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Author Ackermann, R. J. ♦ Rauh, E. G.
Sponsorship USDOE
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Language English
Subject Keyword METALS, CERAMICS, AND OTHER MATERIALS ♦ DIFFRACTION ♦ EVAPORATION ♦ HIGH TEMPERATURE ♦ MASS SPECTROMETERS ♦ MEASURED VALUES ♦ OXYGEN ♦ QUALITATIVE ANALYSIS ♦ SOLID SOLUTIONS ♦ SOLIDIFICATION ♦ THERMODYNAMICS ♦ TUNGSTEN ♦ TUNGSTEN OXIDES ♦ VACUUM ♦ VAPORS ♦ X RADIATION
Abstract The sublimation behavior of the tungsten- oxygen system was investigated over the temperature range 1300 to 1600 deg K by means of mass effusion studies, mass spectrometric observations, chemical analyses, and x-ray diffraction examination of the condensed phases. Measurements were carried out on compositions ranging from WO<sub>1.80</sub> to WO<sub>3</sub>. In all cases the thermodynamically important vapor species are W<sub>4</sub>O<sub>12</sub>, W<sub>3</sub>O<sub>9</sub> , W<sub>3</sub>O<sub>8</sub>, and W<sub>2</sub>O<sub>6</sub>. Univariant behavior was observed for the solid phases W = WO<sub>2</sub>, WO<sub>2</sub>- W<sub>28</sub>O<sub>49</sub>, W<sub>18</sub>O<sub>49</sub>- W<sub>20</sub>O<sub>58</sub>, W<sub>20</sub>O<sub>58</sub> - W<sub>20</sub>O<sub>2.96</sub> and WO<sub>2.96</sub> . The composition WO<sub>2.96</sub>probably represents the azeotropic composition of the WO<sub>3-x</sub> solid solution produced by the vacuum and is the only single phase that evaporates congruently below 1550 deg K. Except for the W<sub>20</sub>O<sub>58</sub>-WO<sub>2.96</sub> mixture in which the composition of the vapor phase is between those of the solid phases, all other phases and mixtures of two solid phases evaporate incongruently, since the vapor phase is richer in oxygen than the condensed phase. Above 1550 deg K there are no congruently evaporating compositions. Standard free energies, enthalpies, and entropies of formation for the four major vapor species and for the W<sub>18</sub>O<sub>49</sub>, W<sub>20</sub>O<sub>58</sub>, and WO<sub>2.96</sub> solid phases are given.
ISSN 00223654
Educational Use Research
Learning Resource Type Article
Publisher Date 1963-12-01
Publisher Department Argonne National Lab., Ill.
Journal Journal of Physical Chemistry
Volume Number 67
Issue Number 12
Organization Argonne National Lab., Ill.


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