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41.
42.
NiNdxFe2-xO4 nanoferrites with different compositions of x?=?0.01, 0.03, 0.05, 0.07 and 0.09 were prepared using the sonochemical method. The structural, optical and morphological properties of the prepared nanoferrites were characterized by X-ray diffraction, ultra violet-diffuse reflectance spectroscopy, scanning electron microscopy and X-ray fluorescence techniques. The X-ray diffraction analysis of the prepared nanoferrites confirmed the presence of a cubic spinel structure. The average crystallite sizes of the prepared nanoferrites were 52, 49, 46, 44 and 40?nm for x?=?0.01, 0.03, 0.05, 0.07 and 0.09, respectively. The particle size of the prepared NiNdxFe2-xO4 nanoferrites was in the range 60–40?nm. The dielectric parameters ranged from 2.9?GHz to 5.6?GHz. Decrease in the dielectric constant was observed with an increase in Nd3+ ions in the prepared NiNdxFe2-xO4 nanoferrites. However, a reverse trend was observed in the dielectric loss. An impedance analysis of the prepared nanoferrites was carried out to explore the pseudo-capacitance behavior. The saturation magnetization and remnant magnetization values of the prepared nanoferrites decreased with an increase in the concentration of Nd3+ ions in NiNdxFe2-xO4 nanoferrites. 相似文献
43.
Yue Wang Jingyi Qiu Zhongbao Yu Hai Ming Meng Li Songtong Zhang Yusheng Yang 《Ceramics International》2018,44(2):1312-1320
Surface-interface reaction between the electrode and electrolyte plays a key role in lithium-ion storage properties, especially for high voltage cathode such as LiCoPO4 and Ni-riched cathode. Generally, surface modification is an effective method to improve the electrochemical performance of electrode materials. Herein, in order to revise the LiCoPO4 cathode with desirable properties, uniform AlF3-modified LiCoPO4 (LiCoPO4@AlF3) cathode materials in nano-sized distribution are synthesized. XRD result indicates that there is no structural transformation observed after AlF3 coating. TEM characterization and XPS analysis reveal that the surface of LiCoPO4 particle is coated by a nano-sized uniform AlF3 layer. Further, the electrochemical results indicate that AlF3 layer significantly improves the cycling and rate performances of LiCoPO4 cathode within the voltage range of 3.0–5.0 V. After a series of optimization, 4 mol% AlF3-coated LiCoPO4 material exhibits the best properties including an initial discharge capacity of 159 mA h g?1 at 0.1 C with 91% capacity retention after 50 cycles, especially a discharge capacity of 90 mA h g?1 can be obtained at 1 C rate. CV curves indicate that the polarization of cathode is reduced by AlF3 layer and EIS curves reveal that AlF3 layer relieves the increase of resistance to facilitate Li-ion transfer at the interface between electrode and electrolyte during the cycling process. The enhanced electrochemical performances are attributed to that the AlF3 layer can stabilize the interface between the cathode and electrolyte, form steady SEI film and suppress the electrolyte continuous decomposition at 5 V high voltages. This feasible strategy and novel characteristics of LiCoPO4@AlF3 could promise the prospective applications in the stat-art of special lithium-ion battery with high energy and/or power density. 相似文献
44.
《Ceramics International》2020,46(14):22738-22744
(1-x) K0.5Na0.5NbO3 ~ xAl2O3 (x = 0, 0.2, 0.4, 0.6) ceramics were prepared via a traditional solid-state reaction method. The phase structure, micro-morphology, dielectric properties and electromagnetic properties of ceramic samples were studied and analyzed. Results indicate that all the samples are similar to K0.5Na0.5NbO3 (KNN) in perovskite structure. With the increase of Al2O3 content, the X-ray diffraction peaks move to a large angle region, suggesting the substitution of niobium ions by aluminium ions and the distortion of the KNN lattice with a new phase arising. With the increase of Al2O3 content the grain size reduces and the dielectric constant decrease, yielding to the decrease of the electromagnetic shielding performance of ceramic. When the x is 0.4, the minimum value of reflectivity of sample is −28 dB at the frequency of 11.6 GHz. It can be concluded that both the grain size and Al2O3 content can obviously affect the electromagnetic properties of ceramics, which can be easily turned through a multi-layer SiO2 heterojunction structure. 相似文献
45.
《Ceramics International》2020,46(3):2868-2876
In order to improve the stability of PZT-based sensors, the mechanical, dielectric, ferroelectric and piezoelectric properties of PZT-5H under impact load were studied experimentally by using the separated Hopkinson pressure bar (SHPB) with an electrical output measurement device. At the same time, the experimental study on the material properties of PZT-5H before and after the impact was carried out. The effect of impact cracks on the output voltage of PZT-5H was also analyzed. The results show that the dynamic piezoelectric constants of PZT-5H under low stress impact (10–50 MPa) are different from those under quasi-static state, and the empirical relationship between them and the peak stress is obtained through experiments. The dielectric properties of PZT-5H did not change under low stress impact, but micro-cracks occurred in the material and dielectric loss increased at high frequencies. Under short circuit, the residual polarization intensity of PZT-5H decreases sharply due to impact load. While the impact load causes the secondary polarization and the increase of the residual polarization intensity of PZT under open circuit. When the stress is over 45 MPa, the PZT-5H breaks. The formation of cracks causes abnormal discharge voltage and gap discharge. 相似文献
46.
《Ceramics International》2020,46(13):20798-20809
The yttrium substituted cadmium ferrites having composition Cd1-xYxFe2O4 (X = 0.00, 0.125, 0.250, 0.375, 0.500) were synthesized by the co-precipitation method and sintered at 1100 °C for 6 h. Structural, morphological, electrical, optical and dielectric characteristics were explored by XRD, SEM, EDS, FTIR, I–V two probes, UV–Vis and LCR techniques.XRD results confirmed the cubic structure of spinel ferrites. A decrease in lattice constants of the prepared samples was observed with the substitution of Y ions and was attributed to the difference in ionic radii of Y3+ (0.95 Å) and Cd2+ (0.97 Å) ions. Cationic distributions, ionic radii of both tetrahedral and octahedral sites, tolerance factor, oxygen positional parameters, bond lengths, interatomic distances, positional parameters and bond length angles were calculated from XRD data. The morphology of the prepared ferrites was studied using SEM and results ratified the XRD results. EDS confirmed the presence of all inserted elements in Cd1-xYxFe2O4 composition. DC resistivity and drift mobility of soft-ferrites were found to be increased from 1.047 × 108–4.822 × 1010 Ω-cm and 5.87 × 10−12 – 1.045 × 10−14 cm2V−1s−1, respectively, at 523 K with yttrium content confirming the behavior of semiconductor materials. The optical band gap energy calculated from the UV–Vis pattern of the Cd1-xYxFe2O4 system was decreased from 3.6011 to 2.8153 eV. DC resistivity and optical band gaps exposed inverse relation. FTIR results revealed lower and upper-frequency absorption bands in the ranges of 419.31–417.01 cm−1 and 540.95–565.70 cm−1, respectively. Dielectric constant and dielectric losses were in decreasing order, while ac conductivity revealed rising behavior with increasing frequency. Results showed the potential of yttrium doped Cd nanoferrites for applications in high-frequency microwave absorbing devices. 相似文献
47.
ABSTRACTThe novel model of the coupled beam-type electrodes with elastic roots, subjected to the AC and DC voltages is constructed. The exact critical pull-in voltage of the two coupled elastically restrained beams with size effect is presented. The analytical method of the general system subjected to the AC and DC voltages simultaneously is presented. The characteristic mechanism of coupled vibration is investigated. 相似文献
48.
Material functionalization of triboelectric nanogenerators (TENG) plays an important role in TENG's electric performance for sustainable energy harvesting. In this work, a method for improving polydimethylsiloxane (PDMS) composites triboelectric performance has been proposed, via filling high dielectric constant liquid (instead of solids) into PDMS matrix. The improvement is attributed to the high dielectric constant liquid in PDMS matrix that reduced the effective thickness of PDMS and increased the dielectric constant of PDMS composite synchronously. At 50% filling ratio (PDMS‐HD50), the triboelectric performance exhibits an enhancement of 4.5‐fold in output voltage and 3.9‐fold in output current as compared to pure PDMS. The results, besides higher transparency, are superior to the results from traditional solid dielectric constant doping materials like BaTiO3 nanoparticle in PDMS. This work has proved potentials of dielectric liquid filling materials in fabricating TENGs and could be a guidance for exploring new liquid filling materials. 相似文献
49.
Hajime Tomita 《Electrical Engineering in Japan》2015,190(3):1-8
In this investigation, the nature of the electrostatic discharge (ESD) that occurs when a charged object moves toward a stationary grounded object is experimentally clarified. The spark lengths, discharge currents, and induced voltages in a magnetic probe were measured when a charged metallic spherical electrode connected to a 422 pF capacitor approached a stationary grounded object, which was the current target, for different moving speeds of the charged metallic spherical electrode in a range of 1 mm/s to 100 mm/s. The charge voltages of the capacitor were +6.5 kV and +10 kV. Based on the results, the average gap length shortened with the speed of the spherical electrode. The average peak values of the discharge current and the induced voltage were likely to increase with the speed of the spherical electrode. The average rise times of the discharge current and the induced voltage were likely to drop with the speed of the spherical electrode. The relation between the spark length and the discharge current due to the ESD can be explained qualitatively by using an equation derived from the spark resistance formula proposed by Rompe and Weizel. 相似文献
50.