1. Folie 1 Synthesis of metal oxide aerogels from their salts Helmut Schäfer, Kathleen Heinrich, Barbara Milow, Lorenz Ratke Institut für Materialphysik im Weltraum, Linder Höhe, D-51147 Köln

2. Folie 2 Background Synthesis of aerogels from their metal salts for application as additives in foundry industry Desired properties:- high surface area - high temperature stability Simple process route Synthesis on a large scale

3. Folie 3 Introduction Preparation of aerogels 1. Hydrolysis of metal alkoxides 2. Condensation reaction to hydro- or alcogel 3. Ageing 4. Drying

4. Folie 4 Introduction Preparation of aerogels 1. Hydrolysis of metal salts 2. Condensation reaction to hydro- or alcogel 3. Ageing strong exothermic reaction!! TiCl 4, SiCl 4, ZrCl 4, ZnCl 2, SnCl 4

5. Folie 5 Introduction 4. Supercritical Drying with carbon dioxide Before!! Removal of residual salts solvent exchange: water → alcohol or acetone >Sodium silicate + KCr(SO 4 ) 2 >Al(Cl) 3 >Sodium silicate + FeCl 3 >FeCl 3 >Zr-alkoxide

6. Folie 6 Characterization Adsorption/Desorption measurement with nitrogen TGA-FTIR Scanning electron microscopy

7. Folie 7 Results – BET Surface BJH-PlotAdsorption/Desorption Desorption Adsorption Zirconium aerogel: BET 498 m 2 /g

8. Folie 8 Results – BET Surface PrecursorCatalystBET in m 2 /g ZrCl 4 /TiCl 4 propylene oxide577 ZrCl 4 propylene oxide498 SiCl 4 -798 FeCl 3 · H 2 Opropylene oxide363 AlCl 3 propylene oxide389 Sodium silicate + SnCl 4 -294 SbCl 3 propylene oxide8 Wide range of different aerogels with high surface areas!!

9. Folie 9 The right choice Metal oxideFp in °CSintering temperature (calc.) in °C ZrO 2 26801695 Al 2 O 3 20501275 TiO 2 18551145 SiO 2 17131051 Fe 2 O 3 15651149 -Toxicity -Price per kg -Availability

10. Folie 10 Results – BET Surface MetaloxideCatalystBET in m 2 /g ZrCl 4 /TiCl 4 propylene oxide577 ZrCl 4 propylene oxide498 SiCl 4 -798 FeCl 3 · H 2 Opropylene oxide363 AlCl 3 propylene oxide389 Sodium silicate + SnCl 4 -294 SbCl 3 propylene oxide8 Sodium silicate + KCr(SO 4 ) 2 *H 2 O -400 Zr-, Ti- and Silica-Aerogels showed best results in preliminary tests for foundry applications!

11. Folie 11 Results – TGA: Silica-Aerogel

12. Folie 12 Results – IR (122 °C): (Silica-Aerogel) IR-Library Extracted from 3D-IR-Spectra

13. Folie 13 Results – SEM Silica-Aerogel (572 m 2 /g)

14. Folie 14 Results – Large Scale synthesis Zirconium-Aerogels20 cm 3 (typical lab scale) 50 cm 3 (works fine) 500 cm 3 (monolith) Successful preparation of Zirconium aerogel up to 500 cm 3 500 L Pilot plant scale with industrial partners

15. Folie 15 Conclusion Aerogels can be easily synthesized from their metal salts A wide range of different aerogels with high surface areas were synthesized Zirconia aerogel up to 500 cm 3 were synthesized Focus on Zr-, Ti- and Silica-aerogels for foundry applications