The first segment of this tutorial was presented by Andre Pineau. It covered the fundamentals of ductile and brittle (cleavage and intergranular) fracture in metals, in particular in steels and aluminum alloys. A comprehensive review of what is called the “local approach to fracture” (LAF) was given. This approach to fracture was introduced in the early 1980s, and is largely based on a detailed study of the micromechanisms of failure, in contrast to the conventional “global” approaches derived from fracture mechanics.

The second part of the tutorial, presented by Benoit Tanguy, was devoted to the application of the local approach to fracture to practical situations for materials in service. The variation of the brittle fracture toughness, KIc, with temperature (for a given thickness and a given strain rate) can be simply predicted with only two parameters. The Weibull theory was used to predict the variation of KIc with specimen thickness and loading rate. The effects of metallurgical inhomogeneities and non-isothermal loading (Warm Prestress Effect) were also considered. A similar approach for ductile fracture was introduced. Both approaches (ductile and brittle) were used to show how the ductile-to-brittle transition in ferritic steels can be interpreted. A special emphasis was placed on the effect of irradiation in nuclear components on the shift of the ductile-to-brittle transition temperature. Very recent results showing the variation of inter-granular fracture toughness with the amount of impurities (P, C) segregated at grain boundaries will be presented. These results illustrate the predictive potential of the LAF methodology when applied to structural steels.

In 1833, Faraday combined silver and sulfur and discovered the first material with a negative temperature coefficient of resistance, silver sulfide. At the time, the word semiconductor did not even exist. Yet we now know that this first semiconducting material laid the foundation for an entirely new and extremely important class of electronic materials. Today, a similar revolution is unfolding for optical materials. Textbook conceptions of light-matter interactions, such as the notions of exclusively positive refractive indices and reciprocal light propagation, are being redefined by new optical materials. These materials allow light to be controlled in ways previously thought impossible, providing techniques to circumvent the diffraction limit of light and tune both electric and magnetic light-matter interactions. In this presentation, I will describe my group’s efforts to develop such new optical materials, and use them to directly visualize, probe, and control nanoscale systems and phenomena – particularly those relevant to energy and biology. We first explore the optical (i.e., plasmonic) resonances of individual metallic nanoparticles as they transition from a classical to a quantum-influenced regime. We then use these results to monitor heterogeneous catalytic reactions on individual nanoparticles. Subsequently, using real-time manipulation of plasmonic nanoparticles, we investigate the effects of classical-coupling and quantum tunneling between metallic particles on their optical resonances. By utilizing these effects, we demonstrate the colloidal synthesis of an isotropic metafluid or "metamaterial paint" that exhibits a strong magnetic response – and the potential for negative refractive indices – at visible frequencies. Finally, we introduce a new technique, cathodoluminescence tomography, that enables three-dimensional visualization of light-matter interactions with nanoscale spatial and spectral resolution.

The use of biologically derived materials is increasingly finding application and utility in the technological domains. Among natural materials, silk has proven particularly interesting for its properties—specifically, the ability to exist in more than one form (either metastable or stable). This material polymorphism offers the opportunity to explore multiple applications that hinge on the ability to control silk’s structure, morphing a natural fiber into multiple technologically relevant formats.
This talk will describe the transformation process of native silk fibers into engineered nanoscale materials and their applications. Such materials embody a confluence of form and function, and enable a series of approaches in the optical and electronic domains that operate at the interface of biology and technology.