Document Details
PURL
(2 mb)
Title:
An Improved Method for Determining Activation Energies of Relaxation Processes
Author(s):
Dienes, G. J. [North American Aviation, Inc., Los Angeles, CA (United States)]; Parkins, W. E. [North American Aviation, Inc., Los Angeles, CA (United States)]
Document Type:
REPORT
Publication Date:
1950 Apr 12
Declassification Date:
1997 Apr 16
Declassification Status:
Declassified
Document Pages:
36 p.
Accession Number:
None
Document Number(s):
NAA-SR-60
Originating Research Org.:
North American Aviation, Inc., Los Angeles, CA (United States)
OpenNet Entry Date:
2017 Oct 25
OpenNet Modified Date:
2023 Nov 06
Description/Abstract:
A general procedure is described for determining the activation energy of an annealing process without using restrictive theoretical assumptions. The theory shows that activation energies are most reliably determined by analyzing experimented relaxation curves obtained at various constant annealing temperatures. The activation energy is directly calculable from the times and temperatures which correspond to any arbitrary, but fixed, fractional anneal. The approximations involved in other techniques are briefly discussed. The theory is applicable to any physical property although written explicitly in terms of electrical resistivity. Experimental verification, based on electrical resistivity annealing of irradiated graphite, is presented. Comparison of two samples of different irradiation exposure shows that the more heavily damaged material is characterized by higher activation energies for annealing carried out in identical temperature regions. The analytical method is applied to results of elastic modulus and electric resistivity annealing measurements given in an earlier report. Anomalies in the early results are clarified.