Fabrication of thin-walled iridium tubular articles by radial magnetic pulsed compaction and sintering of nanopowder

Abstract

Iridium is rather difficult to process due to its brittleness and sensitivity to impurities. It is better treated while it is clean and fine-grained. Therefore, it should be promising to use fine powders. At the same time, the pressing and sintering of iridium nanopowders has not been studied well. This paper describes a method for manufacturing thin-walled iridium tubes using powder technology. Iridium powder of 99.997% purity with an average particle size of 42 nm (BET) was obtained by the electrolysis of molten salts. It was subjected to radial magnetic pulsed compaction in copper shell, which was subsequently chemically removed. The resulting pressure on the powder here strongly depends on the parameters of the magnetic field pulse and other initial conditions, such as the properties of the shell, the thickness of the charge and the rheological properties of the powder. Therefore, the properties of green and sintered samples were investigated depending on the amplitude of the magnetic pressure, without changing the other parameters. Green bodies with a relative density of up to 50% were obtained with an amplitude of magnetic pressure of 85 –190 MPa. The green density slightly increased with increasing magnetic pressure. Sintering at 1000°C in a hydrogen atmosphere yielded thin-walled tubes with a grain size of 0.3 μm and a density of up to 22.3 g/cm3, close to the theoretical density of iridium, 22.56 g/cm3. The sintered density was insensitive to the green density in the studied range. Solid sintered tubes were obtained by an amplitude of magnetic pressure between 85 and 122 MPa.