Mechanism of the Oxidation of Zirconium in Oxygen and Liquid Sodium

Smith, Tony

doi:10.1149/1.2423461

Cited by 17 publications

(2 citation statements)

References 13 publications

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“…Diffusion analysis applicable to this type of a system has been advanced by Wagner (8) and applied by many investigators (4,9,10). At time 0 < t < ~, subject to boundary conditions, Eq.…”

Section: Theoreticalmentioning

confidence: 99%

A Film-Thickness Determination of Nitrogen Diffusion in Zirconium Nitride

Rosa¹,

Hagel²

1968

J. Electrochem. Soc.

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Calculations of the diffusion coefficient for nitrogen in zirconium nitride are given in terms of a unidirectional, two-phase, volume-diffusion model. These calculations require the knowledge of both the thicknesses of nitride films and of nitrogen diffusion coefficients in the underlying zirconium metal 9 The values obtained can be represented by D ----7 9 • 10 -5 exp N---~ ZrN (--35,900/RT) cm2/sec for the temperature range of 650~176 Zirconium nitriding kinetics for extended exposures up to 900 hr are also reported 9 The portion of nitrogen confined to the s-zirconium phase amounts to about 80 w/o of the total nitrogen consumed during the over-all nitriding process 9The zirconium-nitrogen reaction has not attracted the interest of many investigators 9 Gulbransen and Andrew (1) described this metal-gas reaction in the temperature range of 400~176and Dravnieks (2) studied the kinetics at 862~176 Mallett et al. (3) measured the rate of surface reaction of zirconium with nitrogen in the range of 975~176 at 1 arm pressure. All these investigators report that the reaction conformed strictly to a parabolic relationship and that the reaction rate was much slower than with oxygen. These experiments were carried out for short time exposures, up to 7 hr.More recently, Rosa and Smeltzer (4) investigated nitriding kinetics in terms of models based on the growth of the reaction product layer and simultaneous dissolution of the reactant in the metal substrate. They found that over the temperature range 750 ~ 1000~and for exposures up to 170 hr, the reaction obeys the parabolic rate law. Using microhardness measurements, they determined the diffusion coefficient of nitrogen in s-zirconium as DN a-zr ~ 0 9 exp (--54,100/RT) cm2/sec, which to the best knowledge of the present authors is the only relationship available at this time.The purpose of this investigation is to evaluate the diffusion coefficients of nitrogen in hypostoichiometric zirconium nitride for the temperature range of 650 ~ 850~ in terms of data from nitriding kinetics and from the growth rates of the nitride layer. A comprehensive model relevant to the forthcoming calculations is presented. ExperimentalThe commonly used gravimetric method has been employed for measuring nitriding kinetics of 2 • 1 • 0.2 cm, 99.93 w/o (weight per cent) pure, zirconium samples 9 High-purity, better than 99.9 v/o (volume per cent) pure, nitrogen was passed through a cold trap and glass columns containing silica gel and phosphorous pentoxide to remove residual water vapor. Before exposing to nitrogen at a pressure of 400 Torr, specimens were treated by wet abrasion on 200 through 600-grit silicon carbide papers followed by final polishing on 8 and 1# diamond-dust impregnated laps, acetone washing, and careful drying to avoid water stains 9To prevent formation of a gap between the metal and mounting material, whenever microscopic measurements of nitride thicknesses had to be taken, all samples are cold mounted in "Hysol" self-setting epoxy resin and prepared for metallography by us...

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“…Diffusion analysis applicable to this type of a system has been advanced by Wagner (8) and applied by many investigators (4,9,10). At time 0 < t < ~, subject to boundary conditions, Eq.…”

Section: Theoreticalmentioning

confidence: 99%

A Film-Thickness Determination of Nitrogen Diffusion in Zirconium Nitride

Rosa¹,

Hagel²

1968

J. Electrochem. Soc.

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“…When a surface oxide forms, parabolic kinetics would be expected, although the mechanistic significance of n values of 3 for exposures in He at 700 • C is not clear. Cubic kinetics have been observed for other refractory metals, 10,28 and one hypothesis is that it may be related to the oxygen diffusion rate being a function of oxygen concentration in the substrate.…”

Section: Discussionmentioning

confidence: 99%

The Role of Oxygen Uptake and Scale Formation on the Embrittlement of Vanadium Alloys

Pint

DiStefano

2005

Oxid Met

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Vanadium alloys are of interest in fusion energy systems, however, their environmental durability is a major concern. Specimens of V-4Cr-4Ti were exposed to air and oxygen (10 5 Pa), low pressure (10 −3 −10 −6 Pa) oxygen and high purity He environments (10 5 −10 1 Pa) at 500−700 • C in order to characterize the surface oxide, determine oxidation kinetics and quantify effects on mechanical properties at 25 and 600 • C. At low oxygen pressures (P O 2 10 −5 Pa), linear reaction kinetics were measured for exposures up to 2000 hr and the data were used to develop a mathematical expression for the oxidation rate as a function of temperature and oxygen pressure. At higher pressures, linear-parabolic reaction kinetics were associated with high oxygen uptake and the formation of an external oxide layer. Room-temperature and 600 • C tensile ductility was reduced by these exposures, but specimens which formed an external oxide were found to retain some tensile ductility after exposure. However, similar specimens with an external oxide that were subsequently annealed for 2000 hr at 700 • C became severely embrittled demonstrating that a surface oxide will not prevent degradation of this refractory alloy. Exposures in He were performed to determine the effect of total gas pressure on oxygen uptake.

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Untersuchung von Korrosionseffekten durch Natrium an Metallen der vierten und fünften Nebengruppe

Borgstedt¹,

Frees²

1968

Materials & Corrosion

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Der Angriff von flüssigem Na auf Ti, Zr, V und Nb erfolgt über einen Austasch von Sauerstoff von der flüssigen zur metallischen festen Phase; wegen der hohen Bildungsenergie der Oxide dieser Metalle genügen schon Na2O‐Gehalte von weniger als 10 ppm für die Auslösung der Reaktion. Der Sauerstoff wird direkt in die Matrix der Metalle eigebaut, ohne daß eine Oxidschicht entsteht; die Aufnahme von Sauerstoff ist immer mit Versprödung verbunden. In vielen Fällen reichert sich der Sauerstoff in der Randzone des Metalls an, wobei mehrere Schichten unterschiedlicher Struktur und schlechter Haftung entstehen. Die Sauerstoffkonzentration läßt sich mittels Mikrohärtemssungen bestimmen.

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Mechanism of the Oxidation of Zirconium in Oxygen and Liquid Sodium

Cited by 17 publications

References 13 publications

A Film-Thickness Determination of Nitrogen Diffusion in Zirconium Nitride

A Film-Thickness Determination of Nitrogen Diffusion in Zirconium Nitride

The Role of Oxygen Uptake and Scale Formation on the Embrittlement of Vanadium Alloys

Untersuchung von Korrosionseffekten durch Natrium an Metallen der vierten und fünften Nebengruppe

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