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DIFFUSION IN URANIUM, ITS ALLOYS, AND COMPOUNDS

Description: ABS>A review of laboratory diffusion studies on uranium and its compounds and alloys is presented. Included are results and analysis of studies on diffusion in single-phase and in multiphase U alloys, diffusion of gases in U, and diffusion in UO/sub 2/. (J.R.D.)
Date: May 1, 1961
Creator: Rothman, S.J.
Partner: UNT Libraries Government Documents Department

THE DIFFUSION OF CHROMIUM IN GAMMA URANIUM. Partial Report-Metallurgy Program 4.1.27

Description: The diffusion of tracer amounts of chromium in gamma uranium was studied by the radioactive tracer-sectioning method. The temperature dependence of the diffusion coefficient D is given by D = 1.98 x 10/sup -3/ exp(--2l,800/RT)cm/sup 2// sec, in poor agreement with the data of Mosse, Levy, and Adda. Possible reasons for the discrepancy are discussed, and it is concluded that the present data are to be preferred as a basis for theoretical studies of the diffusion of tracers in gamma uranium. The difference between the activation energy and that for self-diffusion is also discussed; no conclusions are reached. (auth)
Date: June 1, 1961
Creator: Rothman, S.J.
Partner: UNT Libraries Government Documents Department

The Diffusion of Gold in Gamma Uranium

Description: The diffusion coefficient of tracer amounts of Au/sup 198/ in gamma U is described by an Arrhenius-type equation: D = 4.86 x 10 cm/sup -3/sec exp(-30,400 cal/mol/RT). The values of D/sub 0/ and the activation energy are close to those for self-diffusion in gamma U, indicating that the low activation energy for self- diffusion is due to a general weakness of the lattice rather than to easy compressibility of the U atom. (auth)
Date: May 1, 1960
Creator: Rothman, S. J.
Partner: UNT Libraries Government Documents Department

Radiation-enhanced diffusion in metals and alloys

Description: Some phenomena that involves diffusion during irradiation include fission-product redistribution in reactor fuels, defect clustering in CTR walls or fast-reactor cladding, smearing-out of gradients in ion-implanted semiconductors, and microstructure development in a HVEM. This paper is a review of the basics of radiation-enhanced diffusion (REM). The present status of REM today is somewhat the same as diffusion in the 1940's, and recommendations are made for further work. 105 references. (DLC)
Date: January 1, 1975
Creator: Lam, N.Q. & Rothman, S.J.
Partner: UNT Libraries Government Documents Department

Diffusion studies in amorphous NiZr alloys

Description: Tracer impurity and self diffusion measurements have been made on amorphous (a-) NiZr alloys using radioactive tracer, Secondary Ion Mass Spectrometry and Rutherford backscattering techniques. The temperature dependence of diffusion in a-NiZr can be represented in the form D = D/sub 0/exp(-Q/kT), with no structural relaxation effects being observed. The mobility of an atom in a-NiZr increased dramatically with decreasing atomic radius of the diffusing atom and also with decreasing Ni content for Ni concentrations below approx. =40 at. %. These diffusion characteristics in a-NiZr are remarkably similar to those in ..cap alpha..-Zr and ..cap alpha..-Ti. These mechanisms assume that Zr and Ti provide a close packed structure, either crystalline or amorphous, through which small atoms diffuse by an interstitial mechanism and large atoms diffuse by a vacancy mechanism. 12 refs., 2 figs., 2 tabs.
Date: June 1, 1987
Creator: Hahn, H.; Averback, R.S.; Hoshino, K. & Rothman, S.J.
Partner: UNT Libraries Government Documents Department

Tracer diffusion of /sup 60/Co and /sup 63/Ni in amorphous NiZr alloy

Description: Tracer diffusion of /sup 60/Co and /sup 63/Ni in equiatomic amorphous NiZr alloy in the temperature range between 486 and 641/sup 0/K can be described by: D/sub Co/sup */ = 3.7 x 10/sup -7/ exp(-(135 +- 14) kJ mole/sup -1//RT) m/sup 2//sec and D/sub Ni//sup */ = 1.7 x 10/sup -7/ exp(-(140 +- 9) kJ mole/sup -1//RT) m/sup 2//sec. The values of D/sub Ni//sup */ are in reasonable agreement with those measured by the Rutherford backscattering technique. The measured diffusivities were independent of time, indicating that no relaxation took place during diffusion. 27 refs., 2 tabs.
Date: January 1, 1987
Creator: Hoshino, K.; Averback, R.S.; Hahn, H. & Rothman, S.J.
Partner: UNT Libraries Government Documents Department

Oxygen diffusion in cuprate superconductors

Description: Superconducting properties of the cuprate superconductors depend on the oxygen content of the material; the diffusion of oxygen is thus an important process in the fabrication and application of these materials. This article reviews studies of the diffusion of oxygen in La{sub 2}{sub {minus}}{sub {times}}Sr{sub {times}}CuO{sub 4}, YBa{sub 2}Cu{sub 3}O{sub 7}{sub {minus}}{delta}, YBa{sub 2}Cu{sub 4}O{sub 8}, and the Bi{sub 2}Sr{sub 2}Ca{sub n}{sub {minus}}{sub 1}Cu{sub n}O{sub 2}{sub +}{sub 4} (n = 1, and 2) superconductors, and attempt to elucidate the atomic mechanisms responsible.
Date: January 1, 1995
Creator: Routbort, J.L. & Rothman, S.J.
Partner: UNT Libraries Government Documents Department

Oxygen diffusion in high- Tc superconductors

Description: The cuprate superconductors are fascinating not only because of their technical promise, but also because of their structures, especially the anisotropy of the crystal lattice. There are some structural similarities among these compounds, but also significant differences. Measurements of the oxygen tracer diffusion coefficients have been carried out as a function of temperature, oxygen partial pressure, crystal orientation, and doping in the La-Sr-Cu-0, Y-Ba-Cu-0, and Bi-Sr-Ca-Cu-0 systems. These measurements have revealed a variety of defect mechanisms operating in these compounds; the exact nature of the mechanism depends on the details of the structure.
Date: July 1, 1992
Creator: Rothman, S.J. & Routbort, J.L.
Partner: UNT Libraries Government Documents Department

Self-Diffusion in Beta Uranium. Partial Report--Metallurgy Division Program 4.1.2

Description: The self-diffusion coefficient of U decreased from 3 x 10/sup -9/ cm/sup 2//sec at 785 deg C to 2.1 x 10/sup -11/ cm/sup 2//sec at 760 deg C. At temperatares high in the beta phase, the plots of log C vs. X/sup 2/ are curved, indicating that self-diffusion in beta U does not take place by isotropic volume diffusion alone. (auth)
Date: July 1, 1960
Creator: Rothman, S. J.; Gray, J., Jr.; Hughes, J. P. & Harkness, A. L.
Partner: UNT Libraries Government Documents Department

SELF-DIFFUSION IN GAMMA URANIUM

Description: The self-diffusion coefficient or uranium was measured at four temperatures in the gamma phase. The data are fitted by an Arrhenius-tyoe equation D = 2.33 x well with previously reported results. The value of D/sub o/ is lower than that predicted by Zener's theory, and the activation energy is much less than the value expected from various empirical codelations. (auth)
Date: July 1, 1959
Creator: Rothman, S.J.; Lloyd, L.T.; Weil, R. & Harkness, A.L.
Partner: UNT Libraries Government Documents Department

Anisotropy of oxygen tracer diffusion in YBa sub 2 Cu sub 3 O sub 7-. delta. single crystals

Description: The crystal structure of YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} strongly suggests that the diffusion of oxygen in this material will be highly anisotropic, with diffusion in the ab plane being much faster than diffusion parallel to the c axis, and this has been assumed in most analyses of diffusion in YBa{sub 2}Cu{sub 3}O{sub 7-{delta}}. The present data confirm this hypothesis; the diffusion coefficient in the ab plane is several orders of magnitude greater than the diffusion coefficient along the c axis. Some interesting artifacts of the measurement, due to this strong anisotropy, are also revealed. Oxygen exchange in polycrystalline samples of YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} is discussed in terms of these results. 15 refs., 9 figs.
Date: September 1, 1989
Creator: Rothman, S.J.; Routbort, J.L.; Liu, J.-Z.; Downey, J.W.; Thompson, L.J.; Fang, Y. et al.
Partner: UNT Libraries Government Documents Department