Niobium-silicon

Abstract Multiphase Niobium-Silicon alloys offer great potential as a new generation of... 

Very high pressure and temperature experiments with the Sawaoka fixture on Nb-Si powder mixtures show that the silicon melted but the higher melt temperature niobium did not. Under these conditions, only chemical reaction... 

Canister anodes consist of a spirally wound galvanised steel outer casing containing a carbonaceous based extender which surrounds the primary anode element which may be graphite, silicon iron, magnetite, platinised titanium, mixed metal oxide-coated titanium or platinised niobium, etc. 

Groundbeds consist of a carbonaceous extender generally coke breeze and graphite, silicon-iron scrap steel, platinised titanium or niobium anodes. 

Platinised tantalum Platinised niobium Platinised titanium Platinum Thermally deposited noble metal oxide on titanium High- silicon/ chromium iron... 

Impressed current systems are normally based upon anodes of silicon iron, platinised titanium or platinised niobium. The method of anode installation is usually by suspension. The anode configuration and number must be such as to ensure uniform current distribution. Considerable use is made of wire-type platinised-titanium, and niobium anodes which offer minimal weight and relative ease of mounting/suspension. 

Cihal, etal presented early data on the effects of chromium, nickel, molybdenum, titanium, niobium and silicon on the passive behaviour of stainless steel. 

Uchino and Azuma [504] developed and proposed a two-step calcination process of tantalum and niobium hydroxides to obtain oxides. The first treatment is recommended to be performed at 500-700°C, and the second- at 750-1000°C. It is reported that the above method ensures the production of oxides that contain only negligible concentrations of fluorine and silicon impurities. 

The fluorine concentration in hydrofluorides of tantalum and niobium is an extremely important issue. Fluorine that separates into the gaseous phase interacts with the construction elements of the furnaces, leading to additional contamination of the final product by silicon, aluminum, etc. Thus, it is recommended to perform diying in crucibles made of Teflon or polypropylene with appropriate temperature limitations. Use of crucibles made of carbon-glass ensures high quality and a broad working temperature range, at least up to 300-350°C. 

Chlorine Trifluoride Tech. Bull. , Morristown, Baker Adamson, 1970 Incandescence is caused by contact with bromine, iodine, arsenic, antimony (even at -10°C) powdered molybdenum, niobium, tantalum, titanium, vanadium boron, carbon, phosphorus or sulfur [1], Carbon tetraiodide, chloromethane, benzene or ether ignite or explode on contact, as do organic materials generally. Silicon also ignites [2],... 

Field emission displays are VFDs that use field emission cathodes as the electron source. The cathodes can be molybdenum microtips,33-35 carbon films,36,37 carbon nanotubes,38" 16 diamond tips,47 or other nanoscale-emitting materials.48 Niobium silicide applied as a protective layer on silicon tip field emission arrays has been claimed to improve the emission efficiency and stability.49 ZnO Zn is used in monochrome field emission device (FED) displays but its disadvantage is that it saturates at over 200 V.29... 

Between 1993 and 2004, synthetic studies of compounds involving bonds between silicon and group 5 metals were restricted to niobium and tantalum. 

Aluminum, barium, beryllium, boron, dysprosium, erbium, europium, gadolinium, gallium, germanium, hafnium, holmium, lanthanum, molybdenum, neodymium, niobium, phosphorus, praseodymium, rhenium, samarium, scandium, silicon, strontium, tantalum, terbium, thulium, tin, titanium, tungsten, uranium, vanadium, ytterbium, yttrium, zirconium... 

Preparation ofNb5Si3 Metallic niobium and silicon dioxide do not react if heated (for instance at 1100°C) under vacuum. In the presence of traces of H2 or I2 the formation of transporting compounds (SiO or Nbl4) is observed, followed by their migration and reaction according to the following schemes ... 

Gold, 0110 Hafnium, 4599 Indium, 4640 Iridium, 4643 Lanthanum, 4677 Lead, 4882 Lithium, 4680 Magnesium, 4690 Manganese, 4700 Mercury, 4600 Molybdenum, 4712 Neodymium, 4819 Nickel, 4820 Niobium, 4817 Osmium, 4873 Palladium, 4885 Platinum, 4887 Plutonium, 4888 Potassium, 4645 Praseodymium, 4886 Rhenium, 4890 Rhodium, 4892 Rubidium, 4889 Ruthenium, 4894 Samarimn, 4911 Selenium, 4908 Silicon, 4909 Silver, 0001 Sodium, 4796 Strontium, 4913 Tantalum, 4914 Technetium, 4915 Tellurium, 4916 Thallium, 4922 Thorium, 4917 Tin, 4912 Titanium, 4919 Timgsten, 4925 Uranium, 4923 Vanadium, 4924 Zinc, 4927 Zirconium, 4928... 

Reaction with amorphous silicon at 900°C, catalyzed by steam produces cadmium orthosilicate, Cd2Si04. The same product also is obtained by reaction with sdica. Finely divided oxide reacts with dimethyl sulfate forming cadmium sulfate. Cadmium oxide, upon rapid heating with oxides of many other metals, such as iron, molybdenum, tungsten, titanium, tantalum, niobium, antimony, and arsenic, forms mixed oxides. For example, rapid heating with ferric oxide at 750°C produces cadmium ferrite, CdFe204 ... 

Niobium combines with carbon, boron, silicon and other elements at very high temperatures, forming interstitial binary compounds of varying compositions. With carbon, it forms niobium carbide having compositions varying from NbCo.7 to NbC [12069-94-2]. With boron, the products are orthorhombic niobium boride, NbB [12045-19-1], and the hexagonal diniobium diboride, Nb2B2[12007-29-3]. 

In 1901 Henri Moissan pulverized some American columbite, mixed with it some sugar charcoal, compressed the mixture, and heated it from seven to eight minutes in his electric furnace, using a current of one thousand amperes under fifty volts. After volatilizing all the manganese and part of the iron and silicon, he obtained a melt containing niobium and tantalum combined with carbon. 

Silica is reduced to silicon at 1300—1400°C by hydrogen, carbon, and a variety of metallic elements. Gaseous silicon monoxide is also formed. At pressures of >40 MPa (400 atm), in the presence of aluminum and aluminum halides, silica can be converted to silane in high yields by reaction with hydrogen (15). Silicon itself is not hydrogenated under these conditions. The formation of silicon by reduction of silica with carbon is important in the technical preparation of the element and its alloys and in the preparation of silicon carbide in the electric furnace. Reduction with lithium and sodium occurs at 200—250°C, with the formation of metal oxide and silicate. At 800—900°C, silica is reduced by calcium, magnesium, and aluminum. Other metals reported to reduce silica to the element include manganese, iron, niobium, uranium, lanthanum, cerium, and neodymium (16). 

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