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Carbon-Based Nanofluids Characteristics
Published in Alina Adriana Minea, Advances in New Heat Transfer Fluids, 2017
Gabriela Huminic, Angel Huminic, Florian Dumitrache, Claudiu Fleacă
The laser pyrolysis method requires the presence of a sensitizer (laser energy transfer agent) besides nanoparticle precursors. For the Fe(C) nanoparticle laser-assisted synthesis, ethylene plays the role of a sensitizer because it has a good absorption at the main emission line of CO2 laser (wavelength 10.59 μm). At the same time, ethylene plays the role of carbon donor but with quite low efficiency. Different compositions were used to calibrate the carbon donor source: pure ethylene or ethylene mixed with different other gases or vapors such as inert species (Ar or He), reducing agents (H2 or NH3), organic monomers (acrylic acid or methyl methacrylate), organosilanes (hexamethyldisiloxane), or even acetylene. The last case induces a strong increase of carbon content in the resulting Fe–C nanoparticles. Usually, the employed iron source is Fe(CO)5 (iron pentacarbonyl). It is a volatile liquid whose vapors are entrained to the reaction zone using a carrier gas (Dumitrache et al. 2004, 2011). Also, nonvolatile Fe(C5H5)2 (ferrocene) was used by spraying (nebulizing) their toluene solution (Leconte et al. 2007). In the last case, carbon is mainly provided by toluene and ferrocene cyclopentadienyl ligands.
Early days in the Rick Smalley lab
Published in Harry Kroto, 60: Buckminsterfullerene, 2016
We eventually tried an experiment with formaldehyde, and were able to detect its mass spectrum in the molecular beam. However, when we tried to activate the fragmentation detection, using a dye laser tuned near 280 nm, we were unable to detect any photofragments. We decided that the problem was the weak n ^ p* transition for formaldehyde (it is a forbidden electronic transition, becoming weakly allowed by vibronic coupling), the low vapor pressure that we were able to achieve by heating the solid paraformaldehyde, and its low quantum yield for photodissociation. To improve matters, I decided to try a molecule with a much stronger transition, much greater vapor pressure, and unit quantum yield. I settled on iron pentacarbonyl, Fe(CO)5. This decision turned out to be our first lucky accident.
Structures, electronic properties and reaction paths from Fe(CO)5 molecule to small Fe clusters
Published in Phase Transitions, 2018
The reaction paths and the corresponding stable configurations of Fem(CO)n (1 ≤ m ≤ 3, 0 ≤ n ≤ 12) clusters are labeled in Figure 1 (blue, gray and red spheres represent Fe, C and O atoms). The symmetry and binding energy Eb are listed in Table 1. During the stages of iron pentacarbonyl decomposition, Fe(CO)5 seems to be gradually separated carbon monoxide and the corresponding energies are expended. Once Fe(CO)4 is generated, the combined reaction Fe(CO)5 + Fe(CO)4 → Fe2(CO)9 is bound to first occurs, Correspondingly the reaction energy ΔE 0.059 eV is released. Nevertheless, for the decomposition steps from Fe(CO)4 to Fe(CO)3, the calculated energy 0.187 eV should be depleted.