd-doped PtSe2 (Pd–PtSe2) monolayer as a sensing material for detection of H2S and SOF2 in the SF6 insulation devices. The Pd dopant is stably trapped on the TPt site of the PtSe2 surface with Eb of −2.37 eV, and the bandgap of Pd–PtSe2 system is reduced to 0.81 eV from that of 1.31 eV of the pristine counterpart. Pd–PtSe2 monolayer has stronger adsorption performance upon SOF2 with Ead of −0.94 eV than H2S with Ead of −0.88 eV, leading to more obvious increase to 0.96 eV in the SOF2 system than that of 0.84 eV in the H2S system. Thus, the much higher sensitivity and more desirable recovery property give rise to the stronger suitability of Pd–PtSe2 monolayer for SOF2 detection, as verified by the I–V curve analysis wherein the electrical resistance and sensing response are seen much larger in the SOF2 system. Moreover, the applied strain is proved as a workable manner to modulate the sensing performance of Pd–PtSe2 monolayer, with tunable QT and Eg obtained in various strains. Our calculations evidence the potential of Pd–PtSe2 monolayer as a promising gas sensor to evaluate the operation status of the SF6 insulation devices, which is beneficial to stimulate more edge-cutting work in the field of gas sensing as well.

Dual-working mode device based on dual-element photonic crystal-stepped concave waveguide

In this study, a Si3N4 on insulator device used for photonic integrated circuits (PICs) is proposed. The dual-working mode device is constructed using a racetrack microring resonator, which is established using a dual-element photonic crystal-stepped concave waveguide. A novel scheme of dual-working modes is realized, and sensing and filtering are performed simultaneously without interference. The results show that a sensitivity of 29 pm K−1 and a line width of 0.28 nm are obtained for the sensor mode. An extinction of 41.8 dB and bandwidth of up to 305.5 nm are achieved in the filter mode. The footprint of the entire device is within 20 μm × 11 μm, which is ultra-compact and suitable for PICs.

Active thermal insulation method based on the principle of source-sink matching

To reduce the heat consumption and improve the energy efficiency of the heat storage system, this paper puts forward a method of active thermal insulation in the thermal energy storage system. A heat source area for absorbing surplus heat is set in the heat insulation process, whose heat is transmitted to the heat sink area. And the source-sink matching strategy is discussed. Theoretically, this system can achieve reasonable heat distribution and thermal insulation at the same time. In this work, the water heater is selected as a typical heat storage device, and the theoretical method is verified by designing an active insulation device in the water heater. The results show that a low-temperature zone is generated in the water heater as a result of the active thermal insulation device, which reduces the external heat dissipation. At the same time, the installation position of the radiator is conducted through energy level and exergy analysis. The studied case shows that the energy level matching coefficient of the novel water heater system can reach 0.49 and the exergy efficiency can be increased to 24% compared to a conventional system. The active thermal insulation method is expected to provide an effective energy-saving idea for a variety of heat storage systems.

Theoretical screening into Ru-doped MoS2 monolayer as a promising gas sensor upon SO2 and SOF2 in SF6 insulation devices

In this article, we based on the first-principles theory explore the sensing and adsorption behaviors of Ru-doped MoS2 (Ru-MoS2) monolayer upon two main decomposed gases in the SF6 insulation device, namely SO2 and SOF2. The simulation results show that the of SO2 adsorption system is calculated as −1.20 eV, indicating that this system is classified as chemisorption, while the of SOF2 adsorption system is obtained as −0.61 eV, implying the physisorption nature. BS and DOS analysis further demonstrates the adsorption performance in two systems and expounds the electronic behavior of Ru-MoS2 monolayer upon gas adsorption. Furthermore, the recovery time for two species at various temperatures shows that Ru-MoS2 monolayer is a potential sensing material on detecting SO2 and manifests the excellent and recyclable performance on scavenging SOF2 due to its weaker binding force. Apart from that, the frontier molecular orbital theory provides the basic sensing mechanism of the Ru-MoS2 monolayer as a resistance-type sensor upon two typical gases, which is quite essential to promote the steady operation of the power system. Highlights Geometric structure and electronic behaviour of Ru-doped MoS2 monolayer are studied Expound the sensing mechanism of Ru–MoS2 monolayer upon SO2 and SOF2 Explore the recovery property of Ru–MoS2 monolayer toward SO2 and SOF2 Analyse the conductivity change of isolated and gas adsorbed Ru–MoS2 surface by using the frontier molecular orbital theory.

Opportunities in topological insulator devices

Topological insulators (TIs) are expected to be a promising platform for novel quantum phenomena, whose experimental realizations require sophisticated devices. In this Technical Review, we discuss four topics of particular interest for TI devices: topological superconductivity, quantum anomalous Hall insulator as a platform for exotic phenomena, spintronic functionalities, and topological mesoscopic physics. We also discuss the present status and technical challenges in TI device fabrications to address new physics.

Origin of the Out-of-Equilibrium Body Potential In Silicon on Insulator Devices With Metal Contacts

This work addresses the origin of the transient body potential variation in silicon on insulator (SOI) with deposited metal contacts, under back-gate bias sweep from accumulation to inversion. The phenomenon arises from the difficulty to inject carriers into the silicon film due to the Schottky contact between the metal and the low p-type doped silicon. The Schottky diode current is controlled by the back-gate voltage, which fixes the potential at the bottom of the low-doped film. When the back-gate voltage drives the silicon film towards inversion, the limited current from the Schottky contact induces a deficit of minority carriers in the film and brings the body potential in an out-of-equilibrium regime. This phenomenon will be reproduced with numerical modelling based on Poisson and continuity equations, including the quasi-Fermi potential. The transient character and its dependence on the Schottky barrier height will be evidenced. A simple and effective combination of the classic Schottky current equation and inversion current calculated from the Lambert function, as in fully depleted (FD)-SOI MOSFETs, confirms the origin of the effect.

Adsorption properties of CS2 and COF2 on the SF6 adsorbent surfaces: A DFT study

As the typical carbon-containing decomposition components of SF6 under partial discharge in high-voltage insulation devices, CS2 and COF2, will not only corrode devices, but also pollute the environment. Remove these gases through SF6 adsorbent is an effective approach to eliminate the above hazards. In this paper, the adsorption performance of CS2 and COF2 on α-Al2O3 (0 0 0 1) surface was calculated by first-principle based density functional theory, including the adsorption enthalpy change, charge transfer and structural parameters, and five relatively stable adsorption structures were initially obtained through analysis. Results indicate that all adsorption processes are exothermic. To further understand the adsorption mechanism, the density of states, frontier molecular orbital and deformation charge density diagram were analyzed. Calculations show that both CS2 and COF2 has a fine adsorption effect on α-Al2O3 (0 0 0 1) surface, besides, for CS2, it is easier to be adsorbed on α-Al2O3 (0 0 0 1) surface through C atom while there is no significant difference in performance parameters of the adsorption configuration for COF2. Furthermore, frontier molecular orbital analysis also confirmed that the adsorbed system is more stable. This work provide theoretical basis for the experiments of SF6 adsorbents adsorbing typical carbon-containing decomposition components.

InP3 Monolayer as a Promising 2D Sensing Material in SF6 Insulation Devices.

In this letter, we perform a first-principles study on the adsorption performance of the InP3 monolayer upon three SF6 decomposed species, including SO2, SOF2, and SO2F2, to investigate its potential as a resistance-type, optical or field-effect transistor gas sensor. Results indicate that the InP3 monolayer exhibits strong chemisorption upon SO2 but weak physisorption upon SO2F2. The most admirable adsorption behavior is upon SOF2, which provides a favorable sensing response (−19.4%) and recovery property (10.4 s) at room temperature as a resistance-type gas sensor. A high response of 180.7% upon SO2 and a poor one of −1.9% upon SO2F2 are also identified, which reveals the feasibility of the InP3 monolayer as a resistance-type sensor for SO2 detection with recycle use via a heating technique to clean the surface. Moreover, the InP3 monolayer is a promising optical sensor for SO2 detection due to the obvious changes in adsorption peaks within the range of ultraviolet and is a desirable field-effect transistor sensor for selective and sensitive detection of SO2 and SOF2 given the evident changes of QT and Eg under the applied electric field.

Spin-Wave Driven Bidirectional Domain Wall Motion in Kagome Antiferromagnets.

We predict a mechanism to controllably manipulate domain walls in kagome antiferromagnets via a single linearly polarized spin-wave source. We show by means of atomistic spin dynamics simulations of antiferromagnets with kagome structure that the speed and direction of the domain wall motion can be regulated by only tuning the frequency of the applied spin wave. Starting from microscopics, we establish an effective action and derive the corresponding equations of motion for the spin-wave-driven domain wall. Our analytical calculations reveal that the coupling of two spin-wave modes inside the domain wall explains the frequency-dependent velocity of the spin texture. Such a highly tunable spin-wave-induced domain wall motion provides a key component toward next-generation fast, energy-efficient, and Joule-heating-free antiferromagnetic insulator devices.

Microparticles separation using acoustic topological insulators

Acoustic topological insulators have exotic states on their topological interfaces, which provide an extraordinary approach to control the sound wave with a backscattering-immune property. Non-contact particle manipulations play an important role in life science, and acoustic tweezers are gaining increasing attention due to their better biological compatibility. In this Letter, we use an acoustic topological insulator to achieve non-contact particle manipulations such as microparticle trapping and separation. Based on the Su–Schrieffer–Heeger (SSH) model, we can obtain the topological interfacial states. Then, we calculate the flow distribution fields and acoustic radiation force distribution fields, and the results show that we can separate two particles with the same size and density. Our study provides a guide to design topological insulator devices and achieves non-contact label-free microparticle manipulations, which exhibits enormous application potential in the biomedical field.

Effect of an Insulation Device in Preventing Hypothermia during Magnetic Resonance Imaging Examinations for Dogs and Cats under General Anesthesia.

Simple SummaryMagnetic resonance imaging examinations require general anesthesia, and it is difficult to prevent a decrease in body temperature because a machine for warming the body cannot be placed in the magnetic resonance imaging room, which must have a low room temperature. In this study, we created a heat insulating device that does not affect magnetic resonance imaging and examined the effectiveness of this device for dogs and cats undergoing magnetic resonance imaging examinations. In the dogs and cats wearing bubble wrap and down cloth blanket, the decrease in body temperature was minimal. The heat insulating device developed in this study protected the animals from the cold air and prevented heat loss from the body surface, minimizing a decrease in body temperature. The results obtained in this study suggest that dogs and cats requiring magnetic resonance imaging can be protected from hypothermia due to general anesthesia without the need for special machinery.Dogs and cats under general anesthesia may develop hypothermia. When performing a magnetic resonance imaging (MRI) examination, it is not possible to place a magnetic material in the MRI room, and MRI equipment requires a low room temperature. This study investigated the effectiveness of a heat insulating device that prevented hypothermia during MRI examinations in dogs and cats. The animals that underwent MRI examinations under general anesthesia were divided into control groups (no covering) and heat insulating groups (wearing bubble wrap and down cloth blankets), and their body temperatures were measured before and after the MRI examinations. The changes in body temperatures were as follows: control dogs (n = 17), median of −1.0 (from −2.5 to 0.3) °C; heat insulated dogs (n = 7), −0.3 (from −0.8 to 0.2) °C; control cats (n = 14), −1.85 (from −2.7 to −0.6) °C; and heat insulated cats (n = 12), −0.8 (from −1.5 to −0.1) °C. These results revealed that the bubble wrap and down cloth blanket significantly prevented hypothermia and heat loss from the body surface during MRI examinations of dogs and cats.

INVERSE DESIGN OF PHONONIC CRYSTALS BY ARTIFICIAL NEURAL NETWORKS

Phononic crystals represent a special kind of artificial periodic composite materials. The peculiar band-gap characteristics provide potential applications in the vibration reduction, wave filtering, sound insulation and acoustic functional devices. However, how to accurately manipulate acoustic and elastic waves is a major challenge for designing phononic crystals. The conventional design method is based on matching the specific application requirements by analyzing and adjusting the geometrical and material parameters of the phononic crystal structures. This method has a low efficiency and can hardly achieve the optimal performance. An artificial neural networks inverse design method for muti-layered phononic crystals based on the Softmax logistic regression and the multi-task learing is proposed in this study. In the proposed method, the Softmax logistic regression is used to choose the material type and the multi-task learing is used to determine the material distribution for each area of the multi-layered structure, so the phononic crystal reverse design problem is transformed into the classification problem of multi-component materials for the unit cell by the proposed method. First, a large number of the samples for the topological structures are randomly generated. Second, the band-gap structures of the samples are obtained by parallel finite element calculation. After that, the relationship between the topological structures and the band-gaps are established by the neural networks. Finally, the trained neural network is ultimately employed to design a phononic crystal structure with the targeted band-gaps, that is, the targeted band gap is used as the input of the neural network, and the trained neural network will output the corresponding cell topology of the phononic crystal unit cell directly. The example shows that the proposed method can obtain one-dimensional (1D) phononic crystals with the targeted band-gaps for the specified application requirements quickly and efficiently. This method provides a new way for the inverse design of phononic crystals.

Skin tightening by an insulated microneedle radiofrequency device combined with lower blepharoplasty: a randomized fellow eye comparison study

Skin tightening by an insulated microneedle radiofrequency device combined with lower blepharoplasty: a randomized fellow eye comparison study