ジルコニウム

外観

灰黒色の粉末(水中浸漬品)

溶解性

水に不溶。塩酸、硫酸、硝酸及び水酸化ナトリウム溶液に溶けない。王水及びふっ化水素酸に徐々に溶け、二硫酸カリウムと溶融すると可溶化する。

解説

ジルコニウム，元素記号 Zr ，原子番号 40，原子量 91.224。周期表4族に属する。天然には比較的豊富に存在し，地殻中の平均存在量 165ppm，海水中の存在量 0.02 μg/l 。鉱物としてはジルコン，バッデリ石などがあり，しばしば希土類元素鉱物のモナズ石に伴って産する。 1789年ドイツの化学者 M.H.クラプロートによって発見，1824年 J.J.ベルセーリウスによって単離された。単体は灰白色の光沢ある金属。融点 1900℃，比重 6.52。酸，アルカリに対し安定であるが，フッ化水素酸，王水，熱リン酸と反応する。粉末は発火点が低く，酸化剤と混ぜると爆発しやすい。純ジルコニウムは熱中性子の吸収断面積が金属中最小であるから，原子炉構造材料として繁用される。耐酸，耐食性が強いため，各種の機械用に，またゲッター，鉄鋼の脱酸剤，耐酸合金成分などとして用いられる。酸化物は白色顔料，耐火材料などに供される。

主な性質

1. 金属ジルコニウムは銀白色（電気炉中で酸化ジルコニウムを還元して得られる無定型ジルコニウムは黒色粉末である）
2. ジルコニウムは低温では広範囲な化学物質とは反応せず、耐食性は優れている（高温では空気中で徐々に酸化され、また窒素気流中において水と反応する）
3. 酸素分子、水素分子、窒素分子を非常に良く吸着する。１，０００℃では多くの酸素を吸着し体積膨張する
4. ジルコニウムは天然の金属中で中性子を最も吸収しにくい金属

用途

原子炉の被覆管、チャンネルボックス、耐蝕耐熱用合金、酸化ジルコニウム (電子材料、センサー、ガラス、耐火物、窯業顔料、研磨研削剤) 原料 (化学工業日報社)

その他の用途としては、上質紙のコート材、吸着剤、塗料乾燥剤、溶射材料、 耐火材、研削研磨材、窯業用顔料などがある。これらの用途の中で、ファインセラミックス原料は高純度 で粒径や粒度分布が高度に制御された材料で、イットリアを部分安定化剤として添加したイットリア部分 安定化ジルコニアは、構造用セラミックスとして、人工陶歯や光コネクタフェルール、粉砕メディア、刃物な どの用途で使用されている。また、スカンジア（Sc2O3）を安定化剤として添加したスカンジア安定化ジルコ ニアは、固体酸化物燃料電池（SOFC）の電解質として使用されている。自動車用排ガス助触媒に用いら れているセリア安定化ジルコニアは、高温環境下において助触媒としてのセリウムの活性が落ちないよう にする役割を持っている。 その他に、金属ジルコニウム及び合金は市場が小さいものの、耐食性が高く金属の中で中性子を最も 吸収しにくいなどの性質から、原子力燃料被覆管（ジルカロイ）、原子力燃料の再処理施設等、原子力関 連機器を中心として化学・医療用機器、超電導材料などにも使用されている。また、すぐれた耐食性から 化学工業分野では耐食性材料として利用される。

主な用途

1. 耐火物（鉄鋼用耐火レンガ）
2. ジルコニア含有製品（電子材料部品、窯業顔料、酸素センサー）
3. ジルカロイ製品（原子力燃料被覆管）
4. 合金添加物（ヘリコプター）

使用上の注意

ハフニウムを約2%含有する。ジルコニウム粉末は空気中で発火しやすいので水中に保存してある。もし乾燥して使用する場合はアルゴン又は窒素気流中で行い、等防具の着用、周囲の状況等に十分注意すること。

説明

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.

化学的特性

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.

物理的性質

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.

同位体

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.

名前の由来

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.”

天然物の起源

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.

特性

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.

使用

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.

定義

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.

一般的な説明

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

空気と水の反応

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 .

反応プロフィール

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].

危険性

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.

健康ハザード

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.

火災危険

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.

安全性プロファイル

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.

製法

ジルコン鉱石は、タイルや煉瓦などのジルコン質耐火物に使われるとともに、二酸化ジルコニウム（ジ ルコニア）の原料になる。二酸化ジルコニウムの精製には乾式と湿式がある。乾式は電融法により、湿式 は水酸化ナトリウムや炭酸ナトリウムとともに加熱処理し、さらに塩酸で抽出ろ過することで得られる粗製 塩類（オキシ塩化ジルコニウム）を加水分解して得られる。乾式は、ほとんど物理的粉砕であることから、不純物の除去は基本的にできない。一方、湿式は顧客 に応じてカスタマイズができ高付加価値製品が多い。

輸送方法

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.

不和合性

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.