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THE EFFECT OF APPLIED STRESS ON THE GRAPHITIZATION OF PYROLYTIC GRAPHITE

Abstract

Metallographic and x-ray diffraction studies were made of the effect of applied stress at high temperature on the structure of pyrolytic graphite (PG). The dominant factor was whether the PG was above or below its graphitization temperature, which, in turn, was not strongly dependent on applied stress. Below the graphitization temperature, the PG showed a high proportion of disordered layers (0.9), a fairly large mean tilt angle (20 deg ) and a small crystailite size (La --150 A). Fracture occurred at low stress and strain and the materiai exhibited a high apparent Young's modulus ( approximates 4 x 10/sup 6/ psi). Above the graphitization temperature, graphitization was considerably enhanced by strain up to about 8%. The disorder parameter was decreased from a zero strain value of 0.3 to 0.l5 with strain, the mean tilt angle was decreased to 4 deg , and a fivefold increase in crystallite size occurred. When the strainenhanced graphitization was complete, the material exhibited a low apparent modulus ( approximates 0.5 x 10/sup 6/ psi) and large plastic strains (>100%) for a constant stress ( approximates 55 ksi). Graphitization was shown to be a spontaneous process that is promoted by breaking cross-links thermally, and the process  More>>
Publication Date:
Jun 15, 1963
Product Type:
Conference
Report Number:
CONF-73-3; AED-Conf-63-061-7
Reference Number:
NSA-17-032649
Resource Relation:
Conference: 6th Biennial Conference on Carbon, Pittsburgh, PA (United States), 17-21 Jun 1963
Subject:
METALS, CERAMICS, AND OTHER MATERIALS; CONFERENCE; DEFECTS; DEFORMATION; DIFFRACTION; FAILURES; GRAIN SIZE; GRAPHITE; GRAPHITIZATION; HIGH TEMPERATURE; LATTICES; METALLOGRAPHY; PYROLYSIS; STRESSES; TEMPERATURE; TENSILE PROPERTIES; X RADIATION
OSTI ID:
4875462
Research Organizations:
Lockheed Missiles and Space Co., Palo Alto, CA (United States)
Country of Origin:
United States
Language:
English
Submitting Site:
DTIE
Size:
Pages: 30
Announcement Date:
Dec 31, 1963

Citation Formats

Bragg, R H, Crooks, D D, Fenn, Jr, R W, and Hammond, M L. THE EFFECT OF APPLIED STRESS ON THE GRAPHITIZATION OF PYROLYTIC GRAPHITE. United States: N. p., 1963. Web.
Bragg, R H, Crooks, D D, Fenn, Jr, R W, & Hammond, M L. THE EFFECT OF APPLIED STRESS ON THE GRAPHITIZATION OF PYROLYTIC GRAPHITE. United States.
Bragg, R H, Crooks, D D, Fenn, Jr, R W, and Hammond, M L. 1963. "THE EFFECT OF APPLIED STRESS ON THE GRAPHITIZATION OF PYROLYTIC GRAPHITE." United States.
@misc{etde_4875462,
title = {THE EFFECT OF APPLIED STRESS ON THE GRAPHITIZATION OF PYROLYTIC GRAPHITE}
author = {Bragg, R H, Crooks, D D, Fenn, Jr, R W, and Hammond, M L}
abstractNote = {Metallographic and x-ray diffraction studies were made of the effect of applied stress at high temperature on the structure of pyrolytic graphite (PG). The dominant factor was whether the PG was above or below its graphitization temperature, which, in turn, was not strongly dependent on applied stress. Below the graphitization temperature, the PG showed a high proportion of disordered layers (0.9), a fairly large mean tilt angle (20 deg ) and a small crystailite size (La --150 A). Fracture occurred at low stress and strain and the materiai exhibited a high apparent Young's modulus ( approximates 4 x 10/sup 6/ psi). Above the graphitization temperature, graphitization was considerably enhanced by strain up to about 8%. The disorder parameter was decreased from a zero strain value of 0.3 to 0.l5 with strain, the mean tilt angle was decreased to 4 deg , and a fivefold increase in crystallite size occurred. When the strainenhanced graphitization was complete, the material exhibited a low apparent modulus ( approximates 0.5 x 10/sup 6/ psi) and large plastic strains (>100%) for a constant stress ( approximates 55 ksi). Graphitization was shown to be a spontaneous process that is promoted by breaking cross-links thermally, and the process is furthered by chemical attack and plastic strain. (auth)}
place = {United States}
year = {1963}
month = {Jun}
}