A scoping review on reflective coatings with nanomaterials: progress since 2000 and current challenges
M. A. Alim, Zhong Tao, H. M. Imran, Md. Arifur Rahim, Zainab Malik, Ataur Rahman
Abstract
This study investigates the progress in using nanomaterials in reflective coating (RC) technology. Generally, the benefits of RC are twofold: minimising surface temperature and protecting surfaces. The purpose of applying RC is versatile, such as lowering the urban heat island effect and building energy consumption, improving photovoltaic performance, and increasing the durability of infrastructure. Incorporating nanomaterials in RC mixes enhances the effectiveness of this technology. However, the technical feasibility and economic viability of an appropriate preparation procedure with a proper mix design remain debatable. This review looks into peer-reviewed research articles related to the application of nanomaterials in RC technology in the core “ Web of Science ” and “ Scopus” collections. It can be argued that researchers used nanomaterials for five distinct purposes: a) blocking near-infrared and ultraviolet portions of solar radiation, b) temperature shielding, c) radiative cooling, d) sub-ambient cooling, and e) surface cleaning or self-cleaning. It is revealed that nanomaterials could enhance the surface solar reflectivity and emissivity to 97% and 0.97, respectively. The reported surface temperature reduction ranges between 2 and 35 °C with a statistical median value of 9.6 °C, whereas the sub-ambient cooling ranges between 2 and 13 °C with a statistical median value of 5 °C. Cooling power of the RC ranged between 35 and 135 W/m 2 , with a median value of 77 W/m 2 . Inconsistencies in RC performance have been discussed in the related sections. It is also found that a superhydrophobic RC can be prepared with a contact angle of ∼ 164°, but the coating has its advantages and limitations. The role of nanomaterials in enhancing UV stability and durability is discussed, along with the practicality and scalability of the technology. It is revealed that key challenges in RC technology include economic viability, stability concerns, and environmental implications. Based on the current unresolved issues, future research directions are outlined. • Nanomaterials are used in reflective coatings for five distinct purposes. • Highest surface solar reflectivity and emissivity obtained were 97% and 0.97. • Temperature reduction ranged between 2 to 35 °C with a mean of 12.44 °C. • Sub-ambient cooling ranged from 2 to 13 °C with a mean of 5.82 °C.