The African Maize Cobs (AMC) biomass was converted into activated carbon (AC) for electrode materials for supercapacitor application. The carbonization was carried out with concentrated sulphuric acid and the activation was done in three... more
The African Maize Cobs (AMC) biomass was converted into activated carbon (AC) for electrode materials for supercapacitor application. The carbonization was carried out with concentrated sulphuric acid and the activation was done in three (3) batches using activation temperatures of 600, 700 and 800oC. The AC materials were characterized by Thermogravimetric analysis (TGA-DSC), N2-adsorption-desorption isotherms, Field Emission Scanning Electron Microscopy (FESEM), Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Diffraction (XRD), Boehm titration, X-ray Photoelectron Spectroscopy (XPS), Raman Spectroscopy and electrochemical analysis (EC). The materials activated were highly functionalized with oxygen groups with total acidity of 0.440 – 0.464mmol/g, basicity of 0.09 – 0.420mmol/g and oxygen percentage composition of 22 – 32%. The AC materials were analysed with EC as electrode material for supercapacitor devices. The electrode materials revealed specific capacitance of; 456.4 ...
Abstract An adaptable and simplified arc underwater set-up is designed for synthesis of nanostructured carbon materials (NSCM) such as carbon onions (CO), multi-walled carbon nanotubes (MWCNTs) and nanoscale graphitic carbon (NGC).... more
Abstract An adaptable and simplified arc underwater set-up is designed for synthesis of nanostructured carbon materials (NSCM) such as carbon onions (CO), multi-walled carbon nanotubes (MWCNTs) and nanoscale graphitic carbon (NGC). Essentially, the set-up consists of a DC power supply, two graphite electrodes and a container for de-ionized water storage. Transmission electron microscopic analysis confirmed that the cathode deposit, floating particles and settled materials consist of MWCNTs, CO and NGC, respectively. The kind of NSCM formation is critically governed by temperature gradient and cooling rate created due to bubble collapse in nucleate boiling during the arcing process. Based on the anode consumption, the total yield of the carbon materials is about ∼ 25.5 wt% which consists 5 wt% of FP, 8.5 wt% of CD and remaining 12 wt% of SP. FP, CD, and SP presented crystallite size of 23.69 nm, 11.84 nm, and 28.91 nm, respectively. The high rate and moderate rate of cooling will determine the growth of MWCNTs and CO, respectively. NGC exhibited specific capacity of 325 mAhg − 1 with lithium half-cell after 50 cycles at a current density of 100 mAg−1.
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Natural graphite flakes were intercalated with strong oxidizing agents and were converted into thermally expanded graphite (TEG) through thermal exfoliation. Thermally expanded graphite was delaminated and transformed into graphene... more
Natural graphite flakes were intercalated with strong oxidizing agents and were converted into thermally expanded graphite (TEG) through thermal exfoliation. Thermally expanded graphite was delaminated and transformed into graphene nanoplatelets (GNP) by using ultrasonic irradiation. GNP integrated polyaniline (PANi) nanocomposites were synthesized via in-situ polymerization of aniline monomers in the presence of GNP. The structure and morphology of composite was evidenced by scanning electron microscopy, Transmission electron microscopy (TEM), X-ray diffraction and Raman spectroscopy. TEM micrographs revealed that GNP consists of 20–25 graphene layers and PANi was uniformly coated on GNP. From Raman analysis it was showed significant interactions between GNP and polyaniline. Electrical conductivity was measured by using 4-point probe device, enhanced conductivity was obtained for composite.
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Graphene nanoplatelets (GNP) with few layers were prepared via expanded graphite derived from exfoliation and, then solution-phase exfoliation. GNPs consist of 7–12 distinguishable graphene layers and possess lateral sizes in the range of... more
Graphene nanoplatelets (GNP) with few layers were prepared via expanded graphite derived from exfoliation and, then solution-phase exfoliation. GNPs consist of 7–12 distinguishable graphene layers and possess lateral sizes in the range of 2–6 μ. An attempt was made to exploit the thermal properties of GNP as filler to ameliorate thermo physical properties of xylitol. Such ultrathin 2-D structured GNP could able to increase thermal conductivity by 38% with the addition of low concentration associated with a reasonable enthalpy of fusion. Phase change materials find application in a medium temperature range such as thermal energy storage of solar energy, direct contact heat storage in heat exchangers, thermal energy storage in spacecraft systems, cooling of engines and compact electronic appliances.
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We report on a simplistic procedure of converting solid waste (discarded bicycle’s rubber tube) to value-added low-dimensional carbon material, and it was used as a negative material (anode) for Na...
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Abstract We report on capacitive properties of functionally-graded porous activated nanoscaled-graphene platelets (aNGNS) prepared via reexfoliation of graphite, and high-energy fragmentation through mixed solvent strategy followed by... more
Abstract We report on capacitive properties of functionally-graded porous activated nanoscaled-graphene platelets (aNGNS) prepared via reexfoliation of graphite, and high-energy fragmentation through mixed solvent strategy followed by thermochemical etch-away conversion. aNGNS based symmetric supercapacitor demonstrated excellent specific capacitance of 242 F/g at the current density of 0.5A/g with a capacity retention of 97.21 % after 1000 cycles. The device shown remarkable energy density of 27.22 Wh/kg at a power density of 230.56 W/kg at constant current density of 0.5 A/g. Moreover, the enormous amount of porosity created via chemical-assisted etching could facilitate minimal ion-diffusion resistance to achieve exceptional specific capacitance.
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Oxidation behavior of tungsten disulphide (WS2) nanosheet powder with an average thickness of about 10 nm was studied in the temperature range of 25-700°C. The samples were subjected to exposures...
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Abstract Among various energy storage devices, pseudo capacitive supercapacitors have gained much attention due to its unique features of high-power density and fair enough energy density. This work is aimed to fabricate high power... more
Abstract Among various energy storage devices, pseudo capacitive supercapacitors have gained much attention due to its unique features of high-power density and fair enough energy density. This work is aimed to fabricate high power density and energy density supercapacitor by using MnO2 nano-flakes as electrode material. MnO2 nano-flakes have been synthesized using hydrothermal technique and incorporated in supercapacitor structure to study the performance. The electrochemical performance of MnO2 nano-flake electrode was investigated and obtained a specific capacitance of 145 F.g−1 at 5 mV.s−1 with energy density of 20.16 Wh.kg−1 and power density of 363.03 W.kg−1.
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Abstract For sustainable application of supercapacitor high energy density along with high power density is becoming an obvious requirement. This work is aimed at utilizing the features of 2D-layered structure and high surface area of... more
Abstract For sustainable application of supercapacitor high energy density along with high power density is becoming an obvious requirement. This work is aimed at utilizing the features of 2D-layered structure and high surface area of MoS2 as electrode for supercapacitor to achieve high energy density and capacitance retention. One step hydrothermal technique is used to synthesize MoS2 layered structure and its performance is studied through electrochemical analysis. The electrochemical performance of MoS2 electrode is tested in a full cell module and a specific capacitance of 255 F·g−1 at 0.25 A·g−1 with energy density of 35.5 W·kg−1 is achieved.
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ABSTRACT Substitutional nitrogen doped aligned carbon nanotubes (NACNTs) with uniform height and high packing density of arrays was synthesized by using the liquid injection CVD process. Transmission electron micrographs indicated that... more
ABSTRACT Substitutional nitrogen doped aligned carbon nanotubes (NACNTs) with uniform height and high packing density of arrays was synthesized by using the liquid injection CVD process. Transmission electron micrographs indicated that the NACNTs are having nano-bell morphology of graphene layers with series of internal compartments. Field emission study of NACNTs showed that they are good emitters with low turn-on and threshold field. The maximum current density was observed to be 18.8 mA/cm2 at electric field of 1.89 V/μm.
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... these results. We are also thankful to Dr. Padmanabham, Associate Director for his encour-agement during this work. We also thank Ms. Malathi, Mr. G. VenkatReddy and K. Subba Rao for their extensive help. The authors ...
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ABSTRACT Multi-walled carbon nanotubes (MWCNTs) and graphite nanosheets (GNS) reinforced epoxy nanocomposites are synthesized by solution mixing process. Various surface active groups on filler materials are analyzed and their effect on... more
ABSTRACT Multi-walled carbon nanotubes (MWCNTs) and graphite nanosheets (GNS) reinforced epoxy nanocomposites are synthesized by solution mixing process. Various surface active groups on filler materials are analyzed and their effect on dispersion, interfacial bonding was correlated to the thermal conductivity and dimensional stability of the nanocomposites. Thermal conductivity of MWCNTs/epoxy nanocomposites was enhanced by 34% when compared to GNS/epoxy nanocomposites at room temperature. Improved dimensional stability was also observed in the case of MWCNTs/epoxy nanocomposites. Poor thermal properties of GNS/epoxy nanocomposites are due to formation of GNS agglomerates in the nanocomposites.
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A composite constituted by carbon nanopipes (CNPs) and polyaniline nanofibers (PANi NFs) is synthesized using in-situ chemical oxidative polymerization. Owing to its electrochemical activity the composite is found to be suitable as a... more
A composite constituted by carbon nanopipes (CNPs) and polyaniline nanofibers (PANi NFs) is synthesized using in-situ chemical oxidative polymerization. Owing to its electrochemical activity the composite is found to be suitable as a working electrode material in hybrid type supercapacitors. Microstructural and phase analyses of the composite showed that (i) CNP surfaces are coated with PANi and (ii) PANi coated CNPs are distributed among PANi NFs. The composite shows an excellent electrochemical activity and a high specific capacitance of ~224.39 F/g. The electro-chemical activity of the composite is explicated in correlation with crystallinity, intrinsic oxidation state, and doping degree of PANi in the composite. The electro-chemical activity of the composite is also explicated in correlation with BET surface area and ordered meso-porosity pertaining to the composite. Charge/discharge curves indicate that the specific capacitance of the composite is a result of electric double-layer capacitance offered by CNPs and Faradaic pseudo capacitance offered by PANi NFs.
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In this work, African maize cobs (AMC) were used as a rich biomass precursor to synthesize carbon material through a chemical activation process for application in electrochemical energy storage devices. The carbonization and activation... more
In this work, African maize cobs (AMC) were used as a rich biomass precursor to synthesize carbon material through a chemical activation process for application in electrochemical energy storage devices. The carbonization and activation were carried out with concentrated Sulphuric acid at three different temperatures of 600, 700 and 800 °C, respectively. The activated carbon exhibited excellent microporous and mesoporous structure with a specific surface area that ranges between 30 and 254 m2·g−1 as measured by BET analysis. The morphology and structure of the produced materials are analyzed through Field Emission Scanning Electron Microscopy (FESEM), Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Diffraction (XRD), Boehm titration, X-ray Photoelectron Spectroscopy (XPS) and Raman Spectroscopy. X-ray photoelectron spectroscopy indicates that a considerable amount of oxygen is present in the materials. The functional groups in the activated carbon enhanced the electrochemical ...
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ABSTRACT Amongst various carbon nanomaterials, carbon nanofibers (CNFs) have lately attracted considerable interest as a promising reinforcement in polymer matrix composites. CNFs are often synthesized using copper nanoparticles as... more
ABSTRACT Amongst various carbon nanomaterials, carbon nanofibers (CNFs) have lately attracted considerable interest as a promising reinforcement in polymer matrix composites. CNFs are often synthesized using copper nanoparticles as catalysts and by using chemical vapor deposition (CVD). In this work iron (Fe) nanoparticles are used as catalysts to synthesize amorphous carbon nanofibers. This owes significance since Fe nanoparticles often lead to tubes rather than fibers. Fe nanoparticles (size ~30-60nm) are prepared by first mixing an appropriate quantity of potassium sodium tartrate tetrahydrate salt with iron (II) chloride dehydrate to obtain iron tartrate and then dried and heated in vacuum oven at about 250°C to remove tartrate. In a subsequent step, CNFs are obtained by using CVD. Acetylene was used as the carbon source in the CVD process. Scanning and transmission electron microscopy show the formation of nanofibers whose diameter is dependent on the size of Fe catalysts. Raman scattering from the fibers show that they are made up of carbon and are amorphous.
Background and purpose: For application in supercapacitors, improving the efficiency of the electrode materials is the most important for obtaining high performance. Porous carbon with suitable architectures is reliable for improved... more
Background and purpose: For application in supercapacitors, improving the efficiency of the electrode materials is the most important for obtaining high performance. Porous carbon with suitable architectures is reliable for improved electrochemical capacitors. In this study, we optimized the maize cobs as a potential abundant precursor for the production of porous carbon supercapacitor applications. This research study aimed to advance on the activation method for Activation of the biomass and to up-cycling agricultural biomass into carbon-based porous materials for supercapacitor electrode application. The carbonized samples were kept in a desiccator for 3 hours to allow intercalation and interaction of the carbon lattice expansion by K+ ion before Activation [Topic, RQ]. Results: The physical and chemical characterization of the synthesized materials was carried out several techniques for determining different properties of the activated carbon from maize cobs, including; structur...
ABSTRACT Few-walled carbon nanotubes (CNTs) were synthesized by the arc discharge process. The study pertains to analyze the effect of buffer gas pressure (Helium) and density of graphite anodes on morphology and yield of CNTs. The... more
ABSTRACT Few-walled carbon nanotubes (CNTs) were synthesized by the arc discharge process. The study pertains to analyze the effect of buffer gas pressure (Helium) and density of graphite anodes on morphology and yield of CNTs. The synthesis of CNTs was carried out at different buffer pressures of Helium ranging from 80 Torr to 600 Torr using different anode densities specifically 1.6 and 1.8 gm/cc. FE-SEM and TGA studies indicated that the highest percentage of MWCNTs was formed around 450 Torr pressure as compared to other pressures. It was observed that the variation of gas pressure affects the current drawn capacity and also the evaporation rate of the graphite electrode. Micro-structure of CNTs synthesized at 450 Torr consists of 8 concentric graphene layers. Improved crystallinity with better thermal stability was observed in case of high density graphite anode.
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Pristine and surface modified multi-walled carbon nanotubes (MWCNT) were used to fabricate MWNTV epoxy composite materials by solution mixing process. A suitable chemical treatment was performed in order to create the functional sites on... more
Pristine and surface modified multi-walled carbon nanotubes (MWCNT) were used to fabricate MWNTV epoxy composite materials by solution mixing process. A suitable chemical treatment was performed in order to create the functional sites on MWCNTs for firm interlocking in between the filler and the matrix for better interfacial load transfer. The increase in oxygen related moieties was confirmed by x-ray photoelectron spectroscopy. The effect of MWNT addition and their surface modification on the flexural strength and thermal conductivity was investigated. FE-SEM study was carried out for observing the morphology of reinforcing materials as well as its dispersion in the polymer matrix. Thermal conductivity of nanocomposites containing 1wt% of modified and unmodified MWCNT were evaluated. The increase in flexural strength of the composite materials was observed with the addition of pristine and modified MWCNT by 55% and 100 %, respectively.
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Pristine and surface modified multi-walled carbon nanotubes (MWCNT) were used to fabricate MWNTV epoxy composite materials by solution mixing process. A suitable chemical treatment was performed in order to create the functional sites on... more
Pristine and surface modified multi-walled carbon nanotubes (MWCNT) were used to fabricate MWNTV epoxy composite materials by solution mixing process. A suitable chemical treatment was performed in order to create the functional sites on MWCNTs for firm interlocking in between the filler and the matrix for better interfacial load transfer. The increase in oxygen related moieties was confirmed by x-ray photoelectron spectroscopy. The effect of MWNT addition and their surface modification on the flexural strength and thermal conductivity was investigated. FE-SEM study was carried out for observing the morphology of reinforcing materials as well as its dispersion in the polymer matrix. Thermal conductivity of nanocomposites containing 1wt% of modified and unmodified MWCNT were evaluated. The increase in flexural strength of the composite materials was observed with the addition of pristine and modified MWCNT by 55% and 100 %, respectively.
Pristine and surface modified multi-walled carbon nanotubes (MWCNT) were used to fabricate MWNTV epoxy composite materials by solution mixing process. A suitable chemical treatment was performed in order to create the functional sites on... more
Pristine and surface modified multi-walled carbon nanotubes (MWCNT) were used to fabricate MWNTV epoxy composite materials by solution mixing process. A suitable chemical treatment was performed in order to create the functional sites on MWCNTs for firm interlocking in between the filler and the matrix for better interfacial load transfer. The increase in oxygen related moieties was confirmed by x-ray photoelectron spectroscopy. The effect of MWNT addition and their surface modification on the flexural strength and thermal conductivity was investigated. FE-SEM study was carried out for observing the morphology of reinforcing materials as well as its dispersion in the polymer matrix. Thermal conductivity of nanocomposites containing 1wt% of modified and unmodified MWCNT were evaluated. The increase in flexural strength of the composite materials was observed with the addition of pristine and modified MWCNT by 55% and 100 %, respectively.
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Pristine and surface modified multi-walled carbon nanotubes (MWCNT) were used to fabricate MWNTV epoxy composite materials by solution mixing process. A suitable chemical treatment was performed in order to create the functional sites on... more
Pristine and surface modified multi-walled carbon nanotubes (MWCNT) were used to fabricate MWNTV epoxy composite materials by solution mixing process. A suitable chemical treatment was performed in order to create the functional sites on MWCNTs for firm interlocking in between the filler and the matrix for better interfacial load transfer. The increase in oxygen related moieties was confirmed by x-ray photoelectron spectroscopy. The effect of MWNT addition and their surface modification on the flexural strength and thermal conductivity was investigated. FE-SEM study was carried out for observing the morphology of reinforcing materials as well as its dispersion in the polymer matrix. Thermal conductivity of nanocomposites containing 1wt% of modified and unmodified MWCNT were evaluated. The increase in flexural strength of the composite materials was observed with the addition of pristine and modified MWCNT by 55% and 100 %, respectively.
Pristine and surface modified multi-walled carbon nanotubes (MWCNT) were used to fabricate MWNTV epoxy composite materials by solution mixing process. A suitable chemical treatment was performed in order to create the functional sites on... more
Pristine and surface modified multi-walled carbon nanotubes (MWCNT) were used to fabricate MWNTV epoxy composite materials by solution mixing process. A suitable chemical treatment was performed in order to create the functional sites on MWCNTs for firm interlocking in between the filler and the matrix for better interfacial load transfer. The increase in oxygen related moieties was confirmed by x-ray photoelectron spectroscopy. The effect of MWNT addition and their surface modification on the flexural strength and thermal conductivity was investigated. FE-SEM study was carried out for observing the morphology of reinforcing materials as well as its dispersion in the polymer matrix. Thermal conductivity of nanocomposites containing 1wt% of modified and unmodified MWCNT were evaluated. The increase in flexural strength of the composite materials was observed with the addition of pristine and modified MWCNT by 55% and 100 %, respectively.
Pristine and surface modified multi-walled carbon nanotubes (MWCNT) were used to fabricate MWNTV epoxy composite materials by solution mixing process. A suitable chemical treatment was performed in order to create the functional sites on... more
Pristine and surface modified multi-walled carbon nanotubes (MWCNT) were used to fabricate MWNTV epoxy composite materials by solution mixing process. A suitable chemical treatment was performed in order to create the functional sites on MWCNTs for firm interlocking in between the filler and the matrix for better interfacial load transfer. The increase in oxygen related moieties was confirmed by x-ray photoelectron spectroscopy. The effect of MWNT addition and their surface modification on the flexural strength and thermal conductivity was investigated. FE-SEM study was carried out for observing the morphology of reinforcing materials as well as its dispersion in the polymer matrix. Thermal conductivity of nanocomposites containing 1wt% of modified and unmodified MWCNT were evaluated. The increase in flexural strength of the composite materials was observed with the addition of pristine and modified MWCNT by 55% and 100 %, respectively.