Platinum Metals Rev., 1969, 13, (3), 110
Glass Sheathed Rhodium and Iridium Filaments
- A. S. D.
Molten metals and alloys can, when contained within a viscous glass tube, be drawn directly to exceedingly fine wires. For several years this technique has been largely confined to copper and copper base alloys which are conveniently handled in borosilicate glass, this remaining as an integral glass skin in place of the conventional organic enamel insulation.
Few attempts have been made to draw fine refractory metals in this way because of the shortage of suitable glasses. A recent report from the Frankfurt branch of Battelle, (K. H. Grunthaler, J. Nixdorf and H. Rochow, Metall, 1969, 23, (4), 310–314) indicates, however, that this problem may now have been solved. Rhodium wire drawn direct from the melt had a blemish-free surface and at diameters of the order of 15 microns retained sufficient ductility for subsequent deformation. The higher temperatures needed for iridium production necessitated improved induction heating equipment.
The technical problems associated with the selection and/or development of a glass capable of behaving viscously and yet containing molten rhodium at temperatures above 2000°C are not discussed in this paper which, surprisingly enough, does not mention whether the residual glass skin adhered to or spalled off the solidified rhodium wire.