Facile microwave-assisted synthesis of Cr2 O3 nanoparticles with high near-infrared reflection for roof-top cooling applications


Autores: Deepak, H.N. et Al


Microwave-assisted solution synthesis was employed for the preparation of Cr 2 O 3 nanoparticles using Cr(acac) 3 and ethylene glycol. The optimum conditions for the completion of the reaction forming a green precipitate (yield-95%) were: irradiation for 40–60 min at 220 °C solution temperature. The as-prepared sample was barely crystalline; annealing in air at above 300 °C formed nanocrystalline Cr 2 O 3 , as shown by X-ray diffraction (XRD). High-resolution transmission electron microscopy (HRTEM) of the “700 °C sample” confirmed the well-crystallised Cr 2 O 3formation with ∼37 nm average size. The as-prepared powder (bluish-green) showed high near-infrared (NIR) reflectance, whereas the annealed samples showed bright-green reflectance, whose International Commission on Illumination L*a*b* (CIE L*a*b*) values shifted towards the green region. The higher D q /B value (3.76), suggested that Cr 3+ lies in a strong crystal field. Stainless steel blocks covered with the as-prepared (intermediate) material reduced heating under sunlight by 5 °C, indicating its suitability as an easily prepared tile coating for roof-top applications. The annealed samples are found suitable as an anti-dazzling coating for automobile windscreens and rear-view mirrors.

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