Research On Multi-Functional Features Of Mica-Fe_xO_y Pearlescent Pigment

Mica-Fe₂O₃ pearlescent pigment is an important colorful pearlescent pigment. Due to the rich color and strong covering ability, mica-Fe₂O₃ pearlescent pigments have been widely used in building coatings, automotive, cosmetics and other fields. The production of mica-Fe₂O₃ pearlescent pigments relied on the experiences of workers. As a result, the color of mica-Fe₂O₃ pearlescent pigments couldn’t be characterized accurately. Moreover, the previous researches mainly concerned the optimum process parameters and the morphology of mica-Fe₂O₃ pearlescent pigments. The theory study of relationships between composition, structure and color characteristics of mica-Fe₂O₃ pearlescent pigments is not thorough, which restricts the development of the pigment. Furthermore, the demand of functional materials is increased. However, the study of mica-Fe₂O₃ pearlescent pigments mainly concentrated on the decorative feature. In this paper, the near-infrared reflection property and thermal insulation property of mica-Fe₂O₃ pigment and magnetic property of mica-Fe₃O₄ pearlescent pigment were studied.In this dissertation, mica-Fe₂O₃ pearlescent pigments were prepared by liquid phase deposition. The influence of process conditions on the coating rate, the effect of composition and structure of Fe₂O₃ coating on its optical and thermal properties, and the magnetic property of mica-Fe₃O₄ pearlescent pigment were studied. The main point could be summarized as following.（1） The effect of synthesis process on the coating rate of mica-Fe₂O₃ pearlescent pigment. The pH values influenced the nucleation driving force of Fe（OH）3 in suspension. when the pH value was in the range of 3.0 to 3.6, heterogeneous nucleation was dominated in the suspension system. As a result, high coating rate of Fe₂O₃ could be prepared. The reaction temperature influenced the nucleation rate of Fe（OH）3 in suspension. The suitable reaction temperature was 80℃⁸5℃. Dropping speed influenced the concentration of Fe3+ in suspension. when the dropping speed was too quick, homogeneous nucleation was dominated in the suspension system., leading to the low coating rate and surface roughness. The appropriate dropping speed was 18mL/h²4m L/h. Mass ratio of liquid and mica influenced the deposition rate of Fe（OH）3. The optimal ratio is 10 to 20.（2） The influence of composition and structure on the color properties of mica-Fe₂O₃ pigment. The coating rate of mica-Fe₂O₃ pearlescent pigment influenced the thickness of Fe₂O₃ thin film. As the increase of coating rate, mica-Fe₂O₃ pearlescent pigments exhibited yellow, red, brown and other hues. Calcination influenced the crystal type and particle size of Fe₂O₃ nanoparticles. The calcination led to the decrease of the hue. Optical films theory were used to analyze the coloration mechanism of mica-Fe₂O₃ pearlescent pigment. As a result, a reflection model for simulate the reflectance and predict the color of mica-Fe₂O₃ pearlescent pigment was established.（3） The near-infrared reflection and insulation properties of mica-Fe₂O₃ pearlescent pigment were studied. As the increase of coating rate, the near-infrared light reflectance decreased. The maximum reflectivity of near-infrared light was as high as 75.67%. The thermal insulation property was explored by a self-made equipment. The surface temperature of test board was reduced 4.2℃⁵.4℃, and the inner surface temperature of test board reduced 5.3℃⁹.1℃, indicating the high thermal insulation property of mica-Fe₂O₃ pigments.（4） Magnetic property of mica-Fe₃O₄ pearlescent pigment was studied. The remanent magnetization（Mr） and coercive force（Hc） of mica-Fe₃O₄ pearlescent pigment was very small, confirming the superparamagnetism of mica-Fe₃O₄. As the increase of coating rate, the saturation magnetization increased. when the coating rate was 40%, the saturation magnetization of mica-Fe₃O₄ pearlescent pigment was 3.9599emu/g. Moreover, an inert atmosphere is more favored for the increase of saturation magnetization.