Oxydation von Titan

The rate law for the oxidation of zirconium was found to be initially intermediate to linear and parabolic, then parabolic, and then nearly cubic over the first 10-rain interval at both 400 ~ and 500~ At 400~ the oxidation rate became parabolic for an oxide thickness of about 300A. At 500~ the oxidation rate became nearly cubic at about 3300A, the transition from one rate to another being gradual rather than sharp. The activation energy for the parabolic region was 29.3 kcal/mole and for the nearly cubic region approximately 42 kcal/mole. The results obtained were independent of the shape of the specimen and its surface preparation. An analysis shows that the high solubility of oxygen in zirconium is not a sufficient condition to account for a cubic rate law of oxidation for a concentration-independent diffusion constant.

Section: Discussionmentioning

confidence: 99%

On the Oxidation of Zirconium

Sense¹

1962

“…The growth of the thin interference color film has been found experimentally to obey a logarithmic growth law (3), and it is probable, therefore, that this is an example of the applicability of Uhlig's thin film growth law to a case of metal oxidation. The initial oxidation of hafnium (34) and titanium (27)(28)(29)(30) has been found also to obey a logarithmic law at temperatures below 350~…”

Section: Discussionmentioning

confidence: 99%

The Oxidation and Corrosion of Zirconium and its Alloys

Cox

1961

“…At present there is no adequate model to account for cubic oxidation of zirconium, although it has been suggested that such kinetics may be partially due to oxygen solution in the metal (7,18). Consequently, it appears more appropriate, at least for long exposures, to represent the extensive data for the chemically polished specimens from this investigation in terms of a parabolic equation accounting for lattice diffusion of oxygen in the oxide and oxygen solution in the metal.…”

Section: T H E P R E S E N T Studies W E R E C a R R I E D Out To E X...mentioning

confidence: 99%

The Oxidation Kinetics of Zirconium in the Temperature Range 400°–600°C

Hussey

Smeltzer

1964

The oxidation kinetics of zirconium were determined in the temperature range 400~176 at subatmospheric pressures for exposure times of 650 hr at 400~ to 160 hr at 600~ by a microbalance technique. From scale thickness measurements, it was shown that at temperatures between 500~176 the amount of oxygen in the metal varies from 14 to 23% of the total oxygen consumption respectively. Further both the oxidation kinetics and the oxygen distribution between the metal and the oxide were found to be independent of changes of oxygen pressure from 0.25 to 50 cm Hg. The kinetics were fitted to a parabolic rate relation after an initial deviation. In the parabolic range, oxidation behavior approximated to a model in which the oxidation rate was determined by oxygen diffusion in both the oxide and metal.