http://www.bibsonomy.org/burst/user/statphys23/afmBibSonomy BuRST Feed for /user/statphys23/afm2008-07-21T01:38:28+02:00http://www.bibsonomy.org/bibtex/2afc55db786fd5c66bc57071f1a30a7ad/statphys23statphys232007-06-20T10:16:09+02:00wetting statphys23 nanoscale fracture glass afm topic-6 <span style="color:#555555;">M. <a href="http://www.bibsonomy.org/author/Ciccotti">Ciccotti</a> and M. <a href="http://www.bibsonomy.org/author/George">George</a> and A. <a href="http://www.bibsonomy.org/author/Grimaldi">Grimaldi</a> and G. <a href="http://www.bibsonomy.org/author/Pallares">Pallares</a> and E. <a href="http://www.bibsonomy.org/author/Charlaix">Charlaix</a> and C. <a href="http://www.bibsonomy.org/author/Marličre">Marli&#269;re</a> </span><em>Abstract Book of the XXIII IUPAP International Conference on Statistical Physics, </em><em>Genova, Italy, </em><em>9-13 July2007. </em>Wed Jun 20 10:16:09 CEST 2007Genova, ItalyAbstract Book of the XXIII IUPAP International Conference on Statistical Physics9-13 JulyWetting phenomena at the nanoscale inside sharp cracks in silica glasses2007wetting statphys23 nanoscale fracture glass afm topic-6 Since crack propagation in oxide materials at low crack velocities is partly determined by chemical corrosion, proper knowledge of the crack tip chemistry is crucial for understanding fracture in these materials. Such knowledge can be obtained only from in situ studies because the processes that occur in the highly confined environment of the crack tip are very different from those that take place at free surfaces, or that can be traced post mortem. We report the occurrence of hydrous liquid condensate between the two fracture surfaces in the vicinity of the tip of tensile cracks in silica. Observations are performed in real-time by means of atomic force microscopy (AFM) at continuously controlled crack velocities in the regime of stress corrosion [1]. The liquid character of the condensation is confirmed by the study of AFM phase-contrast data. Condensate formation and changes in extent and shape are demonstrated for a wide range of macroscopic humidity at different crack speeds [2]. These observations are then compared with the predictions obtained by combining the theoretical models for capillary condensation and for the formation of thin wetting films on the fracture surfaces. It is believed that this evidence of a nanoscale liquid hydrous phase at the crack tip will enable novel insights in the chemistry of failure of oxide materials as well as in the physics of wetting at the nanoscale.\\ 1) Wondraczek L., Ciccotti M. et al., 2006. J. Am. Cer. Soc. 89[2], pp. 746-749.\\ 2) Ciccotti M., George M., et al., 2007. J. Non-Crist. Solids. Under review.http://www.bibsonomy.org/bibtex/272a57f310f0597a63a4d94d2b5f098c5/statphys23statphys232007-06-20T10:16:09+02:00laser reflectivity g-xrd statphys23 x-ray topic-4 carbon pulsed nano-structures deposition field emission afm <span style="color:#555555;">E. <a href="http://www.bibsonomy.org/author/Cappelli">Cappelli</a> and C. <a href="http://www.bibsonomy.org/author/Scilletta">Scilletta</a> and M. <a href="http://www.bibsonomy.org/author/Servidori">Servidori</a> and S. <a href="http://www.bibsonomy.org/author/Orlando">Orlando</a> </span><em>Abstract Book of the XXIII IUPAP International Conference on Statistical Physics, </em><em>Genova, Italy, </em><em>9-13 July2007. </em>Wed Jun 20 10:16:09 CEST 2007Genova, ItalyAbstract Book of the XXIII IUPAP International Conference on Statistical Physics9-13 JulyStructure, morphology and density evolution of carbon films grown by UV, Visible and N-IR pulsed laser ablation of graphite2007laser reflectivity g-xrd statphys23 x-ray topic-4 carbon pulsed nano-structures deposition field emission afm The structure of materials deposited by chemical or physical vapour deposition (CVD, PVD) is strongly dependent on experimental conditions like temperature, pressure and kind or quantity of energy delivered. Depending on these parameters we obtained carbon material structures evolving from amorphous to fullerene-like nano-structures or oriented graphene nano-particles. We report the experimental conditions explored to attain hoped and foreseen results for promising new applications in electronics. Thin carbon films has been deposited by pulsed laser ablation on Si <100> substrates, kept at temperatures ranging from RT to 800 °C, from a rotating graphite target operating in vacuum ($\approx 10-4 Pa$). The laser ablation of the graphite target was performed by pulsed ArF (lambda = 193 nm, tau?= 10 ns, ni?= 10 Hz, phi?? 5÷7 J/cm2 ) and pulsed Nd:YAG laser, operating both in the Visible (lambda = 532 nm, tau?= 7 ns, ni?= 10 Hz, phi?? 7-15 J/cm2 ) and in the near IR (lambda = 1064 nm, tau?= 7 ns, ni?= 10 Hz, phi?? 10-30 J/cm2 ). X-ray diffraction analysis, performed at grazing incidence (G-XRD), established the progressive formation of nano-sized graphene structures, as the deposition temperature was increased. The films obtained at higher temperatures show higher macroscopic roughness (SEM, AFM) compared to the lower temperature deposited samples, characterised by an amorphous structure and very smooth surface. The film density, evaluated by x-ray reflectivity measurements, is also strongly affected both by laser energy and substrate temperature. These structural property modifications induce relevant variation on the emission properties of the samples, as evidenced by Field Emission measurements. The nanostructure formation and texturing is strongly related to the substrate temperature: increasing temperature the carbon plume expanding in vacuum gives rise to structures varying from almost amorphous to aromatic nano-particles formed by vertically oriented graphene layers, growing with the ? axis parallel to the Si substrate; all the while the film thickness increases and the density undergo a parallel decreasing. The presence of He atmosphere in the reaction chamber changes basically the particle nucleation process: a clustering phenomenon of aromatic structures is promoted in the gas phase also at low temperature. The nano-structured particles, however, are characterised by a round shaped morphology and random orientation. The mass density of deposited films is also strongly dependent on the experimental settings: films grown in the inert gas show lower density compared to the vacuum deposited ones. The preferential growth direction of aromatic planes in vacuum and high temperature can be explained as the end-effect of different kinetic processes: the propagation line of the carbon “plume”, the thermal ad-atoms diffusion and the preferential in-plane formation of aromatic bonds, while the density decreasing could be ascribed to the very fast out-of-equilibrium growth and the high re-dissociation process at the heated surface. .