Conductive Loss Research Articles

Ultrahigh efficiency and energy density in tri-layered ferroelectric polymer composites utilizing ultralow loading of micro-sized plates

Ferroelectric-based composites have demonstrated tremendous potential in electrostatic capacitor owing to their exceptional dielectric characteristics. However, it is extremely challenging to attain desirable energy density (Ue) and above 95% efficiency (η) under low electric fields in the ferroelectric polymer-based composites because of the dominating electrical conduction loss. Herein, ferroelectric polymer composites consisting of SrTiO3@SiO2 plates/(PVDF-co-HFP) as the inner layer and polycarbonate (PC) as the outer polymer layers are elaborately proposed. The vital role of the multiple interlaminar interfaces (electrode/dielectric interface and interlayer interface) on the reduction of conduction loss and improvement of corresponding energy storage properties of the ferroelectric polymer is verified by experimental and theoretical simulations. The resulting composite with an ultralow loading of SrTiO3@SiO2 plates (0.5 vol%) displays a record high capacitive performance (∼8.73 J/cm3) at above 95% η under the low electric field of 280 MV/m1, indicating an enormous ∼118% increment of the maximal Ue over the commercial bench-mark biaxially oriented polypropylene (∼4 J/cm3) and far outperforming those of the polymer-based dielectrics reported to date. Along with fast discharge time (9 ns), this contribution presents a versatile and competitive technology for fabricating composites with exceptional energy storage capabilities operating under low electric fields.

Nitrogen Boil-Off Method of Measuring AC Losses in Twisted-Stacked HTS Conductor

Nitrogen Boil-Off Method of Measuring AC Losses in Twisted-Stacked HTS Conductor

A Mechanism for Ice Layer Formation in Glacial Firn

AbstractThere is ample evidence for ice layers and lenses within glacial firn. The standard model for ice layer formation localizes the refreezing by perching of meltwater on pre‐existing discontinuities. Here we argue that even extreme melting events provide insufficient flux for this mechanism. Using a thermomechanical model we demonstrate a different mechanism of ice layer formation. After a melting event when the drying front catches up with the wetting front and arrests melt percolation, conductive heat loss freezes the remaining melt in place to form an ice layer. This model reproduces the depth of a new ice layer at the Dye‐2 site in Greenland. It provides a deeper insight into the interpretation of firn stratigraphy and past climate variability. It also improves the simulation of firn densification processes, a key source of uncertainty in assessing and attributing ice sheet mass balance based on satellite altimetry and gravimetry data.

A composite control method of PWM and phase shift for a three-level DC-DC converter

Abstract This research introduces a control strategy for the Three Level Active Half Bridge (TL-DAHB) DC-DC converter that integrates PWM combined with phase-shift control. This composite control method precisely regulates the output voltage by adjusting the phase-shift duty cycle between the input and output sides. Additionally, the application of the PWM control loop optimizes the duty cycle of the switches, effectively reducing the current stress on the converter during operation, improving transmission efficiency, and decreasing conduction losses of the switches. These enhancements boost the overall performance and the reliability of the converter. With its excellent voltage regulation capabilities and safety features, this converter is an ideal choice in the field of power conversion, especially in applications that demand high levels of stability and safety.

Understanding pediatric inpatient conductive hearing loss: An analysis of patient demographics

ObjectiveHearing loss is a common sensory impairment in children that affects quality of life and development. Early intervention, such as hearing aids and communication therapies, can help children overcome these challenges and lessen the impact on their development. The objective of this study was to identify specific patient demographic factors correlated with the prevalence of pediatric conductive hearing loss. Study designThe study utilized the Kids' Inpatient Database (KID) by the Agency for Healthcare Research and Quality which collects inpatient information from hospitals for patients under 21 years old. We included all patients discharged in 2016 diagnosed with conductive hearing loss, and excluded neonatal patients discharged within 28 days of birth. MethodsStatistical analyses were performed using R Studio and IBM SPSS Statistics. Weighted odds ratios were calculated for conductive hearing loss in relation to race and income, and a multivariate regression analysis examined associations between demographic variables and race categories in conductive hearing loss. ResultsThe prevalence of conductive hearing loss (CHL) in pediatric patients in 2016 was 51.62 cases per 100,000 patients. Non-Hispanic White patients had the highest prevalence, while Black patients had the highest likelihood of CHL compared to the overall population. Lower income levels were associated with a decreased probability of CHL diagnosis. After adjusting for age, sex, hospital region, insurance, and income on multivariate analysis, White and Black patients were less likely to be diagnosed with CHL. Furthermore, patients in specific income quartiles also had lower CHL likelihood compared to the general population. ConclusionWhile Black patients had a higher likelihood of being diagnosed with CHL than the general population, socioeconomic factors such as income greatly influenced the likelihood of CHL diagnosis. Other significant factors included income, region of the country, sex, and age. Further research is needed to better understand and address healthcare disparities related to pediatric hearing loss.

Optimization Method of SiC MOSFET Switching Trajectory Based on Variable Current Drive

Silicon carbide (SiC) MOSFETs exhibit superior performance compared to traditional silicon (Si) MOSFETs, characterized by faster switching speeds, lower on-resistance, higher breakdown voltage, and greater operational temperature tolerance. These attributes make SiC MOSFETs highly suitable for applications in electric vehicles, charging stations, and mobile devices. However, their rapid switching speed can intensify current and voltage overshoot and oscillations during device switching, leading to increased device losses or potential damage. To address this issue, this paper proposes a current-type active gate drive (AGD) circuit. The circuit first detects the rate of change in the drain current and drain-source voltage. Subsequently, it employs an analog amplifier circuit and adjustable drive resistors to decelerate the rate of change in the drain-source voltage and drain current. As a result, overshoot and oscillation in the drain-source voltage and drain current are mitigated. Experimental results demonstrate that the proposed AGD circuit can reduce drain current overshoot by 60%, drain-source voltage overshoot by 15.38%, and waveform oscillations. Additionally, the AGD circuit decreases conduction and turn-off losses by 24% and effectively mitigates electromagnetic interference (EMI) issues within the frequency range of 0.1 to 3 MHz.

Surface Acoustic Wave Sensors for Wireless Temperature Measurements above 1200 Degree Celsius.

High-temperature wireless sensing is crucial for monitoring combustion chambers and turbine stators in aeroengines, where surface temperatures can reach up to 1200 °C. Surface Acoustic Wave (SAW) temperature sensors are an excellent choice for these measurements. However, at extreme temperatures, they face issues such as agglomeration and recrystallization of electrodes, leading to loss of conductivity and reduced quality factor, hindering effective wireless signal transmission. This study develops an LGS SAW sensor with a Pt-10%Rh/Zr/Pt-10%Rh/Zr/Pt-10%Rh/Zr multilayer composite electrode structure to address these challenges. We demonstrate that the sensor can achieve wireless temperature measurements from room temperature to 1200 °C with an accuracy of 1.59%. The composite electrodes excite a quasi-shear wave on the LGS substrate, maintaining a Q-factor of 3526 at room temperature, providing an initial assurance for the strength of the wireless interrogation echo signal. The sensor operates stably for 2.18 h at 1200 °C before adhesion loss between the composite electrode and the substrate causes a sudden increase in resonant frequency. This study highlights the durability of the proposed electrode materials and structure at extreme temperatures and suggests future research to improve adhesion and extend the sensor's lifespan, thereby enhancing the reliability and effectiveness of high-temperature wireless sensing in aerospace applications.

Construction of molecular semiconductor traps to improve the energy storage performance of novel cyanopolynorbornene

To meet the demand of film capacitors in harsh condition applications, research workers devote their effort to develop high temperature resistant polymer dielectrics with high energy density. In this paper, a new type of dipole glass polymer, polynorbornene containing cyano-group side chain (PDMBN) is prepared by ring opening metathesis polymerization. The high dipole moment of the cyano-group possesses high polarization, resulting in that the discharge energy density (Ud) of 8.6 J/cm3 and efficiency of 84 % are found in the PDMBN at room temperature. Via using three organic semiconductors with increased electron affinity (NBTI, NBTI-SO2 and NBTI-2SO2) as the fillers, the energy storage properties of PDMBN matrix are further improved due to the binding effect of free electrons. In addition, the interfacial barrier height is inversely proportional to the temperature, electric field and electron affinity of fillers. As a result, 0.7- wt% NBTI-SO2/PDMBN achieves a maximal Ud of 11.6 J/cm3 at 600 MV/m and room temperature. At elevated temperatures, the conduction loss of polymer PDMBN increases sharply, causing a rapid decline in energy storage performance. Nevertheless, the maximum Ud of 0.7-wt%NBTI/PDMBN composite film at 100 °C and 150 °C can reach 6.2 J/cm3 and 4.5 J/cm3, respectively. This study is helpful for the design of polynorbornene dielectrics, and provides an important reference for the construction of carrier traps in polymer dielectrics at high temperature.

Synergistic Layered Design of Aerogel Nanocomposite of Graphene Nanoribbon/MXene with Tunable Absorption Dominated Electromagnetic Interference Shielding.

Electromagnetic pollution presents growing challenges due to the rapid expansion of portable electronic and communication systems, necessitating lightweight materials with superior shielding capabilities. While prior studies focused on enhancing electromagnetic interference (EMI) shielding effectiveness (SE), less attention is given to absorption-dominant shielding mechanisms, which mitigate secondary pollution. By leveraging material science and engineering design, a layered structure is developed comprising rGOnR/MXene-PDMS nanocomposite and a MXene film, demonstrating exceptional EMI shielding and ultra-high electromagnetic wave absorption. The 3D interconnected network of the nanocomposite, with lower conductivity (10-3-10-2 S/cm), facilitates a tuned impedance matching layer with effective dielectric permittivity, and high attenuation capability through conduction loss, polarization loss at heterogeneous interfaces, and multiple scattering and reflections. Additionally, the higher conductivity MXene layer exhibits superior SE, reflecting passed electromagnetic waves back to the nanocomposite for further attenuation due to a π/2 phase shift between incident and back-surface reflected electromagnetic waves. The synergistic effect of the layered structures markedly enhances total SE to 54.1 dB over the Ku-band at a 2.5 mm thickness. Furthermore, the study investigates the impact of hybridized layered structure on reducing the minimum required thickness to achieve a peak absorption (A) power of 0.88 at a 2.5 mm thickness.

Microstructure evolution and excellent electromagnetic wave absorption performance of SiBCN fibers

In this work, SiBCN fibers with excellent electromagnetic wave (EMW) absorption performance were fabricated using electrospinning technology, followed by curing, pyrolysis, and heat treatment. Microstructure evolution and EMW absorption performance of SiBCN fibers after heat treatment at 1200–1600 °C were investigated. After heat treatment at 1200 °C, the conductive turbostratic C was precipitated from amorphous SiBCN fibers, resulting in minimum reflection loss (RLmin) reaching −63 dB and efficient absorption bandwidth (EAB) reaching 5.2 GHz. While turbostratic C and nano-SiC grains were simultaneously precipitated from SiBCN fibers heat treated at 1400 °C, and the RLmin reached −67 dB. The excellent EMW absorption performance of SiBCN fibers was mainly attributed to the synergistic effect of conductive loss, dipole polarization, and interfacial polarization. This work can guide the fabrication of high-performance EMW-absorbing ceramic fibers.

Innovative enhancements in polymer nanocomposites: Integrating ZnO nanorods into Hydroxypropyl methylcellulose/Polyvinyl pyrrolidone blend for advanced energy storage devices

Polymer nanocomposites are promising for various industrial and scientific applications due to their flexibility, diverse functionalities, and unique properties. In this study, zinc oxide nanorods (ZnO NRs) were incorporated into a blend of polymers (Hydroxypropyl methylcellulose - HPMC and Polyvinyl pyrrolidone - PVP) using a solution-casting technique, with concentrations varying from 2 % to 8 % by weight. Transmission electron microscopy (TEM) revealed that the ZnO NRs had an average diameter of 140 nm and a length of 3.22 μm. X-ray diffraction (XRD) analysis showed reduced crystallinity in the samples as the ZnO NR content increased. Fourier-transform infrared spectroscopy (FTIR) indicated changes in vibrational peaks due to interactions between functional groups in the blend and the nanorods. The addition of ZnO NRs significantly influenced the optical bandgap energies and UV/visible light absorption spectra of the samples. The bandgap of the nanocomposites significantly decreased upon ZnO NR incorporation, with direct and indirect bandgaps ranging from 5.19 to 4.70 eV and 4.74–3.66 eV, respectively. Electrical conductivity and dielectric characteristics were assessed across frequencies ranging from 0.1 to 10 MHz, revealing increasing AC conductivity, dielectric permittivity, and dielectric loss with higher ZnO NR content. Notably, at 10 Hz, the electrical conductivity increased from 3.5 × 10⁻12 S/m to 3.62 × 10⁻10 S/m upon loading with ZnO NR. The combination of adjustable optical bandgaps, frequency-dependent AC conductivity, and a wide range of tunable permittivity highlights the potential of these HPMC/PVP-ZnO NR nanocomposites for developing flexible optoelectronic and energy storage devices.

Fabrication of 3D micro-flower structured BiFeO3 growing on rGO nanosheets for enhanced electromagnetic wave absorption

Because of the distinctive structure and superior properties of graphene and its derivatives, which have been widely studied in the field of electromagnetic wave (EMW) absorption. However, the impedance mismatch caused by excessive conductivity of graphene and the single loss mechanism greatly limit its application. Herein, we prepare 3D micro-flower structured BiFeO3 grown on graphene oxide nanosheets (BiFeO3-rGO) to both improve the impedance matching and introduce abundant interfacial polarization loss. Moreover, the electromagnetic parameters of the materials are adjusted by changing the ratio of BiFeO3 and rGO to obtain prominent EMW absorption and satisfactory impedance matching performances. More importantly, the conductive loss and polarization loss of the materials are quantitatively analyzed to further explore the loss mechanism of EMW. As a result, the fabricated BiFeO3-rGO 1:1 and BiFeO3-rGO 2:1 both achieve remarkable EMW absorption performances with strong reflection loss (RL) of −49.5 and −45.3 dB and broad effective absorption bandwidth (EAB) of 8.12 and 8.08 GHz with a low filling contents of 5 %. This work demonstrates that polarization loss is as important as conduction loss and the key point to further improve the EMW absorption performance is to crack the code of polarization loss.

A combined strategy to constructure MoX2 (X=Se and S)-based core@shell structure flower-like multicomponent nanocomposites for boosted conduction loss, polarization loss and microwave absorption capacities

Interfacial effects or/and magnetic/dielectric synergy can be utilized effective strategies to improve electromagnetic wave (EMW) attenuation. Herein, using CoNi nanospheres as precursor, core@shell CoNi@C nanospheres could be efficiently fabricated via a facile polymerization and subsequent thermal treatment. And core@shell CoNi/NiSe2/Co9Se8@C@MoSe2 and CoNi2S4/Co9S8@C@MoS2 flower-like multicomponent nanocomposites (MCNCs) were fabricated via hydrothermal reaction amongst the obtained CoNi@C, Mo and Se/S sources. The generated carbon acting as protective layer was verified to greatly restrain the selenization of CoNi nanospheres during the formation of MoSe2 nanosheets, generating CoNi/NiSe2/Co9Se8@C@MoSe2. And the complete sulfidation of CoNi alloys led to the formation of CoNi2S4/Co9S8@C@MoS2. Because of their boosted impedance matching, conductive and polarization loss abilities, the acquired flower-like MoX2 (X = Se and S)-based MCNCs displayed greatly improved EMW absorption characteristics (EMWACs) compared with their precursors. Especially, the extraordinary synergistic effect generated into the magnetic/dielectric MCNCs contributed to outstanding EMWACs of CoNi/NiSe2/Co9Se8@C@MoSe2 flower-like MCNCs. Accordingly, our findings provided a combined strategy to simultaneously make the most of magnetic/dielectric synergistic and interfacial effects for boosted conduction loss, polarization loss and EMWACs.

Hierarchical multi-interface Co1-xS/Co9S8@C hollow microsphere for enhancing dielectric polarization as an efficient microwave absorber

Recently, close attention has been devoted to exploring highly efficient microwave absorbing materials (MAMs). Owing to their tunable dielectric properties and controllable structure, materials doped with heteroatoms have been regarded as promising absorbers. Herein, the Co@C, CoSe2@C, and hierarchical Co1-xS/Co9S8@C hollow microspheres were prepared using hydrothermal and subsequent carbonization, selenium, and vulcanization processes, respectively. The existence of anionic sites immensely affects the permittivity and conductivity of a composite. As a result, CoSe2@C and Co1-xS/Co9S8@C hollow microspheres showed improved conductivity and dielectric losses. Particularly, due to the multiphase transformation in the vulcanization process, the Co1-xS/Co9S8@C hollow microsphere possessed numerous heterogeneous interfaces and rich lattice defects, which led to local electronic redistribution and reinforced dielectric polarization. It exhibited a minimum reflection loss (RLmin) of −61.0 dB at a thinner thickness of 2.0 mm. This study contributes to the insight into the polarization loss mechanisms of multi-component and heteroatom doping composites and stimulates the design of high-efficiency MAMs.

The Effect of Premedication with Metoprolol on the Surgical Field during Endoscopic Stapedectomy.

Otosclerosis is one of the most frequent causes of conductive hearing loss in adults. Surgical treatment is considered to be the gold standard for this disease. Endoscopic stapedectomy is a new approach for the treatment of otosclerosis that requires a bloodless field. To determine whether the routine use of β blockers as a premedication can improve the operative field in endoscopic stapedectomy or not. Sixty patients aged from 18 to 50 years, undergoing endoscopic stapedectomy, were included in this prospective, randomized, double blinded, placebo-controlled study. Patients were randomly assigned to receive either metoprolol 100mg ( group 1) or a placebo, vitamin tablet, (group 2) 60min before surgery. The age, gender, body weight and ASA physical status were comparable between the two groups. The average blood loss in the placebo group was significantly greater than in the metoprolol group, but the time of operation in the metoprolol group was not significantly shorter. The surgical field was assessed using the Fromme-Boezaart scale, and those who received metoprolol had considerably cleaner (p0.001) surgical fields. The mean arterial pressure (MAP) didn't differ statistically significant at basal measurement up to 30min after anesthesia induction while it was significantly lower in the metoprolol group after 30min of induction up to end of surgery (p < 0.001). The heart rate was also significantly lower (p < 0.001) in patients who received metoprolol from prior to anesthesia induction up to end of surgery. metoprolol significantly improves visual clarity and hemodynamics during endoscopic stapedectomy.

Porous-multilayered Ti3C2Tx MXene hybrid carbon foams for tunable and efficient electromagnetic wave absorption

The rapid development of modern wireless communication technology makes electromagnetic wave pollution increasingly serious, necessitating the development of high-performance electromagnetic wave-absorbing materials. This study introduces a Ti3C2Tx MXene hybrid carbon foam (HCF) that exhibits a tunable and efficient electromagnetic wave absorption performance. The HCF features a porous, multilayered structure, which enhances its multi-reflection properties, and a heterogeneous interface between the carbon foam and MXene boosting its dielectric loss. By regulating the content of MXene, the ratio of polarization loss to conduction loss can be regulated to achieve better impedance matching. As a result, the HCF demonstrated superb electromagnetic wave absorption performance with RLmin = −72.25 dB and EABmax = 6.55 GHz. Furthermore, the minimum absorption frequency domain could be tuned within 8–14 GHz by varying the MXene content. The performance in radar wave absorption and electromagnetic-thermal conversion (ramp rate 85.81 °C/s from RT to 200 °C) proves that HCF is an efficient and reliable electromagnetic wave absorber, suitable for radar technology, microwave heating, and communication systems applications.

High-throughput phase field simulation and machine learning for predicting the breakdown performance of all-organic composites

All-organic dielectric polymers are materials of choice for modern power electronics and high-density energy storage, and their performance can be significantly improved by doping trace amounts of organic molecular semiconductors with strong electron-affinity energy to suppress charge conduction losses. Insight into the breakdown mechanism of polymers/organic molecular semiconductor composites is essential for the design of high-performance dielectric polymers. This study investigates the impact of the doping concentration of organic molecular semiconductors, dielectric constants, and trap depths on the breakdown performance of dielectric polymers under high temperature and electric fields. A modified phase-field model, incorporating deep traps and carriers’ coulomb capture radius, has been developed to facilitate high-throughput simulations of electrical breakdown in polymer/organic molecular semiconductor composites. This work accurately predicted the breakdown strength of all-organic composites using high-throughput phase-field simulation data as input for machine learning, which provides crucial theoretical support for designing all-organic composite dielectric polymers for energy storage capacitors under extreme conditions.

Interface engineering of polymer composite films for high-temperature capacitive energy storage

Polymer film capacitors encounter challenges in harsh conditions of high temperatures and electric fields because of large conduction loss and degraded breakdown strength (Eb). Herein, an interface engineering strategy is proposed to fluorinate the interfaces between the polyetherimide (PEI) matrix and wide bandgap boron nitride nanosheets (BNNSs) fillers. The composite films exhibit high-performance capacitive energy storage with a remarkable energy density of 5.73 J/cm3 and an ultrahigh efficiency of 91.22 % in conditions of 575 kV/mm and 150 °C. By adopting interfacial fluorination, the band structure of BNNSs is tailored to achieve a type II band alignment with PEI, promoting the dual trapping for both electrons and holes. It highly suppresses leakage current and reduces conduction loss. Typically, introducing fillers can compromise the properties of interfacial layers, creating weak points that trigger breakdown. Conversely, fluorinated interfaces exhibit an increased Young’s modulus and a reduced dielectric constant. According to the electromechanical breakdown theory, the interfacial Eb is increased. The breakdown phase propagation along the interfaces is thereby impeded, ultimately resulting in a further increase in overall Eb, reaching up to 589 kV/mm at 150 °C. Fluorinated interface engineering addresses interfacial challenges posed by fillers, enabling high-temperature energy storage capability in PEI-based capacitors.

Zirconium carbide modified SiOC composites with porous lamellar structures for broadband microwave absorption and thermal stability

The inherent dielectric properties and thermal stability of transition metal carbides (TMCs) have generated significant interest because of their potential use in electromagnetic (EM) wave applications at various temperatures. However, the high relative complex permittivity and conductivity of TMCs can cause impedance mismatch issues when utilized as absorbers, thereby limiting their effectiveness in absorbing EM waves. To solve these problems, ZrC/ZrO2–SiOC composites with a porous lamellar structure were prepared using polymer-derived ceramics (PDC) technology, which involved dispersing zirconium carbide (ZrC) into modified polysiloxane (PSO). The resulting ZrC/ZrO2–SiOC composite (with 5 wt% ZrC content sintered at 900 °C) achieved remarkable EM wave absorption performance, with a minimum reflection loss (RLmin) of −33.52 dB at 13.0 GHz and an effective absorption bandwidth (EAB) extending up to 7.75 GHz. This exceptional absorption of EM waves is due to the synergistic interplay of various factors such as interface polarization, dipole polarization, and conduction loss. Moreover, the composites exhibit a minimal weight loss of less than 2 % when exposed to air at temperatures ranging from 25 to 1200 °C. This study not only broadens the application possibilities of TMC materials in microwave absorption but also highlights their potential for further improvement and deployment in high-temperature environments.

Micro-sized hexapod-like CuS/Cu9S5 hybrid with broadband electromagnetic wave absorption

Reasonable manipulation of component and microstructure is considered as a potential route to realize high-performance microwave absorber. In this paper, micro-sized hexapod-like CuS/Cu9S5 composites were synthesized via a facile approach involving the solvothermal method and subsequent sulfuration treatment. The resultant CuS/Cu9S5 exhibited superb microwave absorbing capacity with a minimum reflection loss (RLmin) of -59.38 dB at 2.7 mm. The maximum effective absorption bandwidth (EABmax) was 7.44 GHz (10.56–18 GHz) when the thickness was reduced to 2.3 mm. The outstanding microwave absorbing ability of CuS/Cu9S5 composites is mainly related to its unique hexapod shape and the formation of heterogeneous interfaces. The unique hexapod shape significantly promotes the multi-reflection of the incident electromagnetic wave (EMW) increasing the attenuation path of EMWs in the material. Heterogeneous interfaces between CuS/Cu9S5 enable powerful interface polarization, contributing to the attenuation of EMWs propagating in the medium. In addition, the EMW absorption performance of CuS/Cu9S5 composites is also inseparable from the conduction loss. This study provides a strong reference for the research of EMW absorbent materials based on transition metal sulfides.