Electrical conductivity and vibrational studies induced phase transition in [N(C3H7)4]2ZnBr4 compound

Bis-Tetrapropylammonium tetrabromozincate was synthesized and characterized by X-ray powder diffraction, as well as vibrational and impedance spectroscopy. Rietveld’s refinement of X-ray diffractogram confirmed the crystallization of the compound through the monoclinic system (space group [Formula: see text]. A temperature study of Raman scattering revealed two phase transitions at approximately [Formula: see text] = 340 K and [Formula: see text] = 393 K. The wavenumber and the line width’s evolution as a function of temperature showed some peculiarities associated with these transitions, which suggests that they are governed by the reorientation of the organic part [N(C3[Formula: see text]][Formula: see text]. The complex impedance plotted as a double semicircular arc in the studied temperature range and the centers of these semicircles lie below the real axis, which indicates that the material is an on-Debye type. These semicircular arcs are related to the bulk and the grain boundary effects. Furthermore, the alternating current conductivity of [N(C3[Formula: see text]]2ZnBr4 obeyed Jonscher’s law: [Formula: see text] = [Formula: see text] and the conduction could be attributed to the correlated barrier hopping (CBH) model in both region(I) and (II) and the Non-overlapping Small Polaron Tunneling (NSPT) in region (III).

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TRANSPORT PROPERTIES OF THERMALLY EVAPORATED In2Se3 THIN FILMS

Surface Review and Letters ◽

10.1142/s0218625x09013293 ◽

2009 ◽

Vol 16 (05) ◽

pp. 723-729 ◽

Cited By ~ 6

Author(s):

D. NITHYAPRAKASH ◽

B. PUNITHAVENI ◽

J. CHANDRASEKARAN

Keyword(s):

Thin Films ◽

Dielectric Constant ◽

Ac Conductivity ◽

Thermal Evaporation ◽

Frequency Range ◽

X Ray Diffraction ◽

Cbh Model ◽

X Ray ◽

Correlated Barrier Hopping ◽

Tan Δ

Thin films of In2Se3 were prepared by thermal evaporation. X-ray diffraction indicated that the as-grown films were amorphous in nature and became polycrystalline γ-In2Se3 films after annealing. The ac conductivity and dielectric properties of In2Se3 films have been investigated in the frequency range 100 Hz–100 kHz. The ac conductivity σ ac is found to be proportional to ωn where n < 1. The temperature dependence of both ac conductivity and the parameter n is reasonably well interpreted by the correlated barrier hopping (CBH) model. The values of dielectric constant ε and loss tangent tan δ were found to increase with frequency and temperature. The ac conductivity of the films was found to be hopping mechanism. In I–V characteristic for different field and temperature were studied and it has been found that the conduction process is Poole–Frenkel type.

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X-ray diffraction study of the phase transitions of (CH3)4NCdCl3 between 293 and 80 K: a quantitative analysis of the ferroelastic domains distribution below 118 K

Acta Crystallographica Section B Structural Science ◽

10.1107/s0108768199013622 ◽

2000 ◽

Vol 56 (2) ◽

pp. 215-225 ◽

Cited By ~ 28

Author(s):

I. Peral ◽

G. Madariaga ◽

A. Pérez-Etxebarria ◽

T. Breczewski

Keyword(s):

Phase Transitions ◽

Structural Phase ◽

X Ray Diffraction ◽

Two Phase ◽

Threefold Axis ◽

X Ray ◽

Organic Part ◽

Small Distortion ◽

Diffraction Patterns ◽

Ferroelastic Domains

X-ray diffraction patterns of [N(CH_{3})_{4}][CdCl_{3}], tetramethylammonium trichlorocadmate(II), have been investigated in the temperature range 80–293 K, which includes two phase transitions at 118 and 104 K, respectively. The main interest in this compound is to establish the mechanism of the structural phase transitions common to other members of the isostructural family [(CH_{3})_{4}N][MX_{3}]. It is supposed to be related to the ordering of the organic part together with some small distortion of the inorganic chains. The origin of the order–disorder mechanism would be the orientationally disordered distribution of the tetramethylammonium tetrahedra at room temperature. Maximum Entropy Methods suggest that the most probable distribution of the organic groups can be described through the so-called two-well model, in which one threefold axis of the tetramethylammonium tetrahedron coincides with the crystallographic threefold axis of the structure. Below 118 K the reflections are split. However, the splitting cannot be fully explained by the ferroelastic domains expected to appear after the phase transitions. Recent NMR results [Mulla-Osman et al. (1998). J. Phys. Condensed Matter, 10, 2465–2476] corroborate the existence of more domains than expected from symmetry considerations. A model of ferroelastic domains which is in agreement with both X-ray diffraction diagram and NMR measurements is proposed.

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X-Ray, DSC, TGA-dTGA, and Vibrational Studies of the Propylenediammonium Hexafluorosilicate NH3(CH2)3NH3SiF6

Biointerface Research in Applied Chemistry ◽

10.33263/briac115.1261812632 ◽

2021 ◽

Vol 11 (5) ◽

pp. 12618-12632

Keyword(s):

Hydrogen Bonding ◽

Infrared Spectrum ◽

Vibrational Spectra ◽

Unit Cell Volume ◽

Site Effect ◽

Monoclinic System ◽

X Ray ◽

Dsc Measurements ◽

Vibrational Studies ◽

Cell Versus

X-ray characterization, thermal behavior, and vibrational studies have been performed on NH3(CH2)3NH3SiF6, which crystallized in the P21/c (Z = 4) monoclinic system. The V/Z ratio variation (unit cell volume/ motifs number per cell) versus the CH2 groups’ number is discussed for H3N(CH2)nNH3SiF6salts (n = 2, 3, 4, 6). The DSC measurements (heating/cooling) recorded in the 35-245°C temperature domain showed the NH3(CH2)3NH3SiF6 decomposition above 30 °C, which is checked and analyzed by TGA-dTGA techniques. The vibrational spectra interpretation is developed based on theoretical group analyses considering the +NH3(CH2)3NH3+ cations and the SiF62-anions in the C1(4) and Ci(2) symmetry sites, respectively. The SiF62-degenerated modes splitting is explained by the site effect, resulting in symmetry lowering from Oh to Ci in the crystal. The Infrared spectrum analysis at lower N-H and C-H frequencies region showed the presence of medium to strong N-HF hydrogen bonding in the title compound.

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Synthesis, Vibrational Spectroscopy and Optical Study of Bi-Tetrabutylphosphonium Hexachlorostannate

10.21203/rs.3.rs-609732/v1 ◽

2021 ◽

Author(s):

I. Mbarek ◽

M. Ben Gzaiel ◽

A. Oueslati ◽

M Gargouri

Keyword(s):

Powder Diffraction ◽

Absorption Measurement ◽

Optical Study ◽

X Ray Diffraction ◽

Two Phase ◽

Monoclinic System ◽

X Ray ◽

Optical Absorption Measurement ◽

Raman Study

Abstract The single crystals of bi-tetrabutylphosphonium hexachlorostannate were grown by solvent evaporated method and characterized by X-ray powder diffraction, Raman spectroscopy and optical study. The X-ray powder diffraction indicates that it was crystallized in the monoclinic system, with C2/c space group. Besides, temperature-controlled X-ray diffraction show that the [P(C4H9)4]2SnCl6 compound indicate the presence of two phase transitions detected at 388 and 403 K. The evolution of Raman line shifts, “ν”, and the half-width, “Δν”, versus temperature show some singularities associated with the transitions, suggesting the important role of the anionic parts ((SnCl6)2-). Besides, the results of the Raman study confirms the conclusion drawn from the X-ray powder diffraction measurements that the phase transition are located near 388K and 403K.Furthermore, an optical absorption measurement confirms the semiconductor nature with a band gap equal to 3.46eV.

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Structural Study of a new Compound Based on Acid 1,4-Cyclohexanedicarboxylic (1,4-CDC)

JOURNAL OF ADVANCES IN CHEMISTRY ◽

10.24297/jac.v6i1.969 ◽

2010 ◽

Vol 6 (1) ◽

pp. 891-896

Author(s):

Manel Halouani ◽

M. Dammak ◽

N. Audebrand ◽

L. Ktari

Keyword(s):

Aqueous Solution ◽

Water Molecules ◽

Carboxyl Group ◽

X Ray Diffraction ◽

Compound I ◽

Unit Cell Parameters ◽

Monoclinic System ◽

X Ray ◽

Cell Parameters ◽

Cyclohexanedicarboxylic Acid

One nickel 1,4-cyclohexanedicarboxylate coordination polymers, Ni2 [(O10C6H4)(COO)2].2H2O (I), was hydrothermally synthesized from an aqueous solution of Ni (NO3)2.6H2O, (1,4-CDC) (1,4-CDC = 1,4-cyclohexanedicarboxylic acid) and tetramethylammonium nitrate. Compound (I) crystallizes in the monoclinic system with the C2/m space group. The unit cell parameters are a = 20.1160 (16) Å, b = 9.9387 (10) Å, c = 6.3672 (6) Å, β = 97.007 (3) (°), V= 1263.5 (2) (Å3) and Dx= 1.751g/cm3. The refinement converged into R= 0.036 and RW = 0.092. The structure, determined by single crystal X-ray diffraction, consists of two nickel atoms Ni (1) and Ni (2). Lots of ways of which is surrounded by six oxygen atoms, a carboxyl group and two water molecules.

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Tris(pyrazolyl)borate Copper Hydroxide Complexes Featuring Tunable Intramolecular H-bonding

10.26434/chemrxiv.7878065.v1 ◽

2019 ◽

Author(s):

Evan Gardner ◽

Caitlyn Cobb ◽

Jeffery A. Bertke ◽

Timothy H. Warren

Keyword(s):

Single Crystal ◽

Copper Hydroxide ◽

X Ray ◽

Modular Synthesis ◽

Pendant Arm ◽

Copper Center ◽

Vibrational Studies

A modular synthesis provides access to a series of new tris(pyrazolyl)borate ligands XpyMeTpK that possess a single functionalized pendant pyridyl (py) or pyrimidyl (pyd) arm designed to engage in tunable intramolecular H-bonding to metal–bound functionalities. To illustrate such H-bonding interactions, a series of [XpyMeTpCu]2(𝜇–OH)2(6a–6e) complexes were synthesized from the corresponding XpyMeTpCu–OAc (5a–5e) complexes. Single crystal X-ray structures of three new dinuclear [XpyMeTpCu]2(𝜇–OH)2complexes reveal H-bonding between the pendant heterocycle and bridging hydroxide ligands while the donor arm engages the copper center in an unusual monomeric DMAPMeTpCu–OH complex. Vibrational studies (IR) of each bridging hydroxide complex reveal reduced 𝜈OH frequencies that tracks with the H-bond accepting ability of the pendant arm.

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Tris(pyrazolyl)borate Copper Hydroxide Complexes Featuring Tunable Intramolecular H-bonding

10.26434/chemrxiv.7878065 ◽

2019 ◽

Author(s):

Evan Gardner ◽

Caitlyn Cobb ◽

Jeffery A. Bertke ◽

Timothy H. Warren

Keyword(s):

Single Crystal ◽

Copper Hydroxide ◽

X Ray ◽

Modular Synthesis ◽

Pendant Arm ◽

Copper Center ◽

Vibrational Studies

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Small angle X-ray scattering study of porosity variation in a styrene-divinylbenzene copolymer

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19811675 ◽

1981 ◽

Vol 46 (7) ◽

pp. 1675-1681 ◽

Cited By ~ 13

Author(s):

Josef Baldrian ◽

Božena N. Kolarz ◽

Henrik Galina

Keyword(s):

Small Angle ◽

Structural Parameters ◽

Two Phase ◽

X Ray ◽

Porosity Variation ◽

Swelling Agent ◽

X Ray Scattering ◽

Styrene Divinylbenzene ◽

Ray Scattering

Porosity variations induced by swelling agent exchange were studied in a styrene-divinylbenzene copolymer. Standard methods were used in the characterization of copolymer porosity in the dry state and the results were compared with related structural parameters derived from small angle X-ray scattering (SAXS) measurements as developed for the characterization of two-phase systems. The SAXS method was also used for porosity determination in swollen samples. The differences in the porosity of dry samples were found to be an effect of the drying process, while in the swollen state the sample swells and deswells isotropically.

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Revisiting the Bøggild Intergrowth in Iridescent Labradorite Feldspars: Ordering, Kinetics, and Phase Equilibria

Minerals ◽

10.3390/min11070727 ◽

2021 ◽

Vol 11 (7) ◽

pp. 727

Author(s):

Shiyun Jin ◽

Huifang Xu ◽

Seungyeol Lee

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Atom Probe ◽

Phase Region ◽

Two Phase ◽

Subsolidus Phase ◽

Plagioclase Feldspar ◽

X Ray ◽

Transmission Electron ◽

Scanning Transmission

The enigmatic Bøggild intergrowth in iridescent labradorite crystals was revisited in light of recent work on the incommensurately modulated structures in the intermediated plagioclase. Five igneous samples and one metamorphic labradorite sample with various compositions and lamellar thicknesses were studied in this paper. The lamellar textures were characterized with conventional transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM). The compositions of individual lamellae were analyzed with high-resolution energy-dispersive X-ray spectroscopy (EDS) mapping and atom probe tomography (APT). The average structure states of the studied samples were also compared with single-crystal X-ray diffraction data (SC-XRD). The Na-rich lamellae have a composition of An44–48, and the Ca-rich lamellae range from An56 to An63. Significant differences between the lamellar compositions of different samples were observed. The compositions of the Bøggild intergrowth do not only depend on the bulk compositions, but also on the thermal history of the host rock. The implications on the subsolidus phase relationships of the plagioclase feldspar solid solution are discussed. The results cannot be explained by a regular symmetrical solvus such as the Bøggild gap, but they support an inclined two-phase region that closes at low temperature.

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XCOVNet: Chest X-ray Image Classification for COVID-19 Early Detection Using Convolutional Neural Networks

New Generation Computing ◽

10.1007/s00354-021-00121-7 ◽

2021 ◽

Author(s):

Vishu Madaan ◽

Aditya Roy ◽

Charu Gupta ◽

Prateek Agrawal ◽

Anand Sharma ◽

...

Keyword(s):

Image Classification ◽

Second Phase ◽

Two Phase ◽

X Ray ◽

The Neural Network ◽

Rapid Spread ◽

Chest X Ray ◽

Polymerase Chain ◽

Two Phases ◽

Active Patients

AbstractCOVID-19 (also known as SARS-COV-2) pandemic has spread in the entire world. It is a contagious disease that easily spreads from one person in direct contact to another, classified by experts in five categories: asymptomatic, mild, moderate, severe, and critical. Already more than 66 million people got infected worldwide with more than 22 million active patients as of 5 December 2020 and the rate is accelerating. More than 1.5 million patients (approximately 2.5% of total reported cases) across the world lost their life. In many places, the COVID-19 detection takes place through reverse transcription polymerase chain reaction (RT-PCR) tests which may take longer than 48 h. This is one major reason of its severity and rapid spread. We propose in this paper a two-phase X-ray image classification called XCOVNet for early COVID-19 detection using convolutional neural Networks model. XCOVNet detects COVID-19 infections in chest X-ray patient images in two phases. The first phase pre-processes a dataset of 392 chest X-ray images of which half are COVID-19 positive and half are negative. The second phase trains and tunes the neural network model to achieve a 98.44% accuracy in patient classification.

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