The preparation using the metal atom technique and properties of nickel microparticles

Abstract

The structural, morphological, and magnetic properties of small nickel particles prepared by the metal atom technique from toluene, SF6, and xenon matrices at 77 K are reported. X-ray scattering and electron microscopy measurements indicate that the smallest particles are obtained from toluene matrices. Particle size depends upon the initial nickel concentration in the toluene matrix, reaching ~ 16-Å average diameter for the highest concentrations studied. The microcrystals prepared from toluene are surrounded by a thin amorphous organic layer, comprising up to 10 wt % of the total sample, due to solvent decomposition on melt-down and subsequent heating to room temperature. The particles are dispersed within larger agglomerates >100 Å in diameter. Microcrystallites obtained from SF6 and xenon are larger. The xenon-prepared nickel is relatively pure, typically ~100 Å in size, and exhibits faceting. Toluene-prepared powders display ferromagnetic behavior with magnetic moments ~40% that of bulk Ni for the largest microcrystallites and paramagnetism for the smallest (metal clusters). The role of matrix solvent in the nucleation and growth of clusters and microcrystallites is also examined and discussed in view of current interest in their catalytic properties. © 1980, American Chemical Society. All rights reserved.