Dr. Karthega M. currently serves as Assistant Professor in Physics, Department of Sciences, School of Engineering, Coimbatore Campus. Her areas of research include Biomaterials and Comorian.


Publication Type: Journal Article

Year of Publication Title


E. Joseph, Madhusudanan, S. P., Mohanta, K., Dr. Karthega M., and Sudip Kumar Batabyal, “Multiple negative differential resistance in perovskite (CH 3 NH 3 PbI 3) decorated electrospun TiO 2 nanofibers”, Applied Physics A, vol. 126, no. 9, pp. 1–8, 2020.[Abstract]

Polyvinyl alcohol and titanium dioxide nanofibers have been synthesized through the electrospinning method. CH3NH3PbI3 microcrystals were deposited over TiO2 nanofiber through a chemical bath deposition method. In this report, we have discussed the electrical properties of the CH3NH3PbI3 decorated TiO2 nanofibers. Multiple negative differential resistance (multiple peaks) was observed in perovskite (CH3NH3PbI3) decorated polyvinyl alcohol-titanium dioxide composites nanofibers when 2 V bias was applied. Polyvinyl alcohol-titanium dioxide composite nanofibers have been characterized by scanning electron microscope, fourier transform infrared spectra and X-ray diffraction. “Write–read–erase–read” sequence of the electrical response of the composites was probed to determine the memory applications. Electrochemical impedance spectroscopy (EIS) was investigated to determine the charge confinement in the perovskite decorated nanofiber in the high- and low-conducting states.

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Dr. Karthega M., “A novel surface modification method On titanium and its alloys using Hydrogen peroxide for biomedical Applications”, 2014.[Abstract]

Human beings are likely to face serious problems caused by newlineDiseases accidents and aging during their lifetime In the past physicians had newlinea very limited number of material choices for implantation to solve these newlinemedical problems However in the recent years significant advances in newlinescience and technology of medical materials have altered the choices of newlinephysicians to develop new materials for the solution of the implantation newlineproblems Now a days much attention has been focused on titanium for its newlineuse in medical and dental fields owing to its superior properties such as low newlinedensity high corrosion resistance and satisfactory biocompatibility However newlinedirect ossteointegration of such implant materials is one of the main goals of newlinebiomaterial research for dental and orthopedic applications Hence chemical newlinemechanical or biological treatments have been investigated to obtain a faster newlinebetter and durable bonding of implants with bone newlineIn recent years to improve ossteointegration scientists have focused newlinetheir attention on the interface interactions between the implant surface and newlinethe bone In particular many efforts have focused on the modification of a newlinestable and thin oxide layer formed spontaneously on the surface of titanium newline. More »»


Dr. Karthega M. and Rajendran, N., “Formation of nanoporous oxide layer over a binary $\beta$-phase titanium in simulated body fluid”, Journal of Porous Materials, vol. 19, pp. 573–577, 2012.[Abstract]

In the present investigation, the surface of Ti-15Mo ($\beta$-Ti) alloy was oxidized using hydrogen peroxide (H2O2) and the layer was densified by thermal treatment. Morphological characterization of treated surface by Field Emission Scanning Electron Microscope (FE-SEM) revealed the formation of nanoporous layer. Electrochemical studies of H2O2 treated specimen exhibited higher corrosion resistance in simulated body fluid (SBF) solution compared to untreated $\beta$-Ti alloy. Further, the formation of nanoporous layer and their electrical components were evinced from impedance studies by fitting it to an circuit model. More »»


Y. Sasikumar, Dr. Karthega M., and Rajendran, N., “In Vitro Bioactivity of Surface-Modified $\beta$-Ti Alloy for Biomedical Applications”, Journal of Materials Engineering and Performance, vol. 20, pp. 1271–1277, 2011.[Abstract]

Ti-15Mo ($\beta$-Ti) alloy was subjected to chemical followed by thermal treatment for the enhancement of in vitro bioactivity and corrosion resistance. The surface-modified specimens were characterized using scanning electron microscopy (SEM) and energy dispersive x-ray analysis (EDAX). The results indicated the formation of nanoporous layer and flake-like structure developed during chemical and subsequent thermal treatments. The in vitro bioactivity of the surface-treated $\beta$-Ti alloy was evaluated by immersing in simulated body fluid (SBF) solution. The formation of apatite particles was confirmed using Fourier transform-infrared spectroscopy, SEM, and EDAX analyses. Moreover, the electrochemical behavior of surface-modified specimens in SBF solution was evaluated using potentiodynamic polarization and electrochemical impedance spectroscopy. The results revealed that the surface-modified specimens exhibited higher potential value and lower current density when compared to untreated specimen. The EIS studies showed the formation of new layer, indicating the growth of apatite-like particles. More »»


Dr. Karthega M., Nagarajan, S., and Rajendran, N., “In vitro studies of hydrogen peroxide treated titanium for biomedical applications”, Electrochimica Acta, vol. 55, pp. 2201 - 2209, 2010.[Abstract]

Pure titanium substrate was subjected to chemical treatment with different concentrations of hydrogen peroxide and subsequently heat treated to produce a titania gel layer with anatase nature. The surface modified substrates were then immersed in simulated body fluid for the formation of calcium phosphate layer over the surface. Titanium treated with 15 wt.% of hydrogen peroxide produced a uniform porous layer, which was found to induce the calcium phosphate formation more easily. However, titanium treated with 5 wt.% and 25 wt.% of hydrogen peroxide exhibited inhomogeneous surface for the growth of calcium phosphate layer. Further, the corrosion behaviour of the untreated and hydrogen peroxide treated specimens in simulated body fluid was evaluated using potentiodynamic polarization and electrochemical impedance spectroscopy. The results have shown that the surface modified titanium using 15 wt.% of hydrogen peroxide exhibited higher corrosion resistance compared to specimens treated with other concentrations of hydrogen peroxide. More »»


Dr. Karthega M. and Rajendran, N., “Hydrogen peroxide treatment on Ti–6Al–4V alloy: A promising surface modification technique for orthopaedic application”, Applied Surface Science, vol. 256, pp. 2176 - 2183, 2010.[Abstract]

Ti–6Al–4V alloy was treated with various concentrations (5 wt.%, 15 wt.% and 25 wt.%) of hydrogen peroxide (H2O2) and then heat treated to produce an anatase titania layer. The surface modified substrates were immersed in simulated body fluid (SBF) solution for the growth of an apatite layer on the surface and the formed apatite layer was characterized using various surface characterization techniques. The results revealed that titania layer with anatase nature was observed for all \{H2O2\} treated Ti–6Al–4V alloy, irrespective of the \{H2O2\} concentrations. Ti–6Al–4V alloy treated with 15 wt.% and 25 wt.% of \{H2O2\} induced apatite formation, however 5 wt.% of \{H2O2\} treated Ti–6Al–4V failed to form apatite layer on the surface. The electrochemical behaviour of \{H2O2\} treated specimens in \{SBF\} solution was studied using potentiodynamic polarization and electrochemical impedance spectroscopy. Ti–6Al–4V alloy treated with 25 wt.% of \{H2O2\} solution exhibited low current density and high charge transfer resistance values compared to specimens treated with other concentrations of \{H2O2\} and untreated Ti–6Al–4V alloy. More »»


N. Rajendran, Dr. Karthega M., and Tamilselvi, S., “Effect of pH on the corrosion behaviour of Ti-6Al-4V alloy for dental implant application in fluoride media”, Trends Biomater Artif Organs, vol. 20, pp. 31–34, 2007.


S. Nagarajan, Dr. Karthega M., and Rajendran, N., “Pitting corrosion studies of super austenitic stainless steels in natural sea water using dynamic electrochemical impedance spectroscopy”, Journal of Applied Electrochemistry, vol. 37, pp. 195–201, 2007.[Abstract]

Potentiodynamic anodic polarisation and dynamic electrochemical impedance spectroscopic (DEIS) measurements were carried out on type 316L stainless steel (SS), alloys 33 and 24 in natural sea water environment in order to assess pitting corrosion resistance. The results revealed that the pitting corrosion resistance was higher in the case of alloys 33 and 24 than 316L SS; due to the higher contents of nitrogen, chromium and molybdenum. DEIS measurements were performed over a wide range of potentials covering the corrosion potential, passive region, breakdown region and dissolution region. It was shown that the impedance measurements in potentiodynamic conditions allow simultaneous investigation of changes in passive layer structure. The impedance spectra of various potential regions were also discussed. The Nyquist plots were fitted using non-linear least-square (NLSS) method for different potential regions.

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Dr. Karthega M., Raman, V., and Rajendran, N., “Influence of potential on the electrochemical behaviour of β titanium alloys in Hank’s solution”, Acta Biomaterialia, vol. 3, pp. 1019 - 1023, 2007.[Abstract]

The electrochemical behaviour of β titanium alloys, namely Ti–15Mo (TiMo) and Ti–29Nb–13Ta–4.6Zr (TNTZ), were studied under physiological conditions using open circuit potential (OCP), potentiodynamic polarization and electrochemical impedance spectroscopic (EIS) measurements. The \{OCP\} data for \{TNTZ\} alloy indicated a noble behaviour compared to TiMo alloy. The current density value for \{TNTZ\} alloy calculated from polarization measurement was found to be comparable to that of TiMo. The \{EIS\} technique was applied to study the nature of the passive film formed on binary TiMo alloy at various impressed potentials and the results were compared with that of the quaternary \{TNTZ\} alloy. The \{EIS\} spectra obtained for TiMo alloy exhibited a single time constant for all potentials, indicating a highly compact passive layer over the surface. The \{TNTZ\} alloy, however, exhibited a single time constant at lower potentials and two time constants at higher potentials, indicating a bilayer structure at higher potentials. More »»


Dr. Karthega M., Tamilselvi, S., and Rajendran, N., “Effect of pH on the Corrosion Behaviour of Ti-6Al-4V alloy for Dental Implant Application in Fluoride Media”, Trends Biomater Artif Organs, vol. 20, pp. 31–34, 2006.[Abstract]

In the last few decades, titanium and its alloys have been developed in different areas of dentistry. The chemical properties of the oxide layer formed on the surface of titanium play an important role in the biocompatibility of the titanium implants and surrounding tissues. Generally, fluoride containing preparations have high fluoride concentration and pH range between 7.2 and 3.2. Since, fluorides are inimical to all reactive metals such as titanium especially in acidic medium, leads to corrosion due to the destruction of their passivity and loss of mechanical properties. The presence of fluoride ions in the electrolytic environments brings with it aggressiveness in the attack on titanium. This is due to the formation of complex titanium fluoride molecule, which is very stable and soluble in the electrolytic solution. Hence, the aim of the present work is to study the effect of pH 3.5, 5.0 and 7.0 on Ti-6Al-4V in artificial saliva solution containing 1% NaF (sodium fluoride). Electrochemical studies such as open-circuit potential (OCP) measurements, Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) were carried out in artificial saliva medium. More »»
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