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R Z Valiev - One of the best experts on this subject based on the ideXlab platform.
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nanostructured cu cr alloy with high strength and Electrical Conductivity
Journal of Applied Physics, 2014Co-Authors: R K Islamgaliev, Konstantin M Nesterov, J Bourgon, Yannick Champion, R Z ValievAbstract:The influence of nanostructuring by high pressure torsion (HPT) on strength and Electrical Conductivity in the Cu-Cr alloy has been investigated. Microstructure of HPT samples was studied by transmission electron microscopy with special attention on precipitation of small chromium particles after various treatments. Effect of dynamic precipitation leading to enhancement of strength and Electrical Conductivity was observed. It is shown that nanostructuring leads to combination of high ultimate tensile strength of 790–840 MPa, enhanced Electrical Conductivity of 81%–85% IACS and thermal stability up to 500 °C. The contributions of grain refinement and precipitation to enhanced properties of nanostructured alloy are discussed.
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a nanostructural design to produce high strength al alloys with enhanced Electrical Conductivity
Scripta Materialia, 2014Co-Authors: R Z Valiev, Yu M Murashkin, I SabirovAbstract:The high strength and increased Electrical Conductivity of the Al alloys are highly desirable for their applications in power transmission lines. However, high strength and high Electrical Conductivity are mutually exclusive in metallic materials. A novel nanostructuring strategy is reported that achieves Al–Mg–Si alloys with superior tensile strength and enhanced Electrical Conductivity. The new strategy is based on a combination of grain refinement down to ultra-fine scale with accelerated formation of nanosized precipitates during severe plastic deformation.
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enhanced mechanical properties and Electrical Conductivity in ultrafine grained al alloy processed via ecap pc
Journal of Materials Science, 2013Co-Authors: Yu M Murashkin, R Z Valiev, I Sabirov, V U Kazykhanov, E V Bobruk, A A DubravinaAbstract:The objective of this work is to study the effect of grain refinement using equal channel angular pressing with parallel channels (ECAP-PC) on microstructure, mechanical properties, and Electrical Conductivity of an Al–Mg–Si alloy. The coarse grained (CG) material is subjected to ECAP-PC processing at 100 °C for 1, 2, and 6 passes. Mechanical behavior of the Al–Mg–Si alloy after ECAP-PC processing and its Electrical Conductivity are analyzed with respect to the microstructure developed during ECAP-PC processing. The effect of artificial aging (AA) on the microstructure, mechanical properties, and Electrical Conductivity of the ECAP-PC processed Al–Mg–Si alloy is investigated. It is shown that the microstructure developed during ECAP-PC processing affects the kinetics of the aging process that, in turn, affects the mechanical properties and Electrical Conductivity of the material. It is demonstrated that both mechanical properties and Electrical Conductivity of the Al–Mg–Si alloy can be simultaneously enhanced via intelligent microstructural design through optimization of the thermo-mechanical processing applied to this material.
Takashi Yoshino - One of the best experts on this subject based on the ideXlab platform.
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Electrical Conductivity of stishovite as a function of water content
Physics of the Earth and Planetary Interiors, 2014Co-Authors: Takashi Yoshino, Akira ShimojukuAbstract:Abstract The Electrical Conductivity of stishovite with various Al2O3 and H2O contents was measured at 12 GPa of pressure (P) and temperatures (T) up to 1900 K in a Kawai-type multi-anvil apparatus. Starting materials were pre-synthesized at 12 GPa and 1673 K from various mixtures of SiO2, Al2O3 and Al(OH)3. The synthesized stishovite aggregates contained various H2O concentrations up to 0.25 wt.%. The Conductivity of relatively dry stishovite was almost constant independently of Al content, whereas the Conductivity significantly increased with increasing H2O content in stishovite. All Electrical Conductivity data fit the formula for Electrical Conductivity σ = σ 0 C W exp { - [ Δ H 0 - α C W 1 / 3 ] / kT } , where σ0 is the pre-exponential term, CW is the H2O concentration, ΔH0 is the activation enthalpy at very low H2O concentration, and k is the Boltzmann constant. The activation enthalpy decreased from 1.22 to 0.90 eV with increasing H2O content from 0.01 to 0.22 wt.%. A nearly linear correlation of the Conductivity values on the H2O content suggests that the dominant mechanism of charge transport in stishovite is proton conduction. Although Electrical Conductivity of hydrous stishovite is higher than that of garnet in the subducted oceanic crust, small amount of hydrous stishovite is insufficient to raise Conductivity. On the other hand, hydrous stishovite can contribute to the high Conductivity occasionally observed at the mantle transition zone, if the subducted Archean continental crusts with tonalite–trondhjemite–granodiorite (TTG) composition were accumulated above the 660 km seismic discontinuity.
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re evaluation of Electrical Conductivity of anhydrous and hydrous wadsleyite
Earth and Planetary Science Letters, 2012Co-Authors: Takashi Yoshino, Tomoo KatsuraAbstract:Abstract Recent laboratory Electrical Conductivity measurements of the main mantle constituent minerals have represented considerable efforts to determine the effects of water content on Electrical Conductivity. However, there are large discrepancies between the results of Yoshino et al. (2008a) and those of Dai and Karato (2009a) on hopping conduction and the effects of water on the Electrical Conductivity of wadsleyite. To investigate the cause of these discrepancies, the Electrical Conductivity of anhydrous and hydrous wadsleyite were newly measured under low and high temperature conditions by impedance spectroscopy. The Conductivity values of dry wadsleyite aggregates with less than 2 ppm H2O by weight were similar to those for hopping conduction reported by Yoshino et al. (2008a) and distinctly higher than those of Dai and Karato (2009a) . For hydrous wadsleyite, at temperatures below 1000 K, the Electrical Conductivity in an Arrhenius plot was repeatable along the heating–cooling paths and was similar to the results of Yoshino et al. (2008a) . The impedance spectrum in the complex impedance plane of hydrous wadsleyite showed a semicircular shape, and the infrared spectrum did not show any shape change after the Conductivity measurements. In contrast, when the temperature exceeds 1000 K, the Electrical Conductivity in an Arrhenius plot showed higher activation enthalpy. The impedance spectra were greatly distorted and the impedance arc contained at least two relaxation processes. This shape is similar to those reported by Dai and Karato (2009a) who measured the Conductivity above 1000 K. The infrared spectra showed a large contribution from molecular water after Conductivity measurements, suggesting significant dehydration during the Conductivity measurements. In summary, the results obtained from Conductivity measurements at higher temperatures (>1000 K) do not represent the proton conduction in the grain interior.
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Electrical Conductivity of fluid bearing quartzite under lower crustal conditions
Physics of the Earth and Planetary Interiors, 2012Co-Authors: Akira Shimojuku, Takashi Yoshino, Daisuke Yamazaki, Takamoto OkudairaAbstract:Abstract The Electrical Conductivity of fluid-bearing quartzite was determined as function of temperature and fluid fraction at 1 GPa in order to assess the origin of the high Conductivity anomalies observed in the middle to lower crustal levels. Dihedral angles of quartz-fluid-quartz determined from recovered samples were below 60°, suggesting that fluid forms an interconnected network through the quartz aggregate. The Electrical Conductivity of quartzite increases with increasing temperature, which can be approximately expressed by Arrhenius equation. The apparent activation enthalpy decreases from 0.70 to 0.25 eV with increasing fluid fraction in volume from 0.00043 to 0.32. The Electrical Conductivity (σ) of the fluid-bearing quartzite increased with fluid fraction (ϕ) proportionally to a power law (σ ∝ ϕ0.56–0.71) within the temperature range of 900–1000 K. The Electrical Conductivity of the aqueous fluid-bearing quartzite with the maximum fluid fraction (0.32) was found to be about three orders of magnitude higher than that of dry quartzite at 1000 K. However, its Electrical Conductivity was definitely lower than the geophysically observed values of high-Conductivity anomalies, even if the quartzite contained large fluid fractions (0.32). The present results suggest that fluid-bearing quartzite is unable to account for the high-Conductivity anomalies in terms of fluid fraction. A significant amount of other ionic species, such as Na, Cl, and Al in aqueous fluid, in addition to silica phases dissolved in fluid, is required to increase Conductivity.
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Laboratory Electrical Conductivity Measurement of Mantle Minerals
Surveys in Geophysics, 2010Co-Authors: Takashi YoshinoAbstract:Electrical Conductivity structures of the Earth’s mantle estimated from the magnetotelluric and geomagnetic deep sounding methods generally show increase of Conductivity from 10^−4–10^−2 to 10^0 S/m with increasing depth to the top of the lower mantle. Although Conductivity does not vary significantly in the lower mantle, the possible existence of a highly conductive layer has been proposed at the base of the lower mantle from geophysical modeling. The Electrical properties of mantle rocks are controlled by thermodynamic parameters such as pressure, temperature and chemistry of the main constituent minerals. Laboratory Electrical Conductivity measurements of mantle minerals have been conducted under high pressure and high temperature conditions using solid medium high-pressure apparatus. To distinguish several charge transport mechanisms in mantle minerals, it is necessary to measure the Electrical Conductivity in a wider temperature range. Although the correspondence of data has not been yet established between each laboratory, an outline tendency of Electrical Conductivity of the mantle minerals is almost the same. Most of mineral phases forming the Earth’s mantle exhibit semiconductive behavior. Dominant conduction mechanism is small polaron conduction (electron hole hopping between ferrous and ferric iron), if these minerals contain iron. The phase transition olivine to high-pressure phases enhances the Conductivity due to structural changes. As a result, Electrical Conductivity increases in order of olivine, wadsleyite and ringwoodite along the adiabat geotherm. The phase transition to post-spinel at the 660 km discontinuity further can enhance the Conductivity. In the lower mantle, the Conductivity once might decrease in the middle of the lower mantle due to the iron spin transition and then abruptly increase at the condition of the D″ layer. The impurities in the mantle minerals strongly control the formation, number and mobility of charge carriers. Hydrogen in nominally anhydrous minerals such as olivine and high-pressure polymorphs can enhance the Conductivity by the proton conduction. However, proton conduction has lower activation enthalpy compared with small polaron conduction, a contribution of proton conduction becomes smaller at high temperatures, corresponding to the mantle condition. Rather high iron content in mantle minerals largely enhances the Conductivity of the mantle. This review focuses on a compilation of fairly new advances in experimental laboratory work together with their explanation.
Shunichiro Karato - One of the best experts on this subject based on the ideXlab platform.
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Electrical Conductivity of amphibole bearing rocks influence of dehydration
Contributions to Mineralogy and Petrology, 2012Co-Authors: Duojun Wang, Yingxing Guo, Shunichiro KaratoAbstract:We investigated the Electrical Conductivity of amphibole-bearing rocks under the conditions of the middle to lower crust. Alternating current measurements were performed in the frequency range of 10–106 Hz in a cubic-anvil high-pressure apparatus at 0.5–1.0 GPa and 373–873 K. The Electrical Conductivity of these rocks is weakly temperature dependent below ~800 K with modest anisotropy and relatively low Conductivity (~5 × 10−3 S/m at ~750 K with the activation enthalpy of 64–67 kJ/mol). However, the Electrical Conductivity starts to increase with temperature more rapidly above ~800 K (activation enthalpy of 320–380 kJ/mol). The infrared spectroscopy observations indicate that dehydration occurs in this high temperature regime. The observed high activation enthalpy and the reproducibility suggest that the enhanced Conductivity is not due to the direct effect caused by the generation of conductive fluids. Dehydration of amphibole is associated with the oxidation of iron (from ferrous to ferric), and we suggest that the increased Conductivity associated with dehydration is caused by oxidation. This effect may explain high Electrical Conductivity observed in some regions of the continental crust.
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Electrical Conductivity of orthopyroxene implications for the water content of the asthenosphere
Proceedings of the Japan Academy. Series B Physical and biological sciences, 2009Co-Authors: Lidong Dai, Shunichiro KaratoAbstract:Electrical Conductivity of minerals is sensitive to water content and hence can be used to infer the water content in the mantle. However, previous studies to infer the water content in the upper mantle were based on pure olivine model of the upper mantle. Influence of other minerals particularly that of orthopyroxene needs to be included to obtain a better estimate of water content in view of the high water solubility in this mineral. Here we report new results of Electrical Conductivity measurements on orthopyroxene, and apply these results to estimate the water content of the upper mantle of Earth. We found that the Electrical Conductivity of orthopyroxene is enhanced by the addition of water in a similar way as other minerals such as olivine and pyrope garnet. Using these new results, we calculate the Electrical Conductivity of pyrolite mantle as a function of water content and temperature incorporating the temperature and water fugacity-dependent hydrogen partitioning. Reported values of asthenosphere Conductivity of 4 × 10−2−10−1 S/m corresponds to the water content of 0.01–0.04 wt%, a result in good agreement with the petrological model of the upper mantle.
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the effect of water on the Electrical Conductivity of olivine
Nature, 2006Co-Authors: Duojun Wang, Mainak Mookherjee, Shunichiro KaratoAbstract:It is well known that water (as a source of hydrogen) affects the physical and chemical properties of minerals--for example, plastic deformation and melting temperature--and accordingly plays an important role in the dynamics and geochemical evolution of the Earth. Estimating the water content of the Earth's mantle by direct sampling provides only a limited data set from shallow regions (<200 km depth). Geophysical observations such as Electrical Conductivity are considered to be sensitive to water content, but there has been no experimental study to determine the effect of water on the Electrical Conductivity of olivine, the most abundant mineral in the Earth's mantle. Here we report a laboratory study of the dependence of the Electrical Conductivity of olivine aggregates on water content at high temperature and pressure. The Electrical Conductivity of synthetic polycrystalline olivine was determined from a.c. impedance measurements at a pressure of 4 GPa for a temperature range of 873-1,273 K for water contents of 0.01-0.08 wt%. The results show that the Electrical Conductivity is strongly dependent on water content but depends only modestly on temperature. The water content dependence of Conductivity is best explained by a model in which Electrical conduction is due to the motion of free protons. A comparison of the laboratory data with geophysical observations suggests that the typical oceanic asthenosphere contains approximately 10(-2) wt% water, whereas the water content in the continental upper mantle is less than approximately 10(-3) wt%.
Hengzhong Zhang - One of the best experts on this subject based on the ideXlab platform.
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pressure dependence of Electrical Conductivity of black titania hydrogenated at different temperatures
Journal of Physical Chemistry C, 2019Co-Authors: Junxiu Liu, Jiejuan Yan, Qiwu Shi, Hongliang Dong, Jinbo Zhang, Zhongwu Wang, Wanxia Huang, Bin Chen, Hengzhong ZhangAbstract:Temperature can control the degree of hydrogenation of titania (i.e., black TiO2), determining the defect chemistry and hence its optical absorption and Electrical Conductivity that are key to the photocatalytic activity. However, how pressure affects the two key factors is unknown. In this work, we used a diamond anvil cell to produce the required high pressure (HP) and studied the pressure dependences of the structure change, the Electrical Conductivity, and the light absorption of black titania using HP X-ray diffraction, Raman/UV–vis spectroscopy, and Electrical transport measurements. Results reveal that accompanying the HP phase transition the Electrical Conductivity exhibits complex variation with pressure, in good accord with the band gap changes of involved HP phases as a function of pressure. This confirms the assumption that pressure affects the Electrical Conductivity of black titania via controlling the number of free electrons (holes) distributed in the conduction (valence) band, which is in...
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pressure dependence of Electrical Conductivity of black titania hydrogenated at different temperatures
The Journal of Physical Chemistry, 2019Co-Authors: Junxiu Liu, Jiejuan Yan, Qiwu Shi, Hongliang Dong, Jinbo Zhang, Zhongwu Wang, Wanxia Huang, Bin Chen, Hengzhong ZhangAbstract:Temperature can control the degree of hydrogenation of titania (i.e., black TiO₂), determining the defect chemistry and hence its optical absorption and Electrical Conductivity that are key to the photocatalytic activity. However, how pressure affects the two key factors is unknown. In this work, we used a diamond anvil cell to produce the required high pressure (HP) and studied the pressure dependences of the structure change, the Electrical Conductivity, and the light absorption of black titania using HP X-ray diffraction, Raman/UV–vis spectroscopy, and Electrical transport measurements. Results reveal that accompanying the HP phase transition the Electrical Conductivity exhibits complex variation with pressure, in good accord with the band gap changes of involved HP phases as a function of pressure. This confirms the assumption that pressure affects the Electrical Conductivity of black titania via controlling the number of free electrons (holes) distributed in the conduction (valence) band, which is inversely proportional to the exponent of the band gap that scales almost linearly with the pressure. This work provides a fundamental understanding of the pressure-induced structure–property relationship in black titania and will have important implications for tuning the photocatalytic activity via pressure and for developing new applications such as pressure sensors.
X.-grant Chen - One of the best experts on this subject based on the ideXlab platform.
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Optimization of mechanical properties and Electrical Conductivity in Al–Mg–Si 6201 alloys with different Mg/Si ratios
Journal of Materials Research, 2020Co-Authors: Siamak Nikzad Khangholi, Mousa Javidani, Alexandre Maltais, X.-grant ChenAbstract:The effects of the Mg/Si ratio and aging treatment on the strength and Electrical Conductivity of Al–Mg–Si 6201 conductor alloys were investigated. Four experimental alloys with different Mg/Si ratios of 2, 1.5, 1, and 0.86 and with a constant Mg level of 0.65 wt% were prepared. It was revealed that excessive Si (a low Mg/Si ratio) increased the peak strength, while the corresponding Electrical Conductivity decreased. To fulfill the minimum required Electrical Conductivity (52.5% IACS), the alloys with low Mg/Si ratios required a longer aging time after peak aging to improve Electrical Conductivity. The alloy with an Mg/Si ratio of ~1 was the best candidate, exhibiting the highest strength up to 54% IACS. On the high end of Electrical Conductivity (54–56% IACS), the alloy with an Mg/Si ratio of ~1.5 provides a better compromise between strength and Electrical Conductivity. Furthermore, the strengthening mechanisms and the factors influencing Electrical Conductivity were discussed for further optimization.