Marc A. Meyers - US grants

This is a proposal for a research program to study the role of interfaces in superplastic deformation and cavitation failure in ceramics. Superplastic forming offers the potential for near-net- shape processing of relatively complex shapes from viable structural ceramics. The propensity to cavitate during deformation, however, is one aspect of superplasticity that need to be better understood for this technique to gain prominence in ceramic processing. The proposed research addresses the critical issues relating to the cavitation problem. The PI intends to study the nucleation and growth of cavities during superplastic deformation as a function of the properties of the grain boundary phase. The research will include the in-house processing of controlled microstructures for the superplastic deformation studies.

The research aims at developing a fundamental understanding of shear-band initiation and propagation. The materials that will be investigated, titanium and aluminum alloys, have great importance in the aerospace industry; they undergo shear localization during plastic deformation and this is an important practical problem. Systematic and integrated experimental and theoretical investigation of the phenomenon of shear-band formation will be carried out. This will lead to the prediction and control of shear instability and to the establishment of its effect on the strength and failure modes of a broad class of materials. Dynamic experiments will be performed, in order to generate shear bands under controlled conditions. The Hopkinson bar experimental technique will be used with both hat-shaped and double-notched specimens. Pulse amplitude and shape in the Hopkinson bar will be varied to control the extent of shear-band propagation. This will be followed by microstructural characterization involving optical, scanning, and transmission electron microscopy. The microstructure after controlled high-strain-rate deformation stages and prior to the onset of macroscopic shear localization, will also be systematically investigated in order to establish which internal defects can lead to the initiation of localization and to characterize the microstructural evolution. The microstructure at the tip of the shear band will be examined in order to establish the structural changes in this zone prior to shear band extension.

This project on nanocrystalline materials has three primary objectives. First, the spark erosion technique for producing nanoparticles of a very wide range of materials will be investigated and optimized for maximum yield of the desired particle sizes and compositions. Second, a variety of nanoparticle systems representing superconducting, magnetic and structural properties will be extensively characterized. Third, the consolidation of the nanoparticles into macroscopic samples retaining the unusual properties of the precursors, utilizing dynamic extrusion and shock consolidation as well as conventional processing methods, will be implemented. Using liquid dielectics, the spark erosion technique has been shown to yield high purity particles of metals, alloys, oxides, carbides, and semiconductors in sizes from nanometers to micrometers at significant production rates. Sparks erosion may be carried out also in ultrapure gases. This approach increases the performance of this method in the synthesis, treatment and subsequent handling of nanoparticles. The characterization of various types of nanoparticles produced will involve diffraction (x-ray, electron, neutron), high resolution TEM, surface analysis, as well as methods particularly suited to specific systems such as optical and Mossbauer spectroscopy, transport measurements and magnetic properties. Research is planned to demonstrate and extend the capabilities of the spark erosion method to produce economically significant quantities of various types of nanoparticles, as well as to investigate some of the unique properties of these systems in particulate and consolidated form.

The Institute for Mechanics and Materials promotes research and education activities at the interface of materials engineering and solid mechanics. A number of workshops are conducted to bring forth major challenges in these areas. A number of pre-doctoral fellowships are supported that promote interaction of researchers with the industrial community. Several national and international visitors are invited to the Institute to bring new ideas together and to promote collaborative work.

This proposal aims to gain fundamental understanding of the
deformation mechanisms that operate in nanostructured metals and
alloys, in particular in those produced by severe plastic deformation
(SPD) methods. Based on this knowledge it further aims to develop full
capability to manufacture these materials in high quality bulk forms.

The extremely attractive (and rare) combination of mechanical
properties (high strength, ductility, fatigue resistance) and
manufacturability of these materials leads to a new class of high
performance alloys for structural uses. It is understood that this
combination of properties is due to the formation of nano-scale grain
sizes in these materials, but the mechanisms responsible for the high
strength combined with high ductility are not well understood. This
presents a fundamental obstacle to the optimization of these
materials, or to predictions of the performance of these materials in
applications.

An integrated approach with strong emphasis on manufacturing is
proposed. On the theoretical side, deformation mechanisms will be
simulated with crystal-plasticity aggregate models and with detailed
models of the grains and grain boundaries. The experimental program
covers a wide a range of strain rates and temperatures, texture
development, and in situ transmission electron microscopy and atomic
force microscopy to directly verify deformation mechanisms. The
experimental results will provide validation to the theoretical
modeling and manufacturing process simulations.

Finally, simulations of the manufacturing processes will enable
process parameter optimization. A complete, miniature, yet fully
scalable, manufacturing facility will be designed and implemented.

The significant impacts of the proposed research are made possible by
the acquired fundamental understanding of the deformation mechanisms,
and include advances in manufacturing techniques to produce these
highly desirable materials in bulk. The miniature manufacturing
facility will become a source of significant quantities of
nano-structured alloys. Finally, the proposal will provide students at
the UCSD and at local K-12 schools with interdisciplinary education in
a cutting-edge area of research.

This is a grant for a collaborative research program between the University of Ancona, Ancona, Italy and the University of California at San Diego. The objective of the study is to produce very refined grain size to the nanoscale through severe plastic deformation. The University of Ancona has a grant from the Istituto Nazionale per la Fisica della Materia (INFM) for "Physical Aspects of Ultrafine Grained Aluminum Alloys," and this NSF grant is a mechanism to substantially enhance collaboration by permitting funding that is complementary to the INFM study. A major goal of the INFM study is to use equal channel angular (ECA) pressing of aluminum alloys as a means to produce nanoscale grain size aluminum alloys. The effort by the US team is directed towards understanding the specific mechanisms by which the severe plastic deformation leads to a refined grain size. The study is expected to alleviate the empiricism involved in the quest to produce very fine-grained alloys of commercial value.

The UCSD group will utilize both the mechanical facilities at UCSD and the University of Ancona. Graduate students, postdoctoral scholars and faculty will participate in exchanges on long-term basis (three months to one year) between these institutions. The collaborative program is very complementary in scope, and will give an opportunity to enhance the research by taking advantage of the international expertise.

This NSF project is co-funded by the Office of Multidisciplinary Activities, the Division of Materials Research (Metals Research) and International Office (Western Europe) as a Cooperative Activity in Materials Research between the NSF and Europe (NSF 02-135). This project is being carried out in collaboration with University of Ancona, Ancona, Italy.

NON-TECHNICAL DESCRIPTION: The synthetic materials (metals, polymers, ceramics, and composites) developed in research laboratories during the past century have revolutionized life. However, at present, the possibilities of designing and producing synthetic materials with improved performance are being exhausted. Therefore researchers are turning their attention to nature, trying to understand it better, with the goal of mimicking its designs. This emerging field of Biomimetics seeks to design properties into materials modeled after biological systems. The proposed study addresses the abalone shell that is highly prized as a source of nacre, or mother-of-pearl. Yet, is comprised of 95% chalk, which is weak and brittle. The complex nanostructure and microstructure of the shell are such that adding 5% of an organic glue leads to a toughness that is orders of magnitude higher than that of chalk. The goal of the proposed research is to understand, at the fundamental level, why the shell is so strong and to use this knowledge to develop a new generation of ceramic composites with superior properties.
TECHNICAL DETAILS: A four-year program with strong characterization and analysis components will be carried out: development of new micro- and nano-mechanical testing methods to establish viscoelastic mechanical response of the protein layer(s) that act as an adhesive between tiles. This approach requires the use of atomic force microscopy, nanoindentation and nanoscratch tests, a miniaturized shear test (analogous to the meso scale test used by the PI), modeling mechanical responses through novel mechanisms incorporating viscoelastic response of organic layer; identification and quantification of the changes in the organic layers that occur after deformation using micro-Raman spectroscopy and FTIR, and identification of mechanisms by which tiles grow in "Christmas tree" pattern and transmit their orientation from level to level. Based on these observations, a detailed growth model for aragonite (the orthorhombic phase of CaCO3) will be developed. The ultimate goal is the use of biologically-inspired techniques to synthesize new materials. Research will be carried out at University of California San Diego, Universidad Nacional Autonoma de Mexico, and the Lawrence Livermore National Laboratory. Graduate and undergraduate students from San Diego and Mexico will be involved in the learning process, as well as high school students. The Preuss School, a charter high school that is designed as in intensive college preparatory educational program for low-income students in the grades 6-12, will be involved. These students come from families whose parents have not received college training. Two senior high school students will work during the school year (4-6 hrs/week, as allowed by The Preuss School) and full time during their summer breaks (6 weeks). It is emphasized that no abalone are harmed or killed for these experiments.
This project is co-funded by the Office of International Science and Engineering and the Division of Materials Research.

ID: MPS/DMR/BMAT(7623) 0757787 PI: Roeder, Ryan ORG: Notre Dame University

Title: Biological Materials Science Symposium

INTELLECTUAL MERIT: The award will support a three and one-half day symposium on biological materials science at the annual meeting of The Minerals, Metals, and Materials Society (TMS) to be held March 9-13, 2008 in New Orleans. An international slate of keynote and invited speakers will address sessions on Mechanical Behavior of Biological Materials, Implant Biomaterials, Bioinspired Design and Processing, Scaffold Biomaterials, and Functional Biomaterials. The program will incorporate a session for presentation of posters as part of a student poster contest. Funds will be used exclusively for supporting student participation through registration waivers and travel awards. The six-member organizing committee includes international representatives from Europe and Asia. The goals of the symposium are to generate enthusiasm and interest among students in the field of biomaterials, to facilitate interaction of students and junior investigators with senior investigators in the field, to educate participants about prior and impending advances in biomaterials, and to promote a global exchange of knowledge. Symposium sessions address topics of current interest in the field and each will offer a blend of keynote speakers, invited speakers, and contributed talks.

BROADER IMPACTS: The symposium will foster international contacts among scientists in the biomaterials field and will provide exceptional opportunities to stimulate student interest and involvement in the field.

ID: MPS/DMR/BMAT(7623) 0855598 PI: Roeder, Ryan ORG: Notre Dame University

Title: Biological Materials Science Symposium

INTELLECTUAL MERIT: The Biological Materials Science Symposium at the Annual Meeting of the Minerals, Metals, and Materials Society (April 2009) provides a venue for researchers exploring the intersection of materials science and biology. Materials science and engineering is expected to play a highly significant role in the foreseeable future of biomedicine. Conversely, noting that materials science finds its roots in solid state physics and chemistry, biology is logically the next great frontier for materials science. The BMS Symposium is different from other related symposia in emphasizing the primacy of the study of biological materials to the development of biomaterials and biomimetic materials, as well as the application of materials science and engineering principles to the study of biological materials. The well-planed program of the proposed five-day symposium provides an important venue for discussion of the role of biologically-derived materials in the broader field of biomaterials, which encompasses not only bioderived materials but also biomimetic, bioinspired, and biocompatible materials that may not be of biological origin. Outstanding keynote and other invited speakers from around the world have been asked to highlight recent advances and emerging trends in the biomaterials field in each of eight topical sessions.

BROADER IMPACTS: A particularly strong feature of this symposium is its commitment to the involvement of students, whose travel to the symposium will be supported in part by this award and who will participate in a student poster contest for which prizes will be given to the best presentations. These students will not only be active symposium participants but will have ample opportunity to meet an international array of biomaterials researchers and learn of their work. Sessions of the broader meeting are specifically designed to highlight the opportunities for women and underrepresented minorities in the field.

TECHNICAL: Abalone shell is tough and fracture resistant. The structure has a brick-and-mortar organization with calcium carbonate (aragonite) bricks surrounded by the organic mortar. The toughness is attributed to the organized arrangement of the aragonite platelets and nanoscale features present at the mineral/organic interface. These nanoscale features include mineral bridges, nanoasperities on the surface of the aragonite tiles and the viscoelastic/adhesive properties of the organic. The main objectives of this work are to fabricate model ceramic/polymer laminates, identify and quantify the contributions of microstructural features that have been attributed to the toughening of the shell. This work is expected to lead to a new class of bioinspired composite materials that are strong, hard and fracture resistant. Students will be cross-trained in biology, materials science and nanoscience.

NON-TECHNICAL DESCRIPTION: Bioinspired materials are emerging as a new class of synthetic structures. The abalone shell is tough and fracture resistant, despite being built from weak constituents: organic matter and a soft mineral (ceramic). Under magnification, the shell has a "brick-and-mortar" structure of mineral bricks and organic mortar. Bioinspired synthetic layered materials based on this structure are expected to have exceptional toughness and fracture resistance. Fabrication and testing of layered organic (polymer) / ceramic structures that duplicate the structure of the abalone shell is the main focus of research. This work is expected to lead to a new class of composite materials that are strong, hard and fracture resistant. Graduate, undergraduate and high school students will be cross-trained in biology, materials science and nanoscience. New classes will be introduced into the curriculum and outreach to underrepresented student populations is a part of this project.