The lattice specific heat in carbon nanotubes is evaluated within the microscopic model proposed by Mahan and Jeon, published
in the Physical Review B, in 2004. Phonons are considered for single wall carbon nanotubes in armchair configuration. As expected,
low temperature and high temperature regions show different behaviour of specific heat. Carbon nanotubes are also displaying
a very interesting lattice transport depending on the tube diameter, with high thermal conductivities for small diameters.
Authors:Robert Vajtai, Sujit K. Biswas, Binqing Wei, Gouwen Meng, Yung Joon Jung and Pulickel M. Ajayan
Single and multiwalled carbon nanotubes have attracted significant interest due to their one-dimensional structure and unique electrical and mechanical properties. Among the wide variety of their potential applications most importantly they offer potential to serve as building blocks for future electronic device architectures [1, 2, 3, 4, 5, 6]. Carbon nanotubes may serve as active or passive electronic elements; and as passive elements they may serve as interconnects both on short and long ranges [7, 8]. The most essential prerequisite for realizing CNT architectures is to be able to grow nanotubes at controlled sites, in predetermined orientations and to form interconnections. Significant progresses in growing aligned carbon nanotube films have been made recently with a combined approach of the floating catalyst method using pre-patterned templates and chemical vapor deposition (CVD) [9, 10, 11, 12]. Recently we summarized our work on growing architectures of carbon nanotubes, which might be integrated into microelectronic circuits . While the predefined growth of the above mentioned large nanotube structures is important and receives a lot of attention characterization of the product also deserves similarly high attention being a key for future applications and giving the real importance and purpose of the growth efforts. In this paper, we report some of our works, which are directed towards electrical tests on CNTs, namely high current carrying capacity; vertically organized multiwalled nanotubes showing the possible usage of highly ordered and well-shaped tubes; and characterization of singlewalled nanotube junctions.
Authors:E. Zsolt Horváth, A. Antal Koós, Krisztián Kertész, Zofia Vértesy, György Molnár, Mária Ádám, Csaba Dücső, József Gyulai and P. László Biró
Gas sensing properties of different carbon nanotube (mostly multiwall,
MWCNT) mats, based on electrical resistance measurement were investigated in a
simple arrangement and found that the sensitivity for different gases or vapors
highly depends on the pre-treatment and functionalization of nanotubes. The
selectivity of the sensing was demonstrated by building a vapor recognition
system based on an array of multitube sensors made of differently
Authors:J. B.Nagy, J. N. Coleman, A. Fonseca, A. Destrée, Z. Mekhalif, N. Moreau, L. Vast and J. Delhalle
Organic polymers -
carbon nanotubes nanocomposites are synthesized either by mechanical mixing of
the two components or by covalently linking the nanotubes to the matrix. The
various procedures will be overviewed and the determining factors will be
identified for the best mechanical properties of the composites. On the other
hand, it will be shown that for highest electrical conductivity much smaller
amounts of carbon nanotubes are needed if the nanotubes can be aligned. The
thermal conductivity of the nanocomposites will also be overviewed. Finally,
together with nanoclay particles, nanotubes are inducing remarkable flame
retardant properties in the nanocomposites materials.
Authors:A. Andreescu, Adriana Savin, Rozina Steigmann, Nicoleta Iftimie, E. Mamut and R. Grimberg
This paper presents a model for evaluation of effective thermal conductivity for the composites with carbon nanotubes (CNT)
having log-normal function of distribution of CNT, with direct effect over depolarization factor. The CNT are considered having
cylindrical shape with L/d ratio very high. The model parameters are calculated in function of the data from literature. The influence of volume fraction
of reinforced materials, of the aspect ratio of the particles included and of the ratio of the two thermal conductivities
Authors:K. Katok, V. Tertykh, S. Brichka and G. Prikhod’ko
Pyrolytic decomposition of acetylene over the surface of nickel-, cobalt-
and iron-containing ordered mesoporous MCM-41 silicas has been studied. Catalytically
active matrices have been prepared by chemisorption of volatile metal acetylacetonate
complexes on the silica surface. Reduction of the supported metal-containing
compounds was carried out in hydrogen or acetylene atmosphere. Acetylene is
used not only as a source of carbon in synthesis of the nanostructures but
also as a reagent capable of reducing metal ions in the surface chemical compounds.
Formation of carbon nanotubes and nanofibers is shown to depend on the pyrolysis
Authors:D. Carta, S. Bullita, A. Falqui, M. Casula, A. Corrias and Z. Kónya
A series of Fe/Co based nanocomposites where the matrix is mesoporous ordered cubic Im3m silica (SBA-16 type) characterized by a three dimensional cage-like structure of pores were obtained by two different approaches: impregnation and gelation. X-ray diffraction and transmission electron microscopy analysis show that after metal loading, calcination at 500 °C and reduction in H2 fl ux at 800 °C the nanocomposites retain the well-ordered structure of the matrix with cubic symmetry of pores. All nanocomposites prepared were tested for the production of carbon nanotubes by catalytic chemical vapour deposition. Transmission electron microscopy points out that good quality multi-walled carbon nanotubes are obtained.
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.