Scientific Events

Defects and Grain boundaries have a remarkable effect on the thermal and electrical transport properties of polycrystalline materials but are often ignored by prevailing physical theories. The concentration of point defects can be altered with phase boundary mapping considering the defect thermodynamics. Thus, the properties can be engineered with careful processing control. Grain boundaries and interfaces can adversely alter the thermal and electrical properties of Power Electronics, Solar Cells, Batteries, Thermoelectrics and permanent magnets such as interfacial electrical and thermal resistance (Kapitza resistance). Interfacial thermal resistance limits the performance of power electronics because of overheating. New scanning thermal reflectance techniques can image the thermal resistance of interfaces and boundaries directly. The Thermal conductivity suppression at grain boundaries can even be imaged showing that different grain boundaries can have very different thermal resistances with high energy grain boundaries having more resistance and low energy boundaries having lower thermal resistance. Interfaces and grain boundaries are 2-dimensional thermodynamic phases (complexions) that have distinct energy, composition and properties that can be rigorously described using the Gibbs excess formalism. The common thermodynamic quantities of temperature and chemical potential connects the complexions to the 3-D phases allowing a phase boundary mapping of grain boundary and interface properties similar to that for point defects. [more]
This lecture explores the design of luminescent materials by examining the balance between radiative and non-radiative decay processes, focusing on rare-earth and transition-metal-based LED phosphors as well as lanthanoid-based luminescent thermometers. It highlights both sustainability challenges and fundamental limits in temperature sensing, offering insights into improving material efficiency through deeper understanding of non-radiative transitions. [more]

Towards more sustainable uses of rare earth elements - from an inorganic and biological perspective

Colloquia Series on Sustainable Metallurgy
Lanthanides (Ln) - the f-elements from Ce to Lu, along with La - are indispensable for modern life. These elements are at the heart of advancements in green energy technologies, energy-efficient lighting, and various industrial and medical applications. [more]

Fracture at the Two-Dimensional Limit

Two-dimensional (2D) materials, such as Graphene, hBN, and MoS2, are promising candidates in a number of advanced functional and structural applications owing to their exceptional electrical, thermal, and mechanical properties. Understanding the mechanical properties of 2D materials is critically important for their reliable integration into future electronic, composite, and energy storage applications. In this talk, we will report our efforts to study the fracture behaviors of 2D materials. Our combined experiment and modelling efforts verify the applicability of the classic Griffith theory of brittle fracture to graphene [1]. Strategies on how to improve the fracture resistance in graphene, including a nanocomposite approach, and the implications of the effects of defects on mechanical properties of other 2D atomic layers will be discussed [2, 3]. More interestingly, stable crack propagation in monolayer 2D h-BN is observed and the corresponding crack resistance curve is obtained for the first time in 2D crystals [4]. Inspired by the asymmetric lattice structure of h-BN, an intrinsic toughening mechanism without loss of high strength is validated based on theoretical efforts, enabling stable crack propagation not seen in graphene. Finally, we will also discuss some of our recent efforts in evaluating the mechanical properties of 2D covalent organic frameworks (COFs) [5, 6] and the fracture behaviors of ultrathin van der Waals solids [7] [more]
Organisers:Erik Bitzek (Max-Planck-Institut for Sustainable Materials), James Kermode (University of Warwick), Gianpietro Moras (Fraunhofer IWM), Lars Pastewka (University of Freiburg), Céline Varvenne (CNRS) [more]
The workshop will bring together leading scientist in from both theory and experiment investigating electron-transfer dynamics at interfaces to discuss possibilities, requirements and challenges for the predictive modelling of electron-transfer dynamics, with a focus on electrochemical solid/liquid interfaces. [more]

Temperature dependence of hydrogen embrittlement

The defactant concept allows to predict why at higher temperature the formation energy of vacancies, dislocations and surfaces is no longer decreased by hydrogen, because it is not trapped to these defects any more. Thus failure due to hydrogen embrittlement is not present at high temperatures. At low temperatures the diffusion of hydrogen to defect generated by deformation will be reduced and, therefore, the decrease of defect formation energy by segregated hydrogen will not occur. Based on these scenarios equations for crack growth or strain to failure are derived and compared with experimental result for power law creep, stress-strain tests and fatigue. [more]
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