scholarly journals Atomic Simulations of Packing Structures, Local Stress and Mechanical Properties for One Silicon Lattice with Single Vacancy on Heating

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3127
Author(s):  
Feng Dai ◽  
Dandan Zhao ◽  
Lin Zhang
Keyword(s):  
Mechanical Properties ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Silicon Crystal ◽  
Local Stress ◽  
Uniaxial Tensile ◽  
Single Vacancy ◽  
Vacancy Defects ◽  
Silicon Lattice ◽  
Atomic Simulations

The effect of vacancy defects on the structure and mechanical properties of semiconductor silicon materials is of great significance to the development of novel microelectronic materials and the processes of semiconductor sensors. In this paper, molecular dynamics is used to simulate the atomic packing structure, local stress evolution and mechanical properties of a perfect lattice and silicon crystal with a single vacancy defect on heating. In addition, their influences on the change in Young’s modulus are also analyzed. The atomic simulations show that in the lower temperature range, the existence of vacancy defects reduces the Young’s modulus of the silicon lattice. With the increase in temperature, the local stress distribution of the atoms in the lattice changes due to the migration of the vacancy. At high temperatures, the Young’s modulus of the silicon lattice changes in anisotropic patterns. For the lattice with the vacancy, when the temperature is higher than 1500 K, the number and degree of distortion in the lattice increase significantly, the obvious single vacancy and its adjacent atoms contracting inward structure disappears and the defects in the lattice present complex patterns. By applying uniaxial tensile force, it can be found that the temperature has a significant effect on the elasticity–plasticity behaviors of the Si lattice with the vacancy.

Cellulose Whiskers Micro-Fibers Effect in the Mechanical Proprieties of PP and PLA Composites Fibers Obtained by Spinning Process

2011 ◽  
Vol 146 ◽  
pp. 12-26 ◽  
Author(s):  
A. Gherissi ◽  
R.Ben Cheikh ◽  
E. Dévaux ◽  
Fethi Abbassi
Keyword(s):  
Mechanical Properties ◽  
Young’S Modulus ◽  
Volume Fraction ◽  
Young's Modulus ◽  
Tensile Tests ◽  
Advanced Materials ◽  
Uniaxial Tensile ◽  
Failure Resistance ◽  
Cellulose Whiskers ◽  
Limit Strength

In this study, we present the manufacturing process of two new composites materials in the form of long fibers of polylactic-acid (PLA) or polypropylene (PP), reinforced by cellulose whiskers micro-fibers loads. In order to evaluate the mechanical properties of these advanced materials, a several uniaxial tensile tests were carried out. The PP and the PLA have initially been spinning without the addition of cellulose whiskers micro-fibers. In order to study the effects of cellulose whiskers micro-fibers reinforcements in the Mechanical behavior of the PLA and PP filaments, we determinate the proprieties of these advanced material from the tensile results. For the PP composite filaments material case, the whiskers reinforcement increases Young's modulus and failure resistance, but it reduces the limit strength failure. For the PLA composites the addition of 1% wt of cellulose whiskers from the total volume fraction of the material, increase the Young’s modulus more than 50% and a decrease of the failure resistance and the limit strength of composite. The obtained composites fibers are very rigid and brittle. What follows, that the addition of cellulose whiskers micro fibers in PP matrix, provides mechanical properties more convenient compared to the PLA matrix.

Focused Ion Beam Induced Surface Damage Effect on the Mechanical Properties of Silicon Nanowires

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
Tatsuya Fujii ◽  
Takahiro Namazu ◽  
Koichi Sudoh ◽  
Shouichi Sakakihara ◽  
Shozo Inoue
Keyword(s):  
Mechanical Properties ◽  
Young’S Modulus ◽  
Focused Ion Beam ◽  
Young's Modulus ◽  
Ion Beam ◽  
Surface Damage ◽  
Ambient Air ◽  
Film Deposition ◽  
Displacement Sensor ◽  
Uniaxial Tensile

In this paper, the effect of surface damage induced by focused ion beam (FIB) fabrication on the mechanical properties of silicon (Si) nanowires (NWs) was investigated. Uniaxial tensile testing of the NWs was performed using a reusable on-chip tensile test device with 1000 pairs of comb structures working as an electrostatic force actuator, a capacitive displacement sensor, and a force sensor. Si NWs were made from silicon-on-nothing (SON) membranes that were produced by deep reactive ion etching hole fabrication and ultrahigh vacuum annealing. Micro probe manipulation and film deposition functions in a FIB system were used to bond SON membranes to the device's sample stage and then to directly fabricate Si NWs on the device. All the NWs showed brittle fracture in ambient air. The Young's modulus of 57 nm-wide NW was 107.4 GPa, which was increased to 144.2 GPa with increasing the width to 221 nm. The fracture strength ranged from 3.9 GPa to 7.3 GPa. By assuming the thickness of FIB-induced damage layer, the Young's modulus of the layer was estimated to be 96.2 GPa, which was in good agreement with the literature value for amorphous Si.

Uncertainty quantification and prediction for mechanical properties of graphene aerogels via gaussian process metamodels

Nano Futures ◽  
2021 ◽  
Author(s):  
Bowen Zheng ◽  
Zeyu Zheng ◽  
Grace Gu
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Ultimate Tensile Strength ◽  
Gaussian Process ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Dynamics Simulation ◽  
Uniaxial Tensile ◽  
Graphene Aerogel ◽  
Graphene Aerogels

Abstract Graphene aerogels, a special class of 3D graphene assemblies, are well known for their exceptional combination of high strength, lightweightness, and high porosity. However, due to microstructural randomness, the mechanical properties of graphene aerogels are also highly stochastic, an issue that has been observed but insufficiently addressed. In this work, we develop Gaussian process metamodels to not only predict important mechanical properties of graphene aerogels but also quantify their uncertainties. Using the molecular dynamics simulation technique, graphene aerogels are assembled from randomly distributed graphene flakes and spherical inclusions, and are subsequently subject to a quasi-static uniaxial tensile load to deduce mechanical properties. Results show that given the same density, mechanical properties such as the Young’s modulus and the ultimate tensile strength can vary substantially. Treating density, Young’s modulus, and ultimate tensile strength as functions of the inclusion size, and using the simulated graphene aerogel results as training data, we build Gaussian process metamodels that can efficiently predict the properties of unseen graphene aerogels. In addition, statistically valid confidence intervals centered around the predictions are established. This metamodel approach is particularly beneficial when the data acquisition requires expensive experiments or computation, which is the case for graphene aerogel simulations. The present research quantifies the uncertain mechanical properties of graphene aerogels, which may shed light on the statistical analysis of novel nanomaterials of a broad variety.

Recycled HDPE-tetrapack composites. Isothermal crystallization, light scattering and mechanical properties

2012 ◽  
Vol 1485 ◽  
pp. 77-82 ◽  
Author(s):  
A Parada-Soria ◽  
HF Yao ◽  
B Alvarado-Tenorio ◽  
L Sanchez-Cadena ◽  
A Romo-Uribe
Keyword(s):  
Mechanical Properties ◽  
Light Scattering ◽  
Young’S Modulus ◽  
Tensile Deformation ◽  
Young's Modulus ◽  
Ultimate Tensile Stress ◽  
Uniaxial Tensile ◽  
Scanning Calorimetry ◽  
Slow Cooling ◽  
The Matrix

ABSTRACTIn this research the thermal and mechanical properties of composites based on recycled high-density polyethylene (HDPE) and recycled Tetrapak have been investigated. The matrix and filler are recovered from landfills. Multicolor HDPE mixtures, with varying concentration of tetrapack flakes, are hot pressed, as well as single color HDPE flakes. Previous studies determine that the nature of the pigment (organics vs. inorganics) strongly influence the mechanical behavior of multicolor HDPE-tetrapack composites. Thus, this research focuses on single color HDPE hot pressed plaques. The kinetics of crystallization under isothermal conditions is determined by differential scanning calorimetry (DSC). The results show that the crystallization kinetics obeys the Avrami theory, and that the Avrami exponent is 1, irrespective of the pigment in use. Small-angle light scattering is applied to investigate the internal structure of the pigmented HDPE. SALS patterns show that the samples exhibited oriented morphologies. However, after melting and slow cooling under pressure the samples exhibit an isotropic morphology. This is confirmed by polarized optical microscopy. Mechanical properties such as Young’s modulus, yield stress and ultimate tensile stress are obtained under uniaxial tensile deformation at room temperature. For the single color HDPE plaques the Young’s modulus is reduced (after melting), suggesting that the anisotropic molecular chains contribute to the higher value of Young’s modulus.

The Uniaxial Tension Properties of Silver Nanorod by Molecular Dynamics Simulations

2007 ◽  
Author(s):  
Li Chen ◽  
Heng Liu ◽  
Lie Yu
Keyword(s):  
Molecular Dynamics ◽  
Young’S Modulus ◽  
Tensile Deformation ◽  
Young's Modulus ◽  
Ultimate Stress ◽  
Uniaxial Tensile ◽  
Vacancy Defects ◽  
Tension Properties ◽  
Dynamics Simulations ◽  
Vacancy Density

Using Sutton-Chen many-body potential, the mechanical characteristics of silver nanorod subjected to 001 uniaxial tensile strain are simulated with molecular dynamics. The results indicate that the tensile deformation process consists of an elastic and a plastic periods. The atomic configurations change little in elastic period but change obviously in plastic period. The changes of atomic configurations directly determine the corresponding stress-strain relation. The stress increases linearly as strain grows within the process of elastic deformation. The stress fluctuates greatly in plastic period. With detailed analysis, the dislocations and slips of atoms lead to the stress oscillation. The influences of size effects on tension properties are investigated simultaneously. Young’s modulus heightens and the elastic ultimate stress decreases with the increasing global size of nanorod. Both of them approach to that of macroscopic material as the global size increases. At the same time, the tension properties of Silver nanorod with vacancy defects are investigated. When the vacancy density is less than 0.1%, the Young’s modulus of defect crystals are almost same as that of free-defect crystals, but the elastic ultimate stress is less than that of free-defect crystals. The Young’s modulus and elastic ultimate stress and strain are all decrease with the increment of vacancy density.

Numerical modeling of the effects hydration and number of hydrogen bonds on the mechanical properties of the tropocollagen molecule

2020 ◽  
Vol 234 (3) ◽  
pp. 299-306 ◽  
Author(s):  
Marouane El Mouss ◽  
Amna Rekik ◽  
Said Zellagui ◽  
Tarek Merzouki ◽  
Ridha Hambli
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Hydrogen Bonds ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Strain Curve ◽  
Collagen Molecule ◽  
Uniaxial Tensile ◽  
Type I ◽  
Two Parameters

Bone aging involves structural and molecular modifications, especially at the level of type I tropocollagen. This macromolecule shows two main age-related alterations, which are the decrease of both molecular diameter (due to the loss of hydration) and number of hydrogen bonds. In this work, it is proposed to investigate the influence of these two parameters (molecular diameter and number of hydrogen bonds) on the mechanical behavior of tropocollagen using finite element method. To this end, a novel three-dimensional finite element model of collagen molecule accounting for hydrogen bonds was developed. Then, a numerical design of experiments for the diameter of tropocollagen and variations in the number of hydrogen bonds has been established. The mechanical properties (“load–strain” curve and apparent Young’s modulus) of the collagen molecule were obtained by employing the proposed model to uniaxial tensile tests. The parametric study demonstrates that the mechanical properties of tropocollagen are slightly affected by the rate of hydration but considerably affected by variation of the number of hydrogen bonds. Finally, a fitted analytical function was deduced from the above results showing effects of the two parameters (hydration rate and hydrogen bonds) on the apparent Young’s modulus of tropocollagen. This study could be useful to understand the influence of structural age modifications of tropocollagen on the macroscopic mechanical properties of bone.

Mechanical Properties of Porous Titanium Compacts Reinforced by UHMWPE

2007 ◽  
Vol 539-543 ◽  
pp. 1033-1037 ◽  
Author(s):  
Naoyuki Nomura ◽  
Y. Baba ◽  
A. Kawamura ◽  
S. Fujinuma ◽  
Akihiko Chiba ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Young’S Modulus ◽  
Bending Strength ◽  
Young's Modulus ◽  
Local Stress ◽  
Porous Titanium ◽  
Three Point Bending ◽  
Porous Ti ◽  
Ti Powder ◽  
Ultra High Molecular Weight

Porous Ti compacts reinforced by ultra-high molecular weight polyethylene (UHMWPE) were fabricated and their mechanical properties were evaluated. Ti powder atomized by plasma rotating electrode process (PREP) was sintered at temperatures ranging from 1473 K to 1673 K for 7.2 ks in a vacuum. The porous Ti compacts contain the porosity of about 40%, irrespective of the sintering temperature. Porous Ti/UHMWPE composites were successfully fabricated by compressing UHMWPE powder into the porous Ti compacts. The compacts exhibit open pore structure and enables the penetration of UHMWPE into pores in the compacts. Young’s modulus of the composites is higher than that of the porous Ti compacts. The increment in Young’s modulus is not simply explained by the rule of mixture because Young’s modulus of the UHMWPE is approximately 1.3 GPa. Three-point bending strength of the composites is improved, presumably due to the local stress relief by UHMWPE in the vicinity of neck in the composites.

Mechanical properties of FeAlSi powders prepared by mechanical alloying from different initial feedstock materials

2019 ◽  
Vol 107 (2) ◽  
pp. 207 ◽  
Author(s):  
Jaroslav Čech ◽  
Petr Haušild ◽  
Miroslav Karlík ◽  
Veronika Kadlecová ◽  
Jiří Čapek ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Mechanical Alloying ◽  
Young’S Modulus ◽  
Milling Time ◽  
Young's Modulus ◽  
Element Model ◽  
X Ray Diffraction ◽  
X Ray ◽  
Powder Particles ◽  
Complete Homogenization

FeAl20Si20 (wt.%) powders prepared by mechanical alloying from different initial feedstock materials (Fe, Al, Si, FeAl27) were investigated in this study. Scanning electron microscopy, X-ray diffraction and nanoindentation techniques were used to analyze microstructure, phase composition and mechanical properties (hardness and Young’s modulus). Finite element model was developed to account for the decrease in measured values of mechanical properties of powder particles with increasing penetration depth caused by surrounding soft resin used for embedding powder particles. Progressive homogenization of the powders’ microstructure and an increase of hardness and Young’s modulus with milling time were observed and the time for complete homogenization was estimated.

scholarly journals First principles computation of composition dependent elastic constants of omega in titanium alloys: implications on mechanical behavior

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
R. Salloom ◽  
S. A. Mantri ◽  
R. Banerjee ◽  
S. G. Srinivasan
Keyword(s):  
Mechanical Properties ◽  
Young’S Modulus ◽  
First Principles ◽  
Young's Modulus ◽  
Group Vi ◽  
Group V ◽  
Β Phase ◽  
Ti Alloys ◽  
Ω Phase ◽  
Stabilizer Concentration

AbstractFor decades the poor mechanical properties of Ti alloys were attributed to the intrinsic brittleness of the hexagonal ω-phase that has fewer than 5-independent slip systems. We contradict this conventional wisdom by coupling first-principles and cluster expansion calculations with experiments. We show that the elastic properties of the ω-phase can be systematically varied as a function of its composition to enhance both the ductility and strength of the Ti-alloy. Studies with five prototypical β-stabilizer solutes (Nb, Ta, V, Mo, and W) show that increasing β-stabilizer concentration destabilizes the ω-phase, in agreement with experiments. The Young’s modulus of ω-phase also decreased at larger concentration of β-stabilizers. Within the region of ω-phase stability, addition of Nb, Ta, and V (Group-V elements) decreased Young’s modulus more steeply compared to Mo and W (Group-VI elements) additions. The higher values of Young’s modulus of Ti–W and Ti–Mo binaries is related to the stronger stabilization of ω-phase due to the higher number of valence electrons. Density of states (DOS) calculations also revealed a stronger covalent bonding in the ω-phase compared to a metallic bonding in β-phase, and indicate that alloying is a promising route to enhance the ω-phase’s ductility. Overall, the mechanical properties of ω-phase predicted by our calculations agree well with the available experiments. Importantly, our study reveals that ω precipitates are not intrinsically embrittling and detrimental, and that we can create Ti-alloys with both good ductility and strength by tailoring ω precipitates' composition instead of completely eliminating them.

scholarly journals Tailoring a Low Young Modulus for a Beta Titanium Alloy by Combining Severe Plastic Deformation with Solution Treatment

Materials ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3467
Author(s):  
Anna Nocivin ◽  
Doina Raducanu ◽  
Bogdan Vasile ◽  
Corneliu Trisca-Rusu ◽  
Elisabeta Mirela Cojocaru ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Plastic Deformation ◽  
Severe Plastic Deformation ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Solution Treatment ◽  
Young Modulus ◽  
Orthopedic Implants ◽  
Beta Titanium Alloy

The present paper analyzed the microstructural characteristics and the mechanical properties of a Ti–Nb–Zr–Fe–O alloy of β-Ti type obtained by combining severe plastic deformation (SPD), for which the total reduction was of etot = 90%, with two variants of super-transus solution treatment (ST). The objective was to obtain a low Young’s modulus with sufficient high strength in purpose to use the alloy as a biomaterial for orthopedic implants. The microstructure analysis was conducted through X-ray diffraction (XRD), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HRTEM) investigations. The analyzed mechanical properties reveal promising values for yield strength (YS) and ultimate tensile strength (UTS) of about 770 and 1100 MPa, respectively, with a low value of Young’s modulus of about 48–49 GPa. The conclusion is that satisfactory mechanical properties for this type of alloy can be obtained if considering a proper combination of SPD + ST parameters and a suitable content of β-stabilizing alloying elements, especially the Zr/Nb ratio.

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