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Lecture

Cellular structures with tailored thermal conductivity

Wednesday (24.10.2018)
16:20 - 16:40
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Open-celled ceramic foams are promising candidates for several applications which exploit their intrinsic high specific surface area and high fluid permeability. Examples are filters and support materials for catalysts or active compounds for heat transformation and storage. Especially for these applications a high thermal conductivity of the strut material is mandatory for the transportation of heat generated in thermal transformation or catalytic processes.

Ceramic materials possessing an intrinsically high thermal conductivity frequently belong to the group of „adamantine compounds“ adopting a crystal structure closely related to diamond [1]. Well known examples are silicon carbide and aluminum nitride, but also more exotic representatives like beryllium oxide or zinc oxide belong to the group of adamantine materials. For all of these compounds a strong (significantly covalent) bonding is present, which is responsible for their good thermal properties on the one hand, but also for a low sintering activity, on the other. Therefore, a high sintering temperature and/or liquid phase forming sintering additives are neccessary for densification of these ceramic materials.

Cellular structures made of adamantine materials are predominantly limited to SiC ceramics, which are usually bonded by an oxide phase lowering the sintering temperature, but also the thermal conductivity, significantly. Within the present work the manufacturing of open-celled ceramic foams made of other wurzite-type materials (AlN and ZnO) following the Schwartzwalder sponge replication technique is presented [2]. Their thermal conductivity is investigated as a function of the processing conditions (slurry composition, sintering regime) and correlated to their respective strut microstructure (porosity, phase composition) [3].


[1] G. A. Slack, J. Phys. Chem. Solids 1973, 34, 321

[2] K. Schwartzwalder, H. Somers, A. V. Somers, US 3,090,094, 1961.

[3] U. Betke, A. Lieb, F. Scheffler, M. Scheffler, Adv. Eng. Mater. 2017, 19, 201600660.

 

Speaker:
Dr. Ulf Betke
Otto von Guericke University Magdeburg
Additional Authors:
  • Prof. Dr. Michael Scheffler
    Otto von Guericke University Magdeburg