Faculty Publications

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Effect of current density during electrodeposition on microstructure and hardness of textured Cu coating in the application of antimicrobial Al touch surface
(Elsevier Ltd, 2016) Augustin, A.; Huilgol, P.; Udupa, K.R.; Bhat, K.U.
Copper is a well proven antimicrobial material which can be used in the form of a coating on the touch surfaces. Those coating can offer a good service as touch surface for very long time if only they possess good mechanical properties like scratch resistance and microhardness. In the present work the above mentioned mechanical properties were determined on the electrodeposited copper thin film; deposited on double zincated aluminium. During deposition, current density was varied from 2 A dm?2 to 10 A dm?2, to produce crystallite size in the range of 33.5 nm to 66 nm. The crystallite size was calculated from the X-ray peak broadening (Scherrer?s formula) which were later confirmed by TEM micrographs. The scratch hardness and microhardness of the coating were measured and correlated with the crystallite size in the copper coating. Both characteristic values were found to increase with the reduction in crystallite size. Reduced crystallite size (Hall–Petch effect) and preferred growth of copper films along (111) plane play a significant role on the increase in the hardness of the coating. Further, TEM analysis reveals the presence of nano-twins in the film deposited at higher current density, which contributed to a large extent to the sharp increase of coating hardness compared to the mechanism of Hall–Petch effect. The antimicrobial ability of the coated sample has been evaluated against Escherichia coli bacteria and which is compared with that of commercially available bulk copper using the colony count method. 94% of E. coli cells were died after six hours of exposure to the copper coated surface. The morphology of the copper treated cells was studied using SEM. © 2016 Elsevier Ltd
Development of adherent antimicrobial copper coatings on stainless steel for healthcare applications
(Springer, 2023) Bharadishettar, N.; Bhat, K.U.; Bhat, K.S.
Copper coatings were fabricated using an environmentally sustainable non-cyanide electrodeposition technique. By following four-stage acid pickling treatment of the substrate and optimum parameters during electrodeposition, adhesion strength up to 9 MPa was obtained. Four different copper coatings were fabricated by varying CuSO4. 5H2O concentration in an electrolyte (10, 15, 30, and 45 g/L) to understand nucleation and growth mechanism and surface texture evolution. Nano-nodular morphology of the deposited copper marks a significant feature. It increases the fraction of grain boundaries in it. The grazing incidence X-ray diffraction analysis revealed the preferred orientation along the (111) plane with the presence of residual compressive stresses (in the range of 24.90–273.92 MPa). Surface texture studies indicated that the coating had an abundance of nano-scaled protruding structures with surface roughness’s Sa in the range of 2.507–1.674 µm (Ra in a range of 1.714–1.235 µm). It offers 3D contact with microbes. The developed coating had increased hardness (41.93%), scratch resistance (58.77%), and 9 MPa adhesion strength with the substrate. Initially, copper coatings had hydrophobicity against water (initial contact angle in the range of 134–139°). The extent of hydrophobicity decreased with exposure time. The developed coatings exhibited significant antimicrobial activity. Antimicrobial studies using the cell viability technique indicated that the coating exhibits toxicity against Escherichia coli (ATCC25922) and Staphylococcus aureus (MCC2408) microbes. 100% reduction of the survival of microbes is observed after 4 h of exposure. Graphical Abstract: [Figure not available: see fulltext.]. © 2023, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.

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