• 한국생물공학회:학술대회논문집
• /
• 2001.11a
• /
• pp.545-548
• /
• 2001

Microbiologically influenced corrosion (MIC) of metal is common in the natural environment and sulfate reducing bacteria are representative microorganisms for MIC. We found that biofilm fomlation by SRB on the metal surface might be controlled by quorum sensing, which is a cell density dependent regulation of cell metabolism. As cell free culture fluids (spent media) of Desulfovibrio vulgaris and D. desulfuricans were tested for quontrn sensing related test strains, it was found that spent media of two SRB induced increased luminescence of Vibrio harveyi BB886 (sensor 1+, sensor 2-) and BB170 (sensor 1-, sensor 2+). Quorum activities of D. vulgaris and D. desulfuricans appeared to be parallel to growth patterns, i.e., it was low in the lag phase, highly increased in the exponential phase, and reached maximum in the stationary phase. Interestingly, however, luminescence of V. harveyi BB886 and BB170 induced by a unit cell mass of the SHB showed a maximal peak in the late lag phase. Hence, it was suspected that quorum sensing of these two SHB play unknown roles in shifting cells from dormant to growth stages.

• Journal of Welding and Joining
• /
• v.27 no.6
• /
• pp.74-79
• /
• 2009

Titanium and titanium alloy can be reproduced immediately even if oxide films($TiO_2$) break apart in sea water. Therefore, since titanium demonstrates large specific strength and outstanding resistance to stress corrosion cracking, crevice corrosion, pitting and microbiologically influenced corrosion in sea water environment, it has been widely applied to heat exchanger for ships. In particular, with excellent elongation, pure titanium may be deemed as optimal material for production of heat exchanger plate which is used with wrinkles formed for efficient heat exchange. Conventional plate type heat exchanger prevented leakage of liquid through insertion of gasket between plates and mechanical tightening by bolts and nuts, but in high temperature and high pressure environment, gasket deterioration and leakage occur, so heat exchanger for LPG re-liquefaction device etc do not use gasket but weld heat exchanger plate for use. On the other hand, since welded plate cannot be separated, it is important to obtain high quality reliable welds. In addition, for better workability and production performance, lasers that can obtain weldment with large aspect ratio and demonstrate fast welding speed even in atmospheric condition not in vacuum condition are used in producing products. So far, 1st report and 2nd report compared and analyzed embrittlement degrees by bead colors of weldment through quantitative analysis of oxygen and nitrogen and measurement of hardness as fundamental experiment for the evaluation of titanium laser welding, and evaluated the welding performance and mechanical properties of butt welding. This study welded specimens in various conditions by using laser and GTA welding machine to apply edge welding to heat exchanger, and evaluated the mechanical strength through tensile stress test. As a result of tensile test, laser weldment demonstrated tensile strength 4 times higher than GTA welds, and porosity could be controlled by increasing and decreasing slope of laser power at overlap area.

• Korean Journal of Materials Research
• /
• v.16 no.10
• /
• pp.639-646
• /
• 2006

Over the last two decades, microbiologically influenced corrosion (MIC) of metallic materials has received considerable attention due to its serious effects on industrial field. In this context, it is important to devise control methods which inhibit biofilm formation on various metallic compounds and are compatible with environment. It was change of various conditions (duty cycle, current density, $AgNO_3$ concentration and pH) for injection of Ag particles in anodized Aluminum alloy pore using pulsed current. Optimal condition was obtained by means of FE-SEM, ICP analysis etc. The antibacterial metal's specimen were manufactured under optimal condition and this specimen were tested the antibacterial characterization and anticorrosion characterization. In result of test, we can confirmed that the antibacterial characterization and anticorrosion characterization of the specimens of injected Ag particles in anodized Aluminum alloy pore using pulsed current were better than the anodized Aluminum alloy specimens.