AEROBIC OXIDATION OF A DIESEL PARAFFINIC-NAPHTHENIC FRACTION IN THE PRESENCE OF Co ASSISTED Fe-CONTAINING MULTI-WALLED CARBON NANOTUBES

The impact of suspended particles on the bioavailability of pollutants has long been a controversial topic. In this study, adsorption of pentachlorophenol (PCP) onto a natural suspended particulate matter (SPM) and multi-walled carbon nanotubes (MWCNTs) was studied. Facilitated transports of PCP into carp by SPM and MWCNTs were evaluated by bioaccumulation tests exposing carp (Carassius auratus red var.) to PCP-contaminated water in the presence of SPM and MWCNTs, respectively. Desorption of PCP on SPM and MWCNTs in simulated digested fluids was also investigated. The results demonstrate that MWCNTs (K F = 7.99 × 10(4)) had a significantly stronger adsorption capacity for PCP than the SPM (K F = 19.0). The presence of SPM and MWCNTs both improved PCP accumulation in the carp during the 21 days of exposure, and the 21 days PCP concentration in the carp was enhanced by 25.9 and 12.8 % than that without particles, respectively. The enhancement in bioaccumulation by MWCNTs was less than that by the SPM. Considerably more PCP was accumulated in the viscera of the fish (BCF = 519495 for SPM and 148955 for MWCNTs), and the difference in PCP concentrations between different tissues became greater with particles. PCP desorption in the simulated digestive fluids was faster than that in the background solution. Compared to MWCNTs-bound PCP, more SPM-bound PCP was desorbed, and K F of desorption for SPM was at least 4 orders of magnitude higher than that for MWCNTs, which can explain the greater enhancement in bioaccumulation in the presence of SPM. Particle-bound pollutants might pose more risk than pollutants alone.

In this work, we investigated the effect of multi-walled carbon nanotubes (MWCNTs) and bio-graphene (bG) on the structure and activity of glucose oxidase (GOx), as well as on the performance of the respective electrochemical glucose biosensors. Various spectroscopic techniques were applied to evaluate conformational changes in GOx molecules induced by the presence of MWCNTs and bG. The results showed that MWCNTs induced changes in the flavin adenine dinucleotide (FAD) prosthetic group of GOx, and the tryptophan residues were exposed to a more hydrophobic environment. Moreover, MWCNTs caused protein unfolding and conversion of α-helix to β-sheet structure, whereas bG did not affect the secondary and tertiary structure of GOx. The effect of the structural changes was mirrored by a decrease in the activity of GOx (7%) in the presence of MWCNTs, whereas the enzyme preserved its activity in the presence of bG. The beneficial properties of bG over MWCNTs on GOx activity were further supported by electrochemical data at two glucose biosensors based on GOx entrapped in chitosan gel in the presence of bG or MWCNTs. bG-based biosensors exhibited a 1.33-fold increased sensitivity and improved reproducibility for determining glucose over the sweat-relevant concentration range of glucose.

Carbon nanotubes catalysis in liquid-phase aerobic oxidation of hydrocarbons: Influence of nanotube impurities

Process for producing carbon/carbon composites

Electrical properties of solution cast films of polystyrene/polyaniline-multiwalled carbon nanotube nanocomposites

Morphological investigation was carried out with melt‐mixed ternary polymer blends of polyamide6 (PA6), polypropylene (PP) and acrylonitrile butadiene styrene copolymer (ABS) in the presence of compatibilizer and multiwall carbon nanotubes (MWNTs). 80/10/10 (wt/wt/wt) PA6/PP/ABS and 80/10/10 (wt/wt/wt) PP/PA6/ABS blends exhibited “core‐shell” morphology, whereas 80/10/10 (wt/wt/wt) ABS/PP/PA6 blends exhibited “separately dispersed” phase morphology. The type of phase morphology was unaltered in the presence of either compatibilizer or MWNTs in the respective ternary polymer blends. The morphological refinement in the presence of compatibilizer was explained on the basis of melt‐interfacial reaction. In contrast, the refinement in the dispersed droplets in the presence of MWNTs was due to the localization of MWNTs in the specific phase. Dynamic relaxation spectroscopic analysis indicated an increase in the relaxation time of PA6 chain in the presence of compatibilizer in the corresponding ternary blends. The variation in the relaxation time was dependent on the efficiency of the compatibilizer. The variation in the relaxation time for PA6 in the presence of 1 wt% MWNTs in the respective ternary blends also followed a similar trend; however, the extent of mobility of PA6 phase was influenced by the state of dispersion of MWNTs in the corresponding blends. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Macro-channeled porous hydroxyapatite (HA) scaffolds were fabricated by a polymer foam replication method. Composites were prepared by coating the surface of HA scaffolds with polycaprolactone (PCL) in the presence of graphene nanopowders (in the form of flakes) and multi-walled carbon nanotubes (MWCNTs) at different concentrations. Compression strength of the scaffolds was investigated as a function of additive concentration. Results revealed that the use of PCL coating increased the mechanical strength of HA scaffolds. Besides, addition of graphene or MWCNTs further improved the compression strength of the constructs when they were used at 0.25 wt% and a decrease was observed at higher graphene and MWCNT concentrations. Highest mechanical performance was obtained in composite HA scaffolds involving MWCNTs. In vitro acellular bioactivity experiments revealed that both graphene and MWCNT-incorporated HA scaffolds showed higher bioactivity in simulated body fluid compared to bare scaffolds. However, HA formation ability was more pronounced with MWCNTs compared to graphene nanoflakes where they were possibly acted as an effective nucleation sites to induce the formation of a biomimetic apatite. Additionally, scaffolds prepared in the study were found to be nontoxic to the mouse bone marrow mesenchymal stem cells.

Crystallization-induced phase separation and segmental relaxations in poly(vinylidene fluoride)/poly(methyl methacrylate) (PVDF/PMMA) blends was systematically investigated by melt-rheology and broadband dielectric spectroscopy in the presence of multiwall carbon nanotubes (MWNTs). Different functionalized MWNTs (amine, -NH2; acid, -COOH) were incorporated in the blends by melt-mixing above the melting temperature of PVDF, where the blends are miscible, and the crystallization induced phase separation was probed in situ by shear rheology. Interestingly, only -NH2 functionalized MWNTs (a-MWNTs) aided in the formation of β-phase (trans-trans) crystals in PVDF, whereas both the neat blends and the blends with -COOH functionalized MWNTs (c-MWNTs) showed only α-phase (trans-gauche-trans-gauche') crystals as inferred from wide-angle X-ray diffraction (WXRD) and Fourier transform infrared (FTIR). Furthermore, blends with only a-MWNTs facilitated in heterogeneous nucleation in the blends manifesting in an increase in the calorimetric crystallization temperature and hence, augmented the rheologically determined crystallization induced phase separation temperature. The dielectric relaxations associated with the crystalline phase of PVDF (αc) was completely absent in the blends with a-MWNTs in contrast to neat blends and the blends with c-MWNTs in the dielectric loss spectra. The relaxations in the blends investigated here appeared to follow Havriliak-Negami (HN) empirical equations, and, more interestingly, the dynamic heterogeneity in the system could be mapped by an extra relaxation at higher frequency at the crystallization-induced phase separation temperature. The mean relaxation time (τHN) was evaluated and observed to be delayed in the presence of MWNTs in the blends, more prominently in the case of blends with a-MWNTs. The latter also showed a significant increase in the dielectric relaxation strength (Δε). Electron microscopy and selective etching was used to confirm the localization of MWNTs in the amorphous phases of the interspherulitic regions as observed from scanning electron microscopy (SEM). The evolved crystalline morphology, during crystallization-induced phase separation, was observed to have a strong influence on the charge transport processes in the blends. These observations were further supported by the specific interactions (like dipole induced dipole interaction) between a-MWNTs and PVDF, as inferred from FTIR, and the differences in the crystalline morphology as observed from WXRD and polarized optical microscopy (POM).

The emerging technology of sodium ion batteries has attracted a great deal of attention due to the abundant availability and cost efficiency of the concerned raw materials. The technology still needs improvements, primarily in terms of finding suitable anode material with superior Na-capacity, cyclic stability and also rate capability. This is mainly caused by graphitic carbon not being able to intercalate sodium, unlike in the case of lithium. Layered Na2Ti3O7, because of its low potential against Na/Na+and decent theoretical Na-capacity (~200 mAh/g), has emerged as a promising anode material among other Na-based intercalation compounds [1]. However, in addition to its poor rate capability owing to inherently low electronic conductivity in pristine form, its cyclic stability is also far from being satisfactory. Poor structural stability during sodiation/desodiation is one of the reasons for the same. Against this backdrop, the present work focuses on improving the overall electrochemical behaviour, not only by reducing size of the Na2Ti3O7 particles to nano-sized regime, but also by incorporating conducting reinforcements like multi-walled carbon nanotubes (MWCNTs). However, the challenges associated with synthesizing active materials having nanoscaled dimensions via facile and cost-effective wet-chemical synthesis routes, while at the same time achieving intimate contact with carbon nanotubes usually pose practical hindrances towards improving rate capability and cyclic stability of promising ceramic electrode materials. Developing MWCNTs-incorporated composite electrode slurry via the usual physical mixing route may not allow intimate contact; rather may lead to contamination. Growth of MWCNTs on electrode-active particles via vapour deposition is not a cost-effective and scalable process. These disadvantages have been overcome in our work by developing an innovative, but facile sol-gel based route, which helped in synthesizing Na2Ti3O7 nanoparticles with near-perfect control over stoichiometry and also in intimate contact with MWCNTs. In more precise terms, the sol-gel based route has been tuned for successfully developing Na2Ti3O7 nanoparticles with MWCNTs uniformly wrapped around them allowing intimate contact with the MWCNTs, as was clearly evident from the high-resolution TEM images. The results once again highlight the success of this route based on direct addition of MWCNTs into the ‘matrix’ sol, followed by rapid gelation and subsequent crystallization in presence of MWCNTs (for Na-ion battery electrode), as recently demonstrated also for LiFePO4-MWCNT electrodes (for Li-ion batteries) [2]. The specific Na-capacities, as recorded during galvanostatic cycling, were considerably higher upon incorporation of the MWCNTs, as compared to those with the active particles of the same size/composition, prepared using the same route, but sans MWCNTs. More importantly, the cyclic stability improved significantly in the presence of the MWCNTs. The differences were more notable at the higher current densities, signifying considerably improved rate capability. In more specific terms, for over a period of 100 discharge/charge cycles, the capacity retention for Na2Ti3O7/MWCNT was superior to that for Na2Ti3O7, sans MWCNTs, by a factor of ~16. Another important observation has been the significant reduction in voltage hysteresis in presence of the MWCNTs. In addition to increasing the overall electrical conductivity, the anchoring/buffering action provided by the MWCNTs against the high volume changes during phase transformation reactions, might possibly be some of the reasons for the higher capacity and improved cyclic stability in the case of MWCNTs-containing Na2Ti3O7 nanoparticles. The work, to be presented, also includes in-situ synchrotron X-Ray diffraction studies for obtaining better insights into some of the fundamental aspects concerning phase transformations during charge/discharge at such ultra-fine dimension, in the presence/absence of MWCNTs (in intimate contact) and also in the presence of impurity phases (as deliberately introduced). The results provide clarity on the sodiation/de-sodiation mechanisms and correlations between the electrochemical performances, phase assemblage and phase evolutions of Na2Ti3O7 and Na2Ti3O7/MWCNT anodes for Na-ion batteries. Keywords: Na2Ti3O7/MWCNT, Na-ion batteries, Cyclic stability, In-situ synchrotron X-Ray diffraction

X-ray diffraction evidence of a phase transformation in zirconia by the presence of graphite and carbon nanotubes in zirconia toughened alumina composites

This study investigates the bond strength of aluminum sheets subjected to the roll bonding process in the presence of multiwall carbon nanotubes (MWCNTs). The effects of MWCNTs dispersion, thickness reduction, weight fraction of MWCNTs at the interface, and rolling temperature on the bond strength of the commercial pure aluminum sheets are studied. The peeling test is used to evaluate the bond strength of aluminum sheets. Optical microscopy and scanning electron microscopy are also used to evaluate the surface conditions of the peeled surfaces. Results indicate that, compared to the spread method, using the solution dispersion method to disperse MWCNTs reduces aluminum sheet’s bond strength. Also, the presence of MWCNTs reduces the sheet’s bond strength compared to aluminum sheets at a constant thickness reduction. However, bond strength is increased with higher thickness reductions in the presence or absence of MWCNTs. It is also shown that increasing the entry temperature improves bond strength, but that bond strength enhancement is lower in aluminum-MWCNTs sheets than in aluminum-aluminum sheets.

The preparation of thermoplastic nanocomposites of waterborne polyurethane (WBPU) and multiwall carbon nanotubes (MWCNTs) via anin situpolymerization approach is presented. The effects of the presence and content of MWCNTs on the morphology and thermal, mechanical and electrical properties of the nanocomposites were investigated. Carbon nanotubes were modified with amide groups in order to enhance their chemical affinity towards WBPU. Thermogravimetric studies show enhanced thermal stability of the nanocomposites. Scanning and transmission electronic microscopy images prove that functionalized carbon nanotubes can be effectively dispersed in WBPU matrix. Mechanical properties reveal that Young's modulus and tensile strength tend to increase when appropriate amounts of MWCNTs are loaded due to the reinforcing effect of the functionalized carbon nanotubes. Thermal properties show an increase in the glass transition temperature and storage modulus with an increase in MWCNT content. X‐ray diffraction reveals better crystallization of the WBPU in the presence of MWCNTs. The WBPU/MWCNT nanocomposite film containing 1 wt% of MWCNTs exhibits a conductivity nearly five orders of magnitude higher than that of WBPU film. © 2017 Society of Chemical Industry

Simultaneous effect of nanoparticles and surfactant on emulsion liquid membrane: Swelling, breakage and mean drop size

Multiwall carbon nanotubes (MWNT) were melt-mixed with poly(ethylene-co-methacrylic acid) ionomers (Surlyn) using twin screw microcompounder. The specific interactions existing between the Na+ moieties in Surlyn and the π electron clouds of MWNT were supported by FTIR and Raman spectroscopic analysis. SAXS scattering patterns were found to be progressively broadened in presence of MWNT in Surlyn/MWNT composites. Morphological investigations revealed selective clustering of MWNT in the vicinity of the ionic domains in Surlyn. Further, the domain size of the ionic clusters was found to increase with increasing MWNT content disrupting the ionic pairs apart in the ionic domain. The melt rheological response of Surlyn was significantly affected in presence of MWNT and was profoundly dependent on the ionic clusters. The state of dispersion of MWNT was assessed by AC electrical conductivity measurements. The associated percolation threshold was observed between 1.5–2 wt% of MWNT.

The effect of multi-walled carbon nanotubes (MWCNTs) on cure kinetic parameters of the epoxy/amine/TiO2 (1 wt%) resin system was studied dynamically at four heating rates using DTA. The presence of MWCNT in various amounts (0.1, 0.2, 0.4 and 0.6 wt%) neither retarded nor accelerated the cure reaction of the epoxy/amine/TiO2 system in a considerable extent. Addition of MWCNTs increased the extent of cure of the corresponding nanocomposites, especially at higher contents up to 0.4 wt% MWCNT filled composite. However, increasing the MWCNT content to 0.6 wt% adversely affected the extent of cure due to nanoparticle agglomeration. The fracture surface morphology of the nanocomposites revealed that the cracks deviated on reaching the MWCNTs, while propagating in the polymer matrix. Fractional extent of conversion (α) was calculated using genetic algorithm. Flynn–Wall–Ozawa and Kissinger methods were used to analyze the kinetic parameters. The presence of MWCNTs did not affect the autocatalytic cure mechanism of epoxy/amine/TiO2 resin system and also did not cause any considerable barrier effect on the curing process. Activation energy data fitted well in the cubic polynomial regression equations and the changes of Ea with respect to α proved the autocatalytic cure mechanism, being followed by all the MWCNT-containing epoxy-based hybrid nanocomposites.