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JOM SEPTEMBER 2008
VOLUME 60, NO.09
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![September 2008 Cover: The magnetic domains within thin-film rings are shown in this colorized image courtesy of the National Institute of Standards and Technology. Changes in color indicate changes in the directions of the magnetization of the material. This issue considers materials at the nano-scale, including an update on progress on spintronics for emerging memory devices, materials and coatings for energetics, and twinning in nano-metals. Professional society governance comes under a microscope, as well, with the publication of proposed new TMS bylaws found on page 21. A ballot to vote on the bylaws is on page 24. [Click to enlarge]](http://www.tms.org/pubs/journals/jom/0809/cover-0809.gif)
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Magneto-electric Nanostructures
Materials and Coatings for Energetics
Twinning in Nano-metals |
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Materials and Processing for Lithium-ion Batteries
By: Claus Daniel
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Magneto-electric Nanostructures: Nanomaterials Committee
Seung HG. Kang, Qualcomm, Inc.
Materials and Coatings for Energetics: Surface Engineering Committee
Narendra B. Dahotre, University of Tennessee and Sudipta Seal, University of Central Florida
Twinning in Nano-metals: Nanomechanical Material Behavior Committee
Amit Misra, Los Alamos National Lab. |
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Published monthly by The Minerals, Metals & Materials Society for its members, JOM is a technical journal devoted to exploring the many aspects of materials science and engineering.
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MAGNETO-ELECTRIC NANOSTRUCTURES
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Recent Advances in Spintronics for Emerging Memory Devices
[p. 28
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Author(s): Seung H. Kang
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The emerging field of spintronics has the potential to bring game-changing opportunities to nanoelectronic technologies far beyond its traditional contribution to mass storage applications such as hard disk drives. The value proposition is timely since the dominant semiconductor industry is in pursuit of “More-than-Moore” to extend the technology roadmap or to create functional diversifications through enhanced system platforms. This article overviews a promising spintronic device in conjunction with recent breakthroughs in tunnel magnetoresistance and spin-transfer-torque magnetization switching.
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Materials and Surfaces for Energetics
[p. 36
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Author(s): Narendra B. Dahotre and Sudipta Seal
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The global demand for energy and materials is enormous and all the physical characteristics of current life depend on the flow and transformation of energy and materials through the techno-economic system. Efforts are focused on reducing conversion losses, developing more efficient energy systems, increasing the use of renewable energy sources, and minimizing the risks associated with new energy concepts. In light of this scenario, four papers organized under the topic of “Materials and Surfaces for Energetics” deal with various aspects of this complex subject matter.
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Functional Nanostructures through Nanosecond Laser Dewetting of Thin Metal Films
[p. 37
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Author(s): H. Krishna, C. Favazza, A.K. Gangopadhyay, and R. Kalyanaraman
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Techniques for processing nanoscale metallic structures with spatial order and tunable physical characteristics, such as size and microstructure, are paramount to realizing applications in the areas of magnetism, optics, and sensing. This paper discusses how pulsed laser melting of ultrathin films can be a powerful but simple and cost-effective technique to fabricate functional nanostructures. Ultrathin metal films (1 nm to 1,000 nm) on inert substrates like SiO2 are generally unstable, with their free energy resembling that of a spinodal system. Such films can spontaneously evolve into predictable nanomorphologies with well-defined length scales. This study reviews this laser-based experimental technique and provides examples of resulting robust nanostructures that can have applications in magnetism and optics.
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Materials and Processing for Lithium-ion Batteries
[p. 43
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Author(s): Claus Daniel
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Lithium-ion battery technology is projected to be the leapfrog technology for the electrification of the drivetrain and to provide stationary storage solutions to enable the effective use of renewable energy sources. The technology is already in use for low-power applications such as consumer electronics and power tools. Extensive research and development has enhanced the technology to a stage where it seems very likely that safe and reliable lithium-ion batteries will soon be on board hybrid electric and electric vehicles and connected to solar cells and windmills. However, the safety of the technology is still a concern, service life is not yet sufficient, and costs are too high. This paper summarizes the state of the art of lithium-ion battery technology for nonexperts. It lists materials and processing for batteries and summarizes the costs associated with them. This paper should foster an overall understanding of materials and processing and the need to overcome the remaining barriers for a successful market introduction.
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Solar Energy-Conversion Processes in Organic Solar Cells
[p. 49
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Author(s): Zhihua Xu, Huidong Zang, and Bin Hu
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Organic semiconducting materials have demonstrated attractive light-absorption and photocurrent-generation functions due to their delocalized π electrons as well as intra-molecular and inter-molecular charge separation processes. On the other hand, organic semiconducting materials have easy property tuning, are mechanically flexible, and have large-area thin film formation properties. As a result, organic materials have become potential candidates in solar energy applications. This article will review critical energy-conversion processes in organic solar cells with the focus on singlet and triplet photovoltaic responses.
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Spatial Ordering and Anisotropy in Surface Stress Domains and Nanostructural Evolution
[p. 54
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Author(s): Y.F. Gao, J.Y. Meng, A. Goyal, and G.M. Stocks
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The role of elastic interaction has been well recognized for various growth modes and nanostructural self-organization on solid surfaces. Examples include spontaneous formation of stress domains in reconstructed surfaces or in-phase–separating monolayers, meandering and bunching of surface steps, and quantum dot formation in heteroepitaxial thin film growth. The long-range spatial ordering in these strain-mediated nanostructural evolution phenomena on solid surfaces is critically dependent on the anisotropy. A universal formulation has been developed to examine the energetically favored orientation with respect to parameters that represent the anisotropy in elasticity and applied stress.
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Twinning in Nanocrystalline Metals
[p. 59
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Author(s): Amit Misra
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Twinning is a commonly observed deformation mode in low-symmetry crystals such as hexagonal-close packed metals. In face-centered cubic (fcc) metals, deformation twinning is typically observed only under extreme loading conditions such as shock or very low temperature deformation. This commentary introduces six articles that review recent work in the area of deformation twinning in nanometals, and synthesis, characterization, and atomistic modeling of nanoscale growth twins.
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Deformation Twinning in Bulk Nanocrystalline Metals: Experimental Observations
[p. 60
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Author(s): Y.T. Zhy, X.Z. Liao, and X.L. Wu
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Deformation twins have been observed in nanocrystalline (nc) fcc metals with medium-to-high stacking fault energies such as aluminum, copper, and nickel. These metals in their coarse-grained states rarely deform by twining at room temperature and low strain rates. Several twinning mechanisms have been reported that are unique to nc metals. This paper reviews experimental evidences on deformation twinning and partial dislocation emissions from grain boundaries, twinning mechanisms, and twins with zero-macro-strain. Factors that affect the twinning propensity and recent analytical models on the critical grain sizes for twinning are also discussed. The current issues on deformation twinning in nanocrystalline metals are listed.
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Determining the Stress Required for Deformation Twinning in Nanocrystalline and Ultrafine-grained Copper
[p. 66
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Author(s): Vinay Sriram, Jenn-Ming Yang, Jin Ye, and Andrew M. Minor
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Deformation twinning in nanocrystalline and ultrafine-grained materials has attracted much attention in recent years due to the ability of a high density of twin boundaries to dramatically improve mechanical properties such as yield strength and ductility. Various processing conditions such as ball milling, cryomilling, electrodeposition, and equi-channel angular extrusion have been used to form deformation twins in metals. Most techniques for estimating the shear stress needed to form deformation twins are based indirectly on the processing conditions. Here, a new method to directly measure the shear stress needed to form twin boundaries through in-situ transmission electron microscopy nanocompression testing will be described.
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The Effect of Twin Plane Spacing on the Deformation of Copper Containing a High Density of Growth Twins
[p. 71
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Author(s): Z.W. Shan, L. Lu, A.M. Minor, E.A. Stach, and S.X. Mao
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In-situ tensile straining in a transmission electron microscope was used to investigate the role of twin plane spacing on the deformation and fracture mechanism of pure copper containing a high density of nanoscale growth twins. Real-time and post-mortem observations clearly reveal that twin plane spacing plays a key role in determining the operative deformation mechanism and therefore the subsequent crack propagation path. The deformation mechanism transition, which results from changes in the twin plane spacing, has implications for interpreting the unusual mechanical behavior of the copper with a high density of nanoscale growth twins.
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Nanoscale Growth Twins in Sputtered Metal Films
[p. 75
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Author(s): X. Zhang, O. Anderoglu, R.G. Hoagland, and A. Misra
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This article reviews recent studies on the mechanical properties of sputtered copper and 330 stainless-steel films with {111} nanoscale growth twins preferentially oriented perpendicular to growth direction. The mechanisms of formation of growth twins during sputtering, unusually high strengths, and excellent thermal stability of nanotwinned structures are highlighted.
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An Atomistic Perspective on Twinning Phenomena in Nano-enhanced fcc Metals
[p. 79
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Author(s): Frederic Sansoz, Hanchen Huang, and Derek H. Warner
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Twin boundaries exist in bulk metals, and they are even more common in metallic nanomaterials. Molecular simulation has made it possible to achieve a predictive understanding of the atomic mechanisms leading to the enhanced properties of nano-twinned metals. Taking nanowires as prototypes, this paper presents an atomistic view of twin structure and its important role in synthesis and in mechanical deformation.
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Strengthening Mechanisms and Dislocation Dynamics in Twinned Metal Nanowires
[p. 85
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Author(s): A.J. Cao, Y.G. Wei, and Scott X. Mao
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Microtwins are frequently observed in face-centered-cubic (fcc) metal nanowires with low stacking fault energy. The authors have previously reported that the tensile yield strength of copper nano wires can be increased by the presence of twin boundaries. In this work simulations are carried out under both uniaxial tension and compression loading, to demonstrate that the strengthening effects are inherent to these nanowires, independent of the loading condition (tensile/compressive). It appears that the strengthening mechanism of the twinned nanowires can be attributed to stress redistribution due to the change of crystallographic orientations across twin boundaries, which requires larger external stress to make them yield as compared to the twin-free wire.
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“Best Practice” Governance Requirements and the TMS Response: Revised Bylaws Ready for Your Vote
[p. 19
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Author(s): Diran Apelian
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Like all organizations, TMS operates using a well-defined system of bylaws and policies. They have served us well for many years, but the time has come for a change. In March 2008 an ad hoc Committee on Governance was created to review the TMS Bylaws, Administrative Manual, and Policy Manual, other documents as necessary, and current practice and procedures for consistency, clarity, and to ensure that they are current. The results are reported here.
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Proposed Bylaws of The Minerals, Metals & Materials Society, Inc.
[p. 21
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Author(s):
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As a result of a review by the ad hoc Committee on Governance, changes are proposed to the TMS Bylaws. Members can vote on the changes using the ballot at the end of this article.
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Member News
[p. 18
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Author(s):
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Terence G. Langdon has been honored by European and Chinese academies of science; Todd M. Osman, former director of materials technology for TMS, takes on the position of executive director of the Materials Research Society; and former TMS President Kenneth J. Richards, 1932–2008, is remembered.
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Foundation News
[p. 35
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Author(s):
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In July, the TMS Foundation, working with ASM International’s Materials Education Foundation, co-sponsored an outreach program that puts promising high school students in contact with materials science and engineering professionals and demonstrates the possibilities of a career in MSE. The Capital District Materials Camp was held on the campus of Rensselaer Polytechnic Institute in Troy, New York, July 7–11.
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In the Final Analysis
[p. 4
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Author(s): James J. Robinson
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At a national conference for association leaders, a study was released concerning the “Decision to Volunteer.” The study analyzed input from thousands of professionals affiliated with dozens of professional societies, and found some common threads.
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Book Reviews
[p. 53
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Author(s):
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Featuring reviews of
Ceramics Science and Technology&mdash:Volume 1: Structure, edited by Ralf Reidel and I.-Wei Chen; reviewed by Waseem Haider
Clay Swelling and Colloid Stability, written by Martin Smalley; reviewed by Charles Sorrell
Materials Handbook: A Concise Desktop Reference, Second Edition, edited by François Cardarelli; reviewed by George Galanes
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News & Update
[p. 6
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Author(s):
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Items of note from the field, profession, and society.
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Upcoming Topics
[p. 65
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Author(s):
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Featuring upcoming editorial topics for January through June 2009, plus information on how to submit a manuscript.
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Meetings Calendar
[p. 89
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Author(s):
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A monthly round-up of soon-to-be-held meetings and upcoming calls for papers.
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Materials Resource Center: Jobs, Consultants, Marketplace
[p. 92
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Author(s):
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Positions and services available.
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End Notes: “Gender Equity in University Materials Science Departments”
[p. 96
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Author(s): Maureen Byko
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What will it take to attract more women to university materials science and engineering (MSE) departments—new policies or just new attitudes? The answers remain murky, but leaders of MSE departments from across the United States gathered in May to at least consider the question. For three days, nearly 100 department chairs and professors, both male and female, met at the Workshop on Gender Equity in Materials Science and Engineering at the University of Maryland. The National Science Foundation and the U.S. Department of Energy organized the conference on behalf of the University Materials Council.
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![September 2008 Cover: The magnetic domains within thin-film rings are shown in this colorized image courtesy of the National Institute of Standards and Technology. Changes in color indicate changes in the directions of the magnetization of the material. This issue considers materials at the nano-scale, including an update on progress on spintronics for emerging memory devices, materials and coatings for energetics, and twinning in nano-metals. Professional society governance comes under a microscope, as well, with the publication of proposed new TMS bylaws found on page 21. A ballot to vote on the bylaws is on page 24. [Click to enlarge]](http://www.tms.org/pubs/journals/JOM/0809/cover-0809.large.gif)