Single crystal hydrostatic compression of (Mg,Mn,Fe,Co) 2 SiO 4 olivines

1998 ◽  
Vol 25 (4) ◽  
pp. 308-312 ◽  
Author(s):  
Li Zhang
Keyword(s):  
Single Crystal ◽  
Hydrostatic Compression

Molecular dynamics study on void collapse in single crystal hcp-Ti under hydrostatic compression

2020 ◽  
Vol 171 ◽  
pp. 109280 ◽  
Author(s):  
Qian Xu ◽  
Wen Li ◽  
Jianxin Zhou ◽  
Yajun Yin ◽  
Hai Nan ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Single Crystal ◽  
Hydrostatic Compression

scholarly journals Reversibility in a Plastically Flexible Coordination Polymer Crystal: A High-Pressure Study

2020 ◽  
Author(s):  
Xiaojiao Liu ◽  
Adam Michalchuk ◽  
Biswajit Bhattacharya ◽  
Franziska Emmerling ◽  
Colin R. Pulham
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Coordination Polymer ◽  
Single Crystal ◽  
Structural Phase ◽  
Low Frequency ◽  
Hydrostatic Compression ◽  
Three Point Bending ◽  
Flexible Material ◽  
Plastic Materials

<p>Single crystals which exhibit mechanical flexibility are promising materials for advanced technological applications. Before such materials can be used, detailed understanding of the mechanisms and structural effects of bending are needed. Coordination polymer single crystal represent a fascinating class of mechanically flexible material; their bending contradicts existing models. Using single crystal X-ray diffraction and microfocus Raman spectroscopy, we study in atomic detail the high-pressure response of the plastically flexible coordination polymer [Zn(μ‐Cl)<sub>2</sub>(3,5‐dichloropyridine)<sub>2</sub>]<i><sub>n</sub>.</i> In stark contrast to three-point bending, the quasi-hydrostatic compression of the single crystal is completely reversible, even following compression to over 9 GPa. A structural phase transition is observed at <i>ca. </i>5 GPa. <i>Ab initio</i> DFT calculations show this transition to result from the pressure-induced softening of low frequency vibrations. This phase transition is not observed during three-point bending. Our combined experimental and theoretical high-pressure investigation propose slight compression at low levels of bending. However, our studies provide the first indication of overall disparate mechanical responses of bulk flexibility and quasi-hydrostatic compression. We suspect this to be a general feature of mechanically plastic materials. <b></b></p>

scholarly journals Influence of Temperature on Void Collapse in Single Crystal Nickel under Hydrostatic Compression

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2369
Author(s):  
Mahesh R. G. Prasad ◽  
Anupam Neogi ◽  
Napat Vajragupta ◽  
Rebecca Janisch ◽  
Alexander Hartmaier
Keyword(s):  
Single Crystal ◽  
Strain Hardening ◽  
Elevated Temperatures ◽  
Hot Isostatic Pressing ◽  
Dislocation Motion ◽  
Hydrostatic Compression ◽  
Dislocation Network ◽  
Nickel Base Superalloy ◽  
Dislocation Loops ◽  
Ambient Temperatures

Employing atomistic simulations, we investigated the void collapse mechanisms in single crystal Ni during hydrostatic compression and explored how the atomistic mechanisms of void collapse are influenced by temperature. Our results suggest that the emission and associated mutual interactions of dislocation loops around the void is the primary mechanism of void collapse, irrespective of the temperature. The rate of void collapse is almost insensitive to the temperature, and the process is not thermally activated until a high temperature (∼1200–1500 K) is reached. Our simulations reveal that, at elevated temperatures, dislocation motion is assisted by vacancy diffusion and consequently the void is observed to collapse continuously without showing appreciable strain hardening around it. In contrast, at low and ambient temperatures (1 and 300 K), void collapse is delayed after an initial stage of closure due to significant strain hardening around the void. Furthermore, we observe that the dislocation network produced during void collapse remains the sample even after complete void collapse, as was observed in a recent experiment of nickel-base superalloy after hot isostatic pressing.

scholarly journals Reversibility in a Plastically Flexible Coordination Polymer Crystal: A High-Pressure Study

2020 ◽  
Author(s):  
Xiaojiao Liu ◽  
Adam Michalchuk ◽  
Biswajit Bhattacharya ◽  
Franziska Emmerling ◽  
Colin R. Pulham
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Coordination Polymer ◽  
Single Crystal ◽  
Structural Phase ◽  
Low Frequency ◽  
Hydrostatic Compression ◽  
Three Point Bending ◽  
Flexible Material ◽  
Plastic Materials

<p>Single crystals which exhibit mechanical flexibility are promising materials for advanced technological applications. Before such materials can be used, detailed understanding of the mechanisms and structural effects of bending are needed. Coordination polymer single crystal represent a fascinating class of mechanically flexible material; their bending contradicts existing models. Using single crystal X-ray diffraction and microfocus Raman spectroscopy, we study in atomic detail the high-pressure response of the plastically flexible coordination polymer [Zn(μ‐Cl)<sub>2</sub>(3,5‐dichloropyridine)<sub>2</sub>]<i><sub>n</sub>.</i> In stark contrast to three-point bending, the quasi-hydrostatic compression of the single crystal is completely reversible, even following compression to over 9 GPa. A structural phase transition is observed at <i>ca. </i>5 GPa. <i>Ab initio</i> DFT calculations show this transition to result from the pressure-induced softening of low frequency vibrations. This phase transition is not observed during three-point bending. Our combined experimental and theoretical high-pressure investigation propose slight compression at low levels of bending. However, our studies provide the first indication of overall disparate mechanical responses of bulk flexibility and quasi-hydrostatic compression. We suspect this to be a general feature of mechanically plastic materials. <b></b></p>

A Preparation of High Resolution Standards for Electron Microscopy. Part II

1971 ◽  
Vol 29 ◽  
pp. 160-161
Author(s):  
Akira Tanaka ◽  
David F. Harling
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Carbon Black ◽  
Single Crystal ◽  
Dark Field ◽  
Graphitized Carbon Black ◽  
Graphitized Carbon ◽  
Dark Field Imaging ◽  
Crystal Films ◽  
Micro Holes

In the previous paper, the author reported on a technique for preparing vapor-deposited single crystal films as high resolution standards for electron microscopy. The present paper is intended to describe the preparation of several high resolution standards for dark field microscopy and also to mention some results obtained from these studies. Three preparations were used initially: 1.) Graphitized carbon black, 2.) Epitaxially grown particles of different metals prepared by vapor deposition, and 3.) Particles grown epitaxially on the edge of micro-holes formed in a gold single crystal film.The authors successfully obtained dark field micrographs demonstrating the 3.4Å lattice spacing of graphitized carbon black and the Au single crystal (111) lattice of 2.35Å. The latter spacing is especially suitable for dark field imaging because of its preparation, as in 3.), above. After the deposited film of Au (001) orientation is prepared at 400°C the substrate temperature is raised, resulting in the formation of many square micro-holes caused by partial evaporation of the Au film.

Structure of Palladium Single-Crystal Films Prepared by Flash Evaporation onto (001) NaCl Substrates

1970 ◽  
Vol 28 ◽  
pp. 456-457
Author(s):  
L. E. Murr ◽  
G. Wong
Keyword(s):  
Single Crystal ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
High Rate ◽  
Flash Evaporation ◽  
Optimum Load ◽  
Single Crystal Films ◽  
Crystal Films ◽  
A Current

Palladium single-crystal films have been prepared by Matthews in ultra-high vacuum by evaporation onto (001) NaCl substrates cleaved in-situ, and maintained at ∼ 350° C. Murr has also produced large-grained and single-crystal Pd films by high-rate evaporation onto (001) NaCl air-cleaved substrates at 350°C. In the present work, very large (∼ 3cm2), continuous single-crystal films of Pd have been prepared by flash evaporation onto air-cleaved (001) NaCl substrates at temperatures at or below 250°C. Evaporation rates estimated to be ≧ 2000 Å/sec, were obtained by effectively short-circuiting 1 mil tungsten evaporation boats in a self-regulating system which maintained an optimum load current of approximately 90 amperes; corresponding to a current density through the boat of ∼ 4 × 104 amperes/cm2.

Dislocations, Ordering and Antiferromagnetic Domains in MnO

1970 ◽  
Vol 28 ◽  
pp. 522-523
Author(s):  
D. J. Barber ◽  
R. G. Evans
Keyword(s):  
Electron Diffraction ◽  
Single Crystal ◽  
Optical Microscopy ◽  
Defect Chemistry ◽  
Magnetic Structures ◽  
Optically Transparent ◽  
Magnetic Features ◽  
Antiferromagnetic Domains

Manganese (II) oxide, MnO, in common with CoO, NiO and FeO, possesses the NaCl structure and shows antiferromagnetism below its Neel point, Tn∼ 122 K. However, the defect chemistry of the four oxides is different and the magnetic structures are not identical. The non-stoichiometry in MnO2 small (∼2%) and below the Tn the spins lie in (111) planes. Previous work reported observations of magnetic features in CoO and NiO. The aim of our work was to find explanations for certain resonance results on antiferromagnetic MnO.Foils of single crystal MnO were prepared from shaped discs by dissolution in a mixture of HCl and HNO3. Optical microscopy revealed that the etch-pitted foils contained cruciform-shaped precipitates, often thick and proud of the surface but red-colored when optically transparent (MnO is green). Electron diffraction and probe microanalysis indicated that the precipitates were Mn2O3, in contrast with recent findings of Co3O4 in CoO.

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