Of vanadium metal

Vanadium metal can be prepared either by the reduction of vanadium chloride with hydrogen or magnesium or by the reduction of vanadium oxide with calcium, aluminum, or carbon. The oldest and most commonly used method for producing vanadium metal on a commercial scale is the reduction of V20 with calcium. Recently, a two-step process involving the alurninotherniic reduction of vanadium oxide combined with electron-beam melting has been developed. This method makes possible the production of a purer grade of vanadium metal, ie, of the quaUty required for nuclear reactors (qv). 

Halides and Oxyhalides. Vanadium(V) oxytrichloride is prepared by chloriaation of V20 mixed with charcoal at red heat. The tetrachloride (VCl is prepared by chlorinating cmde metal at 300°C and freeing the Hquid from dissolved chlorine by repeated freezing and evacuation. It now is made by chlorinating V20 or VOCl ia the presence of carbon at ca 800°C. Vanadium trichloride (VCl ) can be prepared by heating VCl ia a stream of CO2 or by reaction of vanadium metal with HCl. 

Minor uses of vanadium chemicals are preparation of vanadium metal from refined pentoxide or vanadium tetrachloride Hquid-phase organic oxidation reactions, eg, production of aniline black dyes for textile use and printing inks color modifiers in mercury-vapor lamps vanadyl fatty acids as driers in paints and varnish and ammonium or sodium vanadates as corrosion inhibitors in flue-gas scmbbers. 

The benefit of vanadium as an additive in steel is that it forms V4C3 with any carbon present, and this disperses to produce a finegrained steel which has increased resistance to wear and is stronger at high temperatures. Such steels are widely used in the manufacture of springs and high-speed tools. In 1995, world consumption of vanadium metal, alloys and concentrates exceeded 33 000 tonnes of contained vanadium. 

A sample of an oxide of vanadium weighing 4.589 g was heated with hydrogen gas to form water and another oxide of vanadium weighing 3.782 g. The second oxide was treated further with hydrogen until only 2.573 g of vanadium metal remained. 

One of the early applications of calcium as a reducing agent has been in the preparation of vanadium metal from vanadium pentoxide ... 

The production of vanadium metal essentially is the calcium reduction ot vanadium pcntcixide in Ihc presence of iodine and is known its the McKechiiie-Seyboll process. The reaction is earned out in a steel bomb at about 7(K) C. The end products are vanadium metal, lime, and calcium iodide. A similar iodide process also is used in the production of high-purily zirconium. 

Several generations of vanadium metal catchers have been developed (1, 2), leading to an improved activity retention at high vanadium levels on catalyst. The recent progress in nickel tolerance with new nickel encapsulation technologies is just as dramatic. 

Vanadium(V) oxide, V2O5, a yellow, amphoteric solid, may be obtained as an intermediate in the preparation of vanadium metal, as indi-... 

Vanadium Triiodide. VI3 can be prepared by reaction of vanadium metal with iodine at elevated temperatures. It is a brownish-black, hygroscopic crystalline powder, soluble in most nonpolar solvents, that begins to dissociate into VI2 and I2 at 270 °C.i... 

When a 0.3546-g sample of vanadium metal is heated in air, it reacts with oxygen to reach a final mass of 0.6330 g. Calculate the empirical formula of this vanadium oxide. 

When 9.59 g of a certain vanadium oxide is heated in the presence of hydrogen, water and a new oxide of vanadium are formed. This new vanadium oxide has a mass of 8.76 g. When the second vanadium oxide undergoes additional heating in the presence of hydrogen, 5.38 g of vanadium metal forms. 

VC powder is prepared by the reaction of vanadium oxide or ammonium vanadate with carbon at 1500-1700 C in hydrogen followed by a vacuum heat treatment. The reaction of vanadium metal with carbon under vacuum is also used. VC coatings are deposited by CVD, evaporation or sputtering (see Clusters 14 and IS). 

Reaction of vanadium oxide or ammonium vanadate with carbon at 1500-1700°C in hydrogen followed by a vacuum heat-treatment Reaction of vanadium metal Avith carbon under vacuum... 

Values for the melting point of vanadium metal have ranged from 1860° (Wilhelm et ai, 1954) to 1919° (Oriani and Jones, 1954). All of these measurements were made using material of variable purity, for which corrections were not made. The use of proper corrections leads to good agreement with the corrected value of 1888° + 10°, given by Storms and McNeal (1962). 

Vanadium pentoxide is the raw material for production of vanadium metal, and ferrovanadium is an alloy that is added to a steel melt to give the steel a specified vanadium content. In addition ash, ore, and slag containing 1900 tonnes of vanadium were imported to the USA in 2000. 

The kinetics of the electrode processes in vanadium-containing chloride melts was investigated in the middle of the last century [1-5]. Most of the studies were conducted using polarization measurements. Data obtained by different authors are rather fragmentary and often contradictory. For example, there is no information on anodic dissolution of vanadium metal in chloride electrolytes. 

Anodic dissolution of vanadium metal in NaCl-KCl melts... 

Anodic dissolution of vanadium metal at current densities below 1 A/cm leads to the formation of vana-dium(II) ions and the reaction kinetics are controlled by the diffusion of the reaction products formed. At higher current densities the anodic process is accompanied by various types of salt passivation. V(II) complexes can be reversibly oxidized to V(in) on a glassy carbon anode. This reaction is also controlled by mass transfer. 

Centrone A, Harada T, Speakman S et al (2010) Facile synthesis of vanadium metal-organic frameworks and their magnetic properties. Small 6 1598—1602... 

---