Air plasma sprayed multi-material composite coatings for enhanced light absorption and thermal emission.

Faisal, Nadimul Haque; Rajendran, Vinooth; Kaniapan, Siva; Ramalingam, Vinoth; Prathuru, Anil; Ahmed, Rehan; Katiyar, Nirmal Kumar; Bansal, Aakash; Whittaker, Thomas; Isherwood, Patrick; Whittow, Will; Egiza, Mohamed; Goel, Saurav

Abstract

This study pioneers a transformative approach to solar thermal technology by leveraging air plasma-sprayed (APS) multi-material composite coatings. It is to achieve unprecedented light absorption and thermal emission, redefining the design paradigm for bi-layer coatings in solar thermal applications. For the first time, both single-layer (Mo-Mo2C/ceramic, NiO/YSZ) and bi-layer (NiO/YSZ with an additional 8YSZ top layer) coatings on Hastelloy®X substrate were systematically compared using an extensive suite of characterisation techniques, including scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), optical spectroscopy, infrared thermography, surface roughness, sheet resistance, electrical conductivity, dielectric constant measurements and water absorbency tests. The bi-layer NiO/YSZ+8YSZ coating with the highest surface roughness demonstrated remarkable light absorption and thermal emission properties. With a minimal light reflectance of 0.1 and a high thermal emittance of 0.961, this configuration achieved superior solar energy capture and efficient heat re-emission, outperforming single-layer coatings with a moderate reflectance of 0.2 to 0.6. Additionally, the Mo-Mo2C/ZrO2 coating revealed unique spectral behavior with enhanced reflectance in the infrared region, indicating its potential for niche applications. Moreover, the NiO/YSZ+8YSZ and NiO/YSZ coatings configuration also exhibited minimal water absorbency due to its fine microstructure, characterized by small pore sizes and low surface-connected porosity. These findings establish the bi-layer NiO/YSZ+8YSZ coating as a groundbreaking advancement in thermal-sprayed materials, offering exceptional solar selective and thermal emission properties. This work underscores the transformative potential of APS techniques in developing next-generation coatings tailored for optimised solar thermal applications.

Citation

FAISAL, N.H., RAJENDRAN, V., KANIAPAN, S., RAMALINGAM, V., PRATHURU, A., AHMED, R., KATIYAR, N.K., BANSAL, A., WHITTAKER, T., ISHERWOOD, P., WHITTOW, W., EGIZA, M. and GOEL, S. 2025. Air plasma sprayed multi-material composite coatings for enhanced light absorption and thermal emission. Surface and coatings technology [online], 498, article number 131854. Available from: https://doi.org/10.1016/j.surfcoat.2025.131854

• Journal Article Type: Article
• Acceptance Date: Jan 26, 2025
• Online Publication Date: Jan 28, 2025
• Publication Date: Feb 15, 2025
• Deposit Date: Jan 28, 2025
• Publicly Available Date: Jan 28, 2025
• Journal: Surface and coatings technology
• Print ISSN: 0257-8972
• Electronic ISSN: 1879-3347
• Publisher: Elsevier
• Peer Reviewed: Peer Reviewed
• Volume: 498
• Article Number: 131854
• DOI: https://doi.org/10.1016/j.surfcoat.2025.131854
• Keywords: Air plasma spray; Single-layer coatings; Bi-layer coatings; Light absorption; Thermal emittance; Solar thermal conversion
• Public URL: https://rgu-repository.worktribe.com/output/2675098