The diffusion coefficients for ultrathin chrysotile fibers

The diffusion coefficient for chrysotile fibers was determined from measurements of the total penetration and the size distributions before and after a diffusion battery. A protocol was developed in which the fibers were produced by nebulizing a methanol suspension of chrysotile fibers. The fibers were collected on carbon-coated nucleopore filters. After dissolving the filter substrata, the fibers were verified as chrysotile and sized. Experimental variables were flow rate and total pressure. The fiber diffusion coefficients as a function of fiber length and diameter were obtained by first obtaining the size dependent penetrations, then calculating the diffusion coefficient from the Gormley-Kennedy equation. Four experiments were analyzed in depth. Although two of the experiments were at reduced pressure, the corrections due to increased Knudsen number were less than the variation among the experiments. The most significant experimental results were that the measured diffusion coeffici ents were larger than calculations from existing theory. Also, thicker fibers had surprisingly large diffusion coefficients. Theoretical calculations indicated that models based on hypothetical spherical particles gave similar results when either the hybrid, Asgharian-Yu-Gradon, or equivalent volume diameters were used.