Thermo-Mechanical and Size-Dependent Behavior of Freestanding AuAg and Nanoporous-Au Beams

2006 ◽  
Vol 976 ◽  
Author(s):  
Erkin Seker ◽  
Jianzhong Zhu ◽  
Hilary Bart-Smith ◽  
Matthew Begley ◽  
Robert Kelly ◽  
...  
Keyword(s):  
Thermal Treatment ◽  
Mechanical Characterization ◽  
Tensile Failure ◽  
Porosity Evolution ◽  
Size Dependent ◽  
Dependent Behavior ◽  
Low Elastic Modulus ◽  
Chemical Inertness ◽  
Percentage Yield ◽  
Significant Effort

AbstractNanoporous gold (np-Au), produced by selectively removing silver from an AuAg alloy, has recently gained considerable attention from the scientific community. Biocompatibility, chemical inertness, increased surface area, relatively low elastic modulus, and ease of synthesis make np-Au an important candidate for biomedical, catalytic, and MEMS applications. Np-Au films also offer substantial ground for theoretical and empirical research, including mechanical characterization, fracture mechanics, and porosity evolution. Even though a significant effort has been directed towards exploring blanket np-Au films (i.e., foils, strips), to our knowledge no work has been done on fabricating or investigating freestanding np-Au structures (i.e., micro-beams, cantilevers). Recently we have developed techniques to create freestanding clamped np-Au beams with widths from 5 to 40 microns and lengths from 20 to 500 microns. The percentage yield was more than 97% for 2880 beams on a 2-inch wafer. A critical step in the fabrication process, necessary to prevent tensile failure of the beams during dealloying, is a thermal heat treatment prior to dealloying. The study of thermal treatment of beams at temperatures between 100°C and 600°C prior to dealloying revealed three distinct beam behavior regimes, namely quasi-elastic buckling, plastic buckling, and material interdiffusion. This paper will present the preliminary results from thermal treatment experiments particularly focusing on how beam dimensions affect percentage yield and beam fracture.

The role of rough surface in the size-dependent behavior upon nano-indentation

2021 ◽  
pp. 103836
Author(s):  
Ding Tang ◽  
Leilei Zhao ◽  
Huamiao Wang ◽  
Dayong Li ◽  
Yinghong Peng ◽  
...  
Keyword(s):  
Rough Surface ◽  
Nano Indentation ◽  
Size Dependent ◽  
Dependent Behavior

Size dependent behavior of Fe3O4crystals during electrochemical (de)lithiation: an in situ X-ray diffraction, ex situ X-ray absorption spectroscopy, transmission electron microscopy and theoretical investigation

2017 ◽  
Vol 19 (31) ◽  
pp. 20867-20880 ◽  
Author(s):  
David C. Bock ◽  
Christopher J. Pelliccione ◽  
Wei Zhang ◽  
Janis Timoshenko ◽  
K. W. Knehr ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Structural Changes ◽  
Ex Situ ◽  
X Ray Diffraction ◽  
X Ray ◽  
Size Dependent ◽  
Transmission Electron ◽  
Dependent Behavior ◽  
X Ray Absorption

Crystal and atomic structural changes of Fe3O4upon electrochemical (de)lithiation were determined.

scholarly journals Theoretical Investigation on Structure-Property Relationship of Asymmetric Clusters (CH3FBN3)n (n = 1– 6)

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Deng-Xue Ma ◽  
Yao-Yao Wei ◽  
Yun-Zhi Li ◽  
Guo-Kui Liu ◽  
Qi-Ying Xia
Keyword(s):  
Thermodynamic Properties ◽  
Density Functional ◽  
Dft Method ◽  
Energy Difference ◽  
Structure Property ◽  
Functional Theory ◽  
Size Dependent ◽  
Stable Clusters ◽  
Chemical Inertness ◽  
Relationship Of

The structural, relative stability, electronic, IR vibrational, and thermodynamic properties of asymmetric clusters (CH3FBN3)n (n = 1–6) are systematically investigated using density functional theory (DFT) method. Results show that clusters (CH3FBN3)n (n = 2–6) form a cyclic structure with a B atom and a Nα atom binding together. Five main characteristic regions are observed and assigned for the calculated IR spectra. The size-dependent second-order energy difference shows that clusters (CH3FBN3)3 and (CH3FBN3)5 have relatively higher stability and enhanced chemical inertness compared with the neighboring clusters. These two clusters may serve as the cluster-assembled materials. The variations of thermodynamic properties with temperature T or cluster size n are analyzed, respectively. Based on enthalpies in the range of 200–800 K, the formations of the most stable clusters (CH3FBN3)n (n = 2–6) from monomer are thermodynamically favorable. These data are helpful to design and synthesize other asymmetric boron azides.

Dependence of Tetrahedral Bond Lengths on the Surface Passivation and Stacking-Fault Density of CdSe Nanocrystals

2019 ◽  
Vol 57 ◽  
pp. 58-67
Author(s):  
Pin Jiun Wu ◽  
Yuri P. Stetsko ◽  
Meng Ting Hsieh
Keyword(s):  
Surface Passivation ◽  
Surface Effect ◽  
Stacking Faults ◽  
Expansion Ratio ◽  
Cdse Nanocrystals ◽  
Size Dependent ◽  
Dependent Behavior ◽  
Tetrahedral Bond ◽  
Organic Capping ◽  
Capping Ligands

We have investigated the surface effect of colloidally prepared CdSe nanocrystals (NCs) with the size range of 23-40 Å on their structural properties by changing the organic capping ligands. The TOPO/HDA-passivated NCs reveal a size-dependent behavior involving an elongated axial bondR(1)of an atomic tetrahedron and a shrunken equatorial bondsR(2). After treatment of the NCs with pyridine, the bond lengthR(1)decreases significantly whereasR(2)remains unchanged relative to the TOPO/HDA-passivated NCs, suggesting that a tensile stress along the [001] direction is contributed from the surface modification. In addition, we find that the expansion ratio of the pyridine-treated NCs along the c axis depends strongly on the density of stacking faults, which provides an evidence for the relaxation of atomic positions near the interface of stacking faults.

scholarly journals Viscoelastic and poroelastic mechanical characterization of hydrated gels

2009 ◽  
Vol 24 (3) ◽  
pp. 973-979 ◽  
Author(s):  
Matteo Galli ◽  
Kerstyn S.C. Comley ◽  
Tamaryn A.V. Shean ◽  
Michelle L. Oyen
Keyword(s):  
Elastic Modulus ◽  
Mechanical Behavior ◽  
Mechanical Characterization ◽  
Element Model ◽  
Mechanical Analysis ◽  
Intrinsic Permeability ◽  
Unconfined Compression ◽  
Future Studies ◽  
Dependent Behavior

Measurement of the mechanical behavior of hydrated gels is challenging due to a relatively small elastic modulus and dominant time-dependence compared with traditional engineering materials. Here polyacrylamide gel materials are examined using different techniques (indentation, unconfined compression, dynamic mechanical analysis) at different length-scales and considering both viscoelastic and poroelastic mechanical frameworks. Elastic modulus values were similar for nanoindentation and microindentation, but both indentation techniques overestimated elastic modulus values compared to homogeneous loading techniques. Hydraulic and intrinsic permeability values from microindentation tests, deconvoluted using a poroelastic finite element model, were consistent with literature values for gels of the same composition. Although elastic modulus values were comparable for viscoelastic and poroelastic analyses, time-dependent behavior was length-scale dependent, supporting the use of a poroelastic, instead of a viscoelastic, framework for future studies of gel mechanical behavior under indentation.

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