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Title: THE THERMAL EXPANSION OF NIOBIUM PENTOXIDE AND ITS EFFECT ON THE SPALLING OF NIOBIUM OXIDATION FILMS

Abstract

The thermal expansion coefficients of stoichiometric and nonstoichiometric niobium pentoxide were determined from 20 to 1000 l C and 20 to 500 l C, respectively, and were found to be significantly smaller than that of niobium metal. The thermal stresses were calculated which are induced during cooling of a coherent oxide-coated niobium plate. In the absence of volume mismatch of oxide and metal it was concluded that thermal stresses due to differences in expansion coefficients should not cause spalling when the oxidized sample is cooled from 600 l C. A more realistic appraisal, which is consistent with experimentally observed spalling, was made by consideration of the very large strains arising from coherency of the voluminous oxide on the more dense metal. The surface layers of the substrate may deform plastically during oxidation at high temperatures, even though appreciable contamination and strengthening has occurred. Upon cooling, however, the added thermal stresses and decreasing plasticity of the contaminated substrate may lead to spalling, the crack initiating in the contaminated metal and propagating into the brittle oxide. (auth)

Authors:
Publication Date:
Research Org.:
General Electric Co., Pleasanton, Calif.
OSTI Identifier:
4708245
NSA Number:
NSA-17-023883
Resource Type:
Journal Article
Journal Name:
J. Less-Common Metals
Additional Journal Information:
Journal Volume: Vol: 5; Other Information: Orig. Receipt Date: 31-DEC-63
Country of Publication:
Country unknown/Code not available
Language:
English
Subject:
METALS, CERAMICS, AND OTHER MATERIALS; BRITTLENESS; COOLING; CRACKS; DEFORMATION; DUCTILITY; EXPANSION; FILMS; LAYERS; NIOBIUM; NIOBIUM OXIDES; OXIDATION; OXIDES; SURFACES; TEMPERATURE; THERMAL STRESSES

Citation Formats

Douglass, D L. THE THERMAL EXPANSION OF NIOBIUM PENTOXIDE AND ITS EFFECT ON THE SPALLING OF NIOBIUM OXIDATION FILMS. Country unknown/Code not available: N. p., 1963. Web. doi:10.1016/0022-5088(63)90008-0.
Douglass, D L. THE THERMAL EXPANSION OF NIOBIUM PENTOXIDE AND ITS EFFECT ON THE SPALLING OF NIOBIUM OXIDATION FILMS. Country unknown/Code not available. https://doi.org/10.1016/0022-5088(63)90008-0
Douglass, D L. 1963. "THE THERMAL EXPANSION OF NIOBIUM PENTOXIDE AND ITS EFFECT ON THE SPALLING OF NIOBIUM OXIDATION FILMS". Country unknown/Code not available. https://doi.org/10.1016/0022-5088(63)90008-0.
@article{osti_4708245,
title = {THE THERMAL EXPANSION OF NIOBIUM PENTOXIDE AND ITS EFFECT ON THE SPALLING OF NIOBIUM OXIDATION FILMS},
author = {Douglass, D L},
abstractNote = {The thermal expansion coefficients of stoichiometric and nonstoichiometric niobium pentoxide were determined from 20 to 1000 l C and 20 to 500 l C, respectively, and were found to be significantly smaller than that of niobium metal. The thermal stresses were calculated which are induced during cooling of a coherent oxide-coated niobium plate. In the absence of volume mismatch of oxide and metal it was concluded that thermal stresses due to differences in expansion coefficients should not cause spalling when the oxidized sample is cooled from 600 l C. A more realistic appraisal, which is consistent with experimentally observed spalling, was made by consideration of the very large strains arising from coherency of the voluminous oxide on the more dense metal. The surface layers of the substrate may deform plastically during oxidation at high temperatures, even though appreciable contamination and strengthening has occurred. Upon cooling, however, the added thermal stresses and decreasing plasticity of the contaminated substrate may lead to spalling, the crack initiating in the contaminated metal and propagating into the brittle oxide. (auth)},
doi = {10.1016/0022-5088(63)90008-0},
url = {https://www.osti.gov/biblio/4708245}, journal = {J. Less-Common Metals},
number = ,
volume = Vol: 5,
place = {Country unknown/Code not available},
year = {1963},
month = {4}
}