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Electrical Resistivity Measurements (electrical + resistivity_measurement)
Selected AbstractsElectrical Resistivity and Phase Transformation in SteelsMATERIALWISSENSCHAFT UND WERKSTOFFTECHNIK, Issue 1 2003O. N. Mohanty Elektrischer Widerstand; Phasenumwandlung; Magnetische Eigenschaften Abstract Changes in electrical resistance accompanying transformations in steels with magnetic change (e.g. , , martensite/bainite) and without magnetic change (e.g. , , ,, above Curie temperature) have been examined; the former class affects the resistivity the latter does not. Next, while the efficacy of electrical resistivity measurement in capturing the well-known features of austenite stabilization (e.g. over , ageing, reversibility, and influence of prior martensite amount and so on) in high carbon steels has been reported in an earlier publication, new features (e.g. increase in resistance -increase at very low temperatures, change in temperature co-efficient of resistivity in the stabilized material etc.) are highlighted here. Finally, the work shows that a quantitative estimate of precipitation in the copper bearing, age-hardenable HSLA-100 steel during tempering can be done by continuous electrical resistivity measurement. These data also allow an in-depth kinetic analysis using the Johnson-Mehl-Avrami equation. Zusammenhang zwischen elektrischem Widerstand und Phasenumwandlungen in Stählen Änderungen des elektrischen Widerstands wurden im Zusammenhang mit Phasenumwandlungen, die zu Änderungen der magnetischen Eigenschaften führen (z.B. , , Martensit/Bainit), und solchen, die keine Änderungen der magnetischen Eigenschaften bewirken (z.B. , , , oberhalb der Curie-Temperatur), untersucht. Während sich die erste Umwandlungsart auswirkt, gilt dies für die andere nicht. Während über die Empfindlichkeit von Widerstandsmessungen zur Erfassung der Austenitstabilisierung (z.B. Überalterung, Umkehrbarkeit, Einfluß des vorher vorhandenen Martensitanteils, usw.) in übereutektoiden Stählen in einer früheren Veröffentlichung berichtet wurde, wird im zweiten Teil der hier vorgelegten Veröffentlichung auf neuerdings erfassbare Merkmale (z.B. der Anstieg des Widerstands bei sehr niedrigen Temperaturen, die Änderung der Temperaturabhängigkeit des Widerstands im stabilisierten Material, usw.) eingegangen. Schließlich zeigt die Arbeit, daß durch kontinuierliche Widerstandsmessungen während des Anlassens eine quantitative Abschätzung der Ausscheidungsgehalte im kupferhaltigen, ausscheidungsverfestigenden HSLA-100-Stahl erfolgen kann. Die Daten hierzu erlauben zudem eine vertiefte kinetische Analyse auf Basis der Johnson-Mehl-Avrami-Gleichung. [source] Heterogeneity in skin treated with low-frequency ultrasoundJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 10 2008Joseph Kushner IV Abstract Recent experimental evidence using colored, fluorescent permeants suggests that skin treated with low-frequency sonophoresis (LFS) is perturbed in a heterogeneous manner. Macroscopic and microscopic visualization studies, topical penetration studies, transdermal permeability studies, and skin electrical resistivity measurements have shown that discrete domains, referred to as localized transport regions (LTRs), which are formed during LFS treatment of the skin, possess greatly reduced barrier properties, and therefore exhibit increased permeant skin penetration, compared to the surrounding regions of LFS-treated skin. The transformation of LTR formation from a heterogeneous to a homogeneous phenomenon has the potential benefit of increasing the maximum level of transdermal permeability or of reducing the area of skin required to deliver a desired dose of drug transdermally. Future studies, aimed at elucidating both the mechanisms of LTR formation and the limits of nondamaging formation of LTRs in the skin, are required to incorporate these proposed improvements to enhance the efficacy and practical utility of low-frequency sonophoresis. © 2008 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 97:4119,4128, 2008 [source] Highly efficient bismuth telluride doped p-type Pb0.13Ge0.87Te for thermoelectric applicationsPHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 6 2007Yaniv Gelbstein Abstract Bi2Te3 doped p-type Pb0.13Ge0.87Te samples were prepared by hot pressing. We report on very high power factor values of ,30 ,W/cm K2 at 500 °C, as were determined from Seebeck coefficient and electrical resistivity measurements. From dilatometric characterization, the phase transition from the low temperature rhombohedral to the high temperature cubic NaCl structures, takes place at 373 °C. This transition is accompanied by a continuous and gradual change of the lattice parameters, as was observed by hot stage XRD, suggesting a good mechanical durability upon thermal cycling and operating in large thermal gradients. Rhombohedral distortion of the cubic NaCl structure of Pb1,xGex Te upon cooling, characterized by changes in the interaxial angle , and the lattice parameter. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Effect of heat treatment on various physical properties in Zr80Ni20 metallic glassPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 8 2006I. Kokanovi Abstract The effect of heat treatment on various physical properties in Zr80Ni20 metallic glass has been investigated by means of differential scanning calorimetry and electrical resistivity measurements. Experimental values for the crystallisation temperature and activation energy of the crystallisation processes were derived by studying these processes at different heating rates. The electrical resistivity of the annealed samples up to a temperature slightly above the first crystallization exotherm decreases with decreasing heating rates and increasing annealing temperatures. The temperature dependence of the electrical resistivity of the samples has been interpreted in terms of the weak localization of electrons and contribution by electron,phonon scattering. The contribution by electron,phonon scattering increases with increasing the fraction of crystalline phases in the glass matrix. The superconducting transition temperature, Tc, of the Zr80Ni20 metallic glass annealed at heating rates of 60 K/min and 10 K/min up to annealing temperatures below its second crystallisation exotherm decreases with decreasing heating rates and increasing annealing temperatures. The homogeneity of the annealed Zr80Ni20 metallic glass is discussed by using the superconducting transition width as a criterion. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Effects of oxygen ion implantation in spray-pyrolyzed ZnO thin filmsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 5 2006K. P. Vijayakumar Abstract ZnO thin films, prepared using the chemical spray pyrolysis technique, were implanted using 100 keV O+ ions. Both pristine and ion-implanted samples were characterized using X-ray diffraction, optical absorption, electrical resistivity measurements, thermally stimulated current measurements and photoluminescence. Samples retained their crystallinity even after irradiation at a fluence of ,1015 ions/cm2. However, at a still higher fluence of 2 × 1016 ions/cm2, the films became totally amorphous. The optical absorption edge remained unaffected by implantation and optical absorption spectra indicated two levels at 460 and 510 nm. These were attributed to defect levels corresponding to zinc vacancies (VZn) and oxygen antisites (OZn), respectively. Pristine samples had a broad photoluminescence emission centred at 517 nm, which was depleted on implantation. In the case of implanted samples, two additional emissions appeared at 425 and 590 nm. These levels were identified as due to zinc vacancies (VZn) and oxygen vacancies (VO), respectively. The electrical resistivity of implanted samples was much higher than that of pristine, while photosensitivity decreased to a very low value on implantation. This can be utilized in semiconductor device technology for interdevice isolation. Hall measurements showed a marked decrease in mobility due to ion implantation, while carrier concentration slightly increased. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] ChemInform Abstract: Nitrides with Inverse K2[NiF4] Structure: (R1-xCa3+xN1-x/3)Bi2 with R: Rare Earth Metal.CHEMINFORM, Issue 37 2010Frank Gaebler Abstract The new compounds (La1-xCa3+xN1-x/3)Bi2 (x= 0.10, 0.05, 0.00), (Ce0.7Ca3.3N0.9)Bi2, and (PrCa3N)Bi2 are characterized by powder X-ray and neutron diffraction, magnetic susceptibility, and electrical resistivity measurements. [source] ,-Ca3N2, a Metastable Nitride in the System Ca,NCHEMISTRY - A EUROPEAN JOURNAL, Issue 14 2009Peter Höhn Dr. Abstract A new page in the phase book: The metastable nitride ,-Ca3N2, the synthesis, crystal structure (see picture), and physical properties of which are reported, is an isotype of corundum (,-Al2O3). Vacancies in the crystal structure of ,-Ca3N2 are discussed by using full-potential local orbital methods and taking into account both the physical properties and the density of states. The structural chemistry of calcium nitrides is represented by just two different intermediate phases: cubic Ca3N2 (referred to as ,-Ca3N2, Mn2O3 type structure) and Ca2N (CdCl2 type structure). Other binary phases (",-Ca3N2", "Ca11N8") have been proven to represent cyanamide nitrides, Ca4N2[CN2] and Ca11N6[CN2]2, respectively. The metastable nitride ,-Ca3N2 is prepared either by reaction of freshly distilled calcium metal with nitrogen at 700,K, or by reaction of Ca2N with N2 at 500,K. ,-Ca3N2 transforms monotropically (Ttrans,810,K) to cubic ,-Ca3N2. The crystal structure of ,-Ca3N2 (rhombohedral Rc, no. 167, a=619.884(3),pm, c=1662.958(10),pm) is an isotype of the corundum structure (,-Al2O3) and comprises a network of NCa6/4 octahedra that share common faces and edges. Magnetic susceptibility and electrical resistivity measurements confirm that ,-Ca3N2 is a diamagnetic semiconductor. Die Strukturchemie der Calciumnitride wird von lediglich zwei intermediären Verbindungen bestimmt: kubisches Ca3N2 (nachfolgend als , -Ca3N2 bezeichnet; Mn2O3 -Strukturtyp) und das im CdCl2 -Strukturtyp kristallisierende Ca2N. Die binären Phasen ,, -Ca3N2" und ,Ca11N8" konnten inzwischen als die Cyanamid-Nitride Ca4N2[CN2] und Ca11N6[CN2]2 identifiziert werden. Metastabiles , -Ca3N2 kann entweder durch Reaktion von frisch destilliertem Calcium-Metall mit Stickstoff bei 700,K oder durch Umsetzung von Ca2N mit N2 bei 500,K erhalten werden. , -Ca3N2 transformiert monotrop (Ttrans,810,K) zur kubischen Phase , -Ca3N2. Die Kristallstruktur von , -Ca3N2 (rhomboedrisch Rc, No. 167, a=619.884(3),pm, c=1662.958(3),pm) ist isotyp zur Korundstruktur (, -Al2O3) und besteht aus einem Netzwerk von NCa6/4 -Oktaedern, die über gemeinsame Flächen und Kanten verknüpft sind. Messungen der magnetischen Suszeptibilität und des elektrischen Widerstands zeigen, daß , -Ca3N2 ein diamagnetischer Halbleiter ist. [source] | |||||||||||||