THE ROLE OF DISLOCATIONS AND GRAIN BOUNDARIES IN TRANSPORT PROCESSES IN IONIC CRYSTALS

It has been almost universally adopted that dissolution of solids proceeds with development of uniform, continuous frontiers of reaction.However this point of view is doubtful / 1 /. E.g. we have proved the active role of the block (grain) boundaries in the main phases of cement, these boundaries being the areas of hydrate phases' nucleation / 2 /. It has brought to the supposition that the dissolution frontier of cement particles in water is discrete. It seems also probable that the dissolution proceeds through the channels, which serve both for the liquid phase movement and for the drainage of the incongruant solution products. These channels can be appeared along the block boundaries.In order to demonsrate it, we have offered the method of phase-contrast impregnation of the hardened cement paste with the solution of methyl metacrylahe and benzoyl peroxide. The viscosity of this solution is equal to that of water.

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Carbide precipitation and chromium depletion on coherent twin boundaries in deformed 304 stainless steels

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100130717 ◽

1992 ◽

Vol 50 (2) ◽

pp. 1216-1217

Author(s):

A.H. Advani ◽

L.E. Murr ◽

D.J. Matlock ◽

W.W. Fisher ◽

P.M. Tarin ◽

...

Keyword(s):

Grain Boundaries ◽

Stainless Steels ◽

Interfacial Free Energy ◽

Carbide Precipitation ◽

Twin Boundaries ◽

Invariant Structure ◽

Heat Treated ◽

Constant Structure ◽

Cr Depletion

Coherent annealing-twin boundaries are constant structure and energy interfaces with an average interfacial free energy of ∼19mJ/m2 versus ∼210 and ∼835mJ/m2 for incoherent twins and “regular” grain boundaries respectively in 304 stainless steels (SS). Due to their low energy, coherent twins form carbides about a factor of 100 slower than grain boundaries, and limited work has also shown differences in Cr-depletion (sensitization) between twin versus grain boundaries. Plastic deformation, may, however, alter the kinetics and thermodynamics of twin-sensitization which is not well understood. The objective of this work was to understand the mechanisms of carbide precipitation and Cr-depletion on coherent twin boundaries in deformed SS. The research is directed toward using this invariant structure and energy interface to understand and model the role of interfacial characteristics on deformation-induced sensitization in SS. Carbides and Cr-depletion were examined on a 20%-strain, 0.051%C-304SS, heat treated to 625°C-4.5h, as described elsewhere.

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The Role of Fluid Mud in Sediment Transport Processes Along a Muddy Coast

10.21236/ada626141 ◽

2001 ◽

Author(s):

Gail C. Kineke

Keyword(s):

Sediment Transport ◽

Transport Processes ◽

Fluid Mud

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Kesterite Thin‐Film Solar Cell: Role of Grain Boundaries and Defects in Copper–Zinc–Tin–Sulfide and Copper–Zinc–Tin–Selenide

physica status solidi (a) ◽

10.1002/pssa.202100039 ◽

2021 ◽

pp. 2100039

Author(s):

Lingam Sravani ◽

Soumyaranjan Routray ◽

Kumar Prasannajit Pradhan ◽

Maykel Courel Piedrahita

Keyword(s):

Thin Film ◽

Solar Cell ◽

Grain Boundaries ◽

Thin Film Solar Cell ◽

Tin Sulfide ◽

Copper Zinc Tin Sulfide ◽

Tin Selenide ◽

Copper Zinc

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Internal melt figures in ice by rapid adiabatic compression

Journal of Glaciology ◽

10.3189/s0022143000003890 ◽

1994 ◽

Vol 40 (134) ◽

pp. 132-134

Author(s):

R.E. Gagnon ◽

C. Tulk ◽

H. Kiefte

Keyword(s):

Phase Transformations ◽

Grain Boundaries ◽

Single Crystals ◽

Adiabatic Compression ◽

Air Bubbles ◽

Water Ice ◽

Deep Focus ◽

And Behavior ◽

First Time

AbstractSingle crystals and bicrystals of water ice have been adiabatically pressurized to produce, and clearly illustrate, two types of internal melt figures: (1) dendritic figures that grow from nucleation imperfections on the specimen’s surface, or from air bubbles at grain boundaries, into the ice as pressure is elevated; and (2) compression melt fractures, flat liquid-filled disks, that nucleate at imperfections in the crystal and grow with the application of pressure eventually to sprout dendritic fingers at the periphery. The transparency of the ice permitted visualization of the growth and behavior of the figures, and this could be an important tool in understanding the role of phase transformations in deep-focus earthquakes. Correlation between figure size and pressure is noted for the first time.

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On the Role of Diffusion in the Oxidation of Fe, Ni, Co and the Fe-Sn Alloy by Calcium and Sodium Sulfates

Defect and Diffusion Forum ◽

10.4028/www.scientific.net/ddf.258-260.63 ◽

2006 ◽

Vol 258-260 ◽

pp. 63-67

Author(s):

V.M. Chumarev ◽

V.P. Maryevich ◽

V.A. Shashmurin

Keyword(s):

Co Oxidation ◽

Chemical Reaction ◽

Diffusion Processes ◽

Transport Processes ◽

Diffusion Transport ◽

Sodium Sulfates ◽

Product Forms ◽

Kinetics Of ◽

Dominant Part

Diffusion processes play a dominant part in the macro kinetics of Fe, Ni and Co oxidation by calcium and sodium sulfates. Here, the reaction product forms a compact covering which spatially divides the reagents on the surface in the same way as in the oxidation and sulfidization of metals by oxygen and sulfur. Therefore, it is possible to assume in advance that interaction of metals with calcium and sodium sulfates will be determined not by the actual chemical reaction properly but by the diffusion transport processes.

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Role of Grain Boundaries in diffusional Phenomena during Gas Nitriding of Pure Iron

Procedia Engineering ◽

10.1016/j.proeng.2011.04.488 ◽

2011 ◽

Vol 10 ◽

pp. 2943-2948 ◽

Cited By ~ 2

Author(s):

S. Fare ◽

N. Lecis ◽

E. Brescia ◽

M. Mazzola

Keyword(s):

Grain Boundaries ◽

Pure Iron ◽

Gas Nitriding

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Microstructure of Polycrystalline MgO Penetrated by a Silicate Liquid

Microscopy and Microanalysis ◽

10.1017/s1431927696211134 ◽

1996 ◽

Vol 2 (3) ◽

pp. 113-128 ◽

Cited By ~ 3

Author(s):

Sundar Ramamurthy ◽

Michael P. Mallamaci ◽

Catherine M. Zimmerman ◽

C. Barry Carter ◽

Peter R. Duncombe ◽

...

Keyword(s):

Grain Boundaries ◽

Grain Growth ◽

Glassy Phase ◽

Silicate Liquid ◽

Two Phase ◽

The Matrix ◽

Devitrification Process ◽

Phase Mixture

Dense, polycrystalline MgO was infiltrated with monticellite (CaMgSiO4) liquid to study the penetration of liquid along the grain boundaries of MgO. Grain growth was found to be restricted with increasing amounts of liquid. The inter-granular regions were generally found to be comprised of a two-phase mixture: crystalline monticellite and a glassy phase rich in the impurities present in the starting MgO material. MgO grains act as seeding agents for the crystallization of monticellite. The location and composition of the glassy phase with respect to the MgO grains emphasizes the role of intergranular liquid during the devitrification process in “snowplowing” impurities present in the matrix.

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