Date of Award

9-1989

Degree Type

Thesis

Degree Name

Doctor of Philosophy (PhD)

Department

Physics

Supervisor

Professor E.A. Ballik

Abstract

The magnetic-alignment behaviour of asbestos fibers suspended in water was studied. As the magnetic field rotates, with the lag increasing as the rotation rate increases. A theoretical model describing fiber behaviour was developed. Experiments measuring the phase lag of individual fibers, experiencing torques to the order of 10^18 Newton-meters were in excellent agreement with the model. For an unknown fiber the phase lag measurement will give the ratio of the length to radius of the fiber. For a known fiber, the cross-sectional size and shape can be determined.

This research was undertaken with the intention of laying down the groundwork from which an automatic instrument for monitoring asbestos exposure could be made. Initial investigations involved filtering a liquid dispersion in a one Tesla magnetic-field. The filter contained permanently aligned fibers. The fiber was made transparent and scattered-light measurements were made relative to the initial magnetic field direction were made. Subsequent research focussed on mesuring light scattered by fibers suspended in water while the fibers followed a rotating magnetic-field. The latter technique proved far more sensitive, being able to detect fiber concentrations of the order of one million fibers per liter with relatively simple equipment. On a mass basis, this sensitivity corresponds to one part in 10^10. The method did not have the problems associated with the filter itself. Equally important, there is the potential to obtain fiber size information.


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