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Papers by krushnamurty killi

Research paper thumbnail of Atomic and Molecular Layer Deposition of Chiral Thin Films Showing up to 99% Spin Selective Transport

Research paper thumbnail of Effect of Surface Chemistry of the Nano - Reinforcement Matrix on the Mechanical and Electrical Properties of FRPs

The present study has been devoted to achieve the optimum surface chemistry of the nano reinforce... more The present study has been devoted to achieve the optimum surface chemistry of the nano reinforcement ma trix for achieving the best mechanical properties . Two kinds of Fibre Reinfored Plastics (FRPs) were studied in the present work. They are glass fiber reinforced epoxy (glass - epoxy) composites and Carbon fiber reinforced epoxy (C - epoxy) composites. The fo rmer were studied for their impact and mechanical properties when reinforced with nanoclay and the later for their mechanical and electrical properties when reinforced with carbon nanotubes/carbon nanofibers or graphene oxide. For the E - glass - epoxy composi tes, studies were carried out to understand how does amine modified nanoclay influence the crosslink density and toughness of the epoxy matrix. Based on the toughness changes that were observed with the amino modified nanoclay addition to epoxy, new mecha nism was proposed on the mechanical property improvements for glass - epoxy reinforced with nanoclay. Typical resu...

Research paper thumbnail of Boron Monolayer Doping: Role of Oxide Capping Layer, Molecular Fragmentation, and Doping Uniformity at the Nanoscale

Advanced Materials Interfaces, 2020

Doping methodologies using monolayers offer controlled, ex-situ doping of NWs and 3D device archi... more Doping methodologies using monolayers offer controlled, ex-situ doping of NWs and 3D device architectures using molecular monolayers as dopant sources with uniform, self-limiting characteristics. Comparing doping levels and uniformity for boron containing monolayers using different methodologies demonstrate the effects of oxide capping on doping performances following rapid thermal anneal (RTA). Strikingly, for non-covalent monolayers of phenylboronic acid (PBA), highest doping levels are obtained with minimal thermal budget without applying the oxide capping layer. These results are accounted for by considering monolayer damage and entrapment of molecular fragments in the oxide capping layer because thermal damage to the PBA monolayer which result in transformation of the monolayer source to a thin solid source layer. The impact of the oxide capping procedure is demonstrated by a series of experiments. Details of monolayer fragmentation processes and its impact on doping uniformity at the nanoscale are addressed for two types of surface chemistries by applying Kelvin probe force microscopy (KPFM). Our results point at the importance of molecular decomposition processes for monolayer-based doping methodologies, both during pre-anneal capping step and during rapid thermal processing step. These are important guidelines to be considered for future developments of appropriate surface chemistry used in monolayer doping applications.

Research paper thumbnail of Metal Oxide Interlayer for Long-Lived Lithium-Selenium Batteries

Chemistry - A European Journal, 2018

A Lithium (Li)-Selenium (Se)-alkali activated carbon hybrid cell with a tungsten oxide interlayer... more A Lithium (Li)-Selenium (Se)-alkali activated carbon hybrid cell with a tungsten oxide interlayer is implemented for the first time. The Se hybrid at a Se loading of 70% in the full Li-Se cell, delivers a large reversible capacity of 625 mAh gSe-1 as opposed to 505.8 mAh gSe-1 achieved for the pristine Se cell. This clearly shows the advantage of the carbon in improving the capacity of the Li-Se cell. To further circumvent the issues of polyselenide dissolution and shuttle which cause severe capacity fade, a tungsten oxide interlayer is drop-cast over the battery separator. While the oxide layer conducts Li-ions which is evidenced from a Li-ion diffusion coefficient of 4.2  10-9 cm 2 s-1 , it simultaneously blocks the polyselenide cross-over for it is impermeable to polyselenides, thereby reducing the capacity fade with cycling. The outcome of this unique approach is reflected in the reversible capacities of 808 and 510 mAh gSe-1 , achieved for the Li-oxide@separator/Se-alkali activated carbon cell before and after 100 cycles, thus demonstrating that carbon and oxide can efficiently restrict the capacity fade and improve the performances of Li-Se cells.

Research paper thumbnail of Fast and clean functionalization of MWCNTs by DBD plasma and its influence on mechanical properties of C–epoxy composites

RSC Adv., 2015

TPD profile of various MWCNTs samples before and after air plasma treatment: (a) CO2 evolution, (... more TPD profile of various MWCNTs samples before and after air plasma treatment: (a) CO2 evolution, (b) CO evolution.

Research paper thumbnail of The reinforcement ability of ozone-treated CNFs on mechanical properties of C–epoxy composites

Composite Interfaces, 2015

ABSTRACT

Research paper thumbnail of Catalytic nonthermal plasma assisted co-processing of methane and nitrous oxide for methanol production

Catalysis Today, 2015

ABSTRACT

Research paper thumbnail of Effect of Plasma Etched CNFs on Toughness and Mechanical Properties of Epoxy Composites

Materials and Manufacturing Processes, 2014

ABSTRACT Carbon nanofibers (CNFs) are plasma etched by using cold plasma of Air and Helium for di... more ABSTRACT Carbon nanofibers (CNFs) are plasma etched by using cold plasma of Air and Helium for different time durations. Changes in surface functional groups of CNFs due to plasma treatment was estimated by using elemental analysis and temperature programmed decomposition (TPD) in helium atmosphere. The influence of plasma etched CNFs on the toughness of epoxy and tensile, flexural strength of carbon-epoxy composites have been studied. Results indicate that, air plasma etched CNFs can improve the toughness of epoxy, while Helium plasma etched CNFs could not impart improved toughness to epoxy composites. On the other hand, mechanical properties of carbon-epoxy made with air plasma etched CNFs improved significantly as compared to Helium plasma etched CNFs as well as untreated CNFs.

Research paper thumbnail of The Reinforcement Ability of Plasma-Etched Carbon Nanofibers on Mechanical Properties of C-Epoxy Composites

Plasma Processes and Polymers, 2014

Carbon nanofibers (CNFs) are plasma etched by using cold plasma of helium and air for different t... more Carbon nanofibers (CNFs) are plasma etched by using cold plasma of helium and air for different time durations. Changes in surface characteristics of CNFs due to plasma treatment was studied with Raman spectroscopy, BET surface area analyzer, and atomic force microscopy (AFM). Raman spectroscopic studies showed that, plasma treatment is imparting enhanced degree of disorder for CNFs. While AFM studies indicated enhancement in the surface roughness due to plasma treatment. Laminated (2D) carbon fiber reinforced epoxy matrix (C-epoxy) composites were fabricated with the addition of 0.5 wt% of plasma-etched CNFs and evaluated the mechanical properties of the prepared composites. Results indicate that, plasma-etched CNFs can improve the mechanical properties of CFRPs significantly as compared to untreated CNFs.

Research paper thumbnail of Surface modification of carbon fabric for isopropanol removal from gas stream

Microelectronic Engineering, 2014

Display Omitted Surface modification of carbon fabric by plasma and nitric acid.The increasing ox... more Display Omitted Surface modification of carbon fabric by plasma and nitric acid.The increasing oxygen concentration was estimated by using elemental analysis.Oxygen concentration of CF was quantified by novel method temperature programmed decomposition.Improvement in the IPA adsorption performance of CF after activation. The surface chemistry of carbon fabric (CF) was modified by both chemical and physical activation. The increasing oxygen concentration was estimated by using elemental analysis, and quantified by temperature programmed decomposition (TPD) in helium atmosphere. Modified carbon fabrics were used as adsorbents during the removal of a model volatile organic compounds (VOCs) isopropanol from gas streams. Typical results indicated that CF modified by air plasma has the best adsorption capacity, probably due to the formation of highest amount of acidic functional groups during the treatment.

Research paper thumbnail of Preparation of activated carbons from bio-waste: effect of surface functional groups on methylene blue adsorption

International Journal of Environmental Science and Technology, 2014

Low-cost activated carbons were prepared by physical activation of bio-waste rice husk. Various p... more Low-cost activated carbons were prepared by physical activation of bio-waste rice husk. Various physicochemical characterization techniques confirmed the high surface area and oxygen functional groups on the surface. It has been confirmed that activation under humidified carbon dioxide followed by ozonation resulted the highest number of surface functional groups on activated carbon. Nitrogen adsorption-desorption isotherms confirmed the highest surface area (417 m 2 /g), whereas elemental analysis ensured the increasing oxygen content after activation. Temperature-programmed decomposition quantified these surface oxygen functional groups, and it was concluded that ozonation increased both acidic and basic groups. The developed activated carbons were tested during the removal of a model dye methylene blue from aqueous medium in the concentration range 10-30 mg/L. Typical results indicated that adsorption studies are consistent with the Langmuir isotherm model with maximum monolayer adsorption capacity of 28.5 mg/g, and the dimensionless separation factor (R L) values between 0.006 and 0.030 confirmed a favorable adsorption. Methylene blue adsorption followed pseudo-second order kinetics indicating MB was adsorbed onto the surface via chemical interaction.

Research paper thumbnail of Layered Si–Ti oxide thin films with tailored electrical and optical properties by catalytic tandem MLD-ALD

RSC Advances, 2021

Layer-by-layer deposition of Si–Ti layered oxide thin films are obtained using catalytic tandem M... more Layer-by-layer deposition of Si–Ti layered oxide thin films are obtained using catalytic tandem M/ALD methodology. The films exhibit optical (RI) and electrical conductivities by selecting the MLD to ALD proportion in the super cycle.

Research paper thumbnail of Atomic and Molecular Layer Deposition of Chiral Thin Films Showing up to 99% Spin Selective Transport

Research paper thumbnail of Effect of Surface Chemistry of the Nano - Reinforcement Matrix on the Mechanical and Electrical Properties of FRPs

The present study has been devoted to achieve the optimum surface chemistry of the nano reinforce... more The present study has been devoted to achieve the optimum surface chemistry of the nano reinforcement ma trix for achieving the best mechanical properties . Two kinds of Fibre Reinfored Plastics (FRPs) were studied in the present work. They are glass fiber reinforced epoxy (glass - epoxy) composites and Carbon fiber reinforced epoxy (C - epoxy) composites. The fo rmer were studied for their impact and mechanical properties when reinforced with nanoclay and the later for their mechanical and electrical properties when reinforced with carbon nanotubes/carbon nanofibers or graphene oxide. For the E - glass - epoxy composi tes, studies were carried out to understand how does amine modified nanoclay influence the crosslink density and toughness of the epoxy matrix. Based on the toughness changes that were observed with the amino modified nanoclay addition to epoxy, new mecha nism was proposed on the mechanical property improvements for glass - epoxy reinforced with nanoclay. Typical resu...

Research paper thumbnail of Boron Monolayer Doping: Role of Oxide Capping Layer, Molecular Fragmentation, and Doping Uniformity at the Nanoscale

Advanced Materials Interfaces, 2020

Doping methodologies using monolayers offer controlled, ex-situ doping of NWs and 3D device archi... more Doping methodologies using monolayers offer controlled, ex-situ doping of NWs and 3D device architectures using molecular monolayers as dopant sources with uniform, self-limiting characteristics. Comparing doping levels and uniformity for boron containing monolayers using different methodologies demonstrate the effects of oxide capping on doping performances following rapid thermal anneal (RTA). Strikingly, for non-covalent monolayers of phenylboronic acid (PBA), highest doping levels are obtained with minimal thermal budget without applying the oxide capping layer. These results are accounted for by considering monolayer damage and entrapment of molecular fragments in the oxide capping layer because thermal damage to the PBA monolayer which result in transformation of the monolayer source to a thin solid source layer. The impact of the oxide capping procedure is demonstrated by a series of experiments. Details of monolayer fragmentation processes and its impact on doping uniformity at the nanoscale are addressed for two types of surface chemistries by applying Kelvin probe force microscopy (KPFM). Our results point at the importance of molecular decomposition processes for monolayer-based doping methodologies, both during pre-anneal capping step and during rapid thermal processing step. These are important guidelines to be considered for future developments of appropriate surface chemistry used in monolayer doping applications.

Research paper thumbnail of Metal Oxide Interlayer for Long-Lived Lithium-Selenium Batteries

Chemistry - A European Journal, 2018

A Lithium (Li)-Selenium (Se)-alkali activated carbon hybrid cell with a tungsten oxide interlayer... more A Lithium (Li)-Selenium (Se)-alkali activated carbon hybrid cell with a tungsten oxide interlayer is implemented for the first time. The Se hybrid at a Se loading of 70% in the full Li-Se cell, delivers a large reversible capacity of 625 mAh gSe-1 as opposed to 505.8 mAh gSe-1 achieved for the pristine Se cell. This clearly shows the advantage of the carbon in improving the capacity of the Li-Se cell. To further circumvent the issues of polyselenide dissolution and shuttle which cause severe capacity fade, a tungsten oxide interlayer is drop-cast over the battery separator. While the oxide layer conducts Li-ions which is evidenced from a Li-ion diffusion coefficient of 4.2  10-9 cm 2 s-1 , it simultaneously blocks the polyselenide cross-over for it is impermeable to polyselenides, thereby reducing the capacity fade with cycling. The outcome of this unique approach is reflected in the reversible capacities of 808 and 510 mAh gSe-1 , achieved for the Li-oxide@separator/Se-alkali activated carbon cell before and after 100 cycles, thus demonstrating that carbon and oxide can efficiently restrict the capacity fade and improve the performances of Li-Se cells.

Research paper thumbnail of Fast and clean functionalization of MWCNTs by DBD plasma and its influence on mechanical properties of C–epoxy composites

RSC Adv., 2015

TPD profile of various MWCNTs samples before and after air plasma treatment: (a) CO2 evolution, (... more TPD profile of various MWCNTs samples before and after air plasma treatment: (a) CO2 evolution, (b) CO evolution.

Research paper thumbnail of The reinforcement ability of ozone-treated CNFs on mechanical properties of C–epoxy composites

Composite Interfaces, 2015

ABSTRACT

Research paper thumbnail of Catalytic nonthermal plasma assisted co-processing of methane and nitrous oxide for methanol production

Catalysis Today, 2015

ABSTRACT

Research paper thumbnail of Effect of Plasma Etched CNFs on Toughness and Mechanical Properties of Epoxy Composites

Materials and Manufacturing Processes, 2014

ABSTRACT Carbon nanofibers (CNFs) are plasma etched by using cold plasma of Air and Helium for di... more ABSTRACT Carbon nanofibers (CNFs) are plasma etched by using cold plasma of Air and Helium for different time durations. Changes in surface functional groups of CNFs due to plasma treatment was estimated by using elemental analysis and temperature programmed decomposition (TPD) in helium atmosphere. The influence of plasma etched CNFs on the toughness of epoxy and tensile, flexural strength of carbon-epoxy composites have been studied. Results indicate that, air plasma etched CNFs can improve the toughness of epoxy, while Helium plasma etched CNFs could not impart improved toughness to epoxy composites. On the other hand, mechanical properties of carbon-epoxy made with air plasma etched CNFs improved significantly as compared to Helium plasma etched CNFs as well as untreated CNFs.

Research paper thumbnail of The Reinforcement Ability of Plasma-Etched Carbon Nanofibers on Mechanical Properties of C-Epoxy Composites

Plasma Processes and Polymers, 2014

Carbon nanofibers (CNFs) are plasma etched by using cold plasma of helium and air for different t... more Carbon nanofibers (CNFs) are plasma etched by using cold plasma of helium and air for different time durations. Changes in surface characteristics of CNFs due to plasma treatment was studied with Raman spectroscopy, BET surface area analyzer, and atomic force microscopy (AFM). Raman spectroscopic studies showed that, plasma treatment is imparting enhanced degree of disorder for CNFs. While AFM studies indicated enhancement in the surface roughness due to plasma treatment. Laminated (2D) carbon fiber reinforced epoxy matrix (C-epoxy) composites were fabricated with the addition of 0.5 wt% of plasma-etched CNFs and evaluated the mechanical properties of the prepared composites. Results indicate that, plasma-etched CNFs can improve the mechanical properties of CFRPs significantly as compared to untreated CNFs.

Research paper thumbnail of Surface modification of carbon fabric for isopropanol removal from gas stream

Microelectronic Engineering, 2014

Display Omitted Surface modification of carbon fabric by plasma and nitric acid.The increasing ox... more Display Omitted Surface modification of carbon fabric by plasma and nitric acid.The increasing oxygen concentration was estimated by using elemental analysis.Oxygen concentration of CF was quantified by novel method temperature programmed decomposition.Improvement in the IPA adsorption performance of CF after activation. The surface chemistry of carbon fabric (CF) was modified by both chemical and physical activation. The increasing oxygen concentration was estimated by using elemental analysis, and quantified by temperature programmed decomposition (TPD) in helium atmosphere. Modified carbon fabrics were used as adsorbents during the removal of a model volatile organic compounds (VOCs) isopropanol from gas streams. Typical results indicated that CF modified by air plasma has the best adsorption capacity, probably due to the formation of highest amount of acidic functional groups during the treatment.

Research paper thumbnail of Preparation of activated carbons from bio-waste: effect of surface functional groups on methylene blue adsorption

International Journal of Environmental Science and Technology, 2014

Low-cost activated carbons were prepared by physical activation of bio-waste rice husk. Various p... more Low-cost activated carbons were prepared by physical activation of bio-waste rice husk. Various physicochemical characterization techniques confirmed the high surface area and oxygen functional groups on the surface. It has been confirmed that activation under humidified carbon dioxide followed by ozonation resulted the highest number of surface functional groups on activated carbon. Nitrogen adsorption-desorption isotherms confirmed the highest surface area (417 m 2 /g), whereas elemental analysis ensured the increasing oxygen content after activation. Temperature-programmed decomposition quantified these surface oxygen functional groups, and it was concluded that ozonation increased both acidic and basic groups. The developed activated carbons were tested during the removal of a model dye methylene blue from aqueous medium in the concentration range 10-30 mg/L. Typical results indicated that adsorption studies are consistent with the Langmuir isotherm model with maximum monolayer adsorption capacity of 28.5 mg/g, and the dimensionless separation factor (R L) values between 0.006 and 0.030 confirmed a favorable adsorption. Methylene blue adsorption followed pseudo-second order kinetics indicating MB was adsorbed onto the surface via chemical interaction.

Research paper thumbnail of Layered Si–Ti oxide thin films with tailored electrical and optical properties by catalytic tandem MLD-ALD

RSC Advances, 2021

Layer-by-layer deposition of Si–Ti layered oxide thin films are obtained using catalytic tandem M... more Layer-by-layer deposition of Si–Ti layered oxide thin films are obtained using catalytic tandem M/ALD methodology. The films exhibit optical (RI) and electrical conductivities by selecting the MLD to ALD proportion in the super cycle.