Abstract
Mesoporous chromia aerogels with a surface area of 484-735 m 2g-1 a pore volume of 0.4-0.9 cm3 g -1 and a pore diameter of 3-9 nm were prepared by urea-assisted homogeneous precipitation from an aqueous Cr(NO3)3 solution, followed by continuous supercritical CO2 extraction. The aerogels were characterized by means of N2-adsorption isotherms, AA, HRTEM, FTIR, thermoanalytical methods TPD, TPO, DSC and X-ray diffraction in combination with structure modeling. For production of mesoporous aerogels with surface areas > 700 m2 g-1was required P CO2 of ∼ 400 bar. The chromia aerogels consisted of 3 to 5 nm nanoparticles representing a monoclinic analogue of α-CrOOH in which half the O atoms and OH groups were replaced with coordinately bonded water molecules. After dehydration at 550-600 K the materials retained their texture, being converted to two-dimensional fragments (clusters) of α -CrOOH crystals built on [Cr(OH)3O3] octahedra without bonding along the Z-axis (N2, vacuum) or to amorphous CrO2 (air). At temperatures of >650 K in air and of > 773 K in an inert atmosphere, the material was converted to α-Cr2O3 with 50-nm particles.
Original language | English |
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Pages (from-to) | 247-250 |
Number of pages | 4 |
Journal | Studies in Surface Science and Catalysis |
Volume | 146 |
DOIs | |
State | Published - 1 Jan 2003 |
ASJC Scopus subject areas
- Catalysis
- Condensed Matter Physics
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films
- Materials Chemistry