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Materials | About the 2013 Journal of Materials Science Robert W. Cahn Best Paper Prize

About the 2013 Journal of Materials Science Robert W. Cahn Best Paper Prize

The Editors and Publisher are pleased to announce the winning paper and 11 finalists for the 2013 Journal of Materials Science Robert W. Cahn Best Paper Prize (the “Cahn Prize”). The Cahn Prize has been named in honor of the Journal’s founding editor, the late Professor Robert Wolfgang Cahn.

Each month the Editors selected a paper published in that month's issues via a rigorous nomination and voting procedure. The winning paper will be selected from the twelve finalists by a separate panel of distinguished materials scientists. The authors of the winning paper will receive an award of $5,000.

WINNING PAPER February: Dislocation controlled wear in single crystal silicon carbide 

Maneesh Mishra, Izabela Szlufarska

10853_2012_6916_Fig11    ©Springer
For better design and durability of nanoscale devices, it is important to understand deformation in small volumes and in particular how deformation mechanisms can be related to frictional response of an interface in the regime where plasticity is fully developed. Here, we show that when the size of the cutting tool is decreased to the nanometer dimensions, silicon carbide wears in a ductile manner by means of dislocation plasticity. We present different categories of dislocation activity observed for single asperity sliding on SiC as a function of depth of cut and for different sliding directions. For low dislocation density, plastic contribution to frictional energy dissipation is shown to be due to glide of individual dislocations. For high dislocation densities, we present an analytical model to relate shear strength of the sliding interface to subsurface dislocation density. Furthermore, it is shown that a transition from plowing to cutting occurs as function of depth of cut and this transition can be well described by a macroscopic geometry-based model for wear transition.

December: Scaling of conductivity and Young’s modulus in replicated microcellular materials 

Andreas Mortensen, Yves Conde, Andreas Rossoll, Christopher San Marchi

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Scaling exponents for the conductivity and stiffness of replicated microcellular materials exceed commonly predicted values of 1 and 2. We show here that this is caused by the fact that, in replicated microcellular materials, the solid architecture varies with the relative density: a simple derivation based on the physics of powder consolidation returns and explains the observed scaling behaviour. The same derivation also gives an explanation for Archie’s law, known to describe the conductivity of wet soils.

November: Internal melting and coarsening of liquid droplets in an Al–Cu alloy: a 4-D experimental study 

Sofiane Terzi, Luc Salvo, Michel Suéry, Arne K. Dahle, and Elodie Boller

10853_2013_7557_Fig5
...We report in detail the melting and isothermal holding of a model binary alloy where a remarkable number of liquid droplets were observed to develop and coalesce. Various computational tools have been used to study their statistical evolution as well as the local ripening mechanisms involved. We analysed an interesting case of particle coarsening which differs from classical case studies by the fact that the fast-diffusing liquid phase is entrapped within the slow-diffusing solid medium.

October: Inertial stabilization of flexible polymer micro-lattice materials 

Sha Yin, Alan J. Jacobsen, Linzhi Wu, and Steven R. Nutt

10853_2013_7452_Fig6
Soft micro-lattice materials with different lattice geometries were fabricated using a self-propagating photopolymer waveguide process... The micro-lattice structures exhibited super compressibility and increased strength. The observed strength increase, particularly for high aspect ratio and high strain rate, was attributed to inertial stabilization.

September: Thermodynamic investigations of copper oxides used as conversion type electrodes in lithium ion batteries 

Maren Lepple, Robert Adam, Damian M. Cupid, Peter Franke, Thomas Bergfeldt, Daniel Wadewitz, David Rafaja, Hans J. Seifert

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...Based on this data as well as on other literature data, a thermodynamic description of the Li–Cu–O system valid in the battery relevant temperature regime was developed using the CALPHAD method. From this thermodynamic description, titration curves for CuO and Cu2O cathodes, which give the equilibrium cell voltage as a function of lithium content along a selected composition path, were calculated at different temperatures.

August: Isochronal crystallization kinetics of Fe40Ni40B20 amorphous alloy 

Yazhu Ma, Bastian Rheingans, Feng Liu, Eric J. Mittemeijer

CI_Image_10853_2013_7354_Fig3_250px
...The crystallization reaction can be described by nucleation with a continuous nucleation rate incorporating a nucleation index a and by growth in three dimensions according to a linear growth law. The kinetics of transformation and the resulting microstructure observed upon isochronal annealing clearly differ from those upon isothermal annealing investigated in a previous study, reflecting different mechanisms operating upon isochronal and isothermal crystallization.

July: Creep in an electrodeposited nickel 

Vaclav Sklenicka, Kveta Kucharova, Marie Kvapilova, Milan Svoboda, Petr Kral, Gabriele Vidrich

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...The results indicate that the creep resistance of the nanocomposite may be noticeably improved compared to the monolithic nickel due to the interaction of the particles with dislocation motion. It was found that the applied stress interval can be divided into lower and higher stress intervals corresponding to dislocation (power-law) and exponential creep regions, respectively...

June: Oxidation of nanodiamonds and modulation of their assembly in polymer-based nanohybrids by field-inducement 

Hong-Baek Cho, Son Thanh Nguyen, Tadachika Nakayama, Minh Triet Tan Huynh, Hisayuki Suematsu, Tsuneo Suzuki, Weihua Jiang, Shaifulazuar Bin Rozali, Yoshinori Tokoi, Yeung-Ho Park, Koichi Niihara

10853_2013_7228_Fig5    ©Springer
Linear assembly of densely packed oxidized nanodiamonds (OxNDs) was performed in polymer-based nanohybrid films. A homogeneous suspension of the pre-polymer polyepoxide and OxNDs was placed onto a polyamide spacer and subjected to an electric field in order to induce the relocation and assembly of the fillers before the mixture became cross-linked. The OxNDs suspended readily, forming linear assemblies of OxNDs (LAOxNDs) of varying thicknesses, aligned perpendicular to the film surfaces. Nanohybrid films with linear assemblies of LAOxNDs exhibited a moderate increase in thermal conductivity while maintaining the electrical insulation properties of the polyepoxide. Mechanisms for the field-induced fabrication and the structural variation of LAOxNDs in the pre-polymer matrix are elucidated in relation to the variations in physical properties. The present air oxidation process and field-induced application are simple but effective in enhancing the physical properties of polymer-based hybrids, and hence, has the potential for applying in the fabrication and modulation of nanocomposite materials.

May: Atomic structure of hardening precipitates in an Al–Mg–Zn–Cu alloy determined by HAADF-STEM and first-principles calculations: relation to η-MgZn2 

Calin D. Marioara, Williams Lefebvre, Sigmund J. Andersen, Jesper Friis

10853_2013_7158_Fig4    ©Springer
The structures of two nanoscale plate precipitates prevalent at maximum strength and over-aged conditions in a 7449 Al–Mg–Zn–Cu alloy were investigated. Models derived from images of high angle annular dark field scanning transmission electron microscopy were supported by first-principles calculations. Both structures are closely linked to the η-MgZn2 Laves phase through similar layers of a rhombohedral atomic subunit. The finest plate contains one such layer together with a layer of an orthorhombic unit. The second plate contains rhombohedral layers only, normally four, but rotated relatively to form different stacking variants, one of which may be likened to η. For both structures, the same atomic planes describe the main interface with Al. Both plates could be described in space group P3. The unit cells comprise interface and arbitrary numbers of {111}Al (habit) planes. Eight Al-planes were included in the first-principles calculations. The enthalpy indicates high layer/unit stability. The plate thickness can be understood by a simple mismatch formulation.

April: Effects of impurities on the lattice dynamics of nanocrystalline silicon for thermoelectric application 

Tania Claudio, Gabi Schierning, Ralf Theissmann, Hartmut Wiggers, Helmut Schober, Michael Marek Koza, Raphaël P. Hermann

10853_2012_6827_Fig1    ©Springer
Open Access
Doped silicon nanoparticles were exposed to air and sintered to form nanocrystalline silicon. The composition, microstructure, and structural defects were investigated with TEM, XRD, and PDF and the lattice dynamics was evaluated with measurements of the heat capacity, of the elastic constants with resonant ultrasound spectroscopy and of the density of phonon states (DPS) with inelastic neutron scattering. The results were combined and reveal that the samples contain a large amount of silicon dioxide and exhibit properties that deviate from bulk silicon. Both in the reduced DPS and in the heat capacity a Boson peak at low energies, characteristic of amorphous SiO2, is observed. The thermal conductivity is strongly reduced due to nanostructuration and the incorporation of impurities.

March: Modelling the deformation of a confectionery wafer as a non-uniform sandwich structure 

I. K. Mohammed, M. N. Charalambides, J. G. Williams, J. Rasburn

10853_2012_7034_Fig19    ©Springer
The aim of this research was to model the mechanical behaviour of wafers found in various confectionery products in order to optimise the manufacturing stage. Compression and bending tests showed that the mechanical behaviour of the wafer was characteristic of a brittle foam. The internal microstructure of the wafer sheet was examined with an optical microscope which showed that the wafer possessed a sandwich structure with a porous core between two denser skins. An analytical model was developed to calculate the individual moduli of the wafer core and skin sections. These modulus values were used in a finite element (FE) model which consisted of a simple repetitive geometry. The FE model simulated the linear deformation of the wafer under compression and bending. The predictions from the analytical and numerical models were compared. They were found to agree in compression but deviated under bending due to the large mismatch of the core and skin moduli.

January: Effect of high pressure and high temperature on the microstructural evolution of a single crystal Ni-based superalloy 

Inmaculada Lopez-Galilea, Stephan Huth, Werner Theisen, Thomas Fockenberg, Sumit Chakraborty

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The application of high nearly hydrostatic pressures at elevated temperatures on the LEK94 single crystal (SX) nickel-based superalloy directly affects its microstructure. This is due to a combination of the effect of pressure on the Gibbs free energy, on the diffusion coefficients of the alloying elements, on the internal coherent stresses, and on the porosity distribution. The last effect depends at least on the first three. Therefore, based on the theoretical influences of the pressure, the main objective of this work is to understand, by means of an experimental work, the effect of high pressure at elevated temperature during annealing on the evolution of the phases morphology, and porosity of the high-temperature material LEK94. Specifically, pressures up to 4 GPa, temperatures up to 1180 °C, and holding times up to 100 h were investigated. The main findings are that, porosity can be considerably reduced without affecting significantly the γ/γ′ microstructure by high pressure annealing and the verification that increasing the external pressure stabilizes the γ′-phase.