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1 Jun 2012

Volume 111, Issue 11, Articles (11xxxx)

Issue Cover Spotlight Figure

J. Appl. Phys. 111, 112501 (2012); http://dx.doi.org/10.1063/1.4726137 (1 page)

Jiuhua Chen, Haozhe Liu, and Naurang L. Saini
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back to top Interdisciplinary and General Physics

Solidification of Au-Cu-Si alloys investigated by a combinatorial approach

Shiyan Ding, John Gregoire, Joost J. Vlassak, and Jan Schroers

J. Appl. Phys. 111, 114901 (2012); http://dx.doi.org/10.1063/1.4722996 (6 pages)

Online Publication Date: 1 June 2012

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Composition libraries of Au-Cu-Si films comprising 800 composition patches were fabricated through co-sputtering deposition from elemental targets. The gold composition varies between 47% (compositions are in atomic percentage) and 81%, copper between 8% and 40%, and silicon between 6% and 36% within the library. We designed and used a high-throughput optical characterization method to detect melting and solidification based on changes in the film’s contrast; further microscopy characterization reveals the microstructure. This approach reveals the composition dependence of the nucleation temperature and primary phase, which allows us to draw conclusions about glass forming ability and to identify bulk metallic glass forming compositions. Our solidification results suggest that the best glass forming composition coincides with the composition at which a transition from one primary phase to another occurs. We show that in general this transition is not at the eutectic composition but at the lowest nucleation temperature.
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81.30.Fb Solidification
64.70.dj Melting of specific substances
64.70.dg Crystallization of specific substances
68.55.at Other materials
81.15.Cd Deposition by sputtering

On the nature of the coefficient of friction of diamond-like carbon films deposited on rubber

D. Martinez-Martinez, J. P. van der Pal, M. Schenkel, K. P. Shaha, Y. T. Pei, and J. Th. M. De Hosson

J. Appl. Phys. 111, 114902 (2012); http://dx.doi.org/10.1063/1.4723830 (6 pages)

Online Publication Date: 1 June 2012

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In this paper, the nature of the coefficient of friction (CoF) of diamond-like carbon (DLC)-protected rubbers is studied. The relative importance of the viscoelastic and adhesive contributions to the overall friction is evaluated experimentally by modifying the contact load and the adhesive strength between the surface and the counterpart. The results indicate that the increase of CoF during the tribotests under non-lubricated conditions is caused by the increase of the adhesive contribution to friction motivated by the growth of the contact area during the test. In the case of oil lubricating condition, the adhesive force is minimized and the CoF is observed to decrease during the tribotest. This is caused by the reduction of the viscoelastic contribution due to the variation of the shape of the contact area. The role of the microstructure of the DLC film on the efficiency of the oil lubrication is also discussed.
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68.55.A- Nucleation and growth
62.20.Qp Friction, tribology, and hardness
81.40.Jj Elasticity and anelasticity, stress-strain relations
81.40.Pq Friction, lubrication, and wear
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

The steepest S curve of spreading and collecting flows: Discovering the invading tree, not assuming it

E. Cetkin, S. Lorente, and A. Bejan

J. Appl. Phys. 111, 114903 (2012); http://dx.doi.org/10.1063/1.4721657 (7 pages) | Cited 1 time

Online Publication Date: 4 June 2012

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Spreading and collecting flows are united by the flow design known as the S-curve: when plotted versus time, the size of the domain that is filled or emptied has a history that is shaped as an S. Here, we show that the fastest spreading or collecting (i.e., the steepest S curve) is discovered by allowing the tree architecture to morph freely, toward greater access over time, in accord with the constructal law of design in nature. The angles between the lines of the invading flow architecture can be selected such that the overall flow proceeds the fastest, covering the greatest territory at any moment. The design is a sequence of two distinct phenomena: “invasion” by channels and branches that grow fast, and “consolidation” by slow diffusion perpendicular to the channels. Invasion and consolidation collaborate hand-in-glove to facilitate the spreading or collecting over the available finite area or volume.
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68.08.Bc Wetting
47.60.Dx Flows in ducts and channels
47.11.Df Finite volume methods

Enhanced x-ray imaging for a thin film cochlear implant with metal artefacts using phase retrieval tomography

B. D. Arhatari, A. R. Harris, A. G. Paolini, and A. G. Peele

J. Appl. Phys. 111, 114904 (2012); http://dx.doi.org/10.1063/1.4724343 (6 pages)

Online Publication Date: 5 June 2012

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Phase retrieval tomography has been successfully used to enhance imaging in systems that exhibit poor absorption contrast. However, when highly absorbing regions are present in a sample, so-called metal artefacts can appear in the tomographic reconstruction. We demonstrate that straightforward approaches for metal artefact reconstruction, developed in absorption contrast tomography, can be applied when using phase retrieval. Using a prototype thin film cochlear implant that has high and low absorption components made from iridium (or platinum) and plastic, respectively, we show that segmentation of the various components is possible and hence measurement of the electrode geometry and relative location to other regions of interest can be achieved.
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87.59.-e X-ray imaging
87.57.cj Contrast
87.57.cp Artifacts and distortion
87.57.nm Segmentation
87.57.nf Reconstruction

Phase transition in BCx system under high-pressure and high-temperature: Synthesis of cubic dense BC3 nanostructured phase

P. V. Zinin, L. C. Ming, H. A. Ishii, R. Jia, T. Acosta, and E. Hellebrand

J. Appl. Phys. 111, 114905 (2012); http://dx.doi.org/10.1063/1.4723275 (9 pages) | Cited 1 time

Online Publication Date: 7 June 2012

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We synthesized a cubic BC3 (c-BC3) phase, by direct transformation from graphitic phases at a pressure of 39 GPa and temperature of 2200 K in a laser-heated diamond anvil cell. A combination of x-ray diffraction, electron diffraction, transmission electron microscopy (TEM) imaging, and electron energy loss spectroscopy (EELS) measurements lead us to conclude that the obtained phase is hetero-nano-diamond, c-BC3. High-resolution TEM imaging of the c-BC3 specimen recovered at ambient conditions demonstrates that the c-BC3 is a single, uniform, nanocrystalline phase with a grain size of about 3–5 nm. The EELS measurements show that the atoms inside the cubic structure are bonded by sp3 bonds. The zero-pressure lattice parameter of the c-BC3 calculated from diffraction peaks was found to be a = 3.589 ± 0.007 Å. The composition of the c-BC3 is determined from EELS measurements. The ratio of carbon to boron, C/B, is approximately 3 (2.8 ± 0.7).
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62.50.-p High-pressure effects in solids and liquids
64.70.K- Solid-solid transitions
64.70.Nd Structural transitions in nanoscale materials
81.16.-c Methods of micro- and nanofabrication and processing
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
61.50.Ks Crystallographic aspects of phase transformations; pressure effects

Sound propagation in periodic urban areas

Miguel Molerón, Simon Félix, Vincent Pagneux, and Olivier Richoux

J. Appl. Phys. 111, 114906 (2012); http://dx.doi.org/10.1063/1.4725487 (9 pages)

Online Publication Date: 7 June 2012

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This paper presents an experimental and numerical study of low frequency sound propagation in regular urban areas, under the assumption of a periodic distribution of buildings. Although the radiation losses above the urban canyons are generally significant, our results show that the effects of the periodicity still occur. Band diagrams are notably characterized, both numerically and experimentally, to investigate the effect of the radiation above the periodic structure. The problem is tackled using a coupled modal-finite elements method. The main idea is to turn the original unbounded domain into an equivalent waveguiding structure, with PML bounding the originally open region. The experimental study is performed in a scale model of urban area. Numerical and experimental results on both the band diagrams and the wavefield propagating through the lattice are in good agreement.
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43.55.-n Architectural acoustics
02.70.Dh Finite-element and Galerkin methods
43.25.Cb Macrosonic propagation, finite amplitude sound; shock waves

Radiation and near field in resistance-inductor circuit transients

Damir Latypov and John Bulmer

J. Appl. Phys. 111, 114907 (2012); http://dx.doi.org/10.1063/1.4728234 (8 pages)

Online Publication Date: 13 June 2012

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A full wave solution to the classical problem of a transient response in an RL circuit is analyzed. We show that when radiation effects are rigorously taken into account, the response differs from a familiar exponential decay. The circuit behaves more like an RLC circuit and can exhibit an underdamped response. As a result of a two way energy transfer between the circuit and the near field in the underdamped regime, despite the radiation losses, current decay may be slower than predicted by the standard RL circuit model. During a transient, when retardation effects become important, inductance can no longer be defined as a coefficient of proportionality between the magnetic flux through the circuit and the current in the circuit. If rate of current decay is nearly constant, one can define a time-dependent generalized inductance which turns into conventional inductance after time D/c, where D is the diameter of the current loop. Connection of this generalized inductance with the radiation damping problem is discussed. The theory developed in this paper has been used to analyze ultra wide band radiation observed during a fast laser triggered superconducting to normal transition of a superconducting switch.
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84.30.Bv Circuit theory
41.20.Gz Magnetostatics; magnetic shielding, magnetic induction, boundary-value problems
85.25.-j Superconducting devices
84.32.Dd Connectors, relays, and switches

Non-contact characterization of graphene surface impedance at micro and millimeter waves

J. S. Gómez-Díaz, J. Perruisseau-Carrier, P. Sharma, and A. Ionescu

J. Appl. Phys. 111, 114908 (2012); http://dx.doi.org/10.1063/1.4728183 (7 pages) | Cited 2 times

Online Publication Date: 15 June 2012

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The experimental characterization of the surface impedance of monolayer graphene at micro and millimeter wave frequencies is addressed. Monolayer graphene is transferred on a substrate stack, which is placed in the cross-section of a rectangular waveguide. In the fundamental mode, this setup is equivalent to a TE-polarized plane wave impinging under oblique incidence on an infinite graphene sheet, and similarly, the surface impedance of the graphene is a simple lumped element in a transmission-line model, that exactly represents the electromagnetic problem under study. Using this model, we propose a technique based on transmission matrices to accurately extract the surface impedance. The method is able to relax the influence of the substrates tolerances by taking advantage of the graphene infinitesimally small electrical thickness. It can also account for any gap between the sample and the test waveguide, thereby allowing to disregard graphene-metal contact resistance issues. The approach has been successfully applied to characterize graphene samples at X and Ka bands. The extracted surface impedances fit the Drude conductivity model in the absence of interband transitions, and provides a wideband frequency independent resistance (in the range of KΩs) and a weak inductive behavior (in the range of pHs).
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84.40.Az Waveguides, transmission lines, striplines
73.25.+i Surface conductivity and carrier phenomena
72.80.Vp Electronic transport in graphene
73.40.Cg Contact resistance, contact potential
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