Dislocation mediated lattice bending in 1,6-di (N-carbazolyl)-2,4 hexadiyne (DCHD) polydiacetylene droplets

1992 ◽  
Vol 7 (11) ◽  
pp. 3150-3158 ◽  
Author(s):  
Patricia M. Wilson ◽  
David C. Martin
Keyword(s):  
Molecular Structure ◽  
Electron Microscopy ◽  
Room Temperature ◽  
High Resolution Electron Microscopy ◽  
Droplet Surface ◽  
The Core ◽  
Selected Area Electron Diffraction ◽  
Resolution Electron ◽  
Carbon Coated ◽  
Edge Dislocations

Droplets of 1,6–di (N-carbazolyl)-2,4 hexadiyne (DCHD) polydiacetylene were prepared by room temperature evaporation of dilute (0.01 wt. %) solution of the monomer in chloroform onto amorphous carbon-coated mica substrates. High Resolution Electron Microscopy (HREM) and Selected Area Electron Diffraction (SAED) revealed small crystallographically textured droplets (∼1 μm diameter) with cracks parallel to the [001] chain direction. The droplet geometry allowed us to investigate the organization of the polymer near surfaces. It was found that the curvature of the droplet edge caused a local bending of the polymer crystal lattice. Direct imaging of the molecular structure near the droplet surface revealed that the mechanism of lattice bending was by the formation of edge dislocations. Dislocations were etched in some droplets to gain information about perturbations in structure and reactivity near the core.

Electron microscopy and diffraction of crystalline dendrimers and macrocycles

1993 ◽  
Vol 51 ◽  
pp. 1218-1219
Author(s):  
C. J. Buchko ◽  
P. M. Wilson ◽  
Z. Xu ◽  
J. Zhang ◽  
S. Lee ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Liquid Crystalline ◽  
Structural Information ◽  
High Resolution Electron Microscopy ◽  
Scanning Calorimetry ◽  
Tertiary Butyl ◽  
Phenyl Acetylene ◽  
Selected Area Electron Diffraction ◽  
Liquid Crystalline Phases ◽  
Resolution Electron

The synthesis of well-defined organic molecules with unique geometries opens new opportunities for understanding and controlling the organization of condensed matter. Here, we study dendrimers and macrocycles which are synthesized from rigid phenyl-acetylene spacer units, Both units are solubilized by the presence of tertiary butyl groups located at the periphery of the molecule. These hydrocarbon materials form crystalline and liquid crystalline phases which have been studied by differential scanning calorimetry, hot stage optical microscopy, and wide-angle x-ray scattering (WAXS).The precisely defined architecture of these molecules makes it possible to investigate systematic variations in chemical architecture on the nature of microstructural organization. Here we report on the transmission electron microscopy (TEM), selected area electron diffraction (SAED), and high resolution electron microscopy (HREM) studies of crystalline thin films formed by deposition of these materials onto carbon substrates from dilute solution. Electron microscopy is very attractive for gaining structural information on new molecules due to the scarcity of material to grow single crystals suitable for conventional crystallography.

Biological control over the formation and storage of amorphous calcium carbonate by earthworms

2008 ◽  
Vol 72 (1) ◽  
pp. 227-231 ◽  
Author(s):  
M. J. I. Briones ◽  
E. López ◽  
J. Méndez ◽  
J. B. Rodríguez ◽  
L. Gago-Duport
Keyword(s):  
Electron Microscopy ◽  
Biological Control ◽  
Calcium Carbonate ◽  
Ostwald Ripening ◽  
High Resolution Electron Microscopy ◽  
Amorphous Calcium Carbonate ◽  
Concentrated Suspension ◽  
Selected Area Electron Diffraction ◽  
Resolution Electron ◽  
Glandular Secretion

AbstractThe earthworm calciferous gland produces a concentrated suspension of calcium carbonate and in certain species precipitates as concretions of CaCO3, which then enter the soil. Here we investigated the initial stages of CaCO3 formation in the earthworm Lumbricus friendi by means of Fourier transform infrared and electron microscopy techniques (field-emission scanning electron microscopy, transmission electron microscopy, high resolution electron microscopy and selected area electron diffraction). In addition, comparisons between the IR spectra of the water-dissolved carbonic anhydrase (CA) and the glandular secretion (‘milky fluid’) were performed in order to investigate the mechanisms involved in CaCO3 precipitation. Our results strongly suggest that carbonation starts with the dissolved CO2, which is transformed via deprotonation to HCO3-, then to CO32- and finally to amorphous calcium carbonate (ACC). While ACC stabilization takes place under the biological control, further transformation stages leading to calcite concretions seem to be inorganically driven by an Ostwald ripening process.

Orientation Relationship between Fe2M and Martensite in M50NiL Steel

2013 ◽  
Vol 456 ◽  
pp. 533-536
Author(s):  
Yan Zhi Lou
Keyword(s):  
Crystal Structure ◽  
Electron Microscopy ◽  
High Resolution ◽  
Electron Diffraction ◽  
Orientation Relationship ◽  
High Resolution Electron Microscopy ◽  
Lattice Parameters ◽  
Selected Area Electron Diffraction ◽  
Resolution Electron ◽  
Martensite Matrix

In this paper, high resolution electron microscopy (HREM) was used to observe nanosized Fe2M precipitates in M50NiL steel, and crystal structure of which was also investigated by selected area electron diffraction (SAED). At the same time, the orientation relationship between the Fe2M and the martensite matrix was also studied. The results suggested that crystal structure of Fe2M is close-packed hexagonal, and lattice parameters about a=b=0.473nm, c=0.772nm, α=β=90°, γ=120°. The orientation relationship between the nanoprecipitates Fe2M and martensite is and .

Microstructure of epitaxial VO2 thin films deposited on (1120) sapphire by MOCVD

1994 ◽  
Vol 9 (9) ◽  
pp. 2264-2271 ◽  
Author(s):  
H. Zhang ◽  
H.L.M. Chang ◽  
J. Guo ◽  
T.J. Zhang
Keyword(s):  
Electron Microscopy ◽  
Thin Films ◽  
Deposition Temperature ◽  
Room Temperature ◽  
High Resolution Electron Microscopy ◽  
Sapphire Substrates ◽  
Resolution Electron ◽  
Initial Nucleation ◽  
Vo2 Thin Films ◽  
Conventional Electron Microscopy

Epitaxial VO2 thin films grown on (1120) sapphire (α-Al2O3) substrates by MOCVD at 600 °C have been characterized by conventional electron microscopy and high resolution electron microscopy (HREM). Three different epitaxial relationships between the monoclinic VO2 films and sapphire substrates have been found at room temperature: I. (200) [010] monoclinic VO2 ‖ (1120) [0001] sapphire, II. (002) [010] monoclinic VO2 ‖ (1120) [0003] sapphire, and III. (020) [102] monoclinic VO2 ‖ (1120) [0001] sapphire. Expitaxial relationships II and III are equivalent to each other when the film possesses tetragonal structure at the deposition temperature; i.e., they can be described as (010) [100] tetragonal VO2 ‖ (1120) [0001] sapphire and (100) [010] tetragonal VO2 ‖ (1120) [0001] sapphire. HREM image shows that the initial nucleation of the film was dominated by the first orientation relationship, but the film then grew into the grains of the second and the third (equivalent to each other at the deposition temperature) epitaxial relationships. Successive 90°transformation rotational twins around the a-axis are commonly observed in the monoclinic films.

New nonhydrolytic route to synthesize crystalline BaTiO3 nanocrystals with surface capping ligands

2006 ◽  
Vol 21 (12) ◽  
pp. 3187-3195 ◽  
Author(s):  
Zhuoying Chen ◽  
Limin Huang ◽  
Jiaqing He ◽  
Yimei Zhu ◽  
Stephen O'Brien
Keyword(s):  
Electron Microscopy ◽  
Barium Titanate ◽  
Oleyl Alcohol ◽  
High Resolution Electron Microscopy ◽  
Decanoic Acid ◽  
Nonpolar Solvents ◽  
Selected Area Electron Diffraction ◽  
Resolution Electron ◽  
Capping Ligands ◽  
20 Nm

A new nonhydrolytic route for the preparation of well-crystallized size-tunable barium titanate (BaTiO3) nanocrystals capped with surface ligands is reported. Our approach involves: (i) synthesizing a “pseudo” bimetallic precursor, and (ii) combining the as-synthesized bimetallic precursor with a mixture of oleylamine with different surface coordinating ligands at 320 °C for crystallization and crystal growth. Different alcohols in the precursor synthesis and different carboxylic acids were used to study the effect of size and morphological control over the nanocrystals. Nanocrystals of barium titanate with diameters of 6–10 nm (capped with decanoic acid), 3–5 nm (capped with oleic acid), 10–20 nm (a nanoparticle and nanorod mixture capped with oleyl alcohol), and 2–3 nm (capped with oleyl alcohol) were synthesized, and can be easily dispersed into nonpolar solvents such as hexane or toluene. Techniques including x-ray diffraction, transmission electron microscopy, selected area electron diffraction, and high-resolution electron microscopy confirm the crystallinity and morphology of these as-synthesized nanocrystals.

Atomic structure of CdTe dislocations studied by HREM

1989 ◽  
Vol 47 ◽  
pp. 576-577
Author(s):  
P. Lu ◽  
R.W. Glaisher ◽  
David J. Smith
Keyword(s):  
Electron Microscopy ◽  
Ion Beam ◽  
High Resolution Electron Microscopy ◽  
Resolution Limit ◽  
The Core ◽  
Partial Dislocations ◽  
Resolution Electron ◽  
Argon Ion ◽  
Image Simulations

The determination of the atomic core of dislocations in semiconductors is a challenging problem for high-resolution electron microscopy(HREM). In previous studies, various defects in elemental semiconductors, III-V and II-VI compound semiconductors have been reported. In particular, the core structure of the 30° partial dislocations in silicon, which are dissociated from a perfect 60° dislocation, have been deduced. present study, various CdTe dislocations have been imaged at 400keV. and their core structures have been analyzed with assistance from multi-slice image simulations. Sections of CdTe single crystal were cut normal to the [110] direction, followed by mechanically polishing to a thickness of ˜ 20 microns and finally argon ion-beam milling to perforation for electron microscopy. The crystals were examined with a JEM-4000EX. having a structure resolution limit of ˜ 1.7Å at 400keV.

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