Materials Characterization using Scattering Techniques

Monday, February 27, 2012 3:00 pm – 4:00 pm
Room 610, M&M Building

Heinz Nakotte
Gardiner Professor, Chair of the Engineering Physics Committee, Department of Physics, New Mexico State University
and
Instrument Scientist, Single Crystal Diffractometer (SCD), Los Alamos Neutron Science Center, Los Alamos National Laboratory

Abstract

In many cases, materials properties of interest for applications are determined by the structuralfeatures at atomic, nano and/or micron level. While diffraction typically only provides a measureof the volume-averaged structure of the material of interest, the local structure is accessiblethrough total-scattering studies in combination with pair-distribution function analysis. In mylecture, I intend to discuss and compare the opportunities and limitations of total-scatteringstudies using neutrons and synchroton X-rays. I will present some recent results of two of myresearch projects, i.e. local structure of a non-platinum catalyst and evidence for resonant unitmodes in a framework structure that exhibit negative-thermal-expansion behavior. If time permits,I will also provide a brief summary of my other research projects.

Mesoscale Anisotropic Deformation and Damage Nucleation In Polycrystalline Ti Alloy

Friday, February 24, 2012 3:00 pm – 4:00 pm
Room 610, M&M Building

M. A. Crimp
Chemical Engineering and Materials Science
Michigan State University, East Lansing, MI

Abstract

A combination of experimental characterization and crystal plasticity finite element modeling(CPFEM) has been used to study the anisotropic deformation of a number of titanium alloys.Studies have been carried out in the near surface region of 4-point bend specimens, where theglobal stress can be approximated as uniaxial tension.  Specific microstructural patches havebeen characterized prior to deformation using electron backscattered electron diffractionorientation imaging microscopy (OIM).  Specimens have been deformed both in-situ in scanningelectron microscopy (SEM) and ex-situ, facilitating a range of experimental characterizationmethods including optical microscopy, atomic force microscopy, SEM based backscatteredelectron imaging, OIM, and channeling contrast imaging, as well as 3-D X-ray diffraction.  Thesestudies have allowed a comprehensive experimental characterization of the nature of plasticdeformation and damage nucleation in the microstructural patches.  To complement thesestudies, quasi 3-D FEM meshes, developed based the experimentally characterizedmicrostructural patches, have been computationally deformed.  While the simulations accuratelyreproduce significant aspects of the experimental studies, including some crystal rotations andsurface topography development, further work to include grain boundary behavior in thesimulations is needed.

More information: Mesoscale Anisotropic Deformation and Damage Nucleation In Polycrystalline Ti Alloy

BaTiO3 Glass-Ceramics Composites For High Energy Storage Capacitors

Thursday, February 23 2012 2:00 p.m.
Room 610, M&M Building

Douglas B. Chrisey
Department of Material Science and Engineering, Department of Biomedical Engineering
Rensselaer Polytechnic Institute, Troy, NY, 12180

Abstract

Renewable energy sources require large-scale power storage so that their inherently intermittent supply of power can meet demand.  For capacitive energy to have the necessary high volumetric and gravimetric energy storage density this will require the dielectric layer to simultaneously possess a high dielectric constant and a high breakdown strength, e.g., in excess of 10,000 and 1 MV/cm, respectively.  To be a realistic solution for renewable energy storage, it must also be low cost and scalable, i.e., no roadblocks from the laboratory prototype to large scale production, and to achieve the all of the aforementioned requirements we have exploited a glass-ceramic phase.  It is expected that glass-ceramics composites will have higher breakdown strength than that of a sintered ceramic alone, because the glass would displace the air-filled voids.  Due to the dielectric mixing rule, the dielectric constant of the composite mixture will then be limited by the low permittivity of the glass phase in comparison to the ceramic phase.  In our work, we use a glass phase that can undergo a phase transformation into BaTiO3-precipitating glass-ceramic by controlled crystallization (annealing temperature).  The benefit of doing this is that we achieve a higher dielectric constant of composite mixture, due to the additional high dielectric constant BaTiO3 phase, while also improving the high breakdown strength. It was demonstrated that this BaTiO3-precipitaing glass-ceramic and BaTiO3 ceramic composite are promising for improved dielectric properties for high-density energy storage capacitors.

Tech research: Solar power getting less expensive

HOUGHTON – Joshua Pearce wants to change the perception of solar power as a relatively expensive energy source used only in remote locations or by large utility companies, and hopes a recent analysis on the topic he was part of will help dispel that perception.

Pearce, who is an associate professor of electrical engineering and materials science at Michigan Technological University, said the analysis, “A Review of Solar Photovoltaic Levelized Cost of Electricity,” in the December issue of the science publication Renewable & Sustainable Energy Reviews, was begun by himself and colleagues at Queen’s University in Kingston, Ontario, and finished after he started at Tech this past summer.

“We had the study mostly done at Queen’s,” he said. “The journal it’s in only prints invited articles.”

The analysis printed in the magazine was a sort of extension of other work he and his Queen’s University colleagues had done, Pearce said.

“My group had done a lot of research on solar power for the Canadian government,” he said.

What that earlier research showed, Pearce said, was that costs for solar power have been dropping, largely due to better solar panel materials.

“We’ve made very significant progress on that,” he said.

Although the individual cells in most solar panels are still crystal based, Pearce said the materials they’re set in are better than the early days of solar panel technology in the 1970s. In the past, water would get into panels, leading to damage of the cells and panels and degradation of power output.

“Now, we have much better polymer backing,” he said.

Many panels have 25-year warranties, Pearce said. Annual degradation of power from a quality panel is 0.1 to 0.2 percent, rather than the previously assumed level of 1 percent or greater.

A relatively new technology involves the production of large sheets of material on which cells are placed in scribes engraved with lasers, Pearce said. Those are cheaper, but generally not as efficient as panels with individual crystal or polycrystal cells embedded in a polymer field.

The cost of solar panels dropped 70 percent since 2009, Pearce said.

After the burst of use of solar power in the 1970s, Pearce said there was a lull, which has since turned around.

“We’re back with industry support,” he said.

Pearce said there are about 100,000 workers in the solar-power industry, now, compared to about 80,000 workers in the coal industry five years ago.

Costs for start-up for solar power are going to vary based on the system used, Pearce said, but panels can be purchased for about $2,000 each.

“A system of a few thousand dollars is in the reach of a typical middle class family,” he said.

Panels with 50-year life expectancy aren’t very far away, Pearce said.

“We’re getting pretty close, now,” he said.

Although battery costs are declining, also, Pearce said the trend by solar-power users is to connect to their local electrical grid, eliminating the need for batteries and lowering the cost of the system.

Depending on variables, including location and type of system, Pearce said the cost for electricity is going to be attractive to many people.

“Solar is already competitive or better than conventional fossil fuels,” he said. “We’re going down (in cost) and we’re only going to continue to go down.”

Pearce said factors in the cost per watt of solar power include location, efficiency of systems, ability to connect to an electrical grid, government tax incentives and the willingness of lending institutions to fund installations of solar systems.

Getting lenders to accept solar power is going to be extremely important to its growth, Pearce said, which is one of the effects he’d like to see from the recently-published analysis.

“Financing matters,” he said.

Pearce said some recent years have shown a 100 percent increase in the use of solar power all over the world.

“It’s massively increasing,” he said.

Those uses include on houses, cottages and even big-box retailers.

Growth in the use of solar power should continue to increase, also, Pearce said.

“I’m very optimistic,” he said. “I think we’re going to see massive growth.”

Source: Mining Gazette