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61.
There are no reports about the electronic transport behavior of the melting metal nanostructures because the morphology of nanostructures cannot be kept under the melting condition. Here, the electronic properties of the melting Bi nanowires are investigated using the pore confinement of anodic aluminum oxide template. The results indicate that with the increase of temperature the resistance of Bi nanowires has a transition from the positive temperature coefficient of resistance before fusion to the negative one after fusion. Moreover, as the temperature gradually increases, the resistance of the melting Bi nanowires rapidly decreases at first, and then tardily decreases. This research provides fundamental and valuable information for exploring and designing the new electronic devices under the high temperature. 相似文献
62.
In the paper mentioned above we reported on the switching mechanism in vanadium dioxide which was shown to be based on the electronically-induced Mott insulator-to-metal transition occurring in conditions of the non-equilibrium carrier density excess in the applied electric field, and the proposed model involved the dependence of the carrier density n on electric field (the Poole–Frenkel effect), as well as the dependence of the critical electric field on n. The data on the n(T) dependence were obtained on the assumption of a temperature-independent carrier mobility μ, and the problem of n reduction at lower temperatures was not fully understood. In this Letter we revisit this problem in the light of some recent data on the μ(T) dependence for VO2. It is shown that the adjusted values of n, taking into account this μ(T), correspond to the Mott critical density within an order of magnitude. 相似文献
63.
The olivine type LiMPO4 (M=Ni, Mn and Co) materials were synthesized by solution combustion technique using glycine as fuel. The structural characterizations were explored to confirm the phase formation of materials. The scanning electron microscope was used to identify the morphology of olivine materials. The local structure and chemical bonding between MO6 octahedral and (PO4)3- tetrahedral groups were probed by Raman spectroscopy. Grain and grain boundaries were contributed for ion relaxation and dc conduction in olivine materials. Two orders of enhancement in ionic conductivity was observed in these olivine materials than the reported value. Among all the explored olivine samples, LiMnPO4 showed highest enhancement in conductivity due to weak Li–O bonding and largest unit cell volume. 相似文献
64.
Conductance histograms of palladium nanocontacts in ultra high vacuum (UHV) were experimentally studied at room temperature using scanning tunneling microscope (STM). Our results show that the resolution of the pure Pd peaks, at 1.8 and around 3G0, in the histograms, depends on the bias voltage and the electrodes size. The size of the electrodes should be as small as possible to achieve the higher extraction of hydrogen from them and therefore preventing the diffusion of H from the bulk to the nanocontacts during the conductance measurements, particularly at low bias voltage. This could explain why peaks have not been observed previously in the Pd histograms, using STM techniques in UHV. 相似文献
65.
Aline Bruna da Silva Juliano Marini Genaro Gelves Uttandaraman Sundararaj Rinaldo Gregório Jr. Rosario E.S. Bretas 《European Polymer Journal》2013
The objective of this work was to prepare novel conductive blends of poly(vinylidene fluoride) (PVDF) with polypyrrole (PPy) and to compare their performance with PVDF/multiwall carbon nanotube (MWCNT) composites and novel PVDF/PPy/MWCNT hybrid systems. All the compositions were prepared by melt mixing using a miniature mixer. The mixtures were characterized by Fourier transformed infrared (FTIR), wide angle X-ray diffraction (WAXD), thermogravimetric analyses (TGA), scanning and transmission electron microscopy (SEM and TEM, respectively) and volume electrical resistivity. For the binary PVDF/PPy and PVDF/MWCNT systems, percolation thresholds of 10 and 0.3 wt%, respectively, were found. In the hybrid systems, however, the percolation threshold for each filler was lower than in the binary systems, but the electrical conductivities were always much higher at all concentrations than the conductivities of the binary systems. Therefore, the addition of both fillers had a synergistic effect on the hybrid system conductivity, which was attributed to its morphology: the PPy increased the homogeneity of the MWCNT distribution and decreased the available free volume for the MWCNT; as a result the MWCNT rolled around the PPy particles bridging them through the PVDF matrix, increasing the quantum tunneling effect and thus, the electrical conductivity of the system. 相似文献
66.
Pattana Kueseng Pongdhorn Sae-oui Chakrit Sirisinha Karl I. Jacob Nittaya Rattanasom 《Polymer Testing》2013
50/50 NR/NBR blends with various MWCNT loadings were prepared by mixing with MWCNT/NR masterbatches on a two-roll mill and sheeted off at the smallest nip gap. Then, the effect of milling direction, machine direction (MD) and transverse direction (TD), on the mechanical and electrical properties of the blends was elucidated. Dichroic ratio and SEM results confirmed that most of the MWCNTs were aligned along MD when MWCNT was less than 4 phr, and the number of agglomerates increased when MWCNT was more than 4 phr. Additionally, anisotropic properties were clearly observed when 4 phr MWCNT was loaded. At 4 phr MWCNT, 100% modulus and tensile strength in the MD were about 1.5 and 1.3 times higher than those in the TD, respectively. Moreover, electrical conductivity in the MD was superior to that in the TD by about 3 orders of magnitude. Results from dynamic mechanical tests also showed that the maximum tan δ in the MD sample was lower than that in the corresponding TD sample. In addition, the storage modulus at 30 °C for the MD sample containing 4 phr MWCNT was 1.15 higher than that of the corresponding TD sample. This stronger reinforcement efficiency resulted from the combination of the greater alignment and dispersion of most MWCNTs in the MD sample. 相似文献
67.
Johnny N. Martins Michaela Kersch Volker Altstädt Ricardo V.B. Oliveira 《Polymer Testing》2013,32(5):862-869
Blends of poly(vinylidene fluoride) (PVDF) and polyaniline (PAni) were prepared through melt blending in a batch mixer. The morphology, rheological behavior and electrical conductivity were investigated through transmission electron microscopy (TEM) and combined electro-rheological measurements. Through TEM analysis, it was possible to observe that all blends showed typical phase separation with the presence of conductive polymer aggregates. Deformations imposed during a strain sweep caused, not only disturbance of the linear viscoelastic behavior, but also changes in electrical conductivity. The oscillatory shear altered the morphology, breaking the PAni domains into smaller ones. This effect increases the distance between them and, consequently, resulted in a decrease of the electrical conductivity. The measurements under quiescent conditions and steady shear proved that the disturbance in morphology for PVDF/PAni system is non-recoverable. Through combined electrical and rheological measurements, it was possible to achieve good correlation between the electrical and flow behavior of PVDF/PAni blends. 相似文献
68.
69.
Fang Wang Zhiqing Zhang Saiyu Zhang 《Journal of Dispersion Science and Technology》2013,34(8):1166-1172
A study was carried out on the mechanism of electrical conductivity percolation of H2O/C16EO20/n-butanol/heptane microemulsions. Electrical conductivity, UV-vis spectroscopy and FTIR spectra were used to study the diluted “dry” microemulsions with the mass ratio of C16EO20/n-butanol/heptane = 3:3:4. The results of electrical conductivity showed that the percolation occurred around φw = 20 wt% and the transition of w/o microemulsions to bicontinueous microemulsions happened when φw = 45 wt%. From the UV-vis absorption spectra, it was found that the absorption of methyl orange (MO) in microemulsions shifted red than that of in oil phase, but the maximal absorption peak (λmax) remained unchanged when φw > 20 wt%. It implied that the position of MO solubilized in microemulsions was unvaried after free water appeared in the core. FTIR spectra revealed that the OH band of water in microemulsions moved to high frequency at low φw (< 20 wt%) and became broader at high φw. It indicated that the added water only caused the hydration of EO at low φw, the hydration completed when φw > 20 wt% and then the residual water entered into the core with properties similar to bulk water. The presence of free water as ions exchange medium will cause the electrical conductance increased. The percolation appeared after the hydration of EO completed. 相似文献
70.
This article elucidates the pitfalls identified in the software package SIMPRE recently developed by Baldoví et al. (J. Comput. Chem. 2013, 34, 1961) for modeling the spectroscopic and magnetic properties of single ion magnets as well as single‐molecule magnets. Analysis of the methodology used therein reveals that the crystal field parameters (CFPs), expressed nominally in the Stevens formalism, exhibit features characteristic for the CFPs expressed in the Wybourne notation. The resemblance of the two types of CFPs introduces a serious confusion that may lead to wrong comparisons of the CFPs taken from various sources. To clarify this confusion, the properties of the CFPs ( , ) associated with the Stevens operators ( X = S , J , or L ), which belong to the class of the tesseral‐tensor operators, are contrasted with those of the CFPs Bkq associated with the Wybourne operators , which belong to the class of the spherical‐tensor operators. Importantly, the confused properties of Stevens and Wybourne operators may bear on reliability of SIMPRE calculations. To consider this question independent calculations are carried out using the complete approach and compared with those of the restricted approach utilized earlier. It appears that the numerical results of the package SIMPRE are formally acceptable, however, the meaning of the CFPs must be properly reformulated. Several other conceptual problems arising from misinterpretations of the crucial notions and the CFP notations identified therein are also discussed and clarified. © 2014 Wiley Periodicals, Inc. 相似文献