Effect of Carbon on the Electrical Resistivity of Ni–Al Intermetallic Alloy Synthesized by an Electrothermal Explosion under Pressure

In this paper, we studied the effect of carbon (3 wt. %) on the electrical resistivity of materials based on Ni − Al and Ni – Al − C synthesized by the electrothermal explosion in the temperature range 300 – 1300 K in a vacuum of 2·10–3 Pa. During an electrothermal explosion, a Ni – Al-based melt is formed in a powder reactive medium, in which carbon is dissolved. It is shown that during the crystallization of the final product, due to its low solubility in NiAl, carbon is located on the surface of intermetallic NiAl grains in the form of multilayer graphite nanofilms 50 – 80 nm thick, filling the intergranular space. It is shown that the synthesized materials have a metallic conductivity, and the electrical resistivity in the measured temperature range of 300 – 1300 K increases monotonically for the Ni – Al-based alloy from 16 to 40 mW·cm and for the carbon-containing Ni – Al – C material from 22 to 60 mW·cm. The temperature coefficient of resistance (TCS) also increases from 1.45·10–3 K–1 for NiAl to 1.77·10–3 K–1 for NiAl/C. The slope of the resistivity curves in the studied temperature range of 300 – 1300 K remains constant and is well described by a linear function.

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In-situ electrical-resistivity measurements in the high-voltage electron microscope

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100107484 ◽

1978 ◽

Vol 36 (1) ◽

pp. 68-69

Author(s):

W. E. King

Keyword(s):

Electrical Resistivity ◽

Electron Microscope ◽

High Voltage ◽

Resistivity Measurements ◽

Voltage Electron ◽

High Voltage Electron Microscope ◽

High Voltage Electron ◽

Wide Range ◽

Helium Gas

A side-entry type, helium-temperature specimen stage that has the capability of in-situ electrical-resistivity measurements has been designed and developed for use in the AEI-EM7 1200-kV electron microscope at Argonne National Laboratory. The electrical-resistivity measurements complement the high-voltage electron microscope (HVEM) to yield a unique opportunity to investigate defect production in metals by electron irradiation over a wide range of defect concentrations.A flow cryostat that uses helium gas as a coolant is employed to attain and maintain any specified temperature between 10 and 300 K. The helium gas coolant eliminates the vibrations that arise from boiling liquid helium and the temperature instabilities due to alternating heat-transfer mechanisms in the two-phase temperature regime (4.215 K). Figure 1 shows a schematic view of the liquid/gaseous helium transfer system. A liquid-gas mixture can be used for fast cooldown. The cold tip of the transfer tube is inserted coincident with the tilt axis of the specimen stage, and the end of the coolant flow tube is positioned without contact within the heat exchanger of the copper specimen block (Fig. 2).

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The stabilization of B.C.C. Cu in Cu/Nb nanolayered composites

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100163605 ◽

1996 ◽

Vol 54 ◽

pp. 228-229

Author(s):

H. Kung ◽

A.J. Griffin ◽

Y.C. Lu ◽

K.E. Sickafus ◽

T.E. Mitchell ◽

...

Keyword(s):

Electrical Resistivity ◽

Layer Thickness ◽

Volume Fraction ◽

Ion Beam ◽

High Strength ◽

Cross Sectional ◽

Metastable Structure ◽

High Resolution Tem ◽

Potential Improvement ◽

Two Phases

Materials with compositionally modulated structures have gained much attention recently due to potential improvement in electrical, magnetic and mechanical properties. Specifically, Cu-Nb laminate systems have been extensively studied mainly due to the combination of high strength, and superior thermal and electrical conductivity that can be obtained and optimized for the different applications. The effect of layer thickness on the hardness, residual stress and electrical resistivity has been investigated. In general, increases in hardness and electrical resistivity have been observed with decreasing layer thickness. In addition, reduction in structural scale has caused the formation of a metastable structure which exhibits uniquely different properties. In this study, we report the formation of b.c.c. Cu in highly textured Cu/Nb nanolayers. A series of Cu/Nb nanolayered films, with alternating Cu and Nb layers, were prepared by dc magnetron sputtering onto Si {100} wafers. The nominal total thickness of each layered film was 1 μm. The layer thickness was varied between 1 nm and 500 nm with the volume fraction of the two phases kept constant at 50%. The deposition rates and film densities were determined through a combination of profilometry and ion beam analysis techniques. Cross-sectional transmission electron microscopy (XTEM) was used to examine the structure, phase and grain size distribution of the as-sputtered films. A JEOL 3000F high resolution TEM was used to characterize the microstructure.

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Chemical structure of diamond-like carbon thin films

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010017668x ◽

1990 ◽

Vol 48 (4) ◽

pp. 710-711

Author(s):

N.-H. Cho ◽

K.M. Krishnan ◽

D.B. Bogy

Keyword(s):

Electrical Resistivity ◽

Chemical Structure ◽

Diamond Like Carbon ◽

Chemical Structures ◽

Sputtering Power ◽

Data Aquisition ◽

Equilibrium Phases ◽

Electron Energy Loss ◽

Power Densities ◽

Preparation Techniques

Diamond-like carbon (DLC) films have attracted much attention due to their useful properties and applications. These properties are quite variable depending on film preparation techniques and conditions, DLC is a metastable state formed from highly non-equilibrium phases during the condensation of ionized particles. The nature of the films is therefore strongly dependent on their particular chemical structures. In this study, electron energy loss spectroscopy (EELS) was used to investigate how the chemical bonding configurations of DLC films vary as a function of sputtering power densities. The electrical resistivity of the films was determined, and related to their chemical structure.DLC films with a thickness of about 300Å were prepared at 0.1, 1.1, 2.1, and 10.0 watts/cm2, respectively, on NaCl substrates by d.c. magnetron sputtering. EEL spectra were obtained from diamond, graphite, and the films using a JEOL 200 CX electron microscope operating at 200 kV. A Gatan parallel EEL spectrometer and a Kevex data aquisition system were used to analyze the energy distribution of transmitted electrons. The electrical resistivity of the films was measured by the four point probe method.

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