Interaction of oxygen with nanocrystalline metals

Nanocrystalline Ni and Fe specimens with a low oxygen content and mass-dens ities up to 98 and 93%, respectively, were produced by gas-phase condensati on. The oxygen contents were determined by nuclear-reaction analysis (NRA) in the as-prepared state and after exposition to different oxygen partial p ressures. NRA measurements in combination with serial sectioning by ion-bea m sputtering show that the penetration of oxygen along open porosity is sup pressed in the case of specimens with a high mass-density. Neither by NRA m easurements nor by secondary-ion mass spectrometry (SIMS), performed after thermal treatments in oxygen in the temperature regime between 100 and 200 degrees C, oxygen penetration can be detected in high-density nanocrystalli ne Ni specimens. This may indicate a low oxygen diffusion in interfaces of n-Ni. However, a low oxygen solubility may not be excluded. (C) 1999 Acta M etallurgica Inc.