Master of Science in Mechanical Engineering (MSME)
Microscale molding replication and transient liquid phase (TLP) bonding were used to fabricate Al-based microchannel heat exchangers (MHEs) and micro gas chromatograph (mGC) columns. Metal-based microchannel heat exchangers often experience corrosion as a result of their operating conditions. To address this problem, an internal anodization method was developed in Al microtubes by pulsing the flow of electrolyte through a microtube when the current dropped below a set value. The anodic aluminum oxide (AAO) films were characterized by scanning electron microscopy (SEM), focused ion beam (FIB) cross sections, and X-ray energy dispersive spectroscopy (EDS) to determine their growth rate and morphology. The AAO was sealed by immersing in near-boiling water, and then subjected to a linear sweep voltammetry corrosion test in NaCl, which showed an order of magnitude decrease in the corrosion current between un-anodized and anodized/sealed microtubes. The anodization process was extended to MHEs, and subsequent corrosion testing showed superior resistance to ion diffusion within the AAO film. Al-based mGC columns were fabricated and tested for carrier gas flow rate and single-compound efficiency, then they were subsequently anodized using the same process as the MHEs at 30V or 50V for 3 hours or 8 hours. They were re-tested for single compound efficiency then used to separate an n-C4 through n-C9 hydrocarbon standard. Comparison with a commercial column of the same length showed that the mGC columns had a lower resolution because of lower retention times for all compounds. Additionally, the n-C8 and n-C9 peaks had significant tailing. On the other hand, the mGC columns had higher efficiency than the commercial column for n-C5, n-C6, and n-C7. Characterization via SEM and EDS showed that inconsistent AAO morphology was one likely cause of the lower resolution and tailing. A series of recommendations for manufacturing improvements were provided, including changes to the anodization process and surface treatment of the AAO to lower the distribution of active site energies.
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Hymel, Paul Joseph, "Fabrication and Enhancement of Aluminum-Based Microchannel Devices" (2014). LSU Master's Theses. 3045.
Meng, Wen Jin