Oriented nucleation and crystal growth of Ge-fresnoite (Ba2TiGe2O8) in 2BaO·TiO2·2GeO2 glasses with additional GeO2

CrystEngComm ◽  
2018 ◽  
Vol 20 (36) ◽  
pp. 5409-5421 ◽  
Author(s):  
Wolfgang Wisniewski ◽  
Jovana Dimitrijevic ◽  
Christian Rüssel
Keyword(s):  
Crystal Growth ◽  
Crystallization Temperature ◽  
Nucleation And Growth ◽  
Bulk Nucleation ◽  
Growth Selection ◽  
Temperature Constant

The oriented nucleation of Ge-fresnoite is clearly affected by increasing the amount of GeO2 in glasses of the mol composition 2BaO·TiO2·2GeO2 + xGeO2 (x = 0.0–1.5) while keeping the crystallization temperature constant. Bulk nucleation and growth selection occur in the bulk.

Oriented nucleation and crystal growth of Sr-fresnoite (Sr2TiSi2O8) in 2SrO·TiO2·2SiO2 glasses with additional SiO2

CrystEngComm ◽  
2018 ◽  
Vol 20 (23) ◽  
pp. 3234-3245 ◽  
Author(s):  
Wolfgang Wisniewski ◽  
Jovana Dimitrijevic ◽  
Christian Rüssel
Keyword(s):  
Phase Separation ◽  
Crystal Growth ◽  
Bulk Nucleation ◽  
Crystallisation Temperature ◽  
Growth Selection ◽  
Temperature Constant ◽  
Nucleation Growth

The oriented nucleation of Sr-fresnoite is barely affected by increasing the amount of SiO2 in glasses of the mol composition 2SrO·TiO2·2SiO2 + xSiO2 (x = 0 to 1.5) while keeping the crystallisation temperature constant. Bulk nucleation, growth selection and phase separation occur in the bulk.

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.

Enhanced crystallization and phase transformation of amorphous silicon nitride under high pressure

2001 ◽  
Vol 16 (1) ◽  
pp. 67-75 ◽  
Author(s):  
Ya-Li Li ◽  
Yong Liang ◽  
Fen Zheng ◽  
Xian-Feng Ma ◽  
Suo-Jing Cui ◽  
...  
Keyword(s):  
High Pressure ◽  
Phase Transformation ◽  
Silicon Nitride ◽  
Amorphous Silicon ◽  
Crystallization Temperature ◽  
Amorphous Materials ◽  
Normal Pressure ◽  
Nucleation And Growth ◽  
Amorphous Silicon Nitride ◽  
Amorphous Si

The crystallization and phase transformation of amorphous Si3N4 ceramics under high pressure (1.0–5.0 GPa) between 800 and 1700 °C were investigated. A greatly enhanced crystallization and α–β transformation of the amorphous Si3N4 ceramics were evident under the high pressure, as characterized by that, at 5.0 GPa, the amorphous Si3N4 began to crystallize at a temperature as low as 1000 °C (to transform to a modification). The subsequent a–b transformation occurred completed between 1350 and 1420 °C after only 20 min of pressing at 5.0 GPa. In contrast, under 0.1 MPa N2, the identical amorphous materials were stable up to 1400 °C without detectable crystallization, and only a small amount of a phase was detected at 1500 °C. The crystallization temperature and the a–b transformation temperatures are reduced by 200–350 °C compared to that at normal pressure. The enhanced phase transformations of the amorphous Si3N4 were discussed on the basis of thermodynamic and kinetic consideration of the effects of pressure on nucleation and growth.

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.

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.

Composition Controlled Synthesis and Raman Analysis of Ge-Rich SixGe1–x Nanowires

2008 ◽  
Vol 8 (6) ◽  
pp. 3153-3157 ◽  
Author(s):  
P. Meduri ◽  
G. U. Sumanasekera ◽  
Z. Chen ◽  
M. K. Sunkara
Keyword(s):  
Raman Spectroscopy ◽  
Phase Composition ◽  
Vapor Phase ◽  
Room Temperature ◽  
Nucleation And Growth ◽  
Accurate Estimation ◽  
Controlled Synthesis ◽  
Raman Analysis ◽  
Bulk Nucleation ◽  
Alloy Nanowires

Here, we report the synthesis of SixGe1–x nanowires with x values ranging from 0 to 0.5 using bulk nucleation and growth from larger Ga droplets. Room temperature Raman spectroscopy is shown to determine the composition of the as-synthesized SixGe1–x nanowires. Analysis of peak intensities observed for Ge (near 300 cm–1) and the Si-Ge alloy (near 400 cm–1) allowed accurate estimation of composition compared to that based on the absolute peak positions. The results showed that the fraction of Ge in the resulting SixGe1–x alloy nanowires is controlled by the vapor phase composition of Ge.

Melting Phenomena and Impurity Redistribution During Pulsed Laser Irradiation of Amorphous Silicon Layers

1983 ◽  
Vol 23 ◽  
Author(s):  
J. Narayan ◽  
C. W. White ◽  
O. W. Holland
Keyword(s):  
Electron Microscopy ◽  
Amorphous Silicon ◽  
Cross Section ◽  
Pulsed Laser ◽  
Nucleation And Growth ◽  
Bulk Nucleation ◽  
Section Electron ◽  
Section Electron Microscopy ◽  
Pulsed Laser Irradiation ◽  
Impurity Redistribution

ABSTRACTwe have investigated microstructural changes and phase transformations in 30Si+, 75As+, 63Cu+, and 115In+ implanted amorphous silicon layers as a function of pulse energy density. Cross-section electron microscopy studies have revealed the formation of two distinct regions, large and fine polycrystalline regions below the threshold for “defect-free” annealing. The fine polycrystalline region is formed primarily by explosive recrystallization, and occasionally by bulk nucleation and growth. The impurity redistribution in the large and fine polycrystalline regions were determined by Rutherford backscatterinq measurements. Large redistributions of impurities in the large poly region are consistent with velocity of solidifications of 3–5 ms−1. The nature of impurity redistributions in the fine poly region as a function of distribution coefficient provides information on the details of liquid phase crystallization phenomena.

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