Coatings, mica

Titanium dioxide-ferric oxide coated mica... 

Bussiek, M., Mficke, N., and Langowski, J. (2003) Polylysine-coated mica can be used to observe systematic changes in the supercoiled DNA conformation by scanning force microscopy in solution. Nucleic Acids Res. 31, 137. 

Bernard BK, Osheroff MR, Hofmann A, et al Toxicology and carcinogenesis studies of dietary titanium dioxide-coated mica in male and female Fischer 344 rats. J Toxicol Environ Health 29 417M-29, 1990... 

As with fatty acids, organo-silanes can be applied by both wet and dry coating methods. In the present context, wet coating is principally restricted to glass fibre coating, where it can be incorporated into the size, which is already applied from water. Dry coating is the preferred method for coating mica, wollastonite clays and metal hydroxides. 

Table 51 shows an overview of pigments with luster effects. Effect pigments can be classified as metal platelets, oxide-coated metal platelets, oxide-coated mica platelets, platelet-like mono-crystals and comminuted PVD-films (Physical Vapor Deposition). Aims of new developments are new effects, colors, improvement of hiding power, increase of the interference color, increase of light and weather stability and improved dispersibility characteristics. Of special interest are pigments which are toxicologically safe and which can be produced by ecologically acceptable processes. 

Pigments consisting of BiOCl-coated mica or talc and blends of BiOCl with other organic or inorganic colorants are also available. 

The development of the mica-based pigments started with pearlescent colors (Fig. 76 A, TiOz - mica). It was followed by brilliant, mass-tone-colored combination pigments (i.e., mica, Ti02, and another metal oxide) with one color (interference color same as mass tone) or two colors (interference and mass tone different) that depend on composition and viewing angle (Fig. 76 B). In the 1980s further development was made by coating mica particles with transparent layers of iron(III) oxide (Fig. 76 C) [5.222]. 

Titanium Dioxide - Mica (Fig. 77). The first multilayer pigments were marketed in the 1960s as Ti02-coated muscovite micas [5.193], [5.201]. Two different processes are used for coating mica in aqueous suspension on a commercial basis ... 

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],... 

Merck in Japan has recently patented [16] a process for the production of water and weather-resistant pearlescent pigments produced by coating mica with hydrous zirconia. This is in many ways similar to processes operated in the titanium oxide industry and mentioned previously. The zirconium hydroxide aids dispersion and gives better compatibility with the polymer matrix that it is incorporated in. 

Specifically, consider the case in which H refers to a hydrocarbon, W to water, and M to mica Ahw/hw = 0.95 kTI00m, Amh/mh = 2.1 kTtoom, and AHw/mh = —0.226 kTmom. Only in the limit of contact, separation w < thickness h, can the finitude of h be ignored. The interaction ratio of hydrocarbon-coated mica compared to hydrocarbon layers alone increases monotonically with separation w and equals unity only in the limit of close approach.4... 

Compared with the interaction of two semi-infinite bodies of hydrocarbon, the interaction between hydrocarbon-coated mica surfaces increases steadily versus separation whereas that between two finite slabs of hydrocarbon expectably decreases. Significant deviations are already clear at w/h = 1, when the varying separation w equals the constant layer thickness h. 

For measurements between crossed mica cylinders coated with phospholipid bilayers in water, see J. Marra andj. Israelachvili, "Direct measurements of forces between phosphatidylcholine and phosphatidylethanolamine bilayers in aqueous electrolyte solutions," Biochemistry, 24, 4608-18 (1985). Interpretation in terms of expressions for layered structures and the connection to direct measurements between bilayers in water is given in V. A. Parsegian, "Reconciliation of van der Waals force measurements between phosphatidylcholine bilayers in water and between bilayer-coated mica surfaces," Langmuir, 9, 3625-8 (1993). The bilayer-bilayer interactions are reported in E. A. Evans and M. Metcalfe, "Free energy potential for aggregation of giant, neutral lipid bilayer vesicles by van der Waals attraction," Biophys. J., 46, 423-6 (1984). 

V. A. Parsegian, "Reconciliation of van der Waals force measurements between phosphatidylcholine bilayer in water and between bilayer-coated mica surfaces," Langmuir, 9, 3625-8 (1993). 

Force measurements between polymer-coated mica surfaces exhibit many of the features predicted by the SF model. The force measurement technique characterizes the interaction between polymer layers and provides an indirect... 

Iron(III)oxide is also suitable for coating mica platelets. It combines a high refractive index (metallic luster) with good hiding power and weather resistance. Fe203-mica pigments are produced by precipitation of iron(II)- or iron(III)-ions in aqueous mica suspensions and then calcined at 700-900°C [5, 6, 8, 9] ... 

The work of Larson et al. (62) represented the first detailed study to show agreement between AFM-derived diffuse layer potentials and ((-potentials obtained from traditional electrokinetic techniques. The AFM experimental data was satisfactorily fitted to the theory of McCormack et al. (46). The fitting parameters used, silica and alumina zeta-potentials, were independently determined for the same surfaces used in the AFM study using electrophoretic and streaming-potential measurements, respectively. This same system was later used by another research group (63). Hartley and coworkers 63 also compared dissimilar surface interactions with electrokinetic measurements, namely between a silica probe interacting with a polylysine coated mica flat (see Section III.B.). It is also possible to conduct measurements between a colloid probe and a metal or semiconductor surface whose electrochemical properties are controlled by the experimenter 164-66). In Ref. 64 Raiteri et al. studied the interactions between... 

Like titanium dioxide, iron(III) oxide is suitable for coating mica platelets. It combines a high refractive index (metallic luster) with good hiding power and excellent... 

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