Narrow Results

A Cu film with the ability to rapidly inactivate the COVID-19 virus was easily fabricated at approximately 23${}^{\circ }$C on a Na-free glass substrate. The well-adhered Cu films with thickness of approximately 16 $\mu$m and surface area of 8.71 10${}^{-3}$ m² g${}^{-1}$ were obtained by immersion of the glass substrate into an aqueous solution with dissolved Cu (II) complex of ammonia and ascorbic acid. The interface bonded between the film and glass substrate was very strong, such that the film did not peel off even when it was exposed to an ultrasonic wave of 100 mW (42 kHz) in water. The anti-COVID-19 activity in Dulbecco’s modified Eagle’s medium (DMEM) is effective within 2 h and is faster than that of commercial copper plates. The changes in the relative abundance of Cu₂O and CuO crystallines on the Cu film due to DMEM treatment and those in surface morphology were examined by X-ray diffraction peak analysis and field emission-scanning electron microscopy, respectively. The flame atomic absorption analyses of the recovered solutions after DMEM treatment indicated that the Cu ions from the Cu film with DMEM treatment for 1 hour at a concentration of 0.64 ± 0.03 ppm were eluted 2.3 times faster than those from the Cu plate. The rapid elution of Cu ions from Cu₂O crystallines on the film in the early stage is the primary factor in the inactivation of the COVID-19 virus, as elucidated from the time dependence of eluted Cu ions by DMEM treatment. Results from thermogravimetric and differential thermal analysis (TG-DTA) of the powder scratched from the Cu film suggested that a trace amount of organic residues remaining in the Cu film was important in the rapid activity.

In our previous study, we examined the influence of the fatigue properties of the stainless steel coated with TiN film and clarified the influence of TiN coating and the surface roughness on the fatigue property. In this study, the four point bending fatigue crack growth tests were carried out for martensitic stainless steel coated with TiN film deposited by arc ion plating method in order to investigate the effect of surface finishing on the fatigue crack behavior for film coated material. The fatigue crack growth behavior was evaluated using the replica method. As a result, the crack propagation rate of mirror polished specimens were lower than that of rough surface specimens. The crack propagation rate was especially decreased for TiN coatings deposited on the mirror polished substrate. The surface roughness near the crack initiation site increased after fatigue test. It concludes that the surface roughness of substrate influences crack propagation rate and the deposition of TiN film affected influenced crack propagation rate and fatigue strength when the surface roughness of substrate is small enough.