Materials Synthesis and Development

Group

Ceramic-oxide-fiber composites

Topic

Contributing to energy generation

 

Increasing the efficiency of future power stations run at temperatures > 1400 °C

 

Specific challenge

 

  1. High creep resistance at high temperature, and
  2. sufficient "damage tolerance" (stress relaxation) underconditions of thermal shock

associated by:

1. Conversion of commercial fibers with sub-µm microstructure into highly creep resistant components by re-crystallization

Microstructures of Al2O3 fibers: original (commercial) state and after re-crystallization at 1750°C/Ar.

 

Creep results

 

(composites with mullite or Al2O3 matrix; fiber content ~ 40 vol-%):


2. Tailoring damage tolerance by tuning the fiber/matrix interface strength from "week" to "strong"

Mullite matrix sintered 1400 °C (P=35 %). Al2O3/mullite matrix sintered 1600 °C (P=22 %). reference: TiAl - applicable up to ~ 800...900 °C only

 

Ease of OCMC manufacture

 

(a) Using commercial ("affordable“) bundles of easily processable polycrystalline fibers with subsequent re-crystallization, or
(b) Separate fiber re-crystallization (cooperation: ISC Wuerzburg) followed by shaping of composites
  --> Creep resistance similar single-crystal fibers without associated technological restrictions



Tube demonstrator, Al2O3, Ø 40 mm x 70 mm.