The Element Niobium

Hatchett never isolated the metal columbium from its oxide. Nor could Rose prepare niobium in metallic form. This is not surprising. No matter what name it was given, the element was very tightly bound to oxygen. C. W. Blomstrand, professor at the University of Lund in southern Sweden was probably the first to see the metaL In 1864 he heated niobium chloride in an atmosphere of hydrogen and got steel-gray niobium with a metallic luster. 

In 1906 Werner von Bolton at Siemens Halske in Germany manufactured niobium by the aluminothermic method and purified it by repeated re-melting in a vacuum furnace. 

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The element niobium is often called columbium (Cb) in engineering applications. 

Rose s most important discovery was of the element niobium. Hatchett had shown that the hydrated oxide of columbium (Nb205) which he obtained from columbite differed from Ekeberg s tantalic acid (Ta20s) in being easily soluble in alkali carbonate, whilst tantalic acid is less easily soluble but after Wollaston s unfortunate paper (see Vol. Ill, p. 706) it was thought that the... 

Sir Hans Sloane (1660-1753) in London was an active man of science, president of the Royal Society and editor of the distinguished journal Philosophical Transactions. He was also an interested collector. Books, pictures, coins and minerals from his collection were placed at the disposal of the British Museum. Sir Hans had close contact with John Winthrop Jr in Connecticut, who in 1734 was elected as a member of the Royal Society. John donated more than six hundred specimens of minerals from New England, which were incorporated in the mineralogical collection of the British Museum. This turned out to be of great importance in the history of element discoveries. At the beginning of the 19 century the element niobium, or columbium as it was called, was discovered in the mineral collection from New England. 

The element is found in niobite (or columbite), niobite-tantalite, parochlore, and euxenite. Large deposits of niobium have been found associated with carbonatites (carbon-silicate rocks), as a constituent of parochlore. Extensive ore reserves are found in Canada, Brazil, Nigeria, Zaire, and in Russia. 

It is used in arc-welding rods for stabilized grades of stainless steel. Thousands of pounds of niobium have been used in advanced air frame systems such as were used in the Gemini space program. The element has superconductive properties superconductive magnets have been... 

Separation of tantalum from niobium requires several complicated steps. Several methods are used to commercially produce the element, including electrolysis of molten potassium fluorotantalate, reduction of potassium fluorotantalate with sodium, or reacting tantalum carbide with tantalum oxide. Twenty five isotopes of tantalum are known to exist. Natural tantalum contains two isotopes. 

Niobium, discovered by Hatchett ia 1801, was first named columbium. In 1844, Rosed thought he had found a new element associated with tantalum (see Tantalum AND tantalum compounds). He called the new element niobium, for Niobe, daughter of Tantalus of Greek mythology. In 1949, the Union of Pure and Apphed Chemistry setded on the name niobium, but in the United States this metal is stiU known also as columbium. Sometimes called a rare metal, niobium is actually more abundant in the earth s cmst than lead. 

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

The elements that decrease the extent of the austenite field include chromium, siUcon, molybdenum, tungsten, vanadium, tin, niobium, phosphoms, aluminum, and titanium. These are known as ferrite stabilizers. 

The important (3-stabilizing alloying elements are the bcc elements vanadium, molybdenum, tantalum, and niobium of the P-isomorphous type and manganese, iron, chromium, cobalt, nickel, copper, and siUcon of the P-eutectoid type. The P eutectoid elements, arranged in order of increasing tendency to form compounds, are shown in Table 7. The elements copper, siUcon, nickel, and cobalt are termed active eutectoid formers because of a rapid decomposition of P to a and a compound. The other elements in Table 7 are sluggish in their eutectoid reactions and thus it is possible to avoid compound formation by careful control of heat treatment and composition. The relative P-stabilizing effects of these elements can be expressed in the form of a molybdenum equivalency. Mo (29) ... 

The elements of Group 5 are in many ways similar to their predecessors in Group 4. They react with most non-metals, giving products which are frequently interstitial and nonstoichiometric, but they require high temperatures to do so. Their general resistance to corrosion is largely due to the formation of surface films of oxides which are particularly effective in the case of tantalum. Unless heated, tantalum is appreciably attacked only by oleum, hydrofluoric acid or, more particularly, a hydrofluoric/nitric acid mixture. Fused alkalis will also attack it. In addition to these reagents, vanadium and niobium are attacked by other hot concentrated mineral acids but are resistant to fused alkali. 

This particular difference in the Lewis acidity of tantalum and niobium complexes provides the possibility of an effective separation between the elements using liquid-liquid extraction. It is obvious that tantalum will extract into the organic phase at a lower acidity of the aqueous solution, whereas niobium will require a higher level of acidity in order to be extracted. The stripping of the elements from the organic phase into the aqueous phase will take place in reverse order. 

First, it is important to note that complete fluorination of the elements ensures an effective separation process. Particularly, Maiorov and Nikolaev [477] developed and reported on the conversion of tantalum, niobium and titanium sulfates and chlorides into their respective fluorides. It was shown that such conversion leads to significant improvement in/enhancement of the separation of the elements. 

The composition of solutions that are used for washing and stripping of extracts is also different and is adjusted for each specific case however, some common conditions can be noted. It is recommended that the extract obtained following collective extraction, which contains both tantalum and niobium, be washed (scrubbed) using sulfuric acid solutions that contain at least 6 mol per liter of H2SO4. Collective stripping of the elements, on the other hand, can be... 

Although the elements tantalum and niobium were discovered more than 200 years ago in the form of oxides, the true beginning of the chemistry of tantalum and niobium was the discovery and investigation of complex fluorotantalates and fluoroniobates of alkali metals. Application of complex fluoride compounds enabled the separation of tantalum and niobium and in fact initiated the development of the industrial production of the metals and their compounds. 

The two rare earth elements niobium (Nb) and tantalum (Ta) were the main subject of study in the investigation referred to. Both elements have very similar properties and almost always occur together in our solar system. However, the silicate crust of the Earth contains around 30% less niobium (compared to its sister tantalum). Where are the missing 30% of niobium They must be in the Earth s FeNi core. It is known that the metallic core can only take up niobium under huge pressures, and the conditions necessary for this may have been present on Earth. Analyses of meteorites from the asteroid belt and from Mars show that these do not have a niobium deficit. 

For niobium and cobalt clusters structures have been proposed based upon the elements behavi or (71). Niobium s specific inertness has been associated with structures that are analogous to close-packed surface of W(110) which also has an activation barrier for hydrogen chemisorption. Since the IPs are also expected to be higher for closed packed structures these two sets of observations are in agreement. This model at its current stage of development requires different structures for each system and as yet has not been useful in making predictions. 

ISOTOPES There are 49 isotopes of niobium, ranging from Nb-81 to Nb-113. All are radioactive and made artificially except nloblum-93, which Is stable and makes up all of the element s natural existence In the Earth s crust. 

However, the story does not end there. It was not until 1844 when Heinrich Rose (1795-1864) rediscovered the element by producing two similar acids from the mineral niobic acid and pelopic acid. Rose did not reahze he had discovered the old columbium, so he gave this new element the name niobium. Twenty years later, Jean Charles Galissard de Marignac (1817—1894) proved that niobium and tantalum were two distinct elements. Later, the Swedish scientist Christian Wilhelm Blomstrand (1826—1899) isolated and identified the metal niobium from its similar twin, tantalum. 

The element was discovered in 1801 by British chemist Charles Hatchett during analysis of a black mineral sample from the British Museum, originally sent in 1753 from Connecticut. He named the element columbium, after the country of its origin, Columbia (United States). In 1844, Rose announced the discovery of a new element which he named as niobium, in honor of Niobe, the daughter of Tantalus, the mythological Goddess of Tears. Later, it was established that Hatchett s columbium and Roses niobium were the same element. Both names remained in use for more than one hundred years. In 1949 at the Fifteenth International Union of Chemistry Congress held at Amsterdam, the name niobium was officially adopted as the international name. 

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