GB646004A - Metallurgical processes for producing materials or articles of platinum or allied metals, or their alloys, and materials or articles produced by or from the products of such processes - Google Patents

Abstract

A metallurgical process consists in agglomerating by pressing and sintering metals of the platinum group with or without alloying ingredients in amounts yielding cold-working alloys with chromic oxide, the quantity of which oxide is not greater than 10 per cent by weight of the metal, all the ingredients being in a finely divided condition, the sintered body being subsequently swaged, rolled, drawn or otherwise treated to bring it to the form of wire or sheet suitable for the production of the desired articles. A minor part of the chromic oxide may be replaced by one or more other oxides stable at the sintering temperature whether or not the sintering is carried out in hydrogen or other reducing gas. The following binary alloys may be used, namely, platinum with up to 30 per cent of iridium, palladium or rhodium, or up to 15 per cent of ruthenium gold, cobalt or nickel or up to 8 per cent of tungsten, manganese or molybdenum. In an example 100 c.c.s. of distilled water containing 90 grammes of platinum in the form of a suspension of ammonium chloroplatinate is mixed with 50 c.c.s. of an aqueous solution of ammonium hexachlororhodate containing 10 grammes of rhodium and 10 c.c.s. of an aqueous solution of ammonium chromate containing 0.2 grammes of chromic oxide. The mixture is made up to 200 c.c.s. with distilled water, dried, heated slowly to 350 DEG C to decompose the salts to metal and oxide and then to about 600 DEG C to complete the decomposition. The product is crushed, heated to about 850 DEG C in a stream of hydrogen, sieved, pressed in a steel mould under a pressure of about 30 tons per square inch, sintered in hydrogen at about 1400 DEG C-1500 DEG C for about an hour and treated mechanically to bring it to the form of wire or sheet. A further example is given of the production, in a similar manner, of a composition containing platinum, tungsten and chromic oxide. The product may be used in the production of sparking plug electrodes, thermo-couples, electricfurnace heating elements and wire gauze catalysts. Specifications 645,541, 645,681 and 645,682 are referred to.