Light-induced thermal drying process of sol-gel layers obtained by ultrasonic atomization

Sol-gel coatings provide durable surface protection across automotive, construction, and industrial sectors. The global market was valued at USD 7.8 billion in 2022 and is projected to reach USD 16 billion by 2030, representing a 9.4% compound annual growth rate (CAGR). Automotive applications dominate this growth, with car window coatings alone expected to reach USD 6.5 billion by 2030 at an 11.9% CAGR. These coatings offer superior protection for various surface functions, making them increasingly critical for high-performance industrial applications.^[1]

For research purposes, the most common method of preparation of sol-gel layers is dip-coating. However, this method poses challenges when it comes to large-scale and curvilinear surface substrates. Consequently, ultrasonic atomization has been proposed as a promising alternative: it forms uniform, thin sol-gel films from precisely controlled, ultrafine droplets without degrading the hydrolysate structure.^[2] Ultrasonic atomization is based on ultrasonic vibrations that atomise substances from the liquid phase into a spray form, without any adverse chemical processes degrading the original hydrolysate. The size of the droplets is very fine, with volumes expressed in nanoliters, and their size distribution during ultrasonic spraying can be precisely controlled to form uniform thin films.^[3]

While ultrasonic atomization effectively addresses challenges relating to deposition uniformity, the subsequent thermal stabilization of sol-gel layers remains energy-intensive. Conventional thermal curing typically requires elevated temperatures and extended processing times, creating significant barriers for heat-sensitive substrates and high-throughput manufacturing. To address these limitations, we propose light-induced thermal drying as an energy-efficient stabilization method that reduces energy consumption while maintaining coating performance.

In this study, sol-gel coatings were deposited using ultrasonic atomization and subsequently stabilized by light-induced thermal drying process. Controlled light radiation primarily functions as a thermal energy source to promote solvent evaporation. A dedicated photothermal drying stand enable simultaneous irradiation and temperature control. The resulting layers are evaluated to assess the feasibility of light-assisted thermal drying as a low-energy alternative to the industrial sol-gel coating process.

References:

^[1]Global Industry Analysts. Global Sol-Gel Coatings Industry. February 2024.

² Da-Wei Li et al. Large-scale fabrication of durable and robust super-hydrophobic spray coatings with excellent repairable and anti-corrosion performance. Chemical Engineering Journal, 367 (2019). doi: 10.1016/j.cej.2019.02.093.

³V.N. Khmelev et al. Spray Shape Formation at Ultrasonic Spraying Process. International Conference of Young Specialists on Micro/Nanotechnologies and Electron Devices (2018). doi: 10.1109/EDM.2018.8435017.