Niobium metallurgy

In summary, investigations in the area of the chemistry of tantalum and niobium fluoride compounds will advance tantalum-niobium metallurgy and promote the development of new materials for modem applications. 

Niobium is also important in nonferrous metallurgy. Addition of niobium to tirconium reduces the corrosion resistance somewhat but increases the mechanical strength. Because niobium has a low thermal-neutron cross section, it can be alloyed with tirconium for use in the cladding of nuclear fuel rods. A Zr—l%Nb [11107-78-1] alloy has been used as primary cladding in the countries of the former USSR and in Canada. A Zr—2.5 wt % Nb alloy has been used to replace Zircaloy-2 as the cladding in Candu-PHW (pressurized hot water) reactors and has resulted in a 20% reduction in wall thickness of cladding (63) (see Nuclear reactors). 

G. L. Miller, Metallurgy of the Rarer Metals—6 Tantalum and Niobium Butterworths Scientific Pubheations, London, 1959. 

D. L. Douglass and F. W. Kunz, eds., "Columbium Metallurgy," Proceedings Symposium, New York, June 9—10, 1960, Interscience PubHshers, New York, 1961. B. W. Gonser and E. M. Sherwood, eds.. The Technology of Columbium (Niobium), John Wiley Sons, Inc., New York, 1958. 

The basic corrosion behaviour of stainless steels is dependent upon the type and quantity of alloying. Chromium is the universally present element but nickel, molybdenum, copper, nitrogen, vanadium, tungsten, titanium and niobium are also used for a variety of reasons. However, all elements can affect metallurgy, and thus mechanical and physical properties, so sometimes desirable corrosion resisting aspects may involve acceptance of less than ideal mechanical properties and vice versa. 

The carbide precipitation that leads to sensitised grain boundary regions can be minimised by reducing the carbon to 0.03% or less but this increases the cost and reduces the strength. The alternative is to add stabilising elements such as titanium or niobium, which are stronger carbide formers than chromium. There are numerous texts that describe the metallurgy of... 

The monograph will be useful for tantalum and niobium producers, for researchers studying the chemistry of fluorides, and for teachers and students at chemistry and metallurgy departments. 

C. K. Gupta, Extractive Metallurgy of Niobium, Tantalum and Vanadium, Int. Metals Reviews, Vol. 29,... 

C. K. Gupta and A. K. Suri, Extractive Metallurgy of Niobium CRC Press, Boca Raton, Florida, 1994. 

Nonessential nutrients, 17 645 Noneutectoid steels, 23 218 Nonferrous alloys, vanadium in, 25 525 Nonferrous metallics, eddy-current separation of, 15 455—451 Nonferrous metallurgy niobium in, 17 145 oxygen in, 17 762 slaked lime in, 15 63... 

Niobium is a very important metal in both ferrous and nonferrous metallurgy. As an additive to alloys or when alloyed with other metals niobium imparts high mechanical strength, high electrical conductivity, and ductihty to alloys. It enhances corrosion resistance of most alloys. The metal and several of its alloys exhibit superconductivity. Nobium is used as an additive in... 

In metallurgy, niobium is classified as a refractory metal, along with tungsten, tantalum, and molybdenum. A comparison of the four metals is given in the accompanying table. 

Gupta. C.K, and A,K. Suri Extractive Metallurgy of Niobium, CRC Press, LLC., Boca Raton, FL, 1994. 

The use of solvating extractants in the recovery of gold and platinum-group metals (PGM) was described in the previous section. These extractants have also found some specialized applications in the extractive metallurgy of base metals. For example, they have been used in the recovery of uranium, the separation of zirconium and hafnium, the separation of niobium and tantalum, the removal of iron from solutions of cobalt and nickel chlorides, and in the separation of the rare-earth metals from one another. 

Powder metallurgy techniques have been used to produce a very wide range of compacts containing molybdenum disulphide in such metals as mixed iron-palladium, iron-platinum , tantalum , iron-tantalum , molybdenum-tantalum , and molybdenum-niobium . The concentration of molybdenum disulphide in these compacts has risen to 90% compared with less than 35% in earlier materials. Composites containing nickel were found to be unsatisfactory because of high friction and wear. 

Martynenko, V. M., and Borovinskaya, I. P., Some characteristic features of the combustion in system niobium-carbon. In Combustion Processes in Chemical Engineering and Metallurgy (Russ.) (A. G. Merzhanov, ed.). USSR Academy of Science, Chemogolovka, Russia, 1975, p. 127. 

Among the pentavalent elements, the most important are niobium and tantalum. Niobium is an excellent material for surface treatment of steel materials for chemical industry due to its high hardness and corrosion-resistance in wet acidic conditions. Nowadays, niobium is also used for the preparation of superconductor tapes and it is used in other branches of industry, for instance in nuclear technology and metallurgy. Tantalum is also of similar importance. For these applications, it is necessary to prepare high purity metal. Molten salt electrolysis, as an alternative process to classical thermal reduction, provides niobium and tantalum with required quality. In order to optimize these processes, it is necessary to know details of both complex formation and redox chemistry of the species present in the melts. 

The method involving the Mo-V-P acid has been used in determinations of phosphorus in biological tissues [127], plant material [128], fruits [129], fish products [130], foodstuffs [131], phosphate minerals [132], cast iron and steel [133,134], niobium, zirconium and its alloys, titanium and tungsten, aluminium, copper, and white metal [135], nickel alloys [134,135], metallurgy products [136], molybdenum concentrates [137], silicon tetrachloride [7], cement [138], and lubricants[139]. The flow injection technique has been applied for determining phosphate in minerals [140] and in plant materials [141]. 

USE In ferrous metallurgy Ferroniobhim (produced by silicon reduction of columbite) is used to alloy stainless steels and metals for welding rods. In niobium base alloys lor high temps and nuclear reactions. Niobium has some use as a getter in electronic vacuum tubes. 

---