The electric current activated/assisted sintering (ECAS) is an ever growing class of versatile techniques for sintering particulate materials. Despite the tremendous advances over the last two decades in ECASed materials and products there is a lack of comprehensive reviews on ECAS apparatuses and methods. This paper fills the gap by tracing the progress of ECAS technology from 1906 to 2008 and surveys 642 ECAS patents published over more than a century. It is found that the ECAS technology was pioneered by Bloxam (1906 GB Patent No. 9020) who developed the first resistive sintering apparatus. The patents were searched by keywords or by cross-links and were withdrawn from the Japanese Patent Office (342 patents), the United States Patent and Trademark Office (175 patents), the Chinese State Intellectual Property Office of P.R.C. (69 patents) and the World Intellectual Property Organization (12 patents). A subset of 119 (out of 642) ECAS patents on methods and apparatuses was selected and described in detail with respect to their fundamental concepts, physical principles and importance in either present ECAS apparatuses or future ECAS technologies for enhancing efficiency, reliability, repeatability, controllability and productivity. The paper is divided into two parts, the first deals with the basic concepts, features and definitions of basic ECAS and the second analyzes the auxiliary devices/peripherals. The basic ECAS is classified with reference to discharge time (fast and ultrafast ECAS). The fundamental principles and definitions of ECAS are outlined in accordance with the scientific and patent literature.

Recently, the number of published papers on the sintering technologies activated by current have increased exponentially. In particular, it has been reported that the application of electric field as high as 120 V/cm permitted the instantaneous full densification of yttria stabilized tetragonal zirconia at the unusual low temperature of 850°C. The mechanisms of the so called flash sintering phenomenon are elucidated by analyzing the temperature distribution of the bulk sample under the application of the electric field.

A combined experimental/numerical methodology is developed to fully consolidate pure ultrafine WC powder under a current-control mode. Three applied currents, 1900, 2100 and 2700 A, and a constant pressure of 20 MPa were employed as process conditions. The developed spark plasma sintering (SPS) finite-element model includes a moving-mesh technique to account for the contact resistance change due to sintering shrinkage and punch sliding. The effects of the heating rate on the microstructure and hardness were investigated in detail along the sample radius from both experimental and modeling points of view. The maximum hardness (2700 HV10) was achieved for a current of 1900 A at the core sample, while the maximum densification was achieved for 2100 and 2700 A. A direct relationship between the compact microstructure and both the sintering temperature and the heating rate was established. r

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Highly transparent pure alumina with an average grain size of 200 nm was fabricated by means of high‐pressure spark plasma sintering. The alumina sintered either at 950° or at 1000°C for 10 min under an applied pressure of 500 MPa had an in‐line transmission of about 64% for a wavelength of 645 nm. The application of high pressure allowed to obtain highly transparent full dense alumina at low temperatures with no considerable grain growth.

The influence of applied pressures on temperature distribution in punch/die/graphite/sample assembly during SPS current control mode operation was systematically investigated by coupling experiments and computer modeling. Combined experimental and numerical results showed that the peak temperature and the temperature difference existing between the sample and the die outer surface progressively decreased with increasing of applied pressure from 5 to 80 MPa. This behavior was attributed to the strong change of the electric and thermal contact resistances at the punch/die interface due to punch Poisson deformation.

Magnesium tin silicide based thermoelectrics contain earth abundant and non-toxic elements, and have the potential to replace established commercial thermoelectrics for energy conversion applications. In this work, porosity was used as a means to improve their thermoelectric properties.Compared to dense samples of Sb doped Mg 2 Si 0.5 Sn 0.5 with a maximum zT of 1.39 at 663 K, porous samples (37% porosity) prepared by a pressure-less Spark Plasma Sintering technique showed significantly lower thermal conductivity and higher Seebeck coefficient, resulting in an increased maximum zT of 1.63 at 615 K. The possible origins of the enhanced Seebeck coefficient can be attributed to change of carrier concentration and modification of the band structure, by microstructural engineering of the surface composition and particle-particle contacts

Commercially available alumina powder was consolidated at 1150°C by spark plasma sintering at the heating rate of 100°C/min. The effects of the pressure application mode were examined with respect to microstructure, porosity, and transparency. A finite‐element simulation was developed in order to understand the relationship between sample homogeneity and its temperature distribution. The effects of the temperature probing point on the microstructure were investigated. The application of two steps pressure was found effective to obtain homogeneously densified translucent alumina samples at high heating rate.