Viswanathan Kumar - Academia.edu (original) (raw)
Papers by Viswanathan Kumar
Physica E: Low-dimensional Systems and Nanostructures, 2008
... Synthesis and nonlinear optical studies of nano ZnO colloids. Bindu Krishnan a , b , Correspo... more ... Synthesis and nonlinear optical studies of nano ZnO colloids. Bindu Krishnan a , b , Corresponding Author Contact Information , E-mail The Corresponding Author , Litty Irimpan a , VPN Nampoor a and V. Kumar c. ... Available online 29 January 2008. Abstract. ...
Integrated Ferroelectrics, 2018
Preferentially {110}-oriented thin films of lead lanthanum zirconate titanate, (Pb, La) (Zr, Ti)O... more Preferentially {110}-oriented thin films of lead lanthanum zirconate titanate, (Pb, La) (Zr, Ti)O 3 [PLZT] having compositions (7/65/35), (7/60/40) and (7/56/44) across the morphotropic phase boundary with a thickness of 1.5mm were prepared on platinised silicon substrates (111) Pt/Ti/SiO 2 /Si by sol-gel spin coating technique. The crystallographic orientation and crystalline phases were analysed by X-ray diffraction and Raman spectroscopy respectively. The dependence of the transverse piezoelectric coefficient, e 31;f of the PLZT thin films on their composition and texture have been investigated. PLZT (7/60/40) thin films having a higher tetragonal content was found to exhibit optimum piezoelectric characteristics. By combining the results obtained from the dielectric and polarisationelectric field (P-E) studies, the domain switching mechanism responsible for e 31;f have been established.
Journal of Materials Science: Materials in Electronics, 2008
Glass–ceramics based on a soft piezoelectric of composition (Pb0.94Sr0.06)(Zr0.53Ti0.47)0.997Mn0.... more Glass–ceramics based on a soft piezoelectric of composition (Pb0.94Sr0.06)(Zr0.53Ti0.47)0.997Mn0.004O3 (PSZTM) have been synthesized using three different glass systems by sol–gel method. The effect of the different glass systems on the crystallization of the perovskite phase, PSZTM have been studied using XRD and DTA. The piezoelectric characteristics of the different glass–ceramic systems have been determined and are correlated with the crystallization behaviour, crystalline phase and microstructure.
Applied Physics A, 2016
Abstract In the present work, we report the aging effect in manganese (Mn) and niobium (Nb) hybri... more Abstract In the present work, we report the aging effect in manganese (Mn) and niobium (Nb) hybrid-doped PZT composition. Interestingly, it is observed that the ferroelectric aging depends on the acceptor/donor ratio. In hybrid-doped PZT, at high donor dopant concentrations, aging is not observed. The underlying mechanism is correlated with the defect chemistry of the system. It is also observed that tuning the defect chemistry is an effective strategy to realize piezoceramics with enhanced dielectric and piezoelectric characteristics.
Ceramics International, 2017
A new family of compounds with two diglycolamide moieties in their molecule have been synthesized... more A new family of compounds with two diglycolamide moieties in their molecule have been synthesized and studied as suitable extractants for trivalent actinides (An(III)) and trivalent lanthanides (Ln(III)) present in high-level wastes (HLW) issued from the PUREX process. Although the obtained distribution ratios are comparable with those from TODGA under similar experimental conditions, the bis-DGA compounds showed higher selectivity towards Ln(III). The number of bis-DGA molecules involved in the formation of the dominant complex is two, and it is possible to recover more than 99% of the extracted An and Ln with 0.01 M nitric acid in order to recycle the solvent in subsequent extraction cycles. (authors)
Journal of Sol-Gel Science and Technology, 2003
... 4. Conclusions Nanocrystalline PZT powders with good composi-tional homogeneity have been pre... more ... 4. Conclusions Nanocrystalline PZT powders with good composi-tional homogeneity have been prepared by the sol-gel method using a novel system. ... Acknowledgment We are grateful to Mr.Lachlan Cranswick, CCP14, School of Crystallography, Birkbeck College, ...
Journal of Physics D: Applied Physics, 2007
... 40 (2007) 78047810 doi:10.1088/0022-3727/40/24/032 Crystallization studies and dielectric pr... more ... 40 (2007) 78047810 doi:10.1088/0022-3727/40/24/032 Crystallization studies and dielectric properties of (Ba0.7Sr0.3)TiO3 in bariumaluminosilicate glass PV Divya, G Vignesh and V Kumar1 ... References [1] Zhai J, Yao X, Cheng X, Zhang L and Haydn C 2002 J. Mater. Sci. ...
![Research paper thumbnail of Tunability of third order nonlinear absorption in (Pb,La)(Zr,Ti)O[sub 3] thin films](https://attachments.academia-assets.com/84167371/thumbnails/1.jpg)
](Applied Physics Letters, 2011
Journal of Materials Science, 2002
Dispersion of PZT powder of average particle size ~75 nm in commonly used solvent systems for tap... more Dispersion of PZT powder of average particle size ~75 nm in commonly used solvent systems for tape casting namely, toluene-ethanol and MEK-ethanol (azeotropic), xylene-ethanol (zeotropic) along with triton x-100, menhaden fish oil and phosphate ester as dispersants has been studied using simple sedimentation experiments. The relative merits of these three solvent systems and dispersants in dispersing PZT powder was analyzed.
Applied Physics Letters, 2006
Nanocrystalline Zn 1−x Mg x O thin films with an average particle diameter of 60 nm have been dep... more Nanocrystalline Zn 1−x Mg x O thin films with an average particle diameter of 60 nm have been deposited on glass substrates using a sol-gel spin-coating technique. Within the range of compositions, 0 ഛ x ഛ 0.20, the optical band gap could be tuned between 3.40 and 3.83 eV. The nonlinear optical transmission in the visible spectral region is investigated using ultrafast ͑100 fs͒ and short ͑7 ns͒ laser pulses at off-resonant wavelengths. The observed nonlinearity is strong and is comparable to that recently obtained in ZnO nanocomposite layers ion-implanted with Cu + ions.
2011 National Postgraduate Conference, 2011
Fluidized beds are in use for decades in various industrial as well as other areas providing bett... more Fluidized beds are in use for decades in various industrial as well as other areas providing better efficiency and more effectiveness for processes involved. Its application has been extended to various industrial and non-industrial processes since its advent. In due course, the change in nature and new requirements of processes have necessitated alteration in the fluidized beds for custom use.
Journal of the American …, 2002
Formation of spinel phases in ZnOSb2O3 and ZnOSb2O3 Bi2O3 systems is studied by the use of X-r... more Formation of spinel phases in ZnOSb2O3 and ZnOSb2O3 Bi2O3 systems is studied by the use of X-ray diffraction. The formation of nonstoichiometric Zn2.33Sb0.67O4 phase is ob-served in both the systems at 900°C. However, in these systems, at higher temperatures (T > ...
Materials Science in Semiconductor Processing, 2016
Abstract Titania nanotube array sensitised with lead sulphide (PbS) were synthesised using a succ... more Abstract Titania nanotube array sensitised with lead sulphide (PbS) were synthesised using a successive ionic layer adsorption and reaction (SILAR) method. The PbS sensitation gives visible light sensitivity to the titania nanotube arrays. The PbS sensitised titania nanotube were characterised using X-ray diffraction, UV–visible spectroscopy and scanning electron microscopy. The stability of the PbS sensitised titania nanotube were monitored through the X-ray photoelectron spectroscopy (XPS). The photocatalytic activity of the titania sensitised with PbS were studied by monitoring the degradation of methylene blue under visible light irradiation. The photocatalytic activity and solar cell efficiency is found to be highly depended on the number of SILAR cycle used for the sensitisation of PbS on titania nanotube. The sample coated for 3 SILAR cycle of PbS shows highest solar cell efficiency and photocatalytic activity under visible light. The photocatalytic activity drastically decreased in the samples after the Ist cycle of photocatalytic reaction. The drastic decrease in the photoactivity is due to the dissolution of PbS nanoparticle on the surface of titania nanotube after the first cycle of photocatalytic reaction. XPS was employed as a tool to probe the dissolution of PbS nanoparticles.
Catalysis Letters, 2015
Titania nanotubes decorated with Pd nanoparticles were synthesised by a hydrothermal method. The ... more Titania nanotubes decorated with Pd nanoparticles were synthesised by a hydrothermal method. The increased amounts of Pd concentration is found to facilitate the anatase to rutile crystalline phase transformation as well as in collapse of the morphology as revealed by X-ray diffraction, Raman spectroscopy, scanning and transmission electron microscopy. The presence of metallic as well as the oxidized form (PdO2) of surface metal ions was characterized by using XPS. The catalytic activity of the Pd loaded titania nanotubes has been demonstrated by studying the reduction of p-nitrophenol to p-aminophenol. The 1.0 mol% Pd loaded titania nanotubes has been found to exhibit optimum catalytic activity (rate constant of 0.7072 min−1) while those with higher amounts of Pd loading showed lower catalytic activity. It is observed that retention of tubular morphology and higher anatase content play significant roles in their catalytic activity.Graphical Abstract
Journal of the American Ceramic Society
Materials Today: Proceedings
Physica E: Low-dimensional Systems and Nanostructures, 2008
... Synthesis and nonlinear optical studies of nano ZnO colloids. Bindu Krishnan a , b , Correspo... more ... Synthesis and nonlinear optical studies of nano ZnO colloids. Bindu Krishnan a , b , Corresponding Author Contact Information , E-mail The Corresponding Author , Litty Irimpan a , VPN Nampoor a and V. Kumar c. ... Available online 29 January 2008. Abstract. ...
Integrated Ferroelectrics, 2018
Preferentially {110}-oriented thin films of lead lanthanum zirconate titanate, (Pb, La) (Zr, Ti)O... more Preferentially {110}-oriented thin films of lead lanthanum zirconate titanate, (Pb, La) (Zr, Ti)O 3 [PLZT] having compositions (7/65/35), (7/60/40) and (7/56/44) across the morphotropic phase boundary with a thickness of 1.5mm were prepared on platinised silicon substrates (111) Pt/Ti/SiO 2 /Si by sol-gel spin coating technique. The crystallographic orientation and crystalline phases were analysed by X-ray diffraction and Raman spectroscopy respectively. The dependence of the transverse piezoelectric coefficient, e 31;f of the PLZT thin films on their composition and texture have been investigated. PLZT (7/60/40) thin films having a higher tetragonal content was found to exhibit optimum piezoelectric characteristics. By combining the results obtained from the dielectric and polarisationelectric field (P-E) studies, the domain switching mechanism responsible for e 31;f have been established.
Journal of Materials Science: Materials in Electronics, 2008
Glass–ceramics based on a soft piezoelectric of composition (Pb0.94Sr0.06)(Zr0.53Ti0.47)0.997Mn0.... more Glass–ceramics based on a soft piezoelectric of composition (Pb0.94Sr0.06)(Zr0.53Ti0.47)0.997Mn0.004O3 (PSZTM) have been synthesized using three different glass systems by sol–gel method. The effect of the different glass systems on the crystallization of the perovskite phase, PSZTM have been studied using XRD and DTA. The piezoelectric characteristics of the different glass–ceramic systems have been determined and are correlated with the crystallization behaviour, crystalline phase and microstructure.
Applied Physics A, 2016
Abstract In the present work, we report the aging effect in manganese (Mn) and niobium (Nb) hybri... more Abstract In the present work, we report the aging effect in manganese (Mn) and niobium (Nb) hybrid-doped PZT composition. Interestingly, it is observed that the ferroelectric aging depends on the acceptor/donor ratio. In hybrid-doped PZT, at high donor dopant concentrations, aging is not observed. The underlying mechanism is correlated with the defect chemistry of the system. It is also observed that tuning the defect chemistry is an effective strategy to realize piezoceramics with enhanced dielectric and piezoelectric characteristics.
Ceramics International, 2017
A new family of compounds with two diglycolamide moieties in their molecule have been synthesized... more A new family of compounds with two diglycolamide moieties in their molecule have been synthesized and studied as suitable extractants for trivalent actinides (An(III)) and trivalent lanthanides (Ln(III)) present in high-level wastes (HLW) issued from the PUREX process. Although the obtained distribution ratios are comparable with those from TODGA under similar experimental conditions, the bis-DGA compounds showed higher selectivity towards Ln(III). The number of bis-DGA molecules involved in the formation of the dominant complex is two, and it is possible to recover more than 99% of the extracted An and Ln with 0.01 M nitric acid in order to recycle the solvent in subsequent extraction cycles. (authors)
Journal of Sol-Gel Science and Technology, 2003
... 4. Conclusions Nanocrystalline PZT powders with good composi-tional homogeneity have been pre... more ... 4. Conclusions Nanocrystalline PZT powders with good composi-tional homogeneity have been prepared by the sol-gel method using a novel system. ... Acknowledgment We are grateful to Mr.Lachlan Cranswick, CCP14, School of Crystallography, Birkbeck College, ...
Journal of Physics D: Applied Physics, 2007
... 40 (2007) 78047810 doi:10.1088/0022-3727/40/24/032 Crystallization studies and dielectric pr... more ... 40 (2007) 78047810 doi:10.1088/0022-3727/40/24/032 Crystallization studies and dielectric properties of (Ba0.7Sr0.3)TiO3 in bariumaluminosilicate glass PV Divya, G Vignesh and V Kumar1 ... References [1] Zhai J, Yao X, Cheng X, Zhang L and Haydn C 2002 J. Mater. Sci. ...
Applied Physics Letters, 2011
Journal of Materials Science, 2002
Dispersion of PZT powder of average particle size ~75 nm in commonly used solvent systems for tap... more Dispersion of PZT powder of average particle size ~75 nm in commonly used solvent systems for tape casting namely, toluene-ethanol and MEK-ethanol (azeotropic), xylene-ethanol (zeotropic) along with triton x-100, menhaden fish oil and phosphate ester as dispersants has been studied using simple sedimentation experiments. The relative merits of these three solvent systems and dispersants in dispersing PZT powder was analyzed.
Applied Physics Letters, 2006
Nanocrystalline Zn 1−x Mg x O thin films with an average particle diameter of 60 nm have been dep... more Nanocrystalline Zn 1−x Mg x O thin films with an average particle diameter of 60 nm have been deposited on glass substrates using a sol-gel spin-coating technique. Within the range of compositions, 0 ഛ x ഛ 0.20, the optical band gap could be tuned between 3.40 and 3.83 eV. The nonlinear optical transmission in the visible spectral region is investigated using ultrafast ͑100 fs͒ and short ͑7 ns͒ laser pulses at off-resonant wavelengths. The observed nonlinearity is strong and is comparable to that recently obtained in ZnO nanocomposite layers ion-implanted with Cu + ions.
2011 National Postgraduate Conference, 2011
Fluidized beds are in use for decades in various industrial as well as other areas providing bett... more Fluidized beds are in use for decades in various industrial as well as other areas providing better efficiency and more effectiveness for processes involved. Its application has been extended to various industrial and non-industrial processes since its advent. In due course, the change in nature and new requirements of processes have necessitated alteration in the fluidized beds for custom use.
Journal of the American …, 2002
Formation of spinel phases in ZnOSb2O3 and ZnOSb2O3 Bi2O3 systems is studied by the use of X-r... more Formation of spinel phases in ZnOSb2O3 and ZnOSb2O3 Bi2O3 systems is studied by the use of X-ray diffraction. The formation of nonstoichiometric Zn2.33Sb0.67O4 phase is ob-served in both the systems at 900°C. However, in these systems, at higher temperatures (T > ...
Materials Science in Semiconductor Processing, 2016
Abstract Titania nanotube array sensitised with lead sulphide (PbS) were synthesised using a succ... more Abstract Titania nanotube array sensitised with lead sulphide (PbS) were synthesised using a successive ionic layer adsorption and reaction (SILAR) method. The PbS sensitation gives visible light sensitivity to the titania nanotube arrays. The PbS sensitised titania nanotube were characterised using X-ray diffraction, UV–visible spectroscopy and scanning electron microscopy. The stability of the PbS sensitised titania nanotube were monitored through the X-ray photoelectron spectroscopy (XPS). The photocatalytic activity of the titania sensitised with PbS were studied by monitoring the degradation of methylene blue under visible light irradiation. The photocatalytic activity and solar cell efficiency is found to be highly depended on the number of SILAR cycle used for the sensitisation of PbS on titania nanotube. The sample coated for 3 SILAR cycle of PbS shows highest solar cell efficiency and photocatalytic activity under visible light. The photocatalytic activity drastically decreased in the samples after the Ist cycle of photocatalytic reaction. The drastic decrease in the photoactivity is due to the dissolution of PbS nanoparticle on the surface of titania nanotube after the first cycle of photocatalytic reaction. XPS was employed as a tool to probe the dissolution of PbS nanoparticles.
Catalysis Letters, 2015
Titania nanotubes decorated with Pd nanoparticles were synthesised by a hydrothermal method. The ... more Titania nanotubes decorated with Pd nanoparticles were synthesised by a hydrothermal method. The increased amounts of Pd concentration is found to facilitate the anatase to rutile crystalline phase transformation as well as in collapse of the morphology as revealed by X-ray diffraction, Raman spectroscopy, scanning and transmission electron microscopy. The presence of metallic as well as the oxidized form (PdO2) of surface metal ions was characterized by using XPS. The catalytic activity of the Pd loaded titania nanotubes has been demonstrated by studying the reduction of p-nitrophenol to p-aminophenol. The 1.0 mol% Pd loaded titania nanotubes has been found to exhibit optimum catalytic activity (rate constant of 0.7072 min−1) while those with higher amounts of Pd loading showed lower catalytic activity. It is observed that retention of tubular morphology and higher anatase content play significant roles in their catalytic activity.Graphical Abstract
Journal of the American Ceramic Society
Materials Today: Proceedings