Discovered in 1797 by N.L. Vauquelin in Paris, but not extracted until 1828 by Wöhler (Berlin) and A.A.B. Bussy (Paris). Beryllium is a light and lustrous metal which is obtained by the electrolysis of a fused halide (e.g. BeCl₂). It is resistant to attack by air or water, even at elevated temperatures (red heat). Beryllium is non-magnetic, is a good thermal conductor and is used as an alloying addition to copper or nickel, the alloys having excellent thermal, mechanical and electrical properties; in addition, when alloyed with nickel, the resultant Be/Ni alloy has the highest coefficient for secondary electron emission (12.3). Applications for pure beryllium include its use as windows in X-ray tubes and as a source of neutrons when bombarded with alpha particles, a technique used by Chadwick in 1932 in their discovery. Beryllium and its compounds are highly toxic, inhalation of the dust resulting in berylliosis, an inflammation of the lungs.
Mesh is available as either a woven wire or electroformed product; in all cases, the quoted aperture sizes are nominal. Wire mesh: a material which is woven from metal wires to provide a thin grid with a regular series of holes. Electroformed mesh: a product made by electroplating the mesh geometry through a mask onto a substrate which is subsequently etched away.