Particles and crystallites under electrical explosion of wires.

The data produced shed new light on particle formation under fast Joule heating: the particle size depends on the initial size of the crystallites of a metal. The size of crystallites has been determined by the x-ray diffraction method as the size of the region of coherent scattering d(RCS). Median-surface particle sizes d(S) of the powder have been evaluated from the specific surface area S (BET). Such different metals as Al, In, Cu, Ti have been investigated. For the given metals, d(RCS) varies from 25 to 77 nm, d(S) of the powder varies from 45 to 200 nm, and d(S) is the smaller, the smaller is d(RCS). On this evidence, from the beginning of heating, the power of Joule dissipation is higher at the boundaries of crystallites. As a result, even at the energy introduced in the wire equal to the sublimation energy, 'a gas of drops' is formed instead of 'a gas of atoms'.