Pranesh Sengupta - Academia.edu (original) (raw)

Papers by Pranesh Sengupta

Journal of Non-Crystalline Solids, 2017

Viscosity and diffusivity of silicate melts and glasses are related to each other through relaxat... more Viscosity and diffusivity of silicate melts and glasses are related to each other through relaxation timescales. The systematic is explored based on published data. Diffusion coefficients for Sr and Ba were measured in calcium aluminosilicate glasses at conditions near the glass/supercooled liquid boundary in temperaturetime space making use of thin film technology and Rutherford Backscattering Spectroscopy (RBS) to measure concentration profiles on nanoscales. These data extend the range of published diffusion coefficients and combined with the systematic noted above allow the nature of change of diffusion coefficients across the glass transition region to be studied. Activation energies for diffusion in the glassy state (~360 kJ/mol) are higher than in the molten liquid (~213 kJ/mol). A defect based model of glass transition derived by Ojovan and coworkers, where attainment of a percolation threshold of configuron-type defects accounts for the glassliquid transition, can explain the observed diffusion behaviour. Data treatment using this model yields a defect formation enthalpy of~146 kJ/mol and a migration enthalpy of~213 kJ/mol. The results of this study provide generalized expressions for the prediction of diffusion coefficients of cations in silicate melts for any composition at any temperature.

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2017

Halites are one of the interesting material due to its color variations. Natural halites whose co... more Halites are one of the interesting material due to its color variations. Natural halites whose color ranges from transparent to dark blue were studied by UV-VIS and Raman spectroscopy. The halite crystals were irradiated with 3 MeV proton micro-beam ($20 lm beam width with 80PAbeamcurrent)for10and90mintostudytheradiationdamage.After10minsofirradiation,smallspotdevelopedonthesurfaceoftransparenthalitecrystalwhereasafter90minsofirradiationthespotspreadinsidethebulkleadingtoabrowncoloration(20mminitialsizeto80 PA beam current) for 10 and 90 min to study the radiation damage. After 10 mins of irradiation, small spot developed on the surface of transparent halite crystal whereas after 90 mins of irradiation the spot spread inside the bulk leading to a brown coloration (20 mm initial size to 80PAbeamcurrent)for10and90mintostudytheradiationdamage.After10minsofirradiation,smallspotdevelopedonthesurfaceoftransparenthalitecrystalwhereasafter90minsofirradiationthespotspreadinsidethebulkleadingtoabrowncoloration(20mminitialsizeto2.0 mm final size). The irradiated portion and the un-irradiated portion of the halites was characterized by Raman spectroscopic technique. The variation in the population density was observed from the UV-Vis spectra. The change in the Raman band intensities was observed for transparent, blue colored and proton beam irradiation halites. Such variation of spectroscopic characteristics due to proton irradiation suggests that the halite can be used for the radiation monitoring.

Mineralogical Magazine, 2016

Stalagmites and stalactites, as observed within natural caves, may develop inside geological repo... more Stalagmites and stalactites, as observed within natural caves, may develop inside geological repositories during constructional and post-operational periods. It is therefore important to understand actinide sorption within such materials. Towards this, experimental studies were carried out with 233U, 238Np (VI), 238Np (IV), 239Pu and 241Am radiotracers using natural speleothem samples collected from the Dharamjali cave of the Kumaon Lesser Himalayas, India. Petrological/mineralogical studies showed that natural speleothems have three general domains: (1) columnar calcite; (2) microcrystalline calcite; and (3) botryoidal aragonite – each with ferruginous materials. Results showed that all domains of speleothems can take up >99% actinides, irrespective of valence state and pH (1–6 range) of the solution. However, distribution coefficients were found to be at a maximum in aragonite for most of the actinides. Such data are very important for long-term performance and safety assessmen...

Journal of the American Ceramic Society, 2008

Journal of Nuclear Materials, 2014

Superalloy 693, is a newly identified 'high-temperature corrosion resistant alloy'. Present study... more Superalloy 693, is a newly identified 'high-temperature corrosion resistant alloy'. Present study focuses on microstructure and mechanical properties of the alloy prepared by double 'vacuum melting' route. In general, the alloy contains ordered Ni 3 Al precipitates distributed within austenitic matrix. M 6 C primary carbide, M 23 C 6 type secondary carbide and NbC particles are also found to be present. Heat treatment of the alloy at 1373 K for 30 min followed by water quenching (WQ) brings about a microstructure that is free from secondary carbides and Ni 3 Al type precipitates but contains primary carbides. Tensile property of Alloy 693 materials was measured with as received and solution annealed (1323 K, 60 min, WQ) and (1373 K, 30 min, WQ) conditions. Yield strength, ultimate tensile strength (UTS) and hardness of the alloy are found to drop with annealing. It is noted that in annealed condition, considerable cold working of the alloy can be performed.

Transactions of the Indian Institute of Metals, 2022

A b s t r a c t High level radioactive Liquid Waste (HLW), generated during reprocessing of spent... more A b s t r a c t High level radioactive Liquid Waste (HLW), generated during reprocessing of spent fuel, contains most of the radioactivity present in the entire nuclear fuel cycle. The composition of HLW is site-specific and largely depends on off-reactor cooling of spent nuclear fuel, its type and burn up, and chemistry of reprocessing flow sheet. Development of matrices for conditioning of HLW, to ensure isolation of radioactivity from human environment, for extended period of time, is a scientific and technological challenge. Sodium borosilicate glass formulations, adopted worldwide for immobilization of waste, is not suitable for sulphate bearing HLW, because of its low solubility in such glass. Various compositions based on different glass formulations were made with simulated waste to examine compatibility with waste oxide and containing around 10% sulphate. Vitrified waste product obtained from barium borosilicate glass matrix, were extensively evaluated for its characteristi...

Progress in Nuclear Energy

Journal of Luminescence

Abstract Natural halite displays wide range of colors which is considered as mineralogical rarity... more Abstract Natural halite displays wide range of colors which is considered as mineralogical rarity. Such variation suggests that the said cubic crystal structure can harbor a great variety of lattice defects as color centers. Raman spectroscopy is the powerful tool for investigation of mineralogical phases as well as very sensitive to the defects formed in crystal structure. Amongst various types of color centers (F, R1, R2, M – centers and Plasmons) found in natural colored halite samples, F-centers in present colored halite samples have been confirmed using Photoluminescence (PL) analysis. Detail Spectroscopic studies using Micro-Raman spectroscopy and Photoluminescence (PL) indicate that the blue coloration of the studied halite crystals is due to stoichiometric excess of metallic sodium (Na-colloids) in crystal lattices.

Materials Science and Engineering: C

Nanomaterial based paints are in current demand in the area of surface protective coatings due to... more Nanomaterial based paints are in current demand in the area of surface protective coatings due to the significant advances made to improve their antibacterial and anticorrosion characteristics. In this work, we have developed magnetic graphene oxide (MGO) paint with the incorporation of cobalt ferrite (CF) and graphene oxide (GO) along with paint materials by using high energy ball milling (HEBM). Morphological, elemental and functional analysis of the MGO paint is studied with ESEM, AFM, Raman, FTIR spectroscopy. EDS and PIXE methods are used for elemental analysis. Thermal analysis shows that the MGO film was stable up to 100 °C. The saturation magnetization of CF MNP is observed as 76 emu/g and it is reduced to 12 emu/g for MGP paint. The detailed antibacterial study of the prepared MGO paint has performed with S. typhimurium and E. coli. The dead-live assessment shows the dead population for S. typhimurium is superior up to 82% whereas it is 20% for E. coli. The morphological damage of bacterial cells is studied using SEM technique. Flow cytometry analysis of reactive oxygen species (ROS) generation experiments and computational analysis supported the proposed mechanism of induced ROS for the damage of bacterial membrane via interaction of GO and CF with bacterial proteins leading to alteration in their functionality. The observed results indicate that the prepared MGO paint could be a better candidate in the area of nano paint for surface protective coatings.

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Journal of Nuclear Materials

Degradation of the building stones are creating instability in the old building and monuments whi... more Degradation of the building stones are creating instability in the old building and monuments which is to be protected. To investigate the characteristics of such a stones used for the construction in eastern India, we have collected the khondalite stones. The microstructural and elemental composition analysis of the khondalite stones are analyzed by using SEM, EDX and PIXE trace elemental analysis. We have prepared surface protection coating material with graphene oxide and cobalt ferrite as a base material along with other residuals. The prepared coating materials is coated on the galvanized iron substrate for further characterization. The surface morphology characteristics of the coating material is analyzed by SEM and AFM. The corrosion resistance characteristics of the prepared coating material is studied by the electrochemical impedance spectroscopy. The results suggests that the prepared coating material can be used as a surface protection materials to control the self-destruction of khondalite stones.

Materials Today: Proceedings

Abstract The changes occurring in Ni based austenitic Alloy 693 on interaction with alkali borosi... more Abstract The changes occurring in Ni based austenitic Alloy 693 on interaction with alkali borosilicate glass at 1273 K for different time periods was studied. Formation of α- Al 2 O 3 and Cr 2 O 3 scales/layer at the interface were studied in detail using electron probe microanalyser (EPMA) and Raman spectroscopy. This interfacial α- Al 2 O 3 layer grows in width with increase in the interaction time and acts as a barrier to the transport of Ni, Cr and Fe across the interface at high temperatures preventing the formation of detrimental needle shaped phases like Ni 2 CrO 4 phase and cube-shaped NiCr 2 O 4 phase at the interface.

Journal of Radioanalytical and Nuclear Chemistry

Understanding the mobility of radiocesium and radiostrontium within geological environment is imp... more Understanding the mobility of radiocesium and radiostrontium within geological environment is important from ‘deep geological repository system’—safety assessment point of view. Cs and Sr radionuclide sorption studies have been carried out with a stalagmite sample collected from Lesser—Himalayas. Detailed microstructural studies, backed up by micro-Raman and LIBS analyses, identified three different domains within the sample; constituted of microcrystalline calcite, botryoidal aragonite and palisadic calcite respectively. Experimental studies showed that both the radionuclides exhibit moderate to low sorption coefficients within all the different domains of stalagmite under acidic environment.

Journal of Nuclear Materials, 2016

Abstract Cermet is a new fuel concept for the fast reactor system and is ideally designed to comb... more Abstract Cermet is a new fuel concept for the fast reactor system and is ideally designed to combine beneficial properties of both ceramic and metal. In order to understand fuel clad chemical compatibility, diffusion couples were prepared with U-UO 2 cermet fuel and T91 cladding material. These diffusion couples were annealed at 923–1073 K for 1000 h and 1223 K for 50 h, subsequently their microstructures were examined using scanning electron microscope (SEM), X-ray energy dispersive spectroscope (EDS) and electron probe microanalyser (EPMA). It was observed that the interaction between the fuel and constituents of T91 clad was limited to a very small region up to the temperature 993 K and discrete U 6 (Fe,Cr) and U(Fe,Cr) 2 intermetallic phases developed. Eutectic microstructure was observed in the reaction zone at 1223 K. The activation energy for reaction at the fuel clad interface was determined.

AIP Conference Proceedings, 2016

V2O5 doped sodium barium borosilicate glasses were characterized by photoluminescence spectroscop... more V2O5 doped sodium barium borosilicate glasses were characterized by photoluminescence spectroscopy and electron probe microanalyzer (EPMA). The glass remains homogeneous for lower concentration of V2O5 but a phase separation is observed when V2O5 doping is increased beyond 5 mol%. Detailed microanalysis reveals that the phase separated glass consists of a phase containing V, Ba and Si and a separate Si rich phase within the glass matrix. The luminescence study demonstrated that at low concentration the vanadium mainly interacts with the structural units of B/Si while at higher concentrations, V-O-V/ V-O− Na+/Ba2+ linkages are formed.

Journal of Nuclear Materials, 2015

Abstract We have determined the thermo-physical (elastic modulus, specific heat, thermal expansio... more Abstract We have determined the thermo-physical (elastic modulus, specific heat, thermal expansion and thermal conductivity) and transport (ionic conductivity) properties of ThO 2 -5wt.%CeO 2 mixed oxide (MOX) using a combined experimental and theoretical methodology. The specific heat, ionic conductivity and elastic properties of ThO 2 -5wt.%CeO 2 pellets prepared by conventional powder metallurgy (POP) and coated agglomerate pelletization (CAP) routes (sintered in both air and Ar-8%H 2 atmosphere) are compared with respect to homogeneity (CeO 2 distribution in ThO 2 matrix), microstructure, porosity and oxygen to metal ratio. The effects of inhomogeneity and pore distribution on thermal expansion and thermal conductivity of the mixed-oxide pellets are identified. Molecular dynamics (MD) simulations using the Coulomb-Buckingham-Morse-many-body model based interatomic potentials are used to predict elastic properties in the temperature range between 300 and 2000 K and thermodynamic properties, viz. , enthalpy increment and specific heats of ThO 2 . Finally, the thermal expansion coefficient and thermal conductivity of ThO 2 and (Th,Ce)O 2 mixed-oxides obtained from MD are compared with available experimental results.

Journal of Radioanalytical and Nuclear Chemistry, 2015

Abstract106Ru, 144Ce and 152+154Eu radiotracers sorption experiments (pH: 1–6) have been carried ... more Abstract106Ru, 144Ce and 152+154Eu radiotracers sorption experiments (pH: 1–6) have been carried out with polycrystalline columnar/microcrystalline calcite and aragonite obtained from a stalagmite of Dharamjali cave, India. The different domains of the sample were powdered and thoroughly studied using electron microscopic and X-ray spectroscopic techniques. Both 106Ru and 144Ce exhibited higher sorption within calcite varieties compared to aragonite and increased with rising pH, while it showed reverse relation in case of 152+154Eu. Further, it is noted that aragonite offers the highest Kd values for 152+154Eu, whereas 106Ru and 144Ce prefer calcite.