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BY-NC-ND 3.0 license Open Access Published by De Gruyter June 2, 2014

Oxydation von Wolfram und Molybdän in Sauerstoff-Atmosphäre bei niederen Drucken und hoher Temperatur ** ** / Oxidation of Tungsten and Molybdenum in Oxygen-Atmosphere at Low Pressures and High Temperature

Georg Wahl

Abstract

The oxide evaporation of Mo and W (polycrystalline and 110-oriented) in oxygen (2·10-6 to 6·10-6 Torr) at 1900 K is investigated.

Two parallel discs are operated in an oxygen atmosphere. One of these discs ("emitter", Mo or W) is kept at 1900 K, the other one ("collector") at 1000 K. During operation, oxides of the emitter material are formed on the emitter surface, evaporated, and condensed on the collector. The oxide profile on the collector is measured by microprobe. The profile allows the determination of WM=jM/jE and Wtot = j(O2 in oxides)/jE. jM: evaporation density of W or Mo atoms bound in oxides; j (O2 in oxides) : evaporation density of oxides of emitter metal and impurities (in O2-units) ; jE : impingement density of O2-molecules.

Calculations used to determine WM and Wtot are described.

The measurements gave the following values for WM and Wtot:

tungsten, polycrystalline: WM=(7±1)%; Wtot= (8,5 ± 1)%; tungsten, 110-oriented: WM= (2±0.5)%; Wtot≈2%; molybdenum, polycryst.: WM=(37±2)%; Wtot= (42 ±4)% .

Received: 1972-7-29
Published Online: 2014-6-2
Published in Print: 1972-12-1

© 1946 – 2014: Verlag der Zeitschrift für Naturforschung

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

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