High-Pressure Dependence of the Free Volume in Fluoroelastomers from Positron Lifetime andPVTExperiments

2005 ◽  
Vol 38 (2) ◽  
pp. 429-437 ◽  
Author(s):  
Günter Dlubek ◽  
Jan Wawryszczuk ◽  
Jürgen Pionteck ◽  
Tomasz Goworek ◽  
Harald Kaspar ◽  
...  
Keyword(s):  
High Pressure ◽  
Free Volume ◽  
Pressure Dependence ◽  
Positron Lifetime

Temperature and Pressure Dependence of the Free Volume in Polyisobutylene from Positron Lifetime and Pressure-Volume-Temperature Experiments

2006 ◽  
Vol 207 (8) ◽  
pp. 721-734 ◽  
Author(s):  
Duncan Kilburn ◽  
Jan Wawryszczuk ◽  
Günter Dlubek ◽  
Jürgen Pionteck ◽  
Rüdiger Häßler ◽  
...  
Keyword(s):  
Free Volume ◽  
Pressure Dependence ◽  
Positron Lifetime ◽  
Temperature And Pressure

scholarly journals Effect of an Improved Yasutomi Pressure-Viscosity Relationship on the Elastohydrodynamic Line Contact Problem

2013 ◽  
Vol 2013 ◽  
pp. 1-7
Author(s):  
Vincenzo Petrone ◽  
Adolfo Senatore ◽  
Vincenzo D'Agostino
Keyword(s):  
High Pressure ◽  
Film Thickness ◽  
Free Volume ◽  
Experimental Studies ◽  
Line Contact ◽  
Volume Model ◽  
Free Volume Model ◽  
Pressure Area ◽  
New Formulation ◽  
Lubricant Viscosity

This paper presents the application of an improved Yasutomi correlation for lubricant viscosity at high pressure in a Newtonian elastohydrodynamic line contact simulation. According to recent experimental studies using high pressure viscometers, the Yasutomi pressure-viscosity relationship derived from the free-volume model closely represents the real lubricant piezoviscous behavior for the high pressure typically encountered in elastohydrodynamic applications. However, the original Yasutomi correlation suffers from the appearance of a zero in the function describing the pressure dependence of the relative free volume thermal expansivity. In order to overcome this drawback, a new formulation of the Yasutomi relation was recently developed by Bair et al. This new function removes these concerns and provides improved precision without the need for an equation of state. Numerical simulations have been performed using the improved Yasutomi model to predict the lubricant pressure-viscosity, the pressure distribution, and the film thickness behavior in a Newtonian EHL simulation of a squalane-lubricated line contact. This work also shows that this model yields a higher viscosity at the low-pressure area, which results in a larger central film thickness compared with the previous piezoviscous relations.

Mechanical and microstructural properties of polystyrene based composites: positron lifetime spectroscopic and DSC studies

2011 ◽  
Vol 31 (2-3) ◽  
Author(s):  
Abdullah Mohammed Ali Mohammed Altaweel ◽  
Jaya Madhu Raj ◽  
Malalvalli Nagarajaiah Chandrashekara ◽  
Puttegowda Ramya ◽  
Parthasarathy Sampathkumaran ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Thermal Stability ◽  
Free Volume ◽  
Positron Lifetime ◽  
Tensile Modulus ◽  
Silica Content ◽  
Scanning Calorimetry ◽  
Dsc Studies ◽  
Microstructural Property ◽  
Calcium Aluminosilicate

Abstract Polystyrene (PS) based composites respectively with cenosphere (CS) and calcium aluminosilicate (CAS) as fillers were studied using the positron lifetime technique to reveal the correlation between free volume, a microstructural property, and mechanical properties of the composites (tensile strength and tensile modulus). The thermal stability of the composites was determined using differential scanning calorimetry. The results showed that addition of CAS filler lead to a significant improvement in the mechanical properties of the composite, whereas addition of CS resulted in improvement in tensile modulus only. Both PS/CAS and PS/CS composites showed enhancement in thermal stability compared with that of the pure PS matrix. The positron results showed that the average free volume size for the PS/CAS composite (at 40 phr CAS) was reduced significantly compared with that of the pure PS. These results are understood in terms of the influence of silica content, filler-matrix interaction, and particle size.

Measured temperature and pressure dependence of Vp and Vs in compacted, polycrystalline sI methane and sII methane–ethane hydrate

2003 ◽  
Vol 81 (1-2) ◽  
pp. 47-53 ◽  
Author(s):  
M B Helgerud ◽  
W F Waite ◽  
S H Kirby ◽  
A Nur
Keyword(s):  
High Pressure ◽  
Shear Wave ◽  
Pressure Dependence ◽  
Gas Hydrate ◽  
Pressure Vessel ◽  
Wave Speed ◽  
Measured Temperature ◽  
Shear Wave Speed ◽  
Temperature And Pressure ◽  
Fixed End

We report on compressional- and shear-wave-speed measurements made on compacted polycrystalline sI methane and sII methane–ethane hydrate. The gas hydrate samples are synthesized directly in the measurement apparatus by warming granulated ice to 17°C in the presence of a clathrate-forming gas at high pressure (methane for sI, 90.2% methane, 9.8% ethane for sII). Porosity is eliminated after hydrate synthesis by compacting the sample in the synthesis pressure vessel between a hydraulic ram and a fixed end-plug, both containing shear-wave transducers. Wave-speed measurements are made between –20 and 15°C and 0 to 105 MPa applied piston pressure. PACS No.: 61.60Lj

Preliminary Positron Lifetime Results on Free Volumes in Cyclodextrins

2010 ◽  
Vol 666 ◽  
pp. 99-102 ◽  
Author(s):  
Maria Fatima Ferreira Marques ◽  
A.M.G. Moreira Da Silva ◽  
P.M. Gordo ◽  
Z. Kajcsos
Keyword(s):  
Positron Annihilation ◽  
Free Volume ◽  
Positron Lifetime ◽  
Positron Annihilation Lifetime Spectroscopy ◽  
Positron Source ◽  
Lifetime Component ◽  
Positron Annihilation Lifetime ◽  
Long Lifetime

Positron annihilation lifetime spectroscopy was used to study the free-volume parameters in various pure -, - and -cyclodextrins samples and, in the case of β-cyclodextrin, with inclusion of S-carvone and thymoquinone. The results clearly indicate the presence of long lifetime components related to Ps-formation. The data show that the addition of S-carvone to β-cyclodextrin results in a decrease of o-Ps lifetime that we ascribe to a reduction of free volume holes from 81.8 to 63.7 Å3. The long lifetime component disappears when thymoquinone is added to -cyclodextrin, indicating this substance acts as an o-Ps quencher. For all samples studied, a decrease in the long lifetime component values was observed with increasing source in situ time, a result that might be attributed to the irradiation of the sample by the 22Na positron source.

Intermolecular Interactions of Xe Atoms Confined in One-dimensional Nanochannels of Tris(o-phenylenedioxy)cyclotriphosphazene as Studied by High-pressure 129Xe NMR

2003 ◽  
Vol 58 (12) ◽  
pp. 727-734 ◽  
Author(s):  
Hirokazu Kobayashi ◽  
Takahiro Ueda ◽  
Keisuke Miyakubo ◽  
Taro Eguchi
Keyword(s):  
High Pressure ◽  
Nmr Spectroscopy ◽  
Chemical Shift ◽  
Pressure Dependence ◽  
Average Distance ◽  
Chemical Shift Tensor ◽  
Axially Symmetric ◽  
One Dimensional ◽  
129Xe Nmr ◽  
The One

The pressure dependence of the 129Xe chemical shift tensor confined in the Tris(o-phenylenedioxy) cyclotriphosphazene (TPP) nanochannel was investigated by high-pressure 129Xe NMR spectroscopy. The observed 129Xe spectrum in the one-dimensional TPP nanochannel (0.45 nm in diameter) exhibits a powder pattern broadened by an axially symmetric chemical shift tensor. As the pressure increases from 0.02 to 7.0 MPa, a deshielding of 90 ppm is observed for the perpendicularcomponent of the chemical shift tensor δ⊥, whereas a deshielding of about 30 ppm is observed for the parallel one, δ‖. This suggests that the components of the chemical shift tensor, δ‖ and δ⊥, are mainly dominated by the Xe-wall and Xe-Xe interaction, respectively. Furthermore, the effect of helium, which is present along with xenon gas, on the 129Xe chemical shift is examined in detail. The average distance between the Xe atoms in the nanochannel is estimated to be 0.54 nm. This was found by using δ⊥ at the saturated pressure of xenon, and comparing the increment of the chemicalshift value in δ⊥ to that of a β -phenol/Xe compound.

Free Activation Energies and Activation Volumes for the Amide Rotation in Some Peptides Studied by High Pressure 1H-High Resolution NMR

1982 ◽  
Vol 37 (1-2) ◽  
pp. 51-56 ◽  
Author(s):  
H. Hauer ◽  
H.-D. Lüdemann ◽  
R. Jaenicke
Keyword(s):  
High Pressure ◽  
High Resolution ◽  
Pressure Dependence ◽  
Nmr Spectra ◽  
Conformational Transition ◽  
Activation Energies ◽  
High Resolution Nmr ◽  
Maximum Contribution ◽  
The Given ◽  
Amide Rotation

From the pressure dependence of 1H high resolution NMR spectra of two dipeptides (glycylsarcosine and N-acetyl-ʟ-proline-NH-methylamide in the range 0.1 MPa ≤p ≤ 150 MPa the activation volumes ⊿V≠ for the amide rotation are derived. This conformational transition is characterized for glycylsarcosine by ⊿V≠ = 4 ± 1 cm3 · mol-1 and for. the proline derivative by ⊿V≠ = 7.5±1 cm3 · mol-1. From the given results the maximum contribution of proline cis ⇌ trans isomerisation to the pressure dependence of the rate of reactivation of proteins can be estimated to ~ - 30% per MPa and proline present.

High-pressure dependence of Raman phonons of R MnO 3 ( R=Pr,Tb )

2003 ◽  
Vol 171 (1-2) ◽  
pp. 313-316 ◽  
Author(s):  
L. Martín-Carrón ◽  
J. Sánchez-Benítez ◽  
A. de Andrés
Keyword(s):  
High Pressure ◽  
Pressure Dependence
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