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We investigate the intercalation process of oxygen in-between a PVD-grown graphene layer and different copper substrates as a methodology for reducing the substrate-layer interaction. This growth method leads to an extended defect-free graphene layer that strongly couples with the substrate. We have found, by means of X-ray photoelectron spectroscopy, that after oxygen exposure at different temperatures, ranging from 280 °C to 550 °C, oxygen intercalates at the interface of graphene grown on Cu foil at an optimal temperature of 500 °C. The low energy electron diffraction technique confirms the adsorption of an atomic oxygen adlayer on top of the Cu surface and below graphene after oxygen exposure at elevated temperature, but no oxidation of the substrate is induced. The emergence of the 2D Raman peak, quenched by the large interaction with the substrate, reveals that the intercalation process induces a structural undoing. As suggested by atomic force microscopy, the oxygen intercalation does not change significantly the surface morphology. Moreover, theoretical simulations provide further insights into the electronic and structural undoing process. This protocol opens the door to an efficient methodology to weaken the graphene-substrate interaction for a more efficient transfer to arbitrary surfaces.

While high-quality defect-free epitaxial graphene can be efficiently grown on metal substrates, strong interaction with the supporting metal quenches its outstanding properties. Thus, protocols to transfer graphene to insulating substrates are obligatory, and these often severely impair graphene properties by the introduction of structural or chemical defects. Here we describe a simple and easily scalable general methodology to structurally and electronically decouple epitaxial graphene from Pt(111) and Ir(111) metal surfaces. A multi-technique characterization combined with ab-initio calculations was employed to fully explain the different steps involved in the process. It was shown that, after a controlled electrochemical oxidation process, a single-atom thick metal-hydroxide layer intercalates below graphene, decoupling it from the metal substrate. This decoupling process occurs without disrupting the morphology and electronic properties of graphene. The results suggest that suitably optimized electrochemical treatments may provide effective alternatives to current transfer protocols for graphene and other 2D materials on diverse metal surfaces.

While high-quality defect-free epitaxial graphene can be efficiently grown on metal substrates, strong interaction with the supporting metal quenches its outstanding properties. Thus, protocols to transfer graphene to insulating substrates are mandatory, and these often severely impair graphene properties by the introduction of structural or chemical defects. Here we describe a simple, fast and easily scalable general methodology to structurally and electronically decouple epitaxial graphene from metal surfaces. A multi-technique characterization of the different steps involved in the process, combined with ab-initio calculations, shows that after a controlled electrochemical oxidation process a single atom thick metal-hydroxide layer intercalates below graphene decoupling it from the metal substrate. The decoupling process takes place without disrupting the morphology and electronic properties of graphene. The electrochemical protocol has been proved to work on Gr/Pt(111) and Gr/Ir(111) substrates. Epitaxial graphene was grown in UHV conditions by thermal decomposition of fullerenes [1] and the samples were characterized in-situ by STM and LEED. Subsequent ex-situ characterization with AFM, XPS and Raman before and after the electrochemical treatment demonstrates the efficiency of the decoupling process. This work suggests that suitably optimized electrochemical treatments may provide viable alternatives to transfer protocols for graphene and other 2D materials on diverse metal surfaces.

The catalytic role of the metallic substrates has been the perfect starting point to grow high quality graphene layers by thermal decomposition of aromatics [1]. However, metallic substrates quench the graphene’s outstanding properties that make graphene the most promising material for future applications. Thus, protocols to transfer graphene to different technologically relevant substrates are mandatory. These transfer processes are cost inefficient and some can severely degrade the properties of graphene by introducing structural and chemical defects. As an alternative, we propose a novel approach that is less invasive and easily scalable. We target pristine graphene sheets grown on metals and employ electrochemical oxidation at controlled potentials to introduce a single atom-thick oxide decoupling layer. A multi-technique structural characterization (STM, AFM and Raman) combined with theoretical studies (ab-initio calculations) of the different steps of the process has been carried out to fully understand this decoupling. Epitaxial graphene has been grown on Pt(111) in UHV by thermal decomposition of aromatics. Fig. 1a shows a representative STM image of a typical Moiré as well as the typical LEED pattern obtained for Gr on Pt(111) [2]. After in-situ characterization the sample was removed from UHV and characterized by AFM, SEM and Raman spectroscopy before and after electrochemical treatments. Fig. 1b shows important changes in the Raman spectra of the graphene layer induced by the electrochemical treatment. The AFM overall topography shows that about 90% of the surface is decoupled, and ab-initio calculations clearly show that intercalation of a single atom-thick oxide layer can induce a structural separation of the graphene with respect to the surface. These results suggest that carefully controlled electrochemical oxidation can provide an alternative and cleaner method to the transfer of graphene.

Development of epoxy or epoxy-based vinyl ester composites with improved mechanical and electromagnetic properties, filled with carbon-based nanomaterials, is of crucial interest for use in aerospace applications as radar absorbing materials at radio frequency. Numerous studies have highlighted the fact that the effective functional properties of this class of polymer composites are strongly dependent on the production process, which affects the dispersion of the nanofiller in the polymer matrix and the formation of micro-sized aggregations, degrading the final properties of the composite. The assessment of the presence of nanofiller aggregation in a composite through microscopy investigations is quite inefficient in the case of large scale applications, and in general provides local information about the aggregation state of the nanofiller rather than an effective representation of the degradation of the functional properties of the composite due to the presence of the aggregates. In this paper, we investigate the mechanical, electrical, and electromagnetic properties of thermosetting polymer composites filled with graphene nanoplatelets (GNPs). Moreover, we propose a novel approach based on measurements of the dielectric permittivity of the composite in the 8–12 GHz range in order to assess the presence of nanofiller aggregates and to estimate their average size and dimensions.

Crazes constitute one of the most common failure mechanisms in polymers. They act as fracture precursors, severely degrading the mechanical properties of the material. Thus, a deep understanding of the chain rearrangement occurring inside crazes is of utmost fundamental and practical importance. We have employed synchrotron infrared microspectroscopy (SIRMS) and Raman microspectroscopy to investigate the conformational changes inside micron-sized crazes in poly(ethylene terephthalate), PET. A promotion of the full-extended chain conformational structure at the expense of mainly the trans amorphous mesomorphic phase along with an increase in crystallinity of around 4% has been found. These results differ from what we observed across the deformation neck during PET cold drawing, where no promotion of the all-trans crystalline conformation occurred for slow drawing speeds at temperatures well below the glass transition. Our results show the tremendous capabilities of advanced vibrational microspectroscopy techniques to investigate microscale phenomena in polymer science.

High-quality epitaxial graphene can be efficiently grown on metal substrates. Unfortunately, the strong interaction with the supporting metal quenches graphene¿s outstanding properties, thus transfer protocols to insulating surfaces are nowadays routinely used. These transfer processes are cost inefficient and some can severely degrade the properties of graphene by introducing structural and chemical defects. In this work we have used cyclic voltammetry to decouple epitaxial graphene from Pt(111) and polycrystalline Cu metal surfaces. A multitechnique structural characterization (STM, AFM and Raman) combined with theoretical studies (ab-initio calculations) of the different steps of the process show that an atom thick metal-oxide layer is intercalated on the interface between the Ultra High Vacuum (UHV) grown graphene and the surface. Epitaxial graphene has been grown in UHV by thermal decomposition of aromatics, following the procedure described in [1]. Fig. 1a shows a representative STM image of a wide scan area as well as the typical LEED pattern obtained for Gr on Pt(111) [2, 3]. It is possible to clearly distinguish a wrinkle, some nanobubbles and the contour of the Gr domains. Fig. 1b shows a high resolution STM image acquired on a terrace, where the representative z(¿44x¿44)R15°Gr Moiré superstructure is observed with atomic resolution. The Moiré superstructure is a fingerprint for single-layer graphene on the platinum surface [2]. Thus, the STM together with the LEED confirm the high quality of the graphene layer used for the experiments. After in-situ characterization the sample was removed from UHV and characterized by AFM, SEM and Raman spectroscopy before and after electrochemical treatments. Fig. 2 shows important changes in the Raman spectra of the graphene layer induced by the electrochemical treatment. In the untreated sample only atmospheric O2 and N2 bands can be observed, and no evidence of the characteristic graphene bands (G and 2D) are found, c

A mechanical characterization study of the whole range (ZrO2)1-x-(Y2O3)x system is presented for thin film samples. Films have been prepared by Electron Beam Physical Vapour Deposition (EB-PVD) on Si(1 0 0) substrates. The mechanical characterization, obtained from nanoindentation and Brillouin Light scattering (BLS) techniques, shows a monotonous behaviour between the two pure compounds of the series except for the film with 0.08 Y2O3 molar content of yttria-stabilized zirconia (YSZ) solid solution that presents an anomalous hard value. Additionally, BLS is presented as an alternative technique to the study of the mechanical properties of this system. © 2007.