Known to ancient civilisations. Copper is a reddish coloured metal which is malleable and ductile. It has excellent thermal and electrical conductivities and good corrosion resistance. It is found in sulphide ores and as carbonate, arsenide and chloride (abundance in the Earth's crust is 50 ppm). Extraction of the metal involves roasting the ore to produce the oxide, followed by reduction and purification by electrolysis. The element is inert to non-oxidising acids but reacts with oxidising agents. In air, it will weather to produce the characteristic green patina of the carbonate. Copper will combine with oxygen on heating to produce CuO at red heat, and Cu₂O at elevated temperatures. Pure copper has an electrical conductivity second only to that of silver and hence its main application is in the electrical industry. Copper is also the basis of many important alloys (e.g. brass, bronze and aluminium bronze) and has been traditionally considered to be one of the coinage metals, along with silver and gold, but being more common, is the least valued. It is one of the first metals ever to have been worked by man and is thought to have been mined for more than 5000 years.
Polvere - Piccole particelle con un'intervallo di dimensioni definito. I materiali descritti come precursori delle leghe non sono leghe vere e proprie, ma sono ottenuti sinterizzando un mix di polveri dei metalli componenti per ottenere la lega per diffusione. La torta risultante è affinata e setacciata per ottenere l'intervallo delle dimensioni delle particelle richiesto. Se non diversamente specificato, le dimensioni della particella mostrata sono solo per guida. Non forniamo alcuna garanzia sulla distribuzione delle dimensioni delle particelle, tra le dimensioni minime e massime quotate o una forma delle particelle specifica.
