Relaxation Phenomena and Thermodynamics of Liquids at Very High Pressures

1996 ◽  
Vol 464 ◽  
Author(s):  
W. F. Oliver
Keyword(s):  
High Pressure ◽  
Glass Transition ◽  
Light Scattering ◽  
Liquid State ◽  
High Pressures ◽  
Equations Of State ◽  
Brillouin Scattering ◽  
Dynamic Properties ◽  
Relaxation Processes ◽  
Glass Forming

ABSTRACTComplex liquid glass-forming systems ranging from those composed of simple molecules to polymer melts and amorphous polymers have been studied extensively as a function of temperature resulting in a basic understanding of liquid-state dynamics and glass transition phenomenology as these systems are supercooled to the vitreous state. An important aspect of this problem that remains largely unexplored, and that is relevant to the topic of this symposium, involves liquid-state dynamics and vitrification (as well as crystallization) in the regime of high pressure and high density. We describe work on “fragile” to “intermediate strength” simple organic glass-forming liquids where both temperature (T) and pressure (P) are varied. Diamond anvil cells are used to achieve pressures exceeding 10 GPa. Several optical and light scattering techniques are used to explore both static and dynamic properties of these systems. High-pressure Brillouin scattering enables us to model the longitudinal relaxation time in these systems as well as their equations of state. These can now be refined by direct measurements of the pressure dependence of the glass transition, Tg(P). Finally, we summarize depolarized light scattering studies which allow us to compare both the isobaric and isothermal evolution of structural (α) and fast (β) relaxation processes.

Relaxation Processes Features of Glass-Forming Melts on the Basis of Copper

2015 ◽  
Vol 660 ◽  
pp. 108-112
Author(s):  
Viktor Konashkov ◽  
Vladimir Tsepelev ◽  
Arkadi Povodator
Keyword(s):  
Relaxation Process ◽  
Constant Temperature ◽  
Liquid State ◽  
Kinematic Viscosity ◽  
Relaxation Processes ◽  
Temperature Instability ◽  
State Data ◽  
Glass Forming ◽  
Heating And Cooling ◽  
Two Samples

Two samples of industrial alloys on the basis of copper are experimentally studied. These alloys are used for production of amorphous solders. The main studied property is kinematic viscosity of metal melt in a liquid state. Data of viscosity dependences from temperature when heating and the subsequent cooling are obtained. Besides, viscosity dependences at constant temperatures from time are received. On viscosity dependences from temperature, for the same samples, abnormal sites and a divergence of curves of heating and cooling are found. On viscosity dependences from time, at a constant temperature, instability is found. The conclusion is drawn that the revealed features are connected with complexity of relaxation process of the studied fusions.

Time and Ensemble Averaged Dynamic Light Scattering in Orthoterphenyl Above and Below the Glass Transition

1996 ◽  
Vol 455 ◽  
Author(s):  
D. L. Sidebottom ◽  
C. M. Sorensen
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Light Scattering ◽  
Dynamic Light Scattering ◽  
Structural Relaxation ◽  
Mode Coupling ◽  
Average Correlation ◽  
Glass Forming ◽  
Ergodicity Breaking

ABSTRACTWhile traditional dynamic light scattering is useful for following structural relaxation in the liquid, in the glassy domain the technique is limited by the ultimate patience of the experimentalist; i.e., the structural relaxation can not be measured when the experimental time scale is less than the structural relaxation time. Nevertheless, we show how useful information regarding structural relaxation can be accessed from light scattering in the glass using a novel ensemble-averaged technique. Dynamic light scattering (DLS) measurements performed on glass forming orthoterphenyl show an inequality between time and ensemble average correlation functions near and below the calorimetrie glass transition temperature, Tg, and hence demonstrate ergodicity breaking. Our ensemble averaged measurements provide a measure of the so-called non-ergodicity parameter, fq, below Tg. Our DLS results for orthoterphenyl indicate that the functional form for fq is consistent with Mode Coupling theory predictions, but occurs at the glass transition temperature, Tg≈243K, rather than at TC≈290K as observed in neutron scattering studies.

Measurement of Decompression Wave Speed in Rich Gas Mixtures at High Pressures (370 bars) Using a Specialized Rupture Tube

2010 ◽  
Vol 132 (5) ◽  
Author(s):  
K. K. Botros ◽  
J. Geerligs ◽  
R. J. Eiber
Keyword(s):  
High Pressure ◽  
Natural Gas ◽  
Wave Speed ◽  
High Pressures ◽  
Equations Of State ◽  
Gas Mixtures ◽  
Internal Diameter ◽  
Decompression Wave ◽  
Predicted Values ◽  
Fracture Arrest

Measurements of decompression wave speed in conventional and rich natural gas mixtures following rupture of a high-pressure pipe have been conducted. A high-pressure stainless steel rupture tube (internal diameter=38.1 mm and 42 m long) has been constructed and instrumented with 16 high frequency-response pressure transducers mounted very close to the rupture end and along the length of the tube to capture the pressure-time traces of the decompression wave. Tests were conducted for initial pressures of 33–37 MPa-a and a temperature range of 21–68°C. The experimentally determined decompression wave speeds were compared with both GASDECOM and PIPEDECOM predictions with and without nonequilibrium condensation delays at phase crossing. The interception points of the isentropes representing the decompression process with the corresponding phase envelope of each mixture were correlated with the respective plateaus observed in the decompression wave speed profiles. Additionally, speeds of sound in the undisturbed gas mixtures at the initial pressures and temperatures were compared with predictions by five equations of state, namely, BWRS, AGA-8, Peng–Robinson, Soave–Redlich–Kwong, and Groupe Européen de Recherches Gaziéres. The measured gas decompression curves were used to predict the fracture arrest toughness needed to assure fracture control in natural gas pipelines. The rupture tube test results have shown that the Charpy fracture arrest values predicted using GASEDCOM are within +7% (conservative) and −11% (nonconservative) of the rupture tube predicted values. Similarly, PIPEDECOM with no temperature delay provides fracture arrest values that are within +13% and −20% of the rupture tube predicted values, while PIPEDECOM with a 1°C temperature delay provides fracture arrest values that are within 0% and −20% of the rupture tube predicted values. Ideally, it would be better if the predicted values by the equations of state were above the rupture tube predicted values to make the predictions conservative but that was not always the case.

Seismic parameter φ: Computation at very high pressure from laboratory data

1966 ◽  
Vol 56 (3) ◽  
pp. 725-731
Author(s):  
Orson L. Anderson
Keyword(s):  
High Pressure ◽  
Bulk Modulus ◽  
Ultrasonic Velocity ◽  
Pressure Range ◽  
High Pressures ◽  
Equations Of State ◽  
Laboratory Data ◽  
Second Derivative ◽  
Velocity Measurements ◽  
Very High

abstract By using the accuracy inherent in ultrasonic velocity measurements taken at pressures less than 10 kb, the seismic parameter φ=vp2−(43)vS2 can be computed at very high pressures. The equation used requires the assumption that the second derivative with respect to pressure of the bulk modulus be negligible at all pressures considered. This assumption is checked by computing the compression (V/V0) in the pressure range by equations of state using the assumption, and comparing the resulting values with measured compression. Illustrations are given for MgO and Al2O3.

Polarization Scrambling by Optical Windows Used for Light Scattering Experiments at High Pressures

1975 ◽  
Vol 29 (5) ◽  
pp. 393-396 ◽  
Author(s):  
D. M. Cantor ◽  
J. Schroeder ◽  
J. Jonas
Keyword(s):  
High Pressure ◽  
Light Scattering ◽  
High Pressures ◽  
Float Glass ◽  
Aperture Size ◽  
Qualitative Explanation ◽  
High Pressure Cell ◽  
Pressure Cell

Polarization scrambling by high pressure cell windows as a function of pressure up to 2 kbar has been measured for two window materials and two sizes of plug apertures. Measured scrambling was about 1% for quartz, 0.5% for float glass, and decreased with decreasing aperture size. The amount of scrambling decreased significantly with time when the cell was left pressurized. A qualitative explanation of the results, based on changes in the P44 Pockets coefficient with pressure is given.

Dielectric and Optical Properties of Polymer Confined in Random Porous Matrices

2005 ◽  
Vol 899 ◽  
Author(s):  
Fouad Aliev
Keyword(s):  
Glass Transition ◽  
Light Scattering ◽  
Average Pore Size ◽  
Orientational Order ◽  
Pore Wall ◽  
Molecular Structures ◽  
Relaxation Processes ◽  
Average Pore ◽  
Porous Matrices ◽  
Dielectric And Optical Properties

AbstractWe report the results of the investigations of the influence of confinement on the glass transition and dynamics of the a-relaxation processes in poly(octylmethacrylate) (POMA) by dielectric spectroscopy. The polymer was synthesized directly in pores of the porous glass matrix with interconnected and randomly oriented pores with an average pore size of 100 nm by free radical polymerization of the monomer. We found that confinement is resulted in the reduction of the glass transition temperature Tg of the polymer. This change in Tg was mainly due to the existence of a developed pore wall-polymer interface and difference in the dynamic behavior of polymer in the surface layers compared to that in the bulk. Complementary light scattering experiments show that in 100 nm matrices containing the polymer an anomalous change in light scattering, which switches the composite from the opaque state to the transparent, in a narrow temperature range around T = 60 °C. These changes could be explained by assuming that at low temperatures (opaque state) the orientational order of the relatively long linear aliphatic side groups is induced by the inner pore surface. The assumption of the formation of the orientationally ordered regions at the pore wall in confined POMA is in agreement with the molecular structures of the polymer and the surface of silica.

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