Micropore formation mechanism in iridium coating after high‐temperature treatment

Abstract

Noble metal iridium is of great interest for high-temperature applications and extreme environments. A high (110)-oriented iridium coating was prepared by a double glow plasma process on the surface of niobium substrate. The morphology and composition of the coating were determined by scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy, respectively. The phase of the coating was identified by X-ray diffraction analysis. The misorientation angle distributions of grains on the surface and cross section of the coating were characterized by electron backscatter diffraction system. The uniform and pure iridium coating consisted of the submicrometer-sized columnar grains with high-angle boundary. The mean misorientation angles on the surface and cross section of the coating were 38.6°and 45.6°, respectively. After hightemperature treatment, the coating was composed of equiaxed grains with distinct grain boundaries. Micropores appeared on the fracture surface of the coating. The micropore formation mechanism in Ir coating after high-temperature treatment was investigated.

Effect of Electroplating Variables on Electrodeposition of Ni Rich Ni-Ir Alloys from Citrate Aqueous Solutions

“…4,5,[8][9][10][11][12][13] Ir is a promising candidate for a wide range of applications due to its high melting point, low oxygen permeability, high chemical stability, superior oxidation resistance and electrocatalytic activity performance. [14][15][16][17] Therefore, Ir doped Ni may lead to potential wide use, especially in catalytic and anti-corrosive environment applications. 18,19 Ir-Ni alloy is of particular interest because of the completely miscibility of Ir and Ni and the absence of intermetallic compounds in Ir-Ni isomorphous phase diagram.…”