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Atikur Rahman

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Papers by Atikur Rahman

Agricultural Consumption Culture and Ecological Transformation:Bangladesh Perspective

Asian Development Policy Review, 2017

The paper mainly focuses the poor consumption culture and its adverse impact on environmental ser... more The paper mainly focuses the poor consumption culture and its adverse impact on environmental services. It is found the study that social regulation, values, choice and habits of Bangladesh people remain in a traditional and poor standard that cannot foster individual life as well as the socio-ecological aspects. Indiscriminate and excessive use of agro-inputs (fertilizer, insecticides, energy, and water) causes fatal risks to agronatural resources. In addition, aquatic and livestock resources are gradually being depleted and exploited through consumption and production in unsustainable or poor sustainable way. The paper is written based on the content analysis in a qualitative approach. The documents of national and international government and nongovernment offices, journal articles, media report, book etc. have critically been reviewed for data collection. Mainly secondary data has been used in the study, but the empirical observation is applied herein as a primary data source also. A social movement is to be introduced within the entire stakeholder around Bangladesh. Yet, mass media, civil society, intellectuals and policy makers have to come forward to launch the movement so that the peasant community can be regulated by morals, values, principles to eradicate bad agricultural consumption and production towards sustainable development. Contribution/ Originality: The study is one of very few studies which have investigated the farmers" poor agricultural consumption pattern that stimulates them over-use of chemical inputs into their agro framings that causes serious risks to agro ecology. The paper"s primary contribution is finding that poor consumption culture derives from traditional agro habits, lack of education, training, and rented land farming.

Sub-50 Nanometer Self-Assembled Nanotextures for Enhanced Broadband Antireflection in Silicon Solar Cells

Nature Communications

Materials providing broadband light antireflection have applications as highly transparent window... more Materials providing broadband light antireflection have applications as highly transparent window coatings, military camouflage, and coatings for efficiently coupling light into solar cells and out of light emitting diodes. In this work, densely packed silicon nanotextures with feature sizes smaller than 50 nanometers enhance the broadband antireflection compared to that predicted by their geometry alone. A significant fraction of the nanotexture volume comprises a surface layer whose optical properties differ substantially from those of the bulk, providing the key to improved performance. The nanotexture reflectivity is quantitatively well modeled after accounting for both its profile and changes in refractive index at the surface. We employ block copolymer self assembly for precise and tunable nanotexture design in the range of ~10 to 70 nanometers across macroscopic solar cell areas. Implementing this efficient antireflection approach in crystalline silicon solar cells significan...

Observation of angle-dependent transmission of Dirac electrons in graphene hetero junctions

Asymmetric scattering of Dirac electrons and holes in graphene

Collapse and Reversibility of the Superhydrophobic State on Nanotextured Surfaces

Physical Review Letters, 2014

Superhydrophobic coatings repel liquids by trapping air inside microscopic surface textures. Howe... more Superhydrophobic coatings repel liquids by trapping air inside microscopic surface textures. However, the resulting composite interface is prone to collapse under external pressure. Nanometer-size textures should facilitate more resilient coatings owing to geometry and confinement effects at the nanoscale. Here, we use in situ x-ray diffraction to study the collapse of the superhydrophobic state in arrays of ≈20 nm-wide silicon textures with cylindrical, conical, and linear features defined by block-copolymer self-assembly and plasma etching. We reveal that the superhydrophobic state vanishes above critical pressures which depend on texture shape and size. This phenomenon is irreversible for all but the conical surface textures which exhibit a spontaneous, partial reappearance of the trapped gas phase upon liquid depressurization. This process is influenced by the kinetics of gas-liquid exchange.

Sub-50-nm self-assembled nanotextures for enhanced broadband antireflection in silicon solar cells

Nature Communications, 2015

Materials providing broadband light antireflection have applications as highly transparent window... more Materials providing broadband light antireflection have applications as highly transparent window coatings, military camouflage, and coatings for efficiently coupling light into solar cells and out of light-emitting diodes. In this work, densely packed silicon nanotextures with feature sizes smaller than 50 nm enhance the broadband antireflection compared with that predicted by their geometry alone. A significant fraction of the nanotexture volume comprises a surface layer whose optical properties differ substantially from those of the bulk, providing the key to improved performance. The nanotexture reflectivity is quantitatively well-modelled after accounting for both its profile and changes in refractive index at the surface. We employ block copolymer self-assembly for precise and tunable nanotexture design in the range of B10-70 nm across macroscopic solar cell areas. Implementing this efficient antireflection approach in crystalline silicon solar cells significantly betters the performance gain compared with an optimized, planar antireflection coating.

Quantum Noise and Asymmetric Scattering of Electrons and Holes in Graphene

Nano Letters, 2014

We present measurements of quantum interference noise in double-gated single layer graphene devic... more We present measurements of quantum interference noise in double-gated single layer graphene devices at low temperatures. The noise characteristics show a nonmonotonic dependence on carrier density, which is related to the interplay between charge inhomogeneity and different scattering mechanisms. Linearly increasing 1/f noise at low carrier densities coincides with the observation of weak localization, suggesting the importance of short-range disorder in this regime. Using perpendicular and parallel p−n junctions, we find that the observed asymmetry of the noise with respect to the Dirac point can be related to asymmetric scattering of electrons and holes on the disorder potential.

Study of cyclic hot corrosion of nanostructured Cr/Co–Al coatings on superalloy

Materials Chemistry and Physics, 2011

Nanostructured Cr/Co-Al coatings were deposited on Superni-718 substrate by DC/RF magnetron sputt... more Nanostructured Cr/Co-Al coatings were deposited on Superni-718 substrate by DC/RF magnetron sputtering in the present work. Hot corrosion studies were conducted on bare substrate and the Cr/Co-Al coated Superni-718 after exposure to a molten salt environment of Na 2 SO 4-60%V 2 O 5 at 900 • C under cyclic conditions. The weight change measurements were made to calculate the cyclic hot corrosion kinetics of the coatings at 900 • C. The microstructural features of the as deposited coatings were characterized by FE-SEM, AFM and XRD. It was observed that the corrosion rate of Cr/Co-Al coated superalloy is lower than that of the uncoated superalloy due to the formation of continuous, dense, adherent and protective oxide scale over the surface of the coatings. The protective oxide scales are basically the thin layer of Cr 2 O 3 , Al 2 O 3 , and CoCr 2 O 4 which has formed over the Cr/Co-Al coated superalloy substrate exposed to molten salt environment at temperature, 900 • C.

Prevalence and Associated Risk Factors of Myiasis in Different Areas of Chittagong, Bangladesh

Research Journal for Veterinary Practitioners, 2014

A One year eventual study was conducted to detect the prevalence and feasible risk factors of myi... more A One year eventual study was conducted to detect the prevalence and feasible risk factors of myiasis in various species of animal in different areas of Chittagong, Bangladesh from March 2012 to February 2013. By Cross-questioning over animal rearers and with clinical examinations myiatic cases were identified and varied risk factors were distinguished. 226 cases were noted manifesting signs of myiasis. Prevalence rates were goat 69% and cattle 22%; wherever seasonal prevalence was explored highest in autumn (55.5%) than cold (11.6%) (p>0.05). Statistically significant difference in the prevalence was reputed with breed, age, sex, wound depthness, temperature and attitude of animal (p ≤0.05). Above 6 months aged animals (75.5%) and cross breeds (34.2%) were mostly infected where females (64.5%) were more prone to myiasis. Foul odorous abscess with wound, breach after delivery, umbilical infection, dirtiness, fecal and urine contamination, bed sore were the most habitual risk factors, though findings were not significant (p >0.05). Most exposed sites were vagina and perineal region, inter digital space, tail, brisket, navel, scrotum, inguinal region and gum. The study has remarked probable health hazards caused by flies in animal that will promote animal rearers in avoiding and clinically managing them. Additional widespread studies are suggested as molecular identification of species of flies and economic analysis caused by myiasis.

Anomalous noise characteristics in graphene pn junctions

Bulletin of the American Physical …, 2012

Graphene pn junctions provide an interesting platform to study the Dirac nature of charge carrier... more

Transmission of phase information between electrons and holes in graphene

Physical Review B, 2013

We have studied quantum interference between electrons and holes in a split-ring gold interferome... more We have studied quantum interference between electrons and holes in a split-ring gold interferometer with graphene arms, one of which contained a pn junction. The carrier type, the pn junction and the phase of the oscillations in a magnetic field were controlled by a top gate placed over one of the arms. We observe clear Aharonov-Bohm oscillations at the Dirac point and away from it, regardless of the carrier type in each arm. We also find clear oscillations when one arm of the interferometer contains a single pn junction, allowing us to study the interplay of Aharonov-Bohm effect and Klein tunneling.

Observation of charge density wave characteristics in conducting polymer nanowires: Possibility of Wigner crystallization

Physical Review B, 2007

We have presented here results of a low temperature transport study of polypyrrole nanowires havi... more We have presented here results of a low temperature transport study of polypyrrole nanowires having low electron densities, which shows characteristics of charge density waves observed in structurally ordered materials. The current-voltage characteristics of all these nanowires show a power-law dependence on voltage and temperature and a "gap" that decreases rapidly as the temperature is increased, confirming the existence of a long-range electron-electron interaction in the nanowires. A switching transition to highly conducting state has been observed above a threshold voltage, which can be tuned by changing the diameters of the nanowires and the temperature. Negative differential resistance and enhancement of noise have been observed above the threshold. These experimental results give evidence in favor of Wigner crystallization in these nanowires.

Processing and characterisation of nanostructured Al doped ZnO antireflection films

Materials Technology: Advanced Performance Materials, 2013

Al doped ZnO films (3 at-%) were developed on soda lime glass substrate by electroless deposition... more Al doped ZnO films (3 at-%) were developed on soda lime glass substrate by electroless deposition. The films were characterised by X-ray diffraction (XRD), field scanning electron microscope (FESEM/EDS), atomic force microscope (AFM) and UV visible spectrophotometer. Xray diffraction analysis indicates that preferential growth of the films are (101) reflection peak in the 400, 500 and 600uC annealed films. FESEM surface and cross-section analysis exhibit that Al doped ZnO film has dense and compact grains as compared to undoped ZnO film. Film is composed of Zn, Al and O is confirmed by EDS analysis. Surface roughness of the film is determined by AFM. The Al doped ZnO films exhibit excellent optical transmittance (more than 80%) and minimum absorbance spectra in visible range 400-800 nm wavelength. Al doped ZnO film annealed at 500uC is suitable for antireflection coating in silicon solar cell.

High temperature oxidation behavior of nanostructured Ni–Al coatings on superalloy

Journal of Alloys and Compounds, 2009

The high temperature oxidation behavior of magnetron sputtered Ni-Al coatings on the superalloy s... more The high temperature oxidation behavior of magnetron sputtered Ni-Al coatings on the superalloy substrate has been studied in the present work. The microstructural and morphological features of Ni-Al coatings were characterized by FE-SEM, AFM and XRD. Thermo gravimetric technique was used to investigate the oxidation behavior of the coatings, in air at 900 • C. The growth kinetics of oxide layers was predicted from the weight changes of the coating samples measured during oxidation. It was found that the corrosion rate of nanostructured Ni-Al coated superalloy was lower than that of the uncoated superalloy due to the formation of continuous, dense, adherent and protective oxide scale over the surface of the coatings. The morphological features and phases of the corroded coatings were used to elucidate the mechanism of high temperature oxidation. A continuous thin layer of protective oxide films such as NiO and Al 2 O 3 has formed over the Ni-Al coatings exposed to air at high temperature, 900 • C.

Anomalous effect of biased oscillating field on the switching behaviour: Modulating friction of charge carriers in nanowires

EPL (Europhysics Letters), 2009

... Rev. B, 73 (2006) 125313. [7] Rahman A., Sanyal MK, Gangopadhayy R. and De A., Chem. Phys. Le... more

Enhancement of electron–electron interactions in chemically synthesized polymer nanowires

Chemical Physics Letters, 2007

We report here a comparison of electronic transport properties of conducting polymer nanowires sy... more We report here a comparison of electronic transport properties of conducting polymer nanowires synthesized by chemical and electrochemical methods inside nanopores. Electronic transport properties of these nanowires show a power-law behavior (I µ V 1+b) at low temperature. Chemically synthesized nanowires exhibit higher values of b and these values increase further with the diameter of nanowires. Zero bias differential conductance of all the nanowires increase with increasing diameter and temperature but the obtained values of chemically synthesized nanowires were always found to be much lower. These results indicate enhancement of electron-electron interactions in chemically synthesized nanowires.

Negative capacitance in Wigner crystal forming polymer nanowires

Applied Physics Letters, 2009

Negative capacitance has been observed in conducting polymer nanowires. These nanowires exhibit f... more Negative capacitance has been observed in conducting polymer nanowires. These nanowires exhibit features of one-dimensional Wigner crystals, such as switching transition that reduces resistance by several orders of magnitude, negative differential resistance, and enhancement of noise in the switched state. Negative capacitance is theoretically predicted characteristic feature of a Wigner crystal. The magnitude of negative capacitance increases with increasing bias voltage below the switching transition. Above switching transition the magnitude decreases with increasing current bias. The capacitance goes from negative to positive value as the features of Wigner crystal state disappear with increasing temperature.

Diameter-dependent coercivity of cobalt nanowires

Applied Physics A, 2013

We show that the coercivity of electrochemically grown cobalt nanowires (NWs) within the pores of... more We show that the coercivity of electrochemically grown cobalt nanowires (NWs) within the pores of a polycarbonate membrane can be changed to a large extent by tuning their diameters. The face centered cubic crystalline structure of the NWs having diameter in the range of 10 to 200 nm could be retained. Smaller diameter wires (below 30 nm) are found to be single crystalline and oriented in the [110] growth direction, but for higher diameter wires the crystallite size became very small. Magnetization measurements with an applied field parallel to the axis of the NWs show that the nature of the M-H loop changes from square to linear as the diameter of the NWs increases. The coercivity was found to be 1700 Oe and 480 Oe at 5 K (1000 Oe and 250 Oe at 300 K) for 10 nm and 100 nm wires, respectively. The observed changes in the nature of the M-H loop and in coercivity could be explained following the Stoner-Wohlfarth model and using the fact that the domain size reduces as the diameter of the wires increases.

Electron-hole interference in graphene

Bulletin of the American …, 2011

The crystal symmetry of graphene gives rise to massless Dirac low-energy quasiparticles which are... more

Superconducting transition in narrow aluminum strips

APS Meeting …, 2010

We have studied the superconducting transition in highly conducting granular aluminum strips. The... more

Agricultural Consumption Culture and Ecological Transformation:Bangladesh Perspective

Asian Development Policy Review, 2017

The paper mainly focuses the poor consumption culture and its adverse impact on environmental ser... more The paper mainly focuses the poor consumption culture and its adverse impact on environmental services. It is found the study that social regulation, values, choice and habits of Bangladesh people remain in a traditional and poor standard that cannot foster individual life as well as the socio-ecological aspects. Indiscriminate and excessive use of agro-inputs (fertilizer, insecticides, energy, and water) causes fatal risks to agronatural resources. In addition, aquatic and livestock resources are gradually being depleted and exploited through consumption and production in unsustainable or poor sustainable way. The paper is written based on the content analysis in a qualitative approach. The documents of national and international government and nongovernment offices, journal articles, media report, book etc. have critically been reviewed for data collection. Mainly secondary data has been used in the study, but the empirical observation is applied herein as a primary data source also. A social movement is to be introduced within the entire stakeholder around Bangladesh. Yet, mass media, civil society, intellectuals and policy makers have to come forward to launch the movement so that the peasant community can be regulated by morals, values, principles to eradicate bad agricultural consumption and production towards sustainable development. Contribution/ Originality: The study is one of very few studies which have investigated the farmers" poor agricultural consumption pattern that stimulates them over-use of chemical inputs into their agro framings that causes serious risks to agro ecology. The paper"s primary contribution is finding that poor consumption culture derives from traditional agro habits, lack of education, training, and rented land farming.

Sub-50 Nanometer Self-Assembled Nanotextures for Enhanced Broadband Antireflection in Silicon Solar Cells

Nature Communications

Materials providing broadband light antireflection have applications as highly transparent window... more Materials providing broadband light antireflection have applications as highly transparent window coatings, military camouflage, and coatings for efficiently coupling light into solar cells and out of light emitting diodes. In this work, densely packed silicon nanotextures with feature sizes smaller than 50 nanometers enhance the broadband antireflection compared to that predicted by their geometry alone. A significant fraction of the nanotexture volume comprises a surface layer whose optical properties differ substantially from those of the bulk, providing the key to improved performance. The nanotexture reflectivity is quantitatively well modeled after accounting for both its profile and changes in refractive index at the surface. We employ block copolymer self assembly for precise and tunable nanotexture design in the range of ~10 to 70 nanometers across macroscopic solar cell areas. Implementing this efficient antireflection approach in crystalline silicon solar cells significan...

Observation of angle-dependent transmission of Dirac electrons in graphene hetero junctions

Asymmetric scattering of Dirac electrons and holes in graphene

Collapse and Reversibility of the Superhydrophobic State on Nanotextured Surfaces

Physical Review Letters, 2014

Superhydrophobic coatings repel liquids by trapping air inside microscopic surface textures. Howe... more Superhydrophobic coatings repel liquids by trapping air inside microscopic surface textures. However, the resulting composite interface is prone to collapse under external pressure. Nanometer-size textures should facilitate more resilient coatings owing to geometry and confinement effects at the nanoscale. Here, we use in situ x-ray diffraction to study the collapse of the superhydrophobic state in arrays of ≈20 nm-wide silicon textures with cylindrical, conical, and linear features defined by block-copolymer self-assembly and plasma etching. We reveal that the superhydrophobic state vanishes above critical pressures which depend on texture shape and size. This phenomenon is irreversible for all but the conical surface textures which exhibit a spontaneous, partial reappearance of the trapped gas phase upon liquid depressurization. This process is influenced by the kinetics of gas-liquid exchange.

Sub-50-nm self-assembled nanotextures for enhanced broadband antireflection in silicon solar cells

Nature Communications, 2015

Materials providing broadband light antireflection have applications as highly transparent window... more Materials providing broadband light antireflection have applications as highly transparent window coatings, military camouflage, and coatings for efficiently coupling light into solar cells and out of light-emitting diodes. In this work, densely packed silicon nanotextures with feature sizes smaller than 50 nm enhance the broadband antireflection compared with that predicted by their geometry alone. A significant fraction of the nanotexture volume comprises a surface layer whose optical properties differ substantially from those of the bulk, providing the key to improved performance. The nanotexture reflectivity is quantitatively well-modelled after accounting for both its profile and changes in refractive index at the surface. We employ block copolymer self-assembly for precise and tunable nanotexture design in the range of B10-70 nm across macroscopic solar cell areas. Implementing this efficient antireflection approach in crystalline silicon solar cells significantly betters the performance gain compared with an optimized, planar antireflection coating.

Quantum Noise and Asymmetric Scattering of Electrons and Holes in Graphene

Nano Letters, 2014

We present measurements of quantum interference noise in double-gated single layer graphene devic... more We present measurements of quantum interference noise in double-gated single layer graphene devices at low temperatures. The noise characteristics show a nonmonotonic dependence on carrier density, which is related to the interplay between charge inhomogeneity and different scattering mechanisms. Linearly increasing 1/f noise at low carrier densities coincides with the observation of weak localization, suggesting the importance of short-range disorder in this regime. Using perpendicular and parallel p−n junctions, we find that the observed asymmetry of the noise with respect to the Dirac point can be related to asymmetric scattering of electrons and holes on the disorder potential.

Study of cyclic hot corrosion of nanostructured Cr/Co–Al coatings on superalloy

Materials Chemistry and Physics, 2011

Nanostructured Cr/Co-Al coatings were deposited on Superni-718 substrate by DC/RF magnetron sputt... more Nanostructured Cr/Co-Al coatings were deposited on Superni-718 substrate by DC/RF magnetron sputtering in the present work. Hot corrosion studies were conducted on bare substrate and the Cr/Co-Al coated Superni-718 after exposure to a molten salt environment of Na 2 SO 4-60%V 2 O 5 at 900 • C under cyclic conditions. The weight change measurements were made to calculate the cyclic hot corrosion kinetics of the coatings at 900 • C. The microstructural features of the as deposited coatings were characterized by FE-SEM, AFM and XRD. It was observed that the corrosion rate of Cr/Co-Al coated superalloy is lower than that of the uncoated superalloy due to the formation of continuous, dense, adherent and protective oxide scale over the surface of the coatings. The protective oxide scales are basically the thin layer of Cr 2 O 3 , Al 2 O 3 , and CoCr 2 O 4 which has formed over the Cr/Co-Al coated superalloy substrate exposed to molten salt environment at temperature, 900 • C.

Prevalence and Associated Risk Factors of Myiasis in Different Areas of Chittagong, Bangladesh

Research Journal for Veterinary Practitioners, 2014

A One year eventual study was conducted to detect the prevalence and feasible risk factors of myi... more A One year eventual study was conducted to detect the prevalence and feasible risk factors of myiasis in various species of animal in different areas of Chittagong, Bangladesh from March 2012 to February 2013. By Cross-questioning over animal rearers and with clinical examinations myiatic cases were identified and varied risk factors were distinguished. 226 cases were noted manifesting signs of myiasis. Prevalence rates were goat 69% and cattle 22%; wherever seasonal prevalence was explored highest in autumn (55.5%) than cold (11.6%) (p>0.05). Statistically significant difference in the prevalence was reputed with breed, age, sex, wound depthness, temperature and attitude of animal (p ≤0.05). Above 6 months aged animals (75.5%) and cross breeds (34.2%) were mostly infected where females (64.5%) were more prone to myiasis. Foul odorous abscess with wound, breach after delivery, umbilical infection, dirtiness, fecal and urine contamination, bed sore were the most habitual risk factors, though findings were not significant (p >0.05). Most exposed sites were vagina and perineal region, inter digital space, tail, brisket, navel, scrotum, inguinal region and gum. The study has remarked probable health hazards caused by flies in animal that will promote animal rearers in avoiding and clinically managing them. Additional widespread studies are suggested as molecular identification of species of flies and economic analysis caused by myiasis.

Anomalous noise characteristics in graphene pn junctions

Bulletin of the American Physical …, 2012

Graphene pn junctions provide an interesting platform to study the Dirac nature of charge carrier... more

Transmission of phase information between electrons and holes in graphene

Physical Review B, 2013

We have studied quantum interference between electrons and holes in a split-ring gold interferome... more We have studied quantum interference between electrons and holes in a split-ring gold interferometer with graphene arms, one of which contained a pn junction. The carrier type, the pn junction and the phase of the oscillations in a magnetic field were controlled by a top gate placed over one of the arms. We observe clear Aharonov-Bohm oscillations at the Dirac point and away from it, regardless of the carrier type in each arm. We also find clear oscillations when one arm of the interferometer contains a single pn junction, allowing us to study the interplay of Aharonov-Bohm effect and Klein tunneling.

Observation of charge density wave characteristics in conducting polymer nanowires: Possibility of Wigner crystallization

Physical Review B, 2007

We have presented here results of a low temperature transport study of polypyrrole nanowires havi... more We have presented here results of a low temperature transport study of polypyrrole nanowires having low electron densities, which shows characteristics of charge density waves observed in structurally ordered materials. The current-voltage characteristics of all these nanowires show a power-law dependence on voltage and temperature and a "gap" that decreases rapidly as the temperature is increased, confirming the existence of a long-range electron-electron interaction in the nanowires. A switching transition to highly conducting state has been observed above a threshold voltage, which can be tuned by changing the diameters of the nanowires and the temperature. Negative differential resistance and enhancement of noise have been observed above the threshold. These experimental results give evidence in favor of Wigner crystallization in these nanowires.

Processing and characterisation of nanostructured Al doped ZnO antireflection films

Materials Technology: Advanced Performance Materials, 2013

Al doped ZnO films (3 at-%) were developed on soda lime glass substrate by electroless deposition... more Al doped ZnO films (3 at-%) were developed on soda lime glass substrate by electroless deposition. The films were characterised by X-ray diffraction (XRD), field scanning electron microscope (FESEM/EDS), atomic force microscope (AFM) and UV visible spectrophotometer. Xray diffraction analysis indicates that preferential growth of the films are (101) reflection peak in the 400, 500 and 600uC annealed films. FESEM surface and cross-section analysis exhibit that Al doped ZnO film has dense and compact grains as compared to undoped ZnO film. Film is composed of Zn, Al and O is confirmed by EDS analysis. Surface roughness of the film is determined by AFM. The Al doped ZnO films exhibit excellent optical transmittance (more than 80%) and minimum absorbance spectra in visible range 400-800 nm wavelength. Al doped ZnO film annealed at 500uC is suitable for antireflection coating in silicon solar cell.

High temperature oxidation behavior of nanostructured Ni–Al coatings on superalloy

Journal of Alloys and Compounds, 2009

The high temperature oxidation behavior of magnetron sputtered Ni-Al coatings on the superalloy s... more The high temperature oxidation behavior of magnetron sputtered Ni-Al coatings on the superalloy substrate has been studied in the present work. The microstructural and morphological features of Ni-Al coatings were characterized by FE-SEM, AFM and XRD. Thermo gravimetric technique was used to investigate the oxidation behavior of the coatings, in air at 900 • C. The growth kinetics of oxide layers was predicted from the weight changes of the coating samples measured during oxidation. It was found that the corrosion rate of nanostructured Ni-Al coated superalloy was lower than that of the uncoated superalloy due to the formation of continuous, dense, adherent and protective oxide scale over the surface of the coatings. The morphological features and phases of the corroded coatings were used to elucidate the mechanism of high temperature oxidation. A continuous thin layer of protective oxide films such as NiO and Al 2 O 3 has formed over the Ni-Al coatings exposed to air at high temperature, 900 • C.

Anomalous effect of biased oscillating field on the switching behaviour: Modulating friction of charge carriers in nanowires

EPL (Europhysics Letters), 2009

... Rev. B, 73 (2006) 125313. [7] Rahman A., Sanyal MK, Gangopadhayy R. and De A., Chem. Phys. Le... more

Enhancement of electron–electron interactions in chemically synthesized polymer nanowires

Chemical Physics Letters, 2007

We report here a comparison of electronic transport properties of conducting polymer nanowires sy... more We report here a comparison of electronic transport properties of conducting polymer nanowires synthesized by chemical and electrochemical methods inside nanopores. Electronic transport properties of these nanowires show a power-law behavior (I µ V 1+b) at low temperature. Chemically synthesized nanowires exhibit higher values of b and these values increase further with the diameter of nanowires. Zero bias differential conductance of all the nanowires increase with increasing diameter and temperature but the obtained values of chemically synthesized nanowires were always found to be much lower. These results indicate enhancement of electron-electron interactions in chemically synthesized nanowires.

Negative capacitance in Wigner crystal forming polymer nanowires

Applied Physics Letters, 2009

Negative capacitance has been observed in conducting polymer nanowires. These nanowires exhibit f... more Negative capacitance has been observed in conducting polymer nanowires. These nanowires exhibit features of one-dimensional Wigner crystals, such as switching transition that reduces resistance by several orders of magnitude, negative differential resistance, and enhancement of noise in the switched state. Negative capacitance is theoretically predicted characteristic feature of a Wigner crystal. The magnitude of negative capacitance increases with increasing bias voltage below the switching transition. Above switching transition the magnitude decreases with increasing current bias. The capacitance goes from negative to positive value as the features of Wigner crystal state disappear with increasing temperature.

Diameter-dependent coercivity of cobalt nanowires

Applied Physics A, 2013

We show that the coercivity of electrochemically grown cobalt nanowires (NWs) within the pores of... more We show that the coercivity of electrochemically grown cobalt nanowires (NWs) within the pores of a polycarbonate membrane can be changed to a large extent by tuning their diameters. The face centered cubic crystalline structure of the NWs having diameter in the range of 10 to 200 nm could be retained. Smaller diameter wires (below 30 nm) are found to be single crystalline and oriented in the [110] growth direction, but for higher diameter wires the crystallite size became very small. Magnetization measurements with an applied field parallel to the axis of the NWs show that the nature of the M-H loop changes from square to linear as the diameter of the NWs increases. The coercivity was found to be 1700 Oe and 480 Oe at 5 K (1000 Oe and 250 Oe at 300 K) for 10 nm and 100 nm wires, respectively. The observed changes in the nature of the M-H loop and in coercivity could be explained following the Stoner-Wohlfarth model and using the fact that the domain size reduces as the diameter of the wires increases.

Electron-hole interference in graphene

Bulletin of the American …, 2011

The crystal symmetry of graphene gives rise to massless Dirac low-energy quasiparticles which are... more

Superconducting transition in narrow aluminum strips

APS Meeting …, 2010

We have studied the superconducting transition in highly conducting granular aluminum strips. The... more