Carbon-based materials exhibit unique properties driven by the many different bonding configurations available to the
element carbon. Many of them proved to be compatible with inorganic and/or biologic systems and might be considered
as useful materials in medicine and biology. The carbon nanoparticles existing in environment are an important factor on
healthy, either by their toxicity or by interaction with pathogen microorganisms, Carbon black is nowadays one of the
additive most widely used to make composites and the applicability of nanocarbon-based composites depends on how
well its properties can be manipulated. The activation of carbon materials improves their functional properties and
depends on their structure. Through the variation of the experimental parameters, the method of laser-induced pyrolysis
allows obtaining carbon nanoparticles with different morphologies providing useful functional properties. The focus is to
drive these materials into a regime where they can naturally interface with the surrounding matter. With other words, the
goal of the work is to investigate how to modulate, through laser induced pyrolysis, the characteristics of carbon
nanopowders in order to achieve functional properties claimed by specific applications.
Laser pyrolysis of a hydrocarbon-based mixture is a continuous method for the synthesis of soot-containing fullerene. In this synthesis process, the mechanism of fullerene formation and soot is the radical mechanism of the PAH formation. In the flames producing both fullerenes and soot, exactly forming carbon cages require particular types of reaction sequences. The fullerene concentrations are strongly correlated with those of PAHs in the flame. The equilibrium soot-PAHs-fullerene is dependent on experimental parameters. FTIR spectra of soot extracts and exhaust gases are discussed in the frame of this dependence.
TiO2 nano powder was prepared by laser pyrolysis of gas phase reactants. TiCl4 (vapor) was used as titanium precursor. The crystalline structures and morphologies of the powder have been analyzed by transmission electron microscopy (TEM), selected area electron diffraction (SAD) and Raman spectrometry. The different characterization techniques suggest that a nano-crystalline mixture of anatase and rutile is obtained.
Soots obtained by laser pyrolysis of different gaseous/vapor hydrocarbons were investigated. The morphology variation of carbon soot versus process parameters and nature of reactants was analyzed and discussed. The role of oxygen is essential in obtaining soot particles having considerable curved-layer content.
The paper presents the experimental results on adsorption properties of carbon nanopowders which have been obtained by laser pyrolysis of hydrocarbon-based mixtures. We have investigated the adsorption of benzene, n-hexane and ciclohexane. The influence of the nanocarbon morphology (which depends on gaseous precursors and synthesis conditions) on adsorption characteristics is reported.
The embedding of Fe-based nanoparticles in carbon layers allows novel physical and catalyzing properties due to inertness and resistance to external detrimental conditions. We have prepared almost spherical carbon encapsulated iron nanoparticles with narrow size distribution, via laser co-pyrolysis method in which the CW CO2 laser beam irradiates a gas mixture containing iron pentacarbonyl (vapors) and ethylene/acetylene hydrocarbons. Specific flow geometries were used in order to synthesize iron particle first followed by stimulate hydrocarbon decomposition at iron surfaces. High-resolution transmission electron microscopy images reveal the core-shell feature of synthesized nanostructures with around 2 nm thick carbon layers and 3-7 nm diameters iron-based core dimensions. The mean diameter could be experimentally controlled. It was found a decreasing trend of particle size with the decreasing of pressure and total reactant gas flow. EELS, EDAX and Raman spectroscopy analysis confirm the simultaneous presence of carbon and iron. The nanoparticles were seeded onto Si wafer and further used as substrates for laser induced CVD carbon nanotubes growth. Depending on laser power density, nanotubes or nanofibres are formed, in strong dependence with the location of iron based nanoparticles on Si substrates as revealed by SEM analysis.
We report the obtaining of thin organic films based on poly(methyl methacrylate) polymer by Pulsed Laser Deposition on silicon substrates and quartz slides. The films were characterized by complementary techniques: x-ray Diffraction, x-ray Photoelectron Spectroscopy, Atomic Force Microscopy, Optical Microscopy, Raman Spectroscopy and Fourier Transform Infrared Spectroscopy. The obtained structures are amorphous. The film composition and structure depend on both the laser fluence as well as on the temperature of the substrate during deposition. We put in evidence in freshly deposited films the presence of diamond-like carbon while its amount strongly increases by annealing at ~400°C in Argon atmosphere.
Iron-carbon composite nanopowders have been synthesized by the CO2 laser pyrolysis of gas-phase reactants. The experimental device allows for a very low reaction time and a rapid freezing that creates nanoscale-condensed particles. Iron pentacarbonyl and ethylene-acetylene mixtures were used as iron and carbon precursors. In a two-steps experiment, the reaction products may present themselves as iron-based nanoparticles dispersed in a carbon matrix. By a careful control of experimental parameters and radiation geometries we demonstrate the feasibility of an efficient and well-controlled, single-step technique for the production of iron-based nano-cores embedded in carbon layers. Highly dispersed nanoparticles, narrow size distributions and particles with about 4.5 - 6 nm mean diameters were obtained. Electron microscopy and Raman spectroscopy were used in order to analyze the structure and composition of the obtained nanopowders as well as their Soxhlet residue.
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