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Because tungsten is a rare metal [133] and its compounds are generally inert, the effects of tungsten on the environment are limited. [134] The abundance of tungsten in the Earth's crust is thought to be about 1.5 parts per million. It is the 58th most abundant element found on Earth. [135]
Manufacturers use its alloys with platinum, iridium, and other platinum-group metals to make fountain pen nib tipping, electrical contacts, and in other applications that require extreme durability and hardness. [12] Osmium is among the rarest elements in the Earth's crust, making up only 50 parts per trillion . [13] [14]
Cubic boron nitride is insoluble in iron, nickel, and related alloys at high temperatures, but it binds well with metals due to formation of interlayers of metal borides and nitrides. It is also insoluble in most acids, but is soluble in alkaline molten salts and nitrides, such as LiOH, KOH, NaOH/Na 2 CO 3, NaNO 3 which are used to etch c-BN. [32]
Ferrofluid on glass, with a rare-earth magnet underneath. A rare-earth magnet is a strong permanent magnet made from alloys of rare-earth elements.Developed in the 1970s and 1980s, rare-earth magnets are the strongest type of permanent magnets made, producing significantly stronger magnetic fields than other types such as ferrite or alnico magnets.
Developed independently in 1984 by General Motors and Sumitomo Special Metals, [3] [4] [5] neodymium magnets are the strongest type of permanent magnet available commercially. [ 1 ] [ 6 ] They have replaced other types of magnets in many applications in modern products that require strong permanent magnets, such as electric motors in cordless ...
Of these, three elements (bismuth, thorium, and uranium) are primordial because they have half-lives long enough to still be found on the Earth, [d] while all the others are produced either by radioactive decay or are synthesized in laboratories and nuclear reactors. Only 13 of the 38 known-but-unstable elements have isotopes with a half-life ...
The metal is highly resistant to corrosion by acids: at temperatures below 150 °C tantalum is almost completely immune to attack by the normally aggressive aqua regia. It can be dissolved with hydrofluoric acid or acidic solutions containing the fluoride ion and sulfur trioxide , as well as with molten potassium hydroxide .