Suggested Citation:
Risbud, Subhash H. and Young-Hwan Han (2013) Preface and Historical Perspective on Spark Plasma Sintering. Scripta Materialia 69 (2), 105 - 106

The use of electric current discharge to accelerate the densification of metal and ceramic powders has a rich history in the field of materials processing. While patents on this subject date back to the early 1900s the availability of commercial machines beginning the late 1980s sparked burgeoning research and development activities in applying pulsed electric fields to powders to achieve both very quick consolidation and preserve particle size in the densified micro/nanostructure. The acronyms for this and similar closely related processes have evolved through many incarnations over the past 20 to 25 years. Some of them include plasma activated sintering (PAS), electric pulse assisted consolidation (EPAC), field-activated sintering technique (FAST), pulsed electric current sintering (PECS), and perhaps the most popular of all: Spark Plasma Sintering (SPS). In this VP Set we have chosen this popular term SPS to describe variations of processes which use electric fields to achieve quick sintering. Some of the earliest work on difficult-to-sinter additive-free AlN ceramics was done at UC Davis in the early 1990s by Risbud and his colleagues [1] and [2] using a commercial PAS machine (from Sodick Corporation in Japan). Since that time there has been a prodigious growth in publications on SPS and the effects of electric field application on powder sintering. Excellent comprehensive reviews and commentaries by Munir et al. [3] and [4] and Hungria et al. [5], for example, cover the vastness of this expanding field.

The astonishing versatility of SPS has now been demonstrated for more than 20 years as thousands of materials with a bewildering variety of compositions and structures have been consolidated by hundreds of laboratories around the world. Much of the excitement and interest in SPS is based on compelling evidence that SPS indeed is a highly effective way of producing bulk samples with pre-determined shapes, nanostructure retention, and in many cases surprisingly positive effects on properties. In the midst of unquestioned success in attaining near-theoretical density in SPS samples of even the most refractory high-temperature materials (e.g. borides, carbides) the underlying science of “why” SPS does work so well still remains a mystery. Notable efforts to build the scientific framework for SPS have been made however, and we cite only a few selected references here [6], [7], [8], [9], [10], [11], [12], [13], [14] and [15].

This VP Set on SPS has been assembled to provide a viewpoint of the current understanding of the mechanisms involved, structure, and properties of SPS processed materials. The intention is not to overlook the many significant engineering and technological achievements in this field, but to provide a snapshot of SPS as it matures into a more established materials processing method. The limit of approximately 12 articles that make a typical Scripta VP Set necessitated our making a choice on the basis of our perception of the breadth needed and also the willingness of authors to submit their contributions on a tight timeline. Thus the authors chosen for this VP Set are in no way a comprehensive representation; indeed we regret, with apologies, the exclusion of many distinguished scientists working on SPS research, development and manufacturing.

The articles in the VP Set have been organized in the order of mechanisms, synthesis and processing, and mechanical and optical properties. We are grateful to all the authors for responding to our invitation and delivering their viewpoint on this rapidly evolving subject. We are sure their contributions will greatly help the effort of the materials community to further the scientific underpinnings of SPS.