The ability to intelligently control, manipulate, reproduce, scale and tailor the properties and performance of materials and structures, at the macro, micro and nano-scale, will continue to play a pivotal role in aerospace, construction, electronics, energy, healthcare, manufacturing, telecommunications and transportation industries.
Bandgap engineering of semiconductors is a specific example of this approach.1–4 The award of the 2014 Nobel Prize in Physics5 to Isamu Akasaki, Hiroshi Amano and Shuji Nakamura is an excellent testimony to the role of materials in energy conversion. Their invention of the gallium nitride (GaN) blue light emitting diodes (LED) has led to bright and energy-saving white light sources.6–8
Emerging Materials Research is pleased to present a themed issue of the journal dedicated to the proceedings of selected talks that were presented at the TMS 2014 RF Mehl Medal Symposium on frontiers in nanostructured materials and their applications.9 This symposium9 was held during February 16–20, 2014, in San Diego, California, USA. The eight sessions, in this Symposium, comprised 76 presentations. The sessions were organized and chaired by Haiyan Wang (Texas A&M University), Ravi Ravindra (New Jersey Institute of Technology, NJIT), Xinghang Zhang (Texas A&M University), Ke Lu (Institute of Metal Research), Dieter Wolf (Argonne National Laboratory), Steve Pennycook (Oak Ridge National Laboratory), Evan Ma (Johns Hopkins University), Ram Katiyar (University of Puerto Rico), Somuri Prasad (Sandia National Laboratories), Nitin Chopra (University of Alabama), Ashutosh Tiwari (University of Utah) and Sudhakar Nori (North Carolina State University, NCSU).
This symposium was organized in celebration of the pioneering contributions of Professor Jagdish (Jay) Narayan, winner of the 2014 TMS RF Mehl Medal and Institute of Metals Lecture Award. The sessions included topics such as recent developments in synthesis and processing, atomic and nano-scale characterization, structure and property correlations and modeling of nanostructured materials and their applications. The primary emphasis, in electronic materials, was on thin-film heterostructures across the misfit scale, nanodots, nanorods, nanotubes and related devices. Specific topics of interest included fundamentals of thin-film epitaxy across the misfit scale through the paradigm of domain-matching epitaxy, novel thin-film heterostructures integrated with silicon, three-dimensional epitaxial self-assembled structures, quantum-well nanostructuring leading to nano-pocket LED structures, fundamentals of ion-solid and laser-solid interactions, laser annealing, rapid thermal processing, pulsed laser deposition, and formation of novel supersaturated semiconductor alloys and nanostructured materials for the next-generation devices and systems. Sessions on structural materials focused on the role of defects and interfaces in controlling properties and selective alloying of grain boundaries to address metastability and performance of nanostructured materials.
Professor Jagdish Narayan is the John Fan Family Distinguished Chair Professor in the Department of Materials Science and Engineering at NCSU. He is also a Distinguished Visiting Scientist at the Oak Ridge National Laboratory. He obtained his Bachelor of Science from the Indian Institute of Technology, Kanpur, in 1969 and his Master of Science (1970) and PhD (1971) from the University of California, Berkeley. He worked as a Research Metallurgist at Lawrence Berkeley National Laboratory (1971–1972) and Senior Scientist and Group Leader at Oak Ridge National Labs (1972–1984), before joining NCSU in 1984 as Senior Professor and Director of the Microelectronics Center of North Carolina. He also served as Director of Division of Materials Research (1990–1992) of the National Science Foundation.
Professor Narayan has published over 500 scientific papers in international journals and an equal number in conference proceedings, nine edited books, an h-index approaching 70 and over 40 US Patents, which have over 20,000 citations. He is a Fellow of eight professional societies, and is the winner of the 1999 ASM Gold Medal, 2011 Acta Materialia Gold Medal and 2014 TMS RF Mehl Gold Medal. He has won the 2012 Holladay Medal and 2011 Reynolds Award from NCSU, the 2014 O. Max Gardner Award and the 2014 North Carolina Award in Science.
The first of the themed issue papers10 in this issue of Emerging Materials Research presents a study on the ‘Hall–Petch k dependencies in nanopolycrystals’. This paper by Ronald William Armstrong of the Center for Energetic Concepts Development, Department of Mechanical Engineering, University of Maryland, College Park, Maryland, USA, presents a study on the measurements of the Hall–Petch plastic flow stress dependence on the reciprocal square root of polycrystal grain diameter at nanopolycrystal grain sizes. The results occasionally fall short of expectations. The present report reviews experimental and theoretical aspects of such behaviors for a number of metal systems. Comparison with the results on copper had led to prediction of a dislocation pile-up mechanics, the basis of an even stronger grain size dependence that is now shown to carry over to an explanation of similar results that have been reported, recently, for cold-drawn eutectoid steel wires. In this current review, emphasis is given on the additional important results achieved on the production of nanoscale zinc and tungsten carbide materials by Professor Jay Narayan and colleagues at NCSU.
The second themed issue paper11 in this issue focuses on ‘Producing ultrafine-grained materials through severe plastic deformation’. In this paper, by Megumi Kawasaki of the Division of Materials Science and Engineering, Hanyang University, Seoul, South Korea, and Terence G. Langdon of the Department of Aerospace and Mechanical Engineering, University of Southern California, Los Angeles, California, USA, the authors discuss the processing of bulk metals through the application of severe plastic deformation (SPD). SPD has provided an opportunity for achieving excellent grain refinement to the submicrometer or even the nanometer range. This produces materials exhibiting very high strength and with a potential for use in superplastic-forming operations at elevated temperatures. The basic principles of SPD processing are reviewed in this report with an emphasis on two procedures, equal-channel angular pressing (ECAP) and high-pressure torsion (HPT).
‘An observation about global microstructure of ECAPed magnesium’ by Xing Jiao of the Department of Chemical and Materials Engineering, University of Nevada, Reno, Nevada, USA, and Qizhen Li of the School of Mechanical and Materials Engineering, Washington State University, Pullman, Washington, USA, is the third themed issue paper12 in this issue of Emerging Materials Research. This paper reports the application of a popular processing method, ECAP. ECAP was employed to process commercial pure magnesium. A magnesium sample experienced eight ECAP cycles, and then was sliced and prepared to observe the microstructure of two cross-section planes. The overall microstructure was obtained for both planes to reveal the global microscopic features of ECAPed magnesium. The results indicate that there are extensive deformation twins; different regions of each plane have different amounts of twins; overall, the center region tends to have fewer twins compared with the peripheral region for each cross-section plane; and the area of the region with low twin density decreases when the cross-section plane moves close to the middle of the sample along the pressing direction.
Shiva Adireddy, Venkata Sreenivas Puli, Samuel Charles Sklare, Tiffany Jialin Lou and Brian Charles Riggs of the Department of Physics and Engineering Physics, Ravinder Elupula and Scott Michael Grayson of the Department of Chemistry, Douglas Brian Chrisey of Materials Engineering, Department of Physics and Engineering Physics of Tulane University, New Orleans, Lousiana, USA, report their studies on ‘PVDF–BaSrTiO3 nanocomposites for flexible electrical energy storage devices’. This themed issue paper13 describes studies on the energy storage capability of Ba0·5Sr0·5TiO3 (BST)–polyvinylidene fluoride (PVDF) nanocomposites. Morphologically uniform BST colloidal nanocubes were prepared in high yield by a solvothermal method at temperatures as low as 150°C. As-synthesized BST nanocubes were used as fillers (35 vol%) in PVDF polymer matrix. The unique dielectric-polymer films display an enhanced dielectric constant (>27) and enhanced electrical breakdown strength (Eb) (2·85 MV/cm). The resulting dielectric energy density for the BST–PVDF nanocomposite is 9·7 J/cm3, which is a result of the interplay between dependencies of permittivity and breakdown strength on volume fraction. The authors propose that the strong nanoparticle–polymer matrix interfacial interaction is the main reason for the observed improved dielectric properties. This wet-chemical-assisted fabrication approach can be readily extended to other combinations of polymers and ceramics with concomitant improvement in properties. Key parameters of various materials (e.g. chemical composition, shape, size and surface reactivity) can be readily controlled in this method, which opens up a new pathway to highly flexible macroelectronics.
‘Synthesis, characterisation and thermal degradation studies of copolymer resin’ by Wasudeo B. Gurnule and Vaishali R. Bisen of the Department of Chemistry, Kamla Nehru Mahavidyalaya, Nagpur, Maharashtra, India, is a contributed general paper14 in this issue of Emerging Materials Research. In this study, a copolymer (2,4-DBPHF) has been synthesized using monomers 2,4-dihydroxybenzoic acid, phenyl hydrazine and formaldehyde in 1:1:2 molar proportions. The structure of 2,4-DBPHF copolymer has been elucidated on the basis of elemental analysis and various physicochemical techniques, such as ultraviolet–visible spectroscopy, Fourier transform infrared spectroscopy, 1H-NMR spectroscopy and 13C-NMR spectroscopy. A detailed thermal degradation study of this new copolymer has been carried out to ascertain its thermal stability. Thermal degradation curve is discussed, which shows three decomposition steps. The activation energy (Ea) and thermal stability have been calculated by using Freeman–Carroll, Sharp–Wentworth, Friedman, Chang and Coats–Redfern methods. Thermodynamic parameters such as entropy change (ΔS), apparent entropy change (S*) and frequency factor (z) have also been evaluated on the basis of the data of Freeman–Carroll method.
The last two contributed general papers15,16 in this issue of Emerging Materials Research are by Chengbin Liu of the School of Civil and Environmental Engineering, University of Science and Technology Beijing, Beijing, China, and the Department of Hydraulic and Architectural Engineering, Beijing Vocational College of Agriculture, Beijing, China, and Hongguang Ji and Juanhong Liu of the School of Civil and Environmental Engineering, University of Science and Technology Beijing, Beijing, China. In ‘Characteristics of slag fine-powder composite cementitious material-cured coastal saline soil’,15 the authors present a case study. Cement pile as slope support is used in a thermal coal storage and distribution base project in Caofeidian district. Taking into account the potential hazards of cement-cured saline soil, this research concerns a new type of coastal saline soil-curing agent to explore methods to prohibit the hazards of soluble ions in saline soil. On the basis of compressive strength, scanning electron microscopy, energy-dispersive spectrometry, X-ray diffraction analysis and a series of experiments, the strength, water stability, resistance capacity to seawater corrosion, microstructure and hydration products of SM agent-cured saline soil have been studied. The test results show that the curing agent reacts with Cl− in saline soil and generates a hexagonal plate crystal and needle-like Kuzel’s salt crystal, which thereby increases the strength of cured soil in the absence of certain potential hazards of the saline soil.
In ‘Anti-seawater corrosion performance of coastal saline soil cured by slag composite cementitious material’,16 the authors present their results of anti-seawater corrosion performance of slag composite cementitious material-cured coastal saline soil in one year. Based on compressive strength, scanning electron microscopy, electron-dispersive spectrometry and X-ray diffraction analysis, this paper presents studies on anti-seawater corrosion performance, microstructure and hydration products of the shell of SM agent-cured saline soil in seawater curing. The test results show that the SM agent-cured coastal saline soil in sea water generates compact hard CaCO3 shell; this, thereby, not only prevents seawater erosion, but also prevents the Ca(OH)2 to dissolve erosion, which is the fundamental reason why SM agent has a good anti-seawater corrosion performance.
As 2014 comes to a close, on behalf of the Editorial Board of Emerging Materials Research and on my behalf, I acknowledge and thank the contributions and support of Ms. Sohini Banerjee, Dr. Victoria Rae and Ms. Michelle Yeomans.
