The efficacy of sodium hypochlorite (NaOCl) solution as a cleaning and bactericidal agent against Pseudomonas fluorescens was studied as a function of pH. Alumina (Al2O3) particles on which P. fluorescens cells were irreversibly adhered were cleaned with NaOCl solutions of pH 5 to 12 containing free available chlorine (AC) of 120 to 1000mg/L. The efficiency of the removal of P. fluorescens cells from the Al2O3 surfaces increased with increasing pH and the AC concentration. It was found that the efficacy of NaOCl solution as a cleaning agent depended on the concentration of the dissociated hypochlorite ion (-OCl). On the other hand, the bactericidal activity of NaOCl solution of 2.5mg AC/L increased with decreasing pHs from 9.3 to 5.7. The logarithmic relative reductions of viable P. fluorescens were proportional to the product of the AC concentration and time, and the rate of inactivation depended on the concentration of undissociated hypochlorous acid (HOCl). Our results show that the cleaning and bactericidal activities of NaOCl solution are governed by the percentage of HOCl and -OCl existing in the solution.
It is known that when surface roughness is changed, that the adhesiveness of CVD diamond thin film also changes. However, it has not been clarified whether the cause of this is based on an increase of mechanical bonding strength or based on an increase in chemical bonding strength accompanying the change in nucleation density due to the change in surface roughness. To clarify whether the underlying factor is mechanical bonding strength or chemical bonding strength, nucleation density and adhesiveness were evaluated. In order to evaluate the influence of surface roughness only, polishing was performed with single-phase Mo abrasive paper to prepare substrates with different surface roughness, and film formation of diamond thin films was done using the microwave plasma CVD method. Measurement of nucleation density of the diamond thin film was done using an SEM (Scanning Electron Microscope) and adhesiveness was evaluated using the ultrasonic cavitation method. No significant difference in nucleation density was observed as a result of changing the surface roughness. However, ultrasonic cavitation tests revealed that the damaged area tended to increase as the surface roughness became smaller. In particular, it deteriorated sharply when the elevation difference of polishing marks was approximately equal to or less than the film thickness (Ra=200nm) of the diamond thin film. These results indicate that, rather than the influence of nucleation density, changing the surface roughness itself has a direct effect on the mechanical bond : when the elevation difference of polishing marks is relatively small compared to the film thickness, the mechanical bond (anchor effect) becomes weaker, allowing the surface to become damaged more easily.
This study examined the effects of alloying elements on zincate treatment and adhesion of electroless Ni-P coating onto various aluminum alloy substrate. Surface morphology of zinc deposition from the single zincate treatment and its adhesion were changed, depending on the alloying element. The zinc deposition from the double zincate treatment became thinly uniform, and the adhesion between aluminum alloy substrate and Ni-P coating was improved irrespective of the alloying element. However, the adhesion of A7075P aluminum alloy was inferior to that of other alloys.
Crystal orientations of copper film electrodeposited from the acid copper sulfate electrolyte in the presence of acetonitrile were investigated by X-ray diffraction pattern. It was found that the main crystal orientation of the electrodeposited copper film was the 111 plane and that the orientation varied depending on the acetonitrile concentration, the current density, the bath temperature and the cuprous ion concentration. It was considered that the preferred crystal orientation originated from selective adsorption of acetonitrile on the 111 plane.