Prof. Simo-Pekka Hannula,
Department of Materials Science and Engineering, Aalto University School of Chemical Technology,
You find it here as a pdf-file.
His Topic of Materials' Days 2011:
Processing of Hybrid Materials by Pulsed Electric Current Sintering (PECS)
Application of AC or DC fields during sintering has been shown to be effective in lowering processing
temperatures necessary for the elimination of porosity and reducing grain growth. The effect is essentially
athermal, i.e., independent of heating rate and sintering temperature. The use of electric current also
enables higher heating rates and shorter holding times. Therefore it is possible to sinter powders near
theoretical density with little grain growth very effectively. Additionally the use of electric current
enables sintering of materials, which by conventional methods would be difficult or impossible to sinter.
Patents regarding the use of electric current to enhance sintering have been issued since the beginning of
1920s. Nowadays electric current assistant sintering is commonly used in combination of hot pressing.
The low-voltage, high amperage current goes through both die and the compact providing both uniform
and fast heating. Typically, pulsed current is utilized. Pulsed current provides high heating rates and
activates sintering in the microstructural level e.g. by accelerating neck growth due to discharge spark.
The importance of FAST sintering methods in industrial scale is still rather limited, but increasing at an
accelerating rate since the late 1990s. The FCT HP D 25-2 PECS unit was taken in use at Aalto
University in 2008 in order to make the technology known to the Finnish industries.
PECS has been used successfully since for compacting of various materials including several composite
materials such as WC-8Co, WC-12Co Cu-Cu2O, Cu-Al2O3, Cu-ND, Cu-TiB2, Ultimet-TiC, Ni-Mn-Ga-
WC and Al2O3/ZrO2 nanocomposites with different solid lubricants. A new area of application is
compaction of hybrid materials. This includes compaction of CN and Ce0,9Gd0,1O1,95 based materials for
targets to be used in producing PVD coatings of corresponding structures. PECS has also been studied
recently for compacting of magneto-optical materials from hybrid sol-gel derived SiO2 –Fe3O4 powders.
The results obtained so far will be presented, and challenges in compaction of such materials will be