Mica pigment

J. B. Preston, "Mica," Pigment Handbook, John Wiley Sons, Inc., New York, 1971, 30 pp. 

Further experiments were carried out in which small flakes of a 40 pm thick grey mica pigmented lacquer were mechanically detached from mild steel, the resulting transients were captured and analysed. 

By using layers of FCjOj brilliant, intense coloms can be obtained from layers only 50-250 mn in thickness. The FCjOj-mica pigments form absorption and interference coloms simultaneously, the observed coloms again being dependent on the layer thickness. 

Figure 73. Simplified scheme of light reflection at the phase boundaries of a metal oxide-mica pigment...

Figure 76. Upper half of metal oxide - mica pigments...

Figure 77. Cross section of a TiOz-mica pigment (transmission electron micrograph)...

Ti02-mica pigments are used in all color formulations of conventional pigments where brilliance and luster are required in addition to color, i.e., in plastics, coatings, printing, and cosmetics. A major market for silver white pigments (pearl pigments, white metallic ) is the plastics industry. 

Fe203-mica pigments are produced by precipitation of iron(II)- or iron(III)-ions in aqueous mica suspensions and calcination of the so obtained coated particles at 700-900°C [5.190], [5.192]—[5.194] ... 

It is also possible to produce iron oxide mica pigments by a direct CVD fluidized bed process where iron pentacarbonyl is oxidized and Fe203 is deposited on the mica surface [5.227] ... 

Coloristic Variations on the Basis of Mica. Mica platelets can be coated with a variety of compounds to produce novel pigments. Solid state reactions and CVD-process enlarge the possibilities for the synthesis of mica pigments. In addition, the calcination of the materials in the presence of inert (e.g. N2, Ar) or reactive gases (e.g. NFI3, H2, hydrocarbons) allows the formation of phases which are not producible by working in air. Table 54 contains a summary of nacreous mica pigments with special coloristic properties. 

Reduction of suitable aqueous metal salts by electroless plating yields metal-coated mica pigments. They are less expensive than noble metal flakes (Au, Ag) and their brilliant metallic appearance is comparable with that of metallic flakes [5.192], [5.193],... 

On the other hand, new pigments based on transparent silica flakes show extremely strong optical effects, which are different to mica pigments [5.244]. Angle dependent colors and other effects, achieved by the combination of these Si02-flakes with... 

Practically applied platelet-like crystalline materials are produced with layer thickness (d) which are necessary to obtain the desired interference colors (iridescence) [11], Most of the pearlescent pigments synthesized today consist of at least three layers of two materials with different refractive indices. A simplified structure of such pigments and their interaction with light is shown in Fig. 15.4. For the case of metal oxide-mica pigments, thin flakes of mica (thickness ca. 500 nm, compara-... 

Figure 15.4. Transmission electron micrograph of a Ti02-mica pigment with the schematic way of light through layers (blue interference effect, yellow transmission).

Figure 15.6. Schematic illustration of different metal oxide-mica pigments.

Figure 15.7. Scanning electron micrographs of a Ti02-mica pigment prepared by the wet chemical process.

Coating of TiOz-mica pigments with an organic colorant for a masstone or two-tone pigment is done by precipitation or deposition on the pigment surface in... 

Table 15.2 contains a comparative overview of Ti02-mica pigments, basic lead carbonate, bismuth oxychloride, and natural fish silver. Some further physical data are summarized in Table 15.3. 

Table 15.4. Functional Metal Oxide—Mica Pigments...

Table 15.4 contains data about the functional properties of some metal oxide-mica pigments. 

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