レニウム 化学特性,用途語,生産方法
外観
灰色～黒色, 粉末
溶解性
硝酸及び硫酸に溶け、ふっ化水素酸、塩酸及び水に溶けない。うすい硝酸に溶ける。
解説
レニウム，原子番号75の元素．電子配置[Xe]4f 145d56s2の周期表7族遷移金属元素．D.I. Mendeleev(メンデレーエフ)のdvi-マンガン．原子量186.207(1)．天然に安定同位体 185Re(37.40(2)％)と β－ 崩壊(半減期4.12×1011 y)核種 187Re(62.60(2)％)が存在する．質量数160から194までの放射性同位体核種が知られている．レニウム，銀白色の六方最密構造の金属．粉末は黒色または暗灰色．融点3180 ℃，沸点5596 ℃．密度21.02 g cm－3．第一イオン化エネルギー7.76 eV．1.70 K 以下で超伝導．酸化数－1～7で範囲が広い．化学的な性質はマンガンに似ている点もあるが，主要な酸化数は4～7で，Mnの2とは異なる．室温の空気中で安定であるが，300 ℃ 以上で酸化されて揮発性のRe2O7となる．フッ化水素酸，塩酸には不溶，濃硫酸，濃硝酸，過酸化水素に可溶．フッ素と反応してReF6，塩素，臭素とは高温で反応してReX5化合物となる．水銀とアマルガムをつくる．
森北出版「化学辞典（第2版）
主な性質
- レニウムは銀白色の金属であり、融点は大きい。タングステンに次いで２番目に高い。密度も４番目に大きい
- レニウムは乾いた空気中では安定。３５０℃以上の加熱で酸化し、酸化レニウムを生成する
- レニウムはフッ素酸化物及び塩酸には殆んど侵されない。硝酸には速やかに、硫酸にはゆっくり溶けて、過デニウム酸になる
- 単体レニウムは硬度が大きく電気伝導度や熱伝導度も大きい
- ＋６価レニウム化合物は金属酸化物であるにもかかわらず、電気伝導度が非常に高い
用途
超耐熱合金、電子材料。
特長
粉末は酸素気流で少し加熱すると酸化されて酸化レニウム(VII)を生ずる。
応用
おもな用途は，航空機用ジェットエンジン，ガスタービン用ニッケル-ベース超合金と，石油改質用白金-レニウム触媒の成分である．レニウム合金は，そのほか，るつぼ材，電気接点，熱電子放出能力が高いことから電子管材料，質量分析計，真空計などのフィラメントに使用される．
主な用途
- Ｒｔ－Ｒｅ系接触改質触媒（石油精製装置）
- 電子部品材料（ヒーター、フィラメント他）
- 超耐熱合金（火力発電のローターのタービンブレード等）
使用上の注意
不活性ガス封入
化学的特性
Depending on the process used to isolate and process it,
rhenium may appear as a brown-black powder or a silvery
white solid metal. Rhenium is among the least common of the
natural elements comprising 0.5–1 ppb of earth’s crust; it
generally occurs as a trace element in molybdenite, columbite,
gadolinite, and platinum ores. A sulfide mineral of
rhenium, rhenite exists but is very rare.
There are two naturally occurring isotopes, 185 (37%),
which is stable, and 187 (63%), which has a halftime of 10
11
years, and several synthetic radioisotopes whose half-lives
range from ,＜1 μs to 2×10
5 year. Rhenium has 11
valence states that range from 0 to 7.
物理的性質
Rhenium ranges in color from silvery-white to gray to a black powder. It is a rather denseelement. As a refined metal, rhenium is ductile, but because it is rather rare, its properties havenot found many uses. Rhenium does have the widest range of valences. In addition to its commonvalences of 4, 6, and 7, it also has the uncommon valences of 2, –1, and –7.
Rhenium has a high melting point of 3,180°C, a boiling point of 5,627°C, and a densityof 21.04 g/cm
3.
同位体
There are 45 isotopes of rhenium. Only one of these is stable: Re-185, whichcontributes 37.40% to the total amount of rhenium found on Earth. Re-187, which isradioactive with a very long half-life of 4.35×10
+10 years, contributes 62.60% to rhenium’sexistence on Earth. The remaining 43 isotopes are radioactive with relatively shorthalf-lives and are artificially manufactured.
名前の由来
Derived from the Latin word Rhenus, which stands for the Rhine River
in Western Europe.
天然物の起源
Rhenium is the 78th most common element found on Earth, which makes it somewhatrare. During the early twentieth century, it required the processing of about a 1,000 poundsof earth to secure just one pound of rhenium, resulting in a price of about $10,000 per gram.Thus, there were few uses for rhenium. Later in the century, improved mining and refiningtechniques reduced the price. Today, the United States produces about 1,000 pounds of rheniumper year, and the world’s total estimated supply is only about 400 tons.
The main sources of rhenium are the molybdenite and columbite ores. Some rhenium isrecovered as a by-product of the smelting of copper sulfide (CuS) ores. Molybdenum sulfide(MoS
2) is the main ore and is usually associated with igneous rocks and, at times, metallic-likedeposits. Molybdenite is found in Chile, as well as in the states of New Mexico, Utah, andColorado in the United States.
特性
Rhenium is one of the transition elements, which range from metals to metal-like elements.Its chemical and physical properties are similar to those of technetium, which is aboveit in the periodic table. It is not very reactive. When small amounts are added to molybdenum,it forms a unique type of semiconducting metal. It is also noncorrosive in seawater.
使用
Small quantities of rhenium are alloyed with iron to form steel that is both hard and resistantto wear and high-temperatures. Because of its high melting point, rhenium is used inmany applications where long-wearing, high-temperature electrical components are required,such as electrical contacts and switches and high-temperature thermocouples. This physicalquality makes rhenium alloys ideal for use in rocket and missile engines. It is also used to formthe filaments in photographic flash lamps.
Rhenium’s isotope (
187Re) has a very long half-life and decays by both beta and alpharadiation at a very steady rate. This factor makes it useful as a standard to measure the age ofthe universe.
定義
rhenium: Symbol Re. A silvery white metallic transition element;a.n. 75; r.a.m. 186.2; r.d. 20.53; m.p.3180°C; b.p. 5627 (estimated)°C. Theelement is obtained as a by-productin refining molybdenum, and is usedin certain alloys (e.g. rhenium–molybdenum alloys are superconducting).The element forms a numberof complexes with oxidationstates in the range 1–7. It was discoveredby Walter Noddack (1893–1960)and Ida Tacke (1896–1978) in 1925.
調製方法
Among the compounds that can be formed with rhenium
are sulfides, fluorides, chlorides, bromides, iodides, and
oxides. Rhenium(VII) oxide, Re
2O
7, is the most stable
oxide of rhenium. It is formed from rhenium metal powder
or other rhenium oxides in dry air or an oxygen atmosphere
above 350° °C. Re
2O
7 is readily soluble in water, forming
perrhenic acid, HReO4, which forms salts (MReO
4) such as
ammonium perrhenate (NH
4ReO
4). This is an important
starting material, which can be reduced to Re metal and
used for the production of many other rhenium compounds.
Rhenium can also form organometallic compounds such as
carbonyls (e.g., Re
2(CO)
10 and organorhenium compounds
such as hexamethylrhenium, Re(CH
3)
6.
危険性
Rhenium is flammable in powder form. Rhenium dust and powder and many of its compoundsare toxic when inhaled or ingested.
工業用途
The outstanding properties of rhenium and rhenium alloys suggest their use in many specialized applications.Rhenium vs. tungsten thermocouples can be used for temperature measurement and control to approximately 2200 C, whereas previous thermocouple use was limited to temperatures below 1750 C. Indeed, 74% W 26% Re vs. W thermocouples can be used to temperatures of at least 2750 C with a high emf output ensuring accurate precise temperature measurements with excellent reproducibility and reliability.
Rhenium is now widely used for filaments for mass spectrographs and for ion gauges for measuring high vacuum. Its ductility, chemical properties, including the fact that it does not react with carbon to form a carbide, and its emission characteristics make it superior to tungsten for these applications.
Rhenium has received considerable acclaim as an electrical contact material. It possesses excellent resistance to wear as well as arc erosion. Furthermore, the contact resistance of rhenium is extremely stable because of its good corrosion resistance in addition to the fact that possible formation of an oxide film on the contacts would not cause any appreciable change in the contact resistance since the resistivity of the oxide is almost the same as that of the metal. Extensive tests for some types of make-andbreak switching contacts has shown rhenium to have 20 times the life of platinum palladium contacts currently in use.
レニウム 上流と下流の製品情報
原材料
準備製品