Variable temperature PXRD investigation of the phase changes during the dehydration of potassium Tutton salts

AbstractA design is described for a variable-temperature diffractometer specimen mount developed internally in the Physics Laboratory of Materials Central. Temperature capability of 1600°C is achieved using Indirect radiation heating. Higher temperatures may be obtained by directly heating the sample. An adaptation allows operation at temperatures as low as −196°C and is useful for studying low-temperature phase changes and examining materials normally liquid at room temperature. The mount operates in vacuum or inert atmosphere. A full 180° 2θ scanning range is possible through the use of curved beryllium- or aluminum-foil windows. Realignment of the sample at temperature and under vacuum may be accomplished from four points around the front plate of the mount. Only two vacuum seals are used In this mount in addition to the window seal and thermocouple seals. Power for the mount is high current, low voltage, and is controlled by an automatic temperature regulator and sensing device which maintains an accurate preset temperature.Applications of variable temperature techniques on refractory metals, alloys, and compounds are shown, along with an example of low-temperature effects in materials normally liquid at room temperature.

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Structure and Dielectric Behavior of Yb2O3-MgO Co-Doped 0.92BaTiO3-0.08(Na0.5Bi0.5)TiO3 Ferroelectric Relaxor

Materials ◽

10.3390/ma14226802 ◽

2021 ◽

Vol 14 (22) ◽

pp. 6802

Author(s):

Xiao-Hu Ren ◽

Dong-Yun Gui

Keyword(s):

Variable Temperature ◽

Dielectric Behavior ◽

Phase Changes ◽

Core Shell ◽

Shell Microstructure ◽

Temperature Dependent ◽

Raman Analysis ◽

Ferroelectric Relaxor ◽

Dielectric Peak ◽

Xrd And Tem

Dielectric properties and structure of 0.015Yb2O3-xMgO doped 0.92BaTiO3-0.08(Na0.5Bi0.5)TiO3 ceramics with x = 0.0–0.025 have been investigated. As Yb2O3-MgO was added into the BT-NBT, the phase changes from tetragonal to pseudo-cubic, with the tetragonality c/a decreases from 1.011 to 1.008 and XRD peaks broadened. The combined study of XRD and TEM image revealed a formation of core–shell structure in grains with core of 400–600 nm and the shell of a thickness 60–200 nm. There is a slowly phase transition against temperature from the variable temperature Raman analysis. The ferroelectric relaxor peak of BT-NBT decreases from ~4000 to ~2000 and a new broad dielectric peak with an equivalent maximum (εr′~2300) appears in the temperature dependent dielectric constant curve (εr′-T), which produces a flat εr′-T curve. Sample 0.92BaTiO3-0.08(Na0.5Bi0.5)TiO3-0.015Yb2O3-0.005 MgO and 0.92BaTiO3-0.08(Na0.5Bi0.5)TiO3-0.015Yb2O3-0.01MgO give a εr′ variation within ±14% and ±10% in 20–165 °C. The core–shell microstructure should take account for the flattened εr′–T behavior of these samples.

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Understanding the complex structural features and phase changes in Na2Mg2(SO4)3: A combined single crystal and variable temperature powder diffraction and Raman spectroscopy study

Journal of Solid State Chemistry ◽

10.1016/j.jssc.2019.02.014 ◽

2019 ◽

Vol 272 ◽

pp. 157-165 ◽

Cited By ~ 6

Author(s):

I.A. Trussov ◽

L.L. Male ◽

M.L. Sanjuan ◽

A. Orera ◽

P.R. Slater

Keyword(s):

Raman Spectroscopy ◽

Single Crystal ◽

Powder Diffraction ◽

Variable Temperature ◽

Structural Features ◽

Phase Changes ◽

Spectroscopy Study ◽

Complex Structural

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The Interpretation of Crystal Lattice Images

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010009600x ◽

1972 ◽

Vol 30 ◽

pp. 550-551

Author(s):

J. M. Cowley ◽

Sumio Iijima

Keyword(s):

Crystal Orientation ◽

Diffraction Theory ◽

Phase Changes ◽

Electron Wave ◽

Crystal Lattices ◽

Heavy Atoms ◽

Lattice Images ◽

The Right ◽

Intuitive Interpretation ◽

Suitable Approximation

The imaging of detailed structures of crystal lattices with 3 to 4Å resolution, given the correct conditions of microscope defocus and crystal orientation and thickness, has been used by Iijima (this conference) for the study of new types of crystal structures and the defects in known structures associated with fluctuations of stoichiometry. The image intensities may be computed using n-beam dynamical diffraction theory involving several hundred beams (Fejes, this conference). However it is still important to have a suitable approximation to provide an immediate rough estimate of contrast and an evaluation of the intuitive interpretation in terms of an amplitude object.For crystals 100 to 150Å thick containing moderately heavy atoms the phase changes of the electron wave vary by about 10 radians suggesting that the “optimum defocus” theory of amplitude contrast for thin phase objects due to Scherzer and others can not apply, although it does predict the right defocus for optimum imaging.

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Remote diagnostics of vibrations of dynamic objects by Doppler microwave sensors

Metrologiya ◽

10.32446/0132-4713.2020-3-25-42 ◽

2020 ◽

pp. 25-42

Author(s):

Dmitrii V. Khablov

Keyword(s):

Intelligent Systems ◽

Electromagnetic Waves ◽

Continuous Monitoring ◽

Phase Changes ◽

Vibration Diagnostics ◽

Remote Diagnostics ◽

Active Vibration ◽

Dynamic Objects ◽

Microwave Sensors ◽

Non Destructive

This paper describes a promising method for non-contact vibration diagnostics based on the use of Doppler microwave sensors. In this case, active irradiation of the object with electromagnetic waves and the allocation of phase changes using two-channel quadrature processing of the received reflected signal are used. The modes of further fine analysis of the resulting signal using spectral or wavelet transformations depending on the nature of the active vibration are considered. The advantages of this non-contact and remote vibration analysis method for the study of complex dynamic objects are described. The convenience of the method for machine learning and use in intelligent systems of non-destructive continuous monitoring of the state of these objects by vibration is noted.

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Self-Assembly of Hydrogels From Elastin-Mimetic Block Copolymers

MRS Proceedings ◽

10.1557/proc-724-n8.1 ◽

2002 ◽

Vol 724 ◽

Author(s):

Elizabeth R. Wright ◽

R. Andrew McMillan ◽

Alan Cooper ◽

Robert P. Apkarian ◽

Vincent P. Conticello

Keyword(s):

Block Copolymers ◽

Self Assembly ◽

Triblock Copolymers ◽

Variable Temperature ◽

Inverse Temperature ◽

Temperature Transition ◽

Scanning Calorimetry ◽

Design Synthesis ◽

Inverse Temperature Transition ◽

Functional Biomaterials

AbstractTriblock copolymers have traditionally been synthesized with conventional organic components. However, triblock copolymers could be synthesized by the incorporation of two incompatible protein-based polymers. The polypeptides would differ in their hydrophobicity and confer unique physiochemical properties to the resultant materials. One protein-based polymer, based on a sequence of native elastin, that has been utilized in the synthesis of biomaterials is poly (Valine-Proline-Glycine-ValineGlycine) or poly(VPGVG) [1]. This polypeptide has been shown to have an inverse temperature transition that can be adjusted by non-conservative amino acid substitutions in the fourth position [2]. By combining polypeptide blocks with different inverse temperature transition values due to hydrophobicity differences, we expect to produce amphiphilic polypeptides capable of self-assembly into hydrogels. Our research examines the design, synthesis and characterization of elastin-mimetic block copolymers as functional biomaterials. The methods that are used for the characterization include variable temperature 1D and 2D High-Resolution-NMR, cryo-High Resolutions Scanning Electron Microscopy and Differential Scanning Calorimetry.

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