High Resolution 2D and Tomographic X-Ray Microscopy in the SEM

Wednesday, October 22, 2008 2:00 – 3:00 pm
Room 610, M&M Building

Dr. Paul Mainwaring
Gatan Inc.
5794 West Las Positas Blvd.
Pleasanton, CA 9458

Abstract

The great advantage of X-ray microscopy is the ability to image the internal structure ofspecimens compared to the surface information obtained by SEM imaging. The two techniquescombine to deliver the maximum amount of structural information of the specimen. A SEMhosted X-ray ultra microscope consists of a metallic target material mounted on a high precisionsoftware-controlled positioning arm which is placed beneath the electron beam to produce apoint source of X-rays, a sample holder and a CCD camera for signal detection. Thesecomponents are fully compatible with the SEM working environment and allow switchingbetween SEM and X-ray imaging modes. The X-ray energy used can be “tuned” to increasevisibility of certain low contrast specimens. In general, spatial resolution of 200 – 400 nm can beachieved for 2D imaging.

X-ray microscopy allows the sample to be always in focus and the depth of focus enables stereo imaging and 3D micro-tomography to be carried out. Image contrast from the specimen is the result of both X-ray absorption and phase contrast mechanisms. Phase contrast arises from refraction and diffraction rather than absorption, and patented algorithms have been developed to extract this information. Variations in refractive index can occur in samples that present little variation in density and show little absorption contrast in the image. This allows fine detail,especially in low density materials which would be otherwise invisible, to be imaged using the phase contrast component of the total transmitted signal.

Recent improvements include custom built cameras for X-ray detection, robust phase contrast extraction algorithms, fast tomographic acquisition and very fast 3D reconstruction.Examples of the use of the X-ray microscope to image polymers, metal and graphite foams andbiological materials will be given.

Biography

Dr. Mainwaring received a Ph.D degree in geochemistry from the University of Toronto, Canada. In hisearly career, he joined the Canadian federal government Labs in the Department of Energy and built up a modernelectron beam and X-ray diffraction laboratory with SEMs, electron microprobe instruments and image analysissystems for materials characterization. Since 1995 he has been involved in the development of electronbackscattered diffraction systems with Oxford Instruments and EDAX/TSL. Dr. Mainwaring is now at Gatan Inc. asProduct Manager for Cathodoluminescence and X-ray Microscopy, both growing fields in the biological andmaterials research areas.


Inhibitory Effects of Copper-Vermiculite Against E. coli

Friday, October 10, 2008 3:00 – 3:30 pm
Room 610, M&M Building

Bowen Li
Graduate Student
Department of Materials Science and Engineering
Michigan Technological University

Abstract

Copper vermiculite (Cu-V) is new type of synthetic antimicrobial agent havingpotential as a functional additive in products such as plastics, paints, leathers, andwoods to reduce microbial persistence and biofilm formation. The Cu-V wasprepared by cation exchange reaction, and characterized by SEM and XRD; theCu atoms were homogeneously dispersed in the vermiculite structure. Theantibacterial efficiency of Cu-V was evaluated by determining its minimuminhibitory concentration (MIC) against Escherichia coli. In the control vermiculitesuspensions, E. coli densities remained constant during the 12 hour contact time;in contrast, bacteria levels with Cu-V significantly decreased. In the experimentwith 200 ppm Cu-V (5.10 ppm Cu), viable E. coli levels were reduced by 94.8% at1 hour, 99.6% at 2 hours, and >99.9% at 4 hours. The Cu-V MIC level against E.coli was10 ppm, while the untreated vermiculite had no antibacterial activity. Verylittle Cu was detected in the suspensions during the study, indicating that the CuV’s antimicrobial effect was due to surface interactions.


Bonding, Structure, Defects and Diffusion in ‘Tough’ IronBased Bulk Amorphous Alloy

Friday, September 26, 2008 3:00 – 4:00 pm
Room 610, M&M Building

Prof. Gary J. Shiflet
Department of Materials Science and Engineering, University of Virginia

Abstract

Can brittle bulk metallic glasses be further designed to exhibit fracture toughness?And, can this be done without loss of other superior properties, such as, strength(currently 4 GPa)? Yes to both questions. Bulk amorphous metals are quitecommon today and nearly every major metal alloy system can be synthesized intoa bulk glassy material (Fe-, Cu-, Ni- Ti-, Zr-, Mg-based, etc., but not Al). To beuseful, the task now is to make them damage tolerant. This talk will emphasize ourstrategy for increasing alloy plasticity through bonding studies and current effortsto understand defects and structure in amorphous iron-metalloid alloys.  Thedesign of amorphous steel with high glass formability has provided the base alloycomposition used to further improve overall plastic behavior by reducing its highshear modulus. Our systematic investigation highlights the role of interatomicinteractions, in addition to the individual alloying elements, in determining theelastic moduli or Poisson’s ratio, and hence the ductility. For instance, as asolution to alloy brittleness for amorphous steel, ab initio quantum chemistrymethods and EELS indicate that phosphorous improves plasticity because of theunusual bonding associated with electron transfer from phosphorous to iron.Extensions to other alloy systems will also be discussed to test this fundamental approach.

Biography

Dr. Shiflet is currently the WG Reynolds Professor at the University of Virginia where he has been afaculty member in the School of Engineering since 1980. He has a BS and MS in physics and PhD in metallurgicalengineering (1981), all from MTU. Shiflet’s primary interests are in solid-state phase transformations of metal alloysand concerns thermodynamics, nucleation and the kinetics associated with growth of new phases. He haspublished more than 250 papers and holds several patents concerning various amorphous metal alloys. Dr. Shiflethas been awarded two creativity awards from the National Science Foundation, the ASM Research Award (SilverMetal) and has been elected as a Fellow of the American Society for Materials and Japan Advancement of Scienceand was selected as Scientific American 50 for 2004. He is a member of The Metallurgical Society of AIME and theAmerican Society for Materials.


Technical Feasibility Assessment of Bio-absorbable Metal Stent

Tuesday, September 23, 2008 1:00 – 2:00 pm
Room U113, M&M Building

Jon Stinson
Boston Scientific
Interventional Cardiology Division
Maple Grove, MN 55311

Abstract

Boston Scientific Interventional Cardiology Division is exploring the feasibility ofbiodegradable metal stents. In particular, iron is of interest based on reportedbiocompatibility and degradation rate. Boston Scientific is performing IR&Dexperimentation to generate data upon which a recommendation can be made tothe investment board regarding the technical viability of this stent concept. One ofthe challenges discovered was that in-vitro degradation rates of the candidatemetals do not agree with observations from in-vivo experiments. One of the keydesign criteria for a degradable stent is the degradation behavior. In order to beable to assess the feasibility of these stent materials, it is necessary to understandthe time rate of mass and strength loss.

Biography

Jon Stinson is a manager at R&D Materials Analytical Lab, Boston ScientificInterventional Cardiology Division. He received a B.S. degree in Metallurgical Engineering atMTU in 1982 and MBA Management degree at the University of St. Thomas in 1992.  Jon firstworked for 12 years in aerospace and defense (Williams International, Howmet, Honeywell,Alliant Techsystems) as a metallurgical engineer on R&D projects for gas turbine engines andordnance. Then he worked for 14 years in the medical device industry as a metallurgicalengineer and materials lab manager on R&D projects for intraluminal catheter, guidewire, andimplant products.


Enhancement of Magneto-Optical Effects in Gyrotropic Photonic Bandgap Materials

Friday, September 19, 2008 3:00 – 4:00 pm
Room 610, M&M Building

Dr. Amir A. Jalali
Department of Physics
Michigan Technological University

Abstract

Magneto-optic materials have many applications in a large variety of areas of integrated optics. Perhapsthe most common application of magneto-optic materials is in the construction of nonreciprocalwaveguides and magneto-optic isolators although there are also many applications in other areas ofintegrated optics such as magneto-optical fast switching, magneto-optical read-out disks, and magnetooptical sensors and visualizers. All of these applications are based on the magneto-optical activity of thematerial like polarization rotation of the light passing through the medium (Faraday rotation) andmagneto-optical tunability of the medium. Magneto-optical effects can be enhanced significantly in aperiodic structure, the so called photonic crystals, that exhibit photonic bandgaps. The enhancement ofmagneto-optical effects would thus allow large improvements in existing applications and even moreopen up new possibilities for advanced sensor devices and optical filters.

In this talk I will present a study of polarization rotation enhancement in one- and two-dimensionalphotonic crystals and provide theoretical and experimental support for a novel type of photonic bandgapin birefringent magnetooptic photonic crystal waveguides. Contradirectional coupling of fundamental tohigher order local normal modes in birefringent magnetooptic photonic crystal waveguides leads topartially overlapping gyrotropic bandgaps inside the Brillouin zone. The overlapping of gyrotropicbandgaps results in selective suppression of Bloch mode propagation. This type of photonic bandgapand degeneracy breaking inside the Brillouin zone are a result of the local coupling between differentelliptically polarized photonic states in magneto-photonic crystals. Large magnetically active changes inBloch mode polarization near the band edges are observed. These changes are not due to photontrapping as conventionally explained in other types of magnetooptic periodic systems.

The ability of magneto-optic photonic crystal waveguides to provide large polarization rotation and tightoptical confinement can also be exploited to produce highly sensitive biochemical sensors. Our studyshows that the polarization rotation at the edge of gyrotropic degenerate bandgaps is highly sensitive tosmall refractive index changes in the waveguide cover of the device.

Biography

Dr. Jalali received the PhD degree in Physics from the Royal Institute of Technology (KTH), Stockholm, Sweden, inNov. 2004. He spent two years as a Postdoctoral researcher at the Michigan Technological University, Michigan, USA. Since2007, He has been a Research Scientist at Michigan Technological University. His research interests are magnetooptic photoniccrystals, ferromagnetic resonance, waveguide technology and photonic biosensors.


Processing and Properties of Amorphous Reinforced Crystalline Matrix Composites in Ni-W Alloy System

Friday, September 5, 2008 3:00 – 4:00 pm
Room 610, M&M Building

Alex O. Aning
Virginia Polytechnic Institute & State University
Department of Materials Science & Engineering
Blacksburg, Virginia 24061

Abstract

Metal Matrix Composites (MMCs) are used as structural materials because of their ability tohave a combination of high strength and good ductility.  A common problem with MMCs utilizingvastly different materials is the difficulty in forming a strong matrix/reinforcement interfacewithout suffering extensive dissolution, debonding, or chemical reactions between thecomponents.  By using a reinforcement which has a similar chemistry and local atomic structureto that of the matrix, these critical problems can be reduced.  In this work, a nickel baseamorphous particulate reinforced crystalline nickel matrix composites were processed.  Thereinforcement, an equimolar NiW amorphous powder, was synthesized in a SPEX mill by themechanical alloying process.  The amorphous and crystalline nickel powders were blended inan Attritor mill in varying volume fractions and then consolidated using: hot-isostatic pressing(HIP), or combustion driven compaction (CDC) process.  This work revealed that the amorphousNiW reinforcement provided strength and hardness to the ductile Ni matrix while simultaneouslymaintaining a strong interfacial bond due to the similar chemistry of the two components.  Thestrengthening achieved in the composite is attributed to particulate/matrix boundary strengthening.

Biography

Dr. Alex O. Aning is an Associate Professor of Materials Science and Engineeringat Virginia Tech.  He obtained the BS degree in Physics from Morgan State University,Baltimore in 1977, and Ph.D. in Metallurgical Engineering from University of Missouri- Rolla in1982.  After a year of post-doctoral studies at Rolla he joined the Physics Department at MorganState in 1983.  At Morgan State he helped develop a new engineering school.  He later becamethe head the Electrical Engineering Department and lead it to become ABET accredited on thefirst attempt.  He joined Virginia Tech in 1992; from 1998 to 2005, he was part of theEngineering Education Department.  He has held visiting professorships at the Johns HopkinsUniversity (1992) and the University of Virginia (1989/90).  He does research in the areas ofphase transformations, and synthesis and processing of metallic, ceramic and compositematerials.  His current activities include solid-state formation of bulk amorphous alloys, andamorphous phase-strengthened metal matrix composites.  He is a member of TMS and ASMInternational.


New Funding

Peter Moran received $65,000 from the University of Michigan (MIIE program) for “IME: A Proposal to the MIIE Industry and Economic Engagement Fund for Forming a Partnership Between Tellurex, Corp. and Michigan Tech to Engineer Materials for High-Efficiency Thermoelectric Power Generators.” MIIE is Michigan Initiative for Innovation and Entrepreneurship.


New Funding

Associate Professor Peter Moran (MSE) received $76,000 from the U.S. Department of Defense Office of Naval Research for “Developing Highly Magnetoelectric Fe(1-x)Gax/PMN-PT Heterostructures for Integration onto SiC.”