Marc Monthioux

Filling single-wall carbon nanotubes

Single-wall nanotube (SWNT)-based hybrid materials represent a quite recent research field. On the basis of previous works performed on multi-wall carbon nanotubes (MWNTs), the goal is to fill the inner SWNT cavity with various compounds, whose the combination with the surrounding carbon tube is expected to allow peculiar physical phenomena to occur and/or peculiar properties to be obtained. As compared to MWNTs, regular SWNT inner cavity is really nanometric, i.e., in the dimension range where quantum phenomena could occur. However, a major drawback is that filling ∼1-nm wide tubes is less easy (i.e., compared to MWNTs), and the related driving forces not fully understood. Who is working in the field, what and how are the SWNT-based hybrid nano-materials prepared so far, what could possibly be the filling mechanisms, are questions that are discussed in this paper. A review of the existing literature is made, with a focus on C60@SWNTs (peapods), which appear to be the most amazing—and the most promising—SWNT-based hybrid nano-materials to date.

Sensitivity of single-wall carbon nanotubes to chemical processing: an electron microscopy investigation

Abstract Single wall carbon nanotube (SWNT) materials subjected to various chemical treatments including regular, published, acidic purification treatments, were investigated by high resolution transmission electron microscopy and X-ray diffraction. Results show that acid purification cannot avoid SWNT structure alteration. The liquid, acidic medium provokes the gathering of pre-existing fullerenes into crystallised fullerite. A slight temperature increase has a dramatic effect on SWNT degradation which can result in complete amorphisation. Immersion of some of the SWNT materials in dimethylformamide (DMF) was also found to be harmful to the SWNT structure. Several observations suggest that as-prepared (not treated) SWNTs contain structural defects along the tube walls which act as preferred sites for the acid (or DMF) attack, inducing side wall openings.

Carbon nanotube superconducting quantum interference device

A superconducting quantum interference device (SQUID) with single-walled carbon nanotube (CNT) Josephson junctions is presented. Quantum confinement in each junction induces a discrete quantum dot (QD) energy level structure, which can be controlled with two lateral electrostatic gates. In addition, a backgate electrode can vary the transparency of the QD barriers, thus permitting change in the hybridization of the QD states with the superconducting contacts. The gates are also used to directly tune the quantum phase interference of the Cooper pairs circulating in the SQUID ring. Optimal modulation of the switching current with magnetic flux is achieved when both QD junctions are in the ‘on’ or ‘off’ state. In particular, the SQUID design establishes that these CNT Josephson junctions can be used as gate-controlled π-junctions; that is, the sign of the current–phase relation across the CNT junctions can be tuned with a gate voltage. The CNT-SQUIDs are sensitive local magnetometers, which are very promising for the study of magnetization reversal of an individual magnetic particle or molecule placed on one of the two CNT Josephson junctions.

Comparison between natural and artificial maturation series of humic coals from the Mahakam delta, Indonesia

Abstract Type III (humic) organic matter from the Mahakam delta (Indonesia) was chosen to compare artificial and natural coal series. Powdered and concentrated immature organic matter was heated in sealed gold tubes for 24 hr at temperatures ranging from 250 to 550°C and under pressures ranging from 0.5 to 4 kb, with and without water. Both elemental and Rock-Eval analyses were used to characterize the products. A comparison between our results, published data and the natural model shows that, quantitatively, natural maturation is simulated better when pyrolysis is performed under confined conditions (no free volume, no diluting inert gas). Thus, pyrolysis in a medium swept by an inert gas, vacuum pyrolysis and some pyrolysis in sealed glass tubes must be considered to be poor simulation tools. The presence of water does not seem to have an essential effect. Allowing the hydrocarbons formed to reach a certain value of partial pressure seems to be important. Results are unchanged when external pressure varies from 0.5 to 4 kb.

Carbon nanotube encapsulated fullerenes: a unique class of hybrid materials

Abstract We report the discovery of elongated fullerene capsules contained within single-wall carbon nanotubes, as well as new findings pertaining to encapsulated, self-assembled chains of C 60 . The observed structures comprise a new, complete class of hybrid materials: hemispherically-capped graphene cylinders of various lengths within carbon nanotubes. Short capsules and chains comprised of only a few C 60 molecules spontaneously jump nanometer distances along the axis of the containing tube. A model explaining this behavior is proposed.

Thermal behavior of (organosilicon) polymer-derived ceramics. V: Main facts and trends

Abstract Extensive investigations of polymer-based ceramic materials taken within the Si-C-N-O-(H) system have been performed and previously published as Parts I – IV. This paper reports the main results, facts, trends and conclusions which can be drawn from them, regarding the physical and chemical behavior of these materials submitted to an increasing thermal treatment. Both similarities and discrepancies are described and explained, whatever the chemical composition of the ceramic, (i.e. containing Si-C or Si-C-N, Si-C-O, Si-C-N-O). Emphasis is made on the mechanisms, and the role of various parameters, either intrinsic (e.g. the role of compositional C, O, or N) or extrinsic (e.g. influence of the atmosphere), is examined. The overall results indicate, among others, that excess carbon (relative to the SiC stoichiometry) is always beneficial both to the structural stability of the ceramic and the mechanical properties (when measurable), while heteroatoms (O, N) are always finally detrimental. They thus sustain the current efforts to develop ceramic fibers from chemical systems as simple as possible, using oxygen-free curing processes. More generally, they provide guidelines for understanding, and somewhat predicting, the thermochemical behavior of any related materials.

Understanding Nicalon® fibre

Abstract From structural and nanotextural studies by transmission electron microscopy, Nicalon fibre was found to be a microcomposite. Its composition by weight is 55% β-SiC crystals (1·6 nm average diameter), 40% SiO1·15C0·85 intergranular phase and 5% free carbon. The free carbon is composed of isolated aromatic entities less than 1 nm in diameter, with 2–3 aromatic layers stacked in turbostratic order. Taking into account the peculiar texture and applying the rule of mixtures, the density and porosity of the as-received fibre have been calculated, and found to be in agreement with measured values. From the nanotextural and chemical events occurring during a series of increasing heat-treatments (argon flow), a chemical balance accounting for the gaseous species released and fibre weight loss is proposed. Qualitative and quantitative changes in elastic modulus and electrical resistivity have been modelled.

Introduction to Carbon Nanotubes

Carbon nanotubes are remarkable objects that look set to revolutionize the technological landscape in the near future. Tomorrowʼs society will be shaped by nanotube applications, just as silicon-based technologies dominate society today. Space elevators tethered by the strongest of cables; hydrogen-powered vehicles; artificial muscles: these are just a few of the technological marvels that may be made possible by the emerging science of carbon nanotubes.

Pyrolysis of organic matter in cold-seal pressure autoclaves. Experimental approach and applications

Abstract Comparison of natural series of type III coals and type II kerogens with experimental results have shown that the cold-seal autoclave system offers the possibility to simulate the maturation of organic matter. The experimental vessel as well as the temperature regulation and monitoring systems are described in some detail. Limitations of the technique for mass balance calculations and simulations on whole rocks are discussed and indicate necessary improvements of this system for organic geochemistry purposes.

Heavy petroleum products: Microtexture and ability to graphitize

Abstract Various asphalts extracted from crude oils by light n-alcanes were studied by elemental analysis, conventional transmission microscopy and X-ray diffraction. Like most carbonaceous materials, asphalts contain planar aromatic structures (4–12 rings in dia.) single or piled up by twos or threes (basic structural units). These units are distributed at random in the bulk and linked by non-aromatic groups. Heat-treatment was carried out under inert gas flow from room temperature to 3000°C. In the early stages of carbonization, the structural units acquire a local parallel orientation (just before the end of the tar release). The extent of the molecular orientation depends only on the opposing influence of the hydrogens and of heteroatoms such as oxygen, sulfur and nitrogen. The extent of orientation increases drastically from less than 50 A to a few μm as the percentage of cross-linking agents (oxygen and sulfur) and of nitrogen decreases. At the same time the ability to graphitize increases progressively. All kinds of intermediates between non-graphitizing and graphitizing carbons are found after heat-treatment.