Thermal Potential Improvement of an Earth-Air Heat Exchanger (EAHE) by Employing Backfilling for Deep Underground Emergency Ventilation

A problem was presented to observe the packing densities of deposits of sub-micron corrosion product particles. The deposits were 5-100 mils thick and had formed on the inside surfaces of 3/8 inch diameter Zircaloy-2 heat exchanger tubes. The particles were iron oxides deposited from flowing water and consequently were only weakly bonded. Particular care was required during handling to preserve the original formations of the deposits. The specimen preparation method described below allowed direct observation of cross sections of the deposit layers by transmission electron microscopy.The specimens were short sections of the tubes (about 3 inches long) that were carefully cut from the systems. The insides of the tube sections were first coated with a thin layer of a fluid epoxy resin by dipping. This coating served to impregnate the deposit layer as well as to protect the layer if subsequent handling were required.

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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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“Getting High Resolution Out of A High Voltage Microscope”

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s143192760000355x ◽

1980 ◽

Vol 38 ◽

pp. 822-825

Author(s):

David J. Smith

Keyword(s):

Electron Microscope ◽

High Resolution ◽

High Voltage ◽

Theoretical Limit ◽

Voltage Electron ◽

High Voltage Electron Microscope ◽

High Voltage Electron ◽

Technological Advances ◽

Potential Improvement ◽

Lower Voltage

The initial attractions of the high voltage electron microscope (HVEM) stemmed mainly from the possibility of considerable increases in electron penetration through thick specimens compared with conventional 100KV microscopes, although the potential improvement in resolution associated with the decrease in election wavelength had been fully appreciated for many years (eg. Cosslett, 1946)1, even if not realizable in practice. Subsequent technological advances enabled the performance of lower voltage machines to be brought closer to the theoretical limit, to be followed in turn by more recent projects which have been successful, eventually, in achieving even higher resolution with dedicated higher voltage instruments such as those at Kyoto (500KV)2, Munich (400KV)3, Ibaraki (1250KV)4 and Cambridge (600KV)5. It does not necessarily follow however that the performance of journal high voltage microscopes can be easily upgraded, retrospectively, to the same level, as will be discussed in detail below.

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