CRYSTALLOGRAPHY AND SOLIDIFICATION BEHAVIOR OF NANOMETRIC PB PARTICLES EMBEDDED IN ICOSAHEDRAL AND DECAGONAL QUASI-CRYSTALLINE MATRIX

Solidification behaviour of lead particles embedded in icosahedral and decagonal quasicrystalline matrix has been studied. Differential scan ning calorimetry traces for the icosahedral matrix show a sharp lead m elting peak but a very Aat solidification exotherm with several peaks, while lead in the decagonal matrix shows sharp melting and solidifica tion peaks. Transmission electron microscopy shows that lead particles are Faceted on major planes of the matrix. The solidified lead partic les show well defined orientation relationships with the matrix. Three relationships were observed in the case of the icosahedral matrix in all of which there is a tendency for the lead {022} planes to align wi th icosahedral {211111} and {221001} planes. In the decagonal matrix a single relationship is observed. The calculated contact angles for nu cleation show that lead solidification on quasicrystalline surfaces oc cur at higher undercoolings for the same contact angles, as compared t o solidification on crystals. (C) 1998 Acta Metallurgica Inc. Publishe d by Elsevier Science Ltd. All rights reserved.