Susanta Saha

Publications (10) View all

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  Available from: Susanta Saha

  Article: Iron isotope fractionation between liquid and vapor phases of iron pentacarbonyl.

  René A Wiesli, Brian L Beard, Paul S Braterman, Clark M Johnson, Susanta K Saha, Mahadeva P Sinha
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  ABSTRACT: Iron isotope fractionation between liquid and vapor iron pentacarbonyl was measured in a closed system at approximately 0 and approximately 21 degrees C to determine if Fe isotope analysis of iron pentacarbonyl vapor is viable using electron-impact, gas-source mass spectrometry. At the 2sigma level, there is no significant Fe isotope fractionation between vapor and liquid under conditions thought to reflect equilibrium. Experiments at approximately 0 degrees C indicate iron pentacarbonyl vapor is approximately 0.05 per mil (per thousand) greater in (56)Fe/(54)Fe than liquid iron pentacarbonyl, which is just resolvable at the 1sigma level. Partial decomposition of iron pentacarbonyl vapor or liquid to an iron oxide or iron metal shows that significant isotopic fractionation occurs, where the decomposed product has a lower (56)Fe/(54)Fe ratio as compared to the starting iron pentacarbonyl. It follows that methods to decompose iron pentacarbonyl must be quantitative to obtain accurate isotope values.
  Talanta 02/2007; 71(1):90-6. · 3.79 Impact Factor
• Article: Colloid Emulsion of Nanosized Strontium Bismuth Tantalate Powder

  Chung-Hsin Lu, Susanta Kumar Saha
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  ABSTRACT: A novel colloid-emulsion process has been used to synthesize nanosized strontium bismuth tantalate (SrBi2Ta2O9) particles. During calcination, the desired bismuth-layered structure phase develops at the expense of the pyrochlore phase. Calcining the precursor powder at 750°C for 2 h leads to the complete formation of single-phase layered-structured SrBi2Ta2O9. The powder that is formed consists of nanoparticles with a narrow size distribution and almost-spherical morphology. The crystallinity of the calcined powder increases as the calcination temperature and heating time increases. The developed colloid-emulsion process significantly reduces the SrBi2Ta2O9 particle size, in comparison to conventional process techniques, and results in a uniform microstructure of the obtained powder.
  Journal of the American Ceramic Society 12/2004; 83(5):1320 - 1322. · 2.27 Impact Factor
• Article: Synthesis of Hydroxyapatite Nanopowders via Sucrose‐Templated Sol–Gel Method

  Susmita Bose, Susanta Kumar Saha
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  ABSTRACT: The present research describes synthesis of hydroxyapatite (HAp) nanopowders using a sol–gel route with calcium nitrate and ammonium hydrogen phosphate as calcium and phosphorous precursors, respectively. Sucrose is used as template material, and alumina is added as a dopant to study its effects on particle size and surface area. Synthesized powders are characterized using X-ray diffractometry, BET surface-area analysis, and transmission electron microscopy. Results show that alumina stabilizes the HAp crystalline phase. Average particle size of mesoporous HAp samples is between 30 and 50 nm with surface area of 51–60 m2/g.
  Journal of the American Ceramic Society 12/2004; 86(6):1055 - 1057. · 2.27 Impact Factor
• Article: Synthesis and Characterization of Hydroxyapatite Nanopowders by Emulsion Technique

  Susmita Bose, Susanta Kumar Saha
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  ABSTRACT: Nanocrystalline HAp powder was synthesized using surfactant template systems. Composition of the microemulsion and synthesis parameters had significant effect on the formation of HAp nanopowder and their surface area and morphology. Powders were prepared with a surface area of 130 m2/g and particle size between 30 and 50 nm with needle shape and spherical morphology. Nanocrystalline hydroxyapatite (HAp) powder was synthesized using the reverse micelle-processing route. Cyclohexane was used as the oil phase, mixed poly(oxyethylene)5 nonylphenol ether (NP-5) and poly(oxyethylene)12 nonylphenol ether (NP-12) as the surfactant phase, and a solution of Ca(NO3)2 and H3PO4 was used as the aqueous phase. The powders were characterized by BET surface area analyzer, powder X-ray diffraction, and transmission electron microscopy. It was found that experimental conditions such as aqueous/organic phase volume ratio, pH, aging time, aging temperature, and metal ion concentration in the aqueous phase affected the crystalline phase, surface area, particle size, and morphology of HAp nanopowders. With the use of this technique, nanopowders were prepared with different morphology depending on the reaction parameters.
  10/2003;
• Article: Low Temperature Synthesis of Nano-Sized Lithium Manganese Oxide Powder by the Sol-Gel Process Using PVA

  Chung-Hsin Lu, Susanta Kumar Saha
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  ABSTRACT: Lithium manganese oxide (LiMn2O4) powder with spinel structure has been synthesized by a sol-gel method using an aqueous solution of metal nitrates containing polyvinyl alcohol (PVA). The role of PVA and the calcination conditions for the formation of LiMn2O4 have been studied. Homogeneity and reactivity of the precursor powder are enhanced with an increase in the amount of PVA in the starting solution. When the amount of PVA is low, an impurity phase-Mn2O3 is formed at low temperature. On the other hand, when the vinyl alcohol monomer unit of PVA to metal ion ratio is 2 : 1 in the starting solution, only spinel phase is formed at 180C and organic-free LiMn2O4 powder is obtained at as low as 400C. Nanosized LiMn2O4 particles with a narrow size distribution have been successfully prepared by this technique. This method with proper amount of PVA results in much lower calcination temperature and shorter calcination time for producing the single spinel phase in comparison with the conventional solid state reaction and other solution techniques.
  Journal of Sol-Gel Science and Technology 12/2000; 20(1):27-34. · 1.63 Impact Factor