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Boron carbide (B4C) based composites with graphene nano-platelet (GNP) as reinforcement have been prepared by hot pressing. Effect of GNP addition on mechanical properties of the composite, like, hardness, fracture toughness, flexural strength was evaluated. Phase evolution was studied by X-ray diffraction (XRD) and Raman spectroscopy. 2 vol% addition of GNP improved the density of the composite, which acted as a sintering aid. Further addition of GNP resulted in formation of the interconnected networks, agglomerates and interfacial porosities. Improved fracture toughness (KIC) but decreased flexural strength was observed with addition of GNP. Maximum fracture toughness of 5.41 ± 0.55 MPa m1/2 (by indentation method) and 4.52 ± 0.15 MPa m1/2 (by single edge notch bend (SENB) method) was obtained for 10 vol% GNP-B4C composite. Hardness and elastic modulus were also improved with 2 vol% addition of GNP. The observations have been explained with suitable mechanism and model, supported by microstructural and mechanical property data.

SiC nanowire and dense SiC, grown in-situ in a carbon fiber perform play crucial role in determining oxidation resistance of composite. The composite shows three regimes of oxidation, first two being weight loss (Temperature: 763–933 K and 933–1073 K) and the third (1073

We report the development of an ultrasensitive label-free DNA biosensor device with fully integrated standalone carbon nanotube (CNT) aerogel electrode. The multi-directional tenuous network of clustered CNT embedding into the CNT aerogel electrode demonstrates linear ohmic and near isotropic electrical properties, thereby providing high sensitivity for nucleic acid detection. Using this device, the target DNA hybridization is detected by a quantifiable change in the electrochemical impedance, with a distinct response to the single-stranded probe alone or double-stranded target-probe complex. The target DNA is specifically detected with limit of detection (LoD) of 1 pM with a turnaround time of less than 20 min, which is unprecedented for a miniaturized CNT aerogel sensor and impedance spectroscopy without an intermediate DNA amplification step. Moreover, this system is able to differentiate between the closely related target sequences by the distinct impedance response rendering it highly specific. To the best of our knowledge, this is the first report showing the use of standalone bare CNT aerogel electrode without any substrate support, coupled with electrochemical impedance spectroscopy, for the detection of DNA hybridization. Altogether, the results show that our system is fast, sensitive and specific for label-free rapid direct DNA detection, promising a novel avenue for bio-sensing.

Herein, sorption of pentavalent neptunium from aqueous acidic solution was carried out onto 1st and 2nd generation of poly(amidoamine) dendrimer functionalized MWCNTs. The Np(V) sorption kinetics followed pseudo second order kinetics with rate constants of 1.4 × 10−4 and 6.84 × 10−4 g mg−1 min−1 for MWCNT–PAMAMG1 and MWCNT–PAMAMG2, respectively. The sorption of Np(V) onto MWCNT–PAMAMGn proceeded via chemisorption and the data fitted well to Langmuir isotherm model. MWCNT–PAMAMGn was found radiolytically stable up to 500 kGy dose of gamma radiation. Sodium carbonate was found to strip Np effectively from sorbent.

A carbon nanotube fiber is formed by interlocking carbon nanotubes that are perfectly aligned to give a continuous long fiber. The production of neat carbon nanotube fibers has paved the way for realization of superior mechanical and physical properties of individual carbon nanotubes at macroscopic scale. In this review paper, we elucidate the state of the art advances in fabrication methods, characterization, modeling of mechanical properties, and applications of carbon nanotube fibers as next generation high performance fibers for composites. Recommendations have been made on the aspects of design and scale-up for large scale manufacturing of carbon nanotube fibers using (a) a stepwise protocol for the determination rate controlling step(s) and the estimation of overall rate of reaction, and (b) computational fluid dynamics. Finally, the challenges and opportunities in carbon nanotube fiber research have been clearly brought out, and suggestions have been made for future work.

Nitrogen doped carbon nanotubes has been synthesized using imidazole and acetylene in a fixed bed reactor by catalytic chemical vapour deposition. Ferrocene was used as a catalyst dispersed on magnesium oxide as a support. Imidazole acted as both carbon and nitrogen source and acetylene was used as an additional carbon source to tune the nitrogen content and increase the productivity. The temperature, flow rate of the reactants, particle size of the support, and height of the boat and partial pressure of acetylene were varied to understand their effect on the rate of formation of nitrogen doped carbon nanotubes. A plausible reaction mechanism was proposed to predict the rate determining step of the reaction and it was found that saturation and supersaturation of the nitrogen doped carbon nanotubes was rate determining. Temperature studies showed surface reaction can be possibly controlling the reaction rate with activation energy of 114 kJ mol −1 . Average particle size of >91 µm depicted pore diffusion control. The products have been characterized by electron microscopy, thermogravimetry, Raman spectroscopy, carbon-hydrogen-nitrogen analysis and surface area analysis.

Feasibility of synthesis of Platinum/Multiwall Carbon Nanotube (Pt/MWCNT) nano-composites has been evaluated using a green chemical approach in the task specific ionic liquid (TSIL), trioctylmethyl ammonium hydrogen phthalate (TOMAHP). Effects of reaction temperature and introduction of functional groups in MWCNT on the dispersion of Pt onto MWCNT have been studied during synthesis. The Pt/MWCNT nano-composites thus prepared have been characterized for their structures, compositions, sizes and morphologies using X-ray diffraction (XRD), small-angle X-ray scattering (SAXS) and transmission electron microscopic (TEM) techniques. The high resolution transmission electron microscopy (HRTEM) and SAXS study showed that the fcc Pt nanoparticles (NPs) prepared at 40 °C are finely dispersed having average particles size of∼3–5 nm. However, most of them were not deposited onto the surface of pristine MWCNT. When functionalized MWCNT was used instead of pristine one, the Pt NPs formed agglomeration and there was wide size distribution. Increase in reaction temperature from 40 °C to 80 °C leads to formation of well dispersed Pt NPs on pristine MWCNT surface with particle size of 1–3 nm. A possible mechanism for formation of Pt/MWCNT in TSIL medium has been discussed.

Few layered graphene (FLG) was synthesized by substrate-free floating catalyst chemical vapour deposition method for the first time. A sensor prepared from the pristine FLG coated over a glassy carbon electrode without further modification showed high sensitivity towards sensing of H 2 O 2 (355 μA mM −1 cm −2 ) with lower detection limit of 0.27 μM and response time of 5 s. Transmission electron microscopy revealed 3–5 layers of graphene sheets with edge defects, which was supported by Raman spectroscopy. X-ray photoelectron spectroscopy confirmed that the defects are due to oxygen present in the FLG in the form of C O, that played important role in sensing.

Synthesis and characterization of nano-structured porous granules, with fairly defined morphology and porosity, is crucial because such granules are widely utilized for various technological applications. However, an easy, one-step, economic synthesis protocol for large scale production is extremely desirable. In the present work, we have reported the synthesis and characterization of the nano-structured micro-granules using aerosol drying of bi-colloidal suspension of nano-silica and milk. Removal of soft organic component from the granules results in formation of meso and macro pores with moderate specific surface area. Granule morphology and porosity depends strongly on the concentration ratio of the individual components in the drying aerosol as well as the interaction between them.

The present investigation demonstrated the efficient sorption of NpO 2 + and NpO 2 2+ on amidoamine functionalized multiwalled carbon nanotube via chemisorption following Langmuir isotherm. A pseudo second order kinetics were found to follow with the rate constant 5.13 × 10 −4 and 3.85 × 10 −4 mg g −1 min −1 for NpO 2 + and NpO 2 2+ , respectively. The radiolytic stability of the sorbent and the back extraction of the neptunium from the sorbent have been investigated. Computational study was also carried out to optimize the structure of the amidoamine functionalized carbon nanotube and its complex of NpO 2 + and NpO 2 2+ . The amidoamine and all the nitrate anions are coordinated to the neptunyl centre in bidentate mode resulting to six-coordinated and octa-coordinated complex for NpO 2 + and NpO 2 2+ , respectively. The theoretically calculated value of ΔG of NpO 2 2+ sorption is found to be higher than that of NpO 2 + which is in good congruence with the experimentally observed higher adsorption capacity for NpO 2 2+ over NpO 2 + .

Amidoamine functionalized multi-walled carbon nanotubes (MWCNT-AA) have been prepared and characterized. Separation of mercury(II) ions from aqueous solution by solid-liquid extraction has been investigated using the synthesized material as an adsorbent. Batch adsorption studies as a function of pH, contact time, initial metal ion concentration, and temperature have been carried out. The best fit for the adsorption equilibrium data was observed with Redlich-Peterson isotherm model and the kinetics data showed superior fitting for pseudo second order model, signifying chemisorption. The adsorbent showed superior selectivity with high adsorption capacity towards mercury as compared to other metal ions present in industrial waste water containing mercury. The MWCNT-AA was successfully used for six adsorption-desorption cycles without significant loss of uptake using 0.05 M EDTA as desorbing agent. A small scale fixed bed column study was demonstrated to test the scale up application. DFT theoretical calculations establish the bi-dentate mode of complexation and correlate the experimental selectivity.

Nitrogen atoms were successfully doped into the lattice of carbon nanotubes (hereafter called N-CNT) by chemical vapor deposition in a fluidized bed reactor using a solid precursor Imidazole. X-ray Photoelectron Spectroscopy estimated that ∼5.4 atom% of nitrogen was doped in the synthesized CNTs. The successful formation of N-CNTs was also confirmed by Fourier Transforms Infrared Spectroscopy. Transmission electron microscopy revealed the morphological features of N-CNTs and their changes with temperature. The use of fluidized bed resulted in the formation of uniform nature of N-CNTs. In-depth studies of influence of nitrogen doping in CNTs for hydrogen storage was studied by comparing with bare CNTs, also synthesized by a the same fluidized bed reactor. The hydrogen storage capacity for N-CNTs (0.8 wt.%) was enhanced significantly at very low temperature (163 K), compared to bare CNTs (0.28 wt.%).

Poly(amidoamine) dendrimer functionalized carbon nanotube was demonstrated as highly efficient sorbent of the Pu4+ from radioactive waste solution. The second generation dendrimer was found to have more efficiency as compared to the 1st generation might be due to the availability of more functionality for coordinating to the Pu4+ ion. Analysis of different isotherm models revealed that, Langmuir isotherm was predominantly operating through chemi-sorption (with the sorption energy 10.07 and 16.95 kJ mol−1 for 1st and 2nd generation dendrimer) with the sorption capacity 89.22 mg g−1 and 92.48 mg g−1 for 1st and 2nd generation dendrimer, respectively. Analysis of different sorption kinetics model revealed that the sorption proceeded via pseudo 2nd order reaction. The 2nd generation dendrimer was found to be radiolytically more stable while oxalic acid was found to be suitable for quantitative back extraction of Pu4+.

Diglycolamic acid-functionalized carbon nanotubes were employed for the efficient and selective separation of Pu4+, PuO22+ and Am3+. The sorption occurred through monolayer coverage via chemisorption following the Langmuir isotherm. The sorption of Am3+, Pu4+ and PuO22+ on DGA-CNTs proceeded via a pseudo-second-order rate kinetics with a rate constant in the order Am3+ < Pu4+ < PuO22+. The radiolytic stability for DGA-CNTs and the stripping behaviour of DGA-CNTs were investigated. Luminescence investigations revealed the presence of single species without an inner-sphere water molecule. On complexation, the asymmetry around Eu3+ was found to be enhanced along with the covalency of the metal–ligand bond. Additionally, DFT calculations were performed to investigate the coordination and complexation interaction behaviour of CNT-DGA towards the metal ions. The present DFT study revealed a tridentate coordination mode of the DGA moiety towards Pu4+ and Am3+ and a bidentate coordination mode towards PuO22+. The calculated binding energy of sorption with DGA-CNTs towards Pu4+ was found to be higher than that of PuO22+, in both the gaseous and aqueous phase, whereas for Am3+, it was higher than that for PuO22+ but less than that for Pu4+. The free energy of sorption was also found to be highest for Pu4+ uptake and lowest for PuO22+, in both the gaseous and aqueous phase.

Photoelectrochemical performance of bismuth vanadate (BiVO4) photoanode is limited by poor charge separation and transport properties. The roles of carbon nanotube, reduced graphene oxide, or graphitic carbon nitride in BiVO4 composite photoanode were investigated toward enhancing light absorption and reducing overall impedance during photoelectrochemical water oxidation process. X-ray diffraction and Tauc analysis showed that BiVO4 retains its monoclinic phase, n-type semiconductor nature, and band gap in all carbon nanomaterials-incorporated composite photoanodes. It was observed that the carbon nanomaterials incorporation in BiVO4 film increases its surface porosity, ultimately leading to enhanced light absorption. The BiVO4 photoanode with reduced graphene oxide and graphitic carbon nitride showed same bulk charge separation efficiency, whereas the latter showed better charge transfer. It was found that the graphitic carbon nitride formed composite with BiVO4 to provide enhanced light absorption efficiency, i.e., 89% in 350-505 nm range. The BiVO4 with graphitic carbon nitride photoanode showed the best performance with a photocurrent of 2.2 mA cm-2, charge separation efficiency of 67%, and photocurrent of 4.0 mA cm-2 with cobalt-phosphate surface catalyst at 1.23 VRHE for water oxidation under 1 sun illumination. The Mott-Schottky and impedance measurements confirmed the shift of conduction band position toward hydrogen reduction potential and reduction in film resistance, respectively, with carbon nanomaterials addition, and the shift was most significant for graphitic carbon nitride. It is concluded that by concomitant formation of junction during photoanode fabrication between carbon nanomaterials, BiVO4, and fluorine-doped tin oxide glass substrate, better charge separation, transport, and light absorption can be achieved.

The degradation of polymer matrix composite material during carbonization and the processing temperature are some important deciding factors to evaluate the performance of carbon–carbon composite (CC) for the targeted applications. In present study, the carbonization of material at the temperature range of 1200–1500 °C is considered as a critical step for understanding the material performance, as it is essential for the progress in the processing of CCs. The heat, mass and momentum transport equations are used with weight loss kinetics to develop a numerical simulation model for the carbonization process. Afterward, to solve the governing equations, a 2-D finite difference method (FDM) is employed. Using material properties, the developed numerical model predicts the distribution of pressure, porosity, density, specific heat, thermal conductivity as a function of surface temperature for square samples of various thicknesses at different heating rates. The comparisons of the results of the 2-D model are carried out with results of 1-D FDM model published earlier.

Efficient interfacial interaction between MoS2 nanosheets and functionalized carbon nanotube (CNT) has been achieved via adopting an engineered, but facile hydrothermal process using ammonium hepta molybdate and thiourea as precursors. The importance of the route lies in enabling strong and easy coupling between Mo7O246− anion and functionalized CNT at low pH, since the zeta potential of CNT has been found to be positive at low pH. The strong interfacial interaction between MoS2 and CNT enhances the overall electronic conductivity and structural stability which leads to better electrochemical performance. The as-developed composite, with just ∼8% carbon, possesses high Li-storage capacity, excellent rate capability and good cycle-life. Impedance spectra indicate least charge transfer resistance in the case of CNT-containing composites, with post-cycling Scanning Electron Microscopic (SEM) images confirms maintenance of integrity after repeated cycling. The cyclic voltammograms, along with x-ray diffraction and Extended X-ray Absorption Fine Structure (EXAFS), confirm that during lithiation step, MoS2 gets converted to Li2S and Mo via formation of LixMoS2 (0

A novel one step green chemistry approach utilizing trioctylmethyl ammonium hydrogen phthalate (TOMAHP), task specific ionic liquid has been attempted for synthesis of Ag and Pt nanoparticles supported on silica (Ag@mSiO2 and Pt@mSiO2). Structure, size distribution and morphology of these nano-composite particles were evaluated using X-ray diffraction (XRD), transmission electron microscopy (TEM), small angle neutron scattering (SANS) as well as small angle X-ray scattering (SAXS) techniques. The XRD results show that Ag/Pt metal nanoparticles deposited on to SiO2 surface are face center cubic (fcc) in nature. The TEM and SAXS/SANS results show the morphology and size distributions of Ag and Pt nanoparticles loaded on to the surface of SiO2. It has been found that Ag nanoparticles are well dispersed on to the SiO2 surface and are quite monodisperse in size, whereas Pt nanoparticles are quite polydisperse in size and forms aggregate or chain like structure on SiO2 surface containing primary nanoparticles of typical size range 3–7 nm. The stability of nanoparticles, which controls its dispersion on SiO2 substrate, has been discussed.

There is a huge requirement for development of a coating technique in nuclear industry, which is environmentally safe, economical and applicable to large scale components. In this view, simulation of gas-phase behavior in specially designed CVD reactor was carried out using computational tool, COMSOL. There were two important zones in CVD reactor first one is precursor vaporization zone and second one is coating zone. Optimized parameters for coating were derived from the simulation of gas phase dynamics in both zone of CVD reactor. The overall effect of fluid velocity, heat flow and concentration profile showed that Re = 54 is the optimum reaction condition for uniform coating in CVD system. In CVD coating experiments a synthesized halogen free, non-toxic and non-corrosive silicon carbide precursor was used. Uniform coating of SiC was obtained on zircaloy substrate at 900 °C using as synthesized organosilicon precursor. The X-ray diffraction and scanning electron microscopy analysis show that dense nano crystalline SiC film was deposited on zircaloy substrate.

The present paper reports an environmental benign process for the selective adsorption of Nd(III) in presence of Fe(III) on functionalized multiwalled carbon nanotubes (MWCNT) from a synthetic aqueous solution, which can be utilized for the rare earth recovery from scraps or end of life products. Effects of metal ion concentration, aqueous phase acidity (pH), weight of MWCNT, temperature, complexing agents and contact time on the adsorption of Nd(III) and Fe(III) over MWCNT have been studied in detail. The Nd(III) adsorption followed Langmuir isotherm in presence of Fe(III)and showed favourable adsorption at pH 3. The maximum adsorption capacities for Nd(III) and Fe(III) were found to be 44 mg/g and 30.8 mg/g respectively. Pseudo second order kinetics was followed by both Nd(III) and Fe(III) adsorption on MWCNT. For selective adsorption, ascorbic acid was found to be the best among different complexing with a selectivity coefficient of 120 for Nd(III) with respect to Fe(III). The adsorbed ions could be fully desorbed with 0.2 M HCl, indicating the process feasibility in terms of ease of recovery of loaded metal ions as well as regeneration of functionalized MWCNT. This process eliminates the use of hazardous organic solvents for the recovery of rare earths.

Amido amine-functionalized multi-walled carbon nanotubes (MWCNT-AA) were used for efficient and selective solid phase separation of plutonium(IV) and plutonium(VI). Langmuir, Freundlich, Dubinin–Radushkevich (D–R), and Tempkin isotherms were employed for understanding the sorption mechanism and Lagergren first order kinetics, an intra-particle diffusion model, and pseudo second order kinetics were applied to understand the sorption kinetics. The sorption proceeded through monolayer coverage of MWCNT-AA with capacities of 91.2 mg g−1 and 89.4 mg g−1 for Pu4+ and PuO22+, respectively following a Langmuir isotherm while the sorption kinetics followed a pseudo second order reaction with rate constants of 3.86 × 10−5 and 3.19 × 10−5 g mg−1 min−1 for Pu4+ and PuO22+ respectively. This MWCNT-AA showed high radiolytic stability and a method was developed for almost quantitative back extraction of plutonium in both the oxidation states from MWCNT-AA. Finally, the sorbent MWCNT-AA was employed for processing synthetic high level waste solution obtained from a research reactor origin. Moreover, density functional theory calculation was performed to examine the coordination and interaction behaviour of Pu4+ and PuO22+ ions towards MWCNT-AA. The present DFT study reveals that Pu is deca-coordinated (two from each of four nitrates and one AA) in the case of Pu4+ and octa-coordinated (two from each of two nitrates and one AA, and one from each of two oxo groups) in PuO22+. The calculated free energy of complexation was found to be almost three times higher for Pu4+ than PuO22+ both in the gas and aqueous phase, which thus confirms the experimentally observed higher sorption of Pu4+ compared to PuO22+ by MWCNT-AA.

The role of two sulfur sources, such as, thiophene and carbon disulfide, on the structure (graphitic layer) of carbon nanotube cotton (CNT-c) has been investigated during floating catalyst chemical vapour deposition (FC-CVD). The CNT-c assembly at 1200 °C with ferrocene and ethanol as catalyst and carbon precursors respectively was found to be predominantly consisting of (a) single-walled carbon nanotubes (SWCNTs) in the presence of carbon disulfide and (b) multi-walled carbon nanotubes (MWCNTs) in the presence of thiophene. The finding was based on detailed characterization using Raman spectroscopy, transmission electron microscopy and scanning electron microscopy. A possible mechanism for having two different structures has been discussed. The experimental results demonstrated that the interaction of sulfur source with the catalyst particle strongly influenced the number of graphitic layers of CNTs in the CNT-c assembly.

Graphene (Gr) is one of the most preferred reinforcement for polymer matrix, due to its large surface area. However, poor dispersion, due to stacking of Gr sheets, restricts their potential as reinforcement. In the present study, exfoliation of multi-layered graphene sheets is achieved in the presence of nanodiamond (ND), using ultrasonication. High-resolution electron micrographs clearly reveal the role played by ND in hindering restacking of graphene. SPM imaging further quantified exfoliation by measuring the thickness for different combinations of Gr:ND. Improved exfoliation of Gr increases both tensile strength and strain by ~71% and ~113%, respectively, for >0.5 wt% Gr content. Fracture toughness is improved by ~150% with Gr, and an additional 44% with ND decorated Gr. Numerical analysis further confirms the effect of ND assisted exfoliation of Gr in toughening behavior of the composite, which can be explained in terms of improved total interface area, helping in better load transfer.

Addition of carbon nanotubes (CNT) to Graphene (Gr) is seen to have synergistic effect as reinforcement to polymer matrix. This is possible as CNTs inhibit stacking of Gr sheets, thus providing larger surface area nanophase to get bonded with polymer matrix and providing mechanical support through load sharing and crack growth inhibition. However, tube like morphology and high aspect ratio of CNT often lead to entanglement, which restricts their effect in exfoliating Gr. The aim of the present study is to investigate the potential of ND in improving the synergistic effect of Gr-CNT hybrid as a reinforcement to epoxy matrix. This study utilizes the power of ultrasonication technique, which is very simple and scalable, for dispersing and incorporating nanofillers into epoxy matrix. Addition of ND to Gr-CNT epoxy composite improved the tensile strength from ~46% with 0.5 wt% (75Gr:25ND) to ~51% with 0.8 wt% (25Gr:25CNT:50ND) as compared to neat epoxy. While the fracture toughness improved from ~140% with 0.5 wt% (25Gr:75CNT) to 165% with 0.8 wt% (25Gr:50CNT:25ND). Fractured surfaces of composites revealed improved dispersion and strong interfacial interaction with addition of ND to Gr-CNT hybrid. NDs attaches to the surface of Gr inhibit the stacking of Gr sheets by restricting π-π stabilization. NDs also help in bridging the ends of CNTs together into long chains, thereby increasing the aspect ratio of the fiber like reinforcement. This increases the total available surface area of CNTs and Gr, to interact with epoxy matrix, improves the overall efficiency of Gr-CNT hybrid as a reinforcement, resulting into improvement in mechanical properties of the composite structure.

Multiwalled carbon nanotubes (MWCNTs) have been synthesized using methane in a floating catalyst chemical vapour deposition reactor at atmospheric pressure. The catalyst concentration, partial pressure of methane and synthesis temperature have been varied in order to understand their effects on the rate formation of MWCNTs, purity and size of MWCNTs. Reaction mechanism, rate controlling step and overall rate of reaction have been deduced using chemical reaction engineering approach. A systematic study was carried out in order to obtain the kinetic expression based on Langmuir-Hinshelwood type model. The kinetic model was based on the dissociative adsorption pathway of methane and subsequent removal of hydrogen from the adsorbed methyl group with two different active sites. The activation energy for the overall reaction was 46.1 kJ mol−1 in the temperature range of 1073–1273 K. The products have been characterized by transmission electron microscopy, thermogravimetry, BET and Raman spectroscopy. The BET surface area of purified MWCNTs were found to be 157 m2 g−1 with pore volume of 0.176 cc g−1.

Composites with boron carbide (B4C) as the matrix and short carbon fiber (Cf) as reinforcement in 2, 5 and 10 vol% were fabricated by hot pressing route. Microstructural analysis by scanning electron microscopy reveled that Cf got aligned perpendicular to the hot press direction. Agglomeration of Cf was observed at 10 vol% Cf. The addition of Cf improved the flexural strength of B4C-Cf composite and was superior to that of B4C-CNT composite. On other hand, the hardness and fracture toughness of B4C-Cf composite were inferior to that of B4C-CNT composite. The tribological studies revealed that B4C-CNT had superior wear resistance. Both B4C-Cf and B4C-CNT had lower coefficient of friction than monolithic B4C. The possible reasons for deviation of properties due to change in length scale of carbon reinforcement has been analyzed.

Carbon fiber epoxy composites are being used in numerous structural applications. However, fracture toughness of these composites is always less than expected. Therefore, potential of nanofillers in improving the fracture toughness of these composites, with, three different morphologies, i.e., Gr (sheet), CNT (tube) and nanodiamond (particle), in a well-connected 3D network is evaluated in this study. Both, interlaminar and intralaminar mode I fracture toughness, revealed improvement of ~260% and ~53%, respectively, with 25Gr:50CNT:25ND CF-epoxy, as compared to CF-epoxy composite. Marking a total improvement of ~1523% over pure epoxy on intralaminar fracture toughness. The composites were also assessed for tensile and interlaminar shear strength. An improvement of ~60% and ~16%, respectively, is noted with the addition of nanofillers. SEM analysis for delaminated and fractured surfaces revealed the toughening mechanism to be the high surface area of nanofillers, offering strong adhesion between matrix and fiber, along with improved matrix toughness.

Silicon carbide fabric converted from carbon fabric was prepared by a facile halide-activated pack cementation method. The XRD, SEM and EDS analyses confirm the formation of SiC fibres with graded conversion of carbon to SiC from surface to core of individual carbon fibres of carbon fabric. The graded conversion of carbon fibre to SiC was uniform and homogeneous throughout the fabric dimension. The thermokinetics of oxidation in atmospheric environment was studied by TGA analysis. The reaction kinetics and governing mechanism for oxidation of bare carbon fabric and silicon carbide fabric were calculated using Kissinger and Ozawa methods. It was observed that the activation energy for bare carbon fabric and silicon carbide fabric converted from carbon fabric are 62 and $$174 \hbox { kJ mol}^{-1}$$ , respectively. Further, it was observed that the silicon carbide fabric converted from carbon fabric follows the second-order surface reaction oxidation mechanism.

The oxidation kinetics of a 2-D carbon fabric were studied in both an air and a pure oxygen environment. A simple approach using non-isothermal thermogravimetry and differential thermogravimetry was used. The results showed that the non-isothermal oxidation process of the carbon fabric exhibited self-catalytic characteristics in both environments. The oxidation mechanism and kinetic parameters were analyzed with differential and integral models. Evidence indicated that the oxidation process was a surface-induced phenomenon. The oxidation mechanism in oxygen environment was controlled by random nucleation, whereas in the case of air environment it was phase boundary reaction controlled. Different oxidation mechanisms and their correlations with kinetic parameters have been discussed in detail.

Polyethersulfone-based beads encapsulating di-2-ethylhexyl phosphoric acid have been synthesized and evaluated for the recovery of rare earth values from the aqueous media. Percentage recovery and the sorption behavior of Dy(III) have been investigated under wide range of experimental parameters using these beads. Taguchi method utilizing L-18 orthogonal array has been adopted to identify the most influential process parameters responsible for higher degree of recovery with enhanced sorption of Dy(III) from chloride medium. Analysis of variance indicated that the feed concentration of Dy(III) is the most influential factor for equilibrium sorption capacity, whereas aqueous phase acidity influences the percentage recovery most. The presence of polyvinyl alcohol and multiwalled carbon nanotube modified the internal structure of the composite beads and resulted in uniform distribution of organic extractant inside polymeric matrix. The experiment performed under optimum process conditions as predicted by Taguchi method resulted in enhanced Dy(III) recovery and sorption capacity by polymeric beads with minimum standard deviation.

The present manuscript deals with the hydrogen absorption properties of multiwalled carbon nano-tubes (MWCNTs) doped with Pd nanoparticles by the conventional wet impregnation method and the polyol method. In the latter method Pd nanoparticles are doped into CNTs based on polyhydroxy organic compounds (polyol) mediated functionalization. The polyol medium reduces palladium chloride to palladium nanoparticles, and also acts as a capping agent to stabilize the Pd nanoparticles. The samples have been characterized using X-ray diffraction (XRD), Energy Dispersive X-ray (EDX) and Infrared (IR) spectroscopy. Hydrogen absorption studies clearly illustrate that Pd doped MW-CNT's prepared by polyol mediated functionalization show much higher hydrogen storage capacity compared to the sample prepared by wet impregnation route. To determine the cause of this behavior, Transmission Electron Microscopic (TEM) studies of the samples were carried out. The results indicate that the dispersion of Pd nanoparticle on the MW-CNT is much better for the sample prepared by the polyol route. An attempt was made to determine the existence of any metal-support interaction using Thermogravimetric Analysis (TGA). The investigation reveals that the higher dispersion of Pd nanoparticles on the CNT support plays a major role for the hydrogen adsorption.

An environment benign process for the separation of rare earths has been delineated for the first time by developing polyethersulfone based composite beads through phase inversion method, where the use of hazardous organic diluents could be circumvented. The porosity and pore structure of these beads were controlled through different additives, of which, polyvinyl alcohol and multiwall carbon nanotubes proved to be the most efficacious. The extraction efficiency of rare earths was ameliorated by four fold with the application of the developed nanotube incorporated beads. The influence of various process parameters, namely, aqueous phase acidity, metal ion concentration, presence of other competitive ions and temperature on the separation of representative yttrium ion has been elaborated in the present investigation. The experimental results attribute to the excellent stability and reusability of the developed beads. The feasibility of employing this novel technology in large scale has been established by successful operation in continuous column mode. The developed assay exhibits profound application towards a greener approach due to the elimination of hazardous organic diluents and prevention of significant organic extractant loss during the process of recovery of rare earths from aqueous media.

Extractant impregnated polyethersulfone beads have been prepared by phase inversion method and investigated for yttrium recovery from aqueous medium. The effect of experimental parameters on yttrium sorption has been studied. Quantitative sorption of yttrium (> 90%) was attained after 8 hours of equilibration time in the case of D2EHPA impregnated composite beads. Analysis of sorption data by different kinetic and diffusion models suggested that the sorption of Y(III) followed the pseudo-second order model. Stability tests with polymeric composite beads by multiple cycles of sorption and desorption of Y(III) have established the feasibility of reusing the beads for sorption of metal ions.

Oleyl amine stabilised Pd nanoparticles have been prepared by reverse micro-emulsion method and supported on multi walled CNTs. TEM studies have confirmed that Pd nanoparticles, having sizes in the range of 3–5 nm, are well dispersed on the CNTs. Based on 13C MAS NMR and TG-DTA studies it is inferred that the Pd nanoparticles interact with CNT support to form sp3 carbon species, which get effectively dispersed on the CNTs. Such finely dispersed Pd nanoparticles facilitate the spillover of hydrogen to the CNT support and improve the hydrogen storage capacity.

The oxidation kinetics of SiC nanowire coated carbon fibers in oxygen atmosphere were studied through isothermal thermo-gravimetric analysis and dynamic thermo-gravimetric analysis. The isothermal weight loss curve showed two activation energies for the oxidation of SiC nanowire coated carbon fibers. The oxidation process was reaction controlled below 923 K with an activation energy of 125 kJ mol− 1 and mixed controlled (gas diffusion and reaction) above 923 K with an activation energy of 28 kJ mol− 1. Under non-isothermal condition the oxidation mechanism followed three-dimensional diffusion obeying the Zhuravlev–Lesokhin–Tempel'man mechanism with differential form F(α) = 1.5(1 − a)4/3[(1 − a)− 1/3 − 1]− 1 and integral form G(α) = [(1 − a)− 1/3 − 1]2. The kinetic and thermodynamic parameters were evaluated and correlated with surface induced oxidation mechanism.

The manuscript presents the results on the sorption of U(VI), Am(III) & Eu(III) from pH medium by a novel amido-amine functionalized multiwalled carbon nanotube (MWCNT). The novel functional group was introduced in the MWCNT by two step processes and characterized by various instrumental techniques like Scanning Electron Microscopy (SEM), Raman and X-ray Photoelectron Spectroscopy (XPS). The sorption process was found to be highly dependent on the pH of the solution with maximum sorption for both 233U, 241Am & 152+154Eu at pH 7.0. Kinetics of sorption was found to be fast with equilibrium reached in ∼15min and the sorption was found to be following pseudo 2nd order kinetics for the radionuclides. The sorption for both 233U and 152+154Eu followed Langmuir sorption model with maximum sorption capacity of 20.66mg/g and 16.1mg/g respectively. This has been explained by DFT calculations which shows that more negative solvation energy of U(VI) compared to Am(III) and Eu(III) and stronger U-MWCNT-AA complex is responsible for higher sorption capacity of U(VI) compared to Am(III) and Eu(III).The synthesized amido-amine functionalized MWCNT is a very promising candidate for removal of actinides and lanthanides from waste water solution with high efficiency.

A novel and simple sol–gel route has been used for the fabrication of composite structure composed of carbon fibers and silicon carbide nanowires embedded in dense silicon carbide matrix. The carbonaceous silica sol was impregnated in the carbon fiber preform at atmospheric pressure. The sol impregnated carbon preform was cured and heat treated to convert into silicon carbide. The analysis by X-ray diffraction, scanning electron microscopy, X-ray tomography, and transmission electron microscopy indicates that the impregnated carbonaceous silica gel converts to β-silicon carbide with dense and wire morphology. Different morphological silicon carbide was uniformly distributed inside carbon fiber preform and there was no degradation in thermophysical properties of carbon composite during processing. These results reveal high efficient reinforcement of different morphological silicon carbide in carbon composite, demonstrate a new mechanism of carbon composite reinforcement and suggest a new direction to carbon composite reinforcement.

Carbon nanotubes have been synthesized from acetylene and methane in a fluidized bed by using ferrocene as the catalyst dispersed over carbon black support material. The agglomerate size of carbon black, loading of catalyst, total gas flow rate, partial pressure of reactant gas, temperature of synthesis, and time of synthesis have been varied to understand their effects on the yield of carbon nanotubes. A reaction mechanism consisting of eleven steps and the rate equations for these steps have been proposed. Formation of carbon molecules on the catalyst surface was found to be the rate controlling step in the temperature range of 700–807°C, with an activation energy 47 kJ mol−1, while diffusion through pores in the carbon black was found to be the rate controlling step in the temperature range of 807–1000°C with an activation energy of 7.6 kJ mol−1. A continuous deactivation of the catalyst, represented by an exponential decay, was observed. The products have been characterized by thermogravimetry, electron microscopy, and Raman spectroscopy. © 2014 American Institute of Chemical Engineers AIChE J, 60: 2882–2892, 2014

The separation of entrained di-nonyl phenyl phosphoric acid (DNPPA) from merchant grade phosphoric acid (MGA) by adsorption on the coconut shell based activated charcoal has been carried out. The effect of various process parameters, such as DNPPA concentration in aqueous phase of MGA, equilibrium time, amount of activated charcoal and temperature upon adsorption capacity of activated charcoal has been studied. The results showed that the adsorption equilibrium was reached after 240 minutes. The adsorption phenomenon followed pseudo-second order kinetics. Adsorption of DNPPA increased with initial concentration of DNPPA in the range of 50 to 200 mg/L. The experimental data fitted well with the Freundlich isotherm model. Decrease in adsorption with increase in temperature suggests that the adsorption process is exothermic in nature. The value of enthalpy change (ΔH = −35.52 kJ/mol) indicated that DNPPA adsorption on activated charcoal is a physisorption phenomenon. Column operation was carried out to obtai...

Decalcification studies on samarium–cobalt intermetallic alloy powder produced by reduction–diffusion process have been carried out under wide range of experimental conditions based on Taguchi method. This approach has been adopted to arrive at optimum conditions for the leaching operation for calcium removal without affecting the yield of Sm2Co17. The percentage effect of number of water wash, acid wash, pH and digestion time on decalcification was investigated. Conditions predicted by Taguchi method successfully brought down the residual calcium value to about 1750 ppm in Sm2Co17 suitable for further operation related to making permanent magnet. The Sm2Co17 phase was found to be stable even after long period of leaching operations as characterized by scanning electron microscopy and X-ray diffraction. Leaching of calcium from large batch product samples have been demonstrated successfully with 99.5% yield and residual calcium in the range of 1740–1750 ppm. Acetic acid and propionic acid showed comparable results in decalcification.

A novel amorphous carbon–carbon composite has been developed using carbon black dispersed in carbonized phenolic resin matrix in order to avoid Wigner energy problem associated with graphite. The as prepared sample showed a density of 1320 kg m −3 . This has been further densified by resin impregnation and chemical vapour infiltration. The effect of processing parameters on final density (1517 kg m −3 ) has been investigated. This composite possesses the compressive strength of 65 Mpa, coefficient of thermal expansion of 3 × 10 −6 K −1 and the specific heat of 1.2 J g −1 K −1 . This novel composite was subjected to 145 MeV Ne +6 heavy ion irradiation at different doses. The highest dose was kept at 3 × 10 −4 dpa. The stored energy in the composite was found to be 212 J g −1 at the highest dose of irradiation, which is much below than that of graphite. The composite remained amorphous after irradiation as confirmed by X-ray diffraction.

Selective synthesis of both metallic and semi-conducting single-walled carbon nanotubes (SWCNTs) has been performed using floating catalyst chemical vapour deposition (FC-CVD). It was observed that partial pressure of hydrogen determined the selectivity of SWCNTs being predominantly metallic at lower hydrogen concentration (20 vol%) and predominantly semiconducting at higher hydrogen concentration (80 vol%). The qualitative and quantitative analysis on type of SWCNTs was performed based on UV–vis-NIR, Raman spectra at different wavelengths and SWCNT-based field effect transistor device performance. Transmission electron microscopy was used to get diameter distribution of SWCNTs. Detailed analysis showed that the type of SWCNTs was decided at the nucleation stage that was governed by the collision frequency between hydrogen molecules and iron nanoparticles.

Carbon–carbon composites (C/Cs) are of significant technological importance in various advanced applications, owing to their unique mechanical and thermal properties. C/Cs are composed of carbon fiber-reinforced carbon matrix. This chapter summarizes various aspects of C/Cs in terms of matrix and reinforcement precursors, fabrication of C/Cs and effects of various processing parameters on their mechanical and thermal properties, and their applications. Effects of processing parameters and architecture of carbon fiber reinforcement have been highlighted.

Photo-stability of laser dyes has been an important consideration for dye lasers. In this work, photo-stability of dye and its effect has been investigated as a function of dye laser wavelengths rather than commonly studied photo-chemical degradation pathways upon excitation with pump laser. Here, we report a significant improvement in photo-stability of the liquid dye laser at peak emission wavelength compared to edge wavelengths of the dye gain curve, which was related with an increase in rate of stimulated emission of dye at peak wavelength. Thus, high laser efficiency harmonizes to high photo-stability of the dye at peak wavelength which is useful for the applications of dye lasers. As a representative case, the photo-stability rates of pyrromethene 567 (PM567) dye at different laser emission wavelengths were studied using a 10-Hz Nd-YAG (532 nm) laser-pumped dye laser set-up under lasing and non-lasing conditions. Deterioration of dye laser efficiency on account of photo-degradation of dye molecules was theoretically simulated using a time-dependent rate equation model, which has been found to be in good agreement with the experimental observations.