Where Found (Encyclopedia of Global Resources)
The known deposits of zirconium constitute 0.028 percent of the Earth’s crust, which is greater than the combined total of all known copper, nickel, lead, tin, zinc, and mercury deposits. reserves of zirconium minerals are found in Australia, Brazil, China, India, South Africa, Ukraine, Sri Lanka, Russia, and Canada. Deposits in the United States are located in Florida, North Carolina, California, Oregon, Colorado, and Idaho. The largest deposits are in Australia and South Africa.
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Primary Uses (Encyclopedia of Global Resources)
Technical Definition (Encyclopedia of Global Resources)
Zirconium (symbol Zr) is a grayish-white, lustrous metal. It is a member of the second series of transition metals in Group IVB in the periodic table of elements.
Zirconium’s atomic number is 40, and its atomic weight is 91.22; it has five stable isotopes and three unstable isotopes. Zirconium has a melting point of 1,852° Celsius, a boiling point of 4,377° Celsius, and a density of 6.506 grams per cubic centimeter.
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Description, Distribution, and Forms (Encyclopedia of Global Resources)
Zirconium occurs in abundance in S-type stars and has been identified in the Sun and meteorites. Zirconium is found in many minerals, such as zircon (zirconium silicate) and baddeleyite (almost pure zirconium dioxide), and it is typically found in igneous rocks (mainly granite and diorite).
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History (Encyclopedia of Global Resources)
Zirconium was discovered by German chemist M. H. Klaproth in 1789, while he was studying some semiprecious stones from Sri Lanka. The name comes from the Arabic word zargun, which means gold color, describing the gemstone now known as zircon. Impure zirconium was first isolated by Jöns Jacob Berzelius by heating a mixture of potassium zirconium fluoride with potassium in an iron tube.
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Obtaining Zirconium (Encyclopedia of Global Resources)
Metallic zirconium is produced commercially by the purification of zirconium tetrachloride by sublimation and reduction of the tetrachloride vapor with molten magnesium (the Kroll process). Unless special separation methods, such as column chromatography, are used in this process, the zirconium produced contains between 0.5 and 3 percent hafnium, chemical element number 72.
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Uses of Zirconium (Encyclopedia of Global Resources)
Because zirconium has a low tendency to absorb slow neutrons and a remarkable resistance to the corrosive environments in nuclear reactors, it finds many uses in the field of nuclear energy. Zirconium and its tin-iron-nickel-chromium alloy (zircaloy) are used as coatings for pipes and fuel element jackets in fission reactor cores. Zirconium is also used in deodorants, surgical instruments, pins, screws for bone repairs, spinnerets for the spinning of rayon fibers, alloys, and powder metallurgy. In powdered form, zirconium is used as an ammunition primer, in smokeless flash powders, in blasting caps, and in the manufacture of vacuum tubes. Various zirconium compounds are used as catalysts for ammonia synthesis, for organic oxidations, for polymerizations, and in the conversion of sulfur dioxide to sulfur trioxide. Along with niobium (columbium), zirconium is a superconductor (it can conduct electricity without any resistance) at low temperatures and is used in the construction of superconducting magnets with potential applications to the generation of electrical power. Baddeleyite, a compound of zirconium and oxygen, can withstand extremely high temperatures. It is used for laboratory crucibles (melting pots for metals) and the linings for certain furnaces.
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Zirconium (Chemical Elements)
Compounds of zirconium have been known for centuries. Yet, the element itself was not recognized until 1789. In that year, German chemist Martin Heinrich Klaproth (1743-1817) discovered the element in a stone brought to him from the island of Ceylon (now Sri Lanka).
Zirconium is one of the transition metals. The transition metals are the elements found in Rows 4 through 7 and between Groups 2 and 13 in the periodic table. The periodic table is a chart that shows how chemical elements are related to each other. Zirconium is located below titanium, which it resembles, in the periodic table. Below zirconium is hafnium, a chemical twin of zirconium.
An important use of zirconium is in nuclear power plants. Its most important compound is zircon, which has a number of industrial applications. Zircon can also be obtained in gemstone quality. A gemstone is a mineral that can be cut and polished and used in jewelry or art.
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Zirconium (How Products are Made)
Zirconium, symbol Zr on the Periodic Table, is a metal most often found in and extracted from the silicate mineral zirconium silicate and the oxide mineral baddeleyite. In its various compound forms, the grayish-white zirconium is the nineteenth most plentiful element in the earth's crust, where it is far more abundant than copper and lead. It belongs to the titanium family of metals, a group that also includes titanium and hafnium and that is favored in industry for its members' good electrical conductivity as well as their tendency to form metallic salts. Because it is stable in many electron configurations and physical states, zirconium can be made into many products. However, since the 1940s, its most significant applications have been in various structural components of nuclear reactors.
Zirconium was discovered by German chemist Martin Heinrich Klaproth, who first isolated an oxide of the mineral zircon in 1789. The first metallic powder was produced in 1824 by a Swedish Chemist, Jons J. Berzelius. The forms of the metal that could be isolated during the nineteenth century, however, were impure and thus very brittle. The earliest method of purifying useable quantities of the metal was developed in 1925 by Dutch chemists Anton E. van Arkel and J. H. de Boer, who invented a thermal iodide process by which they thermally decomposed zirconium tetraiodide. The drawback with van Arkel and de Boer's method was its cost, but twenty years later William Justin Kroll of Luxembourg invented a cheaper process, using magnesium to break down zirconium tetrachloride. Relatively inexpensive, this process produced zirconium in quantities large and pure enough for industrial use.
Since Kroll's breakthrough, zirconium has become an important element in several industries: steel, iron, and nuclear power. It is used in the steel industry to remove nitrogen and sulfur from iron, thereby enhancing the metallurgical quality of the steel. When added to iron to create an alloy, zirconium improves iron's machinability, toughness, and ductility. Other common industrial applications of zirconium include the manufacture of photoflash bulbs and surgical equipment, and the tanning of leather.
Despite its ability to be used for many different industrial applications, most of the zirconium produced today is used in water-cooled nuclear reactors. Zirconium has strong corrosion-resistance properties as well as the ability to confine fission fragments and neutrons so that thermal or slow neutrons are not absorbed and wasted, thus improving the efficiency of the nuclear reactor. In fact, about 90 percent of the zirconium produced in 1989 was used in nuclear reactors, either in fuel containers or nuclear product casings.
Of the two mineral forms in which zirconium occurs, zircon is by far the more important source. Found mainly in igneous rock, zircon also appears in the gravel and sand produced as igneous rock erodes. In this form, it is often mixed with silica, ilmenite, and rutile. The vast majority of the zircon used in industry today originates in these sand and gravel deposits, from which the purest zircon is extracted and refined to be used as zirconium metals. Less pure deposits are used in the form of stabilized zirconia for refractories and ceramic products. The world's largest zircon mines are in Australia, South Africa,
Extraction and Refining
- 1 The sand and gravel that contain zircon mixed with silicate, ilmenite, and rutile are typically collected from coastal waters by a floating dredge, a large steam shovel fitted on a floating barge. After the shovel has scooped up the gravel and sand, they are purified by means of spiral concentrators, which separate on the basis of density. The ilmenite and rutile are then removed by magnetic and electrostatic separators. The purest concentrates of zircon are shipped to end-product manufacturers to be used in metal production, while less pure concentrations are used for refractories.
- 2 End-product manufacturers of zircon further refine the nearly pure zircon into zirconium by using a reducing agent (usually chlorine) to purify the metal and then sintering (heating) it until it becomes sufficiently ductileorkableor industrial use. For small-scale laboratory use, zirconium metal may be produced by means of a chemical reaction in which chloride is used to reduce the zircon.
- 3 The less-pure zircon is made into zirconia, an oxide of zirconium, by fusing the zircon with coke, iron borings, and lime until the silica is reduced to silicon that alloys with the iron. The zirconia is then stabilized by heating it to about 3,095 degrees Fahrenheit (1,700 degrees Celsius), with additions of lime and magnesia totalling about five percent.
- 4 As mentioned above, baddeleyite contains relatively high, pure concentrations of zirconium oxide that can be used without filtering or cleansing. The only refining process used on baddeleyite involves grinding the gravel or sand to a powder and sizing the powder with different sized sieves. All zirconium oxide that comes from baddeleyite is used for refractories and, increasingly, advanced ceramics.
The quality control methods implemented in the production of zirconium metal are typical Statistical Process Control (SPC) methods used in most metal production. These involve tracking and controlling specific variables determined by the end product requirements. Stringent government quality control is applied to all zirconium metal produced for nuclear applications. These controls assure that the zirconium produced for use in a nuclear plant has been processed correctly and also allow for accountability: processing is tracked so that it can be traced back to each individual step and location.
Quality control methods for zirconium used in refractory applications also focus on SPC. However, in the refractory industries, it is also necessary to ascertain the beach (and even what part of the beach) from which the zirconium mineral was extracted. Manufacturers need to know exactly where the zirconium came from because each source contains slightly different trace elements, and different trace elements can affect the end product.
Silicate, ilmenite, and rutilell byproducts of the zircon refining processre typically dumped back in the water at the extraction site. These elements compose typical beach sand and are in no way detrimental to the environment. Magnesium chloride, the only other notable byproduct of zirconium manufacturing, results from the reduction of the zircon with chlorine in the refining process and is typically sold to magnesium refineries. No byproducts or waste result from baddeleyite refining.
Many believe that the future of zirconium lies in its use as an advanced ceramic. Advanced ceramicslso called "fine," "new," "high-tech," or "high-performance" ceramicsre generally used as components in processing equipment, devices, or machines because they can perform many functions better than competing metals or polymers. Zirconium is fairly hard, doesn't conduct heat well, and is relatively inert (i.e., it doesn't react readily with other elements), all excellent qualities for advanced ceramics. Zirconium oxide, manufactured as a ceramic, can be used to make crucibles for melting metals, gas turbines, liners for jet and rocket motor tubes, resistance furnaces, ultra-high frequency furnaces, and refractories such as the facing of a high-temperature furnace wall.
Where To Learn More
Heuer, A. H., ed. Science and Technology of Zirconia. American Ceramic Society, 1981.
Specifications for Zirconium and Zirconium Alloy Welding Electrodes and Rods. American Welding Society, 1990.
Zirconium and Hafnium. Gordon Press Publishers, 1993.
Burke, Marshall A. "Ceramics Enter the Foundry," Design News. June 16,1986, p. 56.
"Fuel Cell's Future Gets a Boost," Design News. August 18, 1986, p. 38.
"Zirconium," Machine Design. April 14, 1988, pp. 234-35.
"Zirconium Holds Down Costs of Making Zirconium," Metal Progress. November, 1983, pp. 11-12.
"Adding Strength to Glassy Ceramics," Science News. September 13, 1986, p. 170.
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