A continuous electrical resistivity measurement in thin films

The continuous electrical resistivity measurement, while an interesting parameter is being changed, can be a useful tool for in-situ thin film analysis as most changes in films are accompanied by changes in the electrical resistivity. In-situ measurements in a tube furnace at atmospheric pressure during different heat treatments are presented for oxidation tracing in Cr films and the TiN/CrN multilayer and for detection of interactions in Ni/Si}, Ti/Si} and Ni/Al multilayers. Results of electrical resistivity measurements c correlated well with weight gain measurements, X-ray diffraction, Rutherford backscattering spectroscopy and Auger electron spectroscopy depth profiling. It is therefore shown that the measurement of the resistivity with its time and temperature derivatives can represent a useful basis for the application of other analytical methods.     

Method of electrical resistivity measurement for high-temperature melts

A contactless method of electrical resistivity measurement for high-temperature melts is described. The method is based on induction melting in split water-cooled crucible and solving the inverse problem of electromagnetic field with the use of the thermal and electrical parameters of an induction system. Results of the electrical resistivity measurement of a pure-grade aluminum oxide melt within the temperature range of 2300–2950°C in air are presented.     

Coupled region and area fraction of primary phases in Sb-InSb eutectic alloys

Unidirectional solidification of Sb-InSb alloys, 26-34wt% In, was carried out in the range of growth rate 1.2 × 10^–4 to 1.2 × 10^–1 cms^–1 and with a temperature gradient 57° C cm^–1. An explanation is given which relates the coupled region with quantitative data concerning the primary phases, e.g. the area fraction and the protrusion length ahead of the eutectic interface. The coupled region can be constructed with reasonable accuracy from those quantities measured. The estimated coupled region is in qualitative agreement with the experimental result.     

Characterization of microstructural changes in an Al-6.8 wt.% Mg alloy by electrical resistivity measurements

Microstructural changes in an AlMg6.8 alloy after different thermo mechanical (TMT) and sensitization treatments were investigated by electrical resistivity measurements. The electrical resistivity was most affected by the content of Mg solute atoms in the α-Al matrix, due to β-phase precipitation, while contribution of the dislocation density to the resistivity of the AlMg6.8 alloy was less pronounced. The amount and distribution of the β-phase precipitated during sensitization were found to be strongly affected by the microstructure developed under the previously applied TMTs, i.e. by the dislocation density and the primary β-phase particles in the dual (α + β) phase structure. During sensitization of the specimens with a recovered/recrystallized dual (α + β) phase structure, precipitation of randomly distributed, globular β-phase particles occurred. Sensitization of cold deformed and recrystallized single α-Al structures induced β-phase precipitation in the form of a continuous layer along the shear bands/grain boundaries.     

Crystallization study of amorphous Fe40Ni40B20 by electrical resistivity measurement

The crystallization in amorphous Fe₄₀Ni₄₀B₂₀ alloy has been studied by electrical resistivity measurement. It shows a three stage compared to the more conventional two-stage crystallization behaviour in many metallic glasses. The Johnson-Mehl-Avrami equation was found to be operative only for 40% transformed crystallized volume for the highest measured isotherm (740 K). The Avrami exponent and activation energy were found to be 1.75 and 53 kcal mol^–1, respectively. The low activation energy in the amorphous alloy has been explained by the structural relaxation model.     

A new method forin-situ measurement of electrical resistivity of reinforced concrete

A new method is described for thein-situ measurement of electrical resistivity of concrete structures. The method is based on the early work of J. Newman who calculated the electrolyte resistivity between a disk and a counter electrode located at infinity. This method has the advantage compared with Wenner's of using a single small electrode for the measurements. In this paper, results are presented comparing this method with Wenner's and with results carried out using a conductivity cell in electrolytes. Finally, values of resistivity are compared to corrosion intensity, and a threshold for active corrosion is suggested.

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Résumé On décrit une nouvelle méthode de mesure de la résistivité électrique du béton dont la technique est basée sur un travail ancien de J. Newman qui avait calculé la résistivité entre un disque et une électrode auxiliaire placée à l'infini. Comparée à la méthode de Wenner, cette méthode présente l'avantage de n'utiliser, pour les mesures, qu'une petite électrode. Dans cet article, on présente les résultats de la comparaison établie avec la méthode de Wenner et avec les résultats obtenus avec une cellule de conductivité placée dans les électrolytes. Enfin, on compare les valeurs de la résistivité du béton avec celles de l'intensité de la corrosion et on suggère un seuil de corrosion active.

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Editorial note Camen Andrade and Maria-Cruz Alonso are working at the Instituto Eduardo de Torroja which is a RILEM Titular Member. Dr. Andrade, who was the 1986 RILEM Medallist, have had all these years great responsibilities within RILEM. Chairlady of the Advisory Technical Committee until 1993, she is now a member of the Coordinating Committee. She is active in 116-PCD Technical Committee on Permeability of Concrete as a Criterion of its Durability and has been appointed chairdlady of 154-EMC Technical Committee on Electrochemical Techniques for Measuring Metallic Corrosion. Carmen Andrade has been appointed RILEM Fellow in 1995.     

Nondestructive sensing evaluation of surface modified single-carbon fiber reinforced epoxy composites by electrical resistivity measurement

Nondestructive sensing of a single-carbon fiber reinforced epoxy composites was evaluated by the measurement of electrical resistivity under reversible cyclic loading. For the strain–stress sensing, the strain up to the maximum load of a bare carbon fiber itself is larger than that of carbon fiber composite. As curing temperature increased, apparent modulus up to the maximum load increased and the elapsed time became shorter. Higher residual stress might contribute to the improved interfacial adhesion. The strain up to the maximum load at low temperature was larger than that at higher temperature. The strain of electrodeposition (ED) treated carbon fiber was smaller than that of the untreated carbon fiber composite until the maximum load reached. This could be due to higher apparent modulus of composite based on the improved interfacial shear strength (IFSS). Since the electrical resistivity was responded well quantitatively with various parameters, such as matrix modulus, the fiber surface modification, the electrical resistivity measurement can be a feasible method of nondestructive sensing evaluation for conductive fiber reinforced composites inherently.     

A device for contactless measurement of electrical resistivity of metals and alloys

A simple apparatus for contactless mesurement of resistivity is described. The method is based on the change in penetration depth of electromagnetic fields (due to the skin effect) by the change of the conductivity of a foil.     

Real-time PCR measurement by fluorescence anisotropy

We have developed an instrument for monitoring real-time PCR using fluorescence anisotropy, enabling an assay chemistry in which the fluorescence from a labeled primer elucidates amplification. The instrument holds the sample temperature constant to within +/-0.03 degrees C during measurement in the extension phase of each PCR cycle and achieves 0.116 mP FA resolution. Primer conjugation with Alexa-Fluor 488, when compared with other fluorophores, is shown to provide the greatest FA range between primer and product. Comparable reproducibility and linearity of the crossing point for a range of target copy numbers is observed between the FA-based assay run in our instrument and the SYBR green assay run in commercial instrumentation. Reproducibility is also consistent with Poisson-distributed experimental error in aliquoting starting copies, a theoretical limit to instrument/assay performance.     

Electrical resistivity anisotropy in layered p-SnSe single crystals

Single crystals of p-type SnSe were grown by both direct vapor transport (DVT) and chemical vapor transport (CVT) techniques. The d.c. electrical resistivity anisotropy has been investigated for the first time in these layered crystals. The DVT grown crystals exhibited a large anisotropy ratio and also a higher activation energy compared to that of CVT grown crystals. The electron microscopic examination revealed the presence of a large concentration of stacking faults in the DVT grown crystals. The resistivity anisotropy is accordingly discussed in terms of stacking disorder.     

Determination of rolling anisotropy by extensometry

A theory is presented for the determination of three coefficients characterizing anisotropic materials. These new coefficients of anisotropy advantageously replace Lankford's classic empirical coefficient,r, in the definition of the anisotropy of a rolled sheet. It is shown how these coefficients ₀, ₄₅ and ₉₀ may be deduced from the theory, provided certain assumptions are made concerning the rolled material. The validity of the theory was tested through experiments on rolled ultra high-purity iron sheet, ₀, ₄₅ and ₉₀ being determined by means of a special purpose-built extensometer.     

The electrical resistivity of protactinium metal

The electrical resistivity of protactinium metal has been measured between 0.90 and 300 K. The absolute value of the resistivity is between that of thorium and uranium, with ₂₉₈ =19.28 µ -cm. A change in slope of the resistivity was observed at 103 K and remains unexplained. No superconductivity was observed down to 0.9 K. The resistivity ratio ₂₇₃ / _o was 9.27, showing the sample to be reasonably pure.     

Investigation of the thermal expansion,electrical resistivity,and magnetic susceptibility anisotropy in PbMo6S8 single crystals

We measure the thermal expansion, electrical resistivity, and magnetic susceptibility of PbMo₆S₈ single crystals (with aT _c value of 14.2 K) along a twofold and a threefold axis. We find a large anisotropy in the three types of measurements. Results are discussed in terms of peculiarities of the phonon spectrum of Chevrel-phase compounds.     

Fracture toughness of eutectic Al-Si casting alloy with different microstructural features

The static fracture toughness of a series of eutectic Al-Si casting alloy with different microstructural features has been evaluated. The dominant influence of eutectic silicon in controlling the fracture toughness is thus clarified. The relationship between the fracture toughness and the microstructure was established. Fracture toughness was found to be strongly associated with the size and morphology of silicon particles. The other feature which greatly influences the fracture toughness is the ratio (/DE)_Si, i.e. the silicon particle spacing divided by the equivalent particle diameter, rather than the silicon particle spacing, _Si. Fracture toughness also correlates well with the void growth parameter, VGP (=_y (/DE)_Si), proposed by the authors. The results of the present work can be used to develop an understanding of the variation of fracture toughness with the microstructural features of eutectic Al-Si alloys.     

发泡镍电阻率的孔率计算法

通过有关计算公式的应用分析,找到了较合适的发泡镍电阻率用孔率计算的方法,从而为高性能电极基体材料和发泡镍电阻率的生产控制提供便利。     

Low-frequency measurement of anisotropy field

A number of different methods of measuring the anisotropy field HKof magnetic films were investigated for application to the automation of low-frequency measurements. These methods included torque, the large signal susceptibility method recommended by the IEEE,[5] the small signal susceptibility, and a new method using the second harmonic component of the magnetization signal. The agreement between the IEEE method and the second harmonic method was found to be good. Both these methods also gave good agreement with values obtained for torque measurements.     

Anomalous electrical resistivity of thin gadolinium films

Electrical resistivity measurements at room temperature on thin gadolinium films in the thickness range 200–1000 Å are described. The resistivity-thickness curve in this case is anomalous in the sense that it exhibits a decrease in resistivity at lower thicknesses (less than about 500 Å). This is in marked contrast with other work and seems to represent the first observation of a resistivity decrease with decreasing thickness. It is suggested that this curious resistivity characteristic in Gd films results from the thickness dependences of the structural phase and of the spin-disorder resistivity.     

The electrical resistivity of some castable zirconias

The variation of electrical resistivity with temperature has been measured for four castable zirconias: 6.0 mole % calcia-stabilised, 8.5 mole % yttria-stabilised, and 25 and 50 mole % ceria-stabilised zirconia. The calcia-and yttria-stabilised castables need to be sintered at over 2000° K to develop their electrical conductivity fully, but that of the ceria-stabilised castables is independent of sintering temperature, and is similar to that of normally prepared ceramic. The castables are discussed with particular reference to their possible application as M H D electrode materials.