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3Laser treatment of materials to obtain superhydrophilicity for controlling heat exchange
S.V. Starinskiy1'2*, M.M. Vasiliev12, Y.G. Shukhov1, A.A. Rodionov1, V.S. Sulyaeva3
1- S.S. Kutateladze Institute of Thermophysics SB RAS, Lavrentyev Ave. 1, 630090 Novosibirsk, Russia 2- Novosibirsk State University, Pirogova Str. 2, 630090 Novosibirsk, Russia 3- A.V. Nikolaev Institute of Inorganic Chemistry SB RAS, Lavrentyev Ave. 3, 630090 Novosibirsk, Russia
This study examines the influence of the surrounding environment on the properties of copper, nickel, and tin during nanosecond laser processing [1]. By comparing the results of processes conducted in vacuum and air, we conclude that changes in wetting properties cannot be solely attributed to development of surface microstructure. To elucidate this phenomenon, we conducted model experiments using a tin target. Laser processing parameters for the tin target were established, involving deep cavity melting without ablation, resulting in highly evolved material morphology. Under these conditions, laser processing in air did not lead to metal hydrophilization. Therefore, our study demonstrates that the primary cause of changes in material wetting properties during nanosecond laser processing is the re-deposition of ablation products onto the material surface. These products form a nanoporous layer that enhances wicking capabilities and subsequently serves as a sorbent for various impurities, gradually leading to the hydrophobization of most commonly used materials. The proposed mechanism opens the possibility for the development of new methods to create materials with biphilic and anisotropic wetting properties. The key insight lies in the control of the thickness of the nanoporous layer, as it emerges as a pivotal factor dictating wettability properties and wicking capability.
Based on the obtained data, we prepared samples with different wetting properties. The materials were used to analyze the micro and nanostructure at the Leidenfrost point and the dynamics of water droplet boiling on overheated surfaces. Optimization issues are discussed in terms of enhancing the heat dissipation characteristics of the materials. The obtained materials are considered as a basis for creating devices characterized by high-intensity heat exchange during the phase transition of liquid to vapor under conditions of liquid contact with a surface possessing hierarchical micro-/nanotexture. Special attention will be given to the possibility of using unique wetting properties to control heat exchange processes.
"Investigation supported by № 24-19-00664, https://rscf.ru/project/24-19-00664/"
[1] M.M. Vasiliev, Y.G. Shukhov, A.A. Rodionov, V.S. Sulyaeva, D.M. Markovich, S.V Starinskiy, Why do metals become superhydrophilic during nanosecond laser processing? Design of superhydrophilic, anisotropic and biphilic surfaces, Appl. Surf. Sci. 653 (2024) 159392.
