Experimental Condensed Matter Physics

• In the past decade nanostructured material technology has rapidly grown and has been and is the focus of intense research, both fundamental and applied. This emphasis stems from potential application of nanostructured materials in diverse fields of tribology, enhanced oil recovery, liquids and gases separation, semiconductors, environmental technology, optical switches, optical storage devices, and glass lens technology. However, notwithstanding the rapid advances in nanotechnology, what role large surface-to-volume ratios have in modifying the material's physical and chemical properties is still evolving.

      SEM Microphotograph of a Porous Silica        Effect of Pore Size on the Freezing
         Sample. Pore Size = 125 nm.                     Transition  of a Physically-Confined Fluid in                                                                                                  Porous Silica

One of the approaches being followed in my laboratory is to fabricate porous silica materials using sol gel technique. These materials have well defined pore sizes. We use materials ranging in size from 2 to 130 nanometer (nm). Various materials are grown and physically confined within these pores, thus, limiting the surface-to-volume ratio of the physically-restricted material. Currently we are confining liquid crystals, various dyes, single crystals, and different types of fluids. These materials are then subjected to specific heat capacity, vibrational spectroscopy, and dynamic mechanical analysis (DMA) measurements. Also by chemically altering the chemical surface structure of porous silica materials, we have and are attempting to modify the electrical, magnetic, and optical properties of nanostructred materials physically confined in the porous silica.

Publication:

• R. Mu and V. M. Malhotra: "Effects of Confinement of the Solid-Liquid Phase Transitions of Cyclohexane and water in Porous KI and KBr Disks: A Vibrational Approach" in 'Dynamics in Small Confining Systems' ed. J. M. Drake, J. Klafter, and R. Kopelman (Material Research Society, Pittsburgh, USA, 1990), pp 47 - 50.

• R. Mu and V. M. Malhotra: Effects of Surface and Physical Confinement on the Phase Transitions of Cyclohexane in Porous Media, Physical Review. 44, 4296- 4303 (1991).

• R. Mu and V. M. Malhotra: Geometrically Restricted Ultrathin Film of Cyclohexane: A metastable phase, Physical     Review B (Rapid Communications) 46, 532-535 (1992).

• V. M. Malhotra, R. Mu,and A. Natarajan "Effects of Surfaces on the Melting/Freezing Behavior of Fluids in Derivatized-  and Nude-Porous Silica", Materials Research Society Symposium, 290, 120 - 126 (1993).

• P. M. Hoffmann and V. M. Malhotra, "Freezing/Melting Transition of Physically Restricted n-Decane," Materials      Research Society Symposium, Volume 366, 295-300 (1995).

• S. Amanuel and V. M. Malhotra "Comparative Thermodynamic Behavior of Physically Restricted Cyclohexane and     Cyclohexanone in Porous Silica", MRS Symposium Series, Vol. 543, 45-50 (1999)

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