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Synthesis and characterization of (1??? <i>x</i> )(La <sub/>0.6</sub> Ca <sub/>0.4</sub> MnO <sub/>3</sub> )/ <i>x</i> (Sb <sub/>2</sub> O <sub/>3</sub> ) ceramic composites
摘要： The composites ((1 ? x)(La0.6Ca0.4MnO3)/x(Sb2O3)) (x = 0.00, 0.07 and 0.12) were synthesized by conventional solid-state reaction method. The results of X-ray di?raction (XRD) and SEM indicate that Sb2O3 and LCMO coexist in the composites and Sb2O3 mainly segregates at the grain boundaries of LCMO. Furthermore, the magnetic study shows a typical variation. The resistivity of the composite samples was measured at the applied magnetic ?elds of 0T, 2T and 5T. All the specimens undergo a metallic–semiconductor transition at the temperature Tρ. The temperature dependence of resistivity shows that the transport behavior of the composites is governed by the grain boundaries. It is suggested that the Sb2O3 addition, acts as a separation layer between grains. The ρ-T ?t well with the phenomenological equation for conductivity under a percolation approach. Magnetoresistance (MR) has been found to reach a maximum value with Sb2O3 addition. The magnetocaloric properties of LCMO based on resistivity measurements were investigated. We measure the magnetic entropy change ΔSM from the resistivity which is similar to that calculated from the magnetic measurements. Finally, the TCR curves show good value under zero magnetic ?eld, which makes it a good candidate for bolometer applications.
关键词： MR,Manganite-composite,percolation model,resistivity,TCR
更新于2025-09-10 09:29:36
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Single fibres of pyro-electrospinned PVDF-HFP/MWCNT unveal high electrical conductivity
摘要： Formation of single fibres of polymer nanocomposite PVDF-HFP containing MWCNT by Pyro-EHD electrospinning is reported for the first time. Pyro-EHD gives the chance to drawing fibres directly from a viscous polymeric solution containing MWCNT, with respect to classical electrospinning in which highly viscous materials have strong limitation due to the clogging effect. This method allows achieving an electrical conductivity of the fibres considerably higher with respect to the bulk state. The improvement of the electrical conductivity is of one order of magnitude and the electrical percolation threshold is reduced from 2.5 to 0.3 wt%. We also show that the MWCNT are highly oriented in the longitudinal direction of the fibres, producing the improvement in the electrical properties of the composite.
关键词： carbon nanotubes,electrical percolation,PVDF-HFP
更新于2025-09-10 09:29:36
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Multiphonon trap ionization transport in nonstoichiometric SiN<i><sub>x</sub></i>
摘要： It is generally accepted that the charge transport in dielectrics is governed by coulombic trap ionization due to a barrier lowering in high electric fields (Frenkel effect). In this paper, the charge transport mechanism in Si3N4 and nonstoichiometric silicon rich SiNx is experimentally studied and quantitatively analyzed with five theoretical models: Frenkel model of Coulomb traps ionization, Hill-Adachi model of overlapping Coulomb traps, Shklovskii-Efros percolation model, Makram-Ebeid and Lannoo model of multiphonon isolated traps ionization and Nasyrov-Gritsenko model of phonon-assisted electron tunneling between nearby traps. It is shown that the charge transport in Si3N4 and SiNx is qualitatively described by Frenkel effect, but Frenkel effect predicts an enormously low attempt to escape factor value. The charge transport at traps energies Wt=1.6 eV and Wopt=3.2 eV in Si3N4 and SiNx can be described by an increase in traps concentration in the framework of Makram-Ebeid and Lannoo model and Nasyrov-Gritsenko model. The Makram-Ebeid and Lannoo model quantitatively describes the charge transport in Si3N4 and SiNx with low silicon enrichment. The charge transport in nonstoichiometric SiNx with high silicon enrichment is well explained by Nasyrov-Gritsenko model.
关键词： charge transport,traps ionization,percolation,traps
更新于2025-09-09 09:28:46
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High-performance stretchable conductive nanocomposites: materials, processes, and device applications
摘要： Highly conductive and intrinsically stretchable electrodes are vital components of soft electronics such as stretchable transistors and circuits, sensors and actuators, light-emitting diode arrays, and energy harvesting devices. Many kinds of conducting nanomaterials with outstanding electrical and mechanical properties have been integrated with elastomers to produce stretchable conductive nanocomposites. Understanding the characteristics of these nanocomposites and assessing the feasibility of their fabrication are therefore critical for the development of high-performance stretchable conductors and electronic devices. We herein summarise the recent advances in stretchable conductors based on the percolation networks of nanoscale conductive fillers in elastomeric media. After discussing the material-, dimension-, and size-dependent properties of conductive fillers and their implications, we highlight various techniques that are used to reduce the contact resistance between the conductive filler materials. Furthermore, we categorize elastomer matrices with different stretchabilities and mechanical properties based on their polymeric chain structures. Then, we discuss the fabrication techniques of stretchable conductive nanocomposites toward their use in soft electronics. Finally, we provide representative examples of stretchable device applications and conclude the review with a brief outlook for future research.
关键词： soft electronics,conductive nanocomposites,stretchable conductors,percolation networks,elastomeric media
更新于2025-09-04 15:30:14