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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.


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Patent
20 Aug 1996
TL;DR: In this article, an ion implantation equipment is modified so as to provide filament reflectors to a filament inside of an arc chamber, and to remove the electrical insulators for the filament outside of the arc chamber and providing a means of shielding, thereby reducing the formation of a conductive layer on said insulators and greatly extending the lifetime and reducing downtime of the equipment.
Abstract: Ion implantation equipment is modified so as to provide filament reflectors to a filament inside of an arc chamber, and to remove the electrical insulators for the filament outside of the arc chamber and providing a means of shielding, thereby reducing the formation of a conductive layer on said insulators and greatly extending the lifetime and reducing downtime of the equipment. The efficiency of the equipment is further enhanced by means of an interchangeable liner for the arc chamber that increases the wall temperature of the arc chamber and thus the electron temperature. The use of tungsten parts inside the arc chamber, obtained either by making the arc chamber itself or portions thereof of tungsten, particularly the front plate having the exit aperture for the ion beam, or by inserting a removable tungsten liner therein, decreases contamination of the ion beam. Serviceability of the arc chamber is improved by means of a unitary clamp that separately grips both the filament and filament reflectors. This clamp can also advantageously be made of tungsten.

83 citations

Journal ArticleDOI
TL;DR: In this paper, four kinds of tungsten borides were synthesized by solid state reaction between Tungsten and amorphous boron powders, and the formation of W2B was initiated approximately at 1000° C in excess of tengsten content.
Abstract: Various kinds of tungsten borides were synthesized by solid state reaction between tungsten and amorphous boron powders. The mixed powders with various compositions (B/W = 0.4 to 13.0) were treated at 800 to 1550° C for 0 to 120 min in a stream of argon. Four kinds of boride phases such as W2B, WB, W2B5 and WB4 were formed, although the boride phase having the composition of the highest boride, WB12, did not appear. The formation of W2B was initiated approximately at 1000° C in excess of tungsten content. On the other hand, in the excess boron content, the formation of WB, W2B5 and WB4 was initiated approximately at 800, 950 and 1200° C, respectively. The maximum formation amount and crystallinity of WB and W2B5 was found in nearly 10 at % excess boron content in their own stoichiometric compositions. The only crystalline phase of WB4 was prepared with a large excess boron content. However, the formation behaviour of WB4 showed that WB4 is metastable above 1400° C. The stability of WB4 phase could be increased by the presence of excess boron.

83 citations

Posted Content
TL;DR: In this paper, an infrared and Raman spectroscopy study of tungsten oxide-organic layered hybrid materials has been carried out, showing that the longer chains are bound by electrostatic interactions as well as or in place of the hydrogen bonding that must be present in the shorter chain ethylenediamine hybrids.
Abstract: Tungsten oxide-organic layered hybrid materials have been studied by infrared and Raman spectroscopy, and demonstrate a difference in bonding nature as the length of the interlayer organic `spacer' molecule is increased. Ethylenediamine-tungsten oxide clearly displays a lack of terminal -NH3+ ammonium groups which appear in hybrids with longer alkane molecules, thus indicating that the longer chains are bound by electrostatic interactions as well as or in place of the hydrogen bonding that must be present in the shorter chain ethylenediamine hybrids. The presence of organic molecules between the tungsten oxide layers, compared with the layered tungstic acid H2WO4, shows a decrease in the apical W=O bond strength, as might be expected from the aforementioned electrostatic interaction.

83 citations

Journal ArticleDOI
TL;DR: In this paper, a tungsten-containing MCM-41 mesoporous molecular sieve was synthesized by the hydrolysis of tetraethylorthosilicate and ammonium tungstate in the presence of cetylpyridinium bromide as template in strongly acidic medium.
Abstract: A novel tungsten-containing MCM-41 mesoporous molecular sieve was synthesized by the hydrolysis of tetraethylorthosilicate and ammonium tungstate in the presence of cetylpyridinium bromide as template in strongly acidic medium. Physicochemical characterizations of this composite performed by means of powder X-ray diffraction, ICP atomic emission, FT-IR, laser Raman, and diffuse reflectance UV–Vis spectroscopy verified that tungsten ion could be isolated in framework positions of the MCM-41 mesostructure by this approach. Thermo-gravimetric study on this composite suggested that above 90% of the template encapsulated in the as-synthesized mesophase was recoverable by direct ethanol extraction. A catalytic test using hydrogen peroxide hydroxylation of cyclohexene as probe reaction proved that the framework tungsten site in the W-MCM-41 could afford the mesophase with fairly high activity in promoting this reaction, wherein acetic acid was found to be useful as solvent.

83 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20231,055
20222,162
2021902
20201,216
20191,447
20181,372