Research Overview

Current research in my group is focussed on exploring the cooperative phenomena in phase transitions. When cooperativity is established, atoms or molecules in the whole system act concertedly such that the system, it its entirety, is driven in a specific direction leading to a transition. Many of the phase transitions remain poorly understood due to lack of recognition of the underlying cooperative phenomena. Recently we have shown that ordering transition in Ni₃Fe alloy is caused by cooperative freezing of the L12 ordered domains at the critical temperature and the resulting propagation of the domains upon further cooling. A practical manifestation of this cooperative freezing is the critical slowing down, i.e., a significant increase in equilibration time (to 40 days or more) during annealing of Ni₃Fe alloy as the critical temperature (500 ℃) is approached. Another important class of transitions are those responsible for formation of tetrahedral amorphous materials. We found that cooperative relaxation of the tetrahedral network transforms supercooled water into stacking disordered ice, also known as low density amorphous (or LDA) ice. A similar transition is also found in supercooled silicon that leads to formation of amorphous silicon which is commonly used in solar cells. A related research activity in my group is the investigation of structural changes in tetrahedral materials based on ring based mesostructures. We have proposed and implemented a method to identify the rings with specific shapes using puckering method which was originally developed (about five decades ago) to analyse organic ring compounds. With this method, we have been able to identify the boat and chair shaped six-membered rings. Such rings form the basis of mesostructures that are commonly found in tetrahedral materials. Using this approach, we have introduced a new method to identify hexagonal crystalline particles in amorphous materials. We have also explored ring based defect structures such as pentagonal nanochannels which, potentially, have a profound influence on the bulk properties of amorphous ice. Apart from these theoretical and computational approaches, we have also recently started experimental work to understand ionic equilibria in problems of practical interest. In particular, we are working on CO₂ absorption in aqueous potassium carbonate and amine solutions with small amounts of added promoters. Such absorption processes are commonly employed in fertilizer industry. Our aim is to understand the ionic equilibria responsible for enhancement of absorption rates due to added promoters such as glycine. In collaboration with the heterogeneous catalysis group (Prof. Goutam Deo), we are also exploring the use of Alumina supported Ni₃Fe as a catalyst for CO₂ methanation reaction.

Awards

• Gold Medal, B. Tech., Nagpur University (1998).
• Outstanding graduate student award for academic achievement, OSU Department of Chemical Engineering (2005).