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排序方式: 共有124条查询结果,搜索用时 31 毫秒
1.
Sruthi Guru Shubham Kumar Sankeerthana Bellamkonda Ranga Rao Gangavarapu 《International Journal of Hydrogen Energy》2021,46(30):16414-16430
A nanocomposite CuTi layered double hydroxide (LDH) supported on g-C3N4 (15 wt% of g-C3N4) is facilely synthesized by hydrothermal method. There are electrostatic interactions between positive layers of CuTi-LDH and negatively charged inner g-C3N4 sheets. The nanocomposite and its precursors are characterized through various analytical techniques, which affirmed the presence of both g-C3N4 and CuTi-LDH characteristic features. The pore-enriched hybrid geometry of CuTi-LDH@g-C3N4 with high specific surface area (146 m2/g), and suitable band gap of 2.46 eV enables the nanocomposite to act as both an electrocatalyst and photoelectrocatalyst for oxygen evolution reaction (OER). Both the electrochemical and photoelectrochemical studies are done using 1 M KOH (pH = 13.6) with applied potential of ?0.2 V to 1.5 V vs. Ag/AgCl. The onset potential of CuTi-LDH@g-C3N4 for OER appears at η = 0.36 V in dark and η = 0.32 V under visible light illumination of 30 min. Also, Mott-Schottky analysis shows n-type semiconductor behaviour for CuTi-LDH@g-C3N4 and its precursors. The photoelectrochemical water oxidation proceeds by charge transfer across a Type II heterojunction formed between the CuTi-LDH and g-C3N4 materials. 相似文献
2.
In the present study, we report the synthesis of photoactive bismuth oxycarbonate (BOC, Bi2O2CO3) grafted NiFe layered double hydroxide (LDH) supported on g-C3N4 (15 wt% of g-C3N4) by coprecipitation method. The band gap of this photoactive material is determined to be 1.7 eV. The Bi2O2CO3 agglomerates are anchored on NiFe-LDH plates and g-C3N4 nanosheets intercalated between the LDH plates. This architecture helps in expediting electron transfer for hydrogen and oxygen evolution reactions. The pristine NiFe-LDH photoanode acquires bifunctional character because of Bi2O2CO3 agglomerates and g-C3N4 embedded in the architecture of BOC/NiFe-LDH@g-C3N4. This is found to be an efficient photoanode for oxygen evolution and photocathode for hydrogen evolution reactions. The water splitting process occurs along the heterojunction formed between g-C3N4 nanosheets and Bi2O2CO3 grafted NiFe-LDH. Further, an additional interfacial charge transfer aided by Bi2O2CO3 results in S-scheme mechanism, which enhances the rate of photoelectrochemical hydrogen and oxygen evolution reactions. 相似文献
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Lead zirconate titanate thick film with molecular formula PbZr0.52Ti0.42O3 (PZT) was prepared by a modified conventional sol–gel method through seeding and high-energy ball milling, resulting in perovskite phase formation at lower temperatures. The ball-milling time was optimized by keeping the seed particle loading (5 wt.%) constant in the sol–gel solution. This methodology helped in reduction of the crystalline phase formation temperature to 300°C, which is much lower than that reported in the literature (450°C). The well-established perovskite phase was confirmed by x-ray diffraction (XRD) analysis. Scanning electron microscopy (SEM) of PZT films revealed uniform and crystalline microstructure. Film prepared by this methodology showed higher spontaneous polarization (2.22 μC/cm2), higher capacitance (1.17 nF), and low leakage current density (18 μA/cm2). The results obtained from ferroelectric characterization showed a strong correlation with the XRD and SEM results. 相似文献
5.
Robert Brüll Guru Geertz Hans Kothe Tibor Macko Michael Rudschuck Mirko Wenzel Kurt Engelsing Jürgen Wüst Martin Bastian 《大分子材料与工程》2008,293(5):400-408
The supramolecular structure in pipe walls of isotactic PP‐R is a function of compound composition and processing parameters, which both influence the mechanical properties of the pipes. µFTIR shows a gradient of the crystallinity across the pipe wall, with a lower‐crystalline outer layer, and a higher‐crystalline core layer. The rate of extrusion has an influence on the thickness of the outer layer. The nucleating effect on the morphological profile throughout the pipe wall can be visualised. µFTIR shows a homogeneous distribution of the primary antioxidant in the pipe wall. Both the spectral crystallinity and the antioxidant concentration distribution are calculated.
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Abstract One of the critical design aspects in ferroelectric tunable microstrip filters is choosing the right bias configuration, for large tunability as well as to maintain the filter's passband characteristics. This work is based on strontium titanate (STO) ferroelectric thin-film based tunable microstrip filters for cryogenic temperature applications. Large tunability factors have been demonstrated in YBCO/STO/LAO two-layered microstrip filters when operated at or below 77 K. The effect of the dc electric field (primarily responsible for tuning) and critical design parameters such as the insertion loss, frequency tunability, return loss, and bandwidth of superconductor/ferroelectric/dielectric microstrip tunable K-band microwave filters is discussed in this work. 相似文献
8.
Felix A. Miranda Carl H. Mueller Fred W. Van Keuls Guru Subramanyam Sivaruban Vignesparamoorthy 《Integrated ferroelectrics》2013,141(1):121-131
The inclusion of voltage-tunable barium strontium titanate (BSTO) thin films into planar band pass filters offers tremendous potential to increase their versatility. The ability to tune the passband so as to correct for minor deviations in manufacturing tolerances, or to completely reconfigure the operating frequencies of a microwave communication system, are highly sought-after goals. However, use of ferroelectric films in these devices results in higher dielectric losses, which in turn increase the insertion loss and decrease the quality factors of the filters. This study explores the use of patterned ferroelectric layers to minimize dielectric losses without degrading tunability. Patterning the ferroelectric layers enables us to constrict the width of the ferroelectric layers between the coupled microstrip lines, and minimize losses due to ferroelectric layers. Coupled one-pole microstrip bandpass filters with fundamental resonaces at ~7.2 GHz and well-defined harmonic resonances at ~14.4 and ~21.6 GHz, were designed, simulated and tested. For one of the filters, experimental results verified that its center frequency was tunable by 528 MHz at a center frequency of 21.957 GHz, with insertion losses varying from 4.3 to 2.5 dB, at 0 and 3.5 V/ w m, respectively. These data demonstrate that the tuning-to-loss figure of merit of tunable microstrip filters can be greatly improved using patterned ferroelectric thin films as the tuning element, and tuning can be controlled by engineering the ferroelectric constriction in the coupled sections. 相似文献
9.
The sensitivity penalty is evaluated for amplitude-shift-keyed and frequency-shift-keyed multichannel coherent systems that use lasers with linewidths which are a significant fraction of the bit rate. The study was conducted for both ASK and FSK systems using a single-filter receiver with nonsynchronous detection. For FSK systems, both NRZ (nonreturn-to-zero) and alternate mark inversion (AMI) signal formats were studied. The optical channel spacing is strongly determined by the laser linewidth. For example, with the FSK-NRZ data rate of 150 Mb/s, the optical channel spacing which gives 1-dB crosstalk penalty is 4 GHz when the intermediate frequency linewidth is 50 MHz (laser linewidth is 25 MHz), as opposed to 1.8 GHz when the linewidth is negligible.<> 相似文献
10.
K Sooryanarayana T N Guru Row R Somashekar K B R Varma 《Bulletin of Materials Science》1998,21(6):499-502
X-ray line broadening is found to be an effective parameter to estimate the strain associated with rare earth ion (Gd3+)-doped polycrystalline bismuth vanadate(Bi2VO5·5). The strain increases with increasing Gd3+ concentration. It is anisotropic and found to be maximum in (111) plane. The Curie temperature which is known to decrease
with increase in the rare earth ion concentration in these compounds is correlated with increase in strain. 相似文献