In this study, Ag2O was synthesized on polyethylene terephthalate fabrics by using an ultrasonic technique with Ag ion reduction in an aqueous solution. The effects of pH on the microstructure and antibacterial properties of the fabrics were evaluated. X-ray diffraction confirmed the presence of Ag2O on the fabrics. The fabrics were characterized by Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy, and wettability testing. Field-emission scanning electron microscopy verified that the change of pH altered the microstructure of the materials. Moreover, the antibacterial activity of the fabrics against Escherichia coli was related to the morphology of Ag2O particles. Thus, the surface structure of Ag2O particles may be a key factor of the antibacterial activity.
Aluminium alloys are lightweight materials relatively used in automotive industries. However, welding using the conventional welding methods is known to be difficult. In this study, the friction stir welding (FSW) known as the solid state joining process was extensively used for joining similar and dissimilar 5 mm aluminium alloy plates. The butt-joint type of similar joints (AA5083-AA5083) and dissimilar joints (AA5083-AA6061) were carried out under the same welding parameters; 1000 rpm (rotational speed) and 100 mm/min (transverse speed). Macro-and microstructural observations were acquired at the cross-section of the weld regions by stereo and optical microscopes. The microstructural study showed that the formation of 'onion ring' structure was detected in the nugget zone of similar joints, while wavy and distorted patterns appeared in dissimilar joints. All tensile specimens of similar welding joint showed similar fracture patterns where all fractures occurred in the thermo-mechanically affected zone (TMAZ). However, tensile specimens of dissimilar welding joint broke up at the TMAZ region as well as at Al6061 base metal at the retreating side. The tensile strength of similar joint and dissimilar joint was 22% and 19% lower compared to the base metal of Al5083 and Al6061.
In this study, continuous multi-pass friction stir welding was used to clad dissimilar AA6061 aluminium (Al) and C2801P copper (Cu) alloy materials. The empirical relationships between three process parameters and two-factor responses of Al–Cu clad joints were evaluated. Mathematical models were generated using regression analysis to predict the variation in tensile shear and peel load of the cladded joints. The sufficiency of the developed model was validated by analysis of variance (ANOVA), and the multi-criterion optimisation of factor responses was carried out via the response surface method. Results showed the formation of mechanical interlocking at the cladded interface and the development of a thin metallurgical bonding layer consisting of Al alloy content (8–21%), which greatly affected the quality of the Al–Cu joint interface. Moreover, the increase in shoulder overlap ratio, welding speed and tool rotational speed improved the shear and peel strength up to a certain range before gradually declining. The optimised process parameters for the cladded Al–Cu were obtained at a rotational speed of 986 r/min, welding speed of 8.6 mm/min and shoulder overlap ratio of 35%. The cladded Al–Cu generated a shear strength of 5850 kPa and peel strength of 750 kPa with an overall desirability function of 0.94.
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