Pigments Based on Surface Modified Substrates

Contact person: V. Stengl, Dept. Chemistry of Solids

If homogenous hydrolysis of metal cations by urea is conducted under optimized conditions in the presence of a suitable substrate (mica, kaolin, cellulose), the substrate is covered by a thin film of oxide or hydroxy-oxide.

By that method it is possible to prepare coloured composite pigments with kaolin or mica cores. The resulting colour depends on the chosen metal cations, their valence and phase composition and post-synthesis treatment.  For example, from Fe^III it is possible to obtain a scale of shades from yellow through orange and ochre to bronze and red, Fe^III and Fe^II produce shades from silver to black. Blue shades are formed by a combination of Al^III and Co^II, green by Cr^III and greenish blue by Cr^III and Co^II. The resulting colours of mica pigments can be tuned by calcination. Under certain molar ratio of Co and Al the pigment is light violet at 150 °C and stepwise darkens to black, then turns dark green at 500 °C, it is greenish blue above 650 °C and aquamarine blue at 800 °C.

Selected Papers

• Stengl, V.; Subrt, J.; Bakardjieva, S.; Kalendova, A.; Kalenda, P., The preparation and characteristics of pigments based on mica coated with metal oxides. Dyes and Pigments 2003, 58 (3), 239-244.
• Stengl, V.; Subrt, J.; Bakardjieva, S., Chemically modified mica. Chemicke Listy 2003, 97 (1), 45-48.
• Kalenda, P.; Kalendova, A.; Stengl, V.; Antos, P.; Subrt, J.; Kvaca, Z.; Bakardjieva, S., Properties of surface-treated mica in anticorrosive coatings. Progress in Organic Coatings 2004, 49 (2), 137-145.
• Kalendova, A.; Tamchynova, P.; Stengl, V.; Subrt, J., Behaviour of surface-treated mica and other pigments with lamellar particles in anticorrosive coatings. Macromolecular Symposia 2002, 187, 367-376.

Funding

• Ministry of Industry and Trade, MPO FDK-05 - Applcation of mica pigments with ferric oxides for organic coatings for ecological anticorrosive systems (2000 - 2003)
• Ministry of Industry and Trade, MPO FR-TI1/006 - Materials based on kaolinite modified by nano-oxides of transition metal oxides (2009 - 2012)