Facile microwave-assisted synthesis of Cr2O3 nanoparticles with high near-infrared reflection for roof-top cooling applications

Hebbar N. Deepak, K. S. Choudhari, S. A. Shivashankar, C. Santhosh, Suresh D. Kulkarni

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8 Citations (Scopus)


Microwave-assisted solution synthesis was employed for the preparation of Cr2O3 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 Cr2O3, as shown by X-ray diffraction (XRD). High-resolution transmission electron microscopy (HRTEM) of the “700 °C sample” confirmed the well-crystallised Cr2O3 formation 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 Dq/B value (3.76), suggested that Cr3+ 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.

Original languageEnglish
Pages (from-to)747-753
Number of pages7
JournalJournal of Alloys and Compounds
Publication statusPublished - 15-05-2019

All Science Journal Classification (ASJC) codes

  • Mechanics of Materials
  • Mechanical Engineering
  • Metals and Alloys
  • Materials Chemistry

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