Search Results (3)

In this work, a copper coating is developed on a carbon steel substrate by exploiting the superwetting properties of liquid copper. We characterize the surface morphology, chemical composition, roughness, wettability, ability to release a copper ion from surfaces, and antibacterial efficacy (against Escherichia coli and Staphylococcus aureus). The coating shows a dense microstructure and good adhesion, with thicknesses of approximately 20–40 µm. X-ray diffraction (XRD) analysis reveals that the coated surface structure is composed of Cu, Cu₂O, and CuO. The surface roughness and contact angle measurements suggest that the copper coating is rougher and more hydrophobic than the substrate. Inductively coupled plasma atomic emission spectroscopy (ICP-AES) measurements reveal a dissolution of copper ions in chloride-containing environments. The antibacterial test shows that the copper coating achieves a 99.99% reduction of E. coli and S. aureus. This study suggests that the characteristics of the copper-coated surface, including the chemical composition, high surface roughness, good wettability, and ability for copper ion release, may result in surfaces with antibacterial properties. Full article

We suggest a simple idea of bio-based adhesives with strong adhesion even under water. The adhesives simply prepared via polycondensation of 3,4-dihydroxyhydrocinnamic acid (DHHCA) and lactic acid (LA) in one pot polymerization. Poly(DHHCA-co-LA) has a hyperbranched structure and demonstrated strong dry and wet adhesion strength on diverse material surfaces. We found that their adhesion strength depended on the concentration of DHHCA. Poly(DHHCA-co-LA) with the lowest concentration of DHHCA showed the highest adhesion strength in water with a value of 2.7 MPa between glasses, while with the highest concentration of DHHCA it exhibited the highest dry adhesion strength with a value of 3.5 MPa, which was comparable to commercial instant super glue. Compared to underwater glues reported previously, our adhesives were able to spread rapidly under water with a low viscosity and worked strongly. Poly(DHHCA-co-LA) also showed long-term stability and kept wet adhesion strength of 2.2 MPa after steeping in water for 1 month at room temperature (initial strength was 2.4 MPa). In this paper, Poly(DHHCA-co-LA) with strong dry and wet adhesion properties and long-term stability was demonstrated for various kinds of applications, especially for wet conditions. Full article

Ceramic-metal composites with novel performance are desirable materials; however, differences in their properties result in difficulties in joining. In this study, the joining of metal to ceramic is investigated. We recently succeeded in causing super-spread wetting on the surface fine crevice structures of metal surfaces produced by both laser irradiation and reduction-sintering of oxide powders. In this work, joining copper onto an Al₂O₃ plate was achieved by taking advantage of super-spread wetting. Fe₂O₃ powder was first sintered under reducing conditions to produce a microstructure which can cause super-spread wetting of liquid metal on an Al₂O₃ plate. A powder-based surface fine crevice structure of metallic iron with high porosity was well-formed due to the bonding of the reduced metallic iron particles. This structure was joined on an Al₂O₃ plate with no cracking by the formation of an FeAl₂O₄ layer buffering the mismatch gap between the thermal expansion coefficients of iron and Al₂O₃. We successfully achieved metalizing of the Al₂O₃ surface with copper without interfacial cracks using super-spread wetting of liquid copper through the sintered metallic iron layer on the Al₂O₃ plate. Then, laser irradiation was conducted on the surface of the copper-metalized Al₂O₃ plate. A laser-irradiated surface fine crevice structure was successfully created on the copper-metalized Al₂O₃ plate. Moreover, it was confirmed that the super-spread wetting of liquid tin occurred on the laser-irradiated surface fine crevice structure, finally accomplishing the joining of a copper block and the copper-metalized Al₂O₃. Full article