Цирконий

Описание

Zirconium, is a metallic element with a grayish, crystalline scale or gray amorphous powder form. It is flammable or explosive in the form of a powder or dust and as borings and shavings. The powder should be kept wet in storage. Zirconium is a suspected carcinogen, with a TLV of 5 mg/m3 of air and it is insoluble in water. The four-digit UN identification numbers depend on the form and the amount of water present. The number for zirconium, dry, as wire, sheeting, or in the form of strips is 2009. The number for zirconium, dry, as a wire, sheeting, or as strips that are thinner than 254 μm, but not thinner than 18 μm, is 2858. Dry zirconium metal powder is 2008. Wet zirconium powder is 1358. Zirconium metal in a liquid suspension is 1308. The primary uses are as a coating on nuclear fuel rods, photo flashbulbs, pyrotechnics, explosive primers, and laboratory crucibles.

Химические свойства

Zirconium is a grayish-white, lustrous metal in the form of platelets, flakes, or a bluish-black, amorphous powder. It has a negligible vapor pressure, and is insoluble in water, especially as zirconium oxide. The primary valence state is 4+. Zirconium and its alloys react violently with strong acids and are incompatible with strong metal alkalis and strong oxidizers but are inert to most weak acids and alkalis. Pure zirconium powder may explode spontaneously in air, while zirconium hydrides react with water to produce a flammable gas. Zirconium tetrachloride is highly corrosive, which hydrolyzes in water to form zirconyl chloride.

Физические свойства

Zirconium can be a shiny grayish crystal-like hard metal that is strong, ductile, and malleable,or it can be produced as an undifferentiated powder. It is reactive in its pure form.Therefore, it is only found in compounds combined with other elements—mostly oxygen.Zirconium-40 has many of the same properties and characteristics as does hafnium-72, whichis located just below zirconium in group 4 of the periodic table. In fact, they are more similarthan any other pairs of elements in that their ions have the same charge (+4) and are of thesame general size. Because zirconium is more abundant and its chemistry is better knownthan hafnium’s, scientists extrapolate zirconium’s properties for information about hafnium.This also means that one “twin” contaminates the other, and this makes them difficult toseparate.
Zirconium’s melting point is 1,852°C, its boiling point is 4,377°C, and its density is 6.506g/cm³.

Изотопы

Zirconium has 37 isotopes, ranging from Zr-79 to Zr-110. Four of them arestable, and one is a naturally radioactive isotope, with a very long half-life. All five contribute to the element’s natural existence on Earth. The stable isotopes are the following:Zr-90 = 1.45%, Zr-91 = 11.22%, Zr-92 = 17.15%, and Zr-94 = 17.38%. The one naturalradioactive isotope is considered stable: Zr-96, with a half-life of 2.2 × 10+19 years,contributes 2.80% to zirconium’s total existence on Earth. All of the other isotopes are artificially radioactive and are produced in nuclear reactors or particle accelerators. They have half-lives ranging from 150 nanoseconds to 1.53 × 10⁺⁶ years.

Происхождение имени

The name “zirconium” was derived from the Arabic word zargun, which means “gold color.” Known in biblical times, zirconium mineral had several names (e.g., jargoon, jacith, and hyacinth). Later, the mineral was called “zirconia,” and the element was later named “zirconium.”

Вхождение

Zirconium is not a rare element. It is found over most of Earth’s crust and is the 18th mostabundant element, but it is not found as a free metal in nature.
It is found in the ores baddeleyite (also known as zirconia) and in the oxides of zircons,elpidite, and eudialyte.

Характеристики

Zirconium is insoluble in water and cold acids. Although it is a reactive element, it resistscorrosion because of its rapid reaction with oxygen, which produces a protective film of zirconiumoxide (ZrO₂) that protects any metal with which it is coated. Zirconium is best knownas the gemstone zircon. Although there are different types of zircons, the most recognized isthe hard, clear, transparent zircon crystal that has a very high index of refraction, which meansit can bend light at great angles. These zircon crystals (zirconium sulfate, ZrSiO₄) are cut withfacets to resemble diamonds.
Another characteristic that makes zirconium useful is the production of “zircaloy,” whichdoes not absorb neutrons as does stainless steel in nuclear reactors. Thus, it is ideal to makenuclear fuel tubes and reactor containers. Zircaloy is the blend (alloy) of zirconium and anyof several corrosion resistant metals.

Использование

Pure zirconium (hafnium-free) is a valuable structural material for atomic reactors because of its low nuclear cross-section and high corrosion and heat resistance. Because of hafnium's high neutron absorption characteristics, it must be removed from zirconium which is to be used in nuclear reactors; removal unnecessary for other commercial purposes. As an 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.

Определение

zirconium: Symbol Zr. A grey-whitemetallic transition element; a.n. 40;r.a.m. 91.22; r.d. 6.49; m.p. 1852°C;b.p. 4377°C. It is found in zircon (ZrSiO4; the main source) and in baddeleyite(ZnO2). Extraction is by chlorinationto give ZrCl4 which ispurified by solvent extraction and reducedwith magnesium (Krollprocess). There are five natural isotopes(mass numbers 90, 91, 92, 94,and 96) and six radioactive isotopesare known. The element is used innuclear reactors (it is an effectiveneutron absorber) and in certain alloys.The metal forms a passive layerof oxide in air and burns at 500°C.Most of its compounds are complexesof zirconium(IV). Zirconium(IV) oxide(zirconia) is used as an electrolyte infuel cells. The element was identifiedin 1789 by Klaproth and was first isolatedby Berzelius in 1824.

Общее описание

A gray amorphous sludge with not less than 20% water.

Реакции воздуха и воды

May ignite on contact with air or moist air. May burn rapidly with flare-burning effect. Some react vigorously or explosively on contact with water. The severity of the pyrophoric reaction depends a great deal on zirconium particle size, with the finely divided material reacting with the most vigor. The initiation of the explosion has been spark and by electrostatic ignition. Zirconium dusts have been known to explode, [NFPA 482M, 1974], covers all aspects of storage and handling of zirconium, there are 43 abstracts of unusual zirconium fire and explosion incidents. Water Insoluble .

Профиль реактивности

When a mixture of alkali hydroxides and zirconium is heated, the liberated oxygen reacts explosively with zirconium [Mellor 7:116 1946-47]. Chromates, dichromates, sulfates, molybdates, and tungstates of lithium, sodium, potassium, rubdium, and cesium will react violently, even explosively, with an excess of zirconium powder [Ellern 1968. p. 249]. A mixture of hydrated borax and zirconium explodes when heated [Mellor 7:116 1946-47]. An explosion occurred when zirconium sponge was placed in a beaker of carbon tetrachloride [Allison 1969]. Zirconium explodes violently with cupric oxide or lead oxide [Mellor 7:116 1946-47]. A mixture of powdered zirconium and potassium nitrate explodes when heated above the melting point [Mellor 7:116 1946-47].

Опасность

There is disagreement relative to the dangers of the elemental form of zirconium. Some saythat the metal and gemstone forms are harmless, but there is some evidence that the vapors andpowder forms of the metal may be carcinogenic. Also, several zirconium compounds can produceallergic reactions in humans and have proven to be toxic to the skin or lungs if inhaled.
The fine powder and dust of zirconium are explosive, especially in the presence of nonmetalsthat oxidize these forms of zirconium.

Угроза здоровью

The toxicity of zirconium and its compoundshas been found to be of low order. Lethal dosein rabbits when administered intravenouslyis reported as 150 mg/kg (Lewis(Sr) 1996).Inhalation of dust of the metal or its compoundscan form skin and pulmonary granulomasthat may be attributed to reaction ofsensitized T cells with antigen. X-ray studiesin animals indicate retention of the metal inthe lungs. Inhalation may produce irritationof mucous membrane. Skin contact can causeirritation.

Пожароопасность

May react violently or explosively on contact with water. Some are transported in flammable liquids. May be ignited by friction, heat, sparks or flames. Some of these materials will burn with intense heat. Dusts or fumes may form explosive mixtures in air. Containers may explode when heated. May re-ignite after fire is extinguished.

Профиль безопасности

A very dangerous fire hazard in the form of dust when exposed to heat or flame or by chemical reaction with oxidizers. May ignite spontaneously. A dangerous explosion hazard in the form of dust by chemical reaction with air, alkali hydroxides, alkali metal chromates, dichromates, molybdates, sulfates, tungstates, borax, CCl4, CuO, Pb, PbO, P, KClO3, KNO3, nitrylfluoride. Explosive range: 0.16 g/L in air. To fight fire, use special mixtures, dry chemical, salt, or dry sand. See also ZIRCONIUM COMPOUNDS.

Перевозки

UN2008 Zirconium powder, dry, Hazard Class: 4.2; Labels: 4.2-Spontaneously combustible material. UN1358 Zirconium suspended in a liquid, Hazard Class: 3; Labels: 3-Flammable liquid. UN1358 Zirconium powder, wetted with not <25% water (a visible excess of water must be present) (1) mechanically produced, particle size <53 μm; (2) chemically produced, particle size <840 μm, Hazard Class: 4.1; Labels: 4.1-Flammable solid. UN 1932 Zirconium scrap, Hazard Class: 4.2; Labels: 4.2- Spontaneously combustible material. UN 2009 Zirconium, dry, finished sheets, strip or coiled wire, Hazard Class: 4.2; Labels: 4.2-Spontaneously combustible material. UN2858 Zirconium, dry, coiled wire, finished metal sheets, strip (thinner than 254 μm but not thinner than 18 μm), Hazard Class: 4.1; Labels: 4.1-Flammable solid.

Несовместимости

Dust may form explosive mixture with air. Violent reactions with oxidizers, air, alkali hydroxides; alkali metal compounds (such as chromates, dichromates, molybdates, salts; sulfates, and tungstates); borax, carbon tetrachloride; lead, lead oxide; phosphorus, potassium compound s. Incompatible with boron, carbon, nitrogen, halogens, lead, platinum, potassium nitrate. Powder may ignite spontaneously and can continue burning under water. Explodes if mixed with hydrated borax when heated. Fine powder may be stored completely immersed in water.