MAN

Mechanical Analysis of Nanocomposites: an experimental and computational study of the mechanical behavior of polycrystalline and tough nanocomposite structures

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 Obiettivo del progetto (Objective)

'Nanocomposite structures show enhanced mechanical properties (hardness and toughness) which are very interesting for protective purpose. The mechanical behavior of those materials is still not clear, and many different explanations (often contradictory) are present in the literature, which makes difficult the practical application of Nanocomposites. This project proposes to study the deformation mechanisms of these structures by a combined experimental and theoretical (computational) approach. This original approach will allow understanding phenomena which were still unapproachable until a few years ago and to clarify at once, the particular behavior of Nanocomposite structures. From the experimental side, a set of thin films with the abovementioned structures will be prepared by magnetron sputtering and characterized by several techniques, such as XRD, TEM, EELS, SEM, XPS, etc. Mechanical properties will be measured by nanoindentation. Further specific measurements will also be done for some selected samples, in order to evaluate “in situ” the deformation of these materials under stress by SEM, TEM/ED and XRD from a synchrotron source. From the theoretical side, molecular dynamics (MD) simulations will be done to evaluate the role of the crystal size, phase composition and presence of impurities in nanocomposite structures (and polycrystalline ones for comparison). The new knowledge, know-how and tools developed during this project will contribute to bring EU on the forefront of nanocomposite structures and their applications. Together with a training aiming at expending both technical skills (e.g in the field of nanoindentation, diffraction, TEM) and soft-skills (e.g. science management), this project will allow placing the candidate on his path for becoming a leading expert in the field of nanocomposites. In conclusion, this project will have a great impact not only on the researcher, but also on the participating institutions, and in Europe by extension.'

Introduzione (Teaser)

Scientists conducted experimental and theoretical investigations of composites with nano-scale structures. Outcomes point to optimal formulations for enhanced strength.

Descrizione progetto (Article)

Nanomaterials show unique properties not exhibited by their bulk counterparts largely due to their very high surface area to volume ratios. Nanocomposites made up of two or more different materials can further enhance properties through the combination of individual ones and their interactions. They have become the subject of intense research and development as the building blocks of novel devices in virtually every field imaginable.

Improvement in durability and strength is of particular interest for materials operating under conditions of extreme environmental conditions, large stresses or repetitive loading cycles. The formation and propagation of cracks can be prevented through the careful control of micro- and nanostructure. Embedding a hard-phase material in a soft matrix results in improved protection but the behaviour of the material under stress is not well understood.

Scientists working on the EU-funded MAN project took a simple system of titanium carbide (TiC) nanocrystals embedded in an amorphous carbon (a-C) matrix to study this behaviour in detail through a combination of experimental and theoretical investigations. Molecular dynamics simulations of deformation elucidated the behaviours associated with crack formation and propagation in response to stress. Taken into account were the directional dependence related to both the stress direction as well as the crack orientation with respect to the materials boundaries.

Overall, project scientists demonstrated that the propagation of cracks in the a-C phase (more brittle than the TiC phase) is hindered by the presence of TiC. Continued work is expected to result in delineation of the optimal phase ratio and grain shape for the highest fracture toughness in nanocomposites.

MAN outcomes are applicable in most fields where durability is a consideration. These include adverse environmental conditions, when materials are subject to high stresses, or under repetitive loading cycles.