The use of electric current to activate the consolidation and reaction-sintering of materials is reviewed with special emphasis of the spark plasma sintering method. The method has been used extensively over the past decade with results showing clear benefits over conventional methods. The review critically examines the important features of this method and their individual roles in the observed enhancement of the consolidation process and the properties of the resulting materials.

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1000 at 1000: The effect of electric field and pressure on the synthesis and consolidation of materials: a review of the spark plasma sintering method.

The phenomenal increase during the past decade in research utilizing pulsed electric current to activate sintering is attributed generally to the intrinsic advantages of the method relative to conventional sintering methods and to the observations of the enhanced properties of materials consolidated by this method. This review focuses on the fundamental aspects of the process, discussing the reported observations and simulation studies in terms of the basic aspects of the process and identifying the intrinsic benefits of the use of the parameters of current (and pulsing), pressure, and heating rate.

Electric Current Activation of Sintering: A Review of the Pulsed Electric Current Sintering Process

IN view of the interest attaching to the vaporisation and diffusion of solids, the following observations may be worthy of record.

The Diffusion of Solids

Modeling and experimental analyses were carried out to investigate current and temperature distributions under typical spark plasma sintering (SPS) conditions. The simulation utilized two sample materials with widely differing electrical conductivities, alumina and copper. Current and heat generation gradients were evaluated in the radial and axial directions for both cases. Radial gradients result in significant differences in temperature between the surface of the graphite die and its center, in agreement with experimental measurements. Axial gradients are shown to influence the homogeneity of the product.

Fundamental investigations on the spark plasma sintering/synthesis process: II. Modeling of current and temperature distributions

The characteristics of pulsing patterns in the SPS process were investigated, and the effect of pulsing on the reactivity between Si and Mo was determined Pulsing patterns were composed of consecutive 3 ms peaks separated by a period of no current The peaks (voltage) increased in magnitude with an increase of the “off” time relative to the “on” time The RMS value of the current was constant with changes in the pattern, indicating that this value is the governing condition to the power dissipation and thus temperature Pulsing effects on the reactivity between layers of Si and Mo were investigated The direction of the current had no effect on the thickness of the product layer More importantly, the growth rate of the product formed at 1070, 1170 and 1270 °C was independent of the pulse pattern, in the range studied in this work

Fundamental investigations on the spark plasma sintering/synthesis process: I. Effect of dc pulsing on reactivity

The influence of high dc currents (up to 1019 A cm−2) on the interaction between thin Au-Al layers was investigated over the temperature range 400-500°C In contrast with earlier diffusion couple results, only four of the five intermetalllic compounds in this system were observed, in both the absence and the presence of a current at all levels The intermetallics Au5 Al2 and Au2 Al were the dominant products while AuAl and AuAl2 were relatively insignificant The latter showed little change, growing only to a total thickness of a few micrometres, regardless of the magnitude of the current density and time of annealing While the sequence of formation of the different intermetallics was not affected by the current, the incubation time and rate of growth of the layers were strongly influenced The incubation time for the appearance of a measurable product layer was markedly reduced by the current, by nearly two orders of magnitude in some cases The effect of the current on the nucleation of the pr

U. Anselmi-Tamburini

Papers

High-flux current effects in interfacial reactions in Au–Al multilayers