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Nanopages
Authors:
I. Sayago
,
M. Fernández
,
J. Fontecha
,
M. Horrillo
,
A. Seral-Ascaso
,
R. Garriga
, and
E. Muñoz

Carbon nanotube (CNT) networks offer fascinating opportunities as active layers for gas sensor devices. We here review our work on the use of CNT fi lms prepared by airbrush spraying as sensitive layers in resistive sensor devices for gas detection. The sensor fi lms were fabricated by airbrushing nanotube dispersions on alumina substrates. Networks of different CNT materials were tested as active sensing element sensors for the detection of pollutant gases (H2, NO2, octane, toluene, NH3). Our results indicate that the CNT structure and chemical functionalization affect both the CNT entanglement within the airbrushed networks and their gas sensing performance. Thus, highly sensitive NO2 and H2 resistive sensors were fabricated out of networks of carboxylic acid functionalized double-walled carbon nanotubes and Pd-functionalized single-walled carbon nanotubes, respectively. Issues related to gas sensing mechanisms of the tested resistive sensors, and device performance dependence upon the sensor operation temperature are also discussed here. All tested resistive sensors provided negligible responses to interfering gases such as NH3, toluene and octane. CNT-based gas sensors made by other fi lm preparation techniques are also reviewed, and their gas sensor performance is compared to those reported here.

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Abstract  

Carbon nanotubes (CNTs) were synthesized using a chemical vapour deposition (CVD) method. The properties of CNTs before and after vacuum annealing treatment were studied using scanning electron microscopy (SEM), scanning tunneling microscopy/spectroscopy (STM/STS) and thermogravimetric analysis (TG). Field emission characteristics of the raw and vacuum heated (up to 650C) carbon nanotube films (CNTFs) were measured in a diode system. Emissive properties of the CNTFs depend on an annealing process during which structural changes in the nanotube walls take place. The structural changes, related to saturation of dangling bonds, influence a rate of oxidation process and also improve the emissive field properties.

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Journal of Thermal Analysis and Calorimetry
Authors:
Eudes Lorençon
,
Rodrigo G. Lacerda
,
Luiz O. Ladeira
,
Rodrigo R. Resende
,
André S. Ferlauto
,
Ulf Schuchardt
, and
Rochel M. Lago

Introduction Carbon nanotubes (CNTs) have been intensely investigated due to their unique chemical, mechanical, and electrical behavior. The inherent properties of CNTs make them versatile supports for metallic nanoparticles

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Multiwall carbon nanotubes were synthesized either on the outer surface of iron containing mesoporous silicates using catalytic chemical vapor deposition (CCVD) or in the pore system of morphologically different mesoporous materials (hexagonal or spherical shapes) with graphitization of the template molecules. Transmission electron microscopy (TEM) study shows that the CCVD method resulted in long, bent and well graphitized carbon nanotubes on impregnated samples irrespective to the morphology of the silicate. Isomorphously substituted spherical MCM-41 with low Si/Fe ratio was found to be active catalysts for carbon nanotube production in CCVD as well. Synthesis of MWNTs with graphitization of template molecules in the pores of MCM-41 was successful in hexagonal MCM-41 samples irrespective that they contain or not iron in the silicate framework. Carbon nanotube formation was not observed in spherical derivatives of these samples during the graphitization process.

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, the multi-wall carbon nanotube (MWNT) and the single-wall carbon nanotube (SWNT). A SWNT is a graphene sheet rolled into a cylinder with typical diameter on the order of 1.4 nm. However, a MWNT consists of several concentric cylinders with diameters

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have already been discovered, although they are constantly being improved, and require massive amounts of basic nanomaterials such as multiwalled carbon nanotubes (MWNCTs), which means carbon nanotube (CNTs) 1 production capacity must be increased

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Journal of Thermal Analysis and Calorimetry
Authors:
F. Xu
,
L. Sun
,
J. Zhang
,
Y. Qi
,
L. Yang
,
H. Ru
,
C. Wang
,
X. Meng
,
X. Lan
,
Q. Jiao
, and
F. Huang

Abstract  

Heat capacities of the carbon nanotubes (CNTs) with different sizes have been measured by modulated temperature differential scanning calorimetry (MDSC) and reported for the first time. The results indicated the values of C p increased with shortening length of CNTs when the diameters of CNTs were between 60 and 100 nm. However, the values of C p of CNTs were not affected by their diameter when the lengths of CNTs were 1–2 um, or not affected by the length of CNTs when their diameters were below 10 nm. The thermal stabilities of the CNTs have been studied by TG-DTG-DSC. The results of TG-DTG showed that thermal stabilities of CNTs were enhanced with their diameters increase. With lengths increase, the thermal stabilities of CNTs increased when their diameters were between 60 and 100 nm, but there is a slight decrease when their diameters were less than 60 nm. The further DSC analyses showed both released heat and T onset increased with the increase of CNTs diameters, which confirms the consistency of the results from both TG-DTG and DSC on CNTs thermal stability.

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fracture toughness, is trying to be solved by adding carbon nanotubes (CNT). This is expected to improve the mechanical and thermal behaviour of the epoxy resins, increasing also their electrical conductivity [ 1 – 3 ]. However, in the last years, it was

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single-walled carbon nanotubes (SWCNTs) characterization since their discovery in 1993 by Iijima [ 8 ]. It has been widely used to study the stability of SWCNT in an inert (e.g., Ar, N 2 ) or oxidizing atmosphere (e.g., O 2 , CO 2 ) at different

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Introduction In this invited contribution to the NATAS (North American Thermal Analysis Society) conference proceedings, I am briefly summarizing the projects of my group on single-wall carbon nanotubes (CNTs), conducted at

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