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.

Platinum supported WOx–ZrO2: Effect of calcination temperature and tungsten loading

Abstract: The influence of calcination temperature (500–880°C) and of tungsten loading (2, 5 and 18 wt.%) on platinum supported on tungsten-oxide-promoted zirconia, where the platinum was added after high-temperature calcination of the support, has been studied. Catalysts were characterized by X-ray diffraction, temperature-programmed reduction, ammonia temperature-programmed desorption, X-ray photoelectron spectroscopy, laser Raman spectroscopy and catalytic activity for n-hexane isomerization in the presence of hydrogen. A maximum in catalytic activity, defined as “moles of n-hexane converted×(surface density of tungsten atoms)−1 h−1”, is observed for the sample calcined at 700°C. Regarding tungsten loading, samples calcined at 830°C and containing 2 and 5 wt.% tungsten show a lower catalytic activity than a sample containing 18 wt.%. The catalytic activity is associated with the presence of crystalline WO3.

Adsorption of Oxygen and Carbon Monoxide on Tungsten

Abstract: The adsorption of oxygen, carbon monoxide, and nitrogen on a tungsten ribbon filament at 300°K has been measured by means of the flash filament technique An omegatron rf mass spectrometer has been used to measure pressure It is shown that oxygen pressures cannot be measured satisfactorily with ionization gauges of the hot‐tungsten‐filament type The total amounts of gases adsorbed by tungsten are 57×1014 molecules/cm2 for oxygen, 58×1014 for carbon monoxide, and 18×1014 for nitrogen The sticking probabilities of these gases on the uncovered surface are 065 for oxygen, 062 for carbon monoxide, and 042 for nitrogen All of the carbon monoxide and nitrogen desorb from the heated filament as the gases CO and N2; less than 1 percent of the oxygen desorbs as O2 The filament pumps oxygen at a rate of 9 liters/cm2 sec at temperatures above 2000°K

Elevated temperature ablation resistance and thermophysical properties of tungsten matrix composites reinforced with ZrC particles

Abstract: In order to improve the elevated temperature ablation resistance of the copper infiltrated tungsten materials (Cu/W) which are used as the rudders of the rocket motors at present, a new kind of tungsten matrix composites reinforced by 30 vol% zirconium carbide particles (ZrCp/W) was developed, and the elevated temperature ablation resistance and thermophysical properties of the new materials were investigated. The values of the mass ablation rate and linear ablation rate of ZrCp/W were much lower than that of Cu/W, which indicated that the addition of ZrC particles in tungsten matrix remarkably increased the ablation resistance. Thermal thermochemical oxidation of tungsten and ZrC particles was the main ablation mechanism of ZrCp/W. A self-made dynamic responding multi-wavelength pyrometer was employed to measure the ablated surface temperatures and a thermal couple was employed to measure the back surface temperatures. The important temperature curves of the ablated surface and back surface of the specimens were successfully detected online, which indicated that ZrCp/W has good thermal shock resistance. The present of ZrC particles in tungsten matrix remarkably decreased the thermal conductivity and thermal diffusivity of the ZrCp/W composites, which is very useful for increasing the elevated temperature ablation resistance of the composites. The excellent elevated temperature ablation resistance of ZrCp/W is attributed to the lower thermal conductivity, lower thermal diffusivity, oxidation resistance and high melting points. The good properties of ZrCp/W makes it be suitable for the rudders for rocket motors instead of Cu/W.

Tin contact barc for tungsten polished contacts

Abstract: The present invention provides improved critical dimension control on oxide films using a titanium nitride (TiN) antireflection coating (ARC). The present invention also provides for improved methods for forming more uniform local interconnects and contact holes through oxide films, by providing a TiN layer as an ARC layer. The TiN ARC layer is used in a process for etching contacts and filling the contacts with a barrier metal made out of Ti or TiN and a tungsten fill. The TiN layer is easily removed during a tungsten polish, which also removes the barrier metal. Additionally, the TiN can serve as a hardmask for the contact etch, since the chemistry is typically selective to TiN. This allows the resist to be thinned down, providing the lithography process with a larger process window.