Sujata Tarafdar

Publications (50) View all

• Article: Crack Formation in Laponite Gel under AC Fields

  Tajkera Khatun, Tapati Dutta, Sujata Tarafdar
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  ABSTRACT: Crack formation patterns in laponite gel are known to be strongly affected by DC electric fields. We show that AC fields produce equally remarkable patterns in a radially symmetric set-up. The character of the pattern depends crucially on the field strength. A significant feature observed is the bending of radial cracks, with the curvature increasing as field strength is increased. Fields of 20 to 70 V have been applied and several features of the resulting patterns quantified. Striations on the fracture surfaces and crack speeds are also studied.
  04/2013;
• Article: Multifractal analysis of the pore space of real and simulated sedimentary rocks

  Abhra Giri, Sujata Tarafdar, Philippe Gouze, Tapati Dutta
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  ABSTRACT: It is well known that sedimentary rocks having same porosity can have very different pore size distribution. The pore distribution determines many characteristics of the rock among which, its transport property is often the most useful. Multifractal analysis is a powerful tool that is increasingly used to characterize the pore space. In this study we have done multifractal analysis of pore distribution on sedimentary rocks simulated using the Relaxed Bidisperse Ballistic Model (RBBDM). The RBBDM can generate a $3-D$ structure of sedimentary rocks of variable porosity by tuning the fraction $p$ of particles of two different sizes. We have also done multifractal analysis on two samples of real sedimentary rock to compare with the simulation studies. One sample, an oolitic limestone is of high porosity (40%)while the other is a reefal carbonate of low porosity around 7%. $2-D$ sections of X-ray micro-tomographs of the real rocks were stacked sequentially to reconstruct the real rock specimens. Both samples show a multifractal character, but we show that RBBDM gives a very realistic representation of a typical high porosity sedimentary rock.
  02/2013;
• Article: Morphology and Ion-Conductivity of Gelatin-LiClO(4) Films: Fractional Diffusion Analysis.

  Tania Basu, Minakshi Maitra Goswami, T R Middya, Sujata Tarafdar
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  ABSTRACT: Biopolymers are expected to replace synthetic polymers in the quest for cost-effective, environment friendly, and pollution free technology. We report here a study on gelatin films with different concentrations of lithium perchlorate, which may be a candidate for electrolyte material in solid polymer batteries. Morphology studies and impedance spectroscopy both are done on the same set of samples. We study the microstructure of the film by SEM and try to see if a correlation between impedance spectroscopy results and features of gel morphology can be identified. A network structure is revealed in the SEM images where details of the network parameters appear to depend on the salt fraction. Analysis of the impedance measurements is done using a physically meaningful model based on material properties instead of the usual equivalent circuit formalism, where circuit elements are difficult to interpret. We find that anomalous diffusion of charge carriers plays an important role; this is incorporated through a fractional calculus approach.
  The Journal of Physical Chemistry B 08/2012; 116(36):11362-9. · 3.70 Impact Factor
• Article: Aggregation Patterns of Salt Crystalizing in Drying Colloidal Solvents

  Moutushi Dutta Choudhury, Sayanee Jana, Sruti Dutta, Sujata Tarafdar
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  ABSTRACT: We report a study of the structure of droplets of colloidal gels containing dissolved sodium chloride. The components segregate and form intricate patterns. The salt crystalizes in fractal and multi-fractal dendritic forms which are determined by the material which forms the colloidal gel. Here potato starch, gelatine and carboxymethyl cellulose have been used. The substrate also plays a role in some cases. Photographs and micrographs at different level of magnification are shown.
  08/2012;
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  Article: Computer simulation of viscous fingering in a lifting Hele-Shaw cell with grooved plates

  Sujata Tarafdar, Soma Nag, Tapati Dutta, Suparna Sinha
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  ABSTRACT: We simulate viscous fingering generated by separating two plates with a constant force, in a lifting Hele-Shaw cell. Variation in the patterns for different fluid viscosity and lifting force is studied. Viscous fingering is strongly affected by anisotropy. We report a computer simulation study of fingering patterns, where circular or square grooves are etched on to the lower plate. Results are compared with experiments.
  Pramana 04/2012; 73(4):743-754. · 0.57 Impact Factor