Hiroki Gonome

Control of radiative properties of coatings pigmented with Fe 2O 3 nanoparticles

This study describes nanoparticles pigmented coatings used in controlling the radiative properties of surfaces exposed to sunlight. An optimization method that embraces both thermal and aesthetic requirements has been proposed. The proposed coatings maximize the reflectivity of the near infrared (NIR) region to reduce thermal heating, while for aesthetic appeal they minimize the visible (VIS) reflected energy. This spectral behavior can be achieved by controlling the size and concentration of pigment particles and coating thickness. In this study, both experimental and numerical approaches are applied on Fe2 O3 pigmented coating samples with 0.2 μm and 1 μm of average particle size and different particle concentrations and coating thicknesses. For numerical part the radiation analysis using the Radiation Element Method by Ray Emission Model (REM2 ) in a one dimensional parallel plane model is conducted. From the numerical results, it is shown that the optimum size of Fe2 O3 particles for our desired spectral behavior is about 0.8 μm. The experimental results also show that the samples made from 1 μm particles have better performance for our objective.Copyright

Artificial chameleon skin that controls spectral radiation: Development of Chameleon Cool Coating (C 3 )

Chameleons have a diagnostic thermal protection that enables them to live under various conditions. Our developed special radiative control therefore is inspired by the chameleon thermal protection ability by imitating its two superposed layers as two pigment particles in one coating layer. One particle imitates a chameleon superficial surface for color control (visible light), and another particle imitates a deep surface to reflect solar irradiation, especially in the near-infrared region. Optical modeling allows us to optimally design the particle size and volume fraction. Experimental evaluation shows that the desired spectral reflectance, i.e., low in the VIS region and high in NIR region, can be achieved. Comparison between the measured and calculated reflectances shows that control of the particle size and dispersion/aggregation of particle cloud is important in improving the thermal-protection performance of the coating. Using our developed coating, the interior temperature decreases and the cooling load is reduced while keeping the dark tone of the object.