Abstract
Tungsten oxides play a pivotal role in a variety of modern technologies, e.g., switchable glasses, wastewater treatment, and modern gas sensors. Metallic tungsten is used as armor material, for example in gas turbines as well as future fusion power devices. In the first case, oxides are desired as functional materials; while in the second case, oxides can lead to catastrophic failures, so avoiding the oxidation of tungsten is desired. In both cases, it is crucial to understand the reactivity of tungsten oxides with other chemicals. In this study, the different reactivities of tungsten oxides with the highly-oxophilic beryllium are studied and compared. Tungsten-(IV)-oxide and tungsten-(VI)-oxide layers are prepared on a tungsten substrate. In the next step, a thin film of beryllium is evaporated on the samples. In consecutive steps, the sample is heated in steps of 100 K from room temperature (r. t.) to 1273 K. The chemical composition is investigated after each experimental step by high-resolution X-ray photoelectron spectroscopy (XPS) for all involved core levels as well as the valence band. A model is developed to analyze the chemical reactions after each step. In this study, we find that tungsten trioxide was already reduced by beryllium at r. t. and started to react to form the ternary compounds BeWO3 and BeWO4 at temperatures starting from 673 K. However, tungsten dioxide is resistant to reduction at temperatures of up to 1173 K. In conclusion, we find WO2 to be much more chemically resistant to the reduction agent Be than WO3.
Highlights
Tungsten and its oxides play a pivotal role for the solution of current problems in material science
We find that tungsten trioxide was already reduced by beryllium at r. t. and started to react to form the ternary compounds BeWO3 and BeWO4 at temperatures starting from 673 K
This study aims to investigate the stability of thin layers of ceramic tungsten trioxide as well as a thin layer of its metallic counter part, tungsten dioxide
Summary
Tungsten and its oxides play a pivotal role for the solution of current problems in material science. The classical applications of tungsten are in environments with a high heat load, as in turbines or reactors. In these environments, the oxidation of tungsten results in catastrophic events. The formation of volatile tungsten oxides leads to mobilized radioactivity, which is unfavorable. In all these applications, it is crucial to understand the reactivity and stability of the different tungsten oxides. XPS is chosen because high-resolution XPS reveals the elemental composition, and shows their chemical binding state. This allows for evaluation of the chemical composition and reactions. The temperature reactivity study is conducted in situ under UHV (ultra-high vacuum) conditions to avoid the influence of atmospheric gases on the results
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
