Document a92Q3BmyaQrYqwMGp6eawXXB

10/108/2001 15:58 312-996-7822 SCIENCE LIBRARY DEFORMATION OF CHRVSOT1LE ASBESTOS 385 PAGE 05 t ' T I I I .. II il t I II tI* II II * |M on ->( -rw Iv V rf '' VV 'N '\ / s Fic. 1- Hhntnlkm of ta* zeal and reciprocal (nice of defect-free chrysolite fiber (i) and (ti) idealized a* tenet of coocentnc cylinder*- The actual structure u a defected spiral sheet (Yada, 19(7). The reciprocal lattice of the ideal fiber is then a series of equispaced concentric ring* along the a* axis, a* in the Zkl layer, when these rings intersect, the Ewaid sphere (BS) spots ought to be produced a* shown on the -2X1 layer line. However, streaks are observed (Yada, 19(7), arising proba bly from the spiral shape of the fiber defects and strains formed during the scrolling process. When e fiber bundle (fiber* of different orieotatioo*) is imaged, the layer line* are smeared out, yielding n Typical "arcuate" pattern as In Fig- 3b. growth of the crystal. The influence of these faults on the diffraction patterns and their influence on deformation needs further study- When bundles of Gbers are involved, the streaks are replaced by arcs (Pigs. 2iv and 3b), showing a strong tendency toward a texture and yielding the typical "arcuate" patterns observed by several researchers (e.g., Rohl e( al., 1976), The dark-fleld image obtained by imaging any part of the arc, as shown in Figs. 1 and 3b, should yield uniform intensity, if the crystal is homogeneous. This is the case to be expected only in the case of the undeformed fibers--and is consistent with the experimental observations in Figs. 3a and 3b. RESULTS Bright- and dark-field images of naturally occurring chrysotile (A) are shown in Fig. 3. The dark field is obtained by imaging a portion of the diffracted intensity, as explained above. The result is a uniform contrast, as would be expected from an undeformed crystalThe striking feature of the dark-field images is the great intensity along the hollow canals and this needs fiuther investigation. The intensity difference cannot be explained on the basis of differences in absorption alone; it appears that some