Stabilisation of Aragonite: The Role of Mg2+ and Other Impurity Ions

Crystal Formation ◽

Sulfate Ions ◽

Inorganic Systems ◽

Sodium Magnesium ◽

Stable Product ◽

The Stability ◽

Backscatter Diffraction ◽

First Time

Aragonite formation and stabilisation in seawater is still an area of active investigation since the thermodynamically stable product at room temperature is calcite. In this manuscript, purely inorganic systems that were found to stabilise aragonite were analysed by various techniques. Dynamic Light Scattering was used to characterise the nucleation behaviour of the system and it was found that the presence of magnesium ions during crystal formation inhibits nucleation overall, not just calcite nucleation. In addition, it was found that sulfate is not necessary to stabilise aragonite. Microanalysis by energy dispersive X-ray spectroscopy (EDS) and electron backscatter diffraction (EBSD) revealed that the aragonite that was formed had a disordered core with, sodium, magnesium and sulfate ions incorporated into the structure. To the best of the authors’ knowledge this is the first time an ACC core in aragonite has been visualised in a completely abiotic, synthetic system (in the absence of organic molecules). Inclusion of these impurities into the structure may explain the stability of aragonite in natural seawaters.

Using electron backscatter diffraction to measure full crystallographic orientation in Antarctic land-fast sea ice

Journal of Glaciology ◽

10.1017/jog.2018.67 ◽

2018 ◽

Vol 64 (247) ◽

pp. 771-780 ◽

Cited By ~ 3

Author(s):

PAT WONGPAN ◽

DAVID J. PRIOR ◽

PATRICIA J. LANGHORNE ◽

KATHERINE LILLY ◽

INGA J. SMITH

Keyword(s):

Sea Ice ◽

Crystallographic Orientation ◽

Preferred Orientation ◽

Angle Distribution ◽

Crystal Preferred Orientation ◽

Electron Backscatter ◽

Backscatter Diffraction ◽

First Time ◽

Platelet Ice

ABSTRACTWe have mapped the full crystallographic orientation of sea ice using electron backscatter diffraction (EBSD). This is the first time EBSD has been used to study sea ice. Platelet ice is a feature of sea ice near ice shelves. Ice crystals accumulate as an unconsolidated sub-ice platelet layer beneath the columnar ice (CI), where they are subsumed by the advancing sea–ice interface to form incorporated platelet ice (PI). As is well known, in CI the crystal preferred orientation comprises dominantly horizontal c-axes, while PI has c-axes varying between horizontal and vertical. For the first time, this study shows the a-axes of CI and PI are not random. Misorientation analysis has been used to illuminate the possible drivers of these alignments. In CI the misorientation angle distribution from random pairs and neighbour pairs of grains are indistinguishable, indicating the distributions are a consequence of crystal preferred orientation. Geometric selection during growth will develop the a-axis alignment in CI if ice growth in water is fastest parallel to the a-axis, as has previously been hypothesised. In contrast, in PI random-pair and neighbour-pair misorientation distributions are significantly different, suggesting mechanical rotation of crystals at grain boundaries as the most likely explanation.

Protein crystal lattices are dynamic assemblies: the role of conformational entropy in the protein condensed phase

IUCrJ ◽

10.1107/s2052252517017833 ◽

2018 ◽

Vol 5 (2) ◽

pp. 130-140 ◽

Cited By ~ 5

Author(s):

Margarita Dimova ◽

Yancho D. Devedjiev

Keyword(s):

Condensed Phase ◽

Protein Structures ◽

Van Der Waals Interactions ◽

Protein Crystal ◽

Crystal Formation ◽

Conformational Entropy ◽

Crystal Lattices ◽

Crystal Contacts ◽

First Time

Until recently, the occurrence of conformational entropy in protein crystal contacts was considered to be a very unlikely event. A study based on the most accurately refined protein structures demonstrated that side-chain conformational entropy and static disorder might be common in protein crystal lattices. The present investigation uses structures refined using ensemble refinement to show that although paradoxical, conformational entropy is likely to be the major factor in the emergence and integrity of the protein condensed phase. This study reveals that the role of shape entropy and local entropic forces expands beyond the onset of crystallization. For the first time, the complete pattern of intermolecular interactions by protein atoms in crystal lattices is presented, which shows that van der Waals interactions dominate in crystal formation.

A Role of Low Energy Grain Boundaries in the Abnormal Grain Growth in Fe-3%Si Alloy

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.127.89 ◽

2011 ◽

Vol 127 ◽

pp. 89-94 ◽

Cited By ~ 4

Author(s):

Ye Chao Zhu ◽

Jiong Hui Mao ◽

Fa Tang Tan ◽

Xue Liang Qiao

Keyword(s):

Grain Boundaries ◽

Grain Growth ◽

Dominant Role ◽

Coincidence Site Lattice ◽

Diffraction Method ◽

Abnormal Grain Growth ◽

Low Energy ◽

Low energy grain boundaries were considered to be important in abnormal grain growth by theoretical deduction. The disorientation angles and coincidence site lattice grain boundaries distribution of more than 20 Goss grains and their neighboring matrix grains in primary recrystallized Fe-3%Si alloy were investigated using an electron backscatter diffraction method. It was found that the frequency of low energy grain boundaries of Goss grains which are more likely to abnormally grow are higher than their neighboring matrix grains, which indicated that low energy grain boundaries play a dominant role in the abnormal grain growth of Fe-3%Si alloy. The result meets well with the abnormal grain growth theory.

Growth of 4H-SiC Single Crystals on 6H-SiC Seeds with an Open Backside by PVT Method

Materials Science Forum ◽

10.4028/www.scientific.net/msf.615-617.15 ◽

2009 ◽

Vol 615-617 ◽

pp. 15-18 ◽

Cited By ~ 7

Author(s):

Emil Tymicki ◽

Krzysztof Grasza ◽

Katarzyna Racka ◽

Marcin Raczkiewicz ◽

Tadeusz Łukasiewicz ◽

...

Keyword(s):

Single Crystals ◽

Structural Defects ◽

X Ray Diffraction ◽

Force Microscopy ◽

Optical Scanning ◽

Atomic Force ◽

The Stability ◽

Backscatter Diffraction ◽

Source Materials

4H-SiC single crystals grown by the seeded physical vapour transport method have been investigated. These crystals were grown on 6H-SiC seeds. The influence of the seed temperature, form and granulation of SiC source materials on the stability and efficiency of the 4H polytype growth have been investigated. A new way of the seed mounting - with an open backside - has been used. Crystals obtained were free of structural defects in the form of hexagonal voids. The crystalline structure of SiC crystals was investigated by EBSD (Electron Backscatter Diffraction) and X-Ray diffraction methods. Moreover, defects in crystals and wafers cut from these crystals were examined by optical, scanning electron and atomic force microscopy combined with KOH etching.

Temperature-Dependent Mechanical Stability of Retained Austenite in Thermomechanically Processed 3Mn Steel

Materials Science Forum ◽

10.4028/www.scientific.net/msf.1016.762 ◽

2021 ◽

Vol 1016 ◽

pp. 762-767

Author(s):

Aleksandra Kozłowska ◽

Adam Grajcar ◽

Aleksandra Janik ◽

Krzysztof Radwański

Keyword(s):

Retained Austenite ◽

Mechanical Stability ◽

Tensile Tests ◽

Trip Effect ◽

X Ray Diffraction ◽

Temperature Dependent ◽

Static Tensile ◽

The Stability ◽

The temperature-dependent mechanical stability of retained austenite in medium-Mn transformation induced plasticity 0.17C-3.3Mn-1.6Al-1.7Al-0.22Si-0.23Mo thermomechanically processed steel was investigated using scanning electron microscopy (SEM), electron backscatter diffraction (EBSD) and X-ray diffraction (XRD) methods. Specimens were deformed up to rupture in static tensile tests in a temperature range 20–200°C. It was found that deformation temperature affects significantly the intensity of TRIP effect. In case of specimens deformed at temperatures higher than 60°C, a gradual temperature-related decrease in the stability of γ phase was noted. It indicates a progressive decrease of the significance of the TRIP effect and at the same time the growing importance of the thermally activated processes affecting a thermal stability of retained austenite.

Grain Refinement by Extension Twin in Mg Alloy during Asymmetrical Rolling

Metals ◽

10.3390/met8110891 ◽

2018 ◽

Vol 8 (11) ◽

pp. 891 ◽

Cited By ~ 1

Author(s):

I Widiantara ◽

Hae Yang ◽

Muhammad Kamil ◽

Dong Yoon ◽

Young Ko

Keyword(s):

Grain Refinement ◽

Surface Region ◽

Mg Alloy ◽

Speed Ratio ◽

Asymmetrical Rolling ◽

Present Sample ◽

Refinement Process ◽

The work looked into the grain refinement process of Mg alloy during asymmetrical rolling with a focus on the role of twin. The present sample was deformed at ambient temperature by single operation with the height reduction of 50% at the roll speed ratio of 1:4 for the upper and lower rolls having the same dimension. From the electron backscatter diffraction analysis in the surface region where intense shear strain was imparted, a number of { 10 1 ¯ 2 } extension twins with a width of ~1 µm were detected clearly in most of the deformed grains. Moreover, the average misorientation angle of the deformed grains in the top region was found to be ~32°, which was two times higher than that in the center area where the extension twin was detected rarely. As a result, the microstructure in the top region was refined significantly down to be ~1.1 µm with an aid of twin activities that would be discussed in this study.

Key Parameters to Promote Granularization of Lath-Like Bainite/Martensite in FeNiC Alloys during Isothermal Holding

Materials ◽

10.3390/ma11101808 ◽

2018 ◽

Vol 11 (10) ◽

pp. 1808

Author(s):

Meriem Ben Haj Slama ◽

Nathalie Gey ◽

Lionel Germain ◽

Kangying Zhu ◽

Sébastien Allain

Keyword(s):

Isothermal Holding ◽

Lower Bainite ◽

Ferrite Matrix ◽

Granular Bainite ◽

Orientation Data ◽

Isothermal Ageing ◽

The Stability ◽

The stability of lath-like microstructures during low-temperature isothermal ageing was analyzed in a Fe5Ni0.33C (in wt %) steel. The microstructures were characterized using Scanning Electron Microscopy (SEM) coupled with Electron Backscatter Diffraction (EBSD). Advanced orientation data processing was applied to quantify the hierarchical and multiscale organization of crystallographic variants subdividing Prior Austenite Grains (PAG) into packets/blocks/sub-blocks. The result shows that ferrite laths of martensite or lower bainite are stable, whatever the ageing temperature (up to 380 °C). On the contrary, a granularization process is triggered when microstructures contain a fraction of upper bainite. This metallurgical evolution corresponds to a rapid and significant change of the ferrite matrix involving a disappearance of 60° disoriented blocks. The phenomenon affects in turn the mechanical properties. The final microstructures obtained after isothermal holding look like granular bainite, which raises some questions about the classification of bainite.

The Role of Cations of the Precipitant in the Interaction of Protein Molecules in the Lysozyme Oligomers in Crystallization Solutions

Crystals ◽

10.3390/cryst11121534 ◽

2021 ◽

Vol 11 (12) ◽

pp. 1534

Author(s):

Yuliya V. Kordonskaya ◽

Vladimir I. Timofeev ◽

Yulia A. Dyakova ◽

Margarita A. Marchenkova ◽

Yury V. Pisarevsky ◽

...

Keyword(s):

Protein Crystallization ◽

Structural Transformations ◽

Atomic Mass ◽

Crystal Formation ◽

Noticeable Effect ◽

Protein Molecules ◽

The Stability ◽

The Moment ◽

Dynamics Method

At the moment, the main opinion is that protein crystallization depends mainly on the the precipitant anions, therefore, there have been only few works devoted to the problem of the influence of its cations. Using the molecular dynamics method, we investigated the stability, changes in the compactness and structural transformations of lysozyme dimers and octamers in solutions with different precipitants (LiCl, NaCl, KCl and CuCl2) in order to study the contribution of cations during crystal formation in more detail. As a result, we found that cations have a rather noticeable effect on the behavior of oligomers: the higher the atomic mass of the cation, the greater the changes in the dimers structures during its dynamics and, according to the data of SAXS experiments, the lower the concentration of dimers. However, for octamers, this dependence is more complicated.

First evidence of formation of stable DBU Zn-phthalocyanine complexes: synthesis and characterization

Journal of Porphyrins and Phthalocyanines ◽

10.1142/s1088424605000630 ◽

2005 ◽

Vol 09 (07) ◽

pp. 519-527 ◽

Cited By ~ 10

Author(s):

Roberta Del Sole ◽

Agnese De Luca ◽

Giuseppe Mele ◽

Giuseppe Vasapollo

Keyword(s):

Thermal Analysis ◽

Axial Ligand ◽

Synthesis And Characterization ◽

One Pot ◽

Strong Base ◽

Pyridine Complex ◽

The Stability ◽

First Time ◽

Complex Thermal Analysis

Novel Zn (II) phthalocyanine and naphthalocyanine DBU complexes have been prepared in a one-pot synthesis reacting phthalonitrile precursors with an excess of DBU (1,8-diazabicyclo[5.4.0]undec-7-ene). For the first time, it has been well evidenced that DBU played the role of coordinating axial ligand together with the well known role of strong base. Also, DBU complexes showed better solubility in organic solvents due to the coordination of the bulky axial DBU ligand, compared to the Zn (II) phthalocyanines and naphthalocyanines without coordinated DBU. The coordinating properties of DBU toward ZnPcs (DBU free) complexes have also been investigated along with the ZnPc (pyridine) complex. Thermal analysis results reflecting the stability of the synthesized complexes under air are also presented.