Atomistic Determination of Continuum Mechanical Properties of Ion-Bombarded Silicon

2005 ◽  
Vol 127 (4) ◽  
pp. 457-461 ◽  
Author(s):  
N. Kalyanasundaram ◽  
J. B. Freund ◽  
H. T. Johnson
Keyword(s):  
Free Energy ◽  
Surface Free Energy ◽  
Cross Sections ◽  
Interatomic Potential ◽  
Crystalline Silicon ◽  
Strain Curve ◽  
Free Energy Density ◽  
Dynamics Simulation ◽  
Interatomic Potentials ◽  
Stress Strain

Highly disordered, ion-processed silicon is studied using a molecular dynamics simulation with empirical interatomic potentials. The surface free energy density, stress-strain relations, and continuum surface features of silicon, bombarded in the simulations to relatively high fluence by medium energy argon ions, are computed statistically by preparing multiple randomized ion-bombarded specimens. The surface-free energy per unit area for the ion-bombarded silicon is about 1.76J∕m2, much lower than the 2.35J∕m2 corresponding to a (001) unrelaxed, crystalline silicon surface. A stress-strain curve is obtained computationally by performing a constant strain test on the ion-bombarded specimens and by calculating stresses from the interatomic forces acting across different cross sections in the sample. The resulting tensile elastic modulus of the material, while slightly elevated due to the prominence of the free surface in the thin layer, is in good agreement with available experimental data. The surface is characterized using an interatomic potential-based C2 continuous sampling method.

Influence of FRP-to-Concrete Gap Effect on Axial Strains of FRP-Confined Concrete Columns

2015 ◽  
Vol 1119 ◽  
pp. 760-765
Author(s):  
Thomas Vincent ◽  
Togay Ozbakkloglu
Keyword(s):  
Cross Sections ◽  
Axial Stress ◽  
Axial Strain ◽  
Strain Curve ◽  
Shrinkage Strain ◽  
Confined Concrete ◽  
Gap Effect ◽  
Stress Strain ◽  
Concrete Shrinkage ◽  
Concrete Interface

This paper reports on an experimental investigation on the influence of FRP-to-concrete interface gap, caused by concrete shrinkage, on axial compressive behavior of concrete-filled FRP tube (CFFT) columns. A total of 12 aramid FRP (AFRP)-confined concrete specimens with circular cross-sections were manufactured. 3 of these specimens were instrumented to monitor long term shrinkage strain development and the remaining 9 were tested under monotonic axial compression. The influence of concrete shrinkage was examined by applying a gap of up to 0.06 mm thickness at the FRP-to-concrete interface, simulating 800 microstrain of shrinkage in the radial direction. Axial strain recordings were compared on specimens instrumented with two different measurement methods: full-and mid-height linear variable displacement transformers (LVDTs). Results of the experimental study indicate that the influence of interface gap on stress-strain behavior is significant, with an increase in interface gap resulting in a decrease and increase in the compressive strength and ultimate axial strain, respectively. It was also observed that an increase in interface gap leads to a slight loss in axial stress at the transition region of the stress-strain curve. Finally, it is found that an increase in the interface gap results in a significant decrease in the ratio of the ultimate axial strains obtained from mid-section and full-height LVDTs.

Facetting Growth of Low Temperature Polycrystalline Silicon by Ecr-Cvd with Hydrogen Dilution Method

1998 ◽  
Vol 507 ◽  
Author(s):  
H.-L. Hsiao ◽  
A.-B. Yang ◽  
H.-L. Hwang
Keyword(s):  
Free Energy ◽  
Surface Free Energy ◽  
Liquid Layer ◽  
Polycrystalline Silicon ◽  
Diffusion Processes ◽  
Crystalline Silicon ◽  
Dark Field ◽  
Dilution Method ◽  
Hydrogen Dilution ◽  
Quasi Liquid Layer

ABSTRACTThe polycrystalline silicon films with grain size of 1 μ m have been successful deposited on glass substrates using ECR-CVD with hydrogen dilution method at 250°C and without any thermal annealing. The deposited poly-Si films exhibit severe “hill and valley” surface roughness and facets structures. The X-ray diffraction spectra show that the dominant crystal textures are <220> and <111> orientations. The leaf-like two-fold symmetrical grain shape and the corresponding crystallography diffraction pattern indicate the orientation of largest grain is <110>. The dark field TEM image also shows the upside octahedral facets shape. Considering the effect of orientation on deposition rate and symmetry, the possible facets orientation should be <311>. Moreover, the grain sizes of poly-Si thin films deposited on bare Si wafer and on oxidized Si substrates or glass are almost the same. The facetting and textural structures can be attributed to the surface free energy change induced by the adatom quasi-liquid layer which is composed by the radicals and energetic atomic hydrogen. This adatom quasi-liquid layer would dramatically change the surface diffusion processes of adsorbed precursors and surface free energy of low index planes. Therefore, the SiHn radicals and SinHm molecular precursors with enhanced surface mobility would relax to their stable sites and form the crystalline silicon clusters.

COMPUTER SIMULATION OF EPITAXIAL GROWTH OF SILICON ON Si (001) SURFACE

2002 ◽  
Vol 16 (01n02) ◽  
pp. 227-232 ◽  
Author(s):  
M. H. LIANG ◽  
X. XIE ◽  
S. LI
Keyword(s):  
Molecular Dynamics ◽  
Computer Simulation ◽  
Epitaxial Growth ◽  
Interatomic Potential ◽  
Simulation Method ◽  
Growth Direction ◽  
Dynamics Simulation ◽  
Interatomic Potentials ◽  
Weber Potential ◽  
Deposition Conditions

Epitaxial growth of silicon on Si (001) surface has been studied with interatomic potential based molecular dynamics simulation method. Three silicon interatomic potentials developed separately by Stillinger-Weber, Tersoff, and Bazant-Kaxiras were used. Energetic beam of 8 eV, substrate temperature of 500K and deposition rate of 1.15 ps/atom were used as the deposition conditions. Morphologies of the growth were obtained and densities in the growth direction analyzed. Epitaxial growth under the deposition conditions imposed was found possible only using the Stillinger-Weber potential. Disordered growths of differing degree were obtained using the Bazant-Kaxiras and Tersoff potentials. The disordered growth may be attributed to the existence of an epitaxial transition temperature higher than 500K that these potentials might have.

Surface free energy of carbon fibers with circular and non-circular cross sections coated with silicon carbide

Carbon ◽  
1995 ◽  
Vol 33 (6) ◽  
pp. 779-782 ◽  
Author(s):  
Gerhard Emig ◽  
Nadja Popovska ◽  
Dan D. Edie ◽  
Bo-Sung Rhee
Keyword(s):  
Silicon Carbide ◽  
Free Energy ◽  
Surface Free Energy ◽  
Carbon Fibers ◽  
Cross Sections

A continuum state variable theory to model the size-dependent surface energy of nanostructures

2015 ◽  
Vol 17 (38) ◽  
pp. 25494-25498 ◽  
Author(s):  
Mostafa Jamshidian ◽  
Prakash Thamburaja ◽  
Timon Rabczuk
Keyword(s):  
Free Energy ◽  
Energy Density ◽  
Surface Energy ◽  
Surface Free Energy ◽  
Free Energy Density ◽  
Continuum State ◽  
Variable Theory ◽  
Size Dependent ◽  
State Variable ◽  
Excess Surface

We propose a continuum-based state variable theory to quantify the excess surface free energy density throughout a nanostructure.

Bending of Beams with Nonlinear Material Characteristics

1980 ◽  
Vol 102 (4) ◽  
pp. 776-780 ◽  
Author(s):  
G. Szuladzinski
Keyword(s):  
Cross Sections ◽  
Elevated Temperatures ◽  
Strain Curve ◽  
Bending Moment ◽  
Nonlinear Material ◽  
Stress Strain ◽  
Slope Change ◽  
Deflection Analysis ◽  
Manual Methods ◽  
Bending Of Beams

When an expression is known for the curvature of a beam as a function of a bending moment, it is a simple matter to determine the deflected shape. It is a bigger problem to obtain such an explicit expression using a realistic stress-strain curve. This paper begins with a Ramberg-Osgood type of stress-strain formula, that is characterized by a continuous slope change typical of metals in elevated temperatures. A moment-curvature equation of a similar form is then developed and its accuracy is verified for several basic cross-sections. The advantage of this approach is to improve the accuracy and efficiency of deflection analysis compared with the existing manual methods.

scholarly journals Influence of Anodizing Parameters on Surface Morphology and Surface-Free Energy of Al2O3 Layers Produced on EN AW-5251 Alloy

Materials ◽  
2019 ◽  
Vol 12 (5) ◽  
pp. 695 ◽  
Author(s):  
Marek Bara ◽  
Mateusz Niedźwiedź ◽  
Władysław Skoneczny
Keyword(s):  
Free Energy ◽  
Surface Free Energy ◽  
Cross Sections ◽  
Contact Angles ◽  
Oxide Layers ◽  
X Ray ◽  
Energy Value ◽  
Average Value ◽  
Energetic State ◽  
Scanning Electron

The paper presents the influence of the surface anodizing parameters of the aluminum alloy EN AW-5251 on the physicochemical properties of the oxide layers produced on it. Micrographs of the surface of the oxide layers were taken using a scanning electron microscope (SEM). The chemical composition of cross-sections from the oxide layers was studied using energy dispersive spectroscopy (EDS). The phase structure of the Al2O3 layers was determined by the pattern method using X-ray diffractometry (XRD). The nanomorphology of the oxide layers were analyzed based on microscopic photographs using the ImageJ 1.50i program. The energetic state of the layers was based on the surface-free energy (SFE), calculated from measurements of contact angles using the Owens-Wendt method. The highest surface-free energy value (49.12 mJ/m2) was recorded for the sample produced at 293 K, 3 A/dm2, in 60 min. The lowest surface-free energy value (31.36 mJ/m2) was recorded for the sample produced at 283 K, 1 A/dm2, in 20 min (the only hydrophobic layer). The highest average value nanopore area (2358.7 nm2) was recorded for the sample produced at 303 K, 4 A/dm2, in 45 min. The lowest average value nanopore area (183 nm2) was recorded for the sample produced at 313 K, 1 A/dm2, in 20 min.

Sign in / Sign up

Export Citation Format

Share Document