Oxidation rates of niobium and tantalum alloys at low pressures

DiStefano, J.R.; Hendricks, J.W.

doi:10.1007/bf01113371

Cited by 22 publications

(10 citation statements)

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“…The oxidation process of rereficatroy metals has been the subject of numerious past studies and reviews. [1][2][3][4][5][6][7] It is well known that most of metals except noble metals, form tarnishing oxides layers even at low temperatures. Their reaction with oxygen at high temperature is expected to be very rapid.…”

Section: Introductionmentioning

confidence: 99%

“…Another group consists of transition metals, such as iron, nickel, cobalt, molebdenum, vanadium etc., these have moderate oxidation resistance but are the base elements for the important alloys used in high temperature applications. [3][4][5][6] The study of oxidation kinetics of metals provides an important and reliable base to understand the oxidation behaviour of metals. The extent as well as the rate of oxidation reaction can be measured by the amount of metal consumed and the amount of oxygen consumed or the amount of oxide produced.…”

Section: Introductionmentioning

confidence: 99%

“…air and oxygen gas) under different experimental conditions like temperature, oxygen partial pressure, duration of oxidation etc. [1][2][3][4][5][6][7] But very limited reports were published on the oxidation of metals using oxygen plasma as an oxidizing medium. It has been reported that oxygen plasma comprises positive ions, negative ions, neutrals, and many excited metastable states of oxygen molecules.…”

Section: Introductionmentioning

confidence: 99%

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Oxidation of vanadium metal in oxygen plasma and their characterizations

et al. 2015

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In this report, the role of oxygen plasma on oxidation of vanadium (V) metal and the volatilization of its oxides has been studied as a function of source (V metal strip) temperature (Tss) and oxygen partial pressure (PO2). The presence of O2-plasma not only enhances the oxidation rate but also ficilitates in transport of oxide molecules from metal to substrate, as confirmed by the simultanous deposition of oxide film onto substrate. Both the oxidized metal strips and oxide films deposited on substrates are characterized separately. The structural and vibrational results evidence the presence of two different oxide phases (i.e. orthorhombic V2O5 and monocilinic V O2) in oxide layers formed on V metal strips, whereas the oxide films deposited on substrates exhibit only orthorhombic phase (i.e. V2O5). The decrease in peak intensities recorded from heated V metal strips on increasing Tss points out the increment in the rate of oxide volatilization, which also confirms by the oxide layer thickness measurements. The SEM results show the noticeable surface changes on V-strips as the function of Tss and PO2 and their optimum values are recorded to be 500 ˚C and 7.5 × 10−2 Torr, respectively to deposit maximum thick oxide film on substrate. The formation of microcracks on oxidized V-strips, those responsible to countinue oxidation is also confirmed by SEM results. The compositional study of oxide layers formed on V-strips, corroborates their pureness and further assures about the existence of mixed oxide phases. The effect of oxygen partial pressure on oxidation of V-metal has also been discussed in the present report. All the results are well in agreement to each other.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Oxidation of vanadium metal in oxygen plasma and their characterizations

et al. 2015

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“…Low pressure exposures were conducted for up to 2000 hr in an ultra high vacuum system in which a base vacuum of 10 −7 Pa (10 −9 Torr) could be achieved. 21 A micrometering leak valve was used to achieve oxygen partial pressures of 10 −3 -10 −6 Pa (10 −5 -10 −8 Torr). For testing in flowing helium at 10 5 Pa (1 atm), the pumping system was closed after pressurization and excess gas pressure was removed through an oil bubbler.…”

Section: Methodsmentioning

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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“…In addition, Ta-based alloys have unique combination of excellent mechanical and thermal properties at elevated temperatures due to high melting point and good workability suitable for high temperature structural materials [6][7][8]. However, their potential as refractory metallic alloys is not fully realized mainly because of poor oxidation resistance of pure Ta or commercial Ta alloys [9][10][11][12][13][14]. Many research efforts have been attempted to develop a high temperature Ta-base alloys with the ability to form a protective oxide scale, but few satisfactory results have been obtained.…”

Section: Introductionmentioning

confidence: 99%