Thermoelectric Properties of Fe0.2Co3.8Sb12-xTex ... - Physics
Thermoelectric Properties of Fe0.2Co3.8Sb12-xTex ... - Physics
Thermoelectric Properties of Fe0.2Co3.8Sb12-xTex ... - Physics
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A reversible shear-induced crystallization above equilibrium<br />
freezing temperature in mixed surfactant system<br />
Vikram Rathee 1 , Rema Krishnaswamy 2 , Antara Pal 3 , V. A. Raghunathan 3 , Marianne Imp´eror 4 , Brigitte<br />
Pansu 4 and A.K. Sood 1,2<br />
1 Department <strong>of</strong> <strong>Physics</strong>, Indian Institute <strong>of</strong> Science, Bangalore 560012, India,<br />
2 Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur P.O., Bangalore 560064, India,<br />
3 Raman Research Institute, Bangalore-560080, India, and<br />
4 Laboratoire de Physique des Solides, UMR 8502 CNRS, Bat 510, Universite' Paris-Sud 11, 91405 Orsay<br />
Cedex, France.<br />
Shear driven crystallization is a well studied phenomenon in colloidal suspensions, polymer melts,<br />
surfactant mesophases, molecular liquids and atomic systems. The characteristic feature <strong>of</strong> the<br />
crystallization which occurs below the equilibrium freezing temperature is that the positional ordering<br />
persists even after the shear is stopped. Here we demonstrate a novel shear-induced crystallization<br />
phenomenon in a weakly swollen isotropic (L i ) and lamellar (L α ) mesophases with bilayers formed in a<br />
cationic-anionic mixed surfactant system. Synchrotron rheological x-ray scattering reveals the transitions<br />
to be 1st order and reversible under shear i.e., on stopping the shear, the crystalline phase Lc, reverts<br />
back to the equilibrium mesophase. Rheo-optical observations show a shear-thickening which occurs<br />
along with the preordering <strong>of</strong> L i phase induced by shear flow to L α phase before the nucleation <strong>of</strong> L c<br />
phase. Shear diagram <strong>of</strong> the Li phase constructed in the parameter space <strong>of</strong> shear-rate () vs<br />
temperature (T) exhibits L i L c + L i and L i L α + L i , transitions above the equilibrium crystallization<br />
temperature (T K ), in addition to the irreversible shear-driven nucleation <strong>of</strong> L c in L i phase below T K .<br />
Besides revealing a new class <strong>of</strong> non-equilibrium phase transitions, the present study urges a novel<br />
approach towards understanding shear-induced phenomena in concentrated mesophases <strong>of</strong> mixed<br />
amphiphilic systems.
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