Observation of Gas Pores inside the Columnar Grains of a Lotus Type Porous Copper

2018 ◽  
Vol 933 ◽  
pp. 182-187
Author(s):  
Sheng Lin Li ◽  
Qing Lin Jin
Keyword(s):  
Free Energy ◽  
Grain Boundary ◽  
Porous Material ◽  
Energy State ◽  
Pure Copper ◽  
Subsequent Growth ◽  
Porous Copper ◽  
Copper Melt ◽  
Columnar Grains ◽  
Pore Nucleation

Gas pores growing inside the columnar grains, instead of at grain boundary regions were observed in a lotus type porous copper. It is suggested that the lack of effective nucleation substrate in the pure copper melt makes the nucleation and subsequent growth of gas pores difficult. Therefore the melt must be sufficiently undercooled to provide enough free energy for the nucleation, and as a result the gas saturated melt will transform into a higher energy state of gas pores inside the columnar grains. Keywords: Porous material; Solidification; Gas Pore; Nucleation.

Free Energy of the Σ = 11 (332) Tilt Grain Boundary in Silicon

1993 ◽  
Vol 126-128 ◽  
pp. 253-256 ◽  
Author(s):  
S. Mourelatos ◽  
N. Ralantoson ◽  
P. Delavignette ◽  
A. Hairie ◽  
F. Hairie ◽  
...  
Keyword(s):  
Free Energy ◽  
Grain Boundary ◽  
Tilt Grain Boundary

The Free Energy Simulation Approach to Grain Boundary Segregation In Cu-Ni

1990 ◽  
Vol 209 ◽  
Author(s):  
H. Y. Wang ◽  
R. Najafabadi ◽  
D. J. Srolovitz ◽  
R. Lesar
Keyword(s):  
Monte Carlo ◽  
Free Energy ◽  
Grain Boundary ◽  
Chemical Potential ◽  
Boundary Segregation ◽  
Configurational Entropy ◽  
Accurate Method ◽  
Increasing Temperature ◽  
Atomic Coordinates ◽  
Good Agreement

ABSTRACTA new, accurate method for determining equilibrium segregation to defects in solids is employed to examine the segregation of Cu to grain boundaries in Cu-Ni alloys. The results are in very good agreement with the ones given by Monte Carlo. This method is based upon a point approximation for the configurational entropy, an Einstein model for vibrational contributions to the free energy. To achieve the equilibrium state of a defect in an alloy the free energy is minimized with respect to atomic coordinates and composition of each site at constant chemical potential. One of the main advantages this new method enjoys over other methods such as Monte Carlo, is the efficiency with which the atomic structure of a defect, segregation and thermodynamic properties can be determined. The grain boundary free energy can either increase or decrease with increasing temperature due to the competition between energetic and configurational entropy terms. In general, the grain boundary free energy increases with temperature when the segregation is strongest.

Grain-boundary free energy via thermodynamic integration

2006 ◽  
Vol 124 (6) ◽  
pp. 064707 ◽  
Author(s):  
Mark T. Lusk ◽  
Michael R. Fellinger ◽  
Paul D. Beale
Keyword(s):  
Free Energy ◽  
Grain Boundary ◽  
Thermodynamic Integration

Diffusion-Induced Grain Boundary Migration and Role of Defects

1993 ◽  
Vol 319 ◽  
Author(s):  
T.K. Chaki
Keyword(s):  
Free Energy ◽  
Grain Boundary ◽  
Boundary Migration ◽  
Solute Concentration ◽  
Grain Boundary Migration ◽  
Thermally Activated ◽  
Energy Of Mixing ◽  
Free Energy Of Mixing ◽  
Liquid Film Migration ◽  
Lattice Diffusivity

AbstractA model is presented to explain various aspects of diffusion-induced grain boundary migration (DIGM). The driving energies of DIGM are identified as the free energy of mixing and the interface free energy, the former being predominant in most cases of DIGM. The grain boundary migrates due to thermally activated motion of atoms across the interface under the influence of the driving energies. An expression for the velocity of migration is derived. It is shown that this depends parabolically on the solute concentration, in agreement with experimental observations in the case of liquid film migration (LFM), which is analogous to DIGM. Furthermore, the velocity is proportional to lattice diffusivity ahead of the boundary. Recent results of enhancement of DIGM by ion bombardment is explained by radiation-enhanced lattice diffusivity due to introduction of point defects by the ions. The model also explains that diffusion-induced recrystallization (DIR) is due to a free energy decrease associated with the transformation from the amorphous phase in the grain boundary layer to the crystalline phase.

Micro-Encapsulation and Tuning of Biomolecular Unit Cell Networks

2014 ◽  
Author(s):  
Mary-Anne Nguyen ◽  
Stephen A. Sarles
Keyword(s):  
Free Energy ◽  
Lipid Bilayers ◽  
Lipid Membrane ◽  
Energy State ◽  
Model Development ◽  
Solid Material ◽  
Mineral Oil ◽  
Material System ◽  
Electrical Measurements ◽  
Unit Cells

The goal of our research is to fabricate an autonomic material system that provides compartmentalization and multi-bilayer networks for enabling collective biomolecular functionality, as is found in living cells and tissues. The material system is based on biomolecular unit cells, which consist of synthetic lipid bilayers formed at the interfaces of lipid-coated aqueous droplets submerged in oil and contained in a solid material. This paper focuses on microfluidic encapsulation of unit cells within a solid material and tuning the amount of contact between droplets, two approaches aimed at increasing the functional density of the droplet-based material system. Hydrodynamic traps within microfluidic platforms have shown to be a promising method to capture single droplets within microfluidic devices. Herein, we develop a resistive flow model to design hydrodynamic traps for collecting pairs of droplets in a direct trapping mode to form unit cells. We also compare to the model the results of droplet trapping in a prototype microfluidic device fabricated prior to model development. In addition to flow techniques for assembling unit cells in solid materials, we examine the use of mineral oil as the hydrophobic oil phase that surrounds the droplets to increase the area of the lipid membrane formed between neighboring droplets. Compared to hexadecane, mineral oil produces larger contact areas between droplets and more-tightly packed multi-bilayer networks. The total free energies of formation for droplet arrays in mineral oil and hexadecane indicate that connected droplets in mineral oil exhibit a greater decrease in free energy upon formation (i.e. they exist at a lower energy state compared to those in hexadecane) and that hexagonal packing provides the maximum amount of decrease in free energy per droplet for droplets in large arrays. Electrical measurements of unit cells formed in mineral oil initially show gigaohm resistances typical of unit cells, however these unit cells exhibit increasing values of conductance as the bilayer areas grow.

Sign in / Sign up

Export Citation Format

Share Document