scholarly journals Application of Crystal Growth Theory in Graphene CVD Nucleation and Growth

2014 ◽  
Vol 72 (3) ◽  
pp. 345 ◽  
Author(s):  
Lu Wang ◽  
Junfeng Gao ◽  
Feng Ding
Keyword(s):  
Crystal Growth ◽  
Nucleation And Growth ◽  
Growth Theory

Phase separation in undercooled molten Pd80Si20: Part I

1999 ◽  
Vol 14 (9) ◽  
pp. 3653-3662 ◽  
Author(s):  
K. L. Lee ◽  
H. W. Kui
Keyword(s):  
Growth Rate ◽  
Phase Separation ◽  
Crystal Growth ◽  
Grain Refinement ◽  
Crystallization Temperature ◽  
Sharp Decrease ◽  
Nucleation And Growth ◽  
Crystal Growth Rate ◽  
Large Undercooling ◽  
Kinetic Crystallization

Three different kinds of morphology are found in undercooled Pd80Si20, and they dominate at different undercooling regimens ΔT, defined as ΔT = T1 – Tk, where T1 is the liquidus of Pd80Si20 and Tk is the kinetic crystallization temperature. In the small undercooling regimen, i.e., for ΔT ≤ 190 K, the microstructures are typically dendritic precipitation with a eutecticlike background. In the intermediate undercooling regimen, i.e., for 190 ≤ ΔT ≤ 220 K, spherical morphologies, which arise from nucleation and growth, are identified. In addition, Pd particles are found throughout an entire undercooled specimen. In the large undercooling regimen, i.e., for ΔT ≥ 220 K, a connected structure composed of two subnetworks is found. A sharp decrease in the dimension of the microstructures occurs from the intermediate to the large undercooling regimen. Although the crystalline phases in the intermediate and the large undercooling regimens are the same, the crystal growth rate is too slow to bring about the occurrence of grain refinement. Combining the morphologies observed in the three undercooling regimens and their crystallization behaviors, we conclude that phase separation takes place in undercooled molten Pd80Si20.

scholarly journals Non-Isothermal Crystallisation Kinetics of Polypropylene at High Cooling Rates and Comparison to the Continuous Two-Domain pvT Model

Polymers ◽  
2020 ◽  
Vol 12 (7) ◽  
pp. 1515
Author(s):  
Jonathan Alms ◽  
Christian Hopmann ◽  
Jian Wang ◽  
Tobias Hohlweck
Keyword(s):  
Injection Moulding ◽  
Polymer Processing ◽  
Nucleation And Growth ◽  
Growth Theory ◽  
Crystallisation Kinetics ◽  
Cooling Rates ◽  
Dsc Measurements ◽  
Wide Range ◽  
High Cooling Rates ◽  
Kinetics Of

The modelling of the correlation between pressure, specific volume and temperature (pvT) of polymers is highly important for applications in the polymer processing of semi-crystalline thermoplastics, especially in injection moulding. In injection moulding, the polymer experiences a wide range of cooling rates, for example, 60 °C/min near the centre of the part and up to 3000 °C/min near the mould walls. The cooling rate has a high influence on the pvT behaviour, as was shown in the continuous two-domain pvT model (CTD). This work examined the Hoffman–Lauritzen nucleation and growth theory used in the modified Hammami model for extremely high cooling rates (up to 300,000 °C/min) by means of Flash differential scanning calorimeter (DSC) measurements. The results were compared to those of the empirical continuous two-domain pvT model. It is shown that the Hammami model is not suitable to predict the crystallisation kinetics of polypropylene at cooling rates above 600 °C/min, but that the continuous two-domain pvT model is well able to predict crystallisation temperatures at high cooling rates.

scholarly journals In situ X-ray Diffraction Investigation of the Crystallisation of Perfluorinated Ce(IV)-based Metal-Organic Frameworks with UiO-66 and MIL-140 architectures

2020 ◽  
Author(s):  
Stephen Shearan ◽  
Jannick Jacobsen ◽  
Ferdinando Costantino ◽  
Roberto D’Amato ◽  
Dmitri Novikov ◽  
...  
Keyword(s):  
Crystal Growth ◽  
Metal Organic Frameworks ◽  
Building Blocks ◽  
Nucleation And Growth ◽  
X Ray Diffraction ◽  
X Ray ◽  
Rate Determining Step ◽  
Wide Range ◽  
Metal Organic

We report on the results of a thorough <i>in situ</i> synchrotron powder X-ray diffraction study of the crystallisation in aqueous medium of two recently discovered perfluorinated Ce(IV)-based metal-organic frameworks (MOFs), analogues of the already well investigated Zr(IV)-based UiO-66 and MIL-140A, namely, F4_UiO-66(Ce) and F4_MIL-140A(Ce). The two MOFs were originally obtained in pure form in similar conditions, using ammonium cerium nitrate and tetrafluoroterephthalic acid as building blocks, and small variations of the reaction parameters were found to yield mixed phases. Here, we investigate the crystallisation of these compounds <i>in situ</i> in a wide range of conditions, varying parameters such as temperature, amount of the protonation modulator nitric acid (HNO<sub>3</sub>) and amount of the coordination modulator acetic acid (AcOH). When only HNO<sub>3</sub> is present in the reaction environment, F4_MIL-140A(Ce) is obtained as a pure phase. Heating preferentially accelerates nucleation, which becomes rate determining below 57 °C, whereas the modulator influences nucleation and crystal growth to a similar extent. Upon addition of AcOH to the system, alongside HNO<sub>3</sub>, mixed-phased products, consisting of F4_MIL-140A(Ce) and F4_UiO-66(Ce), are obtained. In these conditions, F4_UiO-66(Ce) is always formed faster and no interconversion between the two phases occurs. In the case of F4_UiO-66(Ce), crystal growth is always the rate determining step. An increase in the amount of HNO<sub>3</sub> slows down both nucleation and growth rates for F4_MIL-140A(Ce), whereas nucleation is mainly affected for F4_UiO-66(Ce). In addition, a higher amount HNO<sub>3</sub> favours the formation of F4_MIL-140A(Ce). Similarly, increasing the amount of AcOH leads to slowing down of the nucleation and growth rate, but favours the formation of F4_UiO-66(Ce). The pure F4_UiO-66(Ce) phase could also be obtained when using larger amounts of AcOH in the presence of minimal HNO<sub>3</sub>. Based on these <i>in situ</i> results, a new optimised route to achieving a pure, high quality F4_MIL-140A(Ce) phase in mild conditions (60 °C, 1 h) is also identified.

The Stimulated Crystallization of Amorphous SiO2 Films on Si Substrates Induced By Laser and Thermal Treatments

1988 ◽  
Vol 116 ◽  
Author(s):  
Felix Edelman
Keyword(s):  
Incubation Time ◽  
Crystallization Process ◽  
Laser Flash ◽  
Nucleation And Growth ◽  
Point Of View ◽  
Growth Theory ◽  
Thermal Treatments ◽  
Kinetic Characteristics ◽  
Amorphous Sio2 ◽  
Si Substrates

AbstractThe transformation of amorphous to crystal (a-c) structure of Si02 layers, thermally grown on both (100) and (111) Si substrates, was carried out by CO2 laser, flash-lamp, and furnace heat: treatments. All the treatments resulted in S102 crystallization according to two different mechanisms: normal and self-sustained growth processes. The kinetic characteristics of the S102 crystallization process such as incubation time, rates of nucleation and growth, and the microstructure of the Si-Si02 interface were investigated and are discussed from the point of view of growth theory. The a-c transformation in Si3N4 and SixOyNz films on Si substrates is also discussed.

Organic-Inorganic Nanocomposites Based on Iron Containing Clusters and Biomolecules

1995 ◽  
Vol 48 (4) ◽  
pp. 783 ◽  
Author(s):  
P Chan ◽  
W Chuaanusorn ◽  
M Nesterova ◽  
P Sipos ◽  
TG Stpierre ◽  
...  
Keyword(s):  
Crystal Growth ◽  
Chondroitin Sulfate ◽  
Iron Sulfide ◽  
Nucleation And Growth ◽  
Protein Cage ◽  
Structural Order ◽  
Nucleation Sites ◽  
Inorganic Nanocomposites ◽  
Higher Temperature ◽  
Inorganic Clusters

Biopolymers, such as the protein ferritin and the polysaccharides chondroitin sulfate and chitosan, have been used to control the nucleation and growth of nanoscale iron(III) hydroxide clusters. The biopolymers can provide nucleation sites, that in some cases are spatially defined by the shape of the polymer, and/or defined volumes within which crystal growth of the iron(III) hydroxide can proceed. The product inorganic clusters are bound to the organic polymers which both keep them in solution and prevent aggregation. The morphology of the clusters (spheres or rods) and the uniformity of their dimensions are determined by the biopolymer chosen. The temperature of formation is shown to have an effect on the structure of the clusters, a higher temperature resulting in larger inorganic clusters with a higher degree of structural order. Iron(III) hydroxide clusters in ferritin cages can be partially transformed to iron sulfide by reaction with H2S gas while remaining in the protein cage.

Crystal Growth – Theory and Techniques Vol 2

1979 ◽  
Vol 30 (10) ◽  
pp. 439-439
Author(s):  
J A Champion
Keyword(s):  
Crystal Growth ◽  
Growth Theory
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