The Temperature-Dependent Ideal Shear Strength of Solid Single Crystals

2018 ◽  
Vol 85 (3) ◽  
Author(s):  
Tianbao Cheng ◽  
Daining Fang ◽  
Yazheng Yang
Keyword(s):  
Shear Strength ◽  
Theoretical Model ◽  
Melting Point ◽  
Single Crystals ◽  
Elevated Temperatures ◽  
Absolute Zero ◽  
Temperature Dependent ◽  
Temperature Changes ◽  
First Time ◽  
The Ideal

Knowledge of the ideal shear strength of solid single crystals is of fundamental importance. However, it is very hard to determine this quantity at finite temperatures. In this work, a theoretical model for the temperature-dependent ideal shear strength of solid single crystals is established in the view of energy. To test the drawn model, the ideal shear properties of Al, Cu, and Ni single crystals are calculated and compared with that existing in the literature. The study shows that the ideal shear strength first remains approximately constant and then decreases almost linearly as temperature changes from absolute zero to melting point. As an example of application, the “brittleness parameter” of solids at elevated temperatures is quantitatively characterized for the first time.

scholarly journals Dielectric, Thermal and FTIR Studies of Cobalt Doped Magnesium Hydrogen Maleate Hexahydrate Single Crystals

2011 ◽  
Vol 8 (1) ◽  
pp. 91-96
Author(s):  
B. Rajagopal ◽  
M. V. Ramana ◽  
A. V. Sarma
Keyword(s):  
Activation Energy ◽  
Dielectric Constant ◽  
Dielectric Properties ◽  
Melting Point ◽  
Transition Metal ◽  
Single Crystals ◽  
Loss Tangent ◽  
Transition Metal Ions ◽  
Ftir Studies ◽  
First Time

Present work reports the dielectric, thermal and FTIR studies of Co2+: MHMH single crystal for the first time. The influence of addition of transition metal ions on the dielectric properties, like dielectric constant, loss tangent,a.c. conductivity and activation energy of these crystals was discussed. FTIR studies confirm the presence of carboxylate ions. The melting point of the sample and final product after decomposition are studied using TG/DTA.

Post Metallization Annealing Characterization of Interface Properties of High-κ Dielectrics Stack on Silicon Carbide

2008 ◽  
Vol 600-603 ◽  
pp. 771-774 ◽  
Author(s):  
Ming Hung Weng ◽  
Rajat Mahapatra ◽  
Nicolas G. Wright ◽  
Alton B. Horsfall
Keyword(s):  
Elevated Temperatures ◽  
Gate Dielectric ◽  
Flat Band ◽  
Interface Properties ◽  
Temperature Dependent ◽  
Oxide Charge ◽  
Before And After ◽  
Mis Capacitors ◽  
The Ideal

The interface properties of TiO2/SiO2/SiC metal-insulator-semiconductor (MIS) capacitors were investigated by C-V and G-V measurements over a range of frequencies between 10 kHz and 1 MHz from room temperature up to 500°C. Ledges from multiple traps were observed during high frequency (1 MHz) sweeps from inversion to accumulation during measurements at elevated temperatures. The high measuring temperature resulted in the annealing of the sample, where the existence of trap ledges was observed to be temperature dependent. For n-type substrate negative Qf causes the shift of the C-V curve to more negative gate bias with respect to the ideal C-V curve. These fixed oxide charge is substantially reduced after post metallization annealing (PMA). We report the flat band voltage, detail in reducing fixed oxide charge and temperature dependence of density of interface traps before and after annealing of TiO2 high-κ gate dielectric stacks on a 4H-SiC based device.

scholarly journals Direct atomistic simulation of brittle-to-ductile transition in silicon single crystals

2010 ◽  
Vol 1272 ◽  
Author(s):  
Dipanjan Sen ◽  
Alan Cohen ◽  
Aidan P. Thompson ◽  
Adri Van Duin ◽  
William A. Goddard III ◽  
...  
Keyword(s):  
Single Crystals ◽  
Atomistic Simulation ◽  
Large Scale ◽  
Elevated Temperatures ◽  
Experimental Studies ◽  
Crack Tip ◽  
Threshold Value ◽  
Atomic Scale ◽  
Brittle To Ductile Transition ◽  
First Time

AbstractSilicon is an important material not only for semiconductor applications, but also for the development of novel bioinspired and biomimicking materials and structures or drug delivery systems in the context of nanomedicine. For these applications, a thorough understanding of the fracture behavior of the material is critical. In this paper we address this issue by investigating a fundamental issue of the mechanical properties of silicon, its behavior under extreme mechanical loading. Earlier experimental work has shown that at low temperatures, silicon is a brittle material that fractures catastrophically like glass once the applied load exceeds a threshold value. At elevated temperatures, however, the behavior of silicon is ductile. This brittle-to-ductile transition (BDT) has been observed in many experimental studies of single crystals of silicon. However, the mechanisms that lead to this change in behavior remain questionable, and the atomic-scale phenomena are unknown. Here we report for the first time the direct atomistic simulation of the nucleation of dislocations from a crack tip in silicon only due to an increase of the temperature, using large-scale atomistic simulation with the first principles based ReaxFF force field. By raising the temperature in a computational experiment with otherwise identical boundary conditions, we show that the material response changes from brittle cracking to emission of a dislocation at the crack tip, representing evidence for a potential mechanisms of dislocation mediated ductility in silicon.

Modeling of Temperature-Dependent Hardness for Pure FCC and HCP Metals

2020 ◽  
Vol 12 (02) ◽  
pp. 2050022
Author(s):  
Niandong Xu ◽  
Weiguo Li ◽  
Jianzuo Ma ◽  
Yong Deng ◽  
Haibo Kou ◽  
...  
Keyword(s):  
Theoretical Model ◽  
Melting Point ◽  
Present Model ◽  
Experimental Results ◽  
Effect Of Temperature ◽  
Temperature Dependent ◽  
Different Temperatures ◽  
Pure Metals ◽  
Experimental Values ◽  
Hardness Values

In this study, a theoretical model is developed to characterize the quantitative effect of temperature on the hardness of pure FCC and HCP metals. The model is verified by comparison with the available experimental results of Cu, Al, Zn, Mg, Be, Zr, Ni, Ir, Rh, and Ti at different temperatures. Compared with the widely quoted Westbrook model and Ito–Shishokin model which need piecewise fitting to describe experimental values, the present model merely needs two hardness values at different temperatures to predict the experimental results, reducing reliance on conducting lots of experiments. This work provides a convenient method to predict temperature-dependent hardness of pure metals, and it is worth noting that it can be applied to a wide temperature range from absolute zero to melting point.

scholarly journals Thermodynamic and Kinetic Characteristics of Variations in Shapes of Ridges Formed on {100} Lithium Fluoride Surfaces

1991 ◽  
Vol 238 ◽  
Author(s):  
J. W. Bullard ◽  
A. M. Glaeser ◽  
Alan W. Searcy
Keyword(s):  
Theoretical Model ◽  
Melting Point ◽  
Single Crystals ◽  
Surface Diffusion ◽  
Lithium Fluoride ◽  
Kinetic Characteristics ◽  
Surface Sites ◽  
Diffusion Controlled ◽  
Shape Changes

ABSTRACTChannels with widths in the range from 5 μm to 25 μm were formed in {100} surfaces of LiF single crystals by a photolithographic technique. Specimens annealed at or above 0.90 Tm, where Tm is the melting point, and then quenched showed die channels and the ridges between them develop rounded profiles. Evolution of these profiles was evaluated for the various channel widths and for interchannel ridge spacings of 5 to 100 μm in terms of: a) an accepted theoretical model for a surface diffusion controlled process, and b) a model which assumes that shape changes depend only on the relative energies of attachment of atoms in surface sites with various surface curvatures. Either model is consistent with the experimental observations to within the reproducibility in measurements.

Modeling of the temperature-dependent ideal shear strength of solid single crystals

2018 ◽  
Vol 93 ◽  
pp. 299-302 ◽  
Author(s):  
Tianbao Cheng ◽  
Daining Fang ◽  
Yazheng Yang
Keyword(s):  
Shear Strength ◽  
Single Crystals ◽  
Temperature Dependent

Effect of the alloying element on the temperature-dependent ideal shear strength of γ′-Ni3Al

RSC Advances ◽  
2016 ◽  
Vol 6 (25) ◽  
pp. 20551-20558 ◽  
Author(s):  
Xiaoxia Wu ◽  
Chongyu Wang
Keyword(s):  
Density Functional Theory ◽  
Shear Strength ◽  
First Principles ◽  
Finite Temperature ◽  
Density Functional ◽  
Alloying Element ◽  
Temperature Dependent ◽  
Functional Theory ◽  
The Ideal

The ideal shear strength of a doped γ′-Ni3Al phase at finite temperature was predicted from a first principles approach based on density functional theory in combination with quasiharmonic and quasistatic approximations.

Temperature Dependent Characterization of Bipolar Injection Field-Effect-Transistors (BiFET) for Determining the Short-Circuit-Capability

2015 ◽  
Vol 821-823 ◽  
pp. 806-809
Author(s):  
Andreas Hürner ◽  
Tobias Erlbacher ◽  
Heinz Mitlehner ◽  
Anton J. Bauer ◽  
Lothar Frey
Keyword(s):  
Field Effect ◽  
Elevated Temperatures ◽  
Field Effect Transistors ◽  
Short Circuit ◽  
Junction Temperature ◽  
Electrical Performance ◽  
Saturation Current ◽  
Temperature Dependent ◽  
First Time

In this study, the electrical performance of Bipolar-Injection Field-Effect-Transistors (BiFET) in dependence on the junction temperature is presented for the first time. Based on these results, the short circuit capability of the BiFET is discussed. Thereby, the saturation current is estimated to be approximately 150mA at 300K and it increases by a factor of 5 by rising the temperature up to 450K as analyzed in this study. Furthermore, the reduction of the gate-voltage window of the BiFET at elevated temperatures is comparable to unipolar JFETs, and indicates a very good controllability over a wide temperature range. Finally, numerical simulations demonstrate the potential to improve the electrical performance of the BiFET drastically by adjusting the doping concentration in the control region and increasing the ambipolar lifetime in the p-doped drift layer without influencing the dependency on the junction temperature.

scholarly journals Temperature-dependent optical phonon behaviour of a spinel Zn2TiO4 single crystal grown by the optical floating zone method in argon atmosphere

RSC Advances ◽  
2017 ◽  
Vol 7 (56) ◽  
pp. 35477-35481 ◽  
Author(s):  
Liang Li ◽  
Shuohui Gao ◽  
Tian Cui ◽  
Benxian Li ◽  
Qiang Zhou ◽  
...  
Keyword(s):  
Single Crystal ◽  
Single Crystals ◽  
Raman Spectra ◽  
Optical Phonon ◽  
Argon Atmosphere ◽  
Floating Zone ◽  
Temperature Dependent ◽  
Zone Method ◽  
Floating Zone Method ◽  
First Time

The spinel Zn2TiO4 single crystals were grown via optical floating zone technology in an argon atmosphere for the first time. And temperature dependent Raman spectra were presented.

scholarly journals Development of a Novel Ni-Based Multi-principal Element Alloy Filler Metal, Using an Alternative Melting Point Depressant

2021 ◽  
Author(s):  
Liam Hardwick ◽  
Pat Rodgers ◽  
Ed Pickering ◽  
Russell Goodall
Keyword(s):  
Shear Strength ◽  
Melting Point ◽  
Thermodynamic Parameters ◽  
Elevated Temperatures ◽  
Filler Metal ◽  
Hold Time ◽  
Nickel Superalloy ◽  
High Entropy Alloy ◽  
Principal Element ◽  
Thermo Calc Software

AbstractBrazing is a crucial joining technology in industries where nickel-superalloy components must be joined. Nickel-based brazing filler metals are extensively employed, possessing excellent mechanical properties, corrosion resistance, and retained strength at elevated temperatures. To function as a filler metal, the alloy melting point must be reduced to below that of the materials being joined, but the addition of melting point depressants (MPDs) such as boron, silicon, and phosphorus can, however, lead to the formation of brittle intermetallics, potentially compromising the joint performance. In the present work, a novel multi-principal element brazing alloy (in the style of a high entropy alloy), utilizing Ge as an alternative MPD along with a reduced B addition, is investigated. The design process considered binary phase diagrams and predictions based on Thermo-Calc software and empirical thermodynamic parameters. The alloy was used to vacuum braze nickel-superalloy Inconel-718, and microstructural and mechanical investigations are reported. The maximum shear strength achieved was 297 MPa with a brazing temperature of 1100 °C and 60-minute hold time, with isothermal solidification completed. Shear strength was only slightly reduced with increased joint width. Assessments are made of the ability to accurately predict properties of multi-principle element alloys using Thermo-Calc software and empirical thermodynamic parameters.

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