Electrical conduction behavior of cementite, Fe 3 C
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REFERENCES 1. G.R. Edwards, D. L Olson, and D.K. Matlock: Proceedings of Ti6211 Basic Research Program, B.A. MacDonald, O.P. Arora, and B.B. Rath, eds., ONR, Washington, DC, 1982, pp. 345-62. 2. R.E. Lewis and I.L. Caplan: Proceedings of Ti-6211 Basic Research Program, B. A. MacDonald, O. P. Arora, and B. B. Rath, eds., ONR, Washington, DC, 1982, pp. 331-44. 3. D. M. Bowden and E. A. Starke, Jr.: Metall. Trans. A, 1984, vol. 15A, pp. 1687-98. 4. R.E. Lewis: Proceedings of Ti-6211 Basic Research Program, B. A. MacDonald, O. P. Arora, and B. B. Rath, eds., ONR, Washington, DC, 1982, pp. 297-330. 5. D. Hayduk: Master of Science Thesis No. T-2843, Colorado School of Mines, Golden, CO, September 1983. 6. B.K. Damkroger and G.R. Edwards: Colorado School of Mines, Golden, CO, unpublished research, 1983.
Electrical Conduction Behavior of Cementite, FeaC MING-CHUAN LEE and G. SIMKOVICH Several studies 1'2'3 have been made previously to understand the electrical resistivity of cementite; however, no direct measurements have been made on the pure cementite material. Most of the resistivities of cementite were obtained by extrapolation from data for the iron-carbon alloys containing various compositions of carbon, and the measurements were made only at room temperature. Additionally it has been proposed, without electrical conduction behavior available for aid in interpretation, that cementite may be a semiconductor. 4 Therefore, the electrical conduction behavior of cementite has not yet been fully established. The samples utilized in the present work were made by dehydrating and oxidizing ferric nitrate, (Fe(NO3)2 9 9H20), to form very fine particles of hematite (Fe203). These hematite powders were then weighed and analyzed by X-ray diffraction method. A portion of the identified hematite particles ( - 4 0 0 mesh) was then weighed, placed in a Pyrex crucible, and reduced in hydrogen gas at 673 K (450 ~ After reduction was complete ultra high purity methane, at a desired flow rate, was introduced into the flowing hydrogen gas stream. Throughout the entire carbidizing process the activity of carbon was set at 10 by controlling the partial pressure ratio of methane to hydrogen according to the following equations: 5 3Fe + C = Fe3C AG ~ = 26,694 - 24.77T(j) 2H2 + C = CH4 AG ~
- 9 0 , 1 6 5 + 109.5T(j)
[1] [2] [3] [4]
MING-CHUAN LEE, Graduate Student, and G. SIMKOVICH, Professor, are with the Metallurgy Section of the Department of Materials Science and Engineering, The Pennsylvania State University, University Park, PA 16802. Manuscript submitted January 24, 1986. METALLURGICALTRANSACTIONS A
The temperature of carbidization was maintained at 723 K (450 ~ for a time between 14 and 18 hours. Following carbidization, the sample was removed and weighed again. Generally, the weights corresponded to FeaC, 6.67 -+ 0.03 wt pct of carbon. All samples were examined by X-ray diffraction in order to assure that complete reaction to the product had been reached. The identified cementite powders were then pressed into cylinders and sinte
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