CHESS DMR-0936384 2013

Proposed indirect exchange mechanism of O diffusion in the ε-Co phase takes place over three steps (a)−(d): (a)−(b) O atom in a vacant type I site diffuses to an adjacent interstitial site; (b)−(c) neighboring type I Co atom diffuses to site vacated by O; (c)−(d) O hops back into the empty type I site.

D. H. Ha, L. M. Moreau, S. Honrao, R. G. Hennig and R. D. Robinson, The Oxidation of Cobalt Nanoparticles into Kirkendall-Hollowed CoO and Co3O4: The Diffusion Mechanisms and Atomic Structural Transformations, J Phys Chem C 117(27), 14303-14312 (2013).

Intellectual Merit: The Robinson Group in the Materials Science and Engineering department at Cornell University has discovered a simple air oxidation process which produces polycrystalline Co3O4 nanoparticles with a high ratio of {110} surface planes - making them ideal for use as catalysts. Information about both long- and short-range order in the nanoparticles throughout the air oxidation process was measured using X-ray diffraction and extended X-ray absorption fine structure respectively at the CHESS C1 end station. Interestingly, although the diffraction pattern of the starting material shows only a single-crystalline cobalt phase, extended X-ray absorption fine structure (EXAFS) reveals the presence of an amorphous CoO phase. The combination of X-ray diffraction and EXAFS allows for a much deeper understanding of the air oxidation process, allowing for identification of intermediate phases not “seen” by diffraction alone.

New process discovered to create Cobalt nanoparticle catalysts

Joel Brock, Cornell University, DMR 0936384

CHESS DMR-0936384 2013

Cover featured paper: D. H. Ha, L. M. Moreau, S. Honrao, R. G. Hennig and R. D. Robinson, The Oxidation of Cobalt Nanoparticles into Kirkendall-Hollowed CoO and Co3O4: The Diffusion Mechanisms and Atomic Structural Transformations, J Phys Chem C 117(27), 14303-14312 (2013).

Broader Impacts: The facile synthesis of novel materials is necessary to tackle ever growing global energy demands. Cobalt oxide nanomaterials, in particular Co3O4 nanoparticles, are promising candidates for use in electrocatalysts, batteries, and supercapacitors. The Robinson Group in the Materials Science and Engineering department at Cornell University have discovered a simple air oxidation process which produces polycrystalline Co3O4

nanoparticles with a high ratio of {110} surface planes making them ideal for use as catalysts. Attempts to obtain Co3O4 nanoparticles from the analogous solution-phase process did not produce Co3O4 even after reacting at 200 for 3 hours, whereas air oxidation goes completely to high quality Co3O4 in only 90 minutes. The Co3O4 nanoparticles could then be easily dispersed in an organic solvent making them an ideal source of solution-processed colloidal, monodispersed Co3O4 nanoparticles for use as industrial catalysts.

New process discovered to create Cobalt nanoparticle catalysts

Joel Brock, Cornell University, DMR 0936384

CHESS DMR-0936384 2013

Real-world conditions to study real material behaviorJoel Brock, Cornell University, DMR 0936384

Diffractometer installed at CHESS A2 end station. The x-ray beam enters the furnace through the white ceramic window shown at right, and exits to record diffraction data on a large area detector (not shown) to the left.

B. B. Oswald, J. C. Schuren, D. C. Pagan, and M. P. Miller. An experimental system for high temperature X-ray diffraction studies with in situ mechanical loading. Review of Scientific Instruments, 84:033902, 2013.

Intellectual Merit: Even though a metal seems like a strong material, everyone knows a metal paper clip can be broken quite easily by bending it back and forth ten or twenty times. This type of repetitive use, or cyclic loading, leads to failure of everything from auto components to door hinges to plastic utensils. In the engineering world, understanding failure and predicting failure of parts and materials is important, yet a complete understanding of the processes which lead to failure remains incomplete. One powerful and nondestructive method for monitoring material behavior, such as deformation and failure, is high energy x-ray diffraction. A group of Cornell engineers in the research group of Professor Matt Miller (Mechanical and Aerospace Engineering) has designed and built an instrument to perform in situ mechanical and high-temperature thermal loading while recreating the extreme environments some engineering components need to withstand. The instrument can be used to predict failure in such materials by validating complex material models.

CHESS DMR-0936384 2013

X-ray diffraction data are reduced to calculate compressive (negative) and tensile (positive) strains inside a LSHR nickel-based superalloy held at 550◦ C. The macroscopic load is applied along the z axis. Plotted on a sphere to display all known angular dependence, these pole figures show that the microscopic stress-strain response is different for the four crystallographic lattice planes {hkl}s within the superalloy.

B. B. Oswald, J. C. Schuren, D. C. Pagan, and M. P. Miller. An experimental system for high temperature X-ray diffraction studies with in situ mechanical loading. Review of Scientific Instruments, 84:033902, 2013.

Broader Impacts: In the engineering world, understanding failure and predicting failure of parts and materials is important, yet a complete understanding of the processes which lead to failure remains incomplete. In addition to worrying about failure, engineers are also concerned with system efficiency. Many systems, such as automobile engines, run more efficiently at higher operating temperatures. Improving efficiency has enormous technical and economical relevance. A group of Cornell engineers in the research group of Professor Matt Miller has designed and built an instrument to perform in situ mechanical and thermal loading while recreating the extreme environments some engineering components need to withstand. High-energy X-ray diffraction is one of a few reliable, non-destructive probes of the microstructure of a material, providing information about the spacing of atoms which can be related to concepts like stress, strain, fatigue and failure.

Real-world conditions to study real material behaviorJoel Brock, Cornell University, DMR 0936384

CHESS DMR-0936384 2013

CHESS Graduate Student Wierman wins prestigious Etter Award

Joel Brock, Cornell University, DMR 0936384

Cryocooled thaumatin crystals wrapped in three layers of graphene on a Hampton cryoloop.

J. L. Wierman, J. S. Alden, C. U. Kim, P. L. McEuen, and S. M. Gruner. Graphene as a protein crystal mounting material to reduce background scatter. Journal of Applied Crystallography, 46:1–7, 2013.

Educational Accomplishment: Jennifer (Jeney) Wierman, a rising star in biophysics at Cornell University and a member of the research group of Sol M. Gruner, was recently awarded the Margaret C. Etter Student Lecturer Award in the Synchrotron Radiation Scientific Group by the American Crystallographic Association. As a graduate student Jeney has worked at CHESS since 2011, the majority of her research has focused on improving data collection of x-ray scattering for protein crystallography measurements. In 2012 she began working with graphene, which are thin sheets of one atom thick layers of carbon. As a single layer a carbonatoms, graphene is too thin to significantly scatter, yet it is still relatively strong. Jeney's work demonstrates that it is feasible and practical to handle graphene, and that graphene can be used to replace the standard specimen holders to achieve vanishingly small background scattering. Jeney’s work also demonstrated that wrapping a protein crystal in graphene prevents specimens from dehydration. Her work points out that graphene could have applications in many areas of science where there is need to hold and handle specimens without overwhelming the measurements by the presence of a substrate, such as scattering from weakly diffracting liquids and disordered materials to providing flat backgrounds for objects studied by coherent x-ray diffraction imaging.