We continue to review some of the most important materials in heat treatment and metallurgy.
Beryllium (chemical symbol: Be)
Beryllium was discovered as a component of the gemstone beryl, of which emeralds are the best-known type. The gemstones beryl and emerald are both forms of beryllium aluminum silicate. The French mineralogist Abbé René-Just Haüy asked French pharmacist and chemist Nicholas Louis Vauquelin to examine them, and Vauquelin realized they contained a new metal. In February 1798, Vauquelin announced his discovery at the French Academy and named the element glaucinium (Greek glykys = sweet) because its salts taste sweet. Vauquelin also discovered chromium and asparagine, the first amino acid to be isolated. Eventually, the name beryllium gained favor based on the gemstone beryl, and this is now its accepted name.
Beryllium metal was isolated in 1828 by Friedrich Wöhler in Berlin and independently by Antoine-Alexandere-Brutus Bussy in Paris, both of whom extracted it from beryllium chloride by reacting it with potassium. Beryllium is a very light, strong metal. It is six times lighter than steel by weight, and it maintains its shape at high and low temperatures. Beryllium metal is used in the aerospace and defense industries to make lightweight precision instruments and is also used in military aircraft, missiles, space vehicles and communication satellites.
The mirrors of the Spitzer Space Telescope and the James Webb Space Telescope (JWST), which is scheduled for launch in 2018, are made of beryllium and coated with a thin film of gold. The primary mirror of the JWST contains 18 hexagonal segments. Each is 1.3 meters (4.3 feet) in diameter and must maintain its precise contour at temperatures of -240°C (-400°F). Beryllium's stability at low temperature is critical, and its low weight allows the telescopes to be carried into orbit with less fuel.
Beryllium is a critical component of X-ray machines. X-rays are generated by accelerating electrons in a vacuum tube after which they strike a target at the positive side of the tube, emitting X-rays. In order to let the X-rays out of the tube without letting air in, a beryllium window is used. Beryllium is virtually transparent to X-rays but impermeable to air.
Beryllium reflects neutrons, and this property makes it useful in nuclear weapons. It is also employed in the Joint European Torus nuclear-fusion research laboratory (Fig. 1), and it will be used in the more advanced ITER to condition the components that face the plasma. Beryllium is added to copper to make it spark-resistant for tools and other components used in flammable environments and in naval mines due to its nonmagnetic property.
Here are a few scientific and engineering facts about beryllium.
- Atomic number: 4
- Atomic weight: 9.012182
- Density: 1.848 g/cm3
- Melting point: 1287° C
- Boiling point: 2470° C
- Density: 1.848 g/cm3
- Molar volume: 4.8767×10-6
- Brinell hardness: 600 MPa
- Bulk modulus: 130 GPa
- Young modulus: 287 GPa