Simulated Experiments of Particle and Plasma-Surface Interactions at the Nanoscale.

Professor Jean Paul Allain, Purdue University, School of Nuclear Engineering, School of Materials Engineering, Birck Nanotechnology Center

Date: Nov. 23, 2009
Time: 3:30pm (refreshments start at 3:00pm)
Place: 24-115

ABSTRACT:

The modification of heterogeneous surfaces during particle and plasma irradiation requires an understanding of elemental, chemical and structural evolution at the nanoscale. This is particularly important for systems exposed to high-intensity low-energy irradiation such as plasma-facing components in fusion energy experimental nuclear reactors and plasma-facing mirrors used in nanolithography. In extreme UV lithography sources, for example, hyperthermal (10-1000 eV) Sn ions are an ultra-shallow implant in Ru thin-film mirrors penetrating a few nanometers and subsequently diffusing to sublayers below the air/film interface. The implanted species directly affect the EUV optical reflective properties of the mirror at wavelengths that approach the implantation zone. This is particularly important in advanced microlithography applications.

Prof. Allain’s group designed and built the IMPACT (Interaction of Materials with Particles and Components Testing) experimental facility designed to study in-situ nanoscale characterization of particle-induced growth and synthesis of surface or low-dimensional state systems tailored during energetic or thermal particle exposure at relevant modification time scales. Surface-sensitive techniques include: low-energy ion scattering spectroscopy (LEISS), direct recoil spectroscopy (to study hydrogen levels in nanostructures), X-ray photoelectron spectroscopy (XPS) and in-situ sputtering erosion monitoring. This talk will focus on the limits and challenges that face in-situ characterization studies of thin-film or low-dimensional state systems during irradiation. The talk will also highlight a new experimental facility being built at Purdue known as PRIHSM (Particle and Radiation Interaction with Soft and Hard Matter). The new PRIHSM facility in addition to techniques above includes: ARPES (angular-resolved photoelectron spectroscopy) materials characterization during energetic particle (ion-beam) and gas interaction with candidate materials. LEISS measures elemental mapping of surface structure, UPS measures valence shell dynamics and ARPES maps the energy-momentum electronic band structure. PRIHSM at Purdue will provide a unique opportunity to directly link structure, chemical state and electronic configuration with irradiation-driven surfaces near sub-threshold ion-induced desorption regimes. In particular, irradiation directed synthesis for nanostructure templating, manipulation, and tailoring.

BIOGRAPHY

Prof. Jean Paul Allain completed his Ph.D. in the Department of Nuclear, Plasma and Radiological Engineering at the University of Illinois, Urbana-Champaign. He received an M.S. in Nuclear Engineering from the same institution. Prof. Allain joined Argonne National Laboratory as a staff scientist in 2003 and joined the faculty in the School of Nuclear Engineering at Purdue University in Fall of 2007 with a courtesy appointment with the School of Materials Engineering. Prof. Allain is an affiliate faculty of the Birck Nanotechnology Center. Prof. Allain is the author of over 50 papers in both experimental and computational modeling work in the area of particle-surface interactions in nuclear magnetic fusion science. His studies include developing in-situ surface structure and composition evolution characterization of heterogeneous surfaces under low-energy irradiation promoting structure and function at the nanoscale. Prof. Allain is also working in coupling post-ionization secondary mass neutral spectrometry techniques with in-situ surface characterization to design ultra-thin active films coupled to directed radiation synthesis with applications in semiconductor, biomaterials and nuclear energy technology areas.

Ultra High Strength Nanofilamentary Wires: Study of plasticity mechanisms by in-situ techniques

Dr. Ludovic Thilly, PHYMAT Laboratory, University of Poitiers, France

Monday, Nov. 23rd
12:00 pm – 1:00 pm
Von Hippel Room, 13-2137

High-conductivity and simultaneously high-strength materials are needed for the creation of winding wires for large high-field magnetic systems. Severe plastic deformation is used to prepare Copper-based high strength nanocomposites with a large number of continuous parallel Niobium filaments whose diameters are few tens of nanometers.

The resulting nanocomposite has an ultimate tensile strength of 2 GPa at 77K. In-situ tests are performed under synchrotron radiation on the nanocomposite wires containing Nb nanofilaments to study the evolution of elastic strains and peak profiles versus the applied stress. The elasto-plastic transition is also studied in the different phases with respect to microstructure size. Finally, a new criterion for the determination of the macro-yield stress is developed to determine the transition from elasto-microplastic to macroplastic regimes.

Lunch and refreshments will be served before the talk. Please join us!

Nanoarchitectures: Why more of less is more—especially for energy storage and conversion

Dr. Debra Rolison, Surface Chemistry Branch, Naval Research Laboratory

Thursday, Nov. 19
3:00 pm
Room 66-110

When multifunctionality and molecular transport paths are critical, as they are in rate-critical applications such as catalysis, energy storage and conversion, sensing, and fabrication, the challenge is to move beyond the creation of a functional nanoscale object or feature. High performance, large-scale construction, and bridging to the macroscale requires architectural design. Sol-gel-derived ultraporous, aperiodic aerogel-like nanofoams unite high surface area for heterogeneous reactions, including post-synthesis modifications, with a continuous, porous network for rapid flux of molecular and nanoscopic reactants. The “walls” are defined by the nanoscopic, covalently bonded, one-dimensional solid network of the gel–and because the walls are erected by sol-gel chemistry, the architecture is readily scaled from nanometer to meter length scales. The vast open, interconnected space characteristic of a building is represented by the interpenetrating nanoscopic pore network (3-D plumbing). An architectural viewpoint provides a powerful metaphor to guide the chemist and materials scientist in the design of aperiodic nanoarchitectures and in their physicochemical transformation into multifunctional objects that express high performance.

Please join us!

Nanocatalyst Engineering: From Well-Defined to Nanoscale Surfaces

Vojislav Stamenkovic

Argonne National Laboratory

Materials Science Division

Argonne, IL USA

Tuesday, November 10, 2009

2:00-3:00pm

Room 31-161

Ability to /tune the electronic and structural properties of nanocatalysts/ can potentially lead towards the superior catalytic enhancement that was reported for the Pt_3 Ni(111)-skin surface [1].

Fine tuning of the surface properties is usually done on extended well-defined surfaces in ultra-high vacuum. A number of surface sensitive tools could be utilized such as AES, LEIS and UPS before controlled transfer into real reaction environment. The single and polycrystalline crystalline well-defined surfaces have been used to benchmark the activity range that could be expected on Pt based electrodes. The knowledge accumulated from well-defined systems is further used to engineer nanoscale surfaces with designated composition and morphology.

It has been proposed that surface modifications induced by the second/third metal, and consequent catalytic enhancements could occur through the following effects: (1) /Electronic effect/, due to changes in the metallic d-band center position vs. Fermi level; and (2) /Structural effect/, which reflects relationship between atomic geometry, and/or surface chemistry, i.e., dissolution – surface roughening. In principle, different near-surface composition profiles have been found to have different electronic structures. Modification in Pt electronic properties alters adsorption/catalytic properties of corresponding materials. The most active systems for the electrochemical oxygen reduction reaction (ORR) are established to be the Pt‑skin near‑surface formation.

The similar levels of catalytic enhancement have been established for corresponding nanoscale materials. In addition to electronic properties we have found how catalytic activity could be affected by the arrangement of surface defects on nanoscale surfaces. Ability to control surface and near surface catalyst properties enables fine tuning of catalytic activity and stability of nanoscale surfaces.

[1] V. Stamenkovic, B. Fowler, B.S. Mun, G. Wang, P.N. Ross, C.A. Lucas, N.M. Markovic, /Science/ 315 (2007) 493-497.

[2] V. Stamenkovic, B.S. Mun, K.J.J. Mayrhofer, P.N. Ross, N.M. Markovic, J. Rossmeisl, J. Greeley, J.K. Nørskov, /Angewandte Chemie International Edition/ 45 (2006) 2897.

[3] V. Stamenkovic, B.S. Mun, M. Arenz, K.J.J. Mayrhofer, C. A. Lucas, G. Wang, P.N. Ross, N.M. Markovic, /Nature Materials/ 6 (2007) 241.

Nature Inspired Materials Science

Prof. Michael Rubner

Nov. 17, 4:00, 10-250

Reception to follow in the Bush Room, 10-105

Materials Scientists more and more are looking to nature for clues on how to create highly functional materials with exceptional properties. The fog harvesting capabilities of the Namib Desert beetle, the beautiful iridescent colors of the hummingbird, and the super water repellant abilities of the Lotus leaf are but a few examples of the amazing properties developed over many years in the natural world.  Nature also makes extensive use of the pH-dependent behavior of weak functional groups such as carboxylic acid and amine functional groups.  The pH-gated opening and closing of the carboxylate-lined cages of the cowpea chlorotic mottle virus, for example, is an important element of the infection process.  This presentation will explore synthetic mimics to the nano- and microstructures responsible for these fascinating properties.  For example, we have demonstrated a pH-induced porosity transition that can be used to create porous films with pore sizes that are tunable from the nanometer scale to the multiple micron scale.  The pores of these films, either nano- or micropores, can be reversibly opened and closed by changes in solution pH.  The ability to engineer pH-gated porosity transitions in heterostructure thin films has led to the demonstration of broadband anti-reflection coatings that mimic the anti-reflection properties of the moth eye and pH-tunable Bragg reflectors with a structure and function similar to that found in hummingbird wings.  In addition, the highly textured honeycomb-like surfaces created by the formation of micron-scale pores are ideally suited for the creation of superhydrophobic surfaces that mimic the behavior of the self-cleaning lotus leaf.  Techniques to create patterned superhydrophobic/superhydrophilic surfaces have also been developed that make it possible to create planar open microfluidic channels as well as fog-harvesting coatings that mimic the behavior of the Namib Desert beetle.

The Wulff Lecture is an introductory, general-audience, entertaining lecture which serves to educate, inspire, and encourage MIT undergraduates to take up study in the field of materials science and engineering and related fields. The entire MIT community is invited to attend. The Wulff Lecture honors the late Professor John Wulff, a skilled, provocative, and entertaining teacher who inaugurated a new approach to teaching the popular freshman subject: 3.091 Introduction to Solid State Chemistry.