Chemical Fact Sheet
Zirconium
| Chemical Abstract Number (CAS #) | 7440-67-7 |
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| Analytical Methods | 200.7 - 200.8 - 6010 - 6020 |
| Molecular Formula | Zr |
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Synopsis
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Zirconium - (Persian zargun, gold like), Zr; at. wt. 91.224(2); at. no. 40; m.p. 1855 +/- 2 deg C; b.p. 4409 deg C; sp. gr. 6.506 (20 deg C); valence +2, +3, and +4. The name zircon probably originated from the Persian word zargun, which describes the color of the gemstone now known as zircon, jargon, hyacinth, jacinth, or ligure. This mineral, or its variations, is mentioned in biblical writings. The mineral was not known to contain a new element until Klaproth, in 1789, analyzed a jargon from Ceylon and found a new earth, which Werner named zircon (silex circonius), and Klaproth called Zirkonerde (zirconia). The impure metal was first isolated by Berzelius in 1824 by heating a mixture of potassium and potassium zirconium fluoride in a small iron tube. Pure zirconium was first prepared in 1914. Very pure zirconium was first produced in 1925 by van Arkel and de Boer, by an iodide decomposition process they developed. Zirconium is found in abundance in S-type stars, and has been identified in the sun and meteorites. Analyses of lunar rock samples obtained during the various Apollo missions to the moon show a surprisingly high zirconium oxide content, compared with terrestial rocks. Naturally occurring zirconium contains five isotopes. Twenty six other radioactive isotopes and isomers are known to exist. Zircon, ZrSiO4, the principal ore, is found in deposits in Florida, South Carolina, Australia, and Brazil. Baddeleyite, found in Brazil, is an important zirconium mineral. It is principally pure ZrO2 in crystalline form having a hafnium content of about 1%. Zirconium also occurs in some 30 other recognized mineral species. Zirconium is produced commercially by reduction of the chloride with magnesium (the Kroll Process), and by other methods. It is a grayish-white lustrous metal. When finely divided, the metal may ignite spontaneously in air, especially at elevated temperatures. The solid metal is much more difficult to ignite. The inherent toxicity of zirconium compounds is low. Hafnium is invariably found in zirconium ores, and the separation is difficult. Commercial-grade zirconium contains from 1 to 3% hafnium. Zirconium has a low absorption cross section for neutrons, and is therefore used for nuclear energy applications, such as for cladding fuel elements. Commercial nuclear power generation now takes more than 90% of zirconium metal production. Reactors of the size now being made may use as much as a half-million lineal feet of zirconium alloy tubing. Reactor-grade zirconium is essentially free of hafnium. Zircaloy(R) is an important alloy developed specifically for nuclear applications. Zirconium is exceptionally resistant to corrosion by many common acids and alkalis, by sea water, and by other agents. It is used extensively by the chemical industry where corrosive agents are employed. Zirconium is used as a getter in vacuum tubes as an alloying agent in steel, in surgical appliances, photoflash bulbs, explosive primers, rayon spinnerets, lamp filaments, etc. It is used in poison ivy lotions in the form of the carbonate as it combines with urushiol. With niobium, zirconium is superconductive at low temperatures and is used to make superconductive magnets, which offer hope of direct large-scale generation of electric power. Alloyed with zinc, zirconium becomes magnetic at temperatures below 35 K. Zirconium oxide (zircon) has a high index of refraction and is used as a gem material. The impure oxide, zirconia, is used for laboratory crucibles that will withstand heat shock, for linings of metallurgical furnaces, and by the glass and ceramic industries as a refractory material. Its use as a refractory material accounts for a large share of all zirconium consumed. Zirconium of about 99.8% purity is available at a cost of about $170/kg. |
| Use | IN CAST IRON & STEEL MFR. PACIFIER & POLISHING POWDER FOR LENS & TELEVISION TUBES; IN ARC LAMPS; PIGMENT IN PLASTICS. MAKING RAYON SPINNERETS; SUPERCONDUCTIVE MAGNETS; & IN MAKING SURGICAL APPLIANCES. USED AS REFLECTIVE SURFACE AGENT ON SATELLITES; IN ALLOYS TO BE USED IN NONCORROSIVE CHEM APPARATUS. POWDER ALLOYED WITH LEAD IS USED IN CIGARETTE LIGHTER FLINTS. PYROTECHNICS; METAL-TO-GLASS SEALS; SPECIAL WELDING FLUXES; IN ACID MFR PLANTS. Used as a containment material for the uranium oxide fuel pellets in nuclear power reactors. Is particularly useful for this application because of its ready availability, good ductility, resistance to radiation damage, low thermal-neutron absorption cross section 18X10-30 sq m (0.18 barns), & excellent corrosion resistance in pressurized hot water up to 350 deg C. ZIRCALOY IS A IMPORTANT ALLOY DEVELOPED FOR NUCLEAR APPLICATIONS. Pure zirconium (hafnium-free) is a valuable structural material for atomic reactors. Ingredient of priming or explosive mixtures; flashlight powders; as deoxidizer in metallurgy; as "getter" in vacuum tubes; in constructing rayon spinnerets in lamp filaments, flash bulbs. |
| Consumption Patterns | CONSUMPTION OF SPONGE IS MAINLY FOR MILITARY PURPOSES; SUBSTANTIAL AMT FIND USE IN PRIVATE POWDER REACTORS; ALMOST 50 TONS WERE USED IN INDUSTRY UNRELATED TO NUCLEAR POWER (IE, PHOTOGRAPHIC FLASH BULBS). Foundry sands, 47%; Refractories, 22%; Ceramics, 10%; Abrasives, 6%; and misc, 15% (1985). |
| Apparent Color | BLUISH-BLACK, AMORPHOUS POWDER OR GRAYISH-WHITE LUSTROUS METAL (PLATELETS OR FLAKES) OF HEXAGONAL LATTICE BELOW 865 DEG C; BODY-CENTERED CUBIC ABOVE 865 DEG C; GOLD COLOR |
| Boiling Point | 3577 DEG C |
| Melting Point | 1857 DEG C |
| Molecular Weight | 91.22 (atomic wt) |
| Density | 6.49 |
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Sensitivity Data |
Eye irritant |
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Chemical and Physical Properties |
ATOMIC NUMBER 40; VALENCE 3 & 4; CAN ABSORB UP TO 10 ATOMS % OF OXYGEN OR NITROGEN; HAS HIGH CORROSION & HEAT RESISTANCE; ON PROLONGED HEATING THE COMPACT FORM COMBINES WITH OXYGEN, NITROGEN, CARBON & HALOGENS; HAS LOW NUCLEAR CROSS-SECTION; REACTS WITH HYDROFLUORIC ACID, AQUA REGIA & HOT PHOSPHORIC ACID; BRINELL HARDNESS: 85; FIVE NATURALLY OCCURRING ISOTOPES: 90 (51.46%); 91 (11.23%); 92 (17.11%); 94 (17.40%); 96 (2.80%); NOT ATTACKED BY COLD; VERY SLIGHTLY ATTACKED BY HOT, CONCN SULFURIC ACID OR HYDROCHLORIC ACID; NOT ATTACKED BY NITRIC ACID; ATTACKED BY FUSED POTASSIUM HYDROXIDE OR NITRATE. HARD & BRITTLE WHEN IMPURE, COMPARATIVELY SOFT, MALLEABLE & DUCTILE WHEN PURE; HIGHLY RESISTANT TO CORROSION BY ALKALIS, ACIDS (EXCEPT NITRIC). ALLOYS WITH ALMOST ALL METALS EXCEPT MERCURY, ALKALI & ALKALINE EARTH GROUPS; MAX COVALENCY 8, BUT 5, 6 & 7 ARE COMMON; BULK FORM NOT REACTIVE AT ORDINARY TEMP, OXIDIZES READILY AT 700 DEG C, & COMBINES WITH CHLORIDE AT LOWER TEMP; PROBABLY DOES NOT EXIST IN COMPOUNDS AS MONOATOMIC ION, BUT FREQUENTLY FOUND AS CENTRAL ATOM OF COMPLEX ANIONS & CATIONS; FORMS THREE CATEGORIES OF COMPOUNDS: COMPLEX CATIONS, COMPLEX ANIONS, NONIONIZED GROUPS. IT FORMS STABLE CHELATES WITH BIDENTATE LIGANDS; CAN ALSO FORM LABILE INNER-ORBITAL COMPLEXES. Heat of transition: 3.89 + or - 0.08 kJ/mol; Heat of melting: 18.8 =/- 2.1 kJ/mol; Heat of boiling: 573.2 + or - 4.6 kJ/mol; Heat of sublimation @ 298K: 600.8 kJ/mol; Entropy @ 298.15: 38.99 + or - 0.46 K,J (mol.K); Electrical resistivity, zirconium, @ 5 deg C= 43.74 megohms.cm (0.08X10-6). Polycrystalline adiabatic: Young's modulus= 97.1 GPa; shear modulus= 36.5 Gpa; bulk modulus= 954 Gpa (Calculated from single-crystal adiabatic moduli by the Voight method); Poisson's ratio= 0.33; Brinell harness number, HB 90-130; In aq systems, zirconium is always quadrivalent; Massive zirconium oxidizes rapidly above 600 deg C in air. Zirconium is readily attacked by acidic solutions containing fluorides. As little as 3 ppm fluoride ion in 50% boiling sulfuric acid corrodes zirconium at 1.25 mm/yr. EXTREMELY RESISTANT TO THE CORROSIVE ENVIRONMENT. USED EXTENSIVELY BY CHEMISTS. SUPERCONDUCTIVE. Acoustic Properties: Longitudinal wave speed (V) 4700 m/s (meter/second); shear wave speed 2300 m/s; acoustic impedance (Z) 3070 kg/(cm2.s) (kilogram/(square centimeter second)). TETRAVALENT ZIRCONIUM IS MOST STABLE; ITS ELECTROPOSITIVITY & ELECTRONEGATIVITY ARE ABOUT EQUAL. |
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Environmental Fate |
OCCURS AS ZIRCON /ZIRCONIUM ORTHOSILICATE/ (ZRSIO2) /&/ BADDALYTE /OR BADDELEYITE/ (ZRO2), IN ALLUVIAL DEPOSITS DERIVED FROM IGNEOUS ROCKS, IN NEW SOUTH WALES, BRAZIL, SW INDIA. REGARDED AS RARE METAL BUT PRESENT IN EARTH'S CRUST IN AMTS LARGER THAN LEAD, COPPER, ZINC ABOUT 0.22% IN MINERALS MALACON, ZIRKELITE, EUDIALYTE; FREQUENTLY FOUND IN RARE-EARTH MINERALS FOUND IN ABUNDANCE IN S-TYPE STARS IDENTIFIED IN SUN & METEORITES. LUNAR ROCK SAMPLES OBTAINED DURING THE APOLLO MISSIONS TO THE MOON SHOW A SURPRISINGLY HIGH ZIRCONIUM OXIDE CONTENT, COMPARED WITH TERRESTRIAL ROCKS. Because of its very high chemical activity at temperatures only slightly above normal atm temp, the element occurs only in combined states. Of the many radionuclides produced in nuclear and thermonuclear explosions, the primary contributors to exposure of humans are ... Zirconium-95 ... . |
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