titanium

Ti. Atomic number 22. Group 4 transition element in the periodic table with ^electron configuration [Ar] ^3d24s2 . Atomic weight 47.867(1). Stable isotopes are 46 (8.25(3)%), 47 (7.44(2)%), 48 (73.72(3)%), 49 (5.41(2)%), and 50 (5.18(2)%). Isotopic species with mass numbers 38 to 63 are known. In 1791, W. Gregor of England discovered the mineral rutile in iron sand from Cornwall, and in 1795, MH Klaproth of Germany discovered that rutile was an oxide of a new element and named it titanium after Titan, the giant god in Greek mythology. Udagawa Yoan wrote it as titanium in his book "Semitsu Kaisyu" published in 1837. The Japanese name for this element is based on the German name for this element.
It has been considered a rare element, but is widely distributed. Its abundance in the earth's crust is 5400 ppm. It occurs naturally as rutile (titanium dioxide) TiO ₂ , itatixite (TiO _{2 )} , anthracite (TiO _{2 )} , ilmenite (iron ore) FeTiO ₃ , perovskite CaTiO ₃ , and titanite CaO･TiO ₂ ･SiO ₂ , but the main industrial raw materials are ilmenite and rutile. The proven reserves of ilmenite (1,400 million t), which account for over 90% of titanium demand, are in China (25%), followed by South Africa and India (15% each), and Australia (11%). The Kroll or Hunter process is used for smelting. In the Kroll process, developed in the 1930s, titanium tetrachloride is produced by adding chlorine to red-hot ilmenite or rutile together with carbon, which is then purified by fractional distillation and reduced with metallic magnesium molten at 800-900 °C in helium or argon. The reaction product is evaporated in a vacuum at 1000 °C, and the Mg and _MgCl2 are removed. The resulting product is sponge-like, called titanium sponge, and contains about 99.5% titanium. The sponge is pressed into a shape, welded to make electrodes, and melted by vacuum arc melting to make ingots. Electron beam melting under high vacuum and plasma beam melting in an inert atmosphere are also used. The Hunter process uses metallic sodium as a reducing agent, and in 1910, this process was the first to produce pure metal industrially. Because the sponge produced by this process contains few impurities such as iron and nickel, only small-scale plants for the production of raw materials for electronics products are in operation, but it has been almost entirely replaced by the Kroll process, which is more suitable for reducing costs through large-scale production. To obtain titanium of extremely high purity, the Van Arkel-de Boer process is used, in which titanium iodide (TiI ₄₎ vapor is decomposed on a tungsten filament at 1300 °C. The Kroll process is a batch process and is not suitable for continuous operation. Titanium metal is silver-gray in color and exists in two types, α and β. The α type is a hexagonal crystal system, and at a transition point of 882 °C or higher it becomes the β type with a cubic crystal system. It is paramagnetic. Its density is 4.54 g cm ^-3 (20 °C). Its melting point is 1660 °C and boiling point is 3287 °C. It has excellent strength, heat resistance, and corrosion resistance, and its thermal conductivity and thermal expansion coefficient are small. Its metallic bond radius is 0.145 nm, and its ionic radius is 0.081 nm (Ti ³⁺ , hexacoordinated) and 0.075 nm (Ti ⁴⁺ , ​​hexacoordinated). Its first ionization energy is 6.82 eV, and its oxidation states are -1, 0, 2 to 4. It is most commonly formed as a ^{Ti IV} compound. Titanium is stable at low temperatures, but becomes very active at high temperatures, and directly combines with many nonmetals. In air, it gradually forms a very thin oxide film even at room temperature. At temperatures between 200 and 500°C, the film thickens as the temperature rises, and changes color to brown, dark blue, purple, etc. depending on the thickness. At higher temperatures, the surface first becomes cloudy gray-white, then changes to silver-white and dark gray layers. In oxygen, it burns with a flame at 610°C, becoming _TiO2 . It directly combines with nitrogen at temperatures above 800°C to become titanium nitride TiN. It forms _TiF4 with fluorine at 150°C, and _TiCl4 with chlorine at 300°C. It also forms _TiSi2 with silicon at high temperatures. Powdered titanium absorbs hydrogen. It forms alloys with many metals. It is not attacked by dilute hydrochloric acid or dilute alkali, but dissolves well in hydrofluoric acid as [ _TiF6 ] ^3- .
Metallic titanium has a low specific gravity (about half that of steel) and excellent strength and corrosion resistance, so it is used in pipes and reactors in the petroleum and chemical industries, as well as in the structural materials of jet engines, aircraft, and submarines. Various titanium alloys are made and used in artificial bones and joints, eyeglass frames, golf clubs, and other sporting goods. In Japan, demand for titanium as a metal is less than one-tenth of the total demand. [CAS 7440-32-6][See other terms]Titanium compounds

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

Ti．原子番号22の元素．電子配置[Ar]3d²4s²の周期表4族遷移元素．原子量47.867(1)．安定同位体は46(8.25(3)％)，47(7.44(2)％)，48(73.72(3)％)，49(5.41(2)％)，50(5.18(2)％)．質量数38～63の同位体核種が知られる．1791年イギリスのW. GregorがCornwall産の砂鉄中に鉱物ルチルを発見したが，1795年ドイツのM.H. Klaprothは，ルチルが新元素の酸化物であることを見いだして，ギリシア神話の巨神Titanにちなみチタンと名づけた．宇田川榕菴は天保8年(1837年)出版の「舎密開宗」で知担紐母(チタンニウム)と記載している．日本語の元素名はこの元素のドイツ名による．
希元素の一種と考えられてきたが広く分布している．地殻中の存在度5400 ppm．天然にはルチル(金紅石)TiO₂，イタチタン石TiO₂，鋭すい石TiO₂のほか，イルメナイト(チタン鉄鉱)FeTiO₃，ベロブスカイトCaTiO₃，チタナイトCaO･TiO₂･SiO₂などとして産出するが，主要な工業原料はイルメナイトとルチルである．チタン需要の9割強を担うイルメナイト確認埋蔵量(1400百万t)は中国25％，南アフリカ，インドともに15％，オーストラリア11％ の順である．製錬にはKroll法あるいはHunter法が用いられる．1930年代に開発されたKroll法は，炭素とともに赤熱したイルメナイトまたはルチルに塩素を通じて四塩化チタンを生成させ，これを分別蒸留により精製したのち，ヘリウムまたはアルゴン中で800～900 ℃ に加熱溶融した金属マグネシウムで還元する．反応生成物を1000 ℃ で真空蒸発し，MgとMgCl₂を除去したのちに得られるものは海綿状で，スポンジチタンとよばれ，約99.5％ のチタンを含む．スポンジをプレス成形後，溶接して電極とし，真空アーク溶解法によって溶解してインゴットとする．高真空下の電子ビーム溶解法，不活性雰囲気下のプラズマビーム溶解法も用いられる．還元剤として金属ナトリウムを用いるのがHunter法で，1910年にこの方法によりはじめて工業的に純金属が得られた．この方法によるスポンジは鉄，ニッケルなどの不純物が少ないため，電子工業用製品原料生産の小規模プラントのみが稼働しているが，大規模化によるコストダウンに適したKroll法にほとんど取ってかわられた．きわめて純度の高いチタンを得るには，ヨウ化チタンTiI₄の蒸気を1300 ℃ のタングステンフィラメント上で分解するVan Arkel-de Boer法による．Kroll法はバッチ法で連続運転に適さない．金属チタンは銀灰色，α，βの2型があり，α型は六方晶系，転移点882 ℃ 以上で等軸晶系のβ型になる．常磁性．密度4.54 g cm^－3(20 ℃)．融点1660 ℃，沸点3287 ℃．強度，耐熱性，耐食性にすぐれ，熱伝導率，熱膨張率が小さい．金属結合半径0.145 nm，イオン半径0.081 nm(Ti^3＋，六配位)，0.075 nm(Ti^4＋，六配位)．第一イオン化エネルギー6.82 eV，酸化数－1，0，2～4．Ti^Ⅳ化合物がもっとも多い．低温では安定であるが，高温では非常に活性となり，多くの非金属と直接化合する．空気中では室温でも徐々にきわめて薄い酸化皮膜をつくる．200～500 ℃ では温度上昇にともない皮膜が厚くなり，厚さに応じて褐色，濃青色，紫色などに変色する．さらに高温では表面がまず灰白色に曇り，銀白色，濃灰色層状に変化する．酸素中では610 ℃ で炎をあげて燃えTiO₂となる．窒素とは800 ℃ 以上の温度で直接化合して窒化チタンTiNとなる．フッ素とは150 ℃ でTiF₄を，塩素とは300 ℃ でTiCl₄をつくる．ケイ素とも高温でTiSi₂を生じる．粉末状チタンは水素を吸収する．多くの金属と合金をつくる．希塩酸，希アルカリには侵されないが，フッ化水素酸には [TiF₆]^3－ となってよく溶ける．
金属チタンは比重が小さく(スチールの約半分)，強度，耐食性にすぐれているので，石油および化学産業の配管，反応塔のほか，ジェットエンジン，航空機，潜水艦の構造材料などとして利用される．種々のチタン合金がつくられ，人工骨・関節，眼鏡フレーム，ゴルフクラブなどスポーツ用品に用いられる．金属としての需要は，わが国では全需要の1/10以下である．[CAS 7440-32-6][別用語参照]チタン化合物

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