Diffusion of nickel in beryllium

Anan’in, V. M.; Gladkov, V. P.; Zotov, V. S.; Skorov, D. M.

doi:10.1007/bf01232557

Cited by 11 publications

(10 citation statements)

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“…2). The previously disovered [4] lower mobility is due, in our opinion, to the low ratio of the specific activity of the diffusion source and the activity of the sample. The data for the hot-pressed material differ from the data obtained for cast baryllium.…”

mentioning

confidence: 79%

“…Data on iron diffusion, which have been obtained by different methods, are available [1][2][3][4]. There are plans to use beryllium in a thermonuclear reactor in the future.…”

mentioning

confidence: 99%

“…Diffusion of iron in hot-pressed beryllium (ñ -this work, × -[4]), cast beryllium (ÿ -this work, É -[4]), beryllium alloy with 0.31% Fe[2] (Ñ), and SR-beryllium[3] (Ÿ).…”

mentioning

confidence: 99%

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Diffusion mobility of iron in hot-pressed technical-grade beryllium

2005

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Beryllium is a well-known structural and functional material with unique properties. There are plans to use beryllium in a thermonuclear reactor in the future. The properties of beryllium, specifically, the mechanical properties, depend on the presence of impurities, not only their quantity but also on their form. The process controlling the distribution and redistribution of impurities during heat treatment of a material is diffusion. Iron, which is one of the main technological impurities, can influence the mechanical properties of beryllium and its alloys [1]. Data on iron diffusion, which have been obtained by different methods, are available [1][2][3][4]. These data are, in the main, contradictory, and their use in modern engineering calculations could be invalid. The present work is devoted to determining the diffusion mobility of iron in hot-pressed beryllium with the typical chemical composition found today.The experiment was performed on two technical-grade materials -hot-pressed and cast beryllium, which is the initial material for preparing the hot-pressed beryllium -to determine the effect of the fabrication technology on impurity diffusion. The cast material was prepared by induction remelting of magnesium-reduced beryllium; the hot-pressed material was obtained after the cast material was milled. The cast material differs from the hot-pressed material mainly in that the grain size in the former is incomparably larger: 0.5-10 mm versus 3-15 µm. The chemical composition of hot-pressed beryllium is always different from that of the initial cast material (Table 1). This especially concerns iron and oxygen. Iron enters beryllium during milling in ball mills, and even though the products of milling pass through magnetic separation and special chemical tretament, some of the iron that entered the beryllium from the steel balls remains. The solubility of oxygen in cast beryllium is negligibly low, so that it can be ignored, while in the hot-pressed material its content in the form of BeO reaches 0.5% and higher.The radioactive isotope 59 Fe in the form of iron (III) sulfate was deposited on the surface of beryllium. The total activity of the remainder of the sample was measured as successive layers were removed (Fig. 1). Diffusion annealing was performed at 1148-1393 K. In the layerwise analysis, after diffusion annealing, special attention was devoted to the accuracy with which the total activity and the depth of the removed layer were determined. This was done in order to be able to choose the correct model for the boundary conditions realized in the experiment, since the wrong model can change the diffusion mobility by a factor of 3-8. The experimental error attained for the total activity N and the penetration depth x was 2-5 times smaller than the spread between the conventional models used to describe diffusion experiments. On this basis, a new model, which takes account of the facts that the source of diffusion weakens with time and that the impurity solubility has a limit, was proposed for analyzing...

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confidence: 79%

“…Data on iron diffusion, which have been obtained by different methods, are available [1][2][3][4]. There are plans to use beryllium in a thermonuclear reactor in the future.…”

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confidence: 99%

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Diffusion mobility of iron in hot-pressed technical-grade beryllium

2005

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“…i.e., the integral activity of the sample's residue is in proportion to the concentration of the impurity [9]. Figure 3 gives experimental data on the diffusion of impurities in beryllium at different temperatures and calculated curves for the integral activity.…”

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confidence: 99%

“…The figure shows that the concentration profiles that are the solutions of the mathematical model (1), (10) are located between two curves corresponding to the well-known conditions at the source-matrix boundary: between the instantaneous source (τ → ∞) and the constant flux (τ → 0). Here the concentration profile is presented under the assumption that a constant impurity concentration is maintained at the matrix boundary [9].…”

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confidence: 99%

Problem on Diffusion of a Partially Soluble Impurity in a Solid Matrix with Allowance for the Depletion of the Diffusant Source with Time

Gladkov

Kashcheev

Петров

et al. 2005

J Eng Phys Thermophys

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An analytical expression for the concentration profile of a diffusing element partially soluble in the material's sample has been obtained on condition that the diffusion source is depleted with time. Examples of the use of the solution obtained for processing of diffusion experiments carried out with a number of impurities in beryllium have been considered. The use of the present model shows a more accurate agreement of the calculated and experimental concentration profiles, which enables one to refine the characteristics of diffusion mobility of the impurities in the materials under study.The stability of the structure of solid materials containing impurities is determined, as a rule, by the redistribution of the impurities between the solid solution and the isolated phases. The mobility of impurities in solid materials is limited by diffusion processes; therefore, the diffusion coefficients D i (i = 1, 2, ..., n) of the impurities, which are found by the corresponding experiments [1], are an important characteristic of any impurity-containing material. To increase the migration rate of the impurities one carries out the experiments at a higher-than-average temperature (homogenizes samples) and then extrapolates the result obtained for D to the region of low * ) temperatures, using the Arrhenius law [2]:Clearly, in extrapolating D(T) to lower temperatures, the error of determination of low-temperature diffusion coefficients increases; therefore, to improve the accuracy of their determination one must organize the processing of diffusion experiments so as to minimize the computational error for D.We recall that, in the course of diffusion experiments, one most often applies a source layer of labeled (radioactive) diffusing atoms to one side of the sample; the sample is annealed isothermally for a certain period; then one successively removes its layers on the source side of the source layer and analyzes the radioactivity of the sample's residue N(x), where x is the distance from the source layer to the sample [3].To simplify the processing of the experiment the layer applied to the sample is made as thin as possible and the geometry of the sample is selected so that the process of diffusion can be considered to be one-dimensional. The diffusion coefficient D is determined by comparison of the dependences N exp (x) obtained in the experiment and a certain reference calculated function N calc (x). The form of the latter depends on conditions that are realized at the boundary of the matrix and the source layer of a diffusing impurity in the process of diffusion. In [4], it has been shown that unreliable data on the boundary conditions reduce the accuracy of determination of the coefficient D several times. Consequently, extrapolating the result for D to low temperatures, one can make a mistake by an order of magnitude or more. In this connection, in processing the experiments, we seek to reconstruct the boundary conditions realized at the source layer-matrix boundary in homogenization of a sample as accurately as p...

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3.2.2 Alkaline earth metals

LeClaire¹,

Neumann²

Landolt-Börnstein - Group III Condensed Matter

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Diffusion of nickel in beryllium

Cited by 11 publications

References 2 publications

Diffusion mobility of iron in hot-pressed technical-grade beryllium

Diffusion mobility of iron in hot-pressed technical-grade beryllium

Problem on Diffusion of a Partially Soluble Impurity in a Solid Matrix with Allowance for the Depletion of the Diffusant Source with Time

3.2.2 Alkaline earth metals

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