Susanta K Saha | Siliguri Institute Of Technology (original) (raw)

Papers by Susanta K Saha

Journal of Materials Science Letters

J Mater Sci Lett, 1997

Magnesium aluminate spinel is a refractory oxide material with good mechanical strength and optic... more Magnesium aluminate spinel is a refractory oxide material with good mechanical strength and optical properties. It is highly applicable in metallurgical, electrochemical, radiotechnical and chemical indus-tries. In recent years, a variety of techniques [1–4] have been used to ...

Materials Research Bulletin, 2000

An innovative colloid-gel process using inorganic salts as starting materials has been successful... more An innovative colloid-gel process using inorganic salts as starting materials has been successfully developed for preparing ferroelectric strontium bismuth tantalate (SrBi 2 Ta 2 O 9) powder. This new technique began with the preparation of a mixture of Ta(OH) 5 colloid with the aqueous solutions of strontium and bismuth cations, followed by the addition of ethylene glycol and citric acid as gel-forming reagents. During the calcination process the fluorite phase was formed as an intermediate that was subsequently converted into the SrBi 2 Ta 2 O 9 phase. After calcination at 750°C, pure ultrafine SrBi 2 Ta 2 O 9 polycrystalline powder with a narrow particle size distribution was obtained. The primary particle size of the obtained SrBi 2 Ta 2 O 9 powder was around 40 nm. In comparison with the solid-state reaction, the newly developed colloid-gel process significantly reduces the heating temperature for synthesizing SrBi 2 Ta 2 O 9 , as well as the particle size of the obtained powder.

Talanta, 2007

Iron isotope fractionation between liquid and vapor iron pentacarbonyl was measured in a closed s... more Iron isotope fractionation between liquid and vapor iron pentacarbonyl was measured in a closed system at ∼0 and ∼21 • C to determine if Fe isotope analysis of iron pentacarbonyl vapor is viable using electron-impact, gas-source mass spectrometry. At the 2σ level, there is no significant Fe isotope fractionation between vapor and liquid under conditions thought to reflect equilibrium. Experiments at ∼0 • C indicate iron pentacarbonyl vapor is ∼0.05 per mil (‰) greater in 56 Fe/ 54 Fe than liquid iron pentacarbonyl, which is just resolvable at the 1σ 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.

Materials Science and Engineering: B, 2001

J Mater Sci Lett, 1995

Research in the field of fine grain ceramic mixed oxide systems has gained immense importance bec... more Research in the field of fine grain ceramic mixed oxide systems has gained immense importance because of their potential application in many areas to technology [1-4]. The conventional ceramic method for the preparation of mixed oxide systems involves high temperatures and thus sinters the final product, resulting in the loss of the fine particle nature. In recent years, a variety of non-conventional techniques [5-11] have been used to prepare fine particle systems. These include spray-drying, freezedrying, coprecipitation, sol-gel and hydrothermal oxidation/decomposition processes. In this letter we report a simple, cost effective and versatile route for the preparation of any desired mixed oxide system at fairly low temperature. The process involves thermal dehydration of the homogeneous aqueous solution of metal nitrates and polyvinyl alcohol (PVA). Pyrolysis of this organic based homogeneous mixture (which may be termed the "precursor") results in the desired oxide system. The present study deals with the preparation of a variety of mixed oxide systems, such as spinels [MFe204 where M = Ni(II), Co(II), Zn(II), Mg(II)], orthoferrites [MFeO3 where M = Gd(III), Sm(III)], LaA103, NdGaO3, CaO/MgO/Y203 stabilized zirconia (ZrO2), lead zirconate titanate (PZT), lanthanum modified lead zirconate titanate (PLZT) and BaTiO3. To prepare these oxide systems appropriate amounts of the desired metal nitrates were placed in aqueous solution, then 10% (w/v) aqueous solution of PVA (molecular weight 1,25,000) was added to each of the mixed metal nitrate solutions so as to maintain a metal ion to vinyl alcohol monomer unit mole ratio of 1:2. The PVA helps the homogeneous distribution of the metal ions in its polymeric network structure and inhibits their segregation/ precipitation from the solution. The resulting viscous mixture of PVA metal nitrates was placed over a hot plate (maintained at between 130 and 150 °C) and constantly stirred. When the volume of the solution of mixed metal nitrates and PVA is reduced by evaporation, the nitrate ions provide an in situ oxidizing environment for the decomposition of the PVA. When complete dehydration occurs the nitrates themselves are decomposed with the evolution of brown fumes of nitrogen dioxide, leaving behind a voluminous organic based fluffy black powder (i.e. the precursor powder). These precursor powders are then ground. Pyrolysis of these ground powders at various temperatures gives rise to the desired mixed oxide phase. The choice of heat treatment temperature for the 0261-8028 (~)1995 Chapman & Hall

Polymer Degradation and Stability, Dec 1, 2006

Poly(vinyl chloride)/layered double hydroxide (LDH) composite was prepared by mixing 4 wt% Zn 2 A... more Poly(vinyl chloride)/layered double hydroxide (LDH) composite was prepared by mixing 4 wt% Zn 2 AleCO 3 eLDH with PVC and fluxing at 180 C. The thermal decomposition behaviour of the LDH þ PVC composite in air and nitrogen environments was systematically investigated. We found that mixing Zn 2 AleCO 3 eLDH into PVC facilitates dehydrochlorination from ca. 300 to 270 C but reduces the reaction extent to leave more chlorine on the polyene backbones both in air and N 2. We have also found that at 400e550 C, both in air and N 2 , LDH assists the formation of char-like materials and decreases the release of volatile hydrocarbons. From 550 to 800 C, the char-like materials are mostly retained in N 2 while they are almost completely thermo-oxidized (burned) in air. Thus, addition of Zn 2 AleCO 3 eLDH to PVC does not increase the thermal stability, but does promote charring to retard the generation of flame. The influence of LDH on PVC thermal properties has been also addressed mechanically.

British Ceramic Transactions

Journal of Chemical Sciences, 1994

Journal of the American Ceramic Society, 2003

The present research describes synthesis of hydroxyapatite (HAp) nanopowders using a sol-gel rout... more 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 m 2 /g.

Journal of Non-Crystalline Solids, 1993

ABSTRACT Gels of composition χZrO2−(100−χ)SiO2, with χ=10, 30 and 50 mol%, are prepared at variou... more ABSTRACT Gels of composition χZrO2−(100−χ)SiO2, with χ=10, 30 and 50 mol%, are prepared at various conditions using formate and tetraethoxysilane as precursors. The reactions medium is an aqueous solution of formic acid instead of conventionally applied alcohol. The effect of temperature and the mole ratio of water and tetraethoxysilane on gelation time are studied. Gels are heat treated at 100, 600, 900 and 1100°C. Physical features of ZrO2 particles and of the gel matrix are investigated by X-ray powder diffraction and infrared spectroscopy after each step of the heat treatment.

Journal of sol-gel science and technology, 2001

Lithium manganese oxide (LiMn 2 O 4) powder with spinel structure has been synthesized by a sol-g... more Lithium manganese oxide (LiMn 2 O 4) 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 LiMn 2 O 4 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-Mn 2 O 3 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 180 • C and organic-free LiMn 2 O 4 powder is obtained at as low as 400 • C. Nanosized LiMn 2 O 4 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 Materials Science, 1995

Pure cordierite and cordierite-zirconia (5 and 15 mol.%) are prepared by an aqueous sol-gel techn... more Pure cordierite and cordierite-zirconia (5 and 15 mol.%) are prepared by an aqueous sol-gel technique starting from aqueous solutions of magnesium formate, aluminium formate, zirconium formate and tetraethoxysilane. The gels are dried and calcined at different temperatures ranging from 600 to 1300°C. The dried gels and calcined powders are characterized by thermogravimetric analysis, differential thermal analysis, X-ray powder diffraction and infrared spectroscopic analysis.

Journal of Materials Science, 1994

Gels with the composition of mullite (3Al2O3-2SiO2) were prepared from an aqueous solution of alu... more Gels with the composition of mullite (3Al2O3-2SiO2) were prepared from an aqueous solution of aluminium oxalate and tetraethoxysilane. High-purity stoichiometric mullite powders were produced by calcination of the gel powders with a small exothermic event at 1250 °C. The chemical and structural evolutions were characterized as a function of heat treatment by differential thermal analysis (DTA), thermogravimetric analysis (TGA), X-ray powder diffraction (XRD) and infrared (i.r.) spectroscopy. The composition of mullite varied with the temperature of the heat treatment.

Journal of The American Ceramic Society, 2004

A novel colloid-emulsion process has been used to synthesize nanosized strontium bismuth tantalat... more 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 Materials Science Letters, 1997

Abstracts are not published in this journal

Materials Science and Engineering: C, 2009

Hydroxyapatite (HA) nanopowder was synthesized by reverse microemulsion technique using calcium n... more Hydroxyapatite (HA) nanopowder was synthesized by reverse microemulsion technique using calcium nitrate and phosphoric acid as starting materials in aqueous phase. Cyclohexane, hexane, and isooctane were used as organic solvents, and Dioctyl sulfosuccinate sodium salt (AOT), dodecyl phosphate (DP), NP5 (poly (oxyethylene) 5 nonylphenol ether), and NP12 (poly(oxyethylene) 12 nonylphenol ether) as surfactants to make the emulsion. Effect of synthesis parameters, such as type of surfactant, aqueous to organic ratio (A/O), pH and temperature on powder characteristics were studied. It was found that the surfactant templates played a significant role in regulating the morphology of the nanoparticle. Hydroxyapatite nanoparticle of different morphologies such as spherical, needle shape or rod-like were obtained by adjusting the conditions of the emulsion system. Synthesized powder was characterized using X-ray diffraction (XRD), BET surface area and transmission electron microscopy (TEM). Phase pure HA nanopowder with highest surface area of 121 m 2 /g were prepared by this technique using NP5 as a surfactant. Densification studies showed that this nanoparticle can give about 98% of their theoretical density. In vitro bioactivity of the dense HA compacts was confirmed by excellent apatite layer formation after 21 days in SBF solution. Cell material interaction study showed good cell attachment and after 5 days cells were proliferated on HA compacts in OPC1 cell culture medium. The results imply this to be a versatile approach for making hydroxyapatite nanocrystals with controlled morphology and excellent biocompatibility.

Nanostructured Materials, 1997

Journal of Materials Science Letters

J Mater Sci Lett, 1997

Magnesium aluminate spinel is a refractory oxide material with good mechanical strength and optic... more Magnesium aluminate spinel is a refractory oxide material with good mechanical strength and optical properties. It is highly applicable in metallurgical, electrochemical, radiotechnical and chemical indus-tries. In recent years, a variety of techniques [1–4] have been used to ...

Materials Research Bulletin, 2000

An innovative colloid-gel process using inorganic salts as starting materials has been successful... more An innovative colloid-gel process using inorganic salts as starting materials has been successfully developed for preparing ferroelectric strontium bismuth tantalate (SrBi 2 Ta 2 O 9) powder. This new technique began with the preparation of a mixture of Ta(OH) 5 colloid with the aqueous solutions of strontium and bismuth cations, followed by the addition of ethylene glycol and citric acid as gel-forming reagents. During the calcination process the fluorite phase was formed as an intermediate that was subsequently converted into the SrBi 2 Ta 2 O 9 phase. After calcination at 750°C, pure ultrafine SrBi 2 Ta 2 O 9 polycrystalline powder with a narrow particle size distribution was obtained. The primary particle size of the obtained SrBi 2 Ta 2 O 9 powder was around 40 nm. In comparison with the solid-state reaction, the newly developed colloid-gel process significantly reduces the heating temperature for synthesizing SrBi 2 Ta 2 O 9 , as well as the particle size of the obtained powder.

Talanta, 2007

Iron isotope fractionation between liquid and vapor iron pentacarbonyl was measured in a closed s... more Iron isotope fractionation between liquid and vapor iron pentacarbonyl was measured in a closed system at ∼0 and ∼21 • C to determine if Fe isotope analysis of iron pentacarbonyl vapor is viable using electron-impact, gas-source mass spectrometry. At the 2σ level, there is no significant Fe isotope fractionation between vapor and liquid under conditions thought to reflect equilibrium. Experiments at ∼0 • C indicate iron pentacarbonyl vapor is ∼0.05 per mil (‰) greater in 56 Fe/ 54 Fe than liquid iron pentacarbonyl, which is just resolvable at the 1σ 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.

Materials Science and Engineering: B, 2001

J Mater Sci Lett, 1995

Research in the field of fine grain ceramic mixed oxide systems has gained immense importance bec... more Research in the field of fine grain ceramic mixed oxide systems has gained immense importance because of their potential application in many areas to technology [1-4]. The conventional ceramic method for the preparation of mixed oxide systems involves high temperatures and thus sinters the final product, resulting in the loss of the fine particle nature. In recent years, a variety of non-conventional techniques [5-11] have been used to prepare fine particle systems. These include spray-drying, freezedrying, coprecipitation, sol-gel and hydrothermal oxidation/decomposition processes. In this letter we report a simple, cost effective and versatile route for the preparation of any desired mixed oxide system at fairly low temperature. The process involves thermal dehydration of the homogeneous aqueous solution of metal nitrates and polyvinyl alcohol (PVA). Pyrolysis of this organic based homogeneous mixture (which may be termed the "precursor") results in the desired oxide system. The present study deals with the preparation of a variety of mixed oxide systems, such as spinels [MFe204 where M = Ni(II), Co(II), Zn(II), Mg(II)], orthoferrites [MFeO3 where M = Gd(III), Sm(III)], LaA103, NdGaO3, CaO/MgO/Y203 stabilized zirconia (ZrO2), lead zirconate titanate (PZT), lanthanum modified lead zirconate titanate (PLZT) and BaTiO3. To prepare these oxide systems appropriate amounts of the desired metal nitrates were placed in aqueous solution, then 10% (w/v) aqueous solution of PVA (molecular weight 1,25,000) was added to each of the mixed metal nitrate solutions so as to maintain a metal ion to vinyl alcohol monomer unit mole ratio of 1:2. The PVA helps the homogeneous distribution of the metal ions in its polymeric network structure and inhibits their segregation/ precipitation from the solution. The resulting viscous mixture of PVA metal nitrates was placed over a hot plate (maintained at between 130 and 150 °C) and constantly stirred. When the volume of the solution of mixed metal nitrates and PVA is reduced by evaporation, the nitrate ions provide an in situ oxidizing environment for the decomposition of the PVA. When complete dehydration occurs the nitrates themselves are decomposed with the evolution of brown fumes of nitrogen dioxide, leaving behind a voluminous organic based fluffy black powder (i.e. the precursor powder). These precursor powders are then ground. Pyrolysis of these ground powders at various temperatures gives rise to the desired mixed oxide phase. The choice of heat treatment temperature for the 0261-8028 (~)1995 Chapman & Hall

Polymer Degradation and Stability, Dec 1, 2006

Poly(vinyl chloride)/layered double hydroxide (LDH) composite was prepared by mixing 4 wt% Zn 2 A... more Poly(vinyl chloride)/layered double hydroxide (LDH) composite was prepared by mixing 4 wt% Zn 2 AleCO 3 eLDH with PVC and fluxing at 180 C. The thermal decomposition behaviour of the LDH þ PVC composite in air and nitrogen environments was systematically investigated. We found that mixing Zn 2 AleCO 3 eLDH into PVC facilitates dehydrochlorination from ca. 300 to 270 C but reduces the reaction extent to leave more chlorine on the polyene backbones both in air and N 2. We have also found that at 400e550 C, both in air and N 2 , LDH assists the formation of char-like materials and decreases the release of volatile hydrocarbons. From 550 to 800 C, the char-like materials are mostly retained in N 2 while they are almost completely thermo-oxidized (burned) in air. Thus, addition of Zn 2 AleCO 3 eLDH to PVC does not increase the thermal stability, but does promote charring to retard the generation of flame. The influence of LDH on PVC thermal properties has been also addressed mechanically.

British Ceramic Transactions

Journal of Chemical Sciences, 1994

Journal of the American Ceramic Society, 2003

The present research describes synthesis of hydroxyapatite (HAp) nanopowders using a sol-gel rout... more 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 m 2 /g.

Journal of Non-Crystalline Solids, 1993

ABSTRACT Gels of composition χZrO2−(100−χ)SiO2, with χ=10, 30 and 50 mol%, are prepared at variou... more ABSTRACT Gels of composition χZrO2−(100−χ)SiO2, with χ=10, 30 and 50 mol%, are prepared at various conditions using formate and tetraethoxysilane as precursors. The reactions medium is an aqueous solution of formic acid instead of conventionally applied alcohol. The effect of temperature and the mole ratio of water and tetraethoxysilane on gelation time are studied. Gels are heat treated at 100, 600, 900 and 1100°C. Physical features of ZrO2 particles and of the gel matrix are investigated by X-ray powder diffraction and infrared spectroscopy after each step of the heat treatment.

Journal of sol-gel science and technology, 2001

Lithium manganese oxide (LiMn 2 O 4) powder with spinel structure has been synthesized by a sol-g... more Lithium manganese oxide (LiMn 2 O 4) 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 LiMn 2 O 4 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-Mn 2 O 3 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 180 • C and organic-free LiMn 2 O 4 powder is obtained at as low as 400 • C. Nanosized LiMn 2 O 4 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 Materials Science, 1995

Pure cordierite and cordierite-zirconia (5 and 15 mol.%) are prepared by an aqueous sol-gel techn... more Pure cordierite and cordierite-zirconia (5 and 15 mol.%) are prepared by an aqueous sol-gel technique starting from aqueous solutions of magnesium formate, aluminium formate, zirconium formate and tetraethoxysilane. The gels are dried and calcined at different temperatures ranging from 600 to 1300°C. The dried gels and calcined powders are characterized by thermogravimetric analysis, differential thermal analysis, X-ray powder diffraction and infrared spectroscopic analysis.

Journal of Materials Science, 1994

Gels with the composition of mullite (3Al2O3-2SiO2) were prepared from an aqueous solution of alu... more Gels with the composition of mullite (3Al2O3-2SiO2) were prepared from an aqueous solution of aluminium oxalate and tetraethoxysilane. High-purity stoichiometric mullite powders were produced by calcination of the gel powders with a small exothermic event at 1250 °C. The chemical and structural evolutions were characterized as a function of heat treatment by differential thermal analysis (DTA), thermogravimetric analysis (TGA), X-ray powder diffraction (XRD) and infrared (i.r.) spectroscopy. The composition of mullite varied with the temperature of the heat treatment.

Journal of The American Ceramic Society, 2004

A novel colloid-emulsion process has been used to synthesize nanosized strontium bismuth tantalat... more 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 Materials Science Letters, 1997

Abstracts are not published in this journal

Materials Science and Engineering: C, 2009

Hydroxyapatite (HA) nanopowder was synthesized by reverse microemulsion technique using calcium n... more Hydroxyapatite (HA) nanopowder was synthesized by reverse microemulsion technique using calcium nitrate and phosphoric acid as starting materials in aqueous phase. Cyclohexane, hexane, and isooctane were used as organic solvents, and Dioctyl sulfosuccinate sodium salt (AOT), dodecyl phosphate (DP), NP5 (poly (oxyethylene) 5 nonylphenol ether), and NP12 (poly(oxyethylene) 12 nonylphenol ether) as surfactants to make the emulsion. Effect of synthesis parameters, such as type of surfactant, aqueous to organic ratio (A/O), pH and temperature on powder characteristics were studied. It was found that the surfactant templates played a significant role in regulating the morphology of the nanoparticle. Hydroxyapatite nanoparticle of different morphologies such as spherical, needle shape or rod-like were obtained by adjusting the conditions of the emulsion system. Synthesized powder was characterized using X-ray diffraction (XRD), BET surface area and transmission electron microscopy (TEM). Phase pure HA nanopowder with highest surface area of 121 m 2 /g were prepared by this technique using NP5 as a surfactant. Densification studies showed that this nanoparticle can give about 98% of their theoretical density. In vitro bioactivity of the dense HA compacts was confirmed by excellent apatite layer formation after 21 days in SBF solution. Cell material interaction study showed good cell attachment and after 5 days cells were proliferated on HA compacts in OPC1 cell culture medium. The results imply this to be a versatile approach for making hydroxyapatite nanocrystals with controlled morphology and excellent biocompatibility.

Nanostructured Materials, 1997