Baddeleyite - Zirconium Oxide

Zirconium group Baddeleyite Zirconium oxide Colour Index (1911)11990... 

The types of igneous deposits in which commercially important concentrations of apatite have been found are nepheline-seyenite and carbonatites. The world s largest apatite deposit, located in Russia s Kola Peninsula, is associated with nepheline-seyenite. Carbon-atite deposits that are mined for their phosphate content include Siilinjarvi in Finland, Araxa and Jacupiranga in Brazil, and Phalaborwa in South Africa. By-product recovery from carbonatite ores is common. At Siilinjarvi, by-product calcite is recovered for use as agricultural lime, whereas copper concentrate and baddeleyite (zirconium oxide) are byproducts at Phalaborwa. 

Baddeleyite, a naturally occurring zirconium oxide, has been found in the Poco de Caldas region of the states of Sao Paulo and Minas Geraes in Brazil, the Kola Peninsula of the former USSR, and the northeastern Transvaal of the Repubflc of South Africa. BraziUan baddeleyite occurs frequently with zircon, and ore shipments are reported to contain 65—85% zirconium oxide, 12—18% siUca, and 0.5% uranium oxide. Veryhttle of this ore is exported now because all radioactive minerals are under close control of the BraziUan government. 

The Phalaborwa complex ia the northeastern Transvaal is a complex volcanic orebody. Different sections are mined to recover magnetite, apatite, a copper concentrate, vermicuhte, and baddeleyite, Hsted in order of aimual quantities mined. The baddeleyite is contained in the foskorite ore zone at a zirconium oxide concentration of 0.2%, and at a lesser concentration in the carbonatite orebody. Although baddeleyite is recovered from the process tailings to meet market demand, the maximum output could be limited by the requirements for the magnetite and apatite. The baddeleyite concentrate contains ca 96% zirconium oxide with a hafnium content of 2% Hf/Zr + Hf. A comminuted, chemically beneficiated concentrate containing ca 99% zirconium oxide is produced also. 

Zirconium oxide is fused with alurnina in electric-arc furnaces to make alumina—zirconia abrasive grains for use in grinding wheels, coated-abrasive disks, and belts (104) (see Abrasives). The addition of zirconia improves the shock resistance of brittle alurnina and toughens the abrasive. Most of the baddeleyite imported is used for this appHcation, as is zirconia produced by burning zirconium carbide nitride. 

Zirconium oxide (ZrO ) is the most common compound of zirconium found in nature. It has many uses, including the production of heat-resistant fabrics and high-temperature electrodes and tools, as well as in the treatment of skin diseases. The mineral baddeleyite (known as zirconia or ZrO ) is the natural form of zirconium oxide and is used to produce metallic zirconium by the use of the Kroll process. The KroU process is used to produce titanium metal as well as zirconium. The metals, in the form of metaUic tetrachlorides, are reduced with magnesium metal and then heated to red-hot under normal pressure in the presence of a blanket of inert gas such as helium or argon. 

Zirconium oxide occurs in nature as mineral baddeleyite. Ore is mined from natural deposits and subjected to concentration and purifcation by various processes. The oxide, however, is more commonly obtained as an intermediate in recovering zirconium from zircon, ZrSi04 (See Zirconium, Recovery). 

Zirconium oxide, Zr02 is widely known, both as a mineral, baddeleyite, and as an industrial product obtained horn zircon, Z1SO4. Moreover, the precipitate obtained by action of alkali hydroxides upon solutions of tetravalent zirconium is a hydrated oxide. The latter is readily soluble in acids to form oxysalts, which arc usually formulated in terms of the Zr02+ ion, without including its water of hydration, e.g., as Zr0(H2P04)2. The hydrated Zr02+ ion is not amphiprotic it does not dissolve in alkali hydroxides, While it does react on alkali carbonate fusions, the compounds formed have been shown to be mixed oxides rather than zirconates. 

ZrSi04) and baddeleyite, or zirconia or zirconium oxide (Zr02). The amount of zirconium produced in the United States is not reported. That information is regarded as a trade secret. As of 2008, the largest suppliers of zirconium minerals in the world are Australia and South Africa. These two countries produce about 72 percent of the world s zirconium. 

The mineral baddeleyite (Zr02) is found in nature only in small quantities. The main raw material for zirconium oxide ceramics is thus zircon (ZrSi04), from which pure Zr02 is produced by fusing with lime and coke to reduce the Si02 and the impurities. 

Zirconium oxide, or zirconia, occurs as the mineral baddeleyite, but zirconium oxide is obtained commercially mainly via its recovery from zircon. Zircon is treated with molten sodium hydroxide to dissolve the silica. Zirconia is used as a ceramic, but it must be doped with about 10 percent CaO or Y2O3 to stabilize it in its face-centered cubic form. Zirconia is monoclinic, meaning that it has one oblique intersection of crystallographic axes, but it undergoes a phase change at about 1,100°C (2,012°F), its crystal structure becoming tetragonal, and above 2,300°C (4,172°F) it becomes cubic. To... 

Zirconium Oxide. Zircon a, zirconium dioxide zirconic anhydride. OjZr mol wt 123.22. Zr 74.03%, O 25.97%. ZrOj. Occurs in nature as the mineral baddeleyite. Prepn Clark, Reynolds, Ind. Eng. Chem. 29, 711 (1937) ... 

Zirconium oxide n. Zr02. Pigment white 12 (77990). A natural mineral, baddeleyite. Present commercial grades are unsuitable as pigment grade in paint vehicles. Density, 5.68 g/cm particle size, 1.0-2.0 pm refractive index, 2.1-2.2. Syn zirconium dioxide, zirconia, and bad-deleyite. 

Arkelite is a naturally occurring cubic form of zirconium oxide, although it is a rare mineral. The material was first discovered by the German chemist Klaproth in 1789 from the reaction of zircon compounds with alkalis. The natural form is closely related to baddeleyite (q.v.) and is listed with variable oxygen contents (for example, ZrOj 7 and Zr02.i2). It may occur as a minor component in many different rock types. 

Although natural baddeleyite has not been identified as a pigment, its S3mthetic equivalent, zirconium oxide (. v.), is listed as Cl 77990/Pigment White 12. 

Oxides and hydroxides Arkelite (ZrOj.s Zr02,i2) Baddeleyite (Z1O2) Zirconium oxide (Z1O2). 

There are several crystal-structural modifications of zirconium oxide (Zr02), analogues of the minerals arkelite and baddeleyite the latter of these is the form normally encountered as a pigment. Blumenthal and Jacobs (1973) indicate that there were two production methods. The first involves heating zircon (. v.) and carbon at temperatures in excess of 2000°C to form zirconium carbide this would then be burnt in air to form zirconium oxide. In the second process, zirconium salts were precipitated with an alkali sulfate this apparently gives very pure polysulfatopolyzir-conic acids , calcination of which yields the pure oxide. 

Zirconium occurs naturally as a siUcate in zircon [1490-68-2] the oxide baddeleyite [12036-23-6] and in other oxide compounds. Zircon is an almost ubiquitous mineral, occurring ia granular limestone, gneiss, syenite, granite, sandstone, and many other minerals, albeit in small proportion, so that zircon is widely distributed in the earth s cmst. The average concentration of zirconium ia the earth s cmst is estimated at 220 ppm, about the same abundance as barium (250 ppm) and chromium (200 ppm) (2). 

Mixed zircon, coke, iron oxide, and lime reduced together produce zirconium ferrosiUcon [71503-20-3] 15 wt % Zr, which is an alloy agent. Fused zirconia [1314-23-4] has been made from zircon but baddeleyite is now the preferred feed for the production of fused zirconia and fused alumina—zirconia by electric-arc-fumace processing. 

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