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Matteo Nicoli

Bio: Matteo Nicoli is an academic researcher from École Polytechnique. The author has contributed to research in topics: Nonlinear system & Critical exponent. The author has an hindex of 13, co-authored 25 publications receiving 324 citations. Previous affiliations of Matteo Nicoli include Northeastern University & Charles III University of Madrid.

Papers
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Journal ArticleDOI
TL;DR: The results demonstrate that the bifurcation from propagating a planar to segmented crack front is strongly subcritical, reconciling previous theoretical predictions of linear stability analysis with experimental observations and show that facet coarsening is a self-similar process driven by a spatial period-doubling instability of facet arrays.
Abstract: A planar crack generically segments into an array of "daughter cracks" shaped as tilted facets when loaded with both a tensile stress normal to the crack plane (mode I) and a shear stress parallel to the crack front (mode III). We investigate facet propagation and coarsening using in situ microscopy observations of fracture surfaces at different stages of quasistatic mixed-mode crack propagation and phase-field simulations. The results demonstrate that the bifurcation from propagating a planar to segmented crack front is strongly subcritical, reconciling previous theoretical predictions of linear stability analysis with experimental observations. They further show that facet coarsening is a self-similar process driven by a spatial period-doubling instability of facet arrays.

46 citations

Journal ArticleDOI
TL;DR: The morphologically unstable condition to be nontrivial for a family of stochastic equations of experimental relevance, paradigmatically including the Michelson-Sivashinsky system, and the asymptotic dynamics is scale invariant with dimension-independent exponents reflecting a hidden Galilean symmetry.
Abstract: Nonlocal effects occur in many nonequilibrium interfaces, due to diverse physical mechanisms like diffusive, ballistic, or anomalous transport, with examples from flame fronts to thin films. While dimensional analysis describes stable nonlocal interfaces, we show the morphologically unstable condition to be nontrivial. This is the case for a family of stochastic equations of experimental relevance, paradigmatically including the Michelson-Sivashinsky system. For a whole parameter range, the asymptotic dynamics is scale invariant with dimension-independent exponents reflecting a hidden Galilean symmetry. The usual Kardar-Parisi-Zhang nonlinearity, albeit irrelevant in that parameter range, plays a key role in this behavior.

38 citations

Journal ArticleDOI
TL;DR: In this paper, the authors provide a quantitative assessment of a continuum description of CVD interface growth, identifying non-locality, non-conservation and randomness as the main general mechanisms controlling the formation of these ubiquitous shapes.
Abstract: Chemical vapor deposition (CVD) is a widely used technique to grow solid materials with accurate control of layer thickness and composition. Under mass-transport-limited conditions, the surface of thin films thus produced grows in an unstable fashion, developing a typical motif that resembles the familiar surface of a cauliflower plant. Through experiments on CVD production of amorphous hydrogenated carbon films leading to cauliflower-like fronts, we provide a quantitative assessment of a continuum description of CVD interface growth. As a result, we identify non-locality, non-conservation and randomness as the main general mechanisms controlling the formation of these ubiquitous shapes. We also show that the surfaces of actual cauliflower plants and combustion fronts obey the same scaling laws, proving the validity of the theory over seven orders of magnitude in length scales. Thus, a theoretical justification is provided, which had remained elusive so far, for the remarkable similarity between the textures of surfaces found for systems that differ widely in physical nature and typical scales.

34 citations

Journal ArticleDOI
TL;DR: In this paper, the authors provide a quantitative assessment of a continuum description of CVD interface growth, identifying non-locality, non-conservation, and randomness as the main general mechanisms controlling the formation of these ubiquitous shapes.
Abstract: Chemical vapor deposition (CVD) is a widely used technique to grow solid materials with accurate control of layer thickness and composition. Under mass-transport-limited conditions, the surface of thin films thus produced grows in an unstable fashion, developing a typical motif that resembles the familiar surface of a cauliflower plant. Through experiments on CVD production of amorphous hydrogenated carbon films leading to cauliflower-like fronts, we provide a quantitative assessment of a continuum description of CVD interface growth. As a result, we identify non-locality, non-conservation, and randomness as the main general mechanisms controlling the formation of these ubiquitous shapes. We also show that the surfaces of actual cauliflower plants and combustion fronts obey the same scaling laws, proving the validity of the theory over seven orders of magnitude in length scales. Thus, a theoretical justification is provided, that had remained elusive thus far, for the remarkable similarity between the textures of surfaces found for systems that differ widely in physical nature and typical scales.

28 citations

Journal ArticleDOI
TL;DR: A moving-boundary model of nonconserved interface growth that implements the interplay between diffusive matter transport and aggregation kinetics at the interface is studied and the form of the linear dispersion relation of the IEE changes drastically for slow or for instantaneous attachment kinetics.
Abstract: We study a moving-boundary model of nonconserved interface growth that implements the interplay between diffusive matter transport and aggregation kinetics at the interface. Conspicuous examples are found in thin-film production by chemical vapor deposition and electrochemical deposition. The model also incorporates noise terms that account for fluctuations in the diffusive and attachment processes. A small-slope approximation allows us to derive effective interface evolution equations (IEEs) in which parameters are related to those of the full moving-boundary problem. In particular, the form of the linear dispersion relation of the IEE changes drastically for slow or for instantaneous attachment kinetics. In the former case the IEE takes the form of the well-known (noisy) Kuramoto-Sivashinsky equation, showing a morphological instability at short times that evolves into kinetic roughening of the Kardar-Parisi-Zhang (KPZ) class. In the instantaneous kinetics limit, the IEE combines the Mullins-Sekerka linear dispersion relation with a KPZ nonlinearity, and we provide a numerical study of the ensuing dynamics. In all cases, the long preasymptotic transients can account for the experimental difficulties in observing KPZ scaling. We also compare our results with relevant data from experiments and discrete models.

25 citations


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Journal ArticleDOI
TL;DR: This review discusses the current state of the art on how soft materials break and detach from solid surfaces and defines the important length scales in the problem and in particular the elasto-adhesive length Γ/E, which controls the fracture mechanisms.
Abstract: Soft materials are materials with a low shear modulus relative to their bulk modulus and where elastic restoring forces are mainly of entropic origin. A sparse population of strong bonds connects molecules together and prevents macroscopic flow. In this review we discuss the current state of the art on how these soft materials break and detach from solid surfaces. We focus on how stresses and strains are localized near the fracture plane and how elastic energy can flow from the bulk of the material to the crack tip. Adhesion of pressure-sensitive-adhesives, fracture of gels and rubbers are specifically addressed and the key concepts are pointed out. We define the important length scales in the problem and in particular the elasto-adhesive length Γ/E where Γ is the fracture energy and E is the elastic modulus, and how the ratio between sample size and Γ/E controls the fracture mechanisms. Theoretical concepts bridging solid mechanics and polymer physics are rationalized and illustrated by micromechanical experiments and mechanisms of fracture are described in detail. Open questions and emerging concepts are discussed at the end of the review.

507 citations

01 Nov 1992
TL;DR: In this article, a class of phase-field models for crystallization of a pure substance from its melt are presented, which are based on an entropy functional, and are therefore thermodynamically consistent inasmuch as they guarantee spatially local positive entropy production.
Abstract: In an effort to unify the various phase-field models that have been used to study solidification, we have developed a class of phase-field models for crystallization of a pure substance from its melt. These models are based on an entropy functional, as in the treatment of Penrose and Fife, and are therefore thermodynamically consistent inasmuch as they guarantee spatially local positive entropy production. General conditions are developed to ensure that the phase field takes on constant values in the bulk phases. Specific forms of a phase-field function are chosen to produce two models that bear strong resemblances to the models proposed by Langer and Kobayashi. Our models contain additional nonlinear functions of the phase field that are necessary to guarantee thermodynamic consistency.

459 citations

Journal ArticleDOI
TL;DR: A review of the basic approaches for hydraulic fracture simulation can be found in this article, where the authors discuss both continuum and meso-scales numerical methods as well as engineering models which typically make use of additional assumptions to reduce computational cost.

280 citations

Journal ArticleDOI
TL;DR: In this article, the main experimental results and applications are described under the light of the recently established evidence on the key role played by simultaneous impurity incorporation during irradiation, which has opened a new scenario for an improved understanding of the phenomenon.
Abstract: In recent years Ion Beam Sputtering (IBS) has revealed itself as a powerful technique to induce surface nanopatterns with a large number of potential applications. These structures are produced in rather short processing times and over relatively large areas, for a wide range of materials, such as metals, insulators, and semiconductors. In particular, silicon has become a paradigmatic system due to its technological relevance, as well as to its mono-elemental nature, wide availability, and production with extreme flatness. Thus, this review focuses on the IBS nanopatterning of silicon surfaces from the experimental and the theoretical points of view. First, the main experimental results and applications are described under the light of the recently established evidence on the key role played by simultaneous impurity incorporation during irradiation, which has opened a new scenario for an improved understanding of the phenomenon. Second, the progress and state-of-art of the theoretical descriptions of the IBS nanopatterning process for this type of targets are discussed. We summarize the historical approach to IBS through simulation techniques, with an emphasis on recent information from Molecular Dynamics methods, and provide a brief overview of the earlier and most recent continuum models for pure and compound systems.

139 citations

Journal Article
TL;DR: In this article, it was shown that yielding or flow of a material is not required in order for fingering to be initiated in a confined material and that the instability is driven by the release of lateral constraints within a confined elastic layer and is observed when the lateral confinement significantly exceeds the thickness of the elastic layer.
Abstract: Fingering instabilities similar to those commonly observed in viscous systems have been observed in purely elastic layers that are strained in tension. The instability is driven by the release of lateral constraints within a confined elastic layer and is observed when the lateral confinement significantly exceeds the thickness of the elastic layer. Our results show convincingly that yielding or flow of a material is not required in order for fingering to be initiated in a confined material.

103 citations