Protherm, a beryllium copper alloy that is used for molds in plastic manufacturing, contains 0.4% beryllium and 1.8% nickel.

High strength beryllium copper alloys contain up to 2.7% of beryllium (cast), or 1.6-2% of beryllium with about 0.3% cobalt (wrought). The high mechanical strength is achieved by precipitation hardening or age hardening. The thermal conductivity of these alloys lies between steels and aluminium. The cast alloys are frequently used as material for injection molds. The wrought alloys are designated by UNS as C172000 to C17400, the cast alloys are C82000 to C82800. The hardening process requires rapid cooling of the annealed metal, resulting in a solid state solution of beryllium in copper, which is then kept at 200-460 °C for at least an hour, facilitating precipitation of metastable beryllide crystals in the copper matrix. Overaging is avoided, as an equilibrium phase forms that depletes the beryllide crystals and reduces the strength enhancement. The beryllides are similar in both cast and wrought alloys.

High conductivity beryllium copper alloys contain up to 0.7% beryllium, together with some nickel and cobalt. Their thermal conductivity is better than of aluminium, only a bit less than pure copper. They are usually used as electric contacts in connectors. [2]

[edit] External links

* Standards and properties - Copper and copper alloy microstructures - Copper Beryllium

* National Pollutant Inventory - Beryllium and compounds fact sheet

* National Pollutant Inventory - Copper and compounds fact sheet

Beryllium is not a metal that is often encountered everyday. Although more abundant in the earth's crust than silver, it is more expensive and difficult to produce. The metal itself is very rarely seen, a grey metal formed mainly by powder metallurgy when used as a metal, but more commonly appears as a minor constituent in alloys. Its name comes from the common mineral beryl, which as emerald and aquamarine is an important gemstone, and its chemical symbol is Be. It is also called glucinium, symbol Gl. Glycium and glycinium have been variant spellings.

The oxide was first identified as containing a new element by Haüy (of crystal fame) and Vauquelin in 1797 or 1798 by decomposing beryl. The metal itself was isolated independently by Wöhler and Bussy in 1818, through the reduction of BeCl2 by potassium metal. It was merely a laboratory curiosity until the excellent properties of its alloys with copper were recognized in the 1930's. It was considered a strategic material in World War II because of these alloys.

Mineralogy

Beryllium is a constituent of about 30 identified minerals, but most are rare. The most common beryllium mineral by far is beryl, 3BeO·Al2O3·6SiO2. This is a hard (Mohs 7.5-8.0), relatively light (spgr 2.75-2.80) found in granitic rocks, pegmatites, mica schists and similar environments, occasionally in huge crystals. One crystal was 9 m in length, and weighed 25 tons. Beryl is typically full of inclusions, milky but translucent, and of a greenish color. Clear crystals, which are much smaller but can still be of considerable size, are valuable gemstones. Pure beryl is clear and transparent, but small amounts of impurities color it very attractively. Aquamarine is a fine, pale green-blue, while emerald is deep green due to Cr ion. Because of its color, emerald is the most expensive gemstone, sometimes more costly than diamond. Since the index of refraction of beryl is only 1.580, not much different from that of glass, it does not have the fire or brilliance of diamond and similar gems. However, it is very hard (only corundum, 9, and diamond, 10) are harder. Morganite, a pink to rose beryl, and Golden Beryl, a golden-yellow gem, are less costly than emerald and aquamarine. Usually, the crystals are hand-picked to separate them from the gangue. In ancient times, precious green gems were called smaragdos. This term was applied not only to emerald, but also to malachite.

Currently, most beryllium (93% of world output in 2000) comes from a bertrandite deposit in Juab County, Utah, in Spor Mountain. Bertrandite is Be4Si2O7(OH)2, an alteration product of beryl. It forms clear or white orthorhombic crystals with one plane of good cleavage, is hard (6-7) and of moderate weight (sp.gr. 3.3-3.5; one source says 2.6). The concentrate is sent to Ohio for processing.

Perhaps the most important beryllium mineral after beryl and bertrandite is chrysoberyl, Be(AlO2)2, which at 8.5 is nearly as hard as corundum. Its crystals are orthorhombic, often occurring in pseudo-hexagonal clusters. When of gem quality, chrysoberyl provides alexandrite, with its amazing dichroism, that makes it red when seen from one direction, green from another, and also cat's eye, with inclusions of rutile (TiO2). Another rare beryllium mineral is euclase, named after its perfect cleavage. Its formula is BeAlSiO4(OH). It is a phyllosilicate (layered, like mica; beryl is a 3D tectosilicate), found in granite pegmatites, often with topaz. Due to its hardness (7.5) and durability, it is also found in placers. It may be clear, green or blue.

Nuclear Properties

The atomic number of Be is only 4, and the only naturally occurring isotope has mass number 9, so the nucleus contains 4 protons and 5 neutrons. The atomic weight is 9.012. The isotope with mass number 8, which might be expected to be quite stable with paired-off protons and neutrons, actually splits with a half-life of less than 4 x 10-16 seconds into two alpha particles, which are even more stable. The decay energy is only 90 keV, however. Be8 is the only light nuclide to undergo alpha decay, but it is a very unusual sort of alpha-decay, that is also fission at the same time. Be7 captures an orbital electron (K-capture) to become Li7, half-life 53 days. Be10 is nearly stable, since its half-life is 2 x 106 years against beta-decay to stable B10. These are the only four beryllium nuclides.