Abstract
The synthesis of ZnO comprising different ratios of zinc acetate (ZA) and zinc nitrate (ZN) from the respective zinc precursor solutions was successfully completed via a simple precipitation method. Zinc oxide powders with different mole ratios of ZA/ZN were produced—80/1, 40/1, and 20/1. The crystallinity, microstructure, and optical properties of all produced ZnO powders were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV-Vis-NIR spectrophotometry. The average agglomerated particle sizes of ZnO-80/1, ZnO-40/1, and ZnO-20/1 were measured at 655, 640, and 620 nm, respectively, using dynamic light scattering (DLS). The optical properties of ZnO were significantly affected by the extreme ratio differences in the zinc precursors. ZnO-80/1 was found to have a unique coral-sheet structure morphology, which resulted in its superior ability to reflect near-infrared (NIR) radiation compared to ZnO-40/1 and ZnO-20/1. The NIR-shielding performances of ZnO were assessed using a thermal insulation test, where coating with ZnO-80/1 could lower the inner temperature by 5.2 °C compared with the neat glass substrate. Due to the synergistic effects on morphology, ZnO-80/1 exhibited the property of enhanced NIR shielding in curtailing the internal building temperature, which allows for its utilization as an NIR-reflective pigment coating in the construction of building envelopes.
Highlights
The residential component of electricity usage in Thailand comprised approximately 27% of the total electricity consumed in 2020 [1]
This leads to different NIR-shielding properties [27] as the NIR-shielding performance of zinc oxide (ZnO) is dependent on its morphology
The synthesis process has a crucial effect on the formation of ZnO morphology
Summary
The residential component of electricity usage in Thailand comprised approximately 27% of the total electricity consumed in 2020 [1]. An effective approach to optimizing NIR protection can be achieved by coating the building glass with NIR-reflective pigment These pigments are widely used in roofs and windows to reduce the inner temperature of buildings due to their NIR radiation properties, which contribute to minimizing the indoor heat build-up. In terms of NIR-shielding performance, the spherical ZnO synthesized by hydrothermal synthesis acts as an excellent barrier to energy in the NIR region, while the rod morphology shows less visible reflectance [44]. The mentioned properties of ZnO obtained from pure zinc acetate and zinc nitrate were systematically studied
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