niobium

Nb. Atomic number 41. Electron configuration [Kr] ^4d45s1 . Atomic weight 92.90638(2). A mononuclear element with only one isotope of mass number 93 in nature. Radioactive isotopes with mass numbers 81 ^to 113 are known. In 1801, British C. Hatchett discovered a new metallic element in a mineral called columbite from North America housed in the British Museum and named it columbium, but this was mistaken for tantalum, which occurs together with it. In 1844, German H. Rose revealed that Hatchett's new element was different from tantalum, and named it niobium after Niobe, the daughter of Tantalus in Greek mythology, because the new element occurs together with tantalum. In 1949, niobium was adopted by IUPAC, but the name columbium is still used in the American metal mining industry. The Japanese names for elements are derived from the German names. In his book "Semitsu Kaisyo" published in 1837, Udagawa Yoan called it "Columbium."
It is a relatively widespread element, but its production is small. It is extremely unevenly distributed, with over 90% of the world's reserves in Brazil, followed by Canada. Its abundance in the earth's crust is 11 ppm. It is produced in the form of a niobate salt called columbite, and is also included in rare earth element minerals. It is smelted by alkali fusion, then extracted as a niobate salt, treated with acid, and the niobic acid obtained is dissolved in hydrofluoric acid and separated from tantalum in the form of a fluoro complex salt using a solvent extraction method using isobutyl methyl ketone. The metal is obtained by reducing the oxide with aluminum, sodium, carbon, etc., or by electrolysis of molten fluoride. Historically, it was obtained by reducing chlorides with hydrogen. Metallic niobium is gray-white, soft, and malleable. It belongs to the cubic crystal system. Its density is 8.570 g cm ^-3 . Its melting point is 2468 °C, its boiling point is 4930 °C, and it becomes superconducting below 9.25 K. The work function is small at 3.96 V. Atomic radius 0.143 nm. Ionic radius 0.069 nm (Nb ⁵⁺ , 6-coordinated). 0.074 nm (Nb ⁴⁺ , ​​6-coordinated). Standard electrode potential Nb ³⁺ /Nb -1.1 V. First ionization energy 663.7 kJ mol ^-1 (6.88 eV). In air, it forms an oxide film on its surface and becomes passive, making it extremely stable. At high temperatures, it absorbs hydrogen and becomes brittle. At temperatures above 1000 °C, it reacts with nitrogen to form nitrides. At temperatures above 200 °C, it reacts with chlorine to produce niobium pentachloride. At room temperature, it is inert to water, but reacts with hot steam to produce hydrogen. Soluble in nitric acid and hot concentrated sulfuric acid, slightly soluble in hydrofluoric acid, and insoluble in alkali. Niobium is generally known to have oxidation numbers 2 to 5, with oxidation number 5 being the most stable. In addition to compounds corresponding to these oxidation numbers, compounds corresponding to oxidation number 1, such as (C ₅ H ₅ )Nb(CO) ₄ and [Na((CH ₃ OCH ₂ CH ₂ ) ₂ O) ₂ ][Nb(CO) ₆ ], are also known. Most compounds with a known composition are compounds with the most stable oxidation number of 5, and compounds with lower oxidation numbers are generally extremely unstable. Oxides, niobates, halides, oxyhalides, sulfides, hydrides, nitrides, carbides, silicides, borides, and other complex compounds are known.
Its main uses are in high-tensile steel (for automobiles and ships), stainless steel, and heat-resistant superalloys (for aircraft engines), and it is supplied as an alloy with iron called ferroniobium, which is added to steel. Small condensers (capacitors) made of niobium are used in personal computers and mobile phones, as a substitute for tantalum, which is a scarce resource and has problems with price and supply. It is also used as a high-refractive index high-grade lens material. In addition, Nb ₃ Ge becomes superconducting at 23 K, Nb ₃ Sn at 18.1 K, Nb _0.6 Ti _0.4 at 9.8 K, and Nb itself at 9.25 K. Recently, there has been an increase in demand for it as a material for superconducting magnets for MRI (magnetic resonance imaging) and superconducting accelerating cavities for large accelerators, and there is particularly a large demand for it as a material for superconducting coils for ITER (International Thermonuclear Experimental Reactor). It is designated as a mineral requiring special attention by the Agency for Natural Resources and Energy. [CAS 7440-03-1]

Source: Morikita Publishing "Chemical Dictionary (2nd Edition)" Information about the Chemical Dictionary 2nd Edition

Nb．原子番号41の元素．電子配置[Kr]4d⁴5s¹の周期表5族遷移金属元素．原子量92.90638(2)．天然には，質量数93の同位体のみが存在する単核種元素．81～113の放射性核種が知られている．1801年，イギリスのC. Hatchettが大英博物館所在の北米産のコルンブ石(columbite)と名づけられた鉱物中から新金属元素を発見し，コロンビウムと命名したが，ともに産出するタンタルの間違いであるとされた．1844年，ドイツのH. RoseはHatchettの新元素がタンタルとは別物であることを明らかにし，新元素をタンタルとともに産出することから，ギリシア神話のタンタルスの娘ニオベにちなんでニオブと命名した．1949年，niobiumがIUPACにより採用されたが，最近でもアメリカの金属鉱業界などではコロンビウムという名称も用いられている．日本語の元素名はドイツ語の元素名を採用した．宇田川榕菴は天保8年(1837年)に出版した「舎密開宗」で，格綸彪母(コリュムビウム)としている．
比較的広く存在する元素であるが，産出量は少ない．資源的に極端に偏在していて，ブラジルに世界の埋蔵量の90％ 以上，ついでカナダである．地殻中の存在度11 ppm．コルンブ石としてニオブ酸塩の形で産出するほか，希土類元素の鉱物中に含まれることもある．製錬はアルカリ融解したのち，ニオブ酸塩として抽出し，酸で処理して得たニオブ酸をフッ化水素酸に溶かしてフルオロ錯塩の形でイソブチル=メチル=ケトンを使用する溶媒抽出法でタンタルと分離する．金属は，酸化物をアルミニウム，ナトリウム，炭素などで還元するか，溶融フッ化物の電解によって得られる．歴史的には，塩化物を水素で還元して得られた．金属ニオブは灰白色で軟らかく，展延性をもつ．等軸晶系に属する．密度8.570 g cm^－3．融点2468 ℃，沸点4930 ℃．9.25 K 以下で超伝導となる．仕事関数は3.96 V と小さい．原子半径0.143 nm．イオン半径0.069 nm(Nb^5＋，六配位)．0.074 nm(Nb^4＋，六配位)．標準電極電位 Nb^3＋/Nb－1.1 V．第一イオン化エネルギー663.7 kJ mol^－1(6.88 eV)．空気中では表面に酸化膜をつくって不動態となり，きわめて安定である．高温では水素を吸収してもろくなる．1000 ℃ 以上で窒素と反応して窒化物となる．塩素と200 ℃ 以上で反応して五塩化ニオブを生じる．常温では水に侵されないが，熱水蒸気と反応して水素を発生する．硝酸，熱濃硫酸に可溶，フッ化水素酸に微溶，アルカリに不溶．ニオブには，通常，酸化数2～5が知られており，酸化数5がもっとも安定である．これらの酸化数に相当する化合物のほかに，酸化数1に相当する(C₅H₅)Nb(CO)₄や，[Na((CH₃OCH₂CH₂)₂O)₂][Nb(CO)₆]も知られている．組成の明らかな化合物はほとんどがもっとも安定な酸化数5の化合物で，低酸化数の化合物は一般にきわめて不安定である．酸化物，ニオブ酸塩，ハロゲン化物，オキシハロゲン化物，硫化物，水素化物，窒化物，炭化物，ケイ化物，ホウ化物，そのほか錯化合物などが知られている．
用途は，量的にはほとんど高張力鋼(自動車・造船用)，ステンレス鋼，耐熱超合金(航空機エンジン)用で，鉄との合金フェロニオブの形で供給され，鋼に添加される．希少資源で価格・供給に問題があるタンタルのかわりにニオブを使った小型コンデンサー(キャパシター)がパソコン・携帯電話機用に用いられる．高屈折率高級レンズ材料としても使用される．そのほか，Nb₃Geは23 K，Nb₃Snは18.1 K，Nb_0.6Ti_0.4は9.8 K，Nb自身も9.25 K で超伝導となるので，最近，MRI(磁気共鳴映像法)用超電導磁石や大型加速器用超伝導加速空洞用材料としての需要が加わり，とくにITER(国際熱核融合実験炉)用の超伝導コイル材料としての大口需要がある．資源エネルギー庁・要注視鉱種に指定されている．[CAS 7440-03-1]

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