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Structural characterizaiton and gas reactions of small metal particles by high-resolution, in-situ TEM and TEDThe existing in-situ transmission electron microscopy (TEM) facility was improved by adding a separately pumped mini-specimen chamber. The chamber contains wire-evaporation sources for three metals and a specimen heater for moderate substrate temperatures. A sample introduction device was constructed, installed, and tested, facilitating rapid introduction of a specimen into the mini-chamber while maintaining the background pressure in that chamber in the 10(-9) millibar range. Small particles and clusters of Pd, grown by deposition from the vapor phase in an in-situ TEM facility on amorphous and crystalline support films of alumina and on ultra-thin carbon films, were analyzed by conventional high-resolution TEM and image analysis in terms of detectability, number density, and size distribution. The smallest particles that could be detected and counted contained no more than 6 atoms; size determinations could be made for particles 1 nm in diameter. The influence of various oxygen plasma treatments, annealing treatments, and of increasing the substrate temperature during deposition was investigated. The TEM technique was employed to demonstrate that under otherwise identica l conditions the lattice parameter of Pd particles in the 1 to 2 nm size range and supported in random orientation on ex-situ prepared mica films is expanded by some 3% when compared to 5 nm size particles. It is believed that this expansion is neither a small-particle diffraction effect nor due to pseudomorphism, but that it is due to a annealing-induced transformation of the small as-deposited particles with predominantly composite crystal structures into larger particles with true f.c.c. structure and thus inherently smaller lattice parameter.
Document ID
19860020486
Acquisition Source
Legacy CDMS
Document Type
Contractor Report (CR)
Date Acquired
September 5, 2013
Publication Date
January 1, 1984
Subject Category
Metallic Materials
Report/Patent Number
NAS 1.26:176905
NASA-CR-176905
Accession Number
86N29958
Funding Number(s)
CONTRACT_GRANT: NCC2-283
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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