DIFFUSION OF IRON INTO SINGLE-CRYSTAL Mg3 (thesis)

MgO single crystals were packed in iron powder and heated in a vacuum at 1150, 1250, and 1350 deg C. Concentration-vs-penetration profiles were determined by using the electron microprobe analyzer. The interdiffusion the range 1 to 22 at. % Fe. At 1150 deg C D =8.1x 10/sup -12/ 0/sup -11/ e/sup 0.173STAFe!; and at 1350 deg C D = 2.40 x 10/sup -11/ e/sup 0.173STAFe!. The apparent activation energy for diffusion increases with the iron concentration. At an iron concentration C = 5 at. %, D = 6.34 x 10/sup -1/ exp (-29,600/RT); at C = 10 D = 4.49 x 10/sup -6/ exp (--32,900/RT); at C = 15 D = 5.04 x 10/sup -4/; exp (- 37,700/ RT); and at C = 20 D = 8.40 x 10/sup -4/ exp (-43,500/RT). (auth) Photomicrographic techniques have been used to examine the microstructure of the many grades of formed carbon and graphite developed under Contract No. AF33(616)- 6915. These techniques have aided in the study of these grades and in predicting or understanding their behavior in various applications. Photomicrography has allowed identification of various materials such as cokes, graphites, pitch, etc., within the formed article and has permitted a study ofmore » the distribution of these materials. The effect of impregnation of the graphite with pitches and resins can be more clearly defined by careful photomicrographic examination. Standard metallographic equipment can be used for such studies but preparation of the carbon and graphite requires special techniques. Mounting methods to prevent smearing or chipping of the samples during preparation and to obtain very highly polished surfaces are discussed. Also described are various techniques of lighting to aid in revealing and interpreting microstructure, and the different types of photographic film, plates, developers, and printing papers required for showing pertinent details in the final photomicrograph. (auth)« less