Passivation of Compacted Samples Made of Pyrophoric Iron Nanopowders during Their Interaction with Air

Various macrokinetic modes of interaction (self-ignition or combustion) of compact samples from nonpassivated (pyrophoric) and passivated iron nanopowders with air are under study. Experiments show that the modes of interaction with air depend on the type of the used gaseous medium (argon or air), previously containing weighting cups with samples, and on how long the bottles remain in air. The possibility of passivation of pressed samples from pyrophoric iron nanopowder is experimentally established for the first time in the case where the weighting cups with samples remain in air. Various experimental methods are used to investigate the sample heating dynamics and the effect of density inhomogeneity along the length of the sample. It is revealed that pyrophoric samples are heated nonuniformly, although heating begins simultaneously over the entire surface of the sample.