Particles and crystallites under electrical explosion of wires

Abstract

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'.

Magnetic Nanoparticles of (Co_0.94Fe_0.06)_72.5Si_12.5B₁₅ and Fe₇₈Si₉B₁₃ Obtained by Electric Explosion of Amorphous Wires

“…It's known that the structure parameters of a wire affect the particles size. Thus according to the results obtained in [3] the reduction of the grain size of the wire leads to the reduction of particle sizes. In this connection the explosion of a wire without crystal structure is of interest.…”

Controlled synthesis of nanopowders via electrical explosion of wires

“…The specific action integral is easily estimated from the energy (temperature) dependencies of the metal specific resistance or by use of several current oscillograms, in accordance with (2). The values of h e for some of the metals investigated with the current density ~ 10 7 A/cm 2 are presented in TABLE I.…”

“…According to the rising capabilities of various applications, various methods of the ultra-fine powders production and large-scale manufacture are developed and transferred to a technology. Among them the exploding wire method is widely investigated by the researchers and companies of Russia [1], [2], [3], Ukraine [4], Germany [5], Japan [6], India [7], Korea [8], and others. First, systematic investigations have had a good start in Russia in the 70's [9], [10].…”

“…Major properties of the produced powders, for instance, the median size, are considered at least in six-dimensional space of initial conditions. The introduced energy density w, the rate of heating or the current density j, the rate of cooling of expanding medium (i.e., the diameter of a wire d and the density of environment γ), reactivity of environment, and initial microstructure of wire metal are also important factors [1], [2], [3].…”

Effect of Ambient Gas on the Particle Size of Copper Nanopowder Prepared By the Wire Explosion Technique

“…Effect of various experimental parameters of the wire explosion technique on particle size distribution has been investigated by researchers. Among them are: ambient gas [3], ambient pressure [4], deposited energy [5] and initial crystallite size of wire [6]. In this work, effort is made to investigate the effect of nitrogen, argon and their mixture on the particle size for powder produced from wire explosion.…”