Tungsten

About: Tungsten is a research topic. Over the lifetime, 35225 publications have been published within this topic receiving 456213 citations. The topic is also known as: W & element 74.

WO3 gas sensors prepared by thermal oxidization of tungsten

Abstract: Tungsten trioxide (WO3) was grown by direct thermal evaporation of metal tungsten foils in an oxygen atmosphere. The samples were characterized by scanning electron microscopy (SEM), energy-dispersive X-rays (EDX) analysis and Raman spectroscopy. The synthesized products consisted of crystalline aggregates having a mean size of about 0.8 μm. Raman spectroscopy evidenced typical vibrational peaks of the monoclinic WO3 phase. The samples were investigated as resistive gas sensors towards NO2, NO and NH3 gases. The influence of the working temperature on the sensor response was also studied. The sensors were sensitive enough to detect NO2 and less sensitive to NO and NH3. The relative variation of resistance as a function of gas concentration was found to be reversible and to follow a power-law relationship. The response and recovery times were determined according to a simple adsorption kinetic model.

4.17 – Tungsten as a Plasma-Facing Material

Abstract: As the most promising plasma-facing material for actual and future nuclear fusion devices, tungsten has to face and withstand a broad variety of severe operational conditions. These comprise high transient thermal loads, neutron irradiation-induced material degradation and transmutation, hydrogen and helium attack at the plasma-facing surface, and thermal fatigue under steady state heat fluxes as part of a plasma-facing component. The characterization and understanding of the material’s behavior under these conditions is essential for finding a grade of tungsten or tungsten alloy compatible with such an extreme environment.

Diffusion of hydrogen in bcc tungsten studied with first principle calculations

Abstract: First principle calculations were used to study the hydrogen migration properties in bulk bcc tungsten. Hydrogen has low solubility in tungsten and occupies the tetrahedral interstitial site with an energy difference of 0.38 eV compared to the octahedral interstitial site. The hydrogen diffusion coefficient was evaluated using the harmonic transition state theory and was found to agree with the experimental results at temperatures above 1500 K. The height of the migration barrier between two adjacent tetrahedral sites was found to be 0.21 eV, which is lower than the value 0.39 eV obtained for the migration barrier from degassing measurements in the temperature range between 1100 and 2400 K. The tunneling correction to the diffusion rate provides much better agreement with the experimental result at 29 K than the extrapolated experimental D from high temperature measurements.

Method for low-temperature organic chemical vapor deposition of tungsten nitride, tungsten nitride films and tungsten nitride diffusion barriers for computer interconnect metallization

Abstract: Processes for producing tungsten nitride and tungsten nitride films are provided in which a tungsten carbonyl compound and a nitrogen-containing reactant gas are reacted at a temperature below about 600° C. Tungsten nitride precursors are also included which comprise a tungsten carbonyl compound capable of forming a tungsten nitride film in the presence of a nitrogen-containing reactant gas at a temperature of less than about 600° C. A process for forming a film by atomic layer deposition is also provided which includes introducing into a substrate having a surface into a deposition chamber and heating the substrate to a temperature sufficient to allow adsorption of a tungsten source precursor or an intermediate of a tungsten source precursor, introducing a tungsten source precursor into the deposition chamber by pulsing for a period of time sufficient to form a self-limiting monolayer of the source precursor or an intermediate of the tungsten source precursor intermediate, introducing an inert gas into the deposition chamber by pulsing the inert gas to purge the deposition to remove the tungsten nitride precursor in the gas phase, introducing a nitrogen-containing gas into the deposition chamber by pulsing to react with the adsorbed precursor monolayer on the substrate surface and to form a first tungsten nitride atomic layer on the substrate surface. An inert gas may then introduced into the deposition chamber for a period of time sufficient to remove the unreacted nitrogen-containing gas and reaction byproducts from the deposition chamber. The entire pulsing sequence including precursor, inert gas, nitrogen-containing gas may be repeated until a film with a desired thickness is achieved.