Physics Colloquium: 3D orientation mapping of crystalline materials at multiple length-scales utilizing Neutrons, Photons and Electrons

Event Details

  • Speaker(s): Søren Schmidt
  • Date:
  • Time: 3:30 PM
  • Location: MacN 101

Abstract

Polycrystalline materials are ubiquitous in Nature (rocks, sand, ice, bones) and form the basis of much of modern industry (metals, ceramics, some semiconductors). The physical and mechanical properties of these materials are strongly dependent on the local structure, both on the scale of the individual crystal-lites and averaged over all the crystals within a small sub-volume of the entire specimen. Notably most materials phenomena such as conduction paths, cracks, plastic response etc. are 3D in nature. In this presentation an overview of three non-destructive characterization techniques targeting multiple length-scales are given along with a range of applications:

With Photons:
The 3DXRD (Three Dimensional X-ray Diffraction) methodology [1] for non-destructive characterization of individual grains in polycrystalline materials at the micrometer length scale has been around for more than a decade. The first implementation, the 3DXRD microscope, is situated at beamline ID-11 at the Euro-pean Synchrotron Radiation Facility (ESRF) developed in collaboration between Risoe (now Technical Uni-versity of Denmark) and ESRF. Although initially motivated by materials science, especially within metal-lurgy, a wide range of other fields such as geology, structural biology and chemistry, have benefitted from this technique. In metallurgy the ability to monitor the evolution in the local strain free region during heat treatments has proven very successful in studying recovery, recrystallization and grain growth mecha-nisms [2]. Likewise for in-situ deformation studies of individual grains, such as grain rotations, stress and strain tensor measurements, and lately, evolution of the local deformed bulk microstructure.

With Neutrons:
Three Dimensional Neutron Diffraction – 3DND – is a novel technique. In comparison to X-rays the spatial resolution is coarser but the specimens can be an order of magnitude larger and sample environments more complex. This work is done in collaboration with the European Spallation Source (ESS) in Lund, Swe-den.

With Electrons:
Nanocrystalline materials (i.e. polycrystalline aggregates where the individual crystallites/grains or parti-cles have sizes below 100 nm) are formed through various processes ranging from mechanical treatments of bulk materials, to electrodeposition of thin films and coatings to aggregation of nanoparticles. The ma-terials constitute one of the most rapidly growing new classes of materials and exhibit enhanced proper-ties ranging from high strength and wear resistance, to unique functional characteristics, which open up a large spectrum of applications e.g. for micro- and nano-electro-mechanical systems (MEMS and NEMS). A novel methodology for obtaining 3D orientation maps non-destructively with spatial resolution of 1 nm in nanocrystalline samples with few hundreds nm thickness are presented: 3D Orientation Mapping in Trans-mission Electron Microscope – 3D-OMiTEM [3]. The method utilizes conical dark field scanning mode for data acquisition, where images are collected over a wide range of beam and sample tilts.