H. Bhuyan - Academia.edu (original) (raw)

Papers by H. Bhuyan

Research paper thumbnail of Sub-micron size carbon structures synthesized using plasma enhanced CVD, without external heating and no catalyzer action

... [4] GY Chen, V. Stolojan, SRP Silva, H. Herman and S. Haq, Carbon 43 (2005), p. 704. Article ... more ... [4] GY Chen, V. Stolojan, SRP Silva, H. Herman and S. Haq, Carbon 43 (2005), p. 704. Article | PDF (263 K) | View Record in Scopus | Cited By in Scopus (19). [5] I. Denysenko, J. Berndt, E. Kovacevic and I. Stefanovic, Phys. Plasmas 13 (2006), p. 073507. ...

Research paper thumbnail of TiN coating on steel by pulsed capillary discharge

Research paper thumbnail of Surface modification by nitrogen plasma immersion ion implantation into new steel 460Li–21Cr in a capacitively coupled radio frequency discharge

Applied Surface Science, 2014

ABSTRACT A novel steel 460Li–21Cr belonging to a new generation of superferritic grade steel has ... more ABSTRACT A novel steel 460Li–21Cr belonging to a new generation of superferritic grade steel has been implanted with nitrogen in a low power 13.56 MHz radio frequency plasma by the plasma immersion ion implantation (PIII) technique in order to study its physical and chemical properties under different experimental conditions. We observed improved hardness and wear behavior of 460Li–21Cr steel with a layer thickness between 1.5 and 4.0 μm after 60 min implantation in the temperature range from 350 to 550 °C. The modified surface layer containing nitrogen does not show CrN in X-ray diffraction (XRD). Compared to untreated substrates, the hardness can be increased by a factor of 4, depending on the experimental conditions, and the wear behavior was also improved by two orders of magnitude. The results are very similar to those for austenitic stainless steel with a similar pronounced increase in wear resistance and plateau-like nitrogen depth profiles.

Research paper thumbnail of Hollow cathode effects in the pre-breakdown phase of a pulsed capillary discharge

Plasma Sources Science and Technology, 2009

Experimental observations of the hollow cathode effect (HCE) in an open end pulsed capillary disc... more Experimental observations of the hollow cathode effect (HCE) in an open end pulsed capillary discharge (PCD) are presented. In the HCE axial electron beams emitted from a pre-breakdown plasma produced spontaneously in the hollow cathode region (HCR) assist ionization growth in the interelectrode volume. The PCD operates in argon at 0.6-1.4 Torr, ∼10 kV applied voltage. Time resolved spectroscopic measurements, with 15 ns time resolution, are used in conjunction with photomultiplier observations of light emission from the capillary ends, and Faraday cup measurements of axial electron beams, to characterize the pre-and post-breakdown processes in the HCR of the discharge. The HCR emission is found to be dominated by Ar II lines. Comparison between measured and synthetic spectra indicates that the pre-breakdown HCR plasma is characteristic of a collisional low pressure, low density plasma, whereas the post-breakdown HCR plasma, tens of nanoseconds after breakdown, is due to plasma ejection from the capillary volume. Experimental evidence of a zippering effect in post-breakdown capillary plasma heating, due to an initial axial pressure gradient, as predicted by computer simulations, has been found.

Research paper thumbnail of High energy ion beam irradiation on titanium substrate in a pulsed plasma device operating with methane

Journal of Physics D: Applied Physics, 2009

We report the investigation of high energy ion beam irradiation on titanium (Ti) substrates at ro... more We report the investigation of high energy ion beam irradiation on titanium (Ti) substrates at room temperature using a low energy plasma focus (PF) device operating in methane gas. The surface modifications induced by the ion beam using two different anode materials, graphite and copper, are characterized using standard surface science diagnostic tools, such as x-ray diffraction, scanning electron microscopy,

Research paper thumbnail of Rapid synthesis of carbon nanoparticles with an optimized combination of specific surface area and crystallinity by a plasma-assisted single-step process

Journal of Physics D: Applied Physics, 2013

Research paper thumbnail of Measurements of plasma parameters in capacitively coupled radio frequency plasma from discharge characteristics: Correlation with optical emission spectroscopy

Current Applied Physics, 2013

Research paper thumbnail of Effect of ambient gas species on the formation of Cu nanoparticles in wire explosion process

Current Applied Physics, 2012

Research paper thumbnail of Plasma properties of a DC hollow cathode discharge

We have investigated the plasma properties of a Hollow Cathode Discharge (HCD) using different di... more We have investigated the plasma properties of a Hollow Cathode Discharge (HCD) using different dimensions of hollow cathode aperture (1 to 8 mm) in argon operating medium. The diagnostic used to investigate the plasma properties is a tiny Langmuir probe. The diameter and length of the Langmuir probe was chosen such that it draws a measurable current from the plasma causing a minimal perturbation to the surrounding plasma and remains rigid within the plasma as well as the cylindrical probe theories are applicable while calculating the electron temperature and plasma density. The probe was placed perpendicular to the axis of the hollow cathode at a distance of 20 mm from the hollow cathode side. The HCD was operated in the voltage range of 600 to 1000 V and pressures range of 70 to 100 mtorr. We observed that electron temperature and density varies with the operational condition. The estimated electron temperature is less than 10 eV and the temperature is maximum in the range of 3 to 5 mm diameter of the hollow cathode and a pressure range of 75 to 85 mTorr. The calculated maximum density is of the order of 10 10 cm -3 .

Research paper thumbnail of RECUBRIMIENTOS TiN EN ACERO MEDIANTE DESCARGA CAPILAR PULSADA

RESUMEN La geometría característica de una descarga capilar pulsada (PCD)[1] establece condicione... more RESUMEN La geometría característica de una descarga capilar pulsada (PCD)[1] establece condiciones naturales para la formación de jets de plasma, los cuales se expanden en el gas neutro presente en la cámara. Un capacitor de almacenamiento local, coaxial con el capilar, es cargado pulsadamente a un máximo de–10kV, lo que resulta en un pulso de corriente de~ 10ns,~ 2kA. La descarga es operada en Nitrógeno, en un modo pulsado continuo, a una frecuencia de 50 Hz y presiones entre 0.3 y 1 Torr. Se ha investigado el ...

Research paper thumbnail of Formation of carbon nanostructures by the plasma jets emitted from a pulsed capillary discharge at low pressures

We have performed an experimental analysis on the investigation of intense plasma jet irradiation... more We have performed an experimental analysis on the investigation of intense plasma jet irradiation on Si (100) substrates using a repetitive pulsed capillary discharge (PCD) device operating in methane gas at low pressure. The surface modifications induced by the plasma jet are characterized using standard surface science diagnostic tools, such as scanning electron microscopy (SEM), energy-dispersive x-ray (EDX) analysis and Raman spectroscopy (RS) and the results are reported. In particular, it has been found that with ...

Research paper thumbnail of Plasma species dynamics in a laser produced carbon plasma expanding in low pressure neutral gas background

Journal of Physics: Conference Series, 2012

ABSTRACT We present time and space resolved spectroscopic observations of a laser produced carbon... more ABSTRACT We present time and space resolved spectroscopic observations of a laser produced carbon plasma, in an argon background. An Nd:YAG laser pulse, 370 mJ, 3.5 ns, at 1.06 μm, with a fluence of 6.8 J/cm2, is used to produce a plasma from a solid graphite target, at a base pressure of 0.5 mTorr, and with 80 mTorr Argon background. The spectral emission in the visible is recorded with 15 ns time resolution. 20 ns time resolution plasma imagining, filtered at characteristic carbon species emission wavelengths, is used to study the dynamics of the expanding plasma. Two different fronts with ionic or molecular compositions are seen to detach from de laser target plasma.

Research paper thumbnail of Sub-micron size carbon structures synthesized using plasma enhanced CVD, without external heating and no catalyzer action

... [4] GY Chen, V. Stolojan, SRP Silva, H. Herman and S. Haq, Carbon 43 (2005), p. 704. Article ... more ... [4] GY Chen, V. Stolojan, SRP Silva, H. Herman and S. Haq, Carbon 43 (2005), p. 704. Article | PDF (263 K) | View Record in Scopus | Cited By in Scopus (19). [5] I. Denysenko, J. Berndt, E. Kovacevic and I. Stefanovic, Phys. Plasmas 13 (2006), p. 073507. ...

Research paper thumbnail of TiN coating on steel by pulsed capillary discharge

Research paper thumbnail of Surface modification by nitrogen plasma immersion ion implantation into new steel 460Li–21Cr in a capacitively coupled radio frequency discharge

Applied Surface Science, 2014

ABSTRACT A novel steel 460Li–21Cr belonging to a new generation of superferritic grade steel has ... more ABSTRACT A novel steel 460Li–21Cr belonging to a new generation of superferritic grade steel has been implanted with nitrogen in a low power 13.56 MHz radio frequency plasma by the plasma immersion ion implantation (PIII) technique in order to study its physical and chemical properties under different experimental conditions. We observed improved hardness and wear behavior of 460Li–21Cr steel with a layer thickness between 1.5 and 4.0 μm after 60 min implantation in the temperature range from 350 to 550 °C. The modified surface layer containing nitrogen does not show CrN in X-ray diffraction (XRD). Compared to untreated substrates, the hardness can be increased by a factor of 4, depending on the experimental conditions, and the wear behavior was also improved by two orders of magnitude. The results are very similar to those for austenitic stainless steel with a similar pronounced increase in wear resistance and plateau-like nitrogen depth profiles.

Research paper thumbnail of Hollow cathode effects in the pre-breakdown phase of a pulsed capillary discharge

Plasma Sources Science and Technology, 2009

Experimental observations of the hollow cathode effect (HCE) in an open end pulsed capillary disc... more Experimental observations of the hollow cathode effect (HCE) in an open end pulsed capillary discharge (PCD) are presented. In the HCE axial electron beams emitted from a pre-breakdown plasma produced spontaneously in the hollow cathode region (HCR) assist ionization growth in the interelectrode volume. The PCD operates in argon at 0.6-1.4 Torr, ∼10 kV applied voltage. Time resolved spectroscopic measurements, with 15 ns time resolution, are used in conjunction with photomultiplier observations of light emission from the capillary ends, and Faraday cup measurements of axial electron beams, to characterize the pre-and post-breakdown processes in the HCR of the discharge. The HCR emission is found to be dominated by Ar II lines. Comparison between measured and synthetic spectra indicates that the pre-breakdown HCR plasma is characteristic of a collisional low pressure, low density plasma, whereas the post-breakdown HCR plasma, tens of nanoseconds after breakdown, is due to plasma ejection from the capillary volume. Experimental evidence of a zippering effect in post-breakdown capillary plasma heating, due to an initial axial pressure gradient, as predicted by computer simulations, has been found.

Research paper thumbnail of High energy ion beam irradiation on titanium substrate in a pulsed plasma device operating with methane

Journal of Physics D: Applied Physics, 2009

We report the investigation of high energy ion beam irradiation on titanium (Ti) substrates at ro... more We report the investigation of high energy ion beam irradiation on titanium (Ti) substrates at room temperature using a low energy plasma focus (PF) device operating in methane gas. The surface modifications induced by the ion beam using two different anode materials, graphite and copper, are characterized using standard surface science diagnostic tools, such as x-ray diffraction, scanning electron microscopy,

Research paper thumbnail of Rapid synthesis of carbon nanoparticles with an optimized combination of specific surface area and crystallinity by a plasma-assisted single-step process

Journal of Physics D: Applied Physics, 2013

Research paper thumbnail of Measurements of plasma parameters in capacitively coupled radio frequency plasma from discharge characteristics: Correlation with optical emission spectroscopy

Current Applied Physics, 2013

Research paper thumbnail of Effect of ambient gas species on the formation of Cu nanoparticles in wire explosion process

Current Applied Physics, 2012

Research paper thumbnail of Plasma properties of a DC hollow cathode discharge

We have investigated the plasma properties of a Hollow Cathode Discharge (HCD) using different di... more We have investigated the plasma properties of a Hollow Cathode Discharge (HCD) using different dimensions of hollow cathode aperture (1 to 8 mm) in argon operating medium. The diagnostic used to investigate the plasma properties is a tiny Langmuir probe. The diameter and length of the Langmuir probe was chosen such that it draws a measurable current from the plasma causing a minimal perturbation to the surrounding plasma and remains rigid within the plasma as well as the cylindrical probe theories are applicable while calculating the electron temperature and plasma density. The probe was placed perpendicular to the axis of the hollow cathode at a distance of 20 mm from the hollow cathode side. The HCD was operated in the voltage range of 600 to 1000 V and pressures range of 70 to 100 mtorr. We observed that electron temperature and density varies with the operational condition. The estimated electron temperature is less than 10 eV and the temperature is maximum in the range of 3 to 5 mm diameter of the hollow cathode and a pressure range of 75 to 85 mTorr. The calculated maximum density is of the order of 10 10 cm -3 .

Research paper thumbnail of RECUBRIMIENTOS TiN EN ACERO MEDIANTE DESCARGA CAPILAR PULSADA

RESUMEN La geometría característica de una descarga capilar pulsada (PCD)[1] establece condicione... more RESUMEN La geometría característica de una descarga capilar pulsada (PCD)[1] establece condiciones naturales para la formación de jets de plasma, los cuales se expanden en el gas neutro presente en la cámara. Un capacitor de almacenamiento local, coaxial con el capilar, es cargado pulsadamente a un máximo de–10kV, lo que resulta en un pulso de corriente de~ 10ns,~ 2kA. La descarga es operada en Nitrógeno, en un modo pulsado continuo, a una frecuencia de 50 Hz y presiones entre 0.3 y 1 Torr. Se ha investigado el ...

Research paper thumbnail of Formation of carbon nanostructures by the plasma jets emitted from a pulsed capillary discharge at low pressures

We have performed an experimental analysis on the investigation of intense plasma jet irradiation... more We have performed an experimental analysis on the investigation of intense plasma jet irradiation on Si (100) substrates using a repetitive pulsed capillary discharge (PCD) device operating in methane gas at low pressure. The surface modifications induced by the plasma jet are characterized using standard surface science diagnostic tools, such as scanning electron microscopy (SEM), energy-dispersive x-ray (EDX) analysis and Raman spectroscopy (RS) and the results are reported. In particular, it has been found that with ...

Research paper thumbnail of Plasma species dynamics in a laser produced carbon plasma expanding in low pressure neutral gas background

Journal of Physics: Conference Series, 2012

ABSTRACT We present time and space resolved spectroscopic observations of a laser produced carbon... more ABSTRACT We present time and space resolved spectroscopic observations of a laser produced carbon plasma, in an argon background. An Nd:YAG laser pulse, 370 mJ, 3.5 ns, at 1.06 μm, with a fluence of 6.8 J/cm2, is used to produce a plasma from a solid graphite target, at a base pressure of 0.5 mTorr, and with 80 mTorr Argon background. The spectral emission in the visible is recorded with 15 ns time resolution. 20 ns time resolution plasma imagining, filtered at characteristic carbon species emission wavelengths, is used to study the dynamics of the expanding plasma. Two different fronts with ionic or molecular compositions are seen to detach from de laser target plasma.