Effect of chiral alkyl groups on the structural-phase transition of ferroelectric liquid crystals investigated by differential scanning calorimetry, x-ray diffraction, and infrared/Raman spectroscopic methods

1992 ◽  
Vol 96 (6) ◽  
pp. 2729-2735 ◽  
Author(s):  
Jianan Hou ◽  
Kohji Tashiro ◽  
Masamichi Kobayashi
Keyword(s):  
Phase Transition ◽  
Differential Scanning Calorimetry ◽  
Structural Phase ◽  
Spectroscopic Methods ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Ferroelectric Liquid Crystals ◽  
X Ray ◽  
Raman Spectroscopic ◽  
Alkyl Groups

Differential scanning calorimetry and X-ray diffraction studies of a series of synthetic β-D-galactosyl diacylglycerols

1991 ◽  
Vol 69 (12) ◽  
pp. 863-867 ◽  
Author(s):  
D. A. Mannock ◽  
R. N. McElhaney
Keyword(s):  
Phase Transition ◽  
Differential Scanning Calorimetry ◽  
Phase Behaviour ◽  
Lipid Phase ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Phase Transition Temperatures ◽  
Bonding Properties ◽  
Lower Temperature

We have investigated the physical properties of a homologous series of synthetic, saturated 1,2-di-O-acyl-3-O-(β-D-galactopyranosyl)-sn-glycerols using calorimetry and X-ray diffraction. Unannealed aqueous dispersions of these compounds exhibit a lower temperature, moderately energetic, chain-melting (Lβ/Lα phase transition and a higher temperature, weakly energetic, bilayer/nonbilayer phase transition. On annealing below the Lβ/Lα phase transition, the Lβ phase converts to an LC phase, which may undergo a highly energetic LC/Lα or LC/HII phase transition at very high temperatures on reheating. The temperatures of these phase transitions are higher than those seen in the corresponding α- and β-D-glucosyl diacylglycerols. However, the Lβ/Lα and bilayer/nonbilayer phase transition temperatures of the β-D-galactosyl diacylglycerols are lower than those of the corresponding diacyl phosphatidylethanolamines. These observations are discussed in terms of the hydration and hydrogen bonding properties of their respective headgroups.Key words: differential scanning calorimetry, low-angle x-ray diffraction, glycolipids, galactolipids, lipid phase behaviour.

scholarly journals Phase Transition and Melt-Recrystallization Behavior of Poly(Butylene Adipate) Investigated by Simultaneous Measurements of Wide-Angle X-Ray Diffraction (WAXD) and Differential Scanning Calorimetry (DSC)

Polymers ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 75
Author(s):  
Mengfan Wang ◽  
Weiyu Cao
Keyword(s):  
Phase Transition ◽  
Differential Scanning Calorimetry ◽  
Heating Process ◽  
Wide Angle ◽  
Melt Crystallization ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Β Phase ◽  
Simultaneous Measurements

Simultaneous measurements of wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC) were carried out to investigate the phase transition and melting behaviors of poly(butylene adipate) (PBA). Thermal expansion changes along the a and b axes of the β form unit cell are different from each other during the heating process. At the beginning of the β to αH (high-temperature α phase) phase transition, the β phase melts very fast, while the recrystallization of the αH phase is delayed and slowed. With the further increment of the temperature, the melting rate of the β phase slows down, while the recrystallization of the αH phase accelerates. The diffraction peak intensity ratios of the β(020):β(110) and αH(020):αH(110) diffraction peaks during the first heating process have similar value. However, the above value is different from the value of α(020):α(110) during the following melt-crystallization process. This difference comes from the different orientations of the crystal lattices of the α and αH(β) crystals to the substrate plane, which indicates that the αH phase inherits the orientation of the β phase during phase transition and the orientation of αH form crystals is different from the α form crystals that crystallized from the melt.

Structural Phase Transition of Tungsten-Doped Vanadium Dioxide Nanopowders Prepared by Thermolysis

2008 ◽  
Vol 8 (3) ◽  
pp. 1417-1421 ◽  
Author(s):  
Zifei Peng ◽  
Wei Jiang ◽  
Heng Liu
Keyword(s):  
Phase Transition ◽  
Differential Scanning Calorimetry ◽  
Transition Temperature ◽  
Vanadium Dioxide ◽  
Structural Phase ◽  
Hysteresis Loops ◽  
Tungstic Acid ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Transmission Electron

Tungsten-doped vanadium dioxide (VO2) nanopowders were prepared by thermolysis of (NH4)5[(VO)6(CO3)4(OH)9] · 10H2O at low temperature, with active white powdery tungstic acid used as a substitutional dopant. The composition and microstructure of the powders were examined by X-ray diffraction, transmission electron microscope, and differential scanning calorimetry. The change in electrical resistance due to the S–M transition was measured from 0 to 150 °C by the four-probe method. Hysteresis loops and differential scanning calorimetry analysis of the samples indicated that the phase-transition temperature of VO2 nanopowders was 67.15 °C. For tungstendoped VO2 nanopowders, the temperature was reduced to 26.46 °C. After sintering the nanopowders, Tc rose from 26.46 °C to 34.85 °C with the sizes increasing to the bulk. A significant direct correlation between particle size and Tc was confirmed. The results indicated that white powdery tungstic acid is exceptionally effective as a dopant for reducing transition temperature.

Low-temperature phase transition in glycine–glutaric acid co-crystals studied by single-crystal X-ray diffraction, Raman spectroscopy and differential scanning calorimetry

2012 ◽  
Vol 68 (3) ◽  
pp. 287-296 ◽  
Author(s):  
Boris A. Zakharov ◽  
Evgeniy A. Losev ◽  
Boris A. Kolesov ◽  
Valeri A. Drebushchak ◽  
Elena V. Boldyreva
Keyword(s):  
Phase Transition ◽  
Differential Scanning Calorimetry ◽  
Raman Spectroscopy ◽  
Single Crystal ◽  
Glutaric Acid ◽  
Group Symmetry ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray

The occurrence of a first-order reversible phase transition in glycine–glutaric acid co-crystals at 220–230 K has been confirmed by three different techniques – single-crystal X-ray diffraction, polarized Raman spectroscopy and differential scanning calorimetry. The most interesting feature of this phase transition is that every second glutaric acid molecule changes its conformation, and this fact results in the space-group symmetry change from P21/c to P\bar 1. The topology of the hydrogen-bonded motifs remains almost the same and hydrogen bonds do not switch to other atoms, although the hydrogen bond lengths do change and some of the bonds become inequivalent.

scholarly journals Inorganic Anion Regulates the Phase Transition in Two Organic Cation Salts Containing [(4-Nitroanilinium)(18-crown-6)]+ Supramolecules

2017 ◽  
Author(s):  
Yuan Chen ◽  
Yang Liu ◽  
Binzu Gao ◽  
Chuli Zhu ◽  
Zunqi Liu
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Variable Temperature ◽  
Structural Phase ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Space Group ◽  
X Ray

Two novel inorganic–organic hybrid supramolecular assemblies, namely, (4-HNA)(18-crown-6)(HSO4) (1) and (4-HNA)2(18-crown-6)2(PF6)2(CH3OH) (2) (4-HNA = 4-nitroanilinium), were synthesized and characterized by infrared spectroscopy, single X-ray diffraction, differential scanning calorimetry (DSC), and temperature-dependent dielectric measurements. The two compounds underwent reversible phase transitions at about 255 K and 265 K, respectively. These phase transitions were revealed and confirmed by the thermal anomalies in DSC measurements and abrupt dielectric anomalies during heating. The phase transition may have originated from the [(4-HNA)(18-crown-6)]+ supramolecular cation. The inorganic anions tuned the crystal packings and thus influenced the phase-transition points and types. The variable-temperature X-ray diffraction data for crystal 1 revealed the occurrence of a phase transition in the high-temperature phase with the space group of P21/c and in the low-temperature phase with the space group of P21/n. Crystal 2 exhibited the same space group P21/c at different temperatures. The results indicated that crystals 1 and 2 both underwent an iso-structural phase transition.

scholarly journals Phase transition behavior and deformation mechanism of polytetrafluoroethylene under stretching

RSC Advances ◽  
2021 ◽  
Vol 11 (63) ◽  
pp. 39813-39820
Author(s):  
Cong Luo ◽  
Jingke Pei ◽  
Wenyue Zhuo ◽  
Yanhua Niu ◽  
Guangxian Li
Keyword(s):  
Phase Transition ◽  
Differential Scanning Calorimetry ◽  
Small Angle ◽  
Deformation Mechanism ◽  
X Ray Diffraction ◽  
Phase Transition Behavior ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Transition Behavior ◽  
X Ray Scattering

The deformation mechanism and phase transition behavior of polytetrafluoroethylene (PTFE) under stretching conditions (25, 50, 100 °C) were investigated by using differential scanning calorimetry (DSC), small angle X-ray scattering (SAXS), and X-ray diffraction (XRD).

scholarly journals Structural phase transition of ternary dielectric SmGdO3: Evidence from angle dispersive x-ray diffraction and Raman spectroscopic studies

2015 ◽  
Vol 117 (9) ◽  
pp. 094101 ◽  
Author(s):  
Yogesh Sharma ◽  
Satyaprakash Sahoo ◽  
A. K. Mishra ◽  
Pankaj Misra ◽  
Shojan P. Pavunny ◽  
...  
Keyword(s):  
Phase Transition ◽  
Structural Phase Transition ◽  
Structural Phase ◽  
Spectroscopic Studies ◽  
X Ray Diffraction ◽  
X Ray ◽  
Raman Spectroscopic

Differential Scanning Calorimetry and Guinier Camera/High-Temperature X-Ray Diffraction Studies of the Oxygen Sublattice Phase Transition in the Yba2Cu3O7−x System

1987 ◽  
Vol 99 ◽  
Author(s):  
David S. Lee ◽  
Zezhong Fu ◽  
Egon Hellstern ◽  
William L. Johnson ◽  
Paul Pietrokowsky ◽  
...  
Keyword(s):  
Phase Transition ◽  
Activation Energy ◽  
Differential Scanning Calorimetry ◽  
High Temperature ◽  
Chemical Potential ◽  
X Ray Diffraction ◽  
Oxygen Sublattice ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Xrd Techniques

ABSTRACTWe have studied the phase transition of the oxygen sublattice in the YBa2Cu3O7−x system by Differential Scanning Calorimetry (DSC), Guinier Camera, and high temperature x-ray diffraction (ht-xrd) techniques. The transition was examined under different thermodynamic constraints (constant oxygen partial pressure and constant oxygen concentration) and for a range of oxygen partial pressures. The variation of the endothermic peak temperature with DSC scanning rate was used to deduce an activation energy for the transition. The average activation energy for the process is between 38.7–75.0 kcal/mole(l:2:3) [mole], depending on the thermodynamic constraint imposed on the system.Pressure versus concentration isotherms (P(C)) were used to determine the chemical potential of the oxygen in this system.

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