scholarly journals Synthesis, Characterization and Unusual Dielectric Behaviour of λ-Shaped Mesogenic Homologous Series With Polar Substituents

2011 ◽  
Vol 2 ◽  
pp. 16-25 ◽  
Author(s):  
P. B. Chand ◽  
R. Manohar
Keyword(s):  
Activation Energy ◽  
Homologous Series ◽  
Dielectric Behaviour ◽  
Scanning Calorimetry ◽  
Oh Groups ◽  
Smectic C ◽  
Specific Shape ◽  
Polar Substituents ◽  
Derivatives Of ◽  
Conformer Model

A new λ-shaped mesogenic homologous series with polar bromo and nitro substituent was synthesized by fixing rigid 2-bromo-4-nitrophenylazo groups to a resorcinol moiety. 4-n-alkoxybenzoyl groups esterify both the phenolic -OH groups. In the present series, methoxy and ethoxy derivatives are non-mesogenic, n-propyloxy to n-octyloxy derivatives exhibit enantiotropic nematic mesophase. Smectic C (SmC) mesophase commences from the n- octyloxy derivative as an enantiotropic phase and is retained up to the last member synthesized. The effect of polar bromo and nitro substituent on mesomorphic properties is discussed. In this paper, we also report the unusual dielectric behaviour of n-octyloxy and n-tetradecyloxy derivatives of the present λ-shaped mesogenic homologous series. The dielectric permittivity of the sample was found to be unusually low in SmC phase in comparison to nematic phase. We have explained it on the basis of two-conformer model, which can exist in SmC phase due to specific shape of the molecule. The model has been supported by calculating activation energy of both the possible conformers from Arrhenius plot of relaxation frequency versus temperature. There is a clear difference in the value of activation energy of both the conformers as expected.Keywords: C. Differential scanning calorimetry (DSC); D. Dielectric properties; D. Phase transitionsThe Himalayan Physics  Vol.2, No.2, May, 2011Page: 16-25Uploaded Date: 31 July, 2011

Experimental and Theoretical Investigations of Complex Formation of Substituted Phenylazo-Derivatives of Methylphloroglucinol

2016 ◽  
Vol 12 (8) ◽  
pp. 295-300
Author(s):  
Olga Kovalchukova ◽  
Amangdam A.T. ◽  
Strashnova S.B. ◽  
Strashnov P.V. ◽  
Romashkina E.P. ◽  
...  
Keyword(s):  
Complex Formation ◽  
Organic Ligand ◽  
Spectrophotometric Titration ◽  
Organic Ligands ◽  
Oh Groups ◽  
Tautomeric Forms ◽  
Theoretical Investigations ◽  
Derivatives Of ◽  
Theoretical Results ◽  
Titration Technique

Using spectrophotometric titration technique, the processes of complex formation of some phenylazo-derivatives of methylphloroglucinol (MPG) containing hydroxo-, nitro- and nitroso-substituents were studied. The spectral criteria of neutral and ionized forms of the organic ligands in their different tautomeric forms were determined.It was detected that the complex formation is accompanied by formation of one or two chelate cycles which involve azo- or nitroso-fragments and neighboring OH-groups of the organic ligands. Different types of coordination lead to different changes in the electronic absorption spectra.The DFT-B3LYP modeling of a Ni(II) complex of α-hydroxyphenylazo MPG established the most probable coordination mode of the organic ligand: tridentate chelating dianion, distorted square coordination of Ni-cations including one water molecule.  The theoretical results are in a good accordance with the experimental data.

Crystallization of Amorphous Silicon-Aluminum thin Films: IN-SITU Observation and Thermal Analysis.

1991 ◽  
Vol 237 ◽  
Author(s):  
Toyohiko J. Konno ◽  
Robert Sinclair
Keyword(s):  
Activation Energy ◽  
Amorphous Alloys ◽  
Amorphous Matrix ◽  
In Situ Observation ◽  
Scanning Calorimetry ◽  
Transmission Electron ◽  
High Resolution Tem ◽  
Higher Temperature ◽  
Sputter Deposited

ABSTRACTThe crystallization of sputter-deposited Si/Al amorphous alloys was examined by transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). In-situ high-resolution TEM reveals the existence of an Al layer between the amorphous matrix and the growing crystalline phase. The activation energy for the growth is about 1.2eV, roughly corresponding to the activation energy of Si diffusion in Al. These two observations support the view that a crystallization mechanism, in which an Al buffer layer provides the shortest reaction path, is responsible for the reaction. The product microstructure exhibits secondary crystallization at a higher temperature.

STUDIES ON HOMOGENEOUS FIRST ORDER GAS REACTIONS: VII. THE DECOMPOSITION OF ETHYLIDENE DIBUTYRATE AND HEPTYLIDENE DIACETATE

1937 ◽  
Vol 15b (6) ◽  
pp. 247-253 ◽  
Author(s):  
C. C. Coffin ◽  
J. R. Dacey ◽  
N. A. D. Parlee
Keyword(s):  
Activation Energy ◽  
Homologous Series ◽  
Reaction Velocity ◽  
Vapor State ◽  
Specific Reaction ◽  
First Order ◽  
Gas Reactions

Ethylidene dibutyrate and heptylidene diacetate decompose in the vapor state at temperatures between 200° and 300 °C. to form an aldehyde and an anhydride. The reactions are homogeneous, unimolecular, and complete. The activation energy is the same as that previously found for other members of this homologous series. Ethylidene dibutyrate decomposes at the same rate as ethylidene diacetate, and thus provides further evidence that the specific reaction velocity is independent of the size of the anhydride radicals. Heptylidene diacetate decomposes at the same rate as butylidene diacetate. This indicates that after the aldehyde radical has attained a certain size (three or four carbon atoms) the addition of –CH2− groups leaves the specific reaction velocity unchanged. The velocity constants are given by the equations[Formula: see text]

scholarly journals Green Preparation, Spheroidal, and Superior Property of Nano-1,3,5,7-Tetranittro-1,3,5,7-Tetrazocane

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Xinlei Jia ◽  
Jingyu Wang ◽  
Conghua Hou ◽  
Yingxin Tan
Keyword(s):  
Activation Energy ◽  
Particle Size ◽  
Fractal Dimension ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Fractal Theory ◽  
Crystal Form ◽  
Decomposition Temperature ◽  
Scanning Calorimetry ◽  
The Impact

Herein, a green process for preparing nano-HMX, mechanical demulsification shearing (MDS) technology, was developed. Nano-HMX was successfully fabricated via MDS technology without using any chemical reagents, and the fabrication mechanism was proposed. Based on the “fractal theory,” the optimal shearing time for mechanical emulsification was deduced by calculating the fractal dimension of the particle size distribution. The as-prepared nano-HMX was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and differential scanning calorimetry (DSC). And the impact sensitivities of HMX particles were contrastively investigated. The raw HMX had a lower fractal dimension of 1.9273. The ideal shearing time was 7 h. The resultant nano-HMX possessed a particle size distribution ranging from 203.3 nm to 509.1 nm as compared to raw HMX. Nano-HMX particles were dense spherical, maintaining β-HMX crystal form. In addition, they had much lower impact sensitivity. However, the apparent activation energy as well as thermal decomposition temperature of nano-HMX particles was decreased, attributing to the reduced probability for hotspot generation. Especially when the shearing time was 7 h, the activation energy was markedly decreased.

Proton spin–spin coupling constants and intramolecular hydrogen bonding in bromine derivatives of 1,3-dihydroxybenzene

1976 ◽  
Vol 54 (14) ◽  
pp. 2228-2230 ◽  
Author(s):  
Ted Schaefer ◽  
J. Brian Rowbotham
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Proton Spin ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Hydroxyl Groups ◽  
Oh Groups ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling ◽  
Derivatives Of

The conformational preferences in CCl4 solution at 32 °C of the hydroxyl groups in bromine derivatives of 1,3-dihydroxybenzene are deduced from the long-range spin–spin coupling constants between hydroxyl protons and ring protons over five bonds. Two hydroxyl groups hydrogen bond to the same bromine substituent in 2-bromo-1,3-dihydroxybenzene but prefer to hydrogen bond to different bromine substituents when available, as in 2,4-dibromo-1,3-dihydroxybenzene. When the OH groups can each choose between two ortho bromine atoms, as in 2,4,6-tribromoresorcinol, they apparently do so in a very nearly statistical manner except that they avoid hydrogen bonding to the common bromine atom.

scholarly journals THERMAL CHARACTERIZATION OF THE FAVELONE DERIVATIVES (CNIDOSCOLUS QUERCIFOLIUS) BY THERMOGRAVIMETRY AND DIFFERENTIAL SCANNING CALORIMETRY

2006 ◽  
Vol 05 (3) ◽  
pp. 8-20
Author(s):  
José Carlos Oliveira SANTOS ◽  
Lionete Dantas NUNES ◽  
Sylvia Berenice NÓBREGA ◽  
Dantas José Pires PUZINSKI ◽  
Antonio Gouveia SOUZA
Keyword(s):  
Differential Scanning Calorimetry ◽  
Arid Region ◽  
Agricultural Practices ◽  
Thermal Characterization ◽  
Northeastern Brazil ◽  
Scanning Calorimetry ◽  
Semi Arid Region ◽  
Derivatives Of ◽  
Semi Arid

A thermal analysis has been applied to characterization of food and food products. Taking into account the problems of desertification and agricultural practices able to provide income to the population at the semi-arid region of Northeastern Brazil, this work presents the results of the chemical, thermal and kinetic characterization by thermogravimetry and differential scanning calorimetry of the seed derivatives of favelone (cnidoscolus quercifolius), aiming at the application of these materials as an alternative of food source for animals and for the human population at this brazilian region.

scholarly journals Formation of metal oxide-based hydroxysodalite by alkali-activation of kaolinite

Chemija ◽  
2020 ◽  
Vol 31 (3) ◽  
Author(s):  
Ehab AlShamaileh ◽  
Muayad Esaifan ◽  
Qusay Abu-Afifeh
Keyword(s):  
Activation Energy ◽  
Metal Oxide ◽  
Alkali Activation ◽  
Dsc Analysis ◽  
X Ray Diffraction ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Xrd Study ◽  
Dsc Curves

The formation of metal oxide-based hydroxysodalite by alkali-activation of kaolinite is studied using X-ray diffraction (XRD) study and differential scanning calorimetry (DSC) analysis. Different metal oxides (CoO, MgO, FeO and SiO2) were used to form the metal oxide-based hydroxysodalite. The transformation from kaolinite into hydroxysodalite is confirmed by XRD. In the thermodynamic study, the maximum peak temperatures for DSC curves at various heating rates were used to determine the activation energy (Ea) of the hydroxysodalite formation. With magnesium oxide and cobalt oxide, the formation process was found to be exothermic while it was endothermic with iron oxide.

Characteristic of Dielectric Behaviour of Ferroelectric Liquid Crystal at Smectic-A and Chiral Smectic-C Phase Transition

1987 ◽  
Vol 56 (11) ◽  
pp. 4150-4156 ◽  
Author(s):  
Katsumi Yoshino ◽  
Kenji Nakao ◽  
Hiroki Taniguchi ◽  
Masanori Ozaki
Keyword(s):  
Phase Transition ◽  
Liquid Crystal ◽  
Dielectric Behaviour ◽  
Ferroelectric Liquid Crystal ◽  
Smectic A ◽  
Smectic C

Structural Relaxation Process in CuHfTi Amorphous Alloys

2009 ◽  
Vol 283-286 ◽  
pp. 533-538 ◽  
Author(s):  
Kazumasa Yamada ◽  
N. Shinagawa ◽  
M. Sogame ◽  
I.A. Figueroa ◽  
Hywel A. Davies ◽  
...  
Keyword(s):  
Activation Energy ◽  
Relaxation Process ◽  
Structural Relaxation ◽  
Amorphous Alloys ◽  
Melt Spinning ◽  
Amorphous Materials ◽  
Ternary Alloys ◽  
Relaxation Processes ◽  
Scanning Calorimetry ◽  
Structure Relaxation

The aim of this research is to clarify a quantitative evaluation in the structural relaxation processes focusing on the activation energy in Cu based amorphous alloys. The activation energy for structural relaxation process in a metal type amorphous CuHfTi ternary alloys, with cross sections of typically 0.03 mm x 2.0 mm, prepared by chill-block melt spinning has been investigated by Differential Scanning Calorimetry (DSC) with a cyclically heating technique. Activation energies for structural relaxation with a spatial quantity in amorphous materials have been discussed by use of a relaxed ratio function that depends on annealing temperature and time. In the present work, the distributions for the Activation Energy Spectrum (AES) were observed almost 152 kJmol-1 (1.58 eV). Another result has been also established that the “reversible” AES model energy distribution though the cyclically structure relaxation occurs even in amorphous Cu60Hf20Ti20 alloy.

Laser Damage Threshold of Hydrophobic Up-Conversion Carboxylated Nanocellulose/SrF2:Hо Composite Films Functionalized With 3-Aminopropyltriethoxysilane

2021 ◽  
Author(s):  
Anna A. Luginina ◽  
Sergey V. Kuznetsov ◽  
Vladimir K. Ivanov ◽  
Valery V. Voronov ◽  
Alexey D. Yapryntsev ◽  
...  
Keyword(s):  
Cellulose Nanofibrils ◽  
Damage Threshold ◽  
Nanocomposite Films ◽  
Laser Damage Threshold ◽  
Laser Damage ◽  
Homogeneous Distribution ◽  
Scanning Calorimetry ◽  
Long Distance ◽  
Oh Groups ◽  
X Ray

Abstract Luminescent nanocomposite films, containing SrF 2 :Но up-conversion particles, were prepared by two different protocols from aqueous dispersions of TEMPO-oxidized cellulose nanofibrils (TOCNF) functionalized with 3-aminopropyltriethoxysilane (APS) without the use of organic solvents at pH = 4.0-4.5 and 9.0-9.5, respectively. Proposed synthetic protocols included formation of the films by drying the dispersions containing pre-hydrolyzed APS adsorbed onto TOCNF and SrF 2 :Но particles followed by heating at 105 °C. Hydrophobic (water contact angle 101 ± 2°), strong, and translucent TOCNF/SrF 2 :Но-APS films were prepared by casting from a solution at pH = 4.0-4.5. Scanning electron microscopy, energy-dispersive X-ray spectroscopy with element mapping, Fourier-transform infrared spectroscopy, X-ray diffraction methods confirmed homogeneous distribution of up-conversion particles in TOCNF matrices as well as the grafting of linear polysiloxanes via the condensation of silanol groups and OH-groups on the surface of TOCNF. Differential scanning calorimetry and thermogravimetry data confirmed an increase in thermal stability of the APS modified nanocomposite films obtained at pH = 4.0-4.5. Hydrophobic TOCNF/SrF 2 :Но-APS nanocomposite films exhibited an intense red luminescence in the visible spectrum range ( 5 I 7 level excitation of Ho 3+ ions with 1912 nm laser irradiation) as well as two-times higher laser damage threshold compared to unmodified TOCNF/SrF 2 :Но films. TOCNF/SrF 2 :Но films can be used for visualization 2 μm laser radiation in medicine and long-distance atmosphere monitoring.

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