Introduction

A method for the preparation of composite ceramic material SiC-AlN, starting from porous silicon carbide, though the vapour chemical infiltration of alumium nitride, by using CVI technique. The obtained ceramic composite material is of particular interest for high temperature Concentrated Solar Power application (ceramic receiver). Tested within the Nextower project (www.h2020-nextower.eu).

Technical features

The receivers for concentrating solar technology (CSP) normally used are metallic and barely reach 700 ° C.  Hence the need to make them  with a ceramic material capable of satisfying a series of thermo-structural characteristics: material resistant to oxidation at 1000 ° C, to environmental ageing, to thermal shock and with high thermal conductivity. The present invention responds to the need to find a solution that would allow the creation of a composite ceramic material based on silicon carbide (SiC) and aluminum nitride (AlN), without AlN being exposed to oxidation phenomena at high temperatures. and without undergoing a drastic reduction of its thermal conductivity.

The process comprises the infiltration steps, in which the pores of the substrate are filled with AlN; dissolution, in which a superficial portion of AlN infiltrated in the individual pores is dissolved: sealing, in which the pores are closed on the surface with SiC. It is characterized by the fact that the infiltration step is starting from gaseous mixtures of aluminum chloride and ammonia, with or without thermal gradient or forced flow of the reagents.

Possible Applications

• High temperature Concentrated Solar Power (ceramic receivers);
• Ceramic Heat exchangers for energy demanding production;
• Ceramic burners for biomethane-hydrogen mixtures (SPIRE project CEM-WAVE).

Advantages

• Unique combination of thermal conductivity (higher than ceramic materials), tolerance to high temperature (up to 1500°C) and aggressive environments