Onion-like Fullerenes Research Articles

Raman Spectra of Nano-structured Onion-like Fullerenes

Raman Spectra of Nano-structured Onion-like Fullerenes

オニオン構造フラーレンの多量生成および潤滑材への適用

Milligrams of onion-like fullerenes, so-called carbon onions, have been synthesized by heating diamond clusters in inert ambient at atmospheric pressure. Diamond clusters, of which average grain size is 5nm, were heated up to 1730°C and maintained at the temperature for 1minute in argon using an infrared image furnace. Transformation of diamond clusters into onion-like fullerenes was confirmed by high-resolution electron microscopy, which showed onion-like fullerenes have a well-controlled size ranging from 5 to 10 nm. Ball-on-disk type friction testing was conducted to characterize the tribological properties of onion-like fullerenes as a solid lubricant. As a result, onion-like fullerenes have exhibited lower friction, compared with graphite powders, in both air and vacuum. This low friction property of onion-like fullerenes has been displayed on a sliding disk with lower surface roughness and higher hardness.

Transformation of Active Carbon to Onion-like Fullerenes Under Electron Beam Irradiation

ABSTRACTThe transformation of an active carbon film with Pt nanoparticles to onion-like fullerenes has been in-situ investigated by a high-resolution transmission electron microscope. It was found that the onion-like fullerenes/metals polycrystalline film was formed under electron irradiation. The formation process was consisted of three steps: first, the flakes of onion-like fullerenes were induced by Pt nanoparticles; second, the flakes grew into a few ellipsoidal graphite shell; and third, a gradual reorganization of the formation of quasi-spheroid graphite shells and the bond of Pt particles was took place. It was a composite film of onion-like fullerenes and metal particles. It is suggested that the transformation mechanism involves an irradiation of electron and a catalytic effect of Pt nanoparticles, while any temperature rise due to electron irradiation seems to be negligibly small.

Electron energy loss study of plasmon excitations in curved carbon network

In the present contribution, we focus on the plasmon excitations of curved carbon sp 2 bonded materials: onion-like fullerenes and nanotubes. Experimental spatially resolved transmission Electron Energy Loss Spectroscopy (EELS) data are analysed within a dielectric approach where the anisotropy of particles is fully treated. Combination of theoretical simulation and experimental results allows the differentiation of tangential radial (12.8 eV) and tangential (16–19 eV) surface plasmon and of volume (23–27 eV) plasmons. A shift of the surface plasmon resonance energy with the electron impact parameter is attributed to a change of relative contributions of multipolar modes.

Formation of giant onion-like fullerenes under Al nanoparticles by electron irradiation

The conversion of an amorphous carbon film under Al nanoparticles to giant onion-like fullerenes (GOLFs), which was induced by electron irradiation in a transmission electron microscope, has been investigated. It has become clear that the nucleation and growth processes forming GOLFs from an amorphous carbon film consist of three steps: first, the flakes of GOLFs are induced under Al nanoparticles; second, the flakes grow into a few ellipsoidal graphitic shells; and third, a gradual reorganization occurs into structures comprising the quasi-spheroidal graphitic shells that are GOLFs. Fullerenes containing Al nanoparticles and Al atoms have been generated through these processes. It is suggested that the mechanism involves collisions with high-energy electrons and a catalytic effect of Al, while any temperature rise due to electron irradiation seems to be negligibly small.

Formation of a New Electric Material: Fullerene / Metal Polycrystalline Film

ABSTRACTAn investigation of the formation behavior and mechanism of onion like fullerene / metal polycrystalline film under electron beam irradiation is presented. Metallic nanoparticles of Al, Au and Pt having diameters of 1∼35 nm, were supported on an amorphous carbon film with thickness of about 20 nm. The amorphous carbon film transformed into onion-like fullerene film under electron beam irradiation, with intensity about 1020e/cm2·sec using high resolution transmission electron microscopy. The transformation mechanism and growth morphology have been investigated. It is found that the nucleation and growth process of onion-like fullerenes from amorphous carbon were divided into several steps: Firstly, a few elliptic shells of carbon were induced under Al, Au or Pt nanoparticles; secondly, a gradual reorganization took place into the structures composed of quasi-concentric spheroid or sphered graphite, i.e., onion like fullerenes, and finally, fullerenes were bonded to each other into a film.

Calculation of the energy loss for an electron passing near giant fullerenes

We present a theoretical analysis of the electron energy-loss spectra of isolated giant fullerenes. We use a macroscopic dielectric description of spherical onion-like fullerenes and a discrete dipole approximation (DDA) framework for tubular fullerenes. In the DDA model, an anisotropic dynamical polarizability is assigned to each carbon site. We stress the fundamental importance of the hollow character of giant fullerenes in the electron energy-loss resonances.