| LOU Deyuan,LI Heng,QIU Yuan,JIANG Hongliang,YANG Dongchao,CHEN Chenyang,DONG Chaoshuai,LI Teng,LIU Dun.AlN Superwet Flat Heat Pipes Fabricated by Femtosecond Laser Selective Micro Texturing[J],53(16):182-189 |
| AlN Superwet Flat Heat Pipes Fabricated by Femtosecond Laser Selective Micro Texturing |
| Received:September 02, 2023 Revised:November 14, 2023 |
| View Full Text View/Add Comment Download reader |
| DOI：10.16490/j.cnki.issn.1001-3660.2024.16.015 |
| KeyWord:AlN femtosecond laser micro texturing superhydrophobic superhydrophilic flat heat pipe heat transfer performances |
| Author | Institution |
| LOU Deyuan |
Ultrafast Laser Processing Research Center, School of Mechanical Engineering, Hubei University of Technology, Wuhan , China |
| LI Heng |
Ultrafast Laser Processing Research Center, School of Mechanical Engineering, Hubei University of Technology, Wuhan , China |
| QIU Yuan |
Shenyang Aircraft Corporation, Shenyang , China |
| JIANG Hongliang |
Ultrafast Laser Processing Research Center, School of Mechanical Engineering, Hubei University of Technology, Wuhan , China |
| YANG Dongchao |
Ultrafast Laser Processing Research Center, School of Mechanical Engineering, Hubei University of Technology, Wuhan , China |
| CHEN Chenyang |
Ultrafast Laser Processing Research Center, School of Mechanical Engineering, Hubei University of Technology, Wuhan , China |
| DONG Chaoshuai |
Ultrafast Laser Processing Research Center, School of Mechanical Engineering, Hubei University of Technology, Wuhan , China |
| LI Teng |
Ultrafast Laser Processing Research Center, School of Mechanical Engineering, Hubei University of Technology, Wuhan , China |
| LIU Dun |
Ultrafast Laser Processing Research Center, School of Mechanical Engineering, Hubei University of Technology, Wuhan , China |
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| Abstract: |
| Liquid wicking is one of the key factors determining the heat dissipation capacity of heat pipe. The work aims to study the laser processing of embedding AlN flat heat pipes to enhance the heat dissipation performance of AlN substrates. An integrated flat heat pipe was designed to be embedded in a ceramic substrate. AlN ceramic, known for its high thermal conductivity, was utilized as the material for the capillary core on the plate surface. In the present processing, an ultrafast laser micro texturing technology was employed to fabricate highly-infiltrated integrated flat heat pipes, thereby enhancing heat transfer performance of the ceramic substrate. A superhydrophilic and superhydrophobic composite surface was created on AlN with femtosecond laser micro texturing technology. Additionally, the AlN was subsequently assembled into an embedded plate flat heat pipe to test its heat transfer performance. The heat flux and thermal resistance of the heat pipe were calculated according to the temperature change of measuring point and Fourier's heat conduction law. These three-dimensional surface profile, morphology, oxygen content, and chemical composition were analyzed with three-dimensional optical microscopy, SEM, EDS, and XPS to investigate the formation mechanism of the hydrophilic and hydrophobic surface. The results indicated that the wedge-shaped combination samples had the shortest start-up time and lowest start-up temperature. The samples exhibited a start-up time of approximately 80 s and a start-up temperature of around 81.5 ℃. Compared to the fully superhydrophilic sample, the start-up time and start-up temperature were reduced by 14.9% and 6.0%, respectively. Additionally, the wedge-shaped combination samples exhibited the lowest thermal resistance and the highest heat flux, with a thermal resistance of 0.005 2 K/W and a heat flux of 1 593.1 kW/m2. These values represented a 33% reduction in thermal resistance and a 2% increase in heat flux compared to the fully superhydrophilic sample. SEM observations revealed that after laser texturing and heat treatment, the surface of the AlN ceramic exhibited numerous laminar structures with micrometer-sized pores between them. The AlN surface was covered with scattered nano-villus clusters, which exerted a lifting effect on water droplets and rendered the superhydrophobic surface. However, subsequent micro texturing of the AlN ceramic surface led to the almost complete disappearance of nano-villus clusters, revealing a "bare" sheet structure, and resulting in a superhydrophilic surface. From a surface energy perspective, laser texturing of the AlN ceramic surface generated an inadequate amount of high surface-energy aluminum polyvalent oxide, leading to a superhydrophilic surface. Heat treatment in a constant-temperature oven at 120 ℃ for 24 h, made the surface be oxidized completely. The reactions occurring on the sample surface might involve 2AlN→2Al+N2 and 4Al+3O2→2Al2O3, which subsequently reduced the surface energy and transformed it into a superhydrophobic state. This hybrid superhydrophilic and superhydrophobic surface is beneficial to the rapid transmission of liquid from evaporation end to condensation end in the flat heat pipe, thus enhancing heat transfer performance. The heat pipe fabricated in this study exhibits superior thermal response speed and stability compared to the fully superhydrophilic one, offering a promise for heat dissipation issues in microelectronic devices. |
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