Date of Award

Spring 1992

Degree Type

Thesis - Restricted

Degree Name

Master of Science (MS)

Department

Mechanical and Industrial Engineering

First Advisor

Cartz, L.

Second Advisor

Karioris, F. G.

Abstract

Natural phlogopite micas may contain occluded water which gives rise to anomalous reversible thermal expansion behavior at high temperatures. Expansions as much as 200% at 600°C, are observed, when water vapor bubbles form within the mica and expand reversibly with temperature. A thermal actuator can be based on this property but it is necessary to have micas with known amounts of occluded gases or vaporizing liquids. One method of achieving this is by the implantation of gaseous ions in a pure mica specimen of normal thermal expansion. Mica-gas composites have been prepared of controlled composition by implanting helium, and other noble gases into a muscovite mica at 1-2 MeV and also at 100-200 keV energies. Helium has been implanted at room temperature so as to provide a distribution of the gas (100 ppm) throughout muscovite mica by using a range of energies of 0.6, 0.9, 1.2 and 1.5 MeV in specimens of thickness 10 and 5 μm. The muscovite mica-helium gas composite has an enhanced thermal expansion 10-4oC-1 which is about ten times greater than that of the original muscovite at 600°C along the [0001] direction. The measurements have been carried out by a thermomechanical analyzer where the applied stress on the dilatometer probe can be varied. The thermal expansion of the implanted muscovite mica decreases as the probe stress increases. There is no such dependence with pressure for the unimplanted muscovite mica. The thermal expansion behavior of the helium implanted muscovite mica does depend on the probe pressure and the mica-gas composite has a temperature behavior very similar to that of a gas, and can be compared to the behavior of natural phlogopite above -1500C. Transmission electron microscope (TEM) observations of the implanted muscovite mica at room temperature show typical lenticular flaws. Heating studies using a high temperature stage in a TEM show that the size of these lenticular flaws increases and decreases as temperature increases and decreases, respectively. Upon heat treatment of implanted specimens, the shape and size of these induced lenticular flaws become somewhat irregular and extended. These lenticular flaws are believed to be gas bubbles induced by the implanted ions since no such features can be found in unimplanted samples. Gas bubbles also can be found in mica specimens implanted with neon, argon and xenon, and the size of the bubble varies with the diameter of the gas ions-. Rutherford Back Scattering (RBS) shows that the amount of Xe implanted in muscovite does not change after six months of implantation. The transmission electron microscopy studies suggest that these noble gases are implanted along (0001) cleavage planes.

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