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 this paper, nano-crystalline Cu powder with a mean crystallite size of 45 nm and commercial micron-size Cu powder were either hot pressed or cold pressed and sintered conventionally to fabricate bulk samples. Hardness, density, crystallite size and microstructure of the samples after consolidation were examined. The results show that the hardness of the hot pressed nano-crystalline Cu is in the range of 0.75-1.2 GPa which is higher than that of commercial Cu. The density of the bulk nano-crystalline sample showed that the rising sintering temperature increases the density up to 97% of the theoretical value. The mean crystallite size of the hot pressed sample was 64 nm, which still was in the nano scale. The scanning electron microscopy (SEM) images revealed that the hot pressed samples contain less porosities compared to the conventionally consolidated samples.

Electron Beam-Physical Vapor Deposition (EB-PVD) is being used in coating component for many applications such as electronic industry for producing nanostructures and ICs coatings. In this work, nanostructured copper was deposited on glass using EB-PVD technique. Surface and elemental characteristics of EB-PVD coatings investigated and evidenced corrosion resistance of nanostructured coatings produced by this technique are higher than Cu sheet in chloride media.

Ultrafine grained copper processed by 4 cycles of equal angular pressing was fatigued to study the growth behavior of a small crack. After the crack initiation, the behavior of a major crack was monitored through plastic replication technique, showing that the crack growth rate is proportional to the crack length regardless of stress amplitudes. The crack growth rate of major cracks was evaluated by a term σ_aⁿl, not by the stress intensity factor range, ΔK. Analysis on fracture surfaces by scanning electron microscopy showed a planar followed by a striated surface. The formation mechanism of fracture surface morphologies was discussed by considering the average grain size and the reversible plastic zone size at a crack tip.

In this paper a mathematical model for femtosecond laser ablation of metals is proposed, based on standard two-temperature model connected with 1D hydrodynamic equations. Wide-range equation of state has been developed. The simulation results are compared with experimental data for aluminium and copper. A good agreement for both metals with numerical results and experiment shows that this model can be employed for choosing laser parameters to better accuracy in nanoparticles production by ablation of metals.