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The Plasma Actived Sintering Process. Juan Carlos Rendon Angeles, Doctor Program Student. Research Institute for Fracture Technology, Tohoku University. In general, ceramics have properties superior to metals in the areas of thermal and wcar resistance, however, ceramics have hitherto only been used as structural parts in static enviroments, because of their brittleness. Engineering ceramics may divided into oxides and non-oxides. Typical oxides for engineering applications are alumina (Al2O3), zirconia (ZrO2), etc, whilst on the other hand non-oxide ceramics are typically carbidcs such as SiC or, nitride such as Si3N4 and some borides. Ceramic powders are usually sintered by Hot-Pressing (HP), Hot-Isostatic Pressin,,however high densification levels have not been obtained in pure non-oxide. cerumics such as Si3N4 and SiC. The poor sinterability to full density exhibited thesc ceramics seems to be influenced by factors such as the presence of covalent bonding, high melting points under atmospheric conditions and very low diffusion coefficients. Since 1990 a new improved sintering process for metal and ceramic powders has been under developement by Sumitomo Coal Mining., Ltd. known as Spark Plasma Sintering (SPS). In this process (hot pressing without heating elements), sintering is performed by the direct application of high voltage causing spark discharge across gaps between powder particles to generate a plasma, which evaporates surface oxide films and absorbed impurities. Sintering may be completed very rapidly in order of seconds or a few minutes. The followings features of SPS to make it industrially attractive: 1) Growth of metallic crystals during the sintering process is inhibited by low bulk temperatures and the short-time of sintering; 2) Amorphous material structures remain unaffected; 3) High heating rates of 1000 to 2000 ℃ per minute reduce the sintering time of high melting point materials such as a carbides, borides, tungsten, molybdenum, etc. Most Spark Plasma Sintering developments to date have been directed toward improving the operating performance of this equipment in order to get high density levels principally from Si3N4 and SiC ceramics powders. This work is currently in hand at RIFT Tohoku University in cooperation with the Miyagi Perfectural Institute of Technology. We are interested in the manufacture and characterization of engineering ceramics such as Al2O3; PZS (ZrO2); Si3N4 and SiC by the SPS process and the evaluation of the mechanical properties of this materials. |