Grain‐Boundary Diffusion in MgO

Wuensch, B. J.; Vasilos, T.

doi:10.1111/j.1151-2916.1964.tb15656.x

Cited by 48 publications

(4 citation statements)

References 13 publications

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“…No evidence for grain-boundary diffusion in bicrystals of MgO was observed above 1300°C. 4 The precise temperature at which solid solution is complete in a given specimen, however, depends on the type and amount of precipitate in the material.…”

Section: August 1966mentioning

confidence: 99%

Origin of Grain-Boundary Diffusion in MgO

Wuensch

Vasilos

1966

J American Ceramic Society

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Preferential diffusion of Ni2+ and Co2+ along grain boundaries was observed in certain bicrystals of MgO. This enhancement is attributed to impurity segregation at the boundary. The identified impurities responsible for the effect are the principal impurities in the single-crystal MgO: Ca, Si, and Fe. No enhancement was observed in any bicrystal prepared above 130O0C, a temperature similar to that at which studies of the mechanical properties of MgO have implied a reabsorption of impurity precipitates into solid solution. It is concluded that enhanced grainboundary diffusion of cations in MgO is an extrinsic, rather than an intrinsic, property of the boundary.* Received from the Norton Company, Worcester, Mass.soon discovered, however, that the effect was extrinsic. The origin of the effect could successfully be interpreted through examination of the distribution of impurities in the specimens. 13-89 (1961).Ways of describing and defining progress of fining or the standard to be achieved are discussed. Methods of measurement are also discussed. Published quantitative data which can be used to test proposed hypotheses or theories are reviewed. Finally, processes known to be important in eliminating gas bubbles from liquids, namely rise and bursting at the surface, coalescence, and growth or dissolving are discussed.

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Section: August 1966mentioning

confidence: 99%

Origin of Grain-Boundary Diffusion in MgO

Wuensch

Vasilos

1966

J American Ceramic Society

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“…Recent investigations have shown that cation diffusion can be enhanced a t grain boundaries,21s22 and the region oC a grain that may be affected by a boundary may be as large as I O2 to lo4 A. [23][24][25][26] For submicron particles, such as were used in this investigation, a very large volume fraction of a grain may be affected by a boundary. One of the possible reasons Cor the higher diffusion coefficients observed in this study could be the enhancement of cation diffusion by an increase in the boundary layer of fine grains.…”

Section: (3) Pretreated Powdermentioning

confidence: 99%

Final Stage Densification in Vacuum Hot-Pressing of Alumina

Rossi

Fulrath

1965

J American Ceramic Society

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Temperature and oxygen pressure limits on the oxidation of molybdenum in MoSiz and MogSi3 are a consequence of thermodynamic and diffusion considerations for the pertinent systems and were derived independently of observations of nonprotective oxidation behavior. For a given oxygen pressure, molybdenum can oxidize only at temperatures below these limits. Since nonprotective oxidation is expected to occur exclusively at temperatures and pressures where molybdenum oxidizes, the theoretical and experimental results zre in reasonable agreement. Molybdenum oxidation is a necessary condition for nonprotective oxidation in both cases arid i t is a sufficient condition for nonprotective oxidation of Mo&.

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“…In alkali halides and oxides, however, there are indications that the high diffusivity paths are of considerable dimensions. [6][7][8] In these crystals higherorder approximations have to be taken into account. In the present paper higher-order approximations for the solution of the grain-boundary diffusion problem for an instantaneous source are presented.…”

Section: Introductionmentioning

confidence: 99%

Diffusion in Wide Grain Boundaries

Mimkes

Wuttig

1970

Journal of Applied Physics

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The rigorous solution of the grain-boundary diffusion problem has been approximated by a series expansion method. The calculations show that higher-order terms may be neglected in the bulk adjacent to the grain boundary. Thus, in this region Whipple's and Suzuoka's solutions represent a close approximation to the problem. Inside the grain boundary, however, higher-order approximations have to be taken into aCCount. These approximations gain importance in the case of wide grain boundaries. The solutions obtained for an instantaneous source have been fitted to available grain-boundary diffusion data of NiH in MgO at 1200°C. Numerical calculations give for the bulk diffusion coefficient D=2.9XIo-12 cm 2 sec l , the ratio of diffusion coefficient A = 1.5 and for the grain-boundary width a = 75 p..

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Grain‐Boundary Diffusion in MgO

Cited by 48 publications

References 13 publications

Origin of Grain-Boundary Diffusion in MgO

Origin of Grain-Boundary Diffusion in MgO

Final Stage Densification in Vacuum Hot-Pressing of Alumina

Diffusion in Wide Grain Boundaries

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