Materials Possessing Reduced Coefficient of Thermal Expansion

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

Prof. Jon J. Kellar, Chair
Department of Materials and Metallurgical Engineering
South Dakota School of Mines and Technology
Rapid City, SD 57701-3995

Abstract

There are many industrial applications where dimensionally stable materials arerequired.  Applications include aerospace, catalysis/combustion, optics andelectronics.  Candidate materials for fabrication of dimensionally stable materialsare reviewed and a composite system is studied in detail.  Toward this end, themodel system studied consisted of a lightweight polymer matrix and ceramicparticulate filler.  The polymer used for this study was a cyanate ester resin. Thefiller utilized was zirconium tungstate (ZrW2O8) prepared by two differentsyntheses (sol-gel and inverse-micelle).  The latter synthesis resulted inparticulate filler largely in the form of rectangular rods that were ~3-4 microns longand had a thickness of 0.3 microns.  Next, composite samples were prepared, andthe coefficient of thermal expansion property measured.  It was found that thecomposite CTE was 70% less than the neat polymer.  Compounding methods willbe reported as well as the measured data showing the effects of size and shape inrelation to the coefficient of thermal expansion.  The goal of this research is todevelop a lightweight polymer matrix composite exhibiting near zero expansionbetween -100 and 100 °C.


Spinal Cord Regeneration – A Materials Approach

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

Dr. Ryan Gilbert
Department of Biomedical Engineering
Michigan Technological University

Abstract

Following spinal cord injury, neural and glial cells are destroyed.  Those neuronsthat survive the initial trauma must then survive a secondary injury cascade thatarises from inflammation.  Following initial and secondary injury, regeneratingaxons attempt to grow into and through a glial scar environment.  However, theyare typically unable to navigate through a dense matrix filled with cells andinhibitory molecules.  As a result, individuals with spinal cord injury suffer paralysiscaudal to the injury site.  Traditional approaches to heal the injured spinal cordhave focused on application of drug systemically.  However, because of thecompromised state of the vascular system within the injured spinal cord, morelocalized delivery techniques must be pursued.  This talk will highlight our effortsto construct drug releasing natural hydrogels and polymeric guidance channels.Natural hydrogels loaded with therapeutic can be injected near the injury with thegoal of releasing therapeutic locally. Glutathione and interleukin-10 were loadedinto our agarose/methylcellulose hydrogel system, their release rate characterized,bioactivity assessed within an in vitro model, and functional recovery assessedwithin an in vivo model.  Aligned fiber species have the potential to direct axonaloutgrowth.  Thus, polymer guidance structures were created.  Axonal outgrowthon the conduit structure was assessed within an in vitro model, and the ability ofthe structure to guide neurons after spinal cord injury was assessed within an invivo model.  These results suggest that materials can improve regenerationoutcomes and that translational analogs could be used to effectively treat humanspinal cord injury.

Biography

Dr. Ryan Gilbert earned his B.S.E. from the University of Michigan in Chemical Engineering.  Afterworking for Aastrom Biosciences and Holcim, Dr. Gilbert earned his Ph.D. in Biomedical Engineering from CaseWestern Reserve University.  Dr. Gilbert established the Regeneration and Repair Laboratory at MichiganTechnological University, and the laboratory’s main research focus is in the development of biomaterials for spinalcord regeneration.


Drelich Reappointed

Associate Professor Jarek Drelich has been reappointed as member of the Editorial Board of the Journal of Adhesion Science and Technology. Drelich has been a board member since 1999.

The international journal provides a forum for “theoretical and basic aspects of adhesion science and its applications in all areas of technology”. It is published by Brill, one of the oldest scholarly publishers in the world.


Modeling and Simulation of Microstructure Evolution in Crystalline Solids

Friday, November 14, 2008 3:00 – 4:00 pm
Room 610, M&M Building

Dr. Yongmei M. Jin
Department of Aerospace Engineering, Texas A&M University
3141 TAMU College Station, TX 77843-3141

Abstract

This talk will present materials modeling and computer simulation studies ofmicrostructure evolutions in response to external thermal, mechanical andmagnetic stimuli during processing and service in various crystalline solids, with aspecial focus on structural and functional metal alloys. The theoreticalmethodology (phase field model) is based on gradient thermodynamics ofheterogeneous materials, microstructure-dependent free energies ofmicroelasticity and micromagnetism, and semi-phenomenological kinetics ofmicrostructure evolution. Particular examples will be discussed: (1) developmentof compositional and structural domains during decomposition, ordering transition,and martensitic transformation; (2) effects of crystallographic microstructures onmagnetic and mechanical properties in advanced magnetic materials includinghard ferromagnets, magnetostrictive materials, and magnetic shape memoryalloys; and (3) roles of long-range dipole-dipole interactions and evolution kineticpathways in domain microstructure processes and material properties.Connections between mesoscale phase field modeling, atomistic (first principles,molecular dynamics) and continuum (finite element) simulations, thermodynamicand kinetic databases, as well as experiments will also be addressed.

Biography

Dr. Jin received B.E. and M.E. in Mechanical Engineering from University of Science and Technology of China in 1994 and 1997, respectively, and Ph.D. in Materials Science and Engineering from Rutgers University in2003. After two years of postdoctoral research at Rutgers University, she joined the Department of AerospaceEngineering at Texas A&M University in 2005 as an Assistant Professor. Her research interest focuses on materialsmodeling and computer simulation. In particular, she has been working on the development and application ofphase field models to investigate microstructure evolutions in crystalline materials during various physicalprocesses, e.g., martensitic transformation, decomposition, ordering transition, ferromagnetic domain switching,magnetomechanical behaviors, and defect evolutions (dislocations, cracks, voids, and free surfaces) in single- andpoly-crystalline bulk and thin film materials.


Photoinitiated Controlled Nitric Oxide Release Materials for Implanted Biomedical Devices

Friday, October 31, 2008 3:00 – 4:00 pm
Room 610, M&M Building

Dr. Megan C. Frost
Department of Biomedical Engineering
Michigan technological University

Abstract

The research in our laboratory is focused on the development of novel Snitrosothiol compounds (RSNOs) as nitric oxide (NO) donors that can use light ofdifferent wavelengths and intensities to trigger the release of NO. Preliminary datawill be presented for novel aromatic RSNOs that release NO in response to phototriggers. By altering the electronic properties of substituents on the aromatic ring,we are able to shift the specific wavelength of light needed to release NO. Work isunderway focused on developing the chemistries necessary to immobilize thesecompounds into polymeric materials so that they can be used in the fabrication ofimplantable biomedical devices such as fiber optic sensors and probes capable ofreleasing NO at continuously variable and controllable levels such that the devicesshow improved biocompatibility and enhanced performance.

Biography

Megan C. Frost joined the faculty of the Department of Biomedical Engineering asan assistant professor in August 2007. She comes to Michigan Tech from a postdoctoralposition at the University of Michigan. She holds a PhD in Analytical Chemistry from theUniversity of Michigan, an MS is Analytical Chemistry from Purdue University-Indianapolis and aBS in Biological Sciences from the University of Notre Dame. Her research interests involvedesigning nitric oxide releasing polymeric materials that exhibit reduced biological responsewhen implanted in the body and the development of intravascular and subcutaneous sensorswith these nitric oxide releasing materials that show improved in vivo performance.


Influence of the Starting Substrate Morphology on the Growth of Epitaxial (001)CeO2 Thin Films on r-Plane Al2O3 Substrates

Friday, October 24, 2008 3:30 – 3:55 pm
Room 610, M&M Building

Madhana Sunder
Graduate Student
Department of Materials Science and Engineering
Michigan Technological University
Houghton

Abstract

Epitaxial (001)-oriented cerium dioxide (CeO2) thin film is an essential buffer layer forsubsequent integration of functional single-crystal cubic perovskite films on the commerciallyavailable large area r-plane sapphire (Al2O3) substrates. We report on how modifying the startingsubstrate morphology can lead to growth of epitaxial (001)CeO2 films on r-plane Al2O3substrates. Films grown on as received substrates were primarily of mixed (001) and (111)orientations. In general, low film growth rates and higher substrate temperatures, lead to ahigher volume fraction of (001)CeO2. The highest volume fraction of (001)CeO2 achieved in thecase of films grown on as received substrates, using the highest growth temperature andslowest growth rate of 830°C and 0.05nm/min respectively, was 81%. However when thesubstrates were annealed prior to film deposition, 100% (001)CeO2 films was obtained. Theemergence of a regularly spaced atomic step terrace features on the annealed wafer surface isbelieved to be key in enabling growth of epitaxial (001)CeO2 films. Crystallographic relationshipsbetween the atomic step edges and (001)CeO2 unit cells were derived, to understand the role ofpre-growth substrate annealing in promoting nucleation of (001)CeO2 on r-plane Al2O3substrates. (001)CeO2 films with atomic terraces and improved crystallinity were grown on pregrowth annealed r-plane Al2O3 substrates.


Impact of Growth Surface on the Crystal Structure of PMN-30PT Thin Films

Friday, October 24, 2008 3:05 – 3:30 pm
Room 610, M&M Building

Lakshmi Krishna
Graduate Student
Department of Materials Science and Engineering
Michigan Technological University
Houghton

Abstract

The impact of the crystal structure on the dielectric properties of the PMN-30%PTthin films has not been investigated. This is due in part to a lack of knowledge onhow to promote one crystal structure by modifying the growth conditions. Bygrowing at low temperature (250ºC) and subsequently rapid thermal annealing at850 ºC, we have observed that PMN-30%PT thin films results in a single crystalperovskite phase. In contrast, a high temperature (900ºC) deposition ofPMN-30%PT on CeO2 buffered sapphire (Al2O3) results in a single crystalpyrochlore phase. X-ray diffraction scans were performed to investigate the phaseand degree of crystallinity of the PMN-PT thin films. These films will allow aninvestigation of how crystal structure impacts the dielectric properties of the singlecrystal PMN-PT thin films.


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.