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Radiation damage studies on natural rock salt from various geological localities of interest to the radioactive waste disposal program

Description: As part of a program to investigate radiation damage in geological materials of interest to the radioactive waste disposal program, radiation damage, particularly radiation induced sodium metal colloid formation, has been studied in 14 natural rock salt samples. All measurements were made with equipment for making optical absorption and other measurements on samples, in a temperature controlled irradiation chamber, during and after 0.5 to 3.0 MeV electron irradiation. Samples were chosen for pr… more
Date: January 1, 1981
Creator: Levy, P.W.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Radiation-induced sodium-metal-colloid formation in natural rock salt from different geological localities

Description: Radiation damage has been studied in natural rock salt from various localities, including potential repository sites. In the 100 to 300 C range the damage consists of point defects, primarily F-centers, and colloidal metal sodium particles. With increasing dose the F-centers grow to a saturation level, reached at 10/sup 7/ to 10/sup 8/ rad, that decreases with increasing temperature to a negligible level at 300 C. Colloid concentration vs. irradiation-time curves follow nucleation and growth cu… more
Date: January 1, 1981
Creator: Loman, J. M.; Levy, P. W. & Swyler, K. J.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Vacancy and interstitial loops in irradiated copper

Description: Significant advances have been made in diffuse scattering studies of irradiation induced dislocation loops in metals. Numerical calculational procedures have been developed that provide accurate diffuse scattering cross sections for vacancy and interstitial loops, and these cross sections have been used in conjunction with x-ray diffuse scattering studies of neutron and ion irradiated copper. Size distributions and concentrations have been obtained for both vacancy and interstitial loops and th… more
Date: November 1, 1981
Creator: Larson, B.C. & Young, F.W. Jr.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Vacancy behavior in a compressed fcc Lennard-Jones crystal

Description: This computer experiment study concerns the determination of the stable vacancy configuration in a compressed fcc Lennard-Jones crystal and the migration of this defect in a compressed crystal. Isotropic and uniaxial compression stress conditions were studied. The isotropic and uniaxial compression magnitudes employed were 0.94 less than or equal to eta less than or equal to 1.5, and 1.0 less than or equal to eta less than or equal to 1.5, respectively. The site-centered vacancy (SCV) was the s… more
Date: December 1, 1981
Creator: Beeler, J.R. Jr.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Atomic defects and diffusion in metals

Description: The tracer self-diffusion data for fcc and refractory bcc metals are briefly reviewed with respect to (i) the available monovacancy formation and migration properties and (ii) the high-temperature diffusion enhancement above that expected for mass transport via atomic exchange with monovacancies. While the atomic-defect mechanism for low-temperature self-diffusion can be reliably attributed to monovacancies, the mechanisms responsible for high-temperature mass transport are not so easily define… more
Date: November 1, 1981
Creator: Siegel, R. W.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Determination of vacancy mechanism for grain boundary self-diffusion by computer simulation

Description: It is currently well established that the fast self-diffusion which occurs along grain boundaries (GBs) in metals must occur by a point defect exchange mechanism. For example, it is known that rapid GB diffusion can transport a net current of atoms along GBs during both sintering and diffusional creep, and that the two species in a binary substitutional alloy diffuse at different rates in GBs. However, it has not been possible to establish firmly whether the defect mechanism involves the exchan… more
Date: June 1, 1981
Creator: Balluffi, R. W.; Kwok, T.; Bristowe, P. D.; Brokman, A.; Ho, P. S. & Yip, S.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Electronic structure and formation energy of a vacancy in aluminum

Description: The electronic structure of a vacancy in Al was calculated self-consistently using norm-conserving ionic pseudopotentials obtained from ab initio atomic calculations. A 27-atom-site supercell containing 1 vacancy and 26 atoms was used to simulate the environment of the vacancy. A vacancy formation energy of 1.5 eV was also calculated (cf. the experimental value of 0.66 eV). The effects of the supercell and the nature of the ionic potential on the resulting electronic structure and formation ene… more
Date: November 1, 1981
Creator: Chakraborty, B. & Siegel, R. W.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Molecular dynamics simulation of grain-boundary diffusion of vacancies in bcc iron

Description: The jumping of vacancies in a bcc iron ..sigma.. = 5 tilt boundary was simulated by computer molecular dynamics. The data yielded a reasonable value of the activation energy for migration and showed that the jump processes are highly structure-dependent. The use of a temperature dependent transition probability matrix to describe the diffusion of the vacancies in the grain boundary is suggested. Formation of one type of boundary interstitial was observed which was found to be immobile.
Date: June 1, 1981
Creator: Kwok, T.; Ho, P. S.; Yip, S.; Balluffi, R. W.; Bristowe, P. D. & Brokman, A.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Quantitative comparison of the void distribution in a. beta. '-phase Ni-Al-In alloy using x-ray small-angle scattering and transmission-electron microscopy. [Ni-51. 2 at. % Al-2. 6 at. % In]

Description: Small-angle scattering is a rather mature discipline which can yield valuable information on the size, amount, and distribution of inhomogeneities encountered in materials-science research. Methods have been publisheed which permit one to extend the standard analysis of data from a small-angle-scattering experiment to include determination of the distribution of particle sizes. This extended analysis has been carried out for voids in a ..beta..'-phase Ni-Al-In alloy, and, in order to assess the… more
Date: November 1, 1981
Creator: Epperson, J. E.; Loomis, B. A. & Lin, J. S.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Positron prevacancy effects in pure annealed metals

Description: The low-temperature prevacancy effects sometimes observed with positrons in well-annealed high-purity metals are discussed. It is shown that these effects are not experimental artifacts, but are due to trapping of the positrons. It is suggested that dislocations are responsible for these trapping effects. 46 references, 5 figures.
Date: June 1, 1981
Creator: Smedskjaer, L.C.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Computer Simulation Study of the Structure of Vacancies in Grain Boundaries

Description: The structure of vacancies in grain boundaries has been investigated by computer molecular statics employing pairwise potentials. In order to gain an impression of the vacancy structures which may occur generally, a number of variables was investigated including: metal type, boundary type, degree of lattice coincidence and choice of boundary site. In all cases the vacancies remained as distinguishable point defects in the relatively irregular boundary structures. However, it was found that the … more
Date: January 1, 1981
Creator: Brokman, A.; Bristowe, P.D. & Balluffi, R.W.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Theory of Moessbauer line broadening due to diffusion

Description: We have calculated the line broadening of the Moessbauer line due to diffusion of Moessbauer atoms via single vacanices. We take into account the perturbation of vacancy jumps in the neighbourhood of an impurity Moessbauer atom (e.g. Fe in Al) using the 5-frequency model. The anisotropy of the line width is given by the Fourier transform of the final distribution of a Moessbauer atom after an encounter with a vacancy. This distribution is calculated by Monte Carlo computer simulation. 3 figures… more
Date: December 1, 1981
Creator: Schroeder, K.; Wolf, D. & Dederichs, P. H.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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