Tag: John & Virginia Towers Lecture Series

Oxidation Behavior of Ultra-High Temperature Ceramics at 1500C and 1600C

Monday, March 2, 2009 4:00 – 5:00 pm
Room 610, M&M Building

Dr. Kathleen Sevener
Assistant Professor
Mechanical Engineering Department
Valparaiso University, Valparaiso, IN

Abstract

With the continuing interest in hypersonic flight, much work is focused on developing andcharacterizing ultra-high temperature ceramics (UHTCs) for leading edge applications andincorporating UHTCs into composites for hot structures. There is a lack of understanding of thetrue aerothermal effects on UHTC materials, which is required for optimization of UHTCcomposition.  While means to explore such effects are in progress within the aerospacecommunity, parallel efforts to develop UHTC compositions with improved properties areunderway.  This presentation will focus on work performed at AFRL to evaluate several HfB2-SiCUHTC compositions via isothermal anneals. Initial studies focused on the effect of compositionvariation. To establish a baseline on the materials, samples were subjected to furnace oxidationat 1500°C and 1600°C and the oxidation behavior was characterized via weight change,scanning electron microscopy, and energy dispersive spectroscopy. The baseline data werecompared to published data for similar compositions. Follow-on studies focused on the effect ofprocessing parameters for HfB2-20vol% SiC, the most promising candidate from the initialstudies. Milling time and consolidation method were varied to determine if the resultingmicrostructural changes would influence oxidation behavior. Results of these studies will bepresented and analyzed in the context of oxidation models under development at AFRL, andwith consideration to future applications of UHTCs on hypersonic vehicles.

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Environmental Brake Engineering: Materials Countermeasures

Friday, February 27, 2009 3:00 – 4:00 pm
Room 610, M&M Building

Paul Sanders
Chassis Materials Technical Leader
Ford Research and Advanced Engineering
Ford Motor Company

Abstract

Failure mode avoidance is a product development strategy at Ford Motor Company todeliver improved vehicle performance. The root cause of customer perceived failuremodes such as brake wear, dust, and vibration are analyzed and individual materialscountermeasures are discussed. The high-level environmental impact of theseindependent countermeasures is noted.After this “component-level” approach, a system-level solution will be presented thataddresses the same failure modes. This system approach will require rotor substrateand wear-layer materials development. Through a detailed understanding of the systemperformance, the materials requirements can be clearly defined. In the case of the rotorsubstrate, the material must have > 10 MPa yield strength and < 10-5/s creep rate at ≈500°C. The low stress and time at temperature (< 1 hr lifetime) may enable the design ofa high-temperature aluminum alloy for the rotor structure. The friction wear layer musthave similar tribological behavior to the baseline cast iron in addition to matching thermalexpansion and galvanic potential of the aluminum substrate. General corrosionresistance will significantly reduce rotor and lining wear. This materials-system solutionwill facilitate a lightweight, “lifetime” brake rotor that reduces use-phase environmentalimpact.

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Surfaces and Interfaces in Nanoscale Electronic Materials: From Understanding to Engineering

Monday, February 23, 2009 4:00 – 5:00 pm
Room 610, M&M Building

Pengpeng Zhang
Department of Chemistry and Physics
The Pennsylvania State University

Abstract

Surfaces and interfaces play a critical role in determining properties andfunctions of nanomaterials, in many cases simply dominating bulk properties,owing to the large surface- and interface-to-volume ratio. One can further engineerand improve the performance of nanoscale devices through the control of surfaceand interface chemistry.  Using Si nanomembranes as a model system, we haveinvestigated how surfaces and interfaces influence electrical transport propertiesat the nanoscale by means of scanning tunneling microscopy (STM) and fourprobe measurements. We show that electronic conduction in Si nanomembranesis not determined by bulk dopants but by the interplay of surface and interfaceelectronic structures with the “bulk” band structure of the thin Si membrane, whichcan be thought of as “surface transfer doping.” Additionally, we characterize selfassembled alkanethiolate monolayers (SAMs) on Au{111} with embedded staticdipole groups in the adsorbate molecules using Kelvin probe force microscopy(KPFM), X-ray photoelectron spectroscopy (XPS) and quantitative infraredvibrational spectroscopy (IR) techniques. We have modulated the metal workfunction by adjusting the orientation of the embedded dipole and the geometricstructures of the SAMs, which will facilitate applications in charge injection inorganic electronic devices. Recently, we have also studied divergent dipoles andintermolecular interactions in geometrically identical adsorbates, finding thatdiffering orientations of molecular dipole moments influence SAM properties,including the stability of the monolayers in competitive binding and exchangeenvironments. These studies demonstrate that a thorough physical understandingof emerging phenomena at the nano- or molecular scale can advancetechnologies in nanoelectronics and molecular electronics.

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Multiscale Modeling of Polymer Material Systems

Friday, January 23, 2009
3:00 – 4:00 pm
Room 610, M&M Building

Gregory M. Odegard
Department of Mechanical Engineering – Engineering Mechanics
Michigan Technological University

Abstract

Polymer-based composite and nanocomposite materials have the potential toprovide significant increases in specific stiffness and specific strength relative tocurrent materials used for many engineering structural applications. To facilitatethe design and development of polymer nanocomposite materials, structureproperty relationships must be established that predict the bulk mechanicalresponse of these materials as a function of the molecular- and micro-structure.The objective of this research is to establish an accurate and efficient approachfor using computational modeling to develop structure-property relationships forpolymer-based systems.  A combination of molecular dynamics and finite elementmethods has been used to predict the mechanical response of high-performancepolymers, nanoparticle/polymer composites, SWNT/polymer composites, andSWNT arrays.  An overview of this research will be presented along with theresults from specific material systems.

Biography

Greg earned his Ph.D. at the University of Denver in 2000, where he studied thefailure behavior of graphite/polyimide composites.  From 2000-2004 he worked at NASALangley Research Center where he conducted research on the multiscale modeling andcharacterization of polymer-based nanostructured materials.  Since 2004, Gregory has servedas an Assistant Professor at Michigan Technological University where he conducts researchon a wide range of engineering materials and biological tissue.  Greg has earned the SAMPEOutstanding Graduate Student award, ASME/Boeing Structures and Materials Award, HenryJ.E. Reid Award, MTU Outstanding Graduate Mentor Award, and the Ferdinand P. Beer andE. Russell Johnston Jr. Outstanding New Mechanics Educator Award.  He has published 34journal articles and book chapters and has been cited in the literature over 700 times

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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.

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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.

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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.

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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.

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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.

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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.

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