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.

Quantitative high-resolution electron microscopy (HREM) of defects in ordered polymers

1996 ◽  
Vol 54 ◽  
pp. 166-167
Author(s):  
Patricia M. Wilson ◽  
David C. Martin
Keyword(s):  
Electron Microscopy ◽  
Electron Beam ◽  
High Resolution ◽  
Liquid Crystalline ◽  
High Resolution Electron Microscopy ◽  
Polymer Materials ◽  
Scattered Electron ◽  
Crystalline Polymers ◽  
Resolution Electron ◽  
Beam Damage

Efforts in our laboratory and elsewhere have established the utility of low dose high resolution electron microscopy (HREM) for imaging the microstructure of crystalline and liquid crystalline polymers. In a number of polymer systems, direct imaging of the lattice spacings by HREM has provided information about the size, shape, and relative orientation of ordered domains in these materials. However, because of the extent of disorder typical in many polymer microstructures, and because of the sensitivity of most polymer materials to electron beam damage, there have been few studies where the contrast observed in HREM images has been analyzed in a quantitative fashion.Here, we discuss two instances where quantitative information about HREM images has been used to provide new insight about the organization of crystalline polymers in the solid-state. In the first, we study the distortion of the polymer lattice planes near the core of an edge dislocation and compare these results to theories of dislocations in anisotropic and liquid crystalline solids. In the second, we investigate the variations in HREM contrast near the edge of wedge-shaped samples. The polymer used in this study was the diacetylene DCHD, which is stable to electron beam damage (Jc = 20 C/cm2) and highly crystalline. The instrument used in this work was a JEOL 4000 EX HRTEM with a beam blanidng device. More recently, the 4000 EX has been installed with instrumentation for dynamically recording scattered electron beam currents.

Atomic chemistry by HREM and image simulations?

1986 ◽  
Vol 44 ◽  
pp. 828-829
Author(s):  
J.M. Howe ◽  
R. Gronsky
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Structural Information ◽  
High Resolution Electron Microscopy ◽  
Resolution Electron ◽  
Image Simulations

The technique of high-resolution electron microscopy (HREM) is invaluable to the materials scientist because it allows examination of microstructural features at levels of resolution that are unobtainable by most other methods. Although the structural information which can be determined by HREM and accompanying image simulations has been well documented in the literature, there have only been a few cases where this technique has been used to reveal the chemistry of individual columns or planes of atoms, as occur in segregated and ordered materials.

Insight into the Formation of Ultrafine Nanostructures in Bulk Amorphous Zr54.5 Ti7.5Al10Cu20Ni8

2001 ◽  
Vol 703 ◽  
Author(s):  
André Heinemann ◽  
Helmut Hermann ◽  
Albrecht Wiedenmann ◽  
Norbert Mattern ◽  
Uta Kühn ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Volume Fraction ◽  
High Volume ◽  
High Resolution Electron Microscopy ◽  
Scattering Data ◽  
Scanning Calorimetry ◽  
Enhanced Diffusion ◽  
Resolution Electron ◽  
The Mean ◽  
Interparticle Interference

ABSTRACTBulk amorphous Zr54.5 Ti7.5Al10Cu20Ni8 is investigated by means of smal-angle neutron scattering (SANS), differential-scanning calorimetry (DSC), high-resolution electron microscopy (HREM) and other methods. The formation of ultrafine nanostructures in the glassy phase is observed and explained by a new model. Structura fluctuations of randomly distributed partialy ordered domains grow during annealing just below the glass transition temperature by local re-ordering. During anneaing the DSC gives evidence for a increasing volume fraction of the localy ordered domains. At high volume fractions of impinging domains a percolation threshold on the interconnected domain boundaries occurs and enhanced diffusion becomes possible. At that stage SANS measurements lead to satistically significant scattering data. The SANS signals are anayzed in terms of a model taking into account spherica particles surrounded by diffusion zones and interparticle interference effects. The mean radius of the nanocrystaline particles is determined to 1 nm and the mean thickness of the depletion zone is 2 nm. The upper limit for the volume fraction after annealing at 653 K for 4hours is about 20 %. Electron microscopy confirms the size and shows that the particle are crystaline.

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 .

Trends in Atomic Resolution Electron Microscopy

1994 ◽  
Vol 332 ◽  
Author(s):  
David J. Smith ◽  
M.R. Mccartney
Keyword(s):  
Electron Microscopy ◽  
Structural Information ◽  
High Resolution Electron Microscopy ◽  
Operating Conditions ◽  
Atomic Scale ◽  
Irradiation Damage ◽  
Image Recording ◽  
Exit Surface ◽  
Resolution Electron ◽  
Image Simulations

ABSTRACTStructural information on the atomic scale is readily accessible from thin samples using the technique of high-resolution electron microscopy. Electron micrographs recorded under well-defined operating conditions can be directly interpreted in terms of atomic arrangements around defects of interest such as dislocations and interfaces. Digital image recording with slow-scan CCD cameras and quantitative comparisons with image simulations based on structural models are starting to lead to improved accuracy and reliability in structure determinations. Techniques based upon holographic methods are utilizing the superior illumination coherence of the field emission electron source to enhance resolution beyond the conventional extended Scherzer limit. Innovative methods for combining image and diffraction pattern information are also leading to improved levels of resolution for periodic objects. Care is needed to ensure that electron irradiation damage and surface cleanliness do not impose unnecessary restrictions on the details that can be extracted from recorded micrographs. It is proposed that the complex wavefunction emerging from the exit-surface of the sample should be considered as a basis for comparing the differences between experimental micrographs and image simulations.

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.

Microstructural Comparison of an Al-8.0Zn-1.8Mg-2.0Cu Alloy with Typical T6 and T76 Tempers

2018 ◽  
Vol 941 ◽  
pp. 753-758
Author(s):  
Bai Qing Xiong ◽  
Kai Wen ◽  
Yong An Zhang ◽  
Zhi Hui Li ◽  
Xi Wu Li ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Structural Information ◽  
High Resolution Electron Microscopy ◽  
Precipitate Size ◽  
Imaging Analysis ◽  
Bright Field ◽  
Transmission Electron ◽  
Resolution Electron ◽  
Precipitate Size Distribution ◽  
The Matrix

In order to analyze aging behavior of an Al-8.0Zn-1.8Mg-2.0Cu alloy, the microstructure of the alloy subjected to T6 and T76 states are investigated by transmission electron microscopy (TEM) and high-resolution electron microscopy (HREM). Based on the precipitate observations, precipitate size distributions and average precipitate size are extracted from bright-field TEM images projected along 〈110〉Alorientation with the aid of an imaging analysis. The results indicate that the main precipitates are GPI zone, GPII zone and η' phase in the T6 alloy while η' phase and η phase in the T76 alloy. The bright-field TEM observations reveal that the matrix precipitates for the T6 alloy have small size and dispersive distribution while that for the T76 alloy has big size and sparse distribution. Both have discontinuously distributed grain boundary precipitates. Quantitative structural information including precipitate size distribution and average precipitate size has been calculated by an image analysis based on the bright-field TEM images projected along 〈110〉Alorientation. The results show that the T6 alloy has a narrower precipitate size range than the T76 alloy and thus the T6 alloy possesses a smaller average precipitate size than the T76 alloy.

Electron Crystallography of Phthalocyanines

1999 ◽  
Vol 03 (07) ◽  
pp. 672-678 ◽  
Author(s):  
J. R. FRYER
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Electron Diffraction ◽  
Diffraction Data ◽  
Structural Information ◽  
High Resolution Electron Microscopy ◽  
Electron Diffraction Data ◽  
Electron Crystallography ◽  
Resolution Electron ◽  
Copper Phthalocyanines

It is shown that it is possible to obtain structural information from small (<100 nm) phthalocyanine crystals by using crystallographic direct phasing methods applied to electron diffraction data. This technique is both quantitative and does not suffer from the difficulties associated with high-resolution electron microscopy. Structural information has been obtained from both tetra- and octa chloro-copper phthalocyanines, and the results compared with the hydrogenated and perchloro members of the series.

Gallium ZSM-5 type zeolites: A catalytical and structural electron microscopy study

1988 ◽  
Vol 46 ◽  
pp. 950-951
Author(s):  
Dwight R. Acosta ◽  
Isaac Schifter ◽  
José L. Contreras
Keyword(s):  
Electron Microscopy ◽  
Structural Characteristics ◽  
High Resolution Electron Microscopy ◽  
Microscopy Study ◽  
Electron Microscopy Study ◽  
X Ray Diffraction ◽  
Modified Method ◽  
Selected Area Electron Diffraction ◽  
Resolution Electron ◽  
Cage Size

Synthesis of stereo selective zeolites using Gallium as partial or total substitute instead of aluminum, may lead to obtention of a novel class of zeo lites with modification of channel apertures, cage size and total acidity. Reaction velocity and selectivity for isomerization and cracking processes, for instance, are influenced by acid force of protonic sites, which may be selective or active for particular catalytic reactions.Zeolites Z-683 and Z-691 with a 50% and 100% of A1 atoms substituted respectively, were synthesized using a modified method for ZSM-5 zeolite crystallization as described in the literature. The samples obtained were studied using ammonia (NH3) thermodesorption techniques. X-ray diffraction, high resolution electron microscopy, selected area electron diffraction and optical diffractometry methods were used in order to determine structural characteristics of zeolites above mentioned.Figure 1 shows the results of NH3 thermodesortion studies for three zeolites: Z-601 (ZSM-5), Z-683 (50% A1 - 50% Ga) and Z-691 (100% Ga).

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