On Specific Phase Transitions to the Compound-Like Impurity Nanosegregation Structures at Dislocations and Grain Boundaries in Metals and their Influence on Diffusion-Assisted Processes

2008 ◽  
Vol 138 ◽  
pp. 91-118 ◽  
Author(s):  
Yuriy S. Nechaev
Keyword(s):  
Phase Transitions ◽  
Grain Boundaries ◽  
Elevated Temperatures ◽  
Physical And Mechanical Properties ◽  
Nanostructured Metals ◽  
Study Results ◽  
And Diffusion ◽  
Specific Phase Transitions ◽  
Specific Phase

Specific phase transitions to the compound-like impurity nanosegregation structures at dislocations and grain boundaries in metals and their influence on diffusion-assisted processes are considered, mainly, on the basis of the thermodynamic analysis of the related experimental data. The following systems and aspects are in detail considered: (1) the hydride-like nanosegregation of hydrogen at dislocations and grain boundaries in palladium and their influence on the apparent characteristics of hydrogen solubility and diffusivity in palladium; (2) the physics of the anomalous characteristics of diffusion of Fe and other transition impurities in crystalline Al at elevated temperatures, the role of the compound-like nanosegregation (CLNS) of Fe and the others at dislocations and grain boundaries in Al, analysis of the Mössbauer and diffusion data on CLNS of Fe at grain boundaries and dislocations in Al; (3) some new physical aspects of internal oxidation and nitridation of metals (for Cu-0.3%Fe alloy/Cu2O surface layer, and for (Ni-5%Cr) alloy / N2 gas), the role of the compound-like impurity nanosegregation at dislocations and grain boundaries, study results on the deviations from the classical theories predictions and their interpretation. The possibility is considered of nanotechnology applications of the study results for creation of nanostructured metals with compound-like nanosegregation structures at grain boundaries, in order to obtain specific physical and mechanical properties of such a cellural-type nanocomposites. In particular, it can be complex hydride-like, carbide-like, nitride-like, carbide-nitride-like, oxide-like or intermetallide-like nanosegregation structures at grain boundaries of nanostructured metals.

scholarly journals Refining the Design of Diblock Elastin-Like Polypeptides for Self-Assembly into Nanoparticles

Polymers ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 1470
Author(s):  
Michèle Dai ◽  
Evangelos Georgilis ◽  
Guillaume Goudounet ◽  
Bertrand Garbay ◽  
Jan Pille ◽  
...  
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Self Assembly ◽  
Diblock Copolymers ◽  
Thermal Phase Transition ◽  
Thermal Phase ◽  
Specific Phase Transitions ◽  
Specific Phase

Diblock copolymers based-on elastin-like polypeptide (ELP) have the potential to undergo specific phase transitions when thermally stimulated. This ability is especially suitable to form carriers, micellar structures for instance, for delivering active cargo molecules. Here, we report the design and study of an ELP diblock library based on ELP-[M1V3-i]-[I-j]. First, ELP-[M1V3-i]-[I-j] (i = 20, 40, 60; j = 20, 90) that showed a similar self-assembly propensity (unimer-to-aggregate transition) as their related monoblocks ELP-[M1V3-i] and ELP-[I-j]. By selectively oxidizing methionines of ELP-[M1V3-i] within the different diblocks structures, we have been able to access a thermal phase transition with three distinct regimes (unimers, micelles, aggregates) characteristic of well-defined ELP diblocks.

On the Mechanism of Oxidation Resistance of W-Cr-Pd Alloys

2018 ◽  
Vol 383 ◽  
pp. 133-141
Author(s):  
Alon Kafri ◽  
Alexandra Makonovitsky ◽  
Roni Z. Shneck
Keyword(s):  
Free Surface ◽  
Grain Boundaries ◽  
Oxidation Resistance ◽  
Intermediate Layer ◽  
Elevated Temperatures ◽  
Fast Diffusion ◽  
External Layer ◽  
Present Contribution ◽  
Mechanism Of Oxidation

While studying activation sintering of tungsten, Evans [5] and Ito and Furusawa [6] revealed that W-Cr-Pd alloys exhibit unexpected oxidation resistance at elevated temperatures. The role of palladium in stimulating oxidation resistance in W-Cr alloys is the main aim of the present contribution. As previously observed, at 800 °C these alloys form a relatively dense protective scale that consists of an inner layer of Cr2O3, an intermediate layer of Cr2WO6 and an external layer of WO3. At 1200 °C only Cr2WO6 layer is found, since the Cr2O3 and WO3 evaporate. To determine the role of paladium, W and W-Pd alloys were coated with Cr layers and undergone diffusion experiments. An extraordinary affinity between the Cr and Pd was revealed, manifested by extremely fast inward diffusion of Cr along grain boundaries. In a second experiment the dissolution of Cr into W grains at 1300°C was followed and found to take place preferentially along grain boundaries. These observations assess that the Pd segregated at grain boundaries provides fast diffusion channels for Cr to the free surface and it imparts the significant improvement of the oxidation resistance of W alloys, as suggested by Lee and Simkovitz [10-12].

scholarly journals Эволюция дефектной структуры при испытаниях в режиме ползучести ультрамелкозернистых металлов и сплавов, полученных методами интенсивной пластической деформации

2020 ◽  
Vol 62 (2) ◽  
pp. 267
Author(s):  
В.И. Бетехтин ◽  
А.Г. Кадомцев ◽  
М.В. Нарыкова
Keyword(s):  
Grain Boundaries ◽  
Elevated Temperatures ◽  
Mechanical Stability ◽  
Diffusion Mechanism ◽  
Metals And Alloys ◽  
Structural Factors ◽  
X Ray Scattering ◽  
Ultrafine Grained

Using small-angle X-ray scattering, electron microscopy, and density measurements, structural factors have been identified that lead to a decrease in the mechanical stability of ultrafine-grained (UFG) metals and alloys when tested in creep mode at elevated temperatures. It has been established that one of the important factors is nanopores formed during intense plastic deformation. The development of these nanopores in grain boundaries formed during creep is realized by the diffusion mechanism and leads to destruction. The role of dispersed inclusions and high-angle grain boundaries for the strength of UFG metals and alloys under their “short-term” and long-term loading is considered.

scholarly journals SATB1 undergoes isoform-specific phase transitions in T cells

2021 ◽  
Author(s):  
Tomas Zelenka ◽  
Petros Tzerpos ◽  
Giorgos Panagopoulos ◽  
Konstantinos Tsolis ◽  
Dionysios-Alexandros Papamatheakis ◽  
...  
Keyword(s):  
Phase Transitions ◽  
Gene Expression Regulation ◽  
Nuclear Bodies ◽  
Intracellular Space ◽  
Post Translational Modifications ◽  
Cellular Processes ◽  
Nuclear Rna ◽  
Separation Phase ◽  
Specific Phase Transitions ◽  
Specific Phase

Intracellular space is demarcated into functional membraneless organelles and nuclear bodies via the process of phase separation. Phase transitions are involved in many functions linked to such bodies as well as in gene expression regulation and other cellular processes. In this work we describe how the genome organizer SATB1 utilizes its prion-like domains to undergo phase transitions. We have identified two SATB1 isoforms with distinct biophysical behavior and showed how phosphorylation and interaction with nuclear RNA, impact their phase transitions. Moreover, we show that SATB1 is associated with transcription and splicing, both of which evinced deregulation in Satb1 knockout mice. Thus, the tight regulation of different SATB1 isoforms levels and their post-translational modifications are imperative for SATB1's physiological roles in T cell development while their deregulation may be linked to disorders such as cancer.

Elucidation of block boundaries as the dissolution channels in hydrated cement

1978 ◽  
Vol 36 (1) ◽  
pp. 484-485
Author(s):  
N.V. Belov ◽  
U.I. Papiashwili ◽  
B.E. Yudovich
Keyword(s):  
Liquid Phase ◽  
Grain Boundaries ◽  
Benzoyl Peroxide ◽  
Phase Contrast ◽  
Active Role ◽  
Point Of View ◽  
Hardened Cement ◽  
Hydrated Cement ◽  
Hardened Cement Paste

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.

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

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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