Subjects: Materials Science >> Electronic, Optical and Magnetic Materials submitted time 2023-10-26
Abstract: Triboelectric nanogenerators (TENGs) are promising self-powering supplies for a diverse range of intelligent sensing and monitoring devices, especially due to their capability of harvesting electric energy from low frequency and small-scale mechanical motions. Inspired by the fact that contact-separation mode TENGs with small contact areas harvest high electrical outputs due to fringing effect, this study employed discontinuity on the dielectric side of contact-separation mode TENGs to promote fringing electric fields for the enhancement of electrical outputs. The results reveal that the TENGs with more discontinuities show higher overall electric performance. Compared to pristine TENGs, the TENGs with cross discontinuities increased the surface charge by 50% and the power density by 114%. However, one should avoid generating discontinuities on tribonegative side of TENGs using metal blade within a positive-ion atmosphere due to the neutralization through electrically conductive metal blade. The computational simulation validated that the TENGs with discontinuities obtained higher electrical outputs, and further investigated the effect of discontinuity gap size and array distance on TENGs performance. This study has provided a promising method for the future design of TENGs using discontinuous structures.
Peer Review Status:Awaiting Review
Subjects: Materials Science >> Electronic, Optical and Magnetic Materials submitted time 2023-08-23 Cooperative journals: 《中国科学院院刊》
Abstract: 光谱覆盖广的突出优点,是助力实现光电子信息产业 突破的关键基础材料。为抢占“镓体系”半导体科技制高点,文章在分析“镓体系”半导体科技的战略意 义、重大需求和国内外发展态势基础上,从建制化科研组织、基础研究、自主可控的平台建设等方面对我国 发展“镓体系”半导体科技提出了政策建议。
Subjects: Materials Science >> Electronic, Optical and Magnetic Materials submitted time 2023-03-01
Abstract: The intrinsic high frequency permeability spectra of ferromagnetic composites containing different volume fractions of iron and cobalt have been simulated. A law (called Mghan’s law) is proposed to explain the simulated results by assuming that there are plenty of LLG (Landau-Lifshitz-Gilbert) type natural resonances contributing to the intrinsic permeability spectra. The results clearly show that the spectra strongly depend on the distribution of local effective magnetic field, the interaction between the magnetic particles, the inhomogeneous damping constant of LLG precession, and the initial equilibrium states. Especially, the effect of particles shape distribution in each sampling on the local effective magnetic field. In view of this fact: it is absolutely impossible to have the same effect from these factors when someone prepares several measurement samples, an uncertainty principle is believed to hold for measuring the intrinsic permeability of an electromagnetic (EM) composite. Therefore, this law tells us that it should be cautious when comparing or evaluating the EM properties of composites (for instance, EM wave absorbing composites). Memory effect can be used to restore the intrinsic high frequency permeability for a specific defunct composite sample.
Peer Review Status:Awaiting Review
Subjects: Materials Science >> Electronic, Optical and Magnetic Materials submitted time 2022-10-26 Cooperative journals: 《桂林电子科技大学学报》
Abstract: In order to improve the magnetic properties of permanent magnetic films and increase the utilization of Ce elements,
the magnetization reversal process of the dual main phase Nd2Fe14B/Ce2Fe14B periodic multilayer film has been
simulated, and the influence of the thickness of the magnetic layer and the number of layers of the multilayer film on the
magnetic properties of the periodic multilayer film during the magnetization reversal process has been systematically studied.
The remanence, coercivity, hysteresis loop of the system and the energy change during the magnetization reversal process
and the magnet are analyzed. The coercive force mechanism will provid a certain reference for the preparation of high-performance
magnets with high Ce content in the future. The research results show that when the thickness of the fixed multilayer
film is constant and the number of the fixed multilayer film is constant, with the increase of the thickness of the magnetic
layer, the coercive force and maximum magnetic energy product of the system gradually decrease; The coercive force
mechanism is mainly dominated by nucleation; when other conditions are the same, the coercivity and magnetic energy product
of the parallel-oriented periodic multilayer film are better than those of the perpendicularly-oriented periodic multilayer
film; the total thickness of the periodic multilayer film increases Will reduce the influence of orientation on coercivity. The
research results will help to deepen understand the magnetization reversal mechanism of the dual-phase Nd-Fe-B/Ce-Fe-B
magnets, and provide a certain reference for optimizing the magnetic properties of permanent magnet films in future experiments.
Key wor
Subjects: Materials Science >> Electronic, Optical and Magnetic Materials Subjects: Physics >> Electromagnetism, Optics, Acoustics, Heat Transfer, Classical Mechanics, and Fluid Dynamics submitted time 2022-05-08
Abstract:
In this work, the near ultraviolet femtosecond laser pulse is used to fabricate waveguides and Bragg gratings in poly methyl pentene (PMP). It is observed that the polymer exhibits sensitivity for the light polarization. In low NA processing, by supercontinuum spectrum estimation, the process window of peak power ranges from 2.2MW to 9.2MW. It is inferred that the nonlinear refractive index is n2387=2×10-16cm2W-1 and the third-order susceptibility χ(3) is calculated to be 1.1×10-14esu. Filamenting-process length varies from 300μm to 1500μm along with the increase of pulse energy and the length is a power function of peak energy with power index of ~ 0.53. The maximum of refractive index change is 0.01 which is inferred from the first grating diffraction efficiency, an order higher than the previous figures. These results show that the pulse peak intensity is critical to induce nonlinear absorption in terms of the two-photon absorption. The experimental data provides the latest data for scientific researchers and optical engineers.
Peer Review Status:Awaiting Review
Subjects: Materials Science >> Electronic, Optical and Magnetic Materials submitted time 2022-03-07
Abstract:In this paper, we reported a method to modify the crystallization of CZTSSe films by changing the microstructures of the precursor films. Precursor films with different microstructures were prepared and their crystallization processes were analyzed. We find even tiny differences in microstructures of the precursor films can result in significant alteration of the crystallization processes and the properties of CZTSSe films. Moreover, we found the S-to-Se substitution can be delayed to higher temperature depending on the microstructure of the precursor. This process plays critical roles in enhanceing the crystallization of CZTSSe films and can be used to eliminate the multi-layer crystallization in CZTSSe films. The detailed analysis on the crystallization processes revealed that different mechanism may dominate the crystallization of the films, which can determine the properties of CZTSSe films and solar cells. Moreover, a hybrid structure for precursor film was proposed which has different microstructures in different part of the film. In such a precursor film, different crystallization mechanism can work synergically during the preparation of the film. As the results, the comprehensive properties of the films were improved and solar cells with efficiencies up to 12.6% was prepared.
Peer Review Status:Awaiting Review
Subjects: Materials Science >> Electronic, Optical and Magnetic Materials submitted time 2019-04-30
Abstract: CsKNaLi(Li3SiO4)4:Eu2+ (CKNLLSO:Eu2+) as a new member of oxide-based family with UCr4C4-related type structure was first synthesized successfully. The crystal and band structure of the host compound was characterized and analyzed by aid of Rieveld refinement and density functional theory, respectively. As a result of the highly condensed and rigid anion framework, Eu2+ substituting Cs site gives intense green emission with a narrow full width at half maximum of 55 nm excited by InGaN-based near UV LEDs. The CKNLLSO:Eu2+ phosphor exhibits relatively high thermal stability even though the temperature was raised to 190 ℃. The LED fabricated using the optimized CKNLLSO:4%Eu2+ phosphor demonstrated bight and narrow green light with chromaticity coordinate (0.2320, 0.6016) and correlated color temperature 7314 K, implying its great potential for applications as green components for white LEDs.
Peer Review Status:Awaiting Review
Subjects: Materials Science >> Electronic, Optical and Magnetic Materials submitted time 2017-03-29
Abstract:The phase transformation in two modes, including both displacive and massive growth of τ-phase from ε-MnAl(C), was in situ observed. Temperature dependence of magnetization curves of MnAl(C) under magnetic field were employed for the first time to determine the triggering temperatures of different phase transformation modes. The displacive growth of ε→τ in MnAl(MnAlC) occurs at temperatures below 650 K(766 K), above which both modes coexist. One third or less of the ε-phase can be transformed into τ via displacive mode while the remaining two thirds or more via massive mode. Most large τ-grains formed via massive mode are actually containing a large number of well-distributed τ-nanocrystallline formed via displacive mode. The typical massive growth rate of the τ-phase is 8-60 nm/s, while the displacive growth rate is quite low. The doping of C to MnAl prevents the growth of ε-phase along the basal plane and thus increases the activation temperatures of the phase transformations and the decomposition of τ-phase. Pure τ-phase with highest magnetizations up to 118.3 Am2/kg was obtained. No decomposition was observed in τ-MnAl and τ-MnAl(C) after long-time annealing at selected temperatures, which are crucial in preventing the metastable τ phase from decomposition. These results provide a more complete understanding of the ε→τ phase transformations and thus facilitate the development of high-performance MnAl-based magnets.
Peer Review Status:Awaiting Review