Further Comments on the Theory of Grain Growth in Porous Compacts

Nichols, F.A.

doi:10.1111/j.1151-2916.1968.tb11924.x

Cited by 61 publications

(44 citation statements)

References 4 publications

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“…Later Nichols [5] derived a more appropriate equation for the drag force, Eq. (13) in Part 1, which was applied by Brook [6,7] to consideration of normal grain growth kinetics controlled by pore migration.…”

Section: Phenomenological Considerationmentioning

confidence: 99%

A new model of grain growth kinetics in UO2 fuel pellets. Part 2: Normal grain growth kinetics controlled by pore migration

Veshchunov

2005

Journal of Nuclear Materials

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Section: Phenomenological Considerationmentioning

confidence: 99%

A new model of grain growth kinetics in UO2 fuel pellets. Part 2: Normal grain growth kinetics controlled by pore migration

Veshchunov

2005

Journal of Nuclear Materials

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“…The analysis of bubble-boundary separation presented above does not yield the bubble drag in low-velocity migration easily, so we use the older, phenomenological approximation, which has been discussed by Shewmon (1964), Kingery and Francois (1965), Nichols (1966Nichols ( , 1968, and Brook (1969), among others. Using the analysis of Shewmon (1964), the bubble-drag force in the low-velocity regime, P b , is (30) where Nb is the number of bubbles per grain boundary 2nR 2 is the area per grain boundary (the other 2TlR2 of ~ spherical grain is allocated to adjacent grains), and F b , the drag force per bubble, is given by…”

Section: Alley and Others: Grain Growth In Polar Icementioning

confidence: 99%

Grain Growth in Polar Ice: I. Theory

1986

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ABSTRACT. Many observations regarding grain growth in ice sheets are glaciologically interesting but imperfectly understood. Here we develop the theory of grain growth in ice th,at is not deforming rapidly, and in the succeeding paper we use this theory to explain observations from glacial ice. In the absence of significant strain energy, the driving force for grain growth arises from grain-boundary curvature. Grain growth is slowed by the interaction of grain boundaries with extrinsic materials (microparticles, bubbles, and dissolved impurities) . If the driving force for growth is not large enough to cause boundaries to separate from an extrinsic material, then the grain-boundary velocity is determined by the velocity characteristic of the extrinsic material (low-velocity regime). If the driving force is large enough to cause separation, then boundaries migrate more rapidly than the extrinsic material (high-velocity regime) but the net driving force is reduced through transient pinning by the extrinsic material. Polar ice is typically in the low-velocity regime relative to dissolved impurities and the high-velocity regime relative to microparticles and bubbles. Cross-sectional area of grains is predicted to increase linearly with time under most but not all circumstances. RESUME. Croissance des grains dans la glace poiaire: I. Theorie. De nombreuses observations sur la croissance des grains dans les calottes polaires sont interessantes du point de vue glaciologique mais pas encore totalement elucidees. Nous developpons ici une theorie de croissance des grains dans une glace it deformation faible et dans I'article suivant nous l'utilisons pour expliquer les observations obtenues sur ce type de glace. En I'absence d'energie de deformation notable, la cause de croissance du grain provient de sa courbure de surface. La croissance du grain est diminue par l'interaction de sa surface avec des materiaux extrinseques (microparticules, bulles, et impuretes dissoutes). Si la force majeure de croissance n'est pas suffisante pour separer la surface du materiel extrinseque, alors la vitesse de la limite du grain est determinee par la vitesse caracteristique du materiau extrinseque (regime de vitesse lente). Au contraire SYMBOLS USED AND VALUES OF CONSTANTSGrain-boundary impurity concentration Eutectic composition for impurity-ice system Ice-lattice impurity concentration si cette force est suffisante pour assurer la separation, alors les limites migrent plus rapidement que le materiau (regime de fortes vitesses) mais la force principale est reduite it cause du pincement dO au materiau extrinseque. La glace polaire se situe typiquement dans un regime de basse vitesse vis it vis des impuretes dissoutes et dans un regime de fortes vitesses quant aux microparticules et aux bulles. On arrive it la conclusion qu'une section droite de grain s'accrOIt lineairement en fonction du temps dans la plupart des situations.

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“…For the gas bubbles in UO 2 Baker's data [4] show that small intragranular fission gas bubbles (average diameter $2 nm), formed during the irradiation were virtually immobile on subsequent annealing at temperatures <1500°C. With the growth of a bubble radius from 2 to $10 nm, the bubble diffusivity increases, in contradiction with the standard theoretical predictions.…”

Section: Introductionmentioning

confidence: 97%

“…The bubble mobility is described by the bubble diffusion coefficient which depends on the bubble radius R b . This dependence is different for the various diffusion mechanisms [1,2]. The bubble mobility in UO 2 is largest for the surface diffusion mechanism (at least for bubbles with R b 6 10 lm) and is inversely proportional to R À4 b , whereas a slower dependence on the bubble radius (/ R À3 b ) is typical for the two other mechanisms.…”

Section: Introductionmentioning

confidence: 98%