témavezető: Keszler Anna Mária
helyszín (magyar oldal): MTA, Természettudományi Kutatóközpont, Plazmakémiai kutatócsoport helyszín rövidítés: MTA
A kutatási téma leírása:
The growing demand on engineering applications concerned with exposure to extremely high temperatures (> 2500°C) and harsh environmental conditions are a major challenge of recent research. These high temperature applications cannot be achieved with use of metal or plastic materials. However, these applications are feasible through the use of high performance ceramic materials having a melting point higher than 2500°C. Such ceramics more commonly are referred as ultra-high temperature ceramics (UHTCs) and they are based on borides, nitrides and carbides of the group IVB and VB of transition metals.
Ultra-high temperature ceramics are a family of materials that display a unique set of properties including extremely high melting point, low vapor pressure, chemical stability, high hardness and high temperature strength. This combination of properties make them good candidates for high temperature applications including rocket nozzles, thermal protection materials on hypersonic aerospace vehicles or re-usable atmospheric re-entry vehicles; specific components for propulsion, new very high temperature solar receivers, furnace elements, plasma arc electrodes, direct power extraction electrodes refractory crucibles etc.
Radiofrequency (RF) plasma processes are of growing interest for production of nanosized particles. Plasma is a highly energetic environment which great number of chemical reactions can occur in. In thermal plasmas solid precursors evaporate and dissociate. Dissociated precursors recombine into various products which nucleate in the nanometer range due to the supersaturation of the vapor phase. Good knowledge of elementary plasma processes and properties is very important for the synthesis control to obtain product with controlled properties. The product properties are playing an essential role in further applications.
A considerable body of information has been accumulated about the structure, physicochemical and physicomechanical properties of nanocrystalline high-melting compounds. However, there are still many `blind spots' due to insufficient knowledge of fundamental characteristics of these species. Composition, purity, and grain size all play a major role in governing the mechanical properties of ceramic materials, but these have not yet been optimized for carbides, nitrides or borides.
One of the challenges of UHTC materials is their consolidation into bulk structures. Conventional furnaces are not a plausible option as the temperatures required to melt UHTC material exceeds the capability of most furnaces. Various sintering methods have been used to consolidate UHTC, however consolidation of these materials to high density with a fine grain structure has proven to be challenging task.
Spark plasma sintering (SPS) is a new technique in which an alternating electrical current is passed through the material as it undergoes hot pressing. Using SPS high heating rates and short processing times can be realized. Therefore grain growth can be inhibited and materials with submicron or nanosized microstructures or composites with unique compositions can be prepared leading to improved properties.
felvehető hallgatók száma: 1
Jelentkezési határidő: 2018-05-22
2024. IV. 17. ODT ülés Az ODT következő ülésére 2024. június 14-én, pénteken 10.00 órakor kerül sor a Semmelweis Egyetem Szenátusi termében (Bp. Üllői út 26. I. emelet).
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