Passivation of Compact Samples of Nickel Nanopowders and Modes of Their Interaction with Air

It was experimentally shown for the first time that compact samples of pyrophoric nickel nanopowders can be passivated in air for 3–5 s. The passivation of the samples was confirmed by the absence of noticeable heat release during slow heating to 200°C, an insignificant oxygen content according to the data of X-ray powder diffraction analysis and scanning electron microscopy, and the retention of the chemical activity of the samples. The uniform distribution of oxygen throughout the sample suggests the volumetric nature of their interaction with air during the passivation. The critical conditions for heating of passivated samples under which ignition occurs were determined.