PVT Measurements on 4-n-Pentyl-4´-Cyano-Biphenyl (5CB) and trans-4-(4´-Octyl-Cyclohexyl)-Benzonitrile (8PCH) up to 300 MPa

1997 ◽  
Vol 52 (10) ◽  
pp. 739-747 ◽  
Author(s):  
M. Sandmann ◽  
F. Hamann ◽  
A. Würflinger
Keyword(s):  
Liquid Crystalline ◽  
Solid Phase ◽  
Melting Curve ◽  
Entropy Change ◽  
Isotropic Phase ◽  
Enthalpy Changes ◽  
Metastable Form ◽  
Pvt Measurements ◽  
Crystal Phases ◽  
Specific Volumes

Abstract Specific volumes are presented for 4-n-pentyl-4´-cyanobiphenyl (5CB) and trans-4-(4´-octyl-cyclo-hexyl)-benzonitrile (8PCH) for temperatures between 300 and 370 K up to 300 MPa. The p,Vm ,T data were determined for the liquid crystalline and isotropic phases, and partly also for the solid phase adjacent to the melting curve. Stable and metastable crystal phases can be distinguished. The density and melting temperature of the metastable form are lower than for the stable one. Volume and enthalpy changes accompanying the phase transitions are reported as well. The p,Vm ,T data allow to calculate the entropy change for a hypothetical transition at constant volume. The molar volumes along the nematic-isotropic phase transition TNI (p) allow to determine the molecular field parameter γ = ∂In TNI /∂ In VNI.

PVT Measurements on 4'-w-Hexyl-Biphenyl-4-Carbonitrile (6CB) and 4'-w-Heptyl-Biphenyl-4-Carbonitrile (7CB) up to 300 MPa

1998 ◽  
Vol 53 (5) ◽  
pp. 233-238 ◽  
Author(s):  
M. Sandmann ◽  
A. Würflinger
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Liquid Crystalline ◽  
Entropy Change ◽  
Isotropic Phase ◽  
Enthalpy Changes ◽  
Dependent Part ◽  
Pvt Measurements ◽  
Crystal Phases ◽  
Specific Volumes

Abstract P, Vm , T data were established for 4'-n-hexyl-biphenyl-4-carbonitrile (6CB) and 4'-n-heptyl-biphenyl-4-carbonitrile (7CB) between 300 and 370 K up to 300 MPa, and specific volumes were determined for the liquid crystalline, isotropic, and also partly for the crystal phases. Volume and enthalpy changes at the phase transitions are also presented. In the case of 6CB, a new crystal phase has been detected, corresponding to a triple point at 338 K and 196 MPa. The p, Vm , T data enabled us to separate the entropy change into a volume-dependent part and configurational part. From the molar volumes along the nematic-isotropic phase transition TNl(p), the molecular field parameter γ=∂lnTNI/∂lnVNI was determined.

Differential Thermal Analysis and PVT Measurements on 2,2,2-Trichloro-ethanol Under High Pressure

1997 ◽  
Vol 52 (6-7) ◽  
pp. 493-501 ◽  
Author(s):  
M. Jenau ◽  
M. Sandmann ◽  
A. Würflinger ◽  
J. Ll. Tamarit
Keyword(s):  
Thermal Analysis ◽  
Differential Thermal Analysis ◽  
Atmospheric Pressure ◽  
Solid Phase ◽  
Melting Curve ◽  
Phase Behaviour ◽  
Enthalpy Changes ◽  
Pvt Measurements ◽  
Plastic Phase ◽  
Lower Temperature

Abstract The phase behaviour, the calorimetric and volumetric properties of 2,2,2-trichloro-ethanol (TCE) have been studied with differential thermal analysis (DTA) and pVT measurements in the pressure range 1 atm to 300 MPa and temperatures between 250 K to 355 K. TCE displays a metastable plastic phase (solid I') and a non-plastic solid phase II at atmospheric pressure. At least two pressure-induced solid phases have been detected: a stable plastic phase (solid I') and a non-plastic phase (solid III). There are two sets of triple points: a) 123 MPa and 308 K with the phases solid I, solid II and the liquid, b) 243 MPa and 316 K for solid I, II, III. Furthermore a metastable low-temperature brittle form (solid II') has been found, which transforms to solid I at a considerably lower temperature than solid II. The melting curve of solid I' can be pursued to higher pressures up to 260 MPa. On the other hand, the melting curve of the stable plastic phase solid I can be extrapolated beyond the triple point to pressures below 123 MPa. Volume and enthalpy changes are reported for all phase transitions.

pVT Measurements and Related Studies on the Binary System nC16H34 -nC17H36 and on nC18H38 at High Pressures

2001 ◽  
Vol 56 (9-10) ◽  
pp. 626-634 ◽  
Author(s):  
Albert Würflinger ◽  
Denise Mondieig ◽  
Fazil Rajabalee ◽  
Miquel Angel Cuevas-Diarte
Keyword(s):  
Binary System ◽  
Specific Volume ◽  
Transition Point ◽  
Binary Systems ◽  
High Pressures ◽  
Ambient Pressure ◽  
Melting Curve ◽  
Enthalpy Changes ◽  
Rotator Phase ◽  
Pvt Measurements

Abstract The phase diagram of the binary system nC16H34 -nC17H36 has been established at ambient pressure using DSC and crystallographic measurements. At low temperatures below the rotator phase RI there exist two crystal forms Op (about x(C17) = 0.25) and Mdci (about x(C17) = 0.67) which are different from the crystal structures of the pure compounds (Tp for C16 and Oi for C17). Furthermore two compositions: (a) C16/C17 = 3:1 and (b) = 1:2, which correspond to the coexistence range of Op and Mdci, were chosen for high pressure DTA and pVT measurements, yielding the following findings: The specific volume of the rotator phase of C17 is distinctly lower than those of the binary systems at the same state point. Assuming the existence of a metastable rotator phase for C16, an excess volume of Δ VE/V ≈ 0.01 can be estimated. Due to the very enlarged coexistence range of RI, the mixtures reach their lower transition point at considerably lower temperatures (in isobaric measurements) or higher pressures (in isothermal measurements), where the specific volume is lower than that of C17 at its transition point. Furthermore, the volume and enthalpy changes of the Φord -RI transition is distinctly smaller for the binary systems than for pure C17. Thus the specific volumes of the phases Op and Mdci are appreciably larger than ν(spec.) of C17. Op and Mdci have practically the same specific volume in accordance with the crystallographic results. Enthalpy values are obtained with the aid of the Clausius-Clapeyron equation which agree well with enthalpies derived from the DSC measurements. Furthermore, pVT data have been established for the liquid and solid phases of nC18H38 in the neighbourhood of the melting curve, allowing to determine volume and enthalpy changes of melting as a function of pressure.

PVT and DTA Measurements on trans-4-n-Hexyl- (4'-Cyanophenyl)-Cyclohexane (6PCH) up to 300 MPa

1999 ◽  
Vol 54 (5) ◽  
pp. 281-286 ◽  
Author(s):  
M. Sandmann ◽  
F. Hamann ◽  
A. Würflinger
Keyword(s):  
Thermal Analysis ◽  
Phase Diagram ◽  
High Pressure ◽  
Differential Thermal Analysis ◽  
Phase Transitions ◽  
Melting Curve ◽  
Enthalpy Changes ◽  
Volume Entropy ◽  
Solid Phases ◽  
Specific Volumes

The phase diagram of trans-4-n-hexyl-(4'-cyanophenyl)-cyclohexane, (6PCH) has been established by high-pressure differential thermal analysis. Specific volumes are presented for temperatures between 300 and 370 K up to 300 MPa. The p,Vm ,T data have been determined for the nematic, isotropic, and (partly, in the neighbourhood to the melting curve) solid phases. Volume and enthalpy changes along the phase transitions have also been calculated. As previously, the p,Vm,T data were used to calculate the volume entropy for the nematic-isotropic transition. The molar volumes along the clearing line TNI (p) enabled us to calculate the molecular field parameter γ = ∂ln TNI/∂In VNI , being 4.1.

Thermal phase transition behaviours of the blue phase of bent-core nematogen and chiral dopant mixtures under different boundary conditions

Soft Matter ◽  
2014 ◽  
Vol 10 (41) ◽  
pp. 8224-8228 ◽  
Author(s):  
Min-Jun Gim ◽  
Gohyun Han ◽  
Suk-Won Choi ◽  
Dong Ki Yoon
Keyword(s):  
Phase Transition ◽  
Boundary Conditions ◽  
Liquid Crystalline ◽  
Isotropic Phase ◽  
Different Boundary Conditions ◽  
Various Boundary Conditions ◽  
Thermal Phase Transition ◽  
Thermal Phase ◽  
Blue Phase ◽  
Chiral Dopants

We have investigated dramatic changes in the thermal phase transition of a liquid-crystalline (LC) blue phase (BP) consisting of bent-core nematogen and chiral dopants under various boundary conditions during cooling from the isotropic phase.

scholarly journals Perylene-like Dyes in Liquid Crystalline Media

1996 ◽  
Vol 51 (7) ◽  
pp. 843-850 ◽  
Author(s):  
Ewa Mykowska ◽  
Danuta Bauman
Keyword(s):  
Phase Transition ◽  
Transition Temperature ◽  
Order Parameter ◽  
Liquid Crystalline ◽  
Fluorescent Dyes ◽  
Liquid Crystal Display ◽  
Isotropic Phase ◽  
Display Devices ◽  
Electrooptical Properties ◽  
Derivatives Of

Abstract The spectral and electrooptical properties of some dichroic fluorescent dyes (derivatives of 3.4,9,10-perylenetetracorboxylic acid and of 3,4,9-perylenetricarboxylic acid) in isotropic solvents and nematic liquid crystals have been studied. The order parameter of the dyes in the anisotropic matrices has been determined by means of optical spectroscopy methods. Moreover, the influence of the dye addition on the nematic-isotropic phase transition temperature of the pure host has been investigated. It was found that some of the dyes studied can be utilized in guest-host liquid crystal display devices.

scholarly journals Melting of iron determined by X-ray absorption spectroscopy to 100 GPa

2015 ◽  
Vol 112 (39) ◽  
pp. 12042-12045 ◽  
Author(s):  
Giuliana Aquilanti ◽  
Angela Trapananti ◽  
Amol Karandikar ◽  
Innokenty Kantor ◽  
Carlo Marini ◽  
...  
Keyword(s):  
Melting Temperature ◽  
Absorption Spectroscopy ◽  
Inner Core ◽  
Solid Phase ◽  
Melting Curve ◽  
X Ray ◽  
Core Boundary ◽  
Diamond Anvil ◽  
Laser Heated ◽  
X Ray Absorption

Temperature, thermal history, and dynamics of Earth rely critically on the knowledge of the melting temperature of iron at the pressure conditions of the inner core boundary (ICB) where the geotherm crosses the melting curve. The literature on this subject is overwhelming, and no consensus has been reached, with a very large disagreement of the order of 2,000 K for the ICB temperature. Here we report new data on the melting temperature of iron in a laser-heated diamond anvil cell to 103 GPa obtained by X-ray absorption spectroscopy, a technique rarely used at such conditions. The modifications of the onset of the absorption spectra are used as a reliable melting criterion regardless of the solid phase from which the solid to liquid transition takes place. Our results show a melting temperature of iron in agreement with most previous studies up to 100 GPa, namely of 3,090 K at 103 GPa.

Study of the Liquid Crystalline Phases in Some Compounds of 4-Trans-(4-Alkyl)Cyclo-Hexylphenyl-Alkylcarboxylate

1983 ◽  
Vol 38 (12) ◽  
pp. 1362-1364 ◽  
Author(s):  
I. H. Ibrahim ◽  
W. Haase
Keyword(s):  
Differential Scanning Calorimetry ◽  
Nematic Phase ◽  
Liquid Crystalline ◽  
Intermolecular Distance ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Enthalpy Changes ◽  
Liquid Crystalline Phases ◽  
Nematic Phases

Abstract Three mesogenic compounds of the general formula have been investigated by differential scanning calorimetry. thermal optical microscopy and X-ray diffraction methods/Enthalpy changes of The different phase transitions for these compounds have been determined. H33 exhibits smectic B and nematic phases, whereas H34 and H75 exhibit only smectic B phases. The thickness of the smectic layers and the average intermolecular distance have been evaluated, as well as the corresponding molecular parameters in the nematic phase.

scholarly journals Adsorptive desulfurization of diesel using activated sewage sludge: kinetics, equilibrium and thermodynamics studies

2019 ◽  
Vol 10 (1) ◽  
pp. 1-12 ◽  
Author(s):  
David Stan Aribike ◽  
Mohammed Awwalu Usman ◽  
Mojirade M. Oloruntoba
Keyword(s):  
Sewage Sludge ◽  
Fossil Fuels ◽  
Freundlich Isotherm ◽  
Entropy Change ◽  
Oxidizing Agent ◽  
Optimum Conditions ◽  
Adsorptive Desulfurization ◽  
Equilibrium Study ◽  
Enthalpy Changes ◽  
Activated Sewage Sludge

AbstractCombustion of fossil fuels gives rise to sulfur oxides, which are harmful to the environment. Adsorptive desulfurization (ADS) of diesel was conducted using sewage sludge activated with H2O2 as the oxidizing agent. A full 22 central composite response surface design was employed to determine optimum conditions for the production of activated sewage sludge (ASS). The adsorbent (ASS) was characterized using SEM, EDX and FTIR and the results of the analysis showed that it has the capacity to desulfurize diesel significantly. The ASS was subsequently used to conduct batch ADS of diesel with a view to investigate the kinetics, equilibrium and thermodynamics of the process. The optimum conditions established for the production of ASS using H2O2 as the oxidizing agent were: temperature 400 °C and holding time 60 min. The Elovich model gave the best fit to the kinetic data of the ADS of diesel using ASS, while the equilibrium study showed that the Freundlich isotherm fitted the data at 35 °C better than Temkin and Langmuir isotherms. The positive values of the free energy and enthalpy changes revealed that the process was non-spontaneous and endothermic, respectively, while the negative entropy change is evidence of decrease in randomness of the adsorbed species. 33% desulfurization was achieved in 100 min during ADS of diesel showing that the adsorbent developed by activating SS with H2O2 was very good and effective. Thus, ASS can be used to gain more insight into kinetics, equilibrium and thermodynamics of the ADS of middle-distillate petroleum fractions.

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