Research at Applied Materials Group

Additive Manufacturing (AM) is a technology that produces three-dimensional parts layer by layer from a material. A key concern in metal additive manufacturing is the density and structural integrity of a part formed. A great variety of processing parameters have influence on the final density, microstructure and residual stresses in a built part and thus they need to be optimized to avoid build failures such as porosity and cracks, but also geometrical distortions and faults of often complex structures as well as premature failure. Neutron imaging enables us to visualize and analyse such defects deep in the bulk of specimen, which allows to optimize build conditions, inform and develop simulations as well as sensors for printing technologies.

Engineering materials experience deformation during service, often in a cyclic nature. During the past decades, new materials compositions and new thermomechanical processing have emerged which have provided materials with enhanced strength, ductility and fatigue resistance. However, the recent advances in additive manufacturing, open new opportunities for realizing complex and optimized materials within a single component by manipulating the additive manufacturing process parameters.

The water balance in living plants serves a vital role from extracting water from the soil to transporting it to the shoot as well as throughout the plant and for sustaining transpiration. To fulfill these functions plants and their specific parts have a complex anatomical structure with varying cell layers of e.g. varying hydraulic conductivities. This behavior includes the rhizosphere, which is the soil fraction close to the roots in which the chemistry and microbiology are influenced by their growth, respiration, and nutrient exchange.

Hydrogen is the ultimate renewable energy carrier. The hydrogen cycle includes applications utilizing very high pressures. The investigations of matter (be it liquids for the transport or metal hydrides for hydrogen storage) under pressure, thus, contribute to the cornerstones for reaching the CO2 emission free energy goal.

Polymer electrolyte fuel cells (PEFC) generate clean electric power through electrohcemical reactions of hydrogen and oxygen gas. PEFCs are considered as one of the powertrains in electric vehicles. The technical challeges of PEFCs (e.g., material degradation, mass transport limitation, and ionic conductivity) stem from an accmulation of product water in internal components. At the imaging beamlines of AMG at SINQ, we are obtaining maps of the water content evolution and distributions in operating PEFCs to enable technological optimisation and pioneer material development for improved performance, lifetime and cost reduction.

Electric steels are indispensible elements of electric machinery and constitute with about 12 million tons per year 95% of the produced soft magnetic materials. They are produced as GRO, grain oriented, and NOR, non-grain oriented steel sheets for applications with a well defined magnetisation direction, like in transformers, or isotropic magnetisation behavior as required in motors or generators, respectively. The key magnetic properties of these materials include their magnetic hysteresis, remanence, saturation and losses, all of which are tied to their domain structure. Thus, the design and conservation of advantageous domain structures throughout the production process of electric machines are of outstanding importance for high energy efficiency. Neutron imaging provides unique insights to the underlying domain structure as it can access the bulk even through the typical coatings that electrical steel sheets require for isolation between each other when assembled.

Nuclear materials related to nuclear energy and safety are still of very high relevance and will remain of high importance for decades. Neutron imaging of nuclear and activated materials has a long tradition due to the penetration power and contrast of neutron attenuation including isotope sensitivity. The recently developed experimental infrastructure for high-resolution neutron imaging of highly activated samples will prove to be extremely useful tool for investigations of nuclear fuel claddings and other highly radioactive samples.

Metals are vital for modern societies and for Europe`s key industries to manufacture accurate, customized parts for automotive, aerospace and healthcare applications. Today, metal production still relies largely on experience derived from a trial-and-error approach. Resource efficiency and other challenges demand a paradigm shift in metal production and new materials, e.g. metal matrix composites. The opacity of metals poses a main obstacle to elucidating metal characteristics during processing, phase changes or the impact of interventions.  

Concrete is one of the most applied materials on Earth and constitutes the basis of modern infrastructure. Cementitious materials are an effective, relatively inexpensive and abundant resource. However, the vast volume of concrete needed amounts to immense costs involved. Immense costs are also related to the maintenance of concrete structures and the quality and the optimization of concrete for specific applications. Neutron imaging are used for numerous research questions regarding the durability of concretes and other cementitious materials.

Diffraction contrast neutron imaging [1] often referred to as Bragg edge imaging, is based on the wavelength dependent impact of neutron diffraction at crystal lattice planes on the transmission. A Bragg edge can be observed in the attenuation spectrum at a wavelength where for a specific crystal lattice parameter d_hkl  the Bragg condition reduces to λ=2d as the diffraction angle reaches θ=90°. Thus, beyond such wavelength no Bragg scattering can take place this lattice plane family anymore and the transmission correspondingly increases sharply. This also implies, that for powder-like polycrystalline materials the Bragg edges directly measure the lattice spacings and allow identifying crystalline phases. The exact position of edges carries also information on lattice strains and the overall pattern can be analysed for other microstructural features such as grain size and texture variations. For single- or large grained oligo-crystals on the other hand diffraction contrast allows to index and map grains or orientation distributions [2]

Time is essential in many experiments, in particular, if processes are studied. We may want to how liquids move through porous media, quantify the shape of a solidification front. These are processes on the time scale of neutron imaging and have often been studied using time series of radiographs. The problem is that changes caused by the evolving process in many cases must be studied in three dimensions. Therefore, we need time-resolved tomography using methods like golden ratio and on-the-fly scans.

A key element for the validation of continuum plasticity models is their ability to model the mechanical behavior of materials under multiaxial loading states, which occur during operation or metal forming processes. It is thus essential to formulate the criteria to be implemented in micromechanical models, for which constitutive equations are now relying solely on a knowledgebase derived from uniaxial testing.

The neutron diffractometer POLDI features a unique multiaxial loading rig which allows multiaxial loading and strain path changes while neutron diffraction measurements are undertaken.  Utilizing the multiaxial machine at POLDI, groundbreaking insights into the mechanical behavior and deformation-induced transformations have been obtained the past year at the Paul Scherrer Institute.