• Membrane Journal
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• v.32 no.6
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• pp.456-464
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• 2022

Hydrogen permeation performance was analyzed by manufacturing Pd and Pd-Cu membranes through electroless plating. As a support for the Pd and Pd-Cu membranes, α-Al₂O₃ ceramic hollow fiber were used. Pd-Cu membrane was manufactured through sequential electroless plating, and then annealing was performed at 500°C, for 18 h in a hydrogen atmosphere to make Pd and Cu alloy. After annealing, the Pd-Cu membrane confirmed that the alloy was formed through EDS (Energy Dispersive X-ray Spectroscopy) and XRD (X-ray Diffraction) analysis. In addition, the thickness of the Pd and Pd-Cu plating layers were measured to be about 3.21 and 3.72 µm, respectively, through SEM (Scanning Electron Microscope) analysis. Hydrogen permeation performance was tested for hydrogen permeation in the range of 350~450°C and 1~4 bar in hydrogen single gas and mixed gas (H₂, N₂). In a single hydrogen gas, Pd and Pd-Cu membranes have flux of up to 54.42 and 67.17 ml/cm²⋅ min at 450 °C and 4 bar. In the mixed gas, it was confirmed that the separation factors of 1308 and 453 were obtained under the conditions of 450 °C and 4 bar.

• Composites Research
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• v.37 no.3
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• pp.204-208
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• 2024

De-icing/anti-icing fluid is essential for removing ice formation on aircraft. It chemically removes ice using organic solvents, which can cause damage to the topcoat surface in the process. In this study, glycol-based deicing/anti-icing fluid was used to remove ice, and the resulting damage to the topcoat was examined. USB microscope was used to observe the formation and growth of ice, while a confocal microscope was employed to observe the surface morphology after treatment with de-icing/anti-icing fluid. Additionally, coating thickness measurements and Fourier transform infrared (FT-IR) analysis were conducted to investigate the physical and chemical changes on the surface. The repeated application of de-icing/anti-icing fluid showed a reduction in the ice formation rate and an increase in the growth rate. Damage during the pressurization process and surface damage to the polyurethane topcoat caused by ethylene glycol were observed during the de-icing process. Although no chemical changes were detected, the analysis revealed that surface uniformity decreased, with physical damage such as cracks and undulations forming on the surface. It was confirmed that while de-icing/anti-icing fluid is effective in removing ice, it also causes surface damage.

• The Journal of Korean Academy of Prosthodontics
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• v.57 no.3
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• pp.211-218
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• 2019

Purpose: The purpose of the present study was to compare the accuracy of four different metal copings fabricated by CAD/CAM technology and to evaluate clinical effectiveness. Materials and methods: Composite resin tooth of the maxillary central incisor was prepared for a metal ceramic crown and duplicated metal die was fabricated. Then scan the metal die for 12 times to obtain STL files using a confocal microscopy type oral scanner. Metal copings with a thickness of 0.5 mm and a cement space of $50{\mu}m$ were designed on a CAD program. The Co-Cr metal copings were fabricated by the following four methods: Wax pattern milling & Casting (WM), Resin pattern 3D Printing & casting (RP), Milling & Sintering (MS), Selective laser melting (SLM). Silicone replica technique was used to measure marginal and internal discrepancies. The data was statistically analyzed with One-way analysis of variance and appropriate post hoc test (Scheffe test) (${\alpha}=.05$). Results: Mean marginal discrepancy was significantly smaller in the Group WM ($27.66{\pm}9.85{\mu}m$) and Group MS ($28.88{\pm}10.13{\mu}m$) than in the Group RP ($38.09{\pm}11.14{\mu}m$). Mean cervical discrepancy was significantly smaller in the Group MS than in the Group RP. Mean axial discrepancy was significantly smaller in the Group WM and Group MS then in the Group RP and Group SLM. Mean incisal discrepancies was significantly smaller in the Group RP than in all other groups. Conclusion: The marginal and axial discrepancies of the Co-Cr coping fabricated by the Wax pattern milling and Milling/Sintering method were better than those of the other groups. The marginal, cervical and axial fit of Co-Cr copings in all groups are within a clinically acceptable range.