Prof R K Mandal | Indian Institute of Technology (BHU), Varanasi (original) (raw)

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Papers by Prof R K Mandal

Research paper thumbnail of Special diffraction effects in Al 70- x Co 15 Cu x+y Ni 15− y decagonal alloys

Ferroelectrics, 2001

ABSTRACT Stable decagonal phases are observed to form in both as cast and rapid solidification co... more ABSTRACT Stable decagonal phases are observed to form in both as cast and rapid solidification condition in Al70Co15Ni15 and Al65Co20Cu15 alloys. The former shows diffraction spots and diffuse intensity at positions other than those of a decagonal phase in the 10-fold and 2-fold diffraction patterns. These compounds are stabilised at a specific e/a ratio. Therefore, quaternary alloys with general alloy composition Al70-xCo15Cux+yNi15-ywere prepared with varying e/a ratio. We present here the electron metallographic characterisation of the melt-spun ribbons of different alloy compositions. Changes observed during electron microscopic investigation include streaking and diffuse intensity around the spots and also the presence of totally diffuse rows in some cases. The consequence of the latter on the underlying structure is disorder in the decagonal phase. Owing to the presence of streaking in a 10-fold like zone in the Al70Co15Cu5Ni10 composition, symmetry breaking of 10-fold to a 2-fold Diagonal phase (222) occurs. Further, the presence of a type II superstructure is also observed in Al68Co15Cu12Ni5 composition.

Research paper thumbnail of Effect of Mo addition on transformation behavior of (α2+γ) based Ti–Al alloys

Materials Science and Engineering: A, 2006

The structural and microstructural characterizations of four alloys with nominal compositions of ... more The structural and microstructural characterizations of four alloys with nominal compositions of Ti-42Al-2Mo, Ti-42Al-6Mo, Ti-40Al-2Mo, and Ti-40Al-6Mo have been studied. The 2 at.% Mo as cast alloys comprise of (␣ 2 + ␥) phases whereas those of 6 at.% Mo show (B2 + ␥) phases. The solution treatment at 1300 and 1400 • C for 1 h followed by water quenching of these alloys have shown composition specific phase transformation characteristics. The formation of the B2 phase during heat treatment has been discussed and structural model based on statistical occupancy to explain (1 0 0) peak will be presented. The change in the nature of bonding of the B2 phases in Ti-Al-M (M = Mo, Nb, V) alloys have been highlighted.

Research paper thumbnail of Effect of variation of PVP/PVA weight ratio on the behaviour of nanocrystalline silver

Research paper thumbnail of Microstructural evolution during spray forming of an Al-18Si alloy

Research paper thumbnail of Microstructural modifications induced during spray deposition of Al–Si–Fe alloys and their mechanical properties

Materials Science and Engineering: A, 2007

In the present investigation, different Al alloys such as Al–6.5%Si, Al–18%Si, Al–5%Fe and Al–18%... more In the present investigation, different Al alloys such as Al–6.5%Si, Al–18%Si, Al–5%Fe and Al–18%Si–5%Fe–1.5%Cu (wt.%) were spray deposited and the over-spray powder particles were collected. The spray formed materials as well as their as-cast counterparts were ...

Research paper thumbnail of Evolution of microstructure in spray formed Al–18%Si alloy

Materials Science and Engineering: A, 2004

Spray atomization and deposition process has emerged as an alternative to ingot and powder metall... more Spray atomization and deposition process has emerged as an alternative to ingot and powder metallurgy routes. In the present investigation, we study the microstructural control during spray deposition of hypereutectic Al-Si alloy, employing different nozzle to substrate distances. Spray deposition is carried out using convergent-divergent close-coupled nozzle design at deposition distances of 200, 300, 450, and 550 mm. Microstructural characterization of oversprayed powders as well as spray formed deposits was performed. Microstructural features obtained at smaller deposition distance consist of co-existing primary Si phase and needle like eutectic Si. Dendrites of ␣-Al phase are observed indicating a large undercooling of the liquid pool prior to solidification. A large number of pre-solidified particles with very fine microstructure, embedded in a relatively coarse region, typically characterize those evolved at large deposition distances. However, at intermediate deposition distances, uniform and refined primary Si phases, 3-8 m size, are observed. An undercooling effect is manifested in both the spray deposits as well as powder particles. These microstructural features have been discussed in light of a proposed model, which describes the presence of two layers (1) solidification layer and (2) interaction layer in the liquid pool.

Research paper thumbnail of RICE EXTRACT-ASSISTED GREEN SYNTHESIS OF Au NANOPARTICLES: CATALYTIC AND SERS ACTIVITIES

Surface Review and Letters

In this paper, we investigate the impact of rice-starch stabilization of gold nanoparticles (AuNP... more In this paper, we investigate the impact of rice-starch stabilization of gold nanoparticles (AuNPs) on their catalytic and surface-enhanced Raman spectroscopy (SERS) activities. A typical green synthesis protocol was used to prepare AuNPs with rice-starch functioning as the reductant and the stabilizer. The localized surface plasmon resonance (LSPR) of the starch-stabilized AuNPs is pH-sensitive and got red-shifted with the medium’s pH. The average size of the AuNPs formed decreased with the amount of rice-starch up to a certain level. TEM result shows that the polymeric behavior of starch extract may help synthesize the Au nanorod morphologies. AuNPs stabilized by different amounts of rice-starch were applied as the catalysts for the model [Formula: see text]-nitrophenol reduction reaction. For all AuNP catalysts used, the reaction followed pseudo-first-order kinetics. The catalyst turnover frequencies increased up to a certain level of starch functionalization. Further increase in...

Research paper thumbnail of ZrxFe3−xO4 (0.01 ≤ x ≤ 1.0) nanoparticles: a possible magnetic in vivo switch

RSC Advances, 2016

AC field controlled temperature during magnetic hyperthermia for ZrxFe3−xO4 (0.01 ≤ x ≤ 1.0) base... more AC field controlled temperature during magnetic hyperthermia for ZrxFe3−xO4 (0.01 ≤ x ≤ 1.0) based ferrofluids. The unexpected behavior observed despite their high magnetization (~50 Am2 kg−1) and Curie temperature (TC > 300 °C).

Research paper thumbnail of Solvothermal synthesis of CuO–MgO nanocomposite particles and their catalytic applications

RSC Advances, 2016

CuO–MgO nanocomposites were prepared by a solvothermal procedure.

Research paper thumbnail of Novel aspects of higher dimensional structural description of trigonal, pentagonal and their related phases

A four dimensional description for the trigonal phase is presented. It has been demonstrated that... more A four dimensional description for the trigonal phase is presented. It has been demonstrated that it is possible to model one dimensional quasiperiodic structure with trigonal symmetry apart from recovering the Miller-Bravais scheme for the description of hexagonal phases. A similar discussion on the two classes of decagonal phases having 10/m and 10 5 symmetries will be given. The distinction in the six dimensional models of the two classes of solids has been pointed out. The zone rules for all the cases have been formulated. The critical comparison for the structural description of trigonal, decagonal and related phases in terms of higher dimension is made. The unification achieved in the higher dimensional structural models of various phases has been emphasized. The importance of such models for the study of structural phase transformation has been indicated.

Research paper thumbnail of Special Diffraction Effects in Al7o_xCo15Cux+yNi15_y Decagonal Alloys

Stable decagonal phases are observed to form in both as cast and rapid solidification condition i... more Stable decagonal phases are observed to form in both as cast and rapid solidification condition in Al70Co15Nil5 and A16SCo20Cu15 alloys. The former shows diffraction spots and diffuse intensity at positions other than those of a decagonal phase in the 10-fold and 2-fold diffraction patterns. These compounds are stabilised at a specific e/a ratio. Therefore, quaternary alloys with general alloy composition A17o-,Co15Cux,,,Nils-,, were prepared with varying e/a ratio. We present here the electron metallographic characterisation of the melt-spun ribbons of different alloy compositions. Changes observed during electron microscopic investigation include streaking and diffuse intensity around the spots and also the presence of totally diffuse rows in some cases. The consequence of the latter on the underlying structure is disorder in the decagonal phase. Owing to the presence of streaking in a 10-fold like zone in the A170Co15Cu5Nilo composition, symmetry breaking of 10-fold to a 2-fold Diagonal phase (222) occurs. Further, the presence of a type II superstructure is also observed in A168Co 15Cu 17Ni5 composition.

Research paper thumbnail of Growth of carbon nanotubes on quasicrystalline alloys

We report on the synthesis of carbon nanotubes on quasicrystalline alloys. Aligned multiwalled ca... more We report on the synthesis of carbon nanotubes on quasicrystalline alloys. Aligned multiwalled carbon nanotubes (MWNTs) on the conducting faces of decagonal quasicrystals were synthesized using floating catalyst chemical vapor deposition. The alignment of the nanotubes was found perpendicular to the decagonal faces of the quasicrystals. A comparison between the growth and tube quality has also been made between tubes grown on various quasicrystalline and SiO 2 substrates. While a significant MWNT growth was observed on decagonal quasicrystalline substrate, there was no significant growth observed on icosahedral quasicrystalline substrate. Raman spectroscopy and high resolution transmission electron microscopy (HRTEM) results show high crystalline nature of the nanotubes. Presence of continuous iron filled core in the nanotubes grown on these substrates was also observed, which is typically not seen in MWNTs grown using similar process on silicon and/or silicon dioxide substrates. The study has important implications for understanding the growth mechanism of MWNTs on conducting substrates which have potential applications as heat sinks.

Research paper thumbnail of Localized surface plasmon behavior of Ag-Cu alloy nanoparticles stabilized by rice-starch and gelatin

AIP Advances, 2015

The purpose of this communication was to understand localized surface plasmon behavior of a serie... more The purpose of this communication was to understand localized surface plasmon behavior of a series of Ag-Cu alloy nanoparticles capped by rice-starch and gelatin. The structures of dried powders were investigated with the help of X-ray diffraction. The analysis revealed Ag-rich and Cu-rich phases with maximum solid solubility of Cu ∼9 atom per cent; 8 atom per cent and Ag ∼ 16 atom per cent; 14 atom per cent in rice-starch and gelatin capped samples respectively. Transmission electron microscope was used for knowing the particle size as well as to supplement FCC phase formations of Ag-rich and Cu-rich solid phases arrived at based on X-ray diffraction studies. The UV-Vis spectra of sols were examined for the formation and stability of alloy nanoparticles. The temporal evolution of LSPR curves gave us to assert that the sol is stable for more than two months. Small angle X-ray scattering in the sol state was extensively utilized to understand nature of suspensions in terms of fractals. Such a study is important for having a correlation between LSPR behaviors with those of nanoparticle dispersion in aqueous media. It is believed that this work will be a contribution to the emerging field of plasmonics that include applications in the area of photophysical processes and photochemical reactions.

Research paper thumbnail of Vacancy-mediated structural changes in Au–Cu nanoparticles

Philosophical Magazine Letters

Research paper thumbnail of Effects of Mode of Deformation and Extent of Reduction on Evolution of {111}-Fiber During Cold Rolling of Ni-16Cr Alloy

Metallurgical and Materials Transactions A

Research paper thumbnail of ZnxFe3−xO4 (0.01 ≤ x ≤ 0.8) nanoparticles for controlled magnetic hyperthermia application

New Journal of Chemistry

Stable temperature was attained during magnetic hyperthermia by Zn substituted magnetite nanopart... more Stable temperature was attained during magnetic hyperthermia by Zn substituted magnetite nanoparticles.

Research paper thumbnail of {"__content__"=>"Defect mediated magnetic transitions in Fe and Mn doped MoS.", "sub"=>{"__content__"=>"2"}}

Physical chemistry chemical physics : PCCP, Jan 13, 2018

We report single-phase syntheses of undoped 2H-MoS2 as well as Mn and Fe doped MoS2 by a facile h... more We report single-phase syntheses of undoped 2H-MoS2 as well as Mn and Fe doped MoS2 by a facile hydrothermal route. The formation of the 2H-MoS2 phase was confirmed by XRD and was corroborated with Raman spectra. The morphology of the doped and undoped MoS2 nanostructures comprised sheets, as revealed by TEM and STEM images. The fine granular structure was observed by high resolution TEM micrographs. The STEM-EDS results show dopant concentrations of ∼1 atom% corresponding to Mn and Fe in doped MoS2. The undoped MoS2 revealed diamagnetic behavior at room temperature and paramagnetic behavior in the range (100 to 300 K). The Mn-MoS2 sample displayed ferromagnetism below 20 K with a coercive field of ∼50 Oe. Such a sample may be utilized for magnetic switching purposes at low temperatures. The onset of the antiferromagnetic interaction was observed below 145 K in Fe-MoS2 samples. They have been understood in terms of long-range magnetic interactions amongst the dipole moments mediated...

Research paper thumbnail of Projection method for 4d non-orthogonal hyperlattices

Research paper thumbnail of Unique Indexing Scheme of Decagonal Phases Based on a Six Dimensional Model

MRS Proceedings

ABSTRACTMandal and Lele (1989) have proposed a six dimensional model for the structural descripti... more ABSTRACTMandal and Lele (1989) have proposed a six dimensional model for the structural description of the decagonal phases. The integral linear combination of six basis vectors for indicating a physical vector in their model, however, leaves the problem of redundancy in indexing. While revisiting their model, we have noted that the condition of a null vector in physical space permits the formulation of unique indexing scheme both in physical reciprocal and direct spaces, we will demonstrate that our scheme, unlike all previously discussed ones, relies only on the information contained in the model. It will also be shown that diffracted spot having equivalent indices possesses identical intensity. This aspect, though equally important, has been totally ignored in the past. We shall substantiate our claim by taking examples from the known decagonal phases. We shall also present parity condition on indices that will be helpful in discussing subtle features of diffraction patterns. The...

Research paper thumbnail of Effect of discretization and finite nuclei radius on Kolmogorov-Johnson-Mehl-Avrami isothermal kinetics: A 2-dimensional study

Transactions of the Indian Institute of Metals

Research paper thumbnail of Special diffraction effects in Al 70- x Co 15 Cu x+y Ni 15− y decagonal alloys

Ferroelectrics, 2001

ABSTRACT Stable decagonal phases are observed to form in both as cast and rapid solidification co... more ABSTRACT Stable decagonal phases are observed to form in both as cast and rapid solidification condition in Al70Co15Ni15 and Al65Co20Cu15 alloys. The former shows diffraction spots and diffuse intensity at positions other than those of a decagonal phase in the 10-fold and 2-fold diffraction patterns. These compounds are stabilised at a specific e/a ratio. Therefore, quaternary alloys with general alloy composition Al70-xCo15Cux+yNi15-ywere prepared with varying e/a ratio. We present here the electron metallographic characterisation of the melt-spun ribbons of different alloy compositions. Changes observed during electron microscopic investigation include streaking and diffuse intensity around the spots and also the presence of totally diffuse rows in some cases. The consequence of the latter on the underlying structure is disorder in the decagonal phase. Owing to the presence of streaking in a 10-fold like zone in the Al70Co15Cu5Ni10 composition, symmetry breaking of 10-fold to a 2-fold Diagonal phase (222) occurs. Further, the presence of a type II superstructure is also observed in Al68Co15Cu12Ni5 composition.

Research paper thumbnail of Effect of Mo addition on transformation behavior of (α2+γ) based Ti–Al alloys

Materials Science and Engineering: A, 2006

The structural and microstructural characterizations of four alloys with nominal compositions of ... more The structural and microstructural characterizations of four alloys with nominal compositions of Ti-42Al-2Mo, Ti-42Al-6Mo, Ti-40Al-2Mo, and Ti-40Al-6Mo have been studied. The 2 at.% Mo as cast alloys comprise of (␣ 2 + ␥) phases whereas those of 6 at.% Mo show (B2 + ␥) phases. The solution treatment at 1300 and 1400 • C for 1 h followed by water quenching of these alloys have shown composition specific phase transformation characteristics. The formation of the B2 phase during heat treatment has been discussed and structural model based on statistical occupancy to explain (1 0 0) peak will be presented. The change in the nature of bonding of the B2 phases in Ti-Al-M (M = Mo, Nb, V) alloys have been highlighted.

Research paper thumbnail of Effect of variation of PVP/PVA weight ratio on the behaviour of nanocrystalline silver

Research paper thumbnail of Microstructural evolution during spray forming of an Al-18Si alloy

Research paper thumbnail of Microstructural modifications induced during spray deposition of Al–Si–Fe alloys and their mechanical properties

Materials Science and Engineering: A, 2007

In the present investigation, different Al alloys such as Al–6.5%Si, Al–18%Si, Al–5%Fe and Al–18%... more In the present investigation, different Al alloys such as Al–6.5%Si, Al–18%Si, Al–5%Fe and Al–18%Si–5%Fe–1.5%Cu (wt.%) were spray deposited and the over-spray powder particles were collected. The spray formed materials as well as their as-cast counterparts were ...

Research paper thumbnail of Evolution of microstructure in spray formed Al–18%Si alloy

Materials Science and Engineering: A, 2004

Spray atomization and deposition process has emerged as an alternative to ingot and powder metall... more Spray atomization and deposition process has emerged as an alternative to ingot and powder metallurgy routes. In the present investigation, we study the microstructural control during spray deposition of hypereutectic Al-Si alloy, employing different nozzle to substrate distances. Spray deposition is carried out using convergent-divergent close-coupled nozzle design at deposition distances of 200, 300, 450, and 550 mm. Microstructural characterization of oversprayed powders as well as spray formed deposits was performed. Microstructural features obtained at smaller deposition distance consist of co-existing primary Si phase and needle like eutectic Si. Dendrites of ␣-Al phase are observed indicating a large undercooling of the liquid pool prior to solidification. A large number of pre-solidified particles with very fine microstructure, embedded in a relatively coarse region, typically characterize those evolved at large deposition distances. However, at intermediate deposition distances, uniform and refined primary Si phases, 3-8 m size, are observed. An undercooling effect is manifested in both the spray deposits as well as powder particles. These microstructural features have been discussed in light of a proposed model, which describes the presence of two layers (1) solidification layer and (2) interaction layer in the liquid pool.

Research paper thumbnail of RICE EXTRACT-ASSISTED GREEN SYNTHESIS OF Au NANOPARTICLES: CATALYTIC AND SERS ACTIVITIES

Surface Review and Letters

In this paper, we investigate the impact of rice-starch stabilization of gold nanoparticles (AuNP... more In this paper, we investigate the impact of rice-starch stabilization of gold nanoparticles (AuNPs) on their catalytic and surface-enhanced Raman spectroscopy (SERS) activities. A typical green synthesis protocol was used to prepare AuNPs with rice-starch functioning as the reductant and the stabilizer. The localized surface plasmon resonance (LSPR) of the starch-stabilized AuNPs is pH-sensitive and got red-shifted with the medium’s pH. The average size of the AuNPs formed decreased with the amount of rice-starch up to a certain level. TEM result shows that the polymeric behavior of starch extract may help synthesize the Au nanorod morphologies. AuNPs stabilized by different amounts of rice-starch were applied as the catalysts for the model [Formula: see text]-nitrophenol reduction reaction. For all AuNP catalysts used, the reaction followed pseudo-first-order kinetics. The catalyst turnover frequencies increased up to a certain level of starch functionalization. Further increase in...

Research paper thumbnail of ZrxFe3−xO4 (0.01 ≤ x ≤ 1.0) nanoparticles: a possible magnetic in vivo switch

RSC Advances, 2016

AC field controlled temperature during magnetic hyperthermia for ZrxFe3−xO4 (0.01 ≤ x ≤ 1.0) base... more AC field controlled temperature during magnetic hyperthermia for ZrxFe3−xO4 (0.01 ≤ x ≤ 1.0) based ferrofluids. The unexpected behavior observed despite their high magnetization (~50 Am2 kg−1) and Curie temperature (TC > 300 °C).

Research paper thumbnail of Solvothermal synthesis of CuO–MgO nanocomposite particles and their catalytic applications

RSC Advances, 2016

CuO–MgO nanocomposites were prepared by a solvothermal procedure.

Research paper thumbnail of Novel aspects of higher dimensional structural description of trigonal, pentagonal and their related phases

A four dimensional description for the trigonal phase is presented. It has been demonstrated that... more A four dimensional description for the trigonal phase is presented. It has been demonstrated that it is possible to model one dimensional quasiperiodic structure with trigonal symmetry apart from recovering the Miller-Bravais scheme for the description of hexagonal phases. A similar discussion on the two classes of decagonal phases having 10/m and 10 5 symmetries will be given. The distinction in the six dimensional models of the two classes of solids has been pointed out. The zone rules for all the cases have been formulated. The critical comparison for the structural description of trigonal, decagonal and related phases in terms of higher dimension is made. The unification achieved in the higher dimensional structural models of various phases has been emphasized. The importance of such models for the study of structural phase transformation has been indicated.

Research paper thumbnail of Special Diffraction Effects in Al7o_xCo15Cux+yNi15_y Decagonal Alloys

Stable decagonal phases are observed to form in both as cast and rapid solidification condition i... more Stable decagonal phases are observed to form in both as cast and rapid solidification condition in Al70Co15Nil5 and A16SCo20Cu15 alloys. The former shows diffraction spots and diffuse intensity at positions other than those of a decagonal phase in the 10-fold and 2-fold diffraction patterns. These compounds are stabilised at a specific e/a ratio. Therefore, quaternary alloys with general alloy composition A17o-,Co15Cux,,,Nils-,, were prepared with varying e/a ratio. We present here the electron metallographic characterisation of the melt-spun ribbons of different alloy compositions. Changes observed during electron microscopic investigation include streaking and diffuse intensity around the spots and also the presence of totally diffuse rows in some cases. The consequence of the latter on the underlying structure is disorder in the decagonal phase. Owing to the presence of streaking in a 10-fold like zone in the A170Co15Cu5Nilo composition, symmetry breaking of 10-fold to a 2-fold Diagonal phase (222) occurs. Further, the presence of a type II superstructure is also observed in A168Co 15Cu 17Ni5 composition.

Research paper thumbnail of Growth of carbon nanotubes on quasicrystalline alloys

We report on the synthesis of carbon nanotubes on quasicrystalline alloys. Aligned multiwalled ca... more We report on the synthesis of carbon nanotubes on quasicrystalline alloys. Aligned multiwalled carbon nanotubes (MWNTs) on the conducting faces of decagonal quasicrystals were synthesized using floating catalyst chemical vapor deposition. The alignment of the nanotubes was found perpendicular to the decagonal faces of the quasicrystals. A comparison between the growth and tube quality has also been made between tubes grown on various quasicrystalline and SiO 2 substrates. While a significant MWNT growth was observed on decagonal quasicrystalline substrate, there was no significant growth observed on icosahedral quasicrystalline substrate. Raman spectroscopy and high resolution transmission electron microscopy (HRTEM) results show high crystalline nature of the nanotubes. Presence of continuous iron filled core in the nanotubes grown on these substrates was also observed, which is typically not seen in MWNTs grown using similar process on silicon and/or silicon dioxide substrates. The study has important implications for understanding the growth mechanism of MWNTs on conducting substrates which have potential applications as heat sinks.

Research paper thumbnail of Localized surface plasmon behavior of Ag-Cu alloy nanoparticles stabilized by rice-starch and gelatin

AIP Advances, 2015

The purpose of this communication was to understand localized surface plasmon behavior of a serie... more The purpose of this communication was to understand localized surface plasmon behavior of a series of Ag-Cu alloy nanoparticles capped by rice-starch and gelatin. The structures of dried powders were investigated with the help of X-ray diffraction. The analysis revealed Ag-rich and Cu-rich phases with maximum solid solubility of Cu ∼9 atom per cent; 8 atom per cent and Ag ∼ 16 atom per cent; 14 atom per cent in rice-starch and gelatin capped samples respectively. Transmission electron microscope was used for knowing the particle size as well as to supplement FCC phase formations of Ag-rich and Cu-rich solid phases arrived at based on X-ray diffraction studies. The UV-Vis spectra of sols were examined for the formation and stability of alloy nanoparticles. The temporal evolution of LSPR curves gave us to assert that the sol is stable for more than two months. Small angle X-ray scattering in the sol state was extensively utilized to understand nature of suspensions in terms of fractals. Such a study is important for having a correlation between LSPR behaviors with those of nanoparticle dispersion in aqueous media. It is believed that this work will be a contribution to the emerging field of plasmonics that include applications in the area of photophysical processes and photochemical reactions.

Research paper thumbnail of Vacancy-mediated structural changes in Au–Cu nanoparticles

Philosophical Magazine Letters

Research paper thumbnail of Effects of Mode of Deformation and Extent of Reduction on Evolution of {111}-Fiber During Cold Rolling of Ni-16Cr Alloy

Metallurgical and Materials Transactions A

Research paper thumbnail of ZnxFe3−xO4 (0.01 ≤ x ≤ 0.8) nanoparticles for controlled magnetic hyperthermia application

New Journal of Chemistry

Stable temperature was attained during magnetic hyperthermia by Zn substituted magnetite nanopart... more Stable temperature was attained during magnetic hyperthermia by Zn substituted magnetite nanoparticles.

Research paper thumbnail of {"__content__"=>"Defect mediated magnetic transitions in Fe and Mn doped MoS.", "sub"=>{"__content__"=>"2"}}

Physical chemistry chemical physics : PCCP, Jan 13, 2018

We report single-phase syntheses of undoped 2H-MoS2 as well as Mn and Fe doped MoS2 by a facile h... more We report single-phase syntheses of undoped 2H-MoS2 as well as Mn and Fe doped MoS2 by a facile hydrothermal route. The formation of the 2H-MoS2 phase was confirmed by XRD and was corroborated with Raman spectra. The morphology of the doped and undoped MoS2 nanostructures comprised sheets, as revealed by TEM and STEM images. The fine granular structure was observed by high resolution TEM micrographs. The STEM-EDS results show dopant concentrations of ∼1 atom% corresponding to Mn and Fe in doped MoS2. The undoped MoS2 revealed diamagnetic behavior at room temperature and paramagnetic behavior in the range (100 to 300 K). The Mn-MoS2 sample displayed ferromagnetism below 20 K with a coercive field of ∼50 Oe. Such a sample may be utilized for magnetic switching purposes at low temperatures. The onset of the antiferromagnetic interaction was observed below 145 K in Fe-MoS2 samples. They have been understood in terms of long-range magnetic interactions amongst the dipole moments mediated...

Research paper thumbnail of Projection method for 4d non-orthogonal hyperlattices

Research paper thumbnail of Unique Indexing Scheme of Decagonal Phases Based on a Six Dimensional Model

MRS Proceedings

ABSTRACTMandal and Lele (1989) have proposed a six dimensional model for the structural descripti... more ABSTRACTMandal and Lele (1989) have proposed a six dimensional model for the structural description of the decagonal phases. The integral linear combination of six basis vectors for indicating a physical vector in their model, however, leaves the problem of redundancy in indexing. While revisiting their model, we have noted that the condition of a null vector in physical space permits the formulation of unique indexing scheme both in physical reciprocal and direct spaces, we will demonstrate that our scheme, unlike all previously discussed ones, relies only on the information contained in the model. It will also be shown that diffracted spot having equivalent indices possesses identical intensity. This aspect, though equally important, has been totally ignored in the past. We shall substantiate our claim by taking examples from the known decagonal phases. We shall also present parity condition on indices that will be helpful in discussing subtle features of diffraction patterns. The...

Research paper thumbnail of Effect of discretization and finite nuclei radius on Kolmogorov-Johnson-Mehl-Avrami isothermal kinetics: A 2-dimensional study

Transactions of the Indian Institute of Metals