A comparative study of oxides and carbides ceramics sintered by two ultra rapid densification processes

Reference Presenter Authors
(Institution)
Abstract
12-018 ALEXANDRE ALLEMAND ALLEMAND, A.(CEA); LEPETITCORPS, Y.(Université de BORDEAUX); BESNARD, C.(CNRS); COUILLAUD, S.(GALTENCO); LEON, J.(GALTENCO); During Spark Plasma Sintering (SPS) of barium aluminosilicate BaAl2Si2O8 (BAS) a major problem appeared as soon as big parts or complex shapes tried to be made. Indeed, whether it is for the sintering of beams or discs of 60mm diameter, all the tests performed with SPS created a total or partial fusion of the sample. This fusion occurred at temperatures much lower than the melting point of the material. Tests performed on samples 10mm in diameter was estimated to have a difference of 200°C between the temperature measured on the surface of the matrix and the real temperature of the sample. It is this issue of mastering an exact thermal gradient during the SPS process that has brought us, with the company GALTENCO, to work on a ultra fast, new method of sintering ceramics without pressure. This method, similar to SPS in terms of speed of temperature rise and of temperature dwell, should allow a perfect control of the thermal gradient in the sample to sinter regardless of size and shape. This method bases itself on the manufacturing of a specific mold (made specifically for the sample) and contains a number of heating elements (each associated with a thermal pixel) piloted independently in real-time to control the thermal gradient. This presentation will show a comparative study between the SPS sintering route and this new GALTENCO method to sinter BAS, magnesia (MgO) and silicon carbide (SIC). It is remarkable to see that the GALTENCO method allows sintering beams of BAS, which was impossible to make with SPS. Furthermore, the microstructures of MgO and of SIC samples are very similar for the two methods for comparable sintering thermal cycle. This observed similarity lead to the conclusion that on the tested configuration there is no specific effect of the current in the SPS technique to explain the fast sintering speed except for the Joule effect. Quickly rising temperature is the key to a fast densification.
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