|
For additional spotlight stories please visit the Archive page.
|
October 2012 JOM Examines Nanoscale Materials |
Read it Online on Springerlink
Posted on: 9/22/2012 12:00:00 AM... Big developments at the tiniest length scales is the theme of the October 2012 JOM. Eighteen articles within four technical topics, as well as a feature, explore new understanding, applications, and future implications of advancement in nanoscale materials. To read this JOM issue online, go to Springerlink.
In addition to the technical content, be sure to take a look at this month’s News and Update section, which announces the 2013 JOM Technical Calendar and presents the 2013 TMS Board of Directors nominees. Other features include an overview of the NanoNuclear 2012 workshop and an update on how the National Science Foundation is linking great laboratory research with the world of business through its I-Corps program.
An overview of technical papers and features supporting this month’s nanoscale materials theme is offered below.
FUNCTIONAL MATERIALS
Bulk Nanostructured Metals for Innovative Applications
Ruslan Z. Valiev, Ilchat Sabirov, Alexander P. Zhilyaev, and Terence G. Langdon
Nanostructuring of various materials is a key for obtaining extraordinary properties that
are very attractive for different structural and functional applications. During the last two decades, the production of bulk nanostructured materials (BNM) by severe plastic deformation techniques has attracted special interest since it offers new opportunities for the fabrication of commercial nanostructured metals and alloys for various specific applications. Very significant progress has been made in this area in recent years, which is evident by the first production of advanced pilot articles from nanostructured metals with new functionality. These aspects of innovations of BNM processed by severe plastic deformation are discussed in this overview.
Self-Ordered Nanoporous Alumina Templates Formed by Anodization of Aluminum in
Oxalic Acid
Ioan Vida-Simiti, Dorel Nemes, Nicolaie Jumate, Gyorgy Thalmaier, and Niculina Sechel
Anodic aluminum oxide (AAO) membranes with highly ordered nanopores serve as ideal templates for the formation of various nanostructured materials. The procedure of the template preparation is based on a two-step self-organized anodization of aluminum. In the current study, AAO templates were fabricated in 0.3 M oxalic acid under the anodizing potential range of 30–60 V at an electrolyte temperature ~5 °C. The as obtained layers are amorphous, the mean pores size is between 40-75 nm and is increasing with the increase of the anodization potential. Well defined pores across the whole aluminum template, a pore density of ~1010 pores/cm2, and a tendency to form a porous structure with hexagonal symmetry were observed.
Thermal Expansion of Carbon Nanofiber-Reinforced Multiscale Polymer Composites
Ronald Poveda, Sriniket Achar, and Nikhil Gupta
Improved dimensional stability of composites is desired in applications where they are
exposed to varying temperature conditions. The present study aims at analyzing the
effect of vapor grown carbon nanofibers (CNFs) on the thermal expansion behavior of
epoxy matrix composites and hollow particle filled composites (syntactic foams).
Embedded Binary Eutectic Alloy Nanostructure
D.C. Chrzan, et. al.
The properties of binary eutectic alloy nanostructures embedded within a matrix are discussed. It is demonstrated that GeAu and GeSn nanostructures embedded in SiO2 form in a bi-lobed structure as predicted by a simple theory. Tuning the composition enables one to tune the transformation temperature. Possible technological applications of these nanostructures are discussed.
Fabrication of Patterned Magnetic Nanomaterials for Data Storage Media
Chulmin Choi, Kunbae Noh, Cihan Kuru, Li-Han Chen, and Sungho Jin
Patterned media (PM) for magnetic information storage have received increased attention
in recent years as the primary candidate for 1 Terabit/in2 or higher recording density for computer hard disk drives. A patterned media consists of a periodic array of well-defined magnetic islands, each of which can store one bit of data. This paper deals with a recent investigation of various fabrication approaches, nanostructural features, and magnetic properties for the bit patterned media.
PROGRESS WITH LEAD-FREE SOLDERS
Topics in Lead-Free Solders: Interfacial and Sn Whisker Growth
Srinivas Chada
This commentary provides context for the following papers within this technical topic.
Correlation between Surface Morphology Evolution and Grain Structure: Whisker/Hillock Formation in Sn-Cu
Fei Pei, Nitin Jadhav, and Eric Chason
Sn whisker and hillock formation is a reliability risk that has become increasingly important as the electronics industry has moved towards Pb-free manufacturing. The research presented in this paper uses in-situ SEM/EBSD to simultaneously monitor the evolution of surface morphology and grain orientation in Sn surfaces in order to correlate whisker/hillock initiation with the underlying microstructure. Because rough films are difficult to measure with EBSD, a unique procedure was developed to make Sn-Cu samples with ultra-flat surfaces so that a large fraction of Sn grains can be indexed over repeated scans.
The Interphases Formed during the Very Early Stage Liquid Solder/Metal Substrate Interaction of the Soldering Process
Kwang-Lung Lin, Yu-Wei Lin, and Chang-Ho Yu
The initial step of the soldering process may consist of dissolution of metal substrate and the subsequent counter diffusion between substrate atoms and solder elements. The counter diffusion gives rise to the formation of the various interphases (phases at the interfacial region). A close investigation of the interphases formed at the very early stage of soldering will provide the root out understanding to the soldering process. A number of studies have attempted to adopt rapid quench of the soldered specimen at the very early stage of interaction, around 10 s or less after solder melts, so as to freeze the occurrences. The present article provides a review of the achievements of these studies, and the interphases formed during the very early stage of the soldering process for various solder systems.
BULK NANOSTRUCTURED MATERIALS
Structure-Property-Functionality Relationships in Bimetal Composites
Jian Wang and Yao Shen
This commentary discusses the importance of novel materials for future energy technologies and the role of interfaces in the development of extraordinary and unusual material properties.
Structure-Property-Functionality of Bimetal Interfaces
I.J. Beyerlein, N.A. Mara, J. Wang, J.S. Carpenter, S.J. Zheng, W.Z. Han, R.F. Zhang, K. Kang, T. Nizolek, and T.M. Pollock
To best elucidate interface structure-functionality relationships, the studies in this paper are focused on simple layered composites composed of an alternating stack of two metals with bi-metal interfaces spaced less than 100 nm. These nanocomposites are fabricated by either a bottom-up method (physical vapor deposition) or a top-down method (accumulative roll bonding) to produce two distinct interface types. Atomic-scale differences in interface structure are shown to result in profound effects on bulk-scale properties.
Structure and Property of Interfaces in ARB Cu/Nb Laminated Composites
J. Wang, K. Kang, R.F. Zhang, S.J. Zheng, I.J. Berelein, and N.A. Mara
In this paper, bulk Cu/Nb multilayered composites with high interfacial content have been synthesized via the accumulative roll bonding (ARB) method. The authors provide an overview of the microscopy and simulation results on the structure of this interface at an atomic level and its influence on interface properties, such as interface shear resistance and its ability to absorb point defects and nucleate dislocations nucleation.
Interfacially-Driven Deformation Twinning in Bulk Cu-Ag Composites Melts
N.A. Mara, I.J. Beyerlein, J.S. Carpenter, and J. Wang
Interfaces and interface/defect interactions increasingly dominate the mechanical response of materials as the dimensions of the grains decrease to the nanoscale. Recently, we reported unusually profuse deformation twinning in Ag-Cu layered eutectic composites with bi-layer thicknesses in the submicron regime (~200-400 nm) at room temperature and low strain rates. Using atomistic simulations and dislocation theory, we propose that the Ag-Cu interface facilitated deformation twinning in Cu by permitting the transmission of twinning partials from Ag to Cu. In this way, twins in Ag can provide an ample supply of twinning partials to Cu to support and sustain twin growth in Cu during deformation. Interface-driven twinning as revealed by this study suggests the exciting possibility of altering the roles of dislocation slip and twinning through the design of hetero-phase interface structure and properties.
DEFECT ROLES IN NANOMATERIALS
Mechanical Behavior and Fabrication of One-Dimensional Nanomaterials
Jian Wang and Nan Li
This commentary provides context for the following papers within this technical topic.
In situ TEM Investigation of the Mechanical Behavior of Micronano-Scaled Metal Pillars
Zhiwei Shan
In this paper, recent progress in applying a unique quantitative transmission electron microscope deformation technique on micronano-scaled metal pillars is reviewed.
The Effect of Size on the Deformation Twining Behavior in Hexagonal Close-Packed
Ti and Mg
Qian Yu, Raja K. Mishra, and Andrew M. Minor
In hexagonal close packed (HCP) structural materials, the limited activation of different slip mechanisms results in alternative deformation mechanisms such as twinning becoming relevant to plasticity. As external/internal dimension refinement affects operative mechanisms are commonly used to tune the mechanical properties of materials, understanding the effect of size on deformation twinning in HCP materials is a critical issue for improving their strength and ductility. Recent in situ and ex situ small-scale testing experiments have generated insights into size effects on twinning by deforming single crystal systems with different sizes. The authors review some of the recent results in this field, including studies of the size related deformation twinning behavior in Ti, Mg and their alloys.
Exploring Deformation Mechanisms in Nanostructured Materials
Julia Greer
This article provides a comprehensive overview of the state-of-the-art experimental and computational methods applied to investigating mechanical behavior and microstructural evolution in small-scale metallic systems, whose deformation is governed by intricate interactions of defects with internal interfaces, as well as with free surfaces. Attention is focused on the effects of multiple grain boundaries spanning the sample volume (nanocrystalline and polycrystalline metals). This overview sheds light on the relative role of intrinsic vs. extrinsic length scale limitations on the deformation mechanisms in nanostructured metals, which has significant implications for the development of new materials with tunable mechanical
properties.
A Framework of Growing Crystalline Nanorods
Hanchen Huang
The growth of crystalline nanorods has become a common practice in the absence of a solid framework, in either theoretical or conceptual form. This paper presents such a framework, and puts it in historical perspective of a broader field of crystal growth. This framework derives from three scientific advancements in crystal growth, with focus on multiple-layer surface steps: (1) the diffusion barrier of adatoms down multiple-layer surface steps, (2) the formation and stability of multiple-layer surface steps, and (3) the dimension of surface facets that are bounded by competing monolayer and multiplelayer surface steps.
Misfit Strain Relaxation Mechanisms in Core/Shell Nanowires
H.J. Chu, C.Z. Zhou, J. Wang, and I.J. Beyerlein
In the past decade core/shell nanowires (NWs) have attracted much attention due to
the broad variety of potential applications of these structures in future nanoelectronic
and nanophotonic devices. Because of the lattice mismatch between the core and shell
material, crystal dislocations often form to relax the mismatch strains. This paper proposes a relaxation mechanism for the misfit strains generated at the core/shellinterface in NWs, in which lattice dislocations nucleate from the outer surfaces and then propagate to the core/shell interface. An analytical model is developed to predict the critical shell thickness corresponding to defect-free core/shell NWs with respect to the growth direction.
FEATURE
Undergraduate Education in Nanotechnology and Nanoscience
Nitin Chopra and Ramana G. Reddy
As a result of the expanding market of nanoscale devices and composites, it is becoming critical to train undergraduate students in this area and to make them aware of methodologies for handling and processing nanomaterials. This article offers an overview of initiatives and strategies for ensuring that future generations are appropriately prepared for these new challenges and opportunities.
For additional spotlight stories please visit the Archive page.
|