Size classification of carbon fiber aerosols

Abstract

This report describes an experimental study to classify fiberlike particles by length based on their electrical properties. Carbon fibers with monodisperse diameters and polydisperse lengths were passed through a unipolar charger. The charged fibers were then segregated in an electrical mobility analyzer based on their mobilities. They were collected on Mylar segments, which were placed at different precipitating lengths on a central rod of the analyzer. The results showed that carbon fibers with a narrow length range attached themselves to many of the Mylar segments on the rod, demonstrating the fibers with monodisperse lengths can be classified by using this technique. In addition, the results indicated that the longer the precipitating length of the segment, the shorter the length of the fibers collected. The effects of flow rate, charging time, and analyzer voltage on fiber classification were also investigated. The results showed that, at a fixed precipitating length, the longer fibers were collected under a higher flow rate or a lower analyzer voltage. However, no effect of charging time was observed. Further analysis illustrated that all data obtained from the various operating conditions could be consolidated by a function relating electrical mobility to fiber length. This relationship was then used to estimate the charge distribution of carbon fibers in a unipolar charging mechanism. Based on our results, the number of charges on a carbon fiber increases monotonically with the aspect ratio of the fiber. © 1993 Elsevier Sciencc Publishing Co., Inc.