Molybdenum.pptx - Molybdenum Extraction process Molybdenum processing Molybdenum(Mo is a white platinum-like metal with a melting point of 2,610

Molybdenum.pptx - Molybdenum Extraction process Molybdenum...

This preview shows page 1 - 4 out of 16 pages.

Molybdenum Extraction process
Image of page 1
Molybdenum processing Molybdenum (Mo) is a white platinum-like metal with a melting point of 2,610 °C (4,730 °F). In its pure state, it is tough and ductile and is characterized by moderate hardness, high thermal conductivity, high resistance to corrosion, and a low expansion coefficient. When alloyed with other metals, molybdenum promotes hardenability and toughness, augments tensile strength and creep resistance, and generally promotes uniform hardness. Small quantities of molybdenum (of 1 percent or less) significantly improve the abrasion resistance, anticorrosive properties, and high-temperature strength and toughness of the matrix material. Molybdenum is therefore a vital addition agent in the manufacture of steels and highly sophisticated nonferrous superalloys. Since the molybdenum atom has the same character as that of tungsten but only about half its atomic weight and density, it advantageously replaces tungsten in alloy steels, allowing the same metallurgical effect to be achieved with half as much metal. In addition, two of its outer electron rings are incomplete; this allows it to form chemical compounds where the metal is di-, tri-, tetra-, penta-, or hexa-valent, making possible a wide variety of molybdenum chemical products. This also is the essential factor in its considerable catalytic properties.
Image of page 2
HISTORY Although the metal was known to ancient cultures, and its mineral forms were confused with graphite and the lead ore galena for at least 2,000 years, molybdenum was not formally discovered and identified until 1778, when the Swedish chemist and pharmacist Carl Wilhelm Scheele produced molybdic oxide by attacking pulverized molybdenite (MoS2) with concentrated nitric acid and then evaporating the residue to dryness. Following Scheele’s suggestion, another Swedish chemist, Peter Jacob Hjelm, produced the first metallic molybdenum in 1781 by heating a paste prepared from molybdic oxide and linseed oil at high temperatures in a crucible. During the 19th century, the German chemist Bucholtz and the Swede Jöns Jacob Berzelius systematically explored the complex chemistry of molybdenum, but it was not until 1895 that a French chemist, Henri Moissan, produced the first chemically pure (99.98 percent) molybdenum metal by reducing it with carbon in an electric furnace, thereby making it possible to conduct scientific and metallurgical research into the metal and its alloys. In 1894 a French arms manufacturer, Schneider SA, introduced molybdenum into armour plating at its works in Le Creusot. In 1900 two American engineers, F.W. Taylor and P. White, presented the first molybdenum-based high-speed steels at the Exposition Universelle in Paris. Simultaneously, Marie Curie in France and J.A. Mathews in the United States used molybdenum to prepare permanent magnets. But it was not until acute shortages of tungsten were provoked by World War I that molybdenum was used on a massive scale to make arms, armour plating, and other military hardware. In the
Image of page 3
Image of page 4

You've reached the end of your free preview.

Want to read all 16 pages?

  • Fall '16

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture