A DLC-Punch Array to Fabricate the Micro-Textured Aluminum Sheet for Boiling Heat Transfer Control

Abstract

A diamond-like carbon (DLC) film, coated on an SKD11 (alloy tool steel) substrate, was shaped by plasma oxidation to form an assembly of DLC macro-pillars and to be used as a DLC-punch array that is micro-embossed into aluminum sheets. First, the SKD11 steel die substrate was prepared and DLC-coated to have a film thickness of 10 μm. This DLC coating worked as a punch material. The two-dimensional micro-patterns were printed onto this DLC film by maskless lithography. The unprinted DLC films were selectively removed by plasma oxidation to leave the three-dimensional DLC-punch array on the SKD11 substrate. Each DLC punch had a head of 3.5 μm × 3.5 μm and a height of 8 μm. This DLC-punch array was fixed into the cassette die set for a micro-embossing process using a table-top servo-stamper. Furthermore, through numerically controlled micro-embossing, an alignment of rectangular punches was transcribed into a micro-cavity array in the aluminum sheet. The single micro-cavity had a bottom surface of 3.2 μm × 3.2 μm and an average depth of 7.5 μm. A heat-transfer experiment in boiling water was also performed to investigate the effect of micro-cavity texture on bubbling behavior and the boiling curve.

Pico- and Femtosecond Laser Micromachining for Surface Texturing

“…Microtextures with the size in the order of 1-100 μm on the solid surface and interface work to reduce the friction and wear, to assist the joinability, and to functionalize the surfaces and interfaces [15]. Micromilling [16] and microelectrical discharge machining (micro-EDM) [17] have been utilized to make microtexturing onto the steel surfaces.…”

Plasma Oxidation Printing into DLC and Graphite for Surface Functionalization

“…Thick DLC films were coated on the AISI420J2 stainless steel substrates by MF-AC PECVD (Mid-range Frequency-Alternative Current Plasma Enhanced Chemical Vapor Deposition) process [9]. In the following experiments, the film thickness was constant at 10 µm, as depicted in Figure 3a.…”

“…Maskless lithography with the spatial resolution of 1 µm was utilized to print the two-dimensional micro-patterns. In a similar manner to [9], the nano-carbon and aluminum deposit prints with the total thickness of 140 nm were utilized for micro-patterning since they had sufficient erosion toughness not to be delaminated or broken away, even after plasma oxidation for 36 ks. A square dot pattern with the unit size of 3.5 µm × 3.5 µm was printed onto the DLC film surface with a pitch of 5 µm.…”

Micro-/Nano-Texturing of Aluminum by Precise Coining for Functional Surface Decoration

“…The overall heat penetration capacity of an aluminum heat sink was improved by its microtextures [6,7]. The boiling heat transfer process was enhanced by micro-/nano-textures on the pure aluminum and copper devices [8][9][10]. In addition to these nano-texturing effects on the surface and engineering fields, various mini-/micro-/nano-textured metallic sheets and plates are necessary in mass for health-control and medical operations to deal with medicines, polymer parts, cells, viruses, etc.…”