Reactive Spark Plasma Sintering: Successes and Challenges of Nanomaterial Synthesis

Dina V Dudina,Amiya K Mukherjee

doi:10.1155/2013/625218

Abstract

Spark plasma sintering (SPS), initially developed as an advanced sintering technique for consolidating nanopowders into nanostructured bulk materials, has been recently looked at in much broader perspective and gained a strong reputation of a versatile method of solid state processing of metals, ceramics, and composites. The powders in the SPS-dies experience the action of pulsed electric current and uniaxial pressure; they are heated at very high rates unachievable in furnace heating and sintered within shorter times and at lower temperatures than in conventional methods. The principle of SPS and convenient design of the facilities make it attractive for conducting solid state synthesis. In this paper, based on our own results and the literature data, we analyze the microstructure formation of the products of chemical reactions occurring in the SPS in an attempt to formulate the requirements to the microstructure parameters of reactant mixtures and SPS conditions that should be fulfilled in order to produce a nanostructured material. We present successful syntheses of nanostructured ceramics and metal matrix composite with nanosized reinforcements in terms of microstructure stability and attractive properties of the materials and discuss the challenges of making a dense nanostructured material when reaction and densification do not coincide during the SPS. In the final part of the paper, we provide an outlook on the further uses of reactive SPS in the synthesis of nanostructured materials.

Highlights

Spark plasma sintering (SPS) has attracted enormous interest from researchers and engineers in the past two decades such that it is difficult to imagine the development of modern materials science without the advantages offered by this method
SPS uses a combination of uniaxial pressure and pulsed direct current to heat and sinter the powder specimen placed in a die usually made of graphite [1]
As in other reactive sintering processes, when new phases form during the SPS, such factors as uniformity of distribution of the reactants in the mixture, heat release during exothermic reactions, specific volume change and the presence of reaction byproducts need to be taken into account when the microstructure evolution of the synthesized product is traced

Summary

Introduction

Spark plasma sintering (SPS) has attracted enormous interest from researchers and engineers in the past two decades such that it is difficult to imagine the development of modern materials science without the advantages offered by this method. Researchers became intrigued by a possibility of making nanostructured materials by chemical reactions conveniently placing solid reactants in a SPS-die and subjecting them to pulsed current. As in other reactive sintering processes, when new phases form during the SPS, such factors as uniformity of distribution of the reactants in the mixture, heat release during exothermic reactions, specific volume change and the presence of reaction byproducts need to be taken into account when the microstructure evolution of the synthesized product is traced. In addition to factors common to all reactive processes, there are specific features of the microstructure development during the reactive SPS, which are related to the use of electric current: the changes in electrical conductivity of the material during the course of reaction and the presence of hightemperature regions at the inter-particle contacts serving as reaction initiation zones

SPS-Dies as Chemical Reactors

Challenges of Producing Dense Nanomaterials by Reactive SPS

Outlook

Conclusions