Javed Akhter - Academia.edu (original) (raw)
Papers by Javed Akhter
Journal of Nuclear Materials, 2003
Diffusion bonding of stainless steel to Zircaloy-4 in the presence of Ta as interlayer has been i... more Diffusion bonding of stainless steel to Zircaloy-4 in the presence of Ta as interlayer has been investigated using diffusion couples heat treated at 1150°C under vacuum for 3 h. Different types of regions have been observed in stainless steel, Zircaloy-4 and Ta foil. A Cr rich layer formed in stainless steel is found to act as a diffusion barrier. A region observed with the Ta foil in Zircaloy-4 is rich in Cr, Ta, Fe and Zr while two zones are formed in Zircaoly-4 containing Zr, Ta, Cr, Fe and Ni. The zone rich in Zr gives black contrast and the other zone gives grey contrast and these are identified as eutectic phases of the type TaCr 2-Liq.-b-Zr and Ta(Cr,Fe) 2-Liq.-b-Zr.
Journal of Nuclear Materials, 2002
Electron beam welded joints between Zircaloy-4 and stainless steel 304L are investigated due to t... more Electron beam welded joints between Zircaloy-4 and stainless steel 304L are investigated due to their importance in the nuclear industry. The molten and heat affected zones (HAZs) are found to be free of defects. Diffusion of Fe, Cr and Ni is observed in Zircaloy-4 near the molten zone and of Zr and Sn in the stainless steel. A rod-shaped intermetallic compound Zr(Cr,Fe) 2 and eutectic phases ZrCr 2-liquid (Zr,Fe) and Zr 2 Fe-Zr 2 Ni are present in the molten zone. The hardness of the molten zone, containing Zr(Cr,Fe) 2; is much higher than the rest of the molten zone and the HAZs.
Applied Surface Science, 2009
Computational Materials Science, 2004
Molecular dynamics simulations have been applied to investigate thermal properties of Ag and Au. ... more Molecular dynamics simulations have been applied to investigate thermal properties of Ag and Au. Semi-empirical potentials, based on the embedded atom method (EAM) have been employed to calculate lattice parameter, energy per atom, mean square displacements and radial distribution function for the two metals. Thermal properties like specific heat, thermal coefficient of linear expansion and melting temperature are deduced from
Annals of Microbiology, 2010
Zerovalent copper nanoparticles (Cu 0) of 12 nm size were synthesized using an inert gas condensa... more Zerovalent copper nanoparticles (Cu 0) of 12 nm size were synthesized using an inert gas condensation method in which bulk copper metal was evaporated into an inert environment of argon with subsequent cooling for nucleation and growth of nanoparticles. Crystalline structure, morphology and estimation of size of nanoparticles were carried out by X-ray diffraction and transmission electron microscopy. The antibacterial activity of these nanoparticles against the Gram-negative bacterium Escherichia coli was assessed in liquid as well as solid growth media. It was observed from scanning electron microscopic analysis that the interaction of copper nanoparticles with E. coli resulted in the formation of cavities/pits in the bacterial cell wall. The antibacterial property of copper nanoparticles was attributed mainly to adhesion with bacteria because of their opposite electrical charges, resulting in a reduction reaction at the bacterial cell wall. Nanoparticles with a larger surface-to-volume ratio provide more efficient means for antibacterial activity.
Annals of Microbiology, 2008
The present study describes the isolation of bacteria from soil with the ability to degrade plast... more The present study describes the isolation of bacteria from soil with the ability to degrade plastic polyurethane (PU). Bacterial strains attached on the polyurethane film, after soil burial for 6 months, were isolated and identified as Bacillus sp. AF8, Pseudomonas sp AF9, Micrococcus sp. 10, Arthrobacter sp. AF11, and Corynebacterium sp. AF12. In plate assay, zones of hydrolysis were visualised around the bacterial colonies on mineral salt agar plates containing polyurethane as a sole carbon source. The results of the Sturm test for degradability showed more CO 2 production in the test than in control. The production of esterase was detected in the presence of polyurethane as a substrate. The Scanning Electron Microscopy and Fourier Transform Infrared Spectroscopy showed certain changes on the surface of PU film and formation of some new intermediate products after polymer breakdown.
Electron beam (EB) surface melting technique is becoming popular in nuclear, chemical and aerospa... more Electron beam (EB) surface melting technique is becoming popular in nuclear, chemical and aerospace industries due to its large penetration depth and high cooling rate. Supercooling of the localized area helps to achieve non-equilibrium phases as well as a fine microstructure. EB surface melting of Zircaloy-4, containing SiC, is carried out to improve the surface melting temperature, thermal stability and erosion resistance. The resulted microstructure and non-equilibrium phases are characterized by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Zircaloy-4 is successfully surface hardened by EB melting. The surface hardening can be attributed to both Zr-rich silicides as well as the small size secondary SiC present in the matrix. During EB melting the SiC dissociated partially and interacted with the liquid Zr and resulted in different non-equilibrium phases of Zr-rich silicides during solidification.
IEEE Transactions on Nanotechnology, 2000
Cobalt nanowires were fabricated by alternating current electrodeposition using anodic porous alu... more Cobalt nanowires were fabricated by alternating current electrodeposition using anodic porous alumina template. Diameter of the pores was controlled by the pore widening time. Effect of pore widening time on the magnetic properties and microstructure of the nanowires was investigated. High-resolution scanning transmission electron microscopy was used to study the morphology of the pores as well as nanowires. Magnetic properties were measured by vibrating sample magnetometer at room temperature, and were found to be size-dependent. When the field was applied parallel to the nanowires, coercivity of the nanowires reaches to the maximum value ∼2200 Oe for 10 min pore widening time. Coercivity decreases linearly with further increase in the pore widening time. In the case, when the field was applied perpendicular to the nanowires, coercivity was found to decrease monotonically when the pore widening time was increased from 0 to 10 min.
Journal of Nuclear Materials, 2003
Diffusion bonding of stainless steel to Zircaloy-4 in the presence of Ta as interlayer has been i... more Diffusion bonding of stainless steel to Zircaloy-4 in the presence of Ta as interlayer has been investigated using diffusion couples heat treated at 1150°C under vacuum for 3 h. Different types of regions have been observed in stainless steel, Zircaloy-4 and Ta foil. A Cr rich layer formed in stainless steel is found to act as a diffusion barrier. A region observed with the Ta foil in Zircaloy-4 is rich in Cr, Ta, Fe and Zr while two zones are formed in Zircaoly-4 containing Zr, Ta, Cr, Fe and Ni. The zone rich in Zr gives black contrast and the other zone gives grey contrast and these are identified as eutectic phases of the type TaCr 2 -Liq.-b-Zr and Ta(Cr,Fe) 2 -Liq.-b-Zr.
Journal of Nuclear Materials, 2002
Electron beam welded joints between Zircaloy-4 and stainless steel 304L are investigated due to t... more Electron beam welded joints between Zircaloy-4 and stainless steel 304L are investigated due to their importance in the nuclear industry. The molten and heat affected zones (HAZs) are found to be free of defects. Diffusion of Fe, Cr and Ni is observed in Zircaloy-4 near the molten zone and of Zr and Sn in the stainless steel. A rod-shaped intermetallic compound Zr(Cr,Fe) 2 and eutectic phases ZrCr 2 -liquid (Zr,Fe) and Zr 2 Fe-Zr 2 Ni are present in the molten zone. The hardness of the molten zone, containing Zr(Cr,Fe) 2; is much higher than the rest of the molten zone and the HAZs. Ó (J.I. Akhter). 0022-3115/02/$ -see front matter Ó 2002 Elsevier Science B.V. All rights reserved. PII: S 0 0 2 2 -3 1 1 5 ( 0 1 ) 0 0 7 5 7 -7
Micron, 2010
A simple approach for the growth of long-range highly ordered nanoporous anodic alumina film in H... more A simple approach for the growth of long-range highly ordered nanoporous anodic alumina film in H(2)SO(4) electrolyte through a single step anodization without any additional pre-anodizing procedure is reported. Free-standing porous anodic alumina film of 180 microm thickness with through hole morphology was obtained. A simple and single step process was used for the detachment of alumina from aluminum substrate. The effect of anodizing conditions, such as anodizing voltage and time on the pore diameter and pore ordering is discussed. The metal/oxide and oxide/electrolyte interfaces were examined by high resolution scanning transmission electron microscope. The arrangement of pores on metal/oxide interface was well ordered with smaller diameters than that of the oxide/electrolyte interface. The inter-pore distance was larger in metal/oxide interface as compared to the oxide/electrolyte interface. The size of the ordered domain was found to depend strongly upon anodizing voltage and time.
Materials Letters, 2003
Mechanical alloying (MA) is a versatile technique to produce nanocrystalline and amorphous alloys... more Mechanical alloying (MA) is a versatile technique to produce nanocrystalline and amorphous alloys. Its special advantage is to form alloys of immiscible elements. High energy planetary ball milling has been used to produce Al -2 wt.% Ge alloy. Powders of Al (1 -125 Am) and Ge (0.5 -2 Am) were milled together with a powder to ball weight ratio of 1:20 up to 400 h. The size and shape of the elemental and alloy powder particles were examined in a scanning electron microscope (SEM) while their microanalysis was performed by energy dispersive system (EDS) attached with SEM. It has been observed that 300 h of milling produces homogeneous alloy. X-ray diffraction (XRD) patterns confirm complete alloying of Ge with Al. As the size of the atoms of Al and Ge are different, elastic strain energy because of misfit has been calculated to be about 2.6 kcal/mol. It has been concluded that among the factors contributing towards the enthalpy, stress exerted by dislocations on solute atoms is the major driving force for alloying. D
Computational Materials Science, 2004
Molecular dynamics simulations have been applied to investigate thermal properties of Ag and Au. ... more Molecular dynamics simulations have been applied to investigate thermal properties of Ag and Au. Semi-empirical potentials, based on the embedded atom method (EAM) have been employed to calculate lattice parameter, energy per atom, mean square displacements and radial distribution function for the two metals. Thermal properties like specific heat, thermal coefficient of linear expansion and melting temperature are deduced from
Applied Surface Science, 2009
Journal of Alloys and Compounds, 2008
... [2] E. Campo and V. Lupinc, Metall. Sci Tech. II (1993), p. 31. [3] M. Ahmad, JI Akhtar, MA S... more ... [2] E. Campo and V. Lupinc, Metall. Sci Tech. II (1993), p. 31. [3] M. Ahmad, JI Akhtar, MA Shaikh, M. Akhtar, M. Iqbal, E. Ahmad and MA Chudhry, J. Nucl. Mater. 317 (2003), p. 212. Article | PDF (249 K) | View Record in Scopus | Cited By in Scopus (9). [4] SL Sobolev, Phys. Rev. ...
Journal of Nuclear Materials, 2005
Electron beam welding (EBW) of Zircaloy-4 and Al-Fe-Ce alloys is carried out to investigate the m... more Electron beam welding (EBW) of Zircaloy-4 and Al-Fe-Ce alloys is carried out to investigate the microstructure and non-equilibrium phases produced in the molten zone (MZ). Scanning electron microscopy (SEM) with an energy dispersive system (EDS) attachment and X-ray diffraction (XRD) are used to characterize the microstructural and compositional changes and phases. Five distinct regions containing various phases are observed in the MZ. Hot cracking is observed in the region containing AlZr 2 and Al 2 Zr 3 intermetallic compounds.
Journal of Alloys and Compounds, 2005
Microstructure of the diffusion bonded samples of stainless steel 316L and Zircaloy-4 in the pres... more Microstructure of the diffusion bonded samples of stainless steel 316L and Zircaloy-4 in the presence of Ti interlayer at 1000 • C and 1050 • C is investigated by scanning electron microscopy (SEM) and the phases in the diffusion zone (DZ) have been analyzed by energy dispersive system (EDS) attached with SEM. Five distinct regions have been observed in the sample bonded at 1000 • C due to the diffusion of various elements from both stainless steel and Zircaloy-4. Local melting and formation of dendritic structure occurred in the sample bonded at 1050 • C. Dendritic structure is achieved, which hinders cracking during solidification in the DZ.
Materials Letters, 2007
... experimental phase of this work. Thanks are also due to Mr. Gohar Dad and Mr. Abdal Ahmad for... more ... experimental phase of this work. Thanks are also due to Mr. Gohar Dad and Mr. Abdal Ahmad for providing the EB facility. We are very grateful to Mr. M. Asim Rashid for helping in literature requirements. We do not forget to ...
Journal of Nuclear Materials, 2003
Diffusion bonding of stainless steel to Zircaloy-4 in the presence of Ta as interlayer has been i... more Diffusion bonding of stainless steel to Zircaloy-4 in the presence of Ta as interlayer has been investigated using diffusion couples heat treated at 1150°C under vacuum for 3 h. Different types of regions have been observed in stainless steel, Zircaloy-4 and Ta foil. A Cr rich layer formed in stainless steel is found to act as a diffusion barrier. A region observed with the Ta foil in Zircaloy-4 is rich in Cr, Ta, Fe and Zr while two zones are formed in Zircaoly-4 containing Zr, Ta, Cr, Fe and Ni. The zone rich in Zr gives black contrast and the other zone gives grey contrast and these are identified as eutectic phases of the type TaCr 2-Liq.-b-Zr and Ta(Cr,Fe) 2-Liq.-b-Zr.
Journal of Nuclear Materials, 2002
Electron beam welded joints between Zircaloy-4 and stainless steel 304L are investigated due to t... more Electron beam welded joints between Zircaloy-4 and stainless steel 304L are investigated due to their importance in the nuclear industry. The molten and heat affected zones (HAZs) are found to be free of defects. Diffusion of Fe, Cr and Ni is observed in Zircaloy-4 near the molten zone and of Zr and Sn in the stainless steel. A rod-shaped intermetallic compound Zr(Cr,Fe) 2 and eutectic phases ZrCr 2-liquid (Zr,Fe) and Zr 2 Fe-Zr 2 Ni are present in the molten zone. The hardness of the molten zone, containing Zr(Cr,Fe) 2; is much higher than the rest of the molten zone and the HAZs.
Applied Surface Science, 2009
Computational Materials Science, 2004
Molecular dynamics simulations have been applied to investigate thermal properties of Ag and Au. ... more Molecular dynamics simulations have been applied to investigate thermal properties of Ag and Au. Semi-empirical potentials, based on the embedded atom method (EAM) have been employed to calculate lattice parameter, energy per atom, mean square displacements and radial distribution function for the two metals. Thermal properties like specific heat, thermal coefficient of linear expansion and melting temperature are deduced from
Annals of Microbiology, 2010
Zerovalent copper nanoparticles (Cu 0) of 12 nm size were synthesized using an inert gas condensa... more Zerovalent copper nanoparticles (Cu 0) of 12 nm size were synthesized using an inert gas condensation method in which bulk copper metal was evaporated into an inert environment of argon with subsequent cooling for nucleation and growth of nanoparticles. Crystalline structure, morphology and estimation of size of nanoparticles were carried out by X-ray diffraction and transmission electron microscopy. The antibacterial activity of these nanoparticles against the Gram-negative bacterium Escherichia coli was assessed in liquid as well as solid growth media. It was observed from scanning electron microscopic analysis that the interaction of copper nanoparticles with E. coli resulted in the formation of cavities/pits in the bacterial cell wall. The antibacterial property of copper nanoparticles was attributed mainly to adhesion with bacteria because of their opposite electrical charges, resulting in a reduction reaction at the bacterial cell wall. Nanoparticles with a larger surface-to-volume ratio provide more efficient means for antibacterial activity.
Annals of Microbiology, 2008
The present study describes the isolation of bacteria from soil with the ability to degrade plast... more The present study describes the isolation of bacteria from soil with the ability to degrade plastic polyurethane (PU). Bacterial strains attached on the polyurethane film, after soil burial for 6 months, were isolated and identified as Bacillus sp. AF8, Pseudomonas sp AF9, Micrococcus sp. 10, Arthrobacter sp. AF11, and Corynebacterium sp. AF12. In plate assay, zones of hydrolysis were visualised around the bacterial colonies on mineral salt agar plates containing polyurethane as a sole carbon source. The results of the Sturm test for degradability showed more CO 2 production in the test than in control. The production of esterase was detected in the presence of polyurethane as a substrate. The Scanning Electron Microscopy and Fourier Transform Infrared Spectroscopy showed certain changes on the surface of PU film and formation of some new intermediate products after polymer breakdown.
Electron beam (EB) surface melting technique is becoming popular in nuclear, chemical and aerospa... more Electron beam (EB) surface melting technique is becoming popular in nuclear, chemical and aerospace industries due to its large penetration depth and high cooling rate. Supercooling of the localized area helps to achieve non-equilibrium phases as well as a fine microstructure. EB surface melting of Zircaloy-4, containing SiC, is carried out to improve the surface melting temperature, thermal stability and erosion resistance. The resulted microstructure and non-equilibrium phases are characterized by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Zircaloy-4 is successfully surface hardened by EB melting. The surface hardening can be attributed to both Zr-rich silicides as well as the small size secondary SiC present in the matrix. During EB melting the SiC dissociated partially and interacted with the liquid Zr and resulted in different non-equilibrium phases of Zr-rich silicides during solidification.
IEEE Transactions on Nanotechnology, 2000
Cobalt nanowires were fabricated by alternating current electrodeposition using anodic porous alu... more Cobalt nanowires were fabricated by alternating current electrodeposition using anodic porous alumina template. Diameter of the pores was controlled by the pore widening time. Effect of pore widening time on the magnetic properties and microstructure of the nanowires was investigated. High-resolution scanning transmission electron microscopy was used to study the morphology of the pores as well as nanowires. Magnetic properties were measured by vibrating sample magnetometer at room temperature, and were found to be size-dependent. When the field was applied parallel to the nanowires, coercivity of the nanowires reaches to the maximum value ∼2200 Oe for 10 min pore widening time. Coercivity decreases linearly with further increase in the pore widening time. In the case, when the field was applied perpendicular to the nanowires, coercivity was found to decrease monotonically when the pore widening time was increased from 0 to 10 min.
Journal of Nuclear Materials, 2003
Diffusion bonding of stainless steel to Zircaloy-4 in the presence of Ta as interlayer has been i... more Diffusion bonding of stainless steel to Zircaloy-4 in the presence of Ta as interlayer has been investigated using diffusion couples heat treated at 1150°C under vacuum for 3 h. Different types of regions have been observed in stainless steel, Zircaloy-4 and Ta foil. A Cr rich layer formed in stainless steel is found to act as a diffusion barrier. A region observed with the Ta foil in Zircaloy-4 is rich in Cr, Ta, Fe and Zr while two zones are formed in Zircaoly-4 containing Zr, Ta, Cr, Fe and Ni. The zone rich in Zr gives black contrast and the other zone gives grey contrast and these are identified as eutectic phases of the type TaCr 2 -Liq.-b-Zr and Ta(Cr,Fe) 2 -Liq.-b-Zr.
Journal of Nuclear Materials, 2002
Electron beam welded joints between Zircaloy-4 and stainless steel 304L are investigated due to t... more Electron beam welded joints between Zircaloy-4 and stainless steel 304L are investigated due to their importance in the nuclear industry. The molten and heat affected zones (HAZs) are found to be free of defects. Diffusion of Fe, Cr and Ni is observed in Zircaloy-4 near the molten zone and of Zr and Sn in the stainless steel. A rod-shaped intermetallic compound Zr(Cr,Fe) 2 and eutectic phases ZrCr 2 -liquid (Zr,Fe) and Zr 2 Fe-Zr 2 Ni are present in the molten zone. The hardness of the molten zone, containing Zr(Cr,Fe) 2; is much higher than the rest of the molten zone and the HAZs. Ó (J.I. Akhter). 0022-3115/02/$ -see front matter Ó 2002 Elsevier Science B.V. All rights reserved. PII: S 0 0 2 2 -3 1 1 5 ( 0 1 ) 0 0 7 5 7 -7
Micron, 2010
A simple approach for the growth of long-range highly ordered nanoporous anodic alumina film in H... more A simple approach for the growth of long-range highly ordered nanoporous anodic alumina film in H(2)SO(4) electrolyte through a single step anodization without any additional pre-anodizing procedure is reported. Free-standing porous anodic alumina film of 180 microm thickness with through hole morphology was obtained. A simple and single step process was used for the detachment of alumina from aluminum substrate. The effect of anodizing conditions, such as anodizing voltage and time on the pore diameter and pore ordering is discussed. The metal/oxide and oxide/electrolyte interfaces were examined by high resolution scanning transmission electron microscope. The arrangement of pores on metal/oxide interface was well ordered with smaller diameters than that of the oxide/electrolyte interface. The inter-pore distance was larger in metal/oxide interface as compared to the oxide/electrolyte interface. The size of the ordered domain was found to depend strongly upon anodizing voltage and time.
Materials Letters, 2003
Mechanical alloying (MA) is a versatile technique to produce nanocrystalline and amorphous alloys... more Mechanical alloying (MA) is a versatile technique to produce nanocrystalline and amorphous alloys. Its special advantage is to form alloys of immiscible elements. High energy planetary ball milling has been used to produce Al -2 wt.% Ge alloy. Powders of Al (1 -125 Am) and Ge (0.5 -2 Am) were milled together with a powder to ball weight ratio of 1:20 up to 400 h. The size and shape of the elemental and alloy powder particles were examined in a scanning electron microscope (SEM) while their microanalysis was performed by energy dispersive system (EDS) attached with SEM. It has been observed that 300 h of milling produces homogeneous alloy. X-ray diffraction (XRD) patterns confirm complete alloying of Ge with Al. As the size of the atoms of Al and Ge are different, elastic strain energy because of misfit has been calculated to be about 2.6 kcal/mol. It has been concluded that among the factors contributing towards the enthalpy, stress exerted by dislocations on solute atoms is the major driving force for alloying. D
Computational Materials Science, 2004
Molecular dynamics simulations have been applied to investigate thermal properties of Ag and Au. ... more Molecular dynamics simulations have been applied to investigate thermal properties of Ag and Au. Semi-empirical potentials, based on the embedded atom method (EAM) have been employed to calculate lattice parameter, energy per atom, mean square displacements and radial distribution function for the two metals. Thermal properties like specific heat, thermal coefficient of linear expansion and melting temperature are deduced from
Applied Surface Science, 2009
Journal of Alloys and Compounds, 2008
... [2] E. Campo and V. Lupinc, Metall. Sci Tech. II (1993), p. 31. [3] M. Ahmad, JI Akhtar, MA S... more ... [2] E. Campo and V. Lupinc, Metall. Sci Tech. II (1993), p. 31. [3] M. Ahmad, JI Akhtar, MA Shaikh, M. Akhtar, M. Iqbal, E. Ahmad and MA Chudhry, J. Nucl. Mater. 317 (2003), p. 212. Article | PDF (249 K) | View Record in Scopus | Cited By in Scopus (9). [4] SL Sobolev, Phys. Rev. ...
Journal of Nuclear Materials, 2005
Electron beam welding (EBW) of Zircaloy-4 and Al-Fe-Ce alloys is carried out to investigate the m... more Electron beam welding (EBW) of Zircaloy-4 and Al-Fe-Ce alloys is carried out to investigate the microstructure and non-equilibrium phases produced in the molten zone (MZ). Scanning electron microscopy (SEM) with an energy dispersive system (EDS) attachment and X-ray diffraction (XRD) are used to characterize the microstructural and compositional changes and phases. Five distinct regions containing various phases are observed in the MZ. Hot cracking is observed in the region containing AlZr 2 and Al 2 Zr 3 intermetallic compounds.
Journal of Alloys and Compounds, 2005
Microstructure of the diffusion bonded samples of stainless steel 316L and Zircaloy-4 in the pres... more Microstructure of the diffusion bonded samples of stainless steel 316L and Zircaloy-4 in the presence of Ti interlayer at 1000 • C and 1050 • C is investigated by scanning electron microscopy (SEM) and the phases in the diffusion zone (DZ) have been analyzed by energy dispersive system (EDS) attached with SEM. Five distinct regions have been observed in the sample bonded at 1000 • C due to the diffusion of various elements from both stainless steel and Zircaloy-4. Local melting and formation of dendritic structure occurred in the sample bonded at 1050 • C. Dendritic structure is achieved, which hinders cracking during solidification in the DZ.
Materials Letters, 2007
... experimental phase of this work. Thanks are also due to Mr. Gohar Dad and Mr. Abdal Ahmad for... more ... experimental phase of this work. Thanks are also due to Mr. Gohar Dad and Mr. Abdal Ahmad for providing the EB facility. We are very grateful to Mr. M. Asim Rashid for helping in literature requirements. We do not forget to ...