Investigation of nucleation and growth phenomena during the thermal and light induced spin transition in the [Fe(1-bpp)2][BF4]2 complex

2015 ◽  
Vol 87 (3) ◽  
pp. 261-270 ◽  
Author(s):  
Sylvain Rat ◽  
José Sánchez Costa ◽  
Salma Bedoui ◽  
William Nicolazzi ◽  
Gábor Molnár ◽  
...  
Keyword(s):  
Phase Separation ◽  
Volume Fraction ◽  
Spin Transition ◽  
Optical Microscope ◽  
Nucleation And Growth ◽  
Spin Conversion ◽  
Continuous Irradiation ◽  
Small Volume Fraction ◽  
Nucleation And Growth Mechanism ◽  
Peculiar Behavior

AbstractOptical microscopy measurements have been realized on single crystals of the [Fe(1-bpp)2][BF4]2 complex (1-bpp=2,6-di(pyrazol-1-yl)pyridine). The thermal spin transition around 253 K occurs by a heterogeneous nucleation and growth mechanism and involves a clear phase separation and a small hysteresis. This very abrupt and complete thermal transition is preceded by a premonitory spin conversion, which implies only a small fraction (ca. 2–3 %) of the molecules. This peculiar behavior may be the sign of heterophase fluctuations. The light-induced spin transition from the stable low spin (LS) to the metastable high spin (HS) phase was achieved at 80 K by focusing laser light into a small volume fraction of the crystal. Under continuous irradiation this photo-converted HS “nucleus” then grows and the whole crystal converts to the HS phase providing evidence for a light-induced instability in the system due to long-range elastic interactions. The relaxation of the light-induced metastable HS phase at 83 K follows a sigmoidal decay – typical of cooperative spin crossover systems. Nevertheless the spatial development of this relaxation process appears very homogeneous and no phase separation could be detected within the resolution of the optical microscope.

Llo Phase Formation in CoPt Thin Films

1997 ◽  
Vol 475 ◽  
Author(s):  
R. A. Ristau ◽  
K. Barmak ◽  
K. R. Coffey ◽  
J. K. Howard
Keyword(s):  
Thin Films ◽  
Phase Formation ◽  
Volume Fraction ◽  
Parent Phase ◽  
High Volume ◽  
Nucleation And Growth ◽  
High Coercivity ◽  
Nucleation And Growth Mechanism ◽  
Very High ◽  
Disorder Transition Temperature

ABSTRACTThe high magnetic anisotropy and high coercivity of equiatomic CoPt thin films make them attractive as potential materials for magnetic recording applications. Magnetic coercivity (Hc) over 10 kOe has been measured in films in which the as-deposited fee phase has been partially transformed to the atomically ordered Ll0 phase. Very high Hc has been related to high volume fraction and small size of the Ll0 precipitates. A better understanding of the Ll0 phase formation and quantification of volume fraction is critical to optimizing the magnetic properties of this material.As we have previously reported, an increase in Hc was observed with an increase in Ll0 volume fraction in 10 nm thick, equiatomic CoPt films. In our current investigation we have observed that, at anneal temperatures far from the order/disorder transition temperature, e.g. at T = 0.6 Tc, numerous, very fine Ll0 precipitates are seen, some of which cluster at the parent phase grain boundaries. At T = 0.85 Tc, very few, larger Ll0 regions were seen. As precipitates of the ordered phase grow to impingement, antiphase boundaries (APB) are formed. This is consistent with a heterogeneous nucleation and growth mechanism for the formation of the Ll0 phase throughout the temperature range studies.

Carboxyl-functionalized nanochannels based on block copolymer hierarchical structures

2018 ◽  
Vol 209 ◽  
pp. 303-314 ◽  
Author(s):  
Valentina-Elena Musteata ◽  
Stefan Chisca ◽  
Florian Meneau ◽  
Detlef-M. Smilgies ◽  
Suzana P. Nunes
Keyword(s):  
Phase Separation ◽  
Block Copolymer ◽  
Block Copolymers ◽  
Growth Mechanism ◽  
Butyl Acrylate ◽  
Hierarchical Structures ◽  
Nucleation And Growth ◽  
Porous Structures ◽  
Hexagonally Ordered ◽  
Nucleation And Growth Mechanism

Hierarchical isotropic porous structures with spherical micrometer-sized cavities, interconnected by hexagonally ordered nanochannels, were prepared based on the phase separation of polystyrene-b-poly(t-butyl acrylate) block copolymers, following a nucleation and growth mechanism.

scholarly journals Liquid–liquid phase separation and morphologies in organic particles consisting of <i>α</i>-pinene and <i>β</i>-caryophyllene ozonolysis products and mixtures with commercially available organic compounds

2020 ◽  
Vol 20 (19) ◽  
pp. 11263-11273
Author(s):  
Young-Chul Song ◽  
Ariana G. Bé ◽  
Scot T. Martin ◽  
Franz M. Geiger ◽  
Allan K. Bertram ◽  
...  
Keyword(s):  
Phase Separation ◽  
Liquid Phase ◽  
Aerosol Particles ◽  
Organic Aerosol ◽  
Nucleation And Growth ◽  
Liquid Phases ◽  
Two Component ◽  
Organic Particles ◽  
Nucleation And Growth Mechanism ◽  
Liquid Liquid Phase Separation

Abstract. Liquid–liquid phase separation (LLPS) in organic aerosol particles can impact several properties of atmospheric particulate matter, such as cloud condensation nuclei (CCN) properties, optical properties, and gas-to-particle partitioning. Yet, our understanding of LLPS in organic aerosols is far from complete. Here, we report on the LLPS of one-component and two-component organic particles consisting of α-pinene- and β-caryophyllene-derived ozonolysis products and commercially available organic compounds of relevance to atmospheric organic particles. In the experiments involving single-component organic particles, LLPS was observed in 8 out of 11 particle types studied. LLPS almost always occurred when the oxygen-to-carbon elemental ratio (O:C) was ≤0.44 but did not occur when O:C was >0.44. The phase separation occurred by spinodal decomposition as well as the nucleation and growth mechanism, and when LLPS occurred, two liquid phases coexisted up to ∼100 % relative humidity (RH). In the experiments involving two-component organic particles, LLPS was observed in 23 out of 25 particles types studied. LLPS almost always occurred when the average was O:C ≤0.67 but never occurred when the average O:C was >0.67. The phase separation occurred by spinodal decomposition as well as the nucleation and growth mechanism. When LLPS occurred, two liquid phases coexisted up to ∼100 % RH. These results provide further evidence that LLPS is likely a frequent occurrence in organic aerosol particles in the troposphere, even in the absence of inorganic salts.

Porous Gel Coatings Obtained by Phase Separation in ORMOSIL System

2000 ◽  
Vol 628 ◽  
Author(s):  
Kazuki Nakanishi ◽  
Souichi Kumon ◽  
Kazuyuki Hirao ◽  
Hiroshi Jinnai
Keyword(s):  
Phase Separation ◽  
Reaction Time ◽  
Volume Fraction ◽  
Sol Gel ◽  
Reaction Times ◽  
Dip Coating ◽  
Coating Solution ◽  
Coating Method ◽  
Gel Phase ◽  
Dip Coating Method

ABSTRACTMacroporous silicate thick films were prepared by a sol-gel dip-coating method accompanied by the phase separation using methyl-trimethoxysilane (MTMS), nitric acid and dimethylformamide (DMF) as starting components. The morphology of the film varied to a large extent depending on the time elapsed after the hydrolysis until the dipping of the coating solution. On a glass substrate, the films prepared by early dipping had inhomogeneous submicrometer-sized pores on the surface of the film. At increased reaction times, relatively narrow sized isolated macropores were observed and their size gradually decreased with the increase of reaction time. On a polyester substrate, in contrast, micrometer-sized isolated spherical gel domains were homogeneously deposited by earlier dippings. With an increase of reaction time, the volume fraction of the gel phase increased, then the morphology of the coating transformed into co-continuous gel domains and macropores, and finally inverted into the continuous gel domains with isolated macropores. The overall morphological variation with the reaction time was explained in terms of the phase separation and the structure freezing by the forced gelation, both of which were induced by the evaporation of methanol during the dipping operation.

Formation of coherent twins in YBa2Cu3O7–δ superconductors

1989 ◽  
Vol 4 (4) ◽  
pp. 795-801 ◽  
Author(s):  
C. J. Jou ◽  
J. Washburn
Keyword(s):  
Oxygen Uptake ◽  
Growth Mechanism ◽  
Oxygen Uptake Rate ◽  
Nucleation And Growth ◽  
Electron Microscopic ◽  
Transmission Electron ◽  
Transmission Electron Microscopic ◽  
Twin Formation ◽  
Boundary Model ◽  
Nucleation And Growth Mechanism

A nucleation-and-growth mechanism for the twin formation in YBa2Cu3O7–δ superconductors based on the oxygen uptake rate curve and published transmission electron microscopic observations is proposed together with an oxygen-depleted twin boundary model. The difficulty of reaching stoichiometric YBa2Cu3O7 is explained.

scholarly journals The Modified Void Nucleation and Growth Model (MNAG) for Damage Evolution in BCC Ta

2021 ◽  
Vol 11 (8) ◽  
pp. 3378
Author(s):  
Jie Chen ◽  
Darby J. Luscher ◽  
Saryu J. Fensin
Keyword(s):  
Growth Model ◽  
Damage Evolution ◽  
Volume Fraction ◽  
Void Nucleation ◽  
Nucleation And Growth ◽  
Void Coalescence ◽  
Hydrodynamic Simulations ◽  
Void Evolution ◽  
Void Nucleation And Growth ◽  
Nucleation Growth

A void coalescence term was proposed as an addition to the original void nucleation and growth (NAG) model to accurately describe void evolution under dynamic loading. The new model, termed as modified void nucleation and growth model (MNAG model), incorporated analytic equations to explicitly account for the evolution of the void number density and the void volume fraction (damage) during void nucleation, growth, as well as the coalescence stage. The parameters in the MNAG model were fitted to molecular dynamics (MD) shock data for single-crystal and nanocrystalline Ta, and the corresponding nucleation, growth, and coalescence rates were extracted. The results suggested that void nucleation, growth, and coalescence rates were dependent on the orientation as well as grain size. Compared to other models, such as NAG, Cocks–Ashby, Tepla, and Tonks, which were only able to reproduce early or later stage damage evolution, the MNAG model was able to reproduce all stages associated with nucleation, growth, and coalescence. The MNAG model could provide the basis for hydrodynamic simulations to improve the fidelity of the damage nucleation and evolution in 3-D microstructures.

scholarly journals Microstructural Characterization and Mechanical Properties of Ti-6Al-4V Alloy Subjected to Dynamic Plastic Deformation Achieved by Multipass Hammer Forging with Different Forging Temperatures

2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Xiurong Fang ◽  
Jiang Wu ◽  
Xue Ou ◽  
Fuqiang Yang
Keyword(s):  
Mechanical Properties ◽  
Plastic Deformation ◽  
Volume Fraction ◽  
Microstructural Characterization ◽  
Optical Microscope ◽  
Strain Rates ◽  
Materials Properties ◽  
Forging Process ◽  
Hammer Forging ◽  
Dynamic Plastic Deformation

Dynamic plastic deformation (DPD) achieved by multipass hammer forging is one of the most important metal forming operations to create the excellent materials properties. By using the integrated approaches of optical microscope and scanning electron microscope, the forging temperature effects on the multipass hammer forging process and the forged properties of Ti-6Al-4V alloy were evaluated and the forging samples were controlled with a total height reduction of 50% by multipass strikes from 925°C to 1025°C. The results indicate that the forging temperature has a significant effect on morphology and the volume fraction of primary α phase, and the microstructural homogeneity is enhanced after multipass hammer forging. The alloy slip possibility and strain rates could be improved by multipass strikes, but the marginal efficiency decreases with the increased forging temperature. Besides, a forging process with an initial forging temperature a bit above β transformation and finishing the forging a little below the β transformation is suggested to balance the forging deformation resistance and forged mechanical properties.

Phase Separation: From the Initial Nucleation Stage to the Final Ostwald Ripening Regime

1997 ◽  
Vol 481 ◽  
Author(s):  
Celeste Sagui ◽  
Dean Stinson O'Gorman ◽  
Martin Grant
Keyword(s):  
Phase Separation ◽  
Late Stage ◽  
Ostwald Ripening ◽  
Early Stage ◽  
Classical Problem ◽  
Nucleation And Growth ◽  
New Model ◽  
Nucleation Stage ◽  
Initial Nucleation

ABSTRACTIn this work we have re-examined the classical problem of nucleation and growth. A new model considers the correlations among droplets and naturally incorporates the crossover from the early-stage, nucleation dominated regime to the scaling, late-stage, coarsening regime within a single framework.

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