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Abstract
Facilities exist at AERE Harwell for the preparation and handling under inert atmospheres of fine metal powders in sizes down to 0·1 μm. Such powders may however require handling in air at some stage and in order to avoid the risk of violent oxidation a test for pyrophoricity of the powder is necessary. Since existing techniques relate only to the case of powders dispersed in air, a simple calorimetric test to determine ignition temperature has been devised. The results can be correlated with particle size for powder prepared by a given route or with the extent of surface oxidation used to passivate an otherwise reactive powder. Some examples of powder preparation and handling are described, in particular the use of a hydride route for fine powder preparation and the relevance of particle size to the behaviour of the powder.