NIR Shielding Research Articles

Transparent (NH4)xWO3 colloidal dispersion and solar control foils: Low temperature synthesis, oxygen deficiency regulation and NIR shielding ability

Highly-stable aqueous dispersion of (NH4)xWO3 crystallites (ac. 6–12nm in diameter and 20–100nm in length) with decent infrared shielding ability was synthesized at only 100°C. The effects of reducing agent (N2H4∙2HCl) dosage on the phase, morphology, zeta potential and composite of products have been systematically addressed. It was shown that the addition of N2H4∙2HCl in precursor solution introduced obvious oxygen deficiency into (NH4)xWO3 crystallites, resulting in a further improved NIR shielding ability. However, high dosages of N2H4∙2HCl were found to depress the zeta potentials and accelerate the growth of (NH4)xWO3 crystallites. A mechanism, which was reasonably supported by confirmatory experiments, was extracted to explain the result. To show potential application of our product, (NH4)xWO3-based flexible solar control foils were prepared by directly casting the dispersion onto polyethylene terephthalate (PET) substrates. The foils can selectively cut-off near infrared light (NIR) by 65.8% (transmittance depressed from 91.3% of a bare PET to 25.5% of the foils), while maintaining a high visible transmittance of 67.6%, showing promise as energy-efficient filter.

Synthesis of One-Dimensional Potassium Tungsten Bronze with Excellent near-Infrared Absorption Property

Potassium tungsten oxide nanofibers were successfully synthesized via a facile hydrothermal reaction route in the presence of sulfate. After reduction under a reductive atmosphere of H(2)(5 vol %)/N(2), the potassium tungsten oxide transformed to potassium tungsten bronze. Because of the lack of free electrons, the potassium tungsten oxide (K(x)WO(3+x/2)) showed no NIR shielding performance; however, the potassium tungsten bronze (K(x)WO(3)) showed promising optical characteristics such as high transmittance for visible light, as well as high shielding performance for near-infrared lights, indicating its potential application as a solar filter. Meanwhile, the potassium tungsten bronze (K(x)WO(3)) showed strong absorption of near-infrared light and instantaneous conversion of photoenergy to heat.

Novel synthesis of homogenous CsxWO3 nanorods with excellent NIR shielding properties by a water controlled-release solvothermal process

Nanosize homogenous rod-like tungsten bronze CsxWO3 with excellent NIR shielding ability was successfully synthesized by a novel and facile water controlled-release solvothermal process (WCRSP).