M. K. Punith Kumar

Electrochemical exfoliation of graphite to produce graphene using tetrasodium pyrophosphate

An electrochemical exfoliation based synthetic methodology to produce graphene is provided. An eco-friendly and non-toxic tetrasodium pyrophosphate solution in which the pyrophosphate anion acts as an intercalating ion was used as the electroactive media. Five different ion intercalation potentials were used. Characterization by microscopy, X-ray diffraction, Raman spectroscopy and UV-Visible spectroscopic techniques confirmed that all the potentials produced nano to micrometer sized graphene sheets. No trace of graphene oxide was detected. It was observed that (i) an increase in the intercalation potential increased the graphene yield and (ii) the defect density of graphene did not change significantly with a change in the intercalation potential.

Electrochemical behavior of Zn–graphene composite coatings

A Zn–graphene composite coating was electrodeposited on mild steel. The graphene was synthesized by electrochemical exfoliation of graphite. Electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction techniques were used to characterize the coatings. Compared to a pure Zn coating, the Zn–graphene coating exhibited reduced grain size, reduced surface defects, hillock structures over the coating surface and an altered texture. The corrosion behavior of the coatings was examined by Tafel polarization and electrochemical impedance spectroscopic methods. A significant improvement in the corrosion resistance in terms of reduction in corrosion current and corrosion rate and increase in polarization resistance was noted in the case of the Zn coating containing graphene.

Electrochemical behavior of Sn-graphene composite coating

The electrochemical properties of pure Sn and Sn-graphene composite coating have been determined and compared. Coatings were electrodeposited on mild steel substrates. Graphene was synthesized by the electrochemical exfoliation process using SO42- ion as the intercalating agent. Morphological and structural characterization results revealed a clear effect of graphene on altering the texture, grain size and morphology of the coating. Corrosion behavior was analyzed through potentiodynamic polarization and electrochemical impedance spectroscopic methods. A significant improvement in the corrosion resistance in terms of reduction in corrosion current and corrosion rate and increase in polarization resistance was noted in case of Sn coating containing graphene.

Electrochemical exfoliation of graphite for producing graphene using saccharin

A green electrochemical exfoliation route to produce graphene from graphite electrode has been provided. Saccharin which is a non-toxic and biocompatible artificial sweetener was used as an intercalating agent in aqueous media. Graphene samples were produced using five different exfoliation potentials. Microscopic and spectroscopic analysis confirmed the presence of few layer graphene sheets in as-exfoliated product. Important observations made were: (a) graphene layers from nano-to-micro meter sizes were produced; (b) number of graphene layers decreased with increase in the intercalation potential, (c) yield of graphene increased with increase in the exfoliation potential and (d) defect density in the exfoliated graphene layer was sensitive to the exfoliation potential in a way that with increase in the exfoliation potential the defect density initially increased and then eventually decreased.

Electrochemical behaviour of chromium-graphene composite coating

This work illustrates the role of graphene in enhancing the corrosion resistant properties of chromium–graphene composite coating when compared to the corrosion resistant properties of pure chromium coating containing ZnO nanoparticles. Chromium based coatings have been used extensively due to their various useful attributes such as corrosion and wear resistance and enhanced surface finish. In this work, Cr and Cr–graphene composite coatings were electrodeposited over mild steel substrate using Cr(III) plating bath. To deposit the coatings, an electrodeposition method was also adopted due to its attributes such as low cost, less equipment intensive methodology, accuracy of reproduction and suitability for large scale surface modification. Three different coatings were produced: (a) Cr coating containing ZnO nanoparticles (C), (b) Cr coating containing ZnO nanoparticles deposited using formic acid (CF) and (c) Cr coating containing ZnO nanoparticles and graphene deposited using formic acid (CFG). Graphene used in the deposition process was produced from the electrochemical exfoliation of graphite in sodium lauryl sulphate (SLS) electroactive media. ZnO nanoparticles were synthesized using the precipitation method followed by calcination. Microstructural characterization of the coatings revealed that the coating ‘C’ contained large cracks. Addition of formic acid (in the coating CF) noticeably reduced the cracks in the coating which now also contained hillock structures. Addition of graphene (in coating CFG) further enhanced the coating morphology which now contained negligible cracks and increased hillock structures completely covering its surface. Diffraction analysis revealed that the addition of graphene also altered the texture of the chromium coatings. Potentiodynamic polarization and electrochemical impedance spectroscopic analysis revealed that the change in the morphology and microstructure of the deposit due to the addition of graphene substantially enhanced the corrosion resistance of the CFG coating when compared to both C and CF coatings.

Enhancement of Corrosion Resistance of Zinc Coatings Using Green Additives

In the present work, morphology, microstructure, and electrochemical behavior of Zn coatings containing non-toxic additives have been investigated. Zn coatings were electrodeposited over mild steel substrates using Zn sulphate baths containing four different organic additives: sodium gluconate, dextrose, dextrin, and saccharin. All these additives are “green” and can be derived from food contents. Morphological and structural characterization using electron microscopy, x-ray diffraction, and texture co-efficient analysis revealed an appreciable alteration in the morphology and texture of the deposit depending on the type of additive used in the Zn plating bath. All the Zn coatings, however, were nano-crystalline irrespective of the type of additive used. Polarization and electrochemical impedance spectroscopic analysis, used to investigate the effect of the change in microstructure and morphology on corrosion resistance behavior, illustrated an improved corrosion resistance for Zn deposits obtained from plating bath containing additives as compared to the pure Zn coatings.

Investigation of the inhibition effect of ibuprofen triazole against mild steel corrosion in an acidic environment

The inhibition performance of ibuprofen triazole (IT) on mild steel (MS) corrosion in 1.0 M HCl and 0.5 M H2SO4 has been investigated by using electrochemical (potentiodynamic polarization and electrochemical impedance spectroscopy), gravimetric, and quantum chemical studies. Electrochemical investigation indicates that IT hampers MS corrosion via adsorption through a mixed inhibition mechanism. The protection ability of IT increases with an increasing concentration of inhibitor and decreases with increasing temperature. The adsorption of IT molecules on MS surface follows the Langmuir adsorption isotherm. Certain quantum chemical parameters were calculated to ascertain the correlation between inhibitive effect and molecular structure of IT.

Self assembly based 3D heatsink antenna for high density 3D integration

Heatsinks are typically designed near the power amplifier in a wireless transmission circuit. The radiations from heatsinks are undesirable to the nearby antenna component and should be minimized to reduce electromagnetic interference (EMI). However, in certain applications the heatsink components are in the circuit is unavoidable. The use of heatsink as a transmitting or receiving electromagnetic radiation will be of significant value if heatsink is designed as an antenna, instead of having two separate components: antenna and heatsink. This paper investigates the radiation property of heatsinks as an antenna at two different frequencies: low (2.4 GHz) and high (24 GHz) frequencies. The fabrication of heatsink antennas depend on the designed resonant frequency. As the antennas are made smaller, their resonant frequency increases. Building millimeter-wave capable antennas via conventional semiconductor processing techniques becomes feasible. The fabrication of high frequency on-chip 3D heatsink antennas can be visualized using a novel self assembly process. The self assembly (SA) technique is driven by surface tension property to pull 2D metal patterns into 3D structures. The SA method involves conventional semiconductor steps with an additional dip soldering and reflow steps to develop 3D heatsinks. The 3D heatsink shows improved antenna properties at low and high frequencies.