|
An alumina effect pigment is a pearlescent pigment based on alumina (aluminium oxide). The most important class of special effect pigments today exists of natural mica platelets coated with thin films of transparent metal oxides like titanium oxide and iron oxide. To expand the range of achievable color effects, further special effect pigments were developed, which use substrate materials such as aluminum oxide, silicon dioxide or borosilicate instead of mica.〔Pfaff, G., Industrial Inorganic Pigments, 3rd., Wiley-VCH, 2005, 230.〕〔Pfaff, G., High Performance Pigments, ed. H. M. Smith, Wiley-VCH, 2002, 77〕 == Production process == Effect pigments based on aluminum oxide flakes (alumina flakes) are produced using a special, technologically ambitious manufacturing process. In the first step of the production process, Al2O3 (Aluminium oxide) flakes with a very smooth and perfect surface are formed. The flakes are produced using a crystal growth process. They are formed in the corundum structure (α-Al2O3). The desired flake shape is achieved by controlled crystal growth in the axial and equatorial directions. The extraordinary color purity and transparency of the effect pigments obtained by coating the Al2O3 flakes with metal oxides can be attributed to the synthesis procedure yielding single-crystalline thin flakes 〔Nitta, K., Shau, T. M. Sugahara, ''J. EP'' 763 573〕〔Sharrock, S., Schül, N. "New Effect Pigments Based on SiO2 and Al2O3 Flakes", ''Eur. Coat. J.'' (1/2) (2000) 20〕 The coating of the alumina platelets with high-refractive metal oxides, especially with titanium dioxide and iron(III) oxide leads to extraordinary strongly reflecting effect pigments. These pigments possess a very intensive glitter effect, the so-called crystal effect or sparkle. The coating process is analogous to that used for metal oxide mica pigments except it starts from an aqueous suspension of Al2O3 flakes. The complete manufacturing process of pigments based on aluminum oxide platelets, consisting of the flake production and the coating with metal oxides is shown in Figure 1 〔Teaney, S., Pfaff, G., Nitta, K., "New Effect Pigments Using Innovative Substrates", ''Eur. Coat. J.'' (4) (1999) 90〕 For outdoor applications they are modified with an additional weather stabilizing surface treatment. The effect pigments so described are available on the market as ("Xirallic®" ) pigments, which is a trademark from Merck KGaA. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Alumina effect pigment」の詳細全文を読む スポンサード リンク
|