Masters Theses

Abstract

"The transport of heat in solids is attributed to the combined effect of the quantized vibrations of lattice points, or phonons, and the flow of valence electrons. In dielectric solids, the thermal conductivity is due almost entirely to phonons, while in metals the latter method preponderates. Scattering processes in dielectric solids, giving rise to thermal resistance, also serve to limit the thermal conductivity. Scattering results from vacancies, dislocations, interstitial atoms and phonon interaction. Crystal boundaries also function as scattering points and in crystals of small dimensions, this process is the most pronounced conductivity-limiting factor. At low temperatures the thermal resistance of an ideal crystal is due almost entirely to boundary scattering while at high temperatures anharmonic coupling is the primary limiting factor. As the temperature increases, boundary scattering becomes less pronounced but anharmonic coupling increases. At some median temperature the conductivity is a maximum….

Considerable experimental work has been done in the past to determine the thermal conductivity of various alkali halides below the boiling point of water. Values determined by early experimenters differed widely, but these discrepancies are attributed to various major defects in the samples used. Measurements at the Missouri School of Mines and Metallurgy of the conductivity of sodium chloride above this temperature and to approximately 600°K indicate a relationship proportional to l/T1.3. Therefore, it appears that if theory is to be substantiated by experimental determinations, the conductivity of a single specimen must be examined to the maximum attainable temperature, i.e. the melting point of the substance.

Equipment built by Weisbrod and improved by Brown and Ohlsen was available at the beginning of the investigation. Its design utilizes an absolute steady state method of measurement. Two nearly perfect cylindrical crystals of potassium chloride were used in the experiment, one approximately half the thickness of the other. The purpose of this investigation was to improve the operation of existing equipment and to extend the experimental data available on the conductivity of potassium chloride"--Introduction, pages 1-3.

Advisor(s)

Bessey, William H.

Department(s)

Physics

Degree Name

M.S. in Physics

Sponsor(s)

Research Corporation

Publisher

Missouri School of Mines and Metallurgy

Publication Date

1956

Pagination

v, 33 pages

Note about bibliography

Includes bibliographical references (page 32).

Rights

© 1956 Wendell D. Miller, All rights reserved.

Document Type

Thesis - Open Access

File Type

text

Language

English

Subject Headings

Potassium chloride -- Thermal conductivityMaterials at high temperaturesScientific apparatus and instruments -- Testing

Thesis Number

T 1128

Print OCLC #

5920263

Electronic OCLC #

947642906

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