Inorganic Fullerenes of MX2 (M=W,Mo;X=S,Se)

1994 ◽  
Vol 359 ◽  
Author(s):  
R. Tenne ◽  
L. Margulis ◽  
Y. Feldman ◽  
M. Homyonfer
Keyword(s):  
Gas Phase ◽  
Elevated Temperatures ◽  
Local Area ◽  
Phase Reaction ◽  
Flow Conditions ◽  
X Ray ◽  
Reducing Atmosphere ◽  
Preparation Conditions ◽  
Oxide Substrates ◽  
Average Size

ABSTRACTThe gas-phase reaction between MoO3-x and H2S in a reducing atmosphere and at elevated temperatures (800° to 950°C) has been used to synthesize large quantities of an almost pure nested inorganic fullerenes (IFs) phase of MoS2. A uniform IF phase with a relatively narrow size distribution was obtained. The x-ray spectra of the different samples show that as the average size of the IF decreases the van der Waals gap along the c axis increases, largely because of the strain involved in folding of the lamella. Large amount of quite uniform nanotubes were obtained under modified preparation conditions.In the second part of this work MoS2 nested fullerenes were grown on Ti and Nb and Mo oxide substrates. In one set of conditions hollow nested fullerenes of MoS2 were collected on a titanium oxide matrix, and analyzed by local area energy dispersive analysis. Under different flow conditions of the reacting gasses nested fullerenes with endohedral metal oxides were obtained and analyzed by electron diffraction.

Preparation and Optical Properties of CuS Nanofilms by a Facile Two-Step Process

2017 ◽  
Vol 16 (01) ◽  
pp. 1650021 ◽  
Author(s):  
Zhankui Cui ◽  
Junqiang Zhou ◽  
Suxiang Ge ◽  
Hongxiao Zhao
Keyword(s):  
Optical Properties ◽  
Gas Phase ◽  
Phase Reaction ◽  
Spherical Nanoparticles ◽  
X Ray Diffraction ◽  
Step Process ◽  
X Ray ◽  
Gas Phase Reaction ◽  
Composition And Structure ◽  
Lower Temperature

CuS nanofilms were prepared by a facile two-step process including chemical bath deposition of Cu nanofilms first and the subsequent thermal sulfuration step. The composition and structure of the samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and Raman spectroscopy. The optical properties of CuS nanofilms were determined by Ultraviolet-visible (UV-Vis) technique. The results show that the nanofilms composed by Cu spherical nanoparticles were completely transformed to the nanofilms composed by CuS nanosheets when the sulfuration temperature was 350[Formula: see text]C. The light absorption edges of CuS nanofilms exhibit red shift when sulfuration occurred at lower temperature. A plausible growth mechanism related with gas phase reaction for formation of CuS nanofilms was also proposed.

scholarly journals Further Studies on the Pyrolytic Domino Cyclization of Stabilized Phosphonium Ylides Bearing an Ortho-Aminophenyl Group

Molecules ◽  
2018 ◽  
Vol 23 (9) ◽  
pp. 2153 ◽  
Author(s):  
R. Aitken ◽  
Lorna Murray ◽  
Alexandra Slawin
Keyword(s):  
Gas Phase ◽  
Phenyl Group ◽  
Phase Flow ◽  
Flow Conditions ◽  
X Ray ◽  
Benzyl Radicals ◽  
C And N

Four new, stabilized phosphonium ylides containing a 2-(benzyl(methyl)amino)phenyl group have been prepared and characterized and are found, upon pyrolysis under gas-phase flow conditions, to lose Ph3PO and benzyl radicals to afford new heterocyclic products resulting from domino cyclization of both C- and N-centered radicals. Most products arise from processes of the former type and have quinoline, phenanthridine, or ring-fused phenanthridine structures, while in one case, a process of the latter type leads to a benzocarbazole product. The X-ray structure of a 2-(methyl(tosyl)amino)phenyl ylide is also reported.

Microstructure and Tensile Creep Behavior of Mg-Nd-RE-Ca Casting Alloys

2007 ◽  
Vol 345-346 ◽  
pp. 557-560 ◽  
Author(s):  
Joong Hwan Jun ◽  
Bong Koo Park ◽  
Jeong Min Kim ◽  
Ki Tae Kim ◽  
Woon Jae Jung
Keyword(s):  
Mechanical Properties ◽  
Elevated Temperatures ◽  
Tensile Creep ◽  
Secondary Creep ◽  
Creep Tests ◽  
X Ray ◽  
Casting Alloys ◽  
High Temperature Mechanical Properties ◽  
Ca Addition ◽  
Average Size

Influences of Ca addition on microstructures and mechanical properties at room and elevated temperatures have been investigated for Mg-1.5%Nd-1.0%RE-0.5%Zn-(0~1.0)%Ca casting alloys, on basis of experimental results from X-ray diffractometry (XRD), scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS), tensile and creep tests. Microstructures of the alloys are characterized by dendritic α-(Mg) grains surrounded by Mg12Nd-Zn-(Ca) eutectic network phase. The average size of α grains decreases gradually with an increase in Ca content. At room temperature, yield strength (YS) is enhanced with increasing Ca content with a decrease in ultimate tensile strength (UTS) and elongation to fracture, whereas the Ca addition leads to greater YS and UTS at 175oC. The tensile creep strain and secondary creep rate, measured at 150 and 200oC under 100MPa for 100hrs, become lower with the increase in Ca content. The obtained tensile properties at elevated temperature demonstrate that the addition of Ca plays a role in improving high temperature mechanical properties including creep resistance for the Mg-Nd-RE-Zn-(Ca) alloys. In view of microstructural evolution, this would be attributed to the refined primary α grains and higher thermal stability of the Mg12Nd-Zn-Ca eutectic strengthening phase.

Morphology, Sizes and Oxidation of Composite Copper Nanopowders, Obtained by an Electron Beam with Different Energies

2020 ◽  
Vol 310 ◽  
pp. 109-117
Author(s):  
E.Ch. Khartaeva ◽  
Andrey V. Nomoev ◽  
V.V. Syzrantsev ◽  
E.L. Dzidziguri ◽  
N.S. Khiterkheeva ◽  
...  
Keyword(s):  
Electron Beam ◽  
Gas Phase ◽  
Atmospheric Pressure ◽  
Copper Oxides ◽  
Beam Power ◽  
Phase Method ◽  
X Ray ◽  
Transmission Electron ◽  
Average Size ◽  
Copper Nanopowders

Copper nanopowders were obtained by the gas-phase method under the influence of an electron beam of different powers. Thermodynamic modeling of the phase equilibrium state of the Cu-O2-C system during heating in argon and atmospheric pressure was carried out using the TERRA software package. The obtained nanopowders of copper were studied by X-ray phase analysis and transmission electron microscopy. The morphology, structure, size distribution, and average size of copper nanoparticles are determined. The dependence of the content of copper oxides in a copper-containing nanopowder on the electron beam power has been established. It is shown that copper nanopowders obtained at high power are not oxidized.

Thermoluminescence of Cu-Doped Li2B4O7 + PTFE Annealed by Graphene Exposed to X-Rays and Gamma Radiation

2020 ◽  
pp. 2050005
Author(s):  
Swarnapriya Thiyagarajan ◽  
M. A. Vallejo ◽  
P. Cerón ◽  
C. Gomez-Solis ◽  
C. Wiechers ◽  
...  
Keyword(s):  
Heating Rate ◽  
X Rays ◽  
X Ray Diffraction ◽  
Medical Field ◽  
X Ray ◽  
Reducing Atmosphere ◽  
Linear Behavior ◽  
Good Potential ◽  
Average Size ◽  
Therapy Treatment

Lithium tetraborate (LTB) was doped with copper (0.1%) to enhance the LTB thermoluminescent (TL) properties. A graphene reducing atmosphere was used to increase the vacancies of oxygen in the crystalline structure. LTB:Cu [Formula: see text] PTFE (polytetrafluoroethylene) pellets were prepared by mixing the Li2B4O7:Cu with PTFE in a 4:1 ratio. The obtained materials were characterized by X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). Crystals of Li2B4O7 with the average size of 134[Formula: see text]nm were obtained. The presence of copper was confirmed by SEM. The TL response of LTB:Cu PTFE pellets was studied with [Formula: see text] radiation by using a [Formula: see text]Co source. TTL response shows a linear behavior depending on the radiation dose. The effect of annealing time on TL glow curve was analyzed from 2[Formula: see text]h to 10[Formula: see text]h by irradiating with X-rays. The effect of mass on the TL response was studied varying the mass of the sample from 10[Formula: see text]mg to 50[Formula: see text]mg. From various heating rate studies, it was observed that the TL intensity increased when heating rate was gradually increased. The kinetic parameters were calculated by using computer deconvolution methods. The dosimetric property results showed that this material could have good potential application in a radiation dosimeter for radiation therapy treatment in the medical field.

Photodimerization of anthracene single crystals in situ in the electron microscope

1971 ◽  
Vol 324 (1556) ◽  
pp. 37-43 ◽  
Keyword(s):  
Electron Microscope ◽  
Gas Phase ◽  
Mercury Vapour ◽  
Phase Reaction ◽  
X Ray Diffraction ◽  
X Ray ◽  
Mercury Vapour Lamp ◽  
Diffraction Patterns ◽  
Rule Out

Thin (001) plates of pure anthracene (≈ 50 nm thick in the c* direction) have been dimerized in situ in an electron microscope at approximately —100 °C by irradiating them with the 366 nm line from a mercury vapour lamp. Selected-area diffraction patterns and the corresponding bright-held micrographs show that the dianthracene forms in one of the topotactic relationships with the original anthracene encountered in X -ray diffraction studies (O’Donnell 1968), i. e. [010] A ||[010] D and [102] A ||[001] D . Crystallites of dianthracene ≈ 10 nm in diameter are formed and the photographs appear to rule out both a gas phase reaction and any kind of cooperative phenomenon involving an intermediate conversion of strings or sheets of molecules preceding final recrystallization, as found for anthracene photo-oxide (Lonsdale, Nave & Stephens 1966).

scholarly journals Continuous flow gas phase photoreforming of methanol at elevated reaction temperatures sensitised by Pt/TiO2

2016 ◽  
Vol 1 (6) ◽  
pp. 649-657 ◽  
Author(s):  
A. Caravaca ◽  
H. Daly ◽  
M. Smith ◽  
A. Mills ◽  
S. Chansai ◽  
...  
Keyword(s):  
Gas Phase ◽  
Continuous Flow ◽  
Elevated Temperatures ◽  
Flow Conditions

Gas phase photoreforming of methanol using a Pt/TiO2 photocatalyst has been performed under flow conditions at elevated temperatures.

Electron microscopy of crystalline structure in thermotropic random copolymers

1991 ◽  
Vol 49 ◽  
pp. 1054-1055
Author(s):  
Afzana Anwer ◽  
S. Eilidh Bedford ◽  
Richard J. Spontak ◽  
Alan H. Windle
Keyword(s):  
Electron Microscopy ◽  
Crystalline Structure ◽  
Liquid Crystalline ◽  
Elevated Temperatures ◽  
Random Copolymers ◽  
Molecular Characteristics ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Identical Monomer ◽  
Periodic Layer

Random copolyesters composed of wholly aromatic monomers such as p-oxybenzoate (B) and 2,6-oxynaphthoate (N) are known to exhibit liquid crystalline characteristics at elevated temperatures and over a broad composition range. Previous studies employing techniques such as X-ray diffractometry (XRD) and differential scanning calorimetry (DSC) have conclusively proven that these thermotropic copolymers can possess a significant crystalline fraction, depending on molecular characteristics and processing history, despite the fact that the copolymer chains possess random intramolecular sequencing. Consequently, the nature of the crystalline structure that develops when these materials are processed in their mesophases and subsequently annealed has recently received considerable attention. A model that has been consistent with all experimental observations involves the Non-Periodic Layer (NPL) crystallite, which occurs when identical monomer sequences enter into register between adjacent chains. The objective of this work is to employ electron microscopy to identify and characterize these crystallites.

The 3-Dimensional Molecular Structure of the Actin Filament Revisited

1985 ◽  
Vol 43 ◽  
pp. 480-481
Author(s):  
U. Aebi ◽  
R. Millonig ◽  
H. Salvo
Keyword(s):  
Actin Filament ◽  
Supramolecular Assembly ◽  
Specimen Preparation ◽  
X Ray Diffraction ◽  
Single Filament ◽  
X Ray ◽  
3 Dimensional ◽  
Filament Diameter ◽  
Preparation Conditions ◽  
Apparent Diameter

To date, most 3-D reconstructions of undecorated actin filaments have been obtained from actin filament paracrystal data (for refs, see 1,2). However, due to the fact that (a) the paracrystals may be several filament layers thick, and (b) adjacent filaments may sustantially interdigitate, these reconstructions may be subject to significant artifacts. None of these reconstructions has permitted unambiguous tracing or orientation of the actin subunits within the filament. Furthermore, measured values for the maximal filament diameter both determined by EM and by X-ray diffraction analysis, vary between 6 and 10 nm. Obviously, the apparent diameter of the actin filament revealed in the EM will critically depend on specimen preparation, since it is a rather flexible supramolecular assembly which can easily be bent or distorted. To resolve some of these ambiguities, we have explored specimen preparation conditions which may preserve single filaments sufficiently straight and helically ordered to be suitable for single filament 3-D reconstructions, possibly revealing molecular detail.

GAS PHASE X-RAY ABSORPTION SPECTROSCOPY WITH AN ELECTRON YIELD DETECTOR

1986 ◽  
Vol 47 (C8) ◽  
pp. C8-149-C8-151
Author(s):  
F. W. LYTLE ◽  
R. B. GREEGOR ◽  
G. H. VIA ◽  
J. M. BROWN ◽  
G. MEITZNER
Keyword(s):  
Gas Phase ◽  
Absorption Spectroscopy ◽  
X Ray ◽  
Electron Yield ◽  
X Ray Absorption
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