Niobium, Tantalum and Zirconium

Ferric, molybdenum, titanium, niobium, tantalum, and zirconium compounds also turn curcumin red-brown. However, this color product, unlike that due to boric acid, does not change to blue or green on addition of alkali. 

Vanadium, Niobium, Tantalum and Zirconium Mixed sandwich complexes of vanadium containing arene rings have been described in two reports. The bisindenylbisvanadium complex (41) has been structurally characterised and contains a metal-metal bond length of 2.35A. The complex is formed in the reductive... 

Besides the doped oxides, modified oxides are gained a prominent role in the catalytic scenario. Many different oxide materials were synthesized chemically modifying in particular, but not exclusively, silica stmctures with alumina, titanium, niobium, tantalum, and zirconium giving rise to many successful materials used in catalysis as active phases or support phase [23, 24, 34, 62-67]. 

MIBK is a highly effective separating agent for metals from solutions of their salts and is used in the mining industries to extract plutonium from uranium, niobium from tantalum, and zirconium from hafnium (112,113). MIBK is also used in the production of specialty surfactants for inks (qv), paints, and pesticide formulations, examples of which are 2,4,7,9-tetramethyl-5-decyn-4,7-diol and its ethoxylated adduct. Other appHcations include as a solvent for adhesives and wax/oil separation (114), in leather (qv) finishing, textile coating, and as a denaturant for ethanol formulations. 

Fig. 6.1b) in which twelve inner ligands bridge the edges of the Me octahedron, and six outer ligands occupy apical positions, predominate. These units are found in reduced zirconium, niobium, tantalum, and rare-earth halides, and niobium, tantalum, molybdenum and tungsten oxides [la, 6, 10]. 

No homoleptic isocyanide complexes of niobium, tantalum, titanium, zirconium, and halfnium have yet been synthesized. The vanadium cation... 

The synthesis and characterisation of organophosphide derivatives of other metallic elements continues to attract attention, and the past year has seen further examples of systems involving aluminium , galliumindium " titanium", and zirconium" ". In addition, organophosphide derivatives of niobium , tantalum" , and samariumhave also been described. 

Sergey Serafimovich Berdonosov, Dr. Sci. was born in 1939 in Moscow, Russia. He was a gold medalist at school in 1956 and received an excellence diploma from Moscow State University in 1961. His PhD thesis, defended in 1964, was dedicated to zirconium, hafnium, niobium, tantalum, and protactinium bromides, and his Dr. Sci. thesis (2002) was devoted to the radiochemical studies of desublimation and new approaches to the determination of physicochemical properties of substances and materials. 

Elwell and Wood (39) burn niobium, tantalum and tungsten in a tube furnace at 1200°C. The sample weight is 2 g, 3 g lead being used as flux. For zirconium and hafnium containing alloys, 1 g iron and 2 g bismuth are used as flux. 

Coedo, A. G., Lopez, T. D, and Alguacil, F. (1996). On-line ion-exchange separation and determination of niobium, tantalum, tungsten, zirconium and hafnium in high-purity iron by flow injection inductively coupled plasma mass spectrometry. Anal. Chim. Acta 315(3), 331. 

Nitrogen and carbon are the most potent solutes to obtain high strength in refractory metals (55). Particulady effective ate carbides and carbonitrides of hafnium in tungsten, niobium, and tantalum alloys, and carbides of titanium and zirconium in molybdenum alloys. 

Borides are inert toward nonoxidizing acids however, a few, such as Be2B and MgB2, react with aqueous acids to form boron hydrides. Most borides dissolve in oxidizing acids such as nitric or hot sulfuric acid and they ate also readily attacked by hot alkaline salt melts or fused alkaU peroxides, forming the mote stable borates. In dry air, where a protective oxide film can be preserved, borides ate relatively resistant to oxidation. For example, the borides of vanadium, niobium, tantalum, molybdenum, and tungsten do not oxidize appreciably in air up to temperatures of 1000—1200°C. Zirconium and titanium borides ate fairly resistant up to 1400°C. Engineering and other properties of refractory metal borides have been summarized (1). 

The corrosion behaviour of amorphous alloys has received particular attention since the extraordinarily high corrosion resistance of amorphous iron-chromium-metalloid alloys was reported. The majority of amorphous ferrous alloys contain large amounts of metalloids. The corrosion rate of amorphous iron-metalloid alloys decreases with the addition of most second metallic elements such as titanium, zirconium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, cobalt, nickel, copper, ruthenium, rhodium, palladium, iridium and platinum . The addition of chromium is particularly effective. For instance amorphous Fe-8Cr-13P-7C alloy passivates spontaneously even in 2 N HCl at ambient temperature ". (The number denoting the concentration of an alloy element in the amorphous alloy formulae is the atomic percent unless otherwise stated.)... 

Tantalum, Niobium and Zirconium, Murex Ltd., Rainham, Essex... 

The first experiments on the plasma chemical decomposition of fluoride solutions containing tantalum or niobium to obtain tantalum and niobium oxides were reported about fifteen years ago [524]. Subsequent publications were devoted to further development and expansion of the method for other refractory rare metals such as titanium and zirconium [525 - 532]. 

---