Kingsuk MukhopadhyayDMSRDE (DRDO), Kanpur · Materials Science
Research Items (65)
- Dec 2018
The Aluminium Nitride (AlN) powder/ thin films were prepared from aluminium–urea complex. The complex, hexa urea aluminate (III) chloride, have proven a potential single source precursor to aluminum nitrides, because urea molecules construct a coordination sphere around the metal atom and form a stable structure, compared with the air sensitive halides and hydrides. The precursor and spin coated thin films of precursor on quartz and Si (100) substrates were pyrolysed at various temperatures (800oC to 1000oC) and pressure (100Torr to 1Torr) under nitrogen atmosphere. The pyrolysed powders/ films were characterized by FTIR (Fourier Transform Infrared), TGA (Thermogravimetry analysis), PXRD (Powder X-ray Diffraction), FESEM (Field emission scanning electron microscopy), UV-Vis (Ultra violet-Visible spectroscopy) etc. The XRD results show that the polycrystalline aluminium nitride obtained at temperature 1000oC and at 1Torr pressure. The average crystallites size calculated from XRD were in the range of 20-10 nm which decreases with increase of pyrolysis temperature. We have also conducted pyrolysis process under argon instead of nitrogen and found that the most of the nitrogen coming from urea for the formation of AlN but nitrogen atmosphere favour clean formation of AlN. The band gaps of deposited films were found in the range of 5.1-6.2 eV.
NiMoO4 nanorods of different properties were synthesized via facile and scalable hydrothermal route by varying the reaction time and temperature and the effect of synthesis parameters on their electrochemical performances was investigated. Optimization of the synthesis parameters was carried out based on the electrochemical performance. Experimental analysis revealed that NiMoO4 nanorods synthesized at 150 °C for 6 h showed optimum electrochemical performance with specific capacitance, as high as 594 Fg⁻¹ at 1 Ag⁻¹ current density due to greater mesoporous nature and optimum crystallinity index. NiMoO4//activated carbon asymmetric supercapacitor device was fabricated using the optimized NiMoO4 nanorods and characterized for the electrochemical performances. Specific capacitance of 66 Fg⁻¹ was obtained for the fabricated supercapacitor device at 1 Ag⁻¹ current density and 56% retention of the specific capacitance was observed after 1000 cycles. An energy density of 18 Whkg⁻¹ and power density of 704 Wkg⁻¹ were achieved at 1 Ag⁻¹ current density which offer great promise for supercapacitor application of this material.
The micron long carbon nanofibers were grown on the porous carbon beads in order to get an active surface for rapid immobilization of guest molecules. The fabrication of nanostructures by catalytic route in chemical vapour deposition on porous substrate was accomplished by controlled synthesis of iron nanoclusters on the surface of porous carbon beads. The challenges of catalyst nanoparticles diffusion into the porous substrate was addressed by using iron coordinated ligand complexes and optimized loading percentage of metal salts onto beads. The tethered bottom up surface processed carbon nanofibers onto the porous beads morphologies were established by structural characterizations. The protruding architectures of carbon nanofibers on the porous carbon surface were subjected to bacterial colony for analysing the efficiency of cell conjugation onto hairy structures particularly at a low concentration. The interfaces of immobilized bacteria on the textured surface were studied by varying pH and external physical stimuli to check the biofilm formation. The strategy of fabricating all carbon porous topologically controlled ‘nano on micro’ geometries to fast immobilization of guest molecules could be useful for developing an active disinfectant surface.
In this paper, we have quantified and investigated the effect of various sintering temperature on close-packed Silica Nanospheres (SNs) monolayers. SNs with diameters of 140, 175 and 220 nm were fabricated by an ef- fective and reliable spin-coating technique. The fabricated SNs monolayers were sintered up to 1200 °C and were analyzed from FESEM to investigate in details for local and extended transformations in their structural and morphological properties. A distinct "neck-formation" was observed and was quantified with different particle size distribution as well as surface packing density. It was observed that SNs monolayer undergoes intra-particle reformation in the form of shrinkage in individual SNs and compactification of growth domains, followed by inter-particle sintering. A geometrical model was developed to determine the curvature radius and inter- penetration depth thus enabling us to quantify the parameters that dominate the dynamics of the sintering process for such non-porous SNs.
- Jan 2018
This study is aimed to represent the role of carbonaceous nanofillers to reinforce the commercially available polyurethane porous structure. The effect of dimensionality of fillers to anchor the construction of stable 3D cellular architectures has been highlighted. The cellular frameworks of commercially available thermoplastic polyurethane (TPU) have been fabricated through the thermo-reversible supramolecular self assembly route. It was established that the minimum shrinkage of TPU lattice structures was occurred when the solid state network is strengthened by the topologically engineered 3D hierarchical nanofillers where the amount of reinforcement was found to play a critical role. It has been established by series of structure-property correlations that reinforcing the cellular structure to endure the capillary stress is equally effective as supercritical drying for producing low density porous morphologies. The removal of liquid phase from gel is as important as the presence of 3D fillers in the matrix for reinforcing the cellular structures while replacing the solvent phase with air to generate the two phase solid-gas engineered morphology. The insight into the PU network structure revealed that the dimensionality, amount and distribution of fillers in the matrix are critical for reinforcing the cellular scaffolds in solid gel without any crosslinking.
p class="p1">A comparison of Surface Enhanced Raman Scattering (SERS) activity of chemically synthesised silver nanostructures with different shapes is reported. The silver nanostructures of cubical, prism and wire like morphology were synthesised using chemical synthesis route and utilised as SERS substrates. The sensors were fabricated by spin coating these materials over a Silicon or glass substrate. The fabricated sensors were used to analyse response with two different analytes, 4-Mercaptobenzoic acid and Rhodamine 6G under different concentrations. The signal enhancement was compared with a silver coated thin film over glass substrate and it was observed that the enhancement of the order of 10 <sup>3 </sup> is achieved. The nanowire performed better than the other forms of silver and gave a higher signal enhancement for all the analytes as compared to other nanostructures. The fabricated sensors may be useful for various applications including explosive and biowarfare agent detection.</p
- May 2017
The interfacial debonding of graphite lattices by iron (Fe) nanoparticles and Fenton’s reagent were reported with an objective to scalable production of few layers graphene flakes. The acoustic cavitation by sonochemical route was adapted to produce iron and iron oxide nanoparticles in the graphite matrix. The oxygenated species were introduced into graphite lattice by physical method and then Fenton chemistry was utilized to generate localized hydroxyl radicals at the Fe nanoparticles-graphite interfaces for zipping and self exfoliation of defected graphite lattice. The functional groups were found to be introduced predominately at the periphery of the flake which ensure the lateral dimension of graphene is not affected and at the same time to achieve good dispersion in organic solvents. The defect engineering could be modulated at the organic-inorganic hybrid interfaces for controlling the zipping rate to regulate the degree of functionalization and the size of the lateral dimensions of the graphene sheet.
- Jan 2017
The thermal conductivity of graphene is limited in the transverse direction due to the exfoliation of the interplanar distance. In this study, the multiwalled carbon nanotubes (MWCNTs) with high thermal conductivities were immobilized into the exfoliated few layers graphene with an objective to enhance the transverse thermal conductivity of MWCNT embedded graphene three dimensional architectures. Reconstructing the topographically controlled synthetic hybrid nanostructure assemblies in polymer matrix provides the opportunity to insight into the electrical and thermal conduction mechanism. The thickness of the resin layer between the nanohybrid fillers was found to be critical for the phonon transport through the coating whereas this epoxy insulating layer prevents the tunneling for electron. By controlled functionalization and site specific orientations of hybrid nanoscale morphologies in the fiber reinforced composite, the higher mechanical strength could be achieved with increased electrical but reduced thermal boundary resistance of the matrix.
- Nov 2016
The catalytic efficiency of silver-nanoferns (Ag-NFs) decorated on carbon microfiber surfaces has been investigated. The Ag-NFs were grown on carbon microfiber employing electrodeposition technique using an electrolytic solution of aqueous silver nitrate and boric acid. The structure of grown Ag-NFs has nanoscaled sub-branches of size ≤ 50 nm that could be controlled by applied voltage and electrodeposition time. Using a specially designed home-made glass reactor, the catalytic efficiency of the Ag-NFs grown over carbon microfibers (cAg-NF) has been measured and tested for a model catalytic reaction of para-nitrophenol reduction mediated by sodium borohydride, both in batch and continuous flow modes of operation. The cAg-NFs have shown excellent catalytic activity with a normalized rate constant κ = 3.42 s-1g-1. The reusability for the cAg-NFs has been observed up to seven cycles of operation without much degradation in the catalytic efficiency. The integrated c-Ag-NF catalyst system and the designed reactors are simple and can be easily incorporated for facile effluent treatment or in other applications where catalytic reduction may be required.
An Electrocardiogram (ECG) is a graphic tracing of electrical patterns produced by the heart. This test is frequently used for patients who have heart problems and is an important diagnostic procedure. Standard ECG are recorded on paper has a grid on it. The grid work on ECG records is made up of many tiny blocks that are 1 mm square. Each of these tiny boxes is generally 40 ms duration. Heavier lines are used to make larger squares of five boxes tall and five boxes wide. Each larger square has a duration of 200 ms. Five of these larger squares (200 × 5) equals 1000 ms or 1 sec. By counting out the grids, we can get a fast approximation of the duration of a particular cardiac cycle or timing cycle. However this becomes increasingly complicated when we would like to analysis the ECG data for higher precision. The normal ECG record comprises a P wave, QRS complex, ST segment, and T wave. Analysis of each segment duration is very important for critical decisions by clinician. In view of this we have developed MATLAB based algorithm to read the ECG images, which has options to calibration in both X and Y axis, followed by algorithm to remove the background grids and extract the numerical coordinates of individual points of ECG curve. The numerical data extracted from ECG are highly useful for high precision diagnosis and the details are discussed in the manuscript.
- May 2016
Previous efforts to insert fullerenes into a carbon nanotube (CNT) involved the isolated synthesis of CNTs and fullerenes and then annealing CNTs and fullerenes together for encapsulation. We demonstrated the process for the continuous production of fullerene peapods inside the arc instrument by modifying the conventional arc ablation system, which can be repeated to obtain the desired mass scale product. Inside the arc discharge unit, by using the tunable external magnetic field, the double-walled CNTs (DWCNTs) were first synthesized and then directed to deposit onto the water cooled aluminium (Al) plate. The openings were created on DWCNTs by controlled heating of the Al plate and then fullerenes were synthesized and deposited on DWCNTs. In the arc instrument, fullerenes were finally directed to enter into DWCNTs from the defect sites by heating the Al plate in a vacuum. The formation of the peapod was established by the structure-property studies despite the huge deposition of metal catalyst nanoparticles and fullerenes on the surface of the nanotube which were a serious challenge for molecular level characterization of the grown peapod structures.
- Oct 2015
We report a novel approach for the fabrication of a user friendly functional device with dry electrodes for the measurement of biopotentials (electrocardiograph or ECG, electroencephalogram or EEG) that allows extended measurement time, reduced preparation time and less motion induced artifacts compared to wet gel based commercial electrodes. The dry micro-electrode arrays were fabricated by the UV maskless lithography in the grayscale or back-exposure modes using a biocompatible polymer SU-8. This produced conical shaped, mechanically robust micro-needles on a flexible polymer substrate which conforms to the body contours thereby greatly reducing the motion artifacts. The device was tested in vivo on human subjects and compared with the currently utilized wet gel based Ag/AgCl electrodes. It demonstrated comparable performance in capturing ECG and EEG signals. The electrodes were tested for long duration (48 h) without any signs of degradation. This device can be utilized for long term as well as remote health monitoring of the subjects.
- Jun 2015
The role of different functional groups and the nature of the functional group on multiwalled carbon nanotube (MWCNT) surface were thoroughly studied for silver nanoparticles (AgNPs) loading and on the mechanism of decontamination and disinfection. The surfactant free method for grafting of AgNPs on MWCNT surface followed by vacuum annealing was adapted to enhance the interfacial interactions of nanomaterials with bacteria. The best performing functionalized MWCNT was selected for the fabrication of functional composite membrane for further insight into the interfacial interaction of polymer-nanomaterials. It has been shown that at an optimized weight percentage loading of functionalized MWCNTs, nanotubes scaffolds were generated inside the pores of polysulfone membrane to sieve out toxic metal ions and bacteria by physical and chemical elimination without compromising the flux rate of filtration. The structure property relationship of the nanocomposite membrane has been thoroughly evaluated by the morphological, surface area and contact angle measurement studies. The modified surface of MWCNTs by Ag nanoparticles and polar functional groups placed on the pores of membrane was thus further exposed for the interfacial interaction with the decontaminated and disinfect water which in turn enhances the efficiency of filtration.
- Jan 2015
A scalable process has been demonstrated for the controlled functionalization and positional controlled buckling of multiwalled carbon nanotube (MWCNT) by selectively masking the nanotube surface with chemically inert and thermally stable ceramic material. A uniform thin layer of soluble ceramic precursor, polycarbosilane (PCS), was first coated on MWCNT by the modified solution based coating technique. The discrete silicon carbide (SiC) islands were then produced on nanotube surface during annealing at high temperature. The size and distribution of SiC islands on the surface of nanotube could be topologically regulated by controlling the thickness of PCS layer on MWCNT. The modulated surface of MWCNTs was then exploited for the site specific functionalization by guiding the incoming functional groups to the exposed surface. By optimizing the openings of the exposed surface of MWCNTs, the degree of chemical modifications could be tailored make. The controlled screening of nanotube surface has also been utilized for the physical modifications like selective buckling of tube walls by impinging high energy ions on MWCNTs where the position of bending under irradiation fluence could be customized by the degree of passivation of nanotube surface.
- Dec 2014
An easily dispersible multiwalled carbon nanotube (MWCNT) derivative is prepared, and provides a platform for the synthesis of the phenyl butyric acid methyl ester (PCBM) analog. The carbene addition reaction of MWCNTs makes derivatives that are less soluble in organic solvents; by exploiting this differential solubility, PCBM analogs can be separated from the unreacted functionalized MWCNTs. Our experimental evidences indicate that it is the unique properties of the butyric acid methyl ester moiety that makes the acceptor material perform better in organic photovoltaics (OPVs). Studying the combination of the butyric acid methyl ester moiety and the deagglomerated functionalized MWCNT structures provides us an insight into nanoscale charge transfer and transportation inside the donor–acceptor domain. It is demonstrated that a strong structure–property relationship exists for the functionalized MWCNTs, which enables us to correlate the functionality on the carbon nanostructures with performance in OPVs.
- Apr 2014
The present disclosure provides a composite and a process for preparation of said composite having high thermal conductivity and electrical resistivity. The composite exhibits high thermal conductivity and electrical resistivity.
- Mar 2014
A simple route is followed to produce an abundance of individual carbon nanotubes (CNTs) immobilized in graphitic layers to counter the challenge of locating individual CNTs and restrict the lateral displacement of CNTs due to the high electrostatic force exerted by a scanning tunnelling microscope tip for electrical characterization. Graphitic layers are selected for the embedding matrix as graphite and the nanotubes have a similar work function and hence would not perturb the electrical configuration of the nanotube. Solvent mediated exfoliation of graphite layers to insert the nanotubes was preferred over oxidative expansion, as oxidation could perturb the electrical configuration of graphite. During the exfoliation of graphite the optimized amount of nanotubes was introduced into the medium such that an individual nanotube could be immobilized in few-layer graphene followed by precipitation and centrifugation. The dose and the time of sonication were optimized to ensure that damage to the walls of the nanotubes is minimized, although the ultrasonication causes scissoring of the nanotube length. This procedure for immobilizing nanotubes in graphitic layers would be equally applicable for functionalized CNTs as well. The capability of embedding individual nanotubes into a similar work function material in an organic solvent, which could then be transferred onto a substrate by simple drop casting or spin coating methods, has an added advantage in sample preparation for the STM characterization of CNTs.
The surface of multi wall carbon nanotubes (MWCNTs) was first covalently functionalized with oleyl amine and then non-covalently wrapped with polycarbosilane (PCS). The hybrid functional groups were chosen to introduce different features in the MWCNTs properties. For covalent functionalization a long chain unsaturated aliphatic amine was used to simultaneously achieve the dissociation of MWCNT bundles along with the dispersion and interaction with the host matrix using the amide functionality and double bond. On the other hand, a thermally stable polymer was selected which can interact with both resin and glass fabric to promote interfacial adhesion. This hybrid doubly modified MWCNT is thus possesses duel advantages in glass fiber based epoxy composite. The pristine, covalent, noncovalent and covalent-noncovalent doubly modifiedMWCNT systems were used to study the viscoelastic behavior and interactions of functionalized MWCNTs in the matrix above and below the glass transition temperature of the matrix. The PCS coating on the MWCNTs is amorphous and thermally insulating whereas the nanotube is highly graphitized and thermally conducting. This contrasting behavior provides us to insight into the temperature dependant resin microstructure and curing thermodynamics of epoxy resin in the presence of MWCNTs.
- Jan 2014
A process for the fabrication of the polymeric membrane by using silver nanoparticles decorated functionalized carbon nanotube. The present invention relates to an economical and efficient process of fabricating porous polymer membrane by using silver nanoparticles decorated functionalized carbon nanotube without the use of surfactants for antibacterial and heavy metal removal with increased flux rate from contaminated water.
The present invention provides a method for continuous synthesis of fullerene encapsulated in carbon nanotube structure and corresponding apparatus thereof. The apparatus for continuous synthesis of fullerene encapsulated in carbon nanotube structure comprises an unique features of the multiple anodes on a rotating turret with the suitable external variable transverse magnetic field and an in situ heating arrangement for tailor make the bandgap and thermal conductivity of carbon nanotube by the incorporation of fullerene inside the carbon nanotube. The total time to complete one full cycle of the fullerene peapod structure is much less as compared to available conventional methods.
The present disclosure provides a process for producing a positionally controlled functionalized nanostructure, said process comprising: coating a nanostructure by a precursor material to obtain a coated nanostructure; annealing the coated nanostructure to obtain a nanostructure having a ceramic coating and exposed surfaces; adding functional groups preferentially to the exposed surfaces of the coated nanostructure by selectively screening the nanostructure by the ceramic coating to obtain a positionally controlled functionalized ceramic coated nanostructure; removing the ceramic coating from the positionally controlled functionalized ceramic coated nanostructure by sonication in at least one solvent to obtain a positionally controlled functionalized nanostructure. The present disclosure provides a process for a process for producing positionally controlled channels on a nanostructure, said process comprising: coating a nanostructure by a precursor material to obtain a coated nanostructure; annealing the coated nanostructure to obtain a nanostructure having a ceramic coating and exposed surfaces; impinging high energy ions optionally through a protector layer preferentially to the exposed surfaces of the coated nanostructure by selectively screening the nanostructure by the ceramic coating to obtain a positionally controlled ceramic coated channelized nanostructure; removing the ceramic coating from the positionally controlled ceramic coated channelized nanostructure by sonication in at least one solvent to obtain a positionally controlled channelized nanostructure.
- Jun 2012
The supramolecular assembly of the regioregular poly-3-hexylthiophene (rr-P3HT) in solution has been investigated thoroughly in the past. In the current study, our focus is on the enthalpy of nanofiber formation using thermal analysis techniques by performing the self-assembly process inside the differential scanning calorimetry (DSC) instrument. Thermogravimetric analysis (TGA) was carried out to check the concentration of the solvent during the self-assembly process of P3HT in p-xylene. Ultraviolet visible (UV-vis) spectophotometric technique, small-angle X-ray scattering (SAXS) experiment, atomic force microscopic (AFM), and scanning electron microscopic (SEM) images were used to characterize the different experimental yields generated by cooling the reaction mixture at desired temperatures. Comparison of the morphologies of self-assembled products at different fiber formation temperatures gives us an idea about the possible crystallization parameters which could affect the P3HT nanofiber morphology.
- Feb 2012
- Intelligent Nanomaterials: Processes, Properties, and Applications
In this chapter, we tried to bring out the role of organic and polymer chemistry to provide the much needed support in the development of organic photovoltaic (OPVs) devices with the new and fundamental researches on novel materials with tailor-made properties. A good understanding on the excited state reactivity of photoactive materials would help to prepare new materials and molecules capable of absorbing light over a given wavelength range and using it for driving energy or electron transfer. Scientifically and technologically well equipped chemistry community has explored the possibilities of developing and optimizing the charge separation in the light-harvesting architectures, however it is yet to bear fruit due to the difficulty of transportation of electrons and holes to the corresponding electrodes. Modeling charge mobility in organic semiconductors is complicated due to the presence of bulk heterogeneity in the macrostructure. The understanding of the interface between the metal electrode and the organic material, where charge collection takes place, is even more intriguing. In this chapter, we have highlighted the key features which enable to design new materials for the vast landscape of solar energy conversion and the some of our efforts towards material synthesis for OPVs.
- Jan 2012
- Germanium: Properties, Production and Applications
Fullerenes have unique cage-like structures, which creates a typical inner space. A range of metal atoms can be caught inside this space to form endohedral metallofullerenes. These new series of materials exhibit potential applications as new type of superconductors, organic ferromagnets, nonlinear optical materials, functional molecular devices, magnetic resonance imaging agents, energy conversion devices and biological tracing agents, etc. A great deal of experimental and theoretical studies have been focused on endohedral metallofullerenes of group III metals, most of the lanthanide series elements, group II metals, alkali metals and some tetravalent metals. However, no experimental and very few theoretical studies have so far been carried out on Ge which has a comparable atomic size and weight to that of metal ions inserted earlier in the fullerene cage. The atomic radius of Ge is slightly smaller than other reported endohedral metal atoms. However, it is big enough to get trapped inside the fullerene cage. In this chapter we would describe the process for encapsulating Ge in a fullerene cage by arcing method. Solvent extraction and then exploiting the differential solubility of metallofullerene and empty fullerenes in nitrogenous solvent were used to isolate metallofullerene from the starting carbon soot. The insertion of Ge inside the fullerene was proven by different experimental techniques. Confined metals inside the fullerene cage strongly interact with the bonding and antibonding orbitals of fullerene and drastically alter the electrical and conduction properties of pristine fullerene. Our theoretical studies suggest that the electronic properties of fullerene could be extensively modified by encapsulation of Ge. Density functional theoretic calculations using B3LYP parameterization and 6-31G* basis set suggest that Ge as well as Ge2 can be trapped inside C60. Rotational barrier calculations for Ge2 inside C60 indicate a cross over between singlet and Corresponding author. Tel.: +91 512 2451759-78; fax: +91 512 2404774/+91 512 2450404 E-mail address: email@example.com (Dr. Debmalya Roy). 2 triplet states of the complex with a variation in the orientation angle. The energy gap between the HOMO and LUMO of C60 is reduced significantly by the encapsulation of the guest species. Recently, the development of lightweight, flexible organic solar cells utilizing nanostructured materials has attracted a lot of attention. In the spectrum of solar irradiation, 5% of the total spectral wavelengths are from UV whereas 46% are from visible and 49% are from near IR region. Ge has a fairly good amount of absorption in the near IR region, therefore a range of absorption from UV, visible and NIR region could be achieved which leads to harvest more photons from sunlight and makes this metallofullerene potentially more efficient for photovoltaic application.
- Jan 2012
The present disclosure provides a process for synthesizing functionalized multi-walled carbon nanotubes (MWCNTs), comprising: refluxing MWCNTs with an acidic mixture to obtain a acid functionalized MWCNTs; and reacting the acid functionalized MWCNTs with oleyl amine in presence of an organic solvent to obtain an oleylamine derivative of MWCNTs. The present disclosure also provides a process for synthesizing a polycarbosilane coated MWCNT, comprising: mixing polycarbosilane and MWCNTs to obtain a mixture; stirring the mixture in Tetrahydrofuran, in presence of a catalyst under an inert atmosphere, to obtain a reaction mixture; and drying the reaction mixture under vacuum followed by heating to obtain polycarbosilane coated MWCNT’s. The present disclosure further provides the application of functionalized MWCNTs as synthesized in accordance with the present disclosure, for use in making photovoltaic devices and the application of polycarbosilane coated MWCNTs as synthesized in accordance with the present disclosure for use in making glass fiber reinforced epoxy composites.
- Jun 2011
The ligand [2-(1,2,3,4-thiatriazole-5-yliminomethyl)-phenol] (L) is a schiff base derived from condensation reaction of 1,2,3,4-thiatriazole-5-ylamine and Salicylaldehyde. Synthesis of the ligand (L) and the complex [Cu(II)(L)2]·2H2O have been studied in our previous work (Bharti et al., Asian J Chem 23(2):773–776, 2011). Thermal decomposition behavior of synthesized Cu(II) complex has been investigated by thermo gravimetric (TG) analysis at heating rate of 10 °C min−1 under nitrogen atmosphere. The mechanism of decomposition of Cu(II) complex has been established from TG data. Kinetic parameters such as order of reaction (n), activation energy (E a), frequency factor (Z) and entropy of activation (∆S ≠) were calculated by using Freeman and Carroll (J Phys Chem 62:394–397, 1958) as well as Doyle’s methods as modified by Zsako (J Phys Chem 72(7):2406–2411, 1968).
- Mar 2011
In this manuscript, synthesis and its application in energy conversion devices of nanostructured carbon materials like doped fullerene and functionalized doped fullerene with special emphasis on solar cell application has been discussed. An economical solar cell device can be developed using these materials as electron acceptor and nanofibers of conducting polymers as electron donor materials.
- Feb 2011
Schiff base ligand [2-(1,2,3,4-thiatriazole-5-yliminomethyl)-phenol] (L) was synthesized by condensation reaction of 1,2,3,4-thiatriazole- 5-ylamine and salicylaldehyde. 1,2,3,4-Thiatriazole-5-ylamine is derived from thiosemicarbazide. The synthesized ligand was found to be potential ligand towards transition metal ions. The reaction of copper(II) salt with Schiff base ligand (L) resulted in the formation of a solid complex [Cu(II)(L) 2].2H 2O. The ligand and the complex were characterized through elemental analysis, IR, UV-vis and 1H NMR spectroscopies. The thermal property of the complex was studied by thermogravimetric analysis.
- Dec 2010
Carbon fiber based carbon micro-flowers were produced using catalytic chemical vapour deposition technique on reproducible basis using specially designed nickel sulphide catalyst powder. The purity of the product is ∼95% as revealed by thermal analysis. Scanning electron microscopy analysis also confirms the absence of any impurities (e.g., amorphous carbon). Surface area analysis reveals a large surface area in the range 300-400 m2/gm with adsorption average pore diameter ∼5 nm. Possible uses are proposed.
- Apr 2009
Multiwalled carbon nanotubes (MWCNTs) have been coated with silicon carbide (SiC) using polycarbosilane as precursor in order to improve their thermo oxidative stability. The polycarbosilane coated MWCNTs were heated to ~1300°C under an inert atmosphere to generate the SiC coating. X-ray diffraction, energy dispersive X-ray analysis and scanning electron microscopy have confirmed the formation of SiC on the MWCNTs. The retention of the tubular structure of the MWCNTs has been confirmed by transmission electron microscopy. Thermogravimetric analysis has been performed to evaluate the thermo oxidative stabilities of coated and virgin MWCNTs. Sonication studies have shown that the mechanical strength of the MWCNTs was increased after coating with SiC. KeywordsPolycarbosilane-SiC-MWCNTs
- Jul 2008
Carbon nanotubes have attracted the fancy of many scientists worldwide. The small dimensions, strength, and the remarkable physical properties of these structures make them a unique material with a whole range of promising applications. In this review, the structural aspects, the advantages and disadvantages of different for their procedures synthesis, the qualitative and quantitative estimation of carbon nanotubes by different analytical techniques, the present status on their applications as well as the current challenges faced in the application field, national, in particular DRDO-DMSRDE status, and interest in this field, have been discussed.
- May 2008
Textile fibers reinforced with carbon nanotubes (CNT) show significant improvement in mechanical properties. Being lightweight and stronger than ordinary textile grade fibers, they can be used for different reinforcement applications. This paper reports a study on the comparison of the mechanical properties of composite fibers made of polypropylene (PP) and CNT obtained from different sources. A single walled nanotube from Carbolex USA, mutiwalled nanotubes from Iljin, Korea and DMSRDE Kanpur are used for the study. The composite fibers are made in two varieties viz. 0.5wt% and 1wt% concentration of CNT. It is observed that the mechanical properties, such as tenacity and modulus, increased with increased concentrations of the CNT irrespective of the brand and nature of the synthesis. The composite fibers made of multi walled CNT produced by DMSRDE give the best results in terms of spinnability and mechanical properties. The tenacity of the DMSRDE fibers is as high as ~9gpd and modulus as high as 114gpd.
- Oct 2007
Thermogravimetry (TG) is found to be a simple process to see the effect of the experimental condition on the some properties of synthesized carbon nanotubes (CNTs). A comparative study of thermogravimetry (TG) and derivative thermogravimetry (DTG) curves of CNTs, prepared under different experimental conditions is useful to investigate the influence of synthesis strategy on the thermal stability, yield and the nature of crystallinity of the CNTs. Single step in DTG profile under air atmosphere and high degradation temperature of sample in a TG curve shows the good quality and high yield of the CNTs. The samples of CNTs are prepared by CCVD of acetylene over Fe/Co and Fe/Mo in ratio of 1:1 by weight supported on aluminium isopropoxide (AIP) in the temperature range of 700–900 °C. The investigations from the TG curves help to optimize the experimental conditions for the synthesis of CNTs by CCVD method.
- Jul 2007
Carbon microcoils are generally prepared by catalytic chemical vapor deposition of acetylene, using Ni as the catalyst and thiophene as the promoter. In this work, a new catalyst has been developed on purpose to avoid the introducing of noxious and unpleasant thiophene during the reaction process. The products obtained at temperature of 740 degrees C were pure, regular and had perfect morphology. Scanning electron microscopy and Raman spectroscopy were employed to characterize the asprepared carbon microcoils.
- Apr 2007
Carbon microcoils are generally prepared by catalytic chemical vapor deposition of acetylene, using Ni as the catalyst and thiophene as the promoter. In this work, Ni-sulphide has been used as a catalyst for the purpose of avoiding the introduction of noxious and unpleasant thiophene during the reaction process and getting the thin film of quasi-aligned carbon microcoils. SEM images show that the products obtained in the temperature range of 740–760 °C were pure, regular and had perfect morphology.
- Jan 2007
The preparation of vapor grown carbon fibers (VGCF) by chemical vapor deposition (CVD) using hydrocarbon compounds as carbon source, was discussed. The microcoiled carbon fibers are synthesized with high yield and good reproducibility and have various applications such as in electromagnetic wave absorbers, electrode materials, and tunable devices. The preparation of carbon microcoils require toxic gases such as sulfur or phosphorus promoters and fine ball milled nickel sulfide particles were used as catalysts and acetylene was used as carbon source. SEM imaging technique determines the overall yield of carbon microcoiled samples and the Raman Spectroscopy and TEM analysis show that grown carbon microcoils were amorphous in structure and have the ability of easy scale ups.
- Jul 2006
A simple and reproducible procedure to obtain a 2D/3D alingment of multiwalled carbon nanotubes over a variety of substrates by CCVD methods, was analyzed. The principal advantage of this technique is that one can deposit a CNT film over a wide area. Another advantage is that by suitable controlling the mesh size and shape, different orientations of aligned MWNTs have been grown by the process. By suitably controlling the catalyst particle diameter and depositing it over a commercially available metal wire/support, different orientations and designs of CNT films were synthesized on reproducible basis. The films produced can be used for the study in the various types of CNTs based sensors.
- Apr 2006
We have developed low dielectric material using carbon nanotubes and measured its microwave‐absorbing properties. Its mechanical properties have also been investigated. Measurement showed that tensile strength increases by 23% and tensile modulus increases by 36%. A plausible explanation for high increase of mechanical properties has also been discussed.
- Mar 2006
Fullerenes have cage‐like structures, which leads to a typical inner space. A range of metal atoms can be trapped inside this space to form endohedral metallofullerenes. These new series of materials exhibit potential applications as new types of superconductors, organic ferromagnets, nonlinear optical materials, functional molecular devices, magnetic resonance imaging agents, and biological tracing agents, etc. A great deal of experimental and theoretical studies have been focused on endohedral metallofullerenes of Group 3 metals (Sc, Y, La), most of the lanthanide series elements, Group 2 metals (Ca, Sr, Ba), alkali metals (Li, Na, K, Cs), and some tetravalent metals (U, Zr, Hf). However, no theoretical or experimental studies have so far been reported on Germanium (Ge), an intrinsic semiconductor, which has a comparable atomic size and weight with metal atom inserted in the Fullerene cage. In this paper, we discuss the physical properties of Ge doped C82 metallofullerene. As it is suggested by theoretical calculation that metallofullerenes with C82 and C2V symmetry show maximum stability, so all the calculations here are carried out with C82 Fullerene with C2V symmetry. Theoretical calculations have been done on mono, di, trimetallofullerenes with one, two and three metal atoms and their respective electronic structures have also been studied.
- Sep 2005
A simple method to synthesize double-helical carbon microcoiled fibers by catalytic chemical vapor deposition (CCVD) route in absence of any electromagnetic/microwave field was presented. Correct amount amount of Ni powder was taken on a quartz boat, and was placed in the central zone of the electrically heated horizontal furnaces. The reaction temperature was kept at 1100°C, and acetylene and thiophene vapors were allowed to flow through the furnace. The SEM images showed that the yield was about 85-90%, the sample was quite pure, and the coils diameter was between 3 and 4 μ.
- Dec 2004
The coiled/straight carbon nanofibers (CNF) were synthesized using catalytic chamical vapor deposition. Cobalt acetate tetrahydrate was used as a catalyst with magnesium oxide as support, for synthesizing CNFs. Submicron sized Ni powder was chosen as catalyst, for the synthesis of carbon nanocoiled fibers (CNC). It was found that the larger the anisotropy, the greater the degree of coiling/twisting and the coil diameter and smaller the anisotropy, the smaller the degree of coiling/twisting and the coil diameter.
- Jan 2004
A simple and novel method was developed for efficient synthesis of 2D quasi-aligned multiwalled carbon nanotubes by a catalytic chemical vapour deposition technique. The CNT alignment and in depth analysis of structures has been studied by scanning electron microscopy and transmission electron microscopy. The growth rate and the purity of the product have been found to be affected by the flow rates of the gases as well as the nature of the support used.
- Jun 2003
Alignment or patterning of carbon nanotubes (CNTs) is particularly important for fabricating functional devices such as field emitters, nanophotonics, nanoelectronics, and ultrahydrophobic materials. This work reports on the synthesis of 2D quasi-aligned carbon nanotube bundles by catalytic chemical vapor deposition (CCVD) method using a series of catalysts and a study of their performance in a nutshell.
- Jul 2002
The effect of the sonication time on the structural features of carbon nanotubes. Conversion of carbon nanotubes into carbon nanofibers by sonication was performed. The nanotubes were prepared by the catalytic chemical vapor deposition (CCVD) over Fe and Co incorporated in a zeolite support. Low resolution transmission electron microscopy (TEM) images of prepared carbon nanotubes showed the quasi-parallel alignment and homogeneity of the nanotubes. A greater than 4-h sonication was found to destroy graphitic layers in the sample.
- May 2002
An effective method of growth by catalytic chemical vapor deposition (CCVD) to get a large-scale yield of carbon nanotubes is reported. In this method, acetylene is decomposed catalytically over well-dispersed metal particles (Co-Fe and Co-Ni) embedded in commercially available zeolite at a lower temperature (600-700 degrees C). The two binary-metal catalysts (Co-Fe and Co-Ni) used are compared by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Crucial reaction parameters, such as reaction time, temperature, and the effect of purity of gas to obtain optimum production of the nanotubes, both qualitatively and quantitatively, are also reported.
- Mar 1999
Considerable attention has been focused on the growth of carbon-based films or fibers by various methods. Diamond-like carbon (DLC) films may be of greater importance in some specific electronic applications such as flat panel displays, which represent a very large market. In this study, carbon-based thin films and fibers obtained from doped camphor soot were studied by confocal microRaman spectroscopy at 632.8nm.Different contributions were identified between 1000 and 1650cm−1 in the Raman spectra of the as-grown and laser-annealed films and fibers. The contributions were the D-like and G-like peaks of polycrystalline graphite at about 1345 and 1530cm−1, respectively, with a FWHM value about 5 times larger than in a:C. It is now well established from correlation between Raman signature and grain size measurements that the width of the Raman line is a decreasing function of the graphite grain size. From these results, one can estimate that the grain size of this polycrystalline graphitic phase was small. An additional feature is observed at about 1240cm−1 which could be due to sp3-bonded carbon clusters.
- Jan 1999
Considerable attention has been focused on the growth of carbon-based films or fibers by various methods. Diamond-like carbon (DLC) films may be of greater importance in some specific electronic applications such as flat panel displays, which represent a very large market. In this study, carbon-based thin films and fibers obtained from doped camphor soot were studied by confocal microRaman spectroscopy at 632.8 nm. Different contributions were identified between 1000 and 1650 cm−1 in the Raman spectra of the as-grown and laser-annealed films and fibers. The contributions were the D-like and G-like peaks of polycrystalline graphite at about 1345 and 1530 cm−1, respectively, with a FWHM value about 5 times larger than in a:C. It is now well established from correlation between Raman signature and grain size measurements that the width of the Raman line is a decreasing function of the graphite grain size. From these results, one can estimate that the grain size of this polycrystalline graphitic phase was small. An additional feature is observed at about 1240 cm−1 which could be due to sp3-bonded carbon clusters.
Spherical carbon nanobeads (solid and hollow) of two sizes of around 500–850 nm (large) and 250 nm (small) were synthesized by pyrolysing camphor vapour at 1000 °C in an argon atmosphere, using ferrocene, as catalyst, for the first time. The EEL spectrum suggests the carbon beads to be non-graphitic and these are covered by a graphitic shell of 80–100 nm, revealed by transmission electron microscopy (TEM) micrographs. The larger beads, more than 10 are interconnected by the outer shell. After covering the train of carbon, the beads take the shape of fibrous graphitic carbon which perhaps gives the spongy elastic character to the material. The average surface area of the nanobeads determined by BET studies is calculated to be 16 m2g−1. It is suggested that this material may be a useful anode for secondary lithium ion batteries.
Semiconducting carbon-based thin films obtained from camphor soot were studied by microRaman spectroscopy with a laser wavelength of 632.8 nm. Different spectral contributions were identified between 1000 and 1650 cm−1 and discussed. The contributions are the D-like and G-like peaks of polycrystalline graphite at ~1345 and 1530 cm−1, respectively, with a FWHM value ~5 times larger than in a:C, and an additional feature at ~ 1240 cm−1 due to tetrahedrally-coordinated carbon of camphoric soot. Spectra obtained were typical of DLC materials with small size sp3 clusters. This material seems to be suitable for flat panel display application using field emission by cold cathode. Thermal annealing by laser light induced a modification in the Raman spectrum. A band appears at 1591 cm−1, close to the peak associated with the in-plane stretching mode of sp2-hybridized carbon atoms (crystalline graphite phase). Thick (20 μm) and thin (1 μm) fibers were obtained from camphor pyrolysis. Raman spectra were similar to those obtained with laser annealed thin films.
- Apr 1998
We compare photoexcitation dynamics in films of pristine and C60-mixed 2,5-dioctyloxy poly(p-phenylene vinylene) (DOO–PPV) using ps transient and cw photoinduced absorption (PA), and PA-detected magnetic resonance (PADMR). We conclude that C60 doping is relatively inefficient in DOO–PPV. Consequently, the instantaneous exciton photogeneration yield remains high (close to 1) even at high C60 concentrations. However, as the C60 concentration increases up to 10 molar percent, the stimulated emission lifetime and cw photoluminescence intensity decrease together by about an order of magnitude due to dissociation of the singlet excitons at C60 related defect centers into intrachain polaron pairs, which were identified by PADMR.
- Dec 1997
This communication is a report of our preliminary effort to make a photovoltaic cell from semi-conducting n- and p-type carbon obtained from camphor soot as a confirmation of developing a semi-conducting carbon of low band gap
- Nov 1997
Thin films of camphoric carbon, a natural source, have been deposited on a single crystal Si (1 0 0) surface, 2° off towards[0 1 1] and quartz/glass substrates, at room temperature, by both electron and ion beam deposition. The crystal structure, composition analysis, surface morphology and other optical properties of these films have been studied using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), optical and scanning electron microscopy (SEM), atomic force microscopy (AFM) and UV-visible reflectance/transmittance spectroscopy. Carbon photovoltaic cells have been made and our preliminary investigation of photovoltaic characteristics of a cell of configuration B-doped C (100 nm)/P-doped C (100 nm)/n-Si (380 μm) by electron beam deposition reveal short-circuit current of 1.2 mA cm−2 and an open circuit voltage of 102 mV with fill factor of 0.82, at AM1 condition. The low band gap (1 eV) and the semiconducting nature of these camphoric carbon films indicate the future scope of low-cost and high-efficiency carbon photovoltaic solar cells.
- Jul 1997
Diamond-like carbon (DLC) film has been deposited, for the first time, from the soot of camphor, a natural source, by a simple vacuum deposition technique. This method of deposition is simple, convenient and much faster than the conventional gas cracking technique usually adopted for the DLC film deposition. The DLC thin film is characterized by Raman, Fourier transform IR, solid state 13C NMR, electron spin resonance and scanning electron microscopy (SEM). Preliminary results (X-ray diffraction and SEM analyses) suggest that polycrystalline diamond film may also be obtained from this source.
- Jun 1997
Glassy carbon has been synthesized for the first time by a simple pyrolysis experiment. The glassy carbon from camphor has been characterized by XRD, Raman, FTIR, ESR and SEM/AFM techniques. It has been found that the undoped glassy carbon film has a resistance of less than about 1 Ω and has n-type character. However, when it was doped with boron by a conventional vapour growth process, its resistance increased to the range 3.5 Ω–14.5 kΩ, depending upon the concentration of boron incorporated, and the resulting material has p-type character, hence showing a semiconducting behaviour unlike the undoped film which has metallic character.
- May 1997
Diamond-like carbon film (DLC) has been deposited from the soot of camphor, a natural source, by a simple vacuum deposition technique, for the first time. This method of deposition is simple, convenient and much faster than the conventional gas cracking technique usually adopted for the DLC film deposition. DLC thin film is characterized by Raman, FTIR, solid state C NMR, ESR and SEM. Preliminary results (XRD and SEM analyses) suggest that the polycrystalline diamond film may also be obtained from this source. The prime novelty of this work is that from the same source, we have been able to synthesize both DLC film as well as polycrystalline diamond film by a simple vacuum deposition technique without using any external gas like the conventional chemical vapour deposition (CVD) methods.
- Jan 1997
A photoelectrochemical solar cell from camphoric p-carbon semiconducting pellet has been developed for the first time from the soot of a natural source, camphor. This semiconducting camphoric carbon is unusually stable both in acidic and alkaline media. Preliminary findings show that the semiconductor has band gaps (Eg 2.28 eV direct and 1.28 eV indirect) suitable for solar energy conversion. PEC properties are also being discussed.
- Dec 1996
Semiconducting carbon tubules (n- and p-type) of band gap 1.96−1.98 eV have been synthesised from the soot of naturally occurring camphor for the first time. The mechanism of the formation of multichannel-multilayered camphoric tubules is discussed. Tubules are characterised by SEM, AFM, TEM, XRD, ESR, FTIR and electrical conductivity studies.
- Jun 1994
Fullerenes are prepared from a natural source, camphor, for the first time. The films are deposited on a Si substrate, by a vacuum evaporation technique from the toluene extract of ether insoluble camphor soot. A fast atomic bombardment mass spectrum shows the presence of C60 along with other members of the fullerene family. Crystalline fullerene thin films grown on a Si wafer have been investigated by x-ray diffraction and scanning electron microscopy (SEM). X-ray diffraction measurements have identified that the crystals of C60 have the hexagonal close packed structure. SEM pictures reveal the surface distribution of spherical C60 clusters.
C"SUB 60" and other members of the fullerence family have been isolated by vacuum evaporation technique from the toluene extract of either insoluble camphor soot for the first time. Also, with the help of hot filament chemical vapour deposition technique, under the optimized conditions, we are able to avoid the tedious chromatographic separation method. Fast atom bombardment mass spectroscopic studies and scanning electron micrographs reveal the presence of C"SUB 60" , a few smaller fullerenes and fullerence-based tubules of various sizes (0.14-1.15 mm). (Authors)