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81.
In this work, we report the effect of substrate, film thickness and sputter pressure on the phase transformation and electrical resistivity in tantalum (Ta) films. The films were grown on Si(1 0 0) substrates with native oxides in place and glass substrates by varying the film thickness (t) and pressure of the working gas (pAr). X-ray diffraction (XRD) analysis showed that the formation of α and β phases in Ta films strongly depend on the choice of substrate, film thickness t and sputter pressure pAr. A stable α-phase was observed on Si(1 0 0) substrates for t ≤ 200 nm. Both α and β phases were found to grow on glass substrates at all thicknesses except t = 100 nm. All the films grown on Si(1 0 0) substrates for pAr ≤ 6.5 mTorr had α-phase with strong (1 1 0) texture normal to the film plane. The glass substrates promoted the formation of β-phase in all pAr except pAr = 5.5 mTorr. The resistivity ρ was observed to decrease with t, whereas ρ was increased with pAr on Si(1 0 0) substrates. In all films, the measured resistivity ρ was greater than the bulk resistivity. The resistivity ρ was influenced by the effects of surface roughness and grain size. 相似文献
82.
《Mathematical Methods in the Applied Sciences》2018,41(8):3062-3092
In this paper, we consider an initial boundary value problem for the 3‐dimensional nonhomogeneous incompressible magnetohydrodynamic equations with density‐dependent viscosity and resistivity coefficients over a bounded smooth domain. Global in time unique strong solution is proved to exist when the L2 norms of initial vorticity and current density are both suitably small with arbitrary large initial density, and the vacuum of initial density is also allowed. Finally, we revisit the Navier‐Stokes model without electromagnetic effect. We find that this initial boundary problem also admits a unique global strong solution under other conditions. In particular, we prove small kinetic‐energy strong solution exists globally in time, which extends the recent result of Huang and Wang. 相似文献
83.
Zhimin Xie Young‐Jin Yum Chul‐Kyoung Lee 《Journal of Macromolecular Science: Physics》2013,52(3):561-567
It has been known that the carbon black (CB) network is responsible for the electrical and mechanical behaviors of filled rubber. Due to the complexity involved in the filled rubber in relation to the conductive mechanism of the CB network, there has been little work concerned with simulation of the electrical behavior at large strains. Based upon an infinite circuit model, the electrical resistivity of CB filled rubber under elongation is simulated. For CB (N330) filled natural rubber with volume fraction of 27.5%, the simulated electrical resistivity increases with elongation at small stains, corresponding to the breakup of the agglomerates. The reduction in resistivity at larger strains corresponds to the decrease of the junction width, which results in a decrease of the contact resistance. Good agreement is found between the simulations and the experimental data available in the literature. The simulated results confirm the effects of the breakdown of the CB network and the alignment of CB aggregates under strain on the electrical resistivity. 相似文献
84.
Hong Gao Lan Liu Yuan-Fang Luo De-Min Jia Jia-Sheng Lu 《Journal of Macromolecular Science: Physics》2013,52(10):1939-1954
In order to simultaneously improve the conductivity and stabilize the contact resistance of electrically conductive adhesives (ECAs) containing silver flakes, different types of aminoaldehydes as multifunctional additives, N, N-dimethyl-4-aminobenzaldehyde (DABA), benzaldehyde (BA) as a comparison, and formamide (FA), were introduced into ECAs formulations. The results showed that when the optimal levels of FA, BA, and DABA were individually added into ECAs, the decrease in the resistivities of the ECAs were 34.8%, 67.2%, and 41.7%, respectively, compared to the control sample. This is because, during the curing process, the aldehyde acts as a reducing agent and reduces the oxidized silver flakes. Furthermore, the ECAs with FA or DABA had better contact resistance stability than that of the control sample under the condition of 85°C/85% relative humidity, but ECAs with BA could not stabilize the contact resistance on tin finish, The results indicate that FA and DABA can be adsorbed onto the tin surface and inhibit the occurrence of the galvanic corrosion on the interface between ECA and tin finish. The rheological results showed the processability of ECAs with FA, BA, and DABA were better than that of the control sample. However, the shear strength of ECAs with BA and DABA slightly declined. 相似文献
85.
Abstract High pressure electrical measurements were conducted in the antiferromagnetic insulator CoI, using a miniature Diamond Anvil Cell (DAC). The existence of a Mott Transition predicted from high pressure 129I Mgssbauer Spectroscopy (MS)1 has been verified. At about 8 GPa the system becomes metal1ic as evidenced by the temperature behavior of the conductivity. The conductivity at room temperature, however, still increases with increasing pressure, leveling off at 11 GPa. The metallic behavior in the 8 -11 GPa is explained by coexistence of metallic and insulating clusters via a percolating process. Above 11 GPa the material is completely metallic. This mechanism is consistent with the MS findings. 相似文献
86.
Abstract The temperature dependences of the resistivity of La0.7Ca0.3Mn1?xFexO3 and La0.7Ca0.3Mn1?xFexO3 (0 < × < 0.04) mixed crystals were studied under hydrostatic pressures up to 15kbar. The substitution of Fe for Mn results in an increase of the resistivity and a continuous decrease of the metal-insulator transition temperature Tmi while the substitution of Ge for Mn leads to a more complicated Tmi(x)-curve. In all cases Tmi shifts under pressure with a rate between 1.6 and 2.9K/kbar and a correlation between Tmi and its pressure derivative dTmi/dP is observed which is in accordance with the general trend of dTmi/dP versus Tmi as derived for other manganites and is discussed in terns of a competition between superexchange and double exchange. 相似文献
87.
Normal state resistivity and Hall effect are shown to be successfully modeled by a two-band model of holes and electrons that is applied self-consistently to (i) dc transport data reported for eight bulk-crystal and six oriented-film specimens of YBa2Cu3O7?δ, and (ii) far-infrared Hall angle data reported for YBa2Cu3O7?δ and Bi2Sr2CaCu2O8+δ. The electron band exhibits extremely strong scattering; the extrapolated dc residual resistivity of the electronic component is shown to be consistent with the previously observed excess thermal conductivity and excess electrodynamic conductivity at low temperature. Two-band hole–electron analysis of Hall angle data suggests that the electrons possess the greater effective mass. 相似文献
88.
ABSTRACTThe evolution of dislocations during shape-change of metal forms results from microstructural shear mechanism that is essential to enhance ductility. However, at room temperatures for face-centred cubic metals, this evolution results in the generation of vacancies that tend to form nano-voids, the growth of which leads to ductile failure. The correlated occurrence of dislocations and vacancies may be differentiated using the change of resistivity with plastic strain at 4.2?K, because resistivity is very sensitive to single vacancies compared to the formation of stacking faulted defects and dislocations. In order to assess the microstructure, the specific resistivity of these defect species was measured at 4.2?K, whereby thermal recovery processes are non-existent. The resistivity per dislocation line-length per volume was determined to be 1.87?×?10?25?Ωm3 for super-pure aluminium. The change in resistivity directly correlated to the shear flow stress squared. Vacancy-like defects formed during plastic flow were correlated to the recoverable resistivity after 298?K anneal and the derived volume fraction (CV) from mechanical data. The magnitude could be expressed as 12.9?×?10?9?Ωm per CV in % or as 1.21?×?10?25?Ωm3 in terms of line-length of vacancies per volume. The choice of representation depends on the presumed vacancy distribution. However, the recoverable flow stress upon 298?K anneal only appear to be proportional to √ CV at low strains; that is, at high strains the generated vacancies had transformed to defects that give rise to a small decrease in resistivity but a more notable increase in the flow stress. The possible mechanisms for this transformation are discussed. 相似文献
89.
Antistatic poly(vinyl chloride)/quaternary ammonium salt based ion-conductive acrylate copolymer (PVC/QASI) composites were successfully prepared in a Haake torque rheometer. The surface resistivity of the PVC/QASI composites could be reduced to 107 Ω sq?1 order of magnitude when the QASI content reached 20 phr (parts per hundreds of resin). The surface resistivity of the composites was slightly sensitive to the relative humidity (RH), showing a good antistatic ability under an RH of 12%. Mechanical properties tests, differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) were also used to investigate the tensile strength, elongation at break, thermal properties, and morphology of the PVC/QASI composites, respectively. 相似文献
90.
To probe the effect of the protein environment on the retinal chromophore of rhodopsin, we performed molecular dynamics simulations using combined quantum mechanics/molecular mechanics (QM/MM). The starting geometry of the protein is based on the 2.6Å X-ray structure of bovine rhodopsin of Okada et al. [T. Okada, et al. Proc. Natl. Acad. Sci. USA 99 5982 (2002)]. The wild-type chromophore of rhodopsin according to our calculations shows a highly twisted conformation around the central region, from C10 to C13, due to non-bonded interaction with the protein pocket. The absolute sense of twist of the C11–C12 and C12–C13 bonds is negative (?19 ± 9°) and positive (170 ± 8°), respectively. The 13-demethyl retinal chromophore, in which the methyl group at the C13 position is removed, is less distorted in this region. The C11–C12 bond is less twisted (?15 ± 10°) and the C12–C13 bond is planar (179 ± 9°) . The flattened geometry of this artificial chromophore is supported by spectroscopic evidence. 相似文献