Particle size and kind of mica in synthesis of nontoxic bronze and gold pearlescent pigments based on nanoencapsulated hematite

Document Type: Research Paper


Department of Inorganic Pigments and glazes, Institute for Color Science and Technology (ICST)


Nano-encapsulated iron oxide in Zirconium oxide-coated mica pigments are thermally stable,
innocuous to human health, non-combustible, and they do not conduct electricity. They could be
applied in several industries such as thermoplastics, cosmetics, food packaging, children toys, paints,
automobiles coating, security purposes, and banknotes. Nowadays, they are highly desirable in
ceramic decoration. In the present study, intensively dark gold to bronze colored mica clay pigments,
which were based on mica flakes covered with a layer of nano-iron oxide-Zirconium oxide particles,
were prepared by homogeneous precipitation of iron nitrate and Zirconium chloride ammonia in the
presence of mica flakes in two kinds of ore clay-based phlogopite and muscovite minerals. The final
color was obtained by thermal annealing of precipitates at a temperature of 800◦C. The pigments were
characterized by X-Ray Diffraction, Particle size analysis, Scanning electron microscopy,
Transmission electron microscopy, X-Ray fluorescence, and Simultaneous thermal analysis. Results
indicate that nano-encapsulated iron oxide in zirconia particles have been formed on mica flakes and
kinds of clay-mica can be related to obtained shade from dark gold to bronze pearl. Higher particle
size of mica flakes about phlogopite type of mica introduced pearl effects with higher L* changes in
different angles. Muscovite performed higher hue and better pearl effect than phlogopite.


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