Nucleations of pressure induced phase transitions in mercury selenide

1977 ◽  
Vol 55 (3) ◽  
pp. 222-226
Author(s):  
B. A. Lombos ◽  
H. M. Mahdaly ◽  
B. C. Pant
Keyword(s):  
Phase Transitions ◽  
Heterogeneous Nucleation ◽  
Direct Relationship ◽  
Activation Volume ◽  
Three Dimensional ◽  
Direct Determination ◽  
Nucleation Theory ◽  
Kinetic Transition ◽  
Mercury Selenide

The resistance discontinuity technique combined with a three-dimensional heterogeneous nucleation theory permitted the direct determination of the rate of pressure induced phase transitions in mercury selenide. A direct relationship between the activation volumes and kinetic transition pressures was found which facilitated the determination of the thermodynamical transition pressure by extrapolating to zero activation volume. At low nucleation concentration, a faster rate of transition is observed.

Submicrometre-resolution polychromatic three-dimensional X-ray microscopy

2012 ◽  
Vol 46 (1) ◽  
pp. 153-164 ◽  
Author(s):  
B. C. Larson ◽  
L. E. Levine
Keyword(s):  
Spatial Resolution ◽  
Elastic Strain ◽  
Strain Tensor ◽  
Three Dimensional ◽  
Direct Determination ◽  
Phase Identification ◽  
Sn Whisker ◽  
X Ray ◽  
Elastic Strain Tensor

The ability to study the structure, microstructure and evolution of materials with increasing spatial resolution is fundamental to achieving a full understanding of the underlying science of materials. Polychromatic three-dimensional X-ray microscopy (3DXM) is a recently developed nondestructive diffraction technique that enables crystallographic phase identification, determination of local crystal orientations, grain morphologies, grain interface types and orientations, and in favorable cases direct determination of the deviatoric elastic strain tensor with submicrometre spatial resolution in all three dimensions. With the added capability of an energy-scanning incident beam monochromator, the determination of absolute lattice parameters is enabled, allowing specification of the complete elastic strain tensor with three-dimensional spatial resolution. The methods associated with 3DXM are described and key applications of 3DXM are discussed, including studies of deformation in single-crystal and polycrystalline metals and semiconductors, indentation deformation, thermal grain growth in polycrystalline aluminium, the metal–insulator transition in nanoplatelet VO2, interface strengths in metal–matrix composites, high-pressure science, Sn whisker growth, and electromigration processes. Finally, the outlook for future developments associated with this technique is described.

Molecular Dynamics Simulation of Nano Cluster-Seed Effects on Heterogeneous Nucleation

2009 ◽  
Author(s):  
Donguk Suh ◽  
Seung-chai Jung ◽  
Woong-sup Yoon
Keyword(s):  
Molecular Dynamics ◽  
Heterogeneous Nucleation ◽  
Three Dimensional ◽  
Seed Mass ◽  
Nucleation Theory ◽  
Dynamics Simulation ◽  
Classical Nucleation Theory ◽  
Supersaturation Ratio ◽  
Order Of Magnitude ◽  
Nano Cluster

A three-dimensional heterogeneous nucleation is simulated by classical molecular dynamics, where the Lennard-Jones gas and solid nano cluster-seed molecules have argon and aluminum properties, respectively. All dimensions of the wall are periodic and a soft core carrier gas within the system controls the temperature rise induced by latent heat of condensation. There are three shapes of cluster-seeds being cube, rod, and sphere, three classes of masses, and the simulation took place under nine supersaturation ratios, making a total of 81 calculations. An analysis of variance was performed under a three-way layout to analyze the cluster-seed and supersaturation ratio effects on the system. For supersaturation ratios above the critical value nucleation rates were evaluated, below growth rates, and overall liquefaction rates were each defined and calculated. Results show that the supersaturation ratio dominantly controls all rates, but seed characteristics are important for the growth of the largest cluster under the critical supersaturation ratio. Overall liquefaction increases subject to an escalation of supersaturation ratio and seed mass. However, the significance of the supersaturation ratio for overall liquefaction suggests that thermal diffusion is more dominant than mass interactions for this system. Homogeneous characteristics are also compared with the heterogeneous system to find that though nucleation may occur for an insufficient supersaturation ratio when a seed is within the system, the addition of a seed does not in fact facilitate the increase in rates of the phenomena at high supersaturation ratios. Finally a comparison with the classical nucleation theory asserts a 3 to 4 order of magnitude difference, which is within the lines of deviation when it comes to theory and molecular simulations.

Molecular Dynamics Simulation of Three-Dimensional Heterogeneous Nucleation

2011 ◽  
Author(s):  
Donguk Suh ◽  
Kenji Yasuoka
Keyword(s):  
Molecular Dynamics ◽  
Heterogeneous Nucleation ◽  
Homogeneous Nucleation ◽  
Three Dimensional ◽  
Nucleation Theory ◽  
Dynamics Simulation ◽  
Classical Nucleation Theory ◽  
Supersaturation Ratio ◽  
Seed Growth ◽  
Thermodynamic Conditions

Nanoparticle growth based on three-dimensional heterogeneous nucleation was simulated by classical molecular dynamics. To collectively observe the effects of the dimension of seeds and thermodynamic conditions, seed size and system supersaturation ratio were the factors that were examined to see if they influenced the nucleation rates. Two stages were found to exist within the system, where the first stage is from the seed growth and the second from homogeneous nucleation. The Yasuoka-Matsumoto method was used to calculate the rates. The homogeneous nucleation characteristics coincided with the classical nucleation theory, but heterogeneous nucleation showed an irregular form, which at the current state cannot not be fully understood. Kinetic analysis was also performed to calculate the critical nucleus size and better understand the seed growth characteristics. All in all, the seed effects were insignificant to the overall nucleation characteristics for this system.

Direct Determination of Angular Velocity Using GPS

2000 ◽  
Vol 53 (2) ◽  
pp. 371-379 ◽  
Author(s):  
Mami Ueno ◽  
Rock Santerre ◽  
Alfred Kleusberg
Keyword(s):  
Angular Velocity ◽  
Three Dimensional ◽  
Direct Determination ◽  
Temporal Difference ◽  
Yaw Rate ◽  
Change Of State ◽  
The Difference ◽  
Comparison Of The Results ◽  
Turn Rate

Controlling a ship in a berthing operation is carried out mainly by the change of state, such as velocity and yaw rate (turn rate), although the value of the change of state is very small at berthing. Very high precision is, therefore, required to determine the velocity and angular velocity. A sensor that has an accuracy of ±0.02°/s (1 σ) is sought for determination of turn rate in a berthing system. Three-dimensional angular velocity can directly be determined, with 2 independent baselines of 3 GPS antennas, using instantaneous Doppler measurements or phase rate (temporal difference of phase) observations. This paper discusses the mathematical model for direct determination of angular velocity using GPS, and the comparison of the results of the angular velocity determination using the Doppler and phase rate. The precision of angular velocity determination is estimated using temporal difference of the attitude sensors (TSS and gyrocompass) on board a hydrographic sounding ship. The RMS values of the difference of yaw rate determination between the two systems were: ±0.16°/s using phase rate and ±0.31°/s using Doppler measurements with the separation of onboard antennas of ca. 1·34 m. 10 m baselines could satisfy the sensor requirements for angular velocity determination during berthing maneuvers.

Sign in / Sign up

Export Citation Format

Share Document