Search

Ceramic-based capacitors with excellent recoverable energy storage density (Wrec) and efficiency (η) are greatly desired for pulsed capacitors but challenge as well. In this work, the high energy storage performance with an Wrec of 5.1 J/cm3, an η of 93.4%, and an ultrafast discharge–charge speed t0.9 of 72 ns is achieved in unusual interstitial and substitutional hybrid solid solution of Sr0.64Bi0.18Na0.18TiO3-ZnO (SBNT-Zn), in which two Zn2+ ions occupy one A-site, while one Zn2+ ion occupies one B-site of ABO3 perovskite lattice simultaneously. The addition of Zn2+ increases lattice distortion and breaks long-range ferroelectric order, resulting in more highly dynamic polar nanoregions, higher relaxation behaviors as well as larger polarization (ΔP). Moreover, the extraordinary hybrid solid solution configuration enhances the bandgap of SBNT-Zn and ZnO as a sintering aid refines grain size, both help to enhance electric breakdown strength. This work affirms the feasibility and reliability of forming a hybrid solid solution to develop high-performance ferroelectric materials. [ABSTRACT FROM AUTHOR]

Stimulated Brillouin scattering (SBS) in a high-Q resonator is capable for narrow-linewidth laser generation for various applications but is limited by on-resonance pump to SBS matching from single-longitudinal lasing. In this Letter, we present a narrow linewidth laser via SBS that is enhanced in a monolithic high-Q fiber resonator. The unique cross-polarization pump scheme based on fiber birefringence prevents high-order SBS and ensures single-frequency Brillouin lasing with high intracavity conversion efficiency. Fundamental linewidth of 50 Hz is achieved. Moreover, our scheme also allows precise characterization of Brillouin frequency shift and gain bandwidth of some nonlinear materials. [ABSTRACT FROM AUTHOR]

Observations of lamellar like fringes in iron-carbon-filled vertically aligned carbon nanotubes (CNTs) produced by pyrolysis of ferrocene and rapid cooling methodologies (controlled quenching) have been investigated. The quantitative phase analysis of encapsulated Fe3C, γ-Fe, and α-Fe by X-ray diffraction reveals that controlling the phase-percentage leads to control of the crystal habit and of magnetic properties. Large coercivities and variable saturation magnetizations were observed. In addition, we reported a thorough study of the hysteresis behavior, the Barkhausen effect which has to be possibly associated with the formation of interfacial-defects in the crystal areas in contact with CNT layers. [ABSTRACT FROM AUTHOR]

Flexible organic light-emitting diode display devices fabricated on polyimide (PI) substrates have more obvious residual image problems due to the abnormal threshold-voltage (Vth) shifts of a thin film transistor (TFT). In this paper, the Vth shift of TFT fabricated on a PI substrate was analyzed. We explained the worse bias stability and worse recovery of TFT with a PI substrate compared with TFT with a glass substrate, by an interlayer charging effect (Maxwell–Wagner effect) and a technology computer-aided design (Silvaco). When bias stress was applied for a long time, the interface between the PI substrate and the buffer layer will have a charging effect under the action of an electric field, and the charging charge will react on the channel and hinder the formation of the channel. We found that there are differences in the scale of charge under different voltage stress conditions, and this will result in different Vth shifts of driving TFTs for displays units. [ABSTRACT FROM AUTHOR]

A correction to the article "The size-dependent elastic properties of nanofilm with surface effects," presented in the December 15, 2006 issue is presented.

A compact helicon plasma source for the study of helicon plasma, especially for the study of blue core plasma, is designed and developed with permanent magnets (PMs). The structure of the PMs consists of two sets of ring array magnets with opposite magnetization. This structure can provide a higher magnetic field with fewer PMs, which is helpful for controlling the device's mass. A quartz tube with 50 cm in length, 5 cm in outer diameter, and 0.3 cm in thickness is used. Argon helicon plasma is produced at ∼38 sccm (3.4 Pa inlet chamber and 0.122 Pa diffusion chamber) by a radio frequency (RF) power of ∼13.56 MHz using a helical antenna under a high magnetic field (∼1600 G). Preliminary results measured by the Langmuir probe, photomultiplier tube (PMT), CCD, and Hall coil are applied to characterize the helicon plasma in this source, such as the mode transition and the formation of the blue core with the RF power variation. The device generates the blue core (W mode) plasma at a lower power of about 200 W, and the energy coupling efficiency is as high as 65%. [ABSTRACT FROM AUTHOR]

Condensation is of great interest in various heat exchange processes, owing to the elevated heat and mass transfer by phase change. In this work, a hierarchically microgrooved superhydrophobic surface was fabricated by the mechanical broaching and chemical etching methods to enhance the condensation heat transfer. The dynamic behaviors of condensed droplets and condensation heat transfer characteristics were analyzed on such surface. Particularly, there were two droplet jumping modes, the conventional coalescence jumping of small droplets (<100 μm) at small subcooling (ΔT < 5 K) and the forced jumping of large stretched droplets (400–500 μm) in microgrooves at a broad range of subcooling (ΔT < 12 K), simultaneously emerging on the hierarchically microgrooved superhydrophobic surface. The interesting coalescence-induced sweeping behavior independent of gravity is observed at large surface subcooling. The coalescence-induced jumping and sweeping significantly facilitated the renewal of surface. The investigation has showed that a 90% higher heat flux at small subcooling (ΔT < 5 K) and a 66% higher heat flux at large subcooling (5 K < ΔT < 24 K) were reached on the hierarchically microgrooved superhydrophobic surface compared with the plain hydrophobic surface. [ABSTRACT FROM AUTHOR]

A three-terminal bistable twisted nematic liquid crystal display has been demonstrated. This display makes use of a combination of strong in-plane electric fields and vertical electric field for switching between the φ and the φ+π twist states. The lifetimes of the two bistable twist states are infinite, which is a significant improvement over conventional bistable twisted nematic displays. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The growth control of α-Fe inside multiwall carbon nanotubes has challenged researchers for more than a decade owing to the coexistence of this phase with Fe3C and γ-Fe. Previously, long heating treatments of 20 h have been used to decompose the encapsulated Fe-phases in C and Fe; however, these methods were limited by an unusual oxidation process leading to nanotube decomposition. In this letter, we report an alternative chemical vapour deposition approach that through an accurate control of the ferrocene-vapour flow-rate allows to achieve the direct encapsulation of 95% of α-Fe without additional heating treatments. [ABSTRACT FROM AUTHOR]

The electret ultra-fine fiber filter material is prepared by the centrifugal airflow-assisted process. Moreover, the material can be used in the field of air filtration. A longitudinal air pressure draft sprinkler and a refined centrifugal spinning jet were designed to improve the fiber quality. According to different process parameters, in order to optimize the process of preparing ultra-fine fiber by centrifugal spinning, including the mass fraction of SiO2 (0%, 0.5%, 1%, and 1.5%), the effect of draft pressure (0, 0.05, and 0.15 MPa) on the diameter and morphology of the fiber was investigated. In addition, the effect of air pressure on the diameter and morphology of the fiber was investigated. The effects of key process parameters within the range of common production parameters on fiber quality and fiber morphology were expounded. For the prepared fiber felt, a preliminary test of the physical properties related to the molecular structure and filtration performance of the material was carried out, including the FTIR test and surface contact angle test of the material. After that, we carried out electret treatment of the ultra-fine fiber felt prepared by the centrifugal airflow-assisted process. Besides, we compared the surface electric potential and stability of the fiber felt by the needle electret process and wire electret process, respectively. Finally, the key physical properties of the filter media were tested. In addition, the filtration efficiency and resistance indices of the fiber felt prepared with different parameters were compared. Moreover, the effects of fiber morphology and the electret process on the performance of the filter felt were obtained. The study can provide new ideas and references for the preparation of electret ultra-fine fiber filter media. [ABSTRACT FROM AUTHOR]

Lead-free (Bi0.5Na0.5)0.93Ba0.07TiO3–x wt %In2O3 ceramics synthesized by direct reaction sintering have been studied. X-ray diffraction reveals that all (Bi0.5Na0.5)0.93Ba0.07TiO3–x wt %In2O3 ceramics are of a perovskite structure with coexistence of rhombohedral and tetragonal phases. It is found that the direct reaction sintering promotes growing of ceramic grains while doping of In2O3 contributes to inhibit and homogenize the grain growth, as shown by scanning electron microscopy. The ceramics show excellent piezoelectric and dielectric properties with thickness electromechanical coupling factor kt=0.503, piezoelectric constant d33=205 pC/N, dielectric constant [variant_greek_epsilon]33T/[variant_greek_epsilon]0=1046, and loss tangent tan δ=0.036. [ABSTRACT FROM AUTHOR]