Research

Research areas

MgB₂Superconductor

In case of Magnesium diboride (MgB₂), is an inter-metallic superconductor with Tc around 40 K. Researchers have reported that synthesis of this superconductor requires high temperature and an oxygen free ambiance, which for poses the limitations on use of this superconductor in various applications. In view of this, I developed a technique to synthesize the MgB₂ at relatively lower temperature, which has flexibility over the shape and dimensions of the sample.

The MgB₂ films were deposited on stainless substrates by electrophoretic deposition and tested for their superconducting properties. Stability of the MgB₂ samples was also studied in argon and air ambiance using Thermogravimetry and differential thermal analysis (TG-DTA).

Along with the films, I was involved in bulk synthesis of MgB₂ using high temperature reaction of Mg and Boron powder in presence of excess Mg and carbon environment.

I was also involved in synthesis and microwave properties of Oxide superconductors. These various kinds of samples were then characterized for their structural, morphological and superconducting properties using techniques like XRD, SEM, TGA-DTA, FTIR and Transport property measurements at low temperature. I have experience of synthesis of superconducting thin films by electrochemical depositions , spray pyrolysis and bulk using Solid state synthesis route.

With electrophoretic deposition technique I developed superconducting wires as well as coils of MgB₂ as coated superconductor.

Nonlinear dynamics of the NEMS

I worked on the suspended metallic nanoelectromechanical system (NEMS). The nonlinear dynamics of a single as well as an array of microbeam resonators was studied. Suspended arrays of the NEMS are interesting in many respect, however we considered them in order to understand the mode coupling, anti-crossing behaviors and for generating squeezed states. Along with this, buckling behavior in NEMS is interesting in experimental as well as theoretical point of view as their applications are increasing as a memory devices. To understand these phenomenons’s, NEMS were fabricated DC magnetron sputtering vacuum evaporation process, photolithography as well as e-beam lithography, electron cyclotron resonance (ECR) plasma etching process. Optomechanical behavior of the fabricated devices was studied by using optical detection setup consists of Bragg grating (FBG) and a microlens attached to the end of a single mode fiber which can be accurately positioned using piezomotors. In general, cavity is formed between suspended NEMS and the FBG. The in-plane and out off plane motion of the array of the beams is actuated using external AC –DC driving across the beams and bottom electrode as of the package gold pad. Recently, we have developed the theoretical model that account for the buckling behaviors of the beams. This theoretical model found to be in agreement with some of the experimental results of buckling behavior of the beams. It is seen that system experimentally exhibits some unusual behaviors. For example, contrary to other experiments, in which self-excited oscillations of the mechanical resonator are optically induced when the cavity is blue detuned, it is seen that same effect occurs for the case of red-detuned cavity.

Quantum measurement and Squeezed states

At milli-Kelvin temperatures, mechanical resonators with high frequencies (in the range of GHz) are expected to exhibit coherent quantum behavior. Thus their sensitive displacement detection is possible when coupled with the SQUID by generating their squeezed states. With this motivation, I have fabricated Nb/Al (AlOx)/Nb junction based DC SQUIDs using only a single photolithography step and a single 3D Focused ion Beam (FIB) etching. During fabrication of these devices I handled FIB intensively and acquired the skills in Josephson junction fabrications and depositing materials like platinum using omni probe.

Chromium Magnetism

Chromium and its alloys exhibit SDW. I studied CrCo alloy thin films deposited by DC magnetron sputtering. The resistivity (ρ) for these samples was determined in the temperature range 2 K < T < 395 K and used to determine the Néel transition temperatures (T_N) for the individual samples. The T_N versus x plot for this sample series shows non-monotonic behavior. The low temperature minima are observed in the resistivity plots. Hall coefficients (R_H) measurements were done for the films. Interestingly, the R_H versus T plots reveled a spin-flip transition at about 123 K for 1.3 at.% Co thin film. These results shed light on the effect of dimensionality on the electrical properties of the Cr-Co alloys.

Also I worked on synthesis of doped Cr alloys by arc melting. I studied thermal expansion (INVAR and Elinvar) behavior of these alloys along with ultrasonic velocity measurements at low temperatures.

Photonic Materials

I have also worked on photonic materials. I used atomic layer deposition (ALD) technique to develop antireflection coatings for solar cells. The deposited samples were analyzed by using spectroscopic ellipsometry to evaluate optical parameters such as refractive index, extinction coefficient. Also Oxidation of GaN and Its optical properties were tested using Spectroscopic ellipsometry.

Solid Oxide Fuel Cells (SOFC)

We worked on the development of cathode, anode and electrolyte materials of for SOFC's. Impedance analysis of the materials was also conducted to understand the electronic and ionic behavior of the materials.

Energy Science

Being specialized in energy science, I voluntarily taught energy science course and energy conversion technologies to the M.Sc. Physics students of Physics Dept. Shivaji University, Kolhapur. The renewable energy conversion technologies include solar energy (photovoltaic and solar thermal), Wind energy, Biomass energy, Ocean energy and Fuel cells etc.

For My MSc project , I worked on synthesis of fuel cell cathode material using electrodeposition technique. I am experienced in handling potentiostat and electrochemical analysis of Cyclic Voltametry and Chronoampherometry . I have used electrodeposition setup to deposit multi-component material with desired stoichiometry. I am skilled in electrochemical impedance measurements and its analysis.

Seismology

Seismological Observatory at Department of Physics Shivaji University Kolhapur is running 24x7 since 2002. In this observatory I have installed Seismometer (Taurus T-240), Accelerometers, V-SAT and Solar Photovoltaic System. This seismometer can sense earthquake events happening all over the globe. I collected and analysed seismic data regularly for 4 years. Our studies were focused to understand the seismic activity of Koyna region. Other earthquake system was utilized to understand the earths magentic field changes during the earthquake .

COURSES TAKEN DURING THE RESEARCH WORK

Research methodologies
Characterization of Materials (Transport property measurements, XRD, SEM, TEM, AFM, DTA, DSC, TGA, AAS, UV-VIS-IR.)
Science and Technology of Thin Films
Superconductor Science and Technology

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