GB645682A - Metallurgical processes for producing materials or articles of platinum or allied metals, or their alloys, and materials or articles made 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 class with or without alloying ingredients in amounts yielding cold-working alloys with alumina, the quantity of which 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 into the form of a wire or sheet suitable for use in the production of desired articles. The alumina may be partly replaced by one or more other oxides which are stable at the sintering temperature whether or not the sintering process is carried out in the presence of hydrogen or other reducing gas, the major part of the total oxide content being alumina. The agglomerate may consist mainly of platinum alloyed with rhodium, palladium, iridium, ruthenium or tungsten, e.g. 5-30 per cent of rhodium, the proportion of oxide being 0.01-1.0 per cent of the weight of the metal, or tungsten in the range of 1-8 per cent of the platinum and about 0.2 per cent of oxide. One of the following binary alloys may be used in the agglomerate, namely platinum alloyed with rhodium up to 30 per cent of the alloy, iridium up to 30 per cent of the alloy, ruthenium up to 15 per cent of the alloy, tungsten up to 8 per cent of the alloy, gold up to 15 per cent, molybdenum up to 8 per cent, manganese up to 8 per cent, cobalt up to 15 per cent or nickel up to 15 per cent. The process may be carried out in the following manner. Ammonium chloroplatinate containing 90 grammes of platinum is suspended in 100 c.c.s. of distilled water. To this is added 10 grammes of rhodium in the form of ammonia hexachlororhodate and 0.25 grammes of alumina in the form of aluminium hydroxide. The resultant paste is dried with constant stirring and heated to about 350 DEG C to decompose the mixture to metal and alumina, and finally to about 600 DEG C. The product is crushed and heated in hydrogen at about 850 DEG C to reduce any rhodium oxide. The resultant powder is sieved, pressed at about 30 tons per square inch and sintered at about 1400 DEG C-1500 DEG C in hydrogen for about 1 hour. The agglomerate may be used in the production of sparking plug electrodes, thermo-couples, electric-furnace heating elements and wire gauzes or the like for use as catalysts in chemical operations.