Programas de Investigación

URI permanente para esta comunidadhttps://repositorioinvestigare.pucmm.edu.do/handle/20.500.12060/2096

La PUCMM cuenta con seis (6) programas de investigación e innovación que responden a su misión de buscar soluciones científicas a los desafíos que enfrenta el pueblo dominicano y su entorno global.

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Mostrando 1 - 5 de 5

Carbon nanotubes coated with diamond nanocrystals and silicon carbide by Hot-filament chemical vapor deposition below 200 C substrate temperature
(ELSEVIER) Piazza, Fabrice; Morell, Gerardo; Beltran-Huarac, Juan C.; Paredes, Germercy; Ahmadi, Majid; Guinel, Maxime J.F.
Multi-walled carbon nanotubes (MWCNTs) dispersed onto a silicon substrate have been coated with diamond nanocrystals (DNC) and silicon carbide (SiC) from solid carbon and silicon sources exposed to H2 activated by hot filament chemical vapor deposition (HFCVD) at around 190 °C substrate temperature. MWCNT coating by DNC initiates during filament carburization process at 80 °C substrate temperature under conventional HFCVD conditions. The hybrid nanocarbon material was analyzed by scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, electron energy loss spectroscopy, selected area electron diffraction, X-ray diffraction and Raman spectroscopy. The structure of the MWCNTs is preserved during coating and the smooth DNC/SiC coating is highly conformal. The average grain size is below 10 nm. The growth mechanism of DNC and SiC onto MWCNT surface is discussed.
Low temperature, pressureless sp2 to sp3 transformation of ultrathin, crystalline carbon films
(ELSEVIER) Piazza, Fabrice; Gough, Kathleen; Monthioux, Marc; Puech, Pascal; Gerber, Iann; Wiens, Richard; Paredes, Germercy; Ozoria, Cristhofer
Nanosized and crystalline sp3-bonded carbon materials were prepared over large surface areas up to ~33x51 m2 from the exposure of few-layer graphene (FLG) to H radicals produced by the hot-filament process at low temperature (below 325 C) and pressure (50 Torr). Hybrid materials were also obtained from the partial conversion of FLG. sp3-C related peaks from diamond and/or lonsdaleite and/or hybrids of both were detected in UV and visible Raman spectra. C-H bonding was directly detected by Fourier Transform Infrared (FTIR) microscopy over an area of ~150 m2 and one single component attributed to sp3-C-H mode was detected in the C-H stretching band showing that carbon is bonded to one single hydrogen and strongly suggesting that the sp3-C materials obtained are ultrathin films with basal planes hydrogenated. The experimental results are compared to computational predictions and comprehensively discussed. Those materials constitute new synthetic carbon nanoforms after fullerenes, nanodiamonds, carbon nanotubes and graphene. This opens the door to new research in multiple areas for the development of new potential applications and may have wide scientific impact, including for the understanding of extraterrestrial diamond-related structures and polytype formation mechanism(s).
Synthesis of diamond nanocrystals on polyimide film
(ELSEVIER) Piazza, Fabrice; Solá, Francisco; Resto, Oscar; Fonseca, Luis F.; Morell, Gerardo
Sulfur-assisted hot-filament chemical vapor deposition (HFCVD) was recently employed to grow diamond nano-crystals on polyimide film [F. Piazza, G. Morell, Diamond and Related Materials, 16 (2007) 1950], unambiguously showing that the substrate temperature was below 360 °C, the polyimide glass transition temperature. This accomplishment has opened the door to employ diamond in a wide range of applications where it needs to be integrated with temperature sensitive materials. The result reported earlier relies on visible Raman spectroscopy analysis. We hereby report new additional evidences confirming the result from transmission electron microscopy (TEM), high-resolution TEM, energy dispersive X-ray analysis, electron energy loss spectroscopy and selected area electron diffraction.
Towards a better understanding of the structure of diamanoïds and diamanoïd/graphene hybrids
(ELSEVIER) Piazza, Fabrice; Monthioux, Marc; Puech, Pascal; Gerber, Iann C.
Hot-filament process was recently employed to convert, totally or partially, few-layer graphene (FLG) with Bernal stacking into crystalline sp3–C layers at low pressure. The result reported earlier relies on Raman spectroscopy and Fourier transform infrared microscopy. As soon as the number of graphene layers in the starting FLG is higher than 2-3, the sp2–C to sp3–C conversion is partial only, due to the prevalent Bernal stacking sequence. We report new evidences confirming the sp2–C to sp3–C conversion from electron diffraction at low energy, Raman spectroscopy and Density Functional Theory (DFT) calculations. Partial sp2–C to sp3–C conversion generates couples of twisted, superimposed coherent domains (TCD), supposedly because of stress relaxation, which are evidenced by electron diffraction and Raman spectroscopy. TCDs come with the occurrence of a twisted bilayer graphene feature located at the interface between the upper diamanoïd domain and the non-converted graphenic domain underneath, as evidenced by a specific Raman signature consistent with the literature. DFT calculations show that Raman T peak originates from a combination of the sp3–C stretching mode of a sp3–C layer with the optical out-of-plane mode of a graphene layer; both layers being sandwiched between a highly hydrogenated sp3–C surface and the underneath unconverted graphene layer(s).
Wettability of hydrogenated tetrahedral amorphous carbon
(ELSEVIER) Piazza, Fabrice; Morell, Gerardo
The wettability and surface energy of hydrogenated amorphous carbon films (a-C:H) elaborated by distributed electron cyclotron resonance plasma were studied by contact angle measurements in relation to composition, structure and topography. Tetrahedral a-C:H (ta-C:H) showed relatively high water contact angle (CA) up to 82.3°, and low surface energy (Es), down to 25.3 mJ/m2. Hydrophobicity was found to increase with the intensity of the ion bombardment and with the tetrahedral character. A decrease of the dispersive component is responsible of the decrease of surface energy with substrate bias. Low mass-density polymer-like a-C:H (PLC) presents also a relatively high hydrophobicity with high water CA, up to 76.7°, and low surface energy values, down to 32.1 mJ/m2. Hydrophobicity is interpreted as resulting from a surface layer rich in sp2-carbon for ta-C:H and rich in C–H bonds for PLC.

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Examinando Programas de Investigación por Autor "Piazza, Fabrice"