Far-infrared powder spectrum of (N(CH3)3D)(I)(TCNQ)

1983 ◽  
Vol 61 (9) ◽  
pp. 1271-1277 ◽  
Author(s):  
J. E. Eldridge ◽  
Normand Fortier ◽  
Frances E. Bates ◽  
J. S. Miller
Keyword(s):  
Phase Transition ◽  
Absorption Spectrum ◽  
Transition Temperature ◽  
Theoretical Analysis ◽  
Temperature Effects ◽  
Far Infrared ◽  
Second Phase ◽  
Powder Spectrum ◽  
Absorption Features ◽  
Group Theoretical Analysis

We present the powder absorption spectrum of (TMA)(I)(TCNQ) in the far-infrared as a function of temperature. Below 160 K new absorption features appear and others increase in intensity. This behaviour supports the electron- and neutron-diffraction evidence of a distortion on the TCNQ chains below the first phase-transition temperature. Effects due to the second phase transition at 89 K are also observed. The results of a group-theoretical analysis are presented. These show that totally-symmetric internal modes ag are to be expected in the infrared spectra of this compound even in the undistorted phase.

Ferroelasticity of SrCo0.8Fe0.2O3–δperovskite-related oxide with mixed ion–electron conductivity

2015 ◽  
Vol 48 (1) ◽  
pp. 179-188 ◽  
Author(s):  
I. Belenkaya ◽  
A. Matvienko ◽  
A. Nemudry
Keyword(s):  
Phase Transition ◽  
Theoretical Analysis ◽  
Mechanical Load ◽  
Electron Conductivity ◽  
Transmission Electron ◽  
Lamellar Texture ◽  
The Common ◽  
Common Nature ◽  
Means Of Transmission ◽  
Group Theoretical Analysis

A group-theoretical analysis was carried out to determine the possible orientation states of domains formed as a result of the `perovskite–brownmillerite' phase transition in SrCo0.8Fe0.2O2.5oxide with mixed ion–electron conductivity (MIEC). The results of the theoretical analysis agree with the experimental data obtained in the study of the SrCo0.8Fe0.2O2.5microstructure by means of transmission electron microscopy. Brownmillerite SrCo0.8Fe0.2O2.5(BM) has a lamellar texture composed of 90° twins 60–260 nm in size; the 〈010〉BMand 〈101〉BMdirections are linked through twinning in accordance with the predictions of the group-theoretical analysis. The presence of twins and their switching under mechanical load provide evidence that the perovskite–brownmillerite phase transition in SrCo0.8Fe0.2O2.5is ferroelastic. Comparative analysis of the phenomena observed for ferroelectrics and MIEC oxides indicates their similarity based on the common nature of ferroelectricity and ferroelasticity, and allows us to suppose that nonstoichiometric SrCo0.8Fe0.2O3−δwith compositional disorder may be considered (in terms of its microstructural features) a `relaxor ferroelastic'.

Microstructural Evolution of Nuclear Power Steel A508-III in the Creep Process at 800°C

2016 ◽  
Vol 853 ◽  
pp. 153-157
Author(s):  
Zhi Gang Xie ◽  
Yan Ming He ◽  
Jian Guo Yang ◽  
Zeng Liang Gao
Keyword(s):  
Electron Microscopy ◽  
Phase Transition ◽  
Grain Size ◽  
Transition Temperature ◽  
Phase Transition Temperature ◽  
Microstructural Evolution ◽  
Creep Process ◽  
Second Phase ◽  
Creep Stage ◽  
Second Phase Particles

The A508-III steel is widely used to manufacture the lower heads of commercial reactor pressure vessels (RPV). In severe accident, the reactor core in the RPV begins to melt and meanwhile the technology of in-vessel retention (IVR) exerts its role. In this case the inner surface of RPV will expose to temperatures over a phase transition temperature. However, the significant nonlinear feature of creep curve of A508-III steel suffered heterogeneous damage was not studied. In this work, the creep tests were performed for the steel at the phase transition temperature of 800°C. The microstructural evolution at different creep stages was characterized by scanning electron microscopy and transmission electron microscopy. The results show that, at the second creep stage, more coarsening second phase particles occur in the steel. With the creep processing, the grain size and diameter of second phase particles increase. At the tertiary creep stage, the grain size increases significantly, and the second phase particles coarsen during the process of atom migration. In addition, Micro-cracks and voids also come into being in the situation and they can become larger by combing each other during the creep process. At this stage, the growth of cavities and second phase particles coarsening become the main mechanism of creep damage. The trend of microstructural evolution is consistent with the creep constitutive equation obtained for the A508-III steel at the phase transition temperature of 800°C. The results obtained provide indispensable foundation to establish the relationship between the macroscopic creep and microscopic damage.

Crystal field splitting in the far infrared spectrum of rhombic sulfur

1969 ◽  
Vol 47 (14) ◽  
pp. 2713-2715 ◽  
Author(s):  
A. Anderson ◽  
L. Y. Wong
Keyword(s):  
Theoretical Analysis ◽  
Infrared Spectrum ◽  
Crystal Field ◽  
Far Infrared ◽  
Unit Cell ◽  
Crystal Field Splitting ◽  
Lattice Vibrations ◽  
Normal Coordinate ◽  
Thin Polycrystalline ◽  
Group Theoretical Analysis

The infrared (i.r.) spectra of thin polycrystalline samples of orthorhombic sulfur at 95 °K in the range 50–500 cm−1 have been recorded. The three i.r. active fundamentals ν4, ν5, and ν6 are observed to be split into 2,3, and 3 components, respectively, as predicted from a group theoretical analysis of the unit cell symmetry, thus confirming the assignment of ν4 and ν6. Several weaker absorptions are assigned by comparison with recent Raman results and a normal coordinate analysis. No peaks assignable to lattice vibrations are observed.

Temperature effects and the observation of the B2u lattice mode in the far infrared absorption spectrum of polyethylene

1972 ◽  
Vol 17 (1) ◽  
pp. 84-85 ◽  
Author(s):  
J.W. Fleming ◽  
G.W. Chantry ◽  
P.A. Turner ◽  
Elisabeth A. Nicol ◽  
H.A. Willis ◽  
...  
Keyword(s):  
Absorption Spectrum ◽  
Infrared Absorption ◽  
Temperature Effects ◽  
Infrared Absorption Spectrum ◽  
Far Infrared ◽  
Lattice Mode

The structure of membranes and membrane proteins embedded in amorphous ice

1992 ◽  
Vol 50 (1) ◽  
pp. 432-433
Author(s):  
Uwe Lücken ◽  
Joachim Jäger
Keyword(s):  
Phase Transition ◽  
Transition Temperature ◽  
Membrane Proteins ◽  
Phase Transition Temperature ◽  
Lipid Vesicles ◽  
Freezing Stress ◽  
Amorphous Ice ◽  
Different Temperatures ◽  
Band Pass ◽  
Lipid Polymorphism

TEM imaging of frozen-hydrated lipid vesicles has been done by several groups Thermotrophic and lyotrophic polymorphism has been reported. By using image processing, computer simulation and tilt experiments, we tried to learn about the influence of freezing-stress and defocus artifacts on the lipid polymorphism and fine structure of the bilayer profile. We show integrated membrane proteins do modulate the bilayer structure and the morphology of the vesicles.Phase transitions of DMPC vesicles were visualized after freezing under equilibrium conditions at different temperatures in a controlled-environment vitrification system. Below the main phase transition temperature of 24°C (Fig. 1), vesicles show a facetted appearance due to the quasicrystalline areas. A gradual increase in temperature leads to melting processes with different morphology in the bilayer profile. Far above the phase transition temperature the bilayer profile is still present. In the band-pass-filtered images (Fig. 2) no significant change in the width of the bilayer profile is visible.

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