Calorimetric evidence for the micro-quasicrystalline structure of 'amorphous' Al/transition metal alloys
Journal
Nature
Journal Volume
336
Journal Issue
6197
Pages
366-368
Date Issued
1988
Author(s)
Abstract
The idea that a material exhibiting broad diffraction halos does not have a characteristic amorphous structure but is just an assembly of randomly orientated microcrystals is a remarkably resilient one. Invariably it is resurrected when a new type of amorphous material is discovered, only to be put aside in most cases in favour of a truly amorphous structure (one without any lattice periodicity). For fused silica and the amorphous elemental semiconductors, this structure is the continuous random network1; for the amorphous metals it is a dense random packing of hard spheres (see ref. 2; the strong short-range order in amorphous metals is explicitly taken into account in the 'stereochemically defined9 models described in ref. 3). Nonetheless, truly microcrys-talline materials do exist, and their diffraction patterns consist of broadened powder peaks4. Here we show that these microcrystalline materials can be identified unambiguously by the characteristic isothermal calorimetric signal associated with their transformation to a large-grained material, and we use this test to demonstrate that two sputtered "amorphous' aluminum/transition metal alloys have a micro-quasicrystalline structure. © 1988 Nature Publishing Group.
Other Subjects
Calorimetry--Applications;Crystals--Microstructure;Aluminum Transition Metal Alloys;Exothermic Transformations;Isothermal Crystallization Kinetics;Microcrystalline Materials;Aluminum and Alloys
Type
journal article