Advanced Materials

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Materials Characterization


graphitic layers viewed at 2 nmCharacterization of materials is a key capability enabling the structure and functionality of materials to be understood, as well as the chemical processes occurring at interfaces, such as those that occur in catalysis, corrosion, and fluid transport. ORNL develops and applies a broad range of electron microscopy and electron spectroscopy techniques to provide insight into the structure and composition of materials at the atomic level. Transmission electron microscopy approaches probe functionalities (electronic structure, magnetism, etc.) and explore materials in operando, using a variety of controlled environments. A variety of scanning probe modalities have been developed to provide both atomic and nanoscale information on materials, including electronic and magnetic behaviors. Chemical imaging, which includes specialized scanning probes combined with optical and mass spectrometry techniques, can provide a wealth of information on chemistry occurring at surfaces. Another area of specializion, atom probe tomography, yields a complete three-dimensional atom-by-atom reconstruction of a specimen. Many of these capabilities are available to the scientific community through the Center for Nanophase Materials Sciences (CNMS) and the Shared Research Equipment (ShaRE) program, both of which are DOE Basic Energy Sciences user facilities. ORNL has state-of-the-art capabilities for examining a range of materials—from geological to biological materials—using nuclear magnetic resonance and mass spectrometry.

In addition to atomic and nanoscale characterization, ORNL has a comprehensive suite of mechanical materials characterization tools, ranging from routine stress/strain testing to specialized nanoindentation techniques used to examine the effects of defects in materials. ORNL also has developed a a suite of characterization techniques specially designed for use in post-irradiation examination of materials. Finally, ORNL is home to two major neutron sources that are utilized for a wide range of different neutron-based materials characterization measurements: the High Flux Isotope Reactor (HFIR) and the Spallation Neutron Source (SNS). These resources are used to study structure of a variety of materials, such as superconductors, advanced alloys and polymers. In addition, many neutron scattering techniques combined with isotopic labeling allow detailed insight into dynamics observed in catalysis, water transport through membranes and lithium transport at battery electrode surfaces. Thus, ORNL has a comprehensive set of characterization tools allowing materials to be understood from the atomic to system level.

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1-3 of 3 Results
 

Polar ordering induced by oxygen vacancies
— A combination of scanning transmission electron microscopy (STEM), electron energy loss spectroscopy (EELS) and density functional theory (DFT) calculations show that it is possible to achieve polar order in a superlattice made up of two non-polar oxides by means of oxygen vacancy ordering.

Stable Nanopores in Graphene
— The existence of stable holes in graphene has been demonstrated. This is a major step toward the development of robust and reliable graphene-based nanopore devices that could be used, for example, in DNA sequencing.

Clues for absence of superconductivity in an iron-based material
— The electronic properties of CaFe2As2, using a combination of bulk transport measurements and surface photoemission spectroscopy, have revealed reasons for the lack of superconductivity. These results support the suggested role of magnetism and spin fluctuations in iron-based superconductors.

 
 
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