I am interested in both fundamental as well as applied research in different areas of materials science and metallurgy.

My current interests can be broadly classified into the following areas:

 

High Pressure Materials Science

Complex Hydrides: I am interested in the pressure-induced phase transformations in alkali metal (Li, Na, Mg) based complex hydrides . These experiments provide a unique perspective into the bonding changes that may be helpful in interpreting the hydrogen desorption/absorption behavior of these materials after mechanochemical milling (which is a dynamic high pressure solid state process).

I use high pressure in-situ Raman spectroscopy and synchrotron x-ray diffraction studies in Diamond Anvil Cell (DAC) for these experiments.

 

Polyalcohols & Polyamines: I also study pressure induced transformations and amorphization in organic “plastic crystal” TES materials. I have conducted detailed room temperature high pressure studies (part of my dissertation research) on Pentaerythritol and Neopentylglycol.

 

Vapor Pressure Measurement and Data Assessment

Torsion Effusion Gravimetric Apparatus: I was part of a team involved in the fabrication of a new vapor pressure measurement apparatus. The vapor pressure is measured by measuring the torsion of a double barrel orifice Knudsen cell (Pt-Rh and Molybdenum) and disproportionation reactions in the vapor phase can be determined by the weight loss using a microbalance. The instrumented has been calibrated with KCl and the vapor pressure of Li₃N has been measured.

Assessment of Vapor Pressure Data: The vapor pressure data from different sources have to be evaluated for systematic and random errors. Such an assessment is invaluable for evaluating the quality of vapor pressure data and the data from the above instrument will also be subject to such an analysis.

 

Phase Diagram Calculations

The phase diagram calculations was a main part my Ph.D. dissertation research. I used Thermo-Calc^TM to perform thermodynamic optimization of several binary systems of organic “plastic crystal” thermal energy storage (TES) materials.

 

Thermal Analysis

Differential Scanning Calorimetry (DSC): I have conducted traditional and temperature modulated DSC experiments to obtain thermodynamic data such as heat capacity of pure as well as binary organic “plastic crystal” TES materials.

 

Thermogravimetric Analysis (TGA): I have performed detailed isothermal and nonisothermal oxidation kinetic analysis to obtain kinetic parameters to evaluate the various steels.

 

Interdiffusion Experiments

I am conducting experiments on Steel-Depleted U-Fe diffusion bicouple to obtain interdiffusion coefficients and obtain the kinetics of the layer growth of intermetallics.

RESEARCH INTERESTS

Raja S. Chellappa, Ph.D.