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Your search keyword '"Greene, J.E."' showing total 150 results
Start Over Author "Greene, J.E." Publisher elsevier b.v.
150 results on '"Greene, J.E."'

34. Bendable bulk metallic glass: Effects of a thin, adhesive, strong, and ductile coating

Author

Chu, Jinn P., Greene, J.E., Jang, Jason S.C., Huang, J.C., Shen, Yu-Lin, Liaw, Peter K., Yokoyama, Yoshihiko, Inoue, Akihisa, and Nieh, T.G.

Subjects
*METALLIC glasses, *ADHESIVES, *DUCTILITY, *SURFACE coatings, *STRENGTH of materials, *SHEAR (Mechanics), *TRANSMISSION electron microscopy, *DEFORMATIONS (Mechanics), *INTERFACES (Physical sciences)
Abstract

Abstract: We demonstrate, for the first time, that a thin, strong, ductile, and adhesive coating renders bulk metallic glasses (BMGs) bendable. The bending ductility of 3mm thick BMGs, Zr50Cu30Al10Ni10 in this case, can be dramatically enhanced from ∼0% to ∼13.7% by the deposition of a thin bilayer film on the tensile side of the BMG sample. The bilayer, consisting of a 25nm thick Ti adhesive layer with a 200nm thick metallic glass (MG) overlayer, exhibits the required synergistic combination of good adhesion, high strength, and ductility compared with other single-layer films examined (Ti, TiN, and MG). Cross-sectional scanning and transmission electron microscopy, together with finite element modeling, reveal that the bilayer coating absorbs deformation while allowing more homogeneous formation of a high density of smaller shear bands at the bilayer/BMG interface. The bilayer coating, in turn, covers surface weak points and minimizes the formation of localized shear bands which lead to catastrophic failure under bending. As a result, the average shear-band spacing in bilayer-coated BMGs is small, 54μm, and approximately equal to that found in bendable, 450μm thick, MG ribbons. Thus, coated BMGs can accommodate large strains and overcome the MG size effect, without sacrificing their extraordinary mechanical properties. Our results for both coated and uncoated BMGs, as well as previously reported results for uncoated metallic glasses, with thicknesses ranging from ribbons to thin plates to bulk, are well described by a simple power law relationship between plastic strain to failure and shear band spacing. This scaling law may be useful in guiding future experiments toward producing more flexible BMGs. [Copyright &y& Elsevier]

Published
2012
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37. Hydrogen desorption kinetics and Ge<f>2H6</f> reactive sticking probabilities on Ge-adsorbed Si(<f>0 1 1</f>)

Author

Kim, H. and Greene, J.E.

Subjects
*SILICON, *THERMAL desorption, *ELECTRON spectroscopy
Abstract

Modeling of Si1−xGex(0 1 1) gas-source epitaxy from hydride precursors requires knowledge of reactive sticking probabilities and hydrogen desorption kinetics. We use D2 temperature programmed desorption (TPD), reflection high energy electron diffraction (RHEED), Auger electron spectroscopy (AES), and kinetic modeling to determine hydrogen desorption kinetics from, and Ge2H6 reactive sticking probabilities at, Si and Ge sites on Ge-adsorbed Si(0 1 1) samples with Ge surface coverages θGe between 0 and 1 ML. Following Ge adsorption, the samples were exposed to atomic D until saturation coverage at 250 °C. TPD spectra consist of five second-order peaks due to D2 desorption from, in order of decreasing temperature, Si rest-atom and adatom monodeuterides, Si dideuteride, and Ge rest-atom and adatom monodeuteride phases. The maximum temperatures of all five peaks shift to lower values with increasing θGe. We attribute this, as in the case of Ge-adsorbed Si(0 0 1), to a decrease in Si–D and Ge–D binding energies due to long-range electronic interactions. Ge/Si(0 1 1) surface reconstructions, determined by RHEED, are “16×2” with θGe<0.4 ML and “2×8” at higher coverages. Quantitative θGe values were obtained by fitting the D2 TPD spectra and validated using in situ AES. Based upon θGe vs Ge2H6 exposure data and modeling of the adsorption kinetics, we obtain zero-coverage Ge2H6 reactive sticking probabilities of 1.9×10−2 and 4.8×10−3 at Si and Ge sites, respectively. [Copyright &y& Elsevier]

Published
2002
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