161 research outputs found
Use of facile mechanochemical method to functionalize carbon nanofibers with nanostructured polyaniline and their electrochemical capacitance
A facile approach to functionalize carbon nanofibers [CNFs] with nanostructured polyaniline was developed via in situ mechanochemical polymerization of polyaniline in the presence of chemically treated CNFs. The nanostructured polyaniline grafting on the CNF was mainly in a form of branched nanofibers as well as rough nanolayers. The good dispersibility and processability of the hybrid nanocomposite could be attributed to its overall nanostructure which enhanced its accessibility to the electrolyte. The mechanochemical oxidation polymerization was believed to be related to the strong Lewis acid characteristic of FeCl3 and the Lewis base characteristic of aniline. The growth mechanism of the hierarchical structured nanofibers was also discussed. After functionalization with the nanostructured polyaniline, the hybrid polyaniline/CNF composite showed an enhanced specific capacitance, which might be related to its hierarchical nanostructure and the interaction between the aromatic polyaniline molecules and the CNFs
Vapor grown carbon nanofiber based cotton fabrics with negative thermoelectric power
Vapor grown carbon nanofiber (CNF)
based ink dispersions were used to dip-coat woven
cotton fabrics with different constructional parameters, and their thermoelectric (TE) properties studied
at room temperature. Unlike the positive thermoelectric power (TEP) observed in TE textile fabrics
produced with similar carbon-based nanostructures,
the CNF-based cotton fabrics showed negative TEP,
caused by the compensated semimetal character of the
CNFs and the highly graphitic nature of their outer
layers, which hinders the p-type doping with oxygen
groups onto them. A dependence of the electrical
conductivity (r) and TEP as a function of the woven
cotton fabric was also observed. The cotton fabric with
the largest linear density (tex) showed the best
performance with negative TEP values around
- 8 lV K-1
, a power factor of 1.65 9 10-3
lW m-1 K-2
, and a figure of merit of 1.14 9 10-6
.
Moreover, the possibility of a slight e- charge transfer
or n-doping from the cellulose onto the most external
CNF graphitic shells was also analysed by computer
modelling. This study presents n-type carbon-based
TE textile fabrics produced easily and without any
functionalization processes to prevent the inherent
doping with oxygen, which causes the typical p-type
character found in most carbon-based TE materialsFEDER funds through
COMPETE and by national funds through FCT – Foundation for
Science and Technology within the project POCI-01-0145-
FEDER-007136. E. M. F. Vieira is grateful for financial support
through FCT with CMEMS-UMinho Strategic Project UIDB/
04436/202
Effect of Covalent Functionalisation on Thermal Transport Across Graphene-Polymer Interfaces
This paper is concerned with the interfacial thermal resistance for polymer
composites reinforced by various covalently functionalised graphene. By using
molecular dynamics simulations, the obtained results show that the covalent
functionalisation in graphene plays a significant role in reducing the
graphene-paraffin interfacial thermal resistance. This reduction is dependent
on the coverage and type of functional groups. Among the various functional
groups, butyl is found to be the most effective in reducing the interfacial
thermal resistance, followed by methyl, phenyl and formyl. The other functional
groups under consideration such as carboxyl, hydroxyl and amines are found to
produce negligible reduction in the interfacial thermal resistance. For
multilayer graphene with a layer number up to four, the interfacial thermal
resistance is insensitive to the layer number. The effects of the different
functional groups and the layer number on the interfacial thermal resistance
are also elaborated using the vibrational density of states of the graphene and
the paraffin matrix. The present findings provide useful guidelines in the
application of functionalised graphene for practical thermal management.Comment: 8 figure
The phase of iron catalyst nanoparticles during carbon nanotube growth
We study the Fe-catalyzed chemical vapor deposition of carbon nanotubes by complementary in situ grazing-incidence X-ray diffraction, in situ X-ray reflectivity, and environmental transmission electron microscopy. We find that typical oxide supported Fe catalyst films form widely varying mixtures of bcc and fcc phased Fe nanoparticles upon reduction, which we ascribe to variations in minor commonly present carbon contamination levels. Depending on the as-formed phase composition, different growth modes occur upon hydrocarbon exposure: For γ-rich Fe nanoparticle distributions, metallic Fe is the active catalyst phase, implying that carbide formation is not a prerequisite for nanotube growth. For α-rich catalyst mixtures, Fe3C formation more readily occurs and constitutes part of the nanotube growth process. We propose that this behavior can be rationalized in terms of kinetically accessible pathways, which we discuss in the context of the bulk iron–carbon phase diagram with the inclusion of phase equilibrium lines for metastable Fe3C. Our results indicate that kinetic effects dominate the complex catalyst phase evolution during realistic CNT growth recipes.S.H. acknowledges funding from ERC grant InsituNANO (No.
279342). We acknowledge the European Synchrotron
Radiation Facility (ESRF) for provision of synchrotron
radiation facilities. We acknowledge the use of facilities within
the LeRoy Eyring Center for Solid State Science at Arizona
State University. C.T.W. and C.S.E. acknowledge funding from
the EC project Technotubes. A.D.G. acknowledges funding
from the Marshall Aid Commemoration Commission and the
National Science Foundation. R.S.W. acknowledges funding
from EPSRC (Doctoral training award) and B.C.B. acknowledges
a Research Fellowship at Hughes Hall, Cambridge.This is the accepted manuscript. The final version is available from ACS at http://pubs.acs.org/doi/abs/10.1021/cm301402g
Development of ClearPEM-Sonic, a multimodal mammography system for PET and Ultrasound
International audience; ClearPEM-Sonic is an innovative imaging device specifically developed for breast cancer. The possibility to work in PEM-Ultrasound multimodality allows to obtain metabolic and morphological information increasing the specificity of the exam. The ClearPEM detector is developed to maximize the sensitivity and the spatial resolution as compared to Whole-Body PET scanners. It is coupled with a 3D ultrasound system, the SuperSonic Imagine Aixplorer that improves the specificity of the exam by providing a tissue elasticity map. This work describes the ClearPEM-Sonic project focusing on the technological developments it has required, the technical merits (and limits) and the first multimodal images acquired on a dedicated phantom. It finally presents selected clinical case studies that confirm the value of PEM information
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