scholarly journals A unifying basis for the interplay of stress and chemical processes in the Earth: support from diverse experiments

2020 ◽  
Vol 175 (12) ◽  
Author(s):  
John Wheeler
Keyword(s):  
Chemical Potential ◽  
Chemical Processes ◽  
Phase Changes ◽  
Solid State Reactions ◽  
Fundamental Aspect ◽  
Diffusion Creep ◽  
Pressure Solution ◽  
Polymorphic Transformations ◽  
The Earth ◽  
And Diffusion

AbstractThe interplay between stress and chemical processes is a fundamental aspect of how rocks evolve, relevant for understanding fracturing due to metamorphic volume change, deformation by pressure solution and diffusion creep, and the effects of stress on mineral reactions in crust and mantle. There is no agreed microscale theory for how stress and chemistry interact, so here I review support from eight different types of the experiment for a relationship between stress and chemistry which is specific to individual interfaces: (chemical potential) = (Helmholtz free energy) + (normal stress at interface) × (molar volume). The experiments encompass temperatures from -100 to 1300 degrees C and pressures from 1 bar to 1.8 GPa. The equation applies to boundaries with fluid and to incoherent solid–solid boundaries. It is broadly in accord with experiments that describe the behaviours of free and stressed crystal faces next to solutions, that document flow laws for pressure solution and diffusion creep, that address polymorphic transformations under stress, and that investigate volume changes in solid-state reactions. The accord is not in all cases quantitative, but the equation is still used to assist the explanation. An implication is that the chemical potential varies depending on the interface, so there is no unique driving force for reaction in stressed systems. Instead, the overall evolution will be determined by combinations of reaction pathways and kinetic factors. The equation described here should be a foundation for grain-scale models, which are a prerequisite for predicting larger scale Earth behaviour when stress and chemical processes interact. It is relevant for all depths in the Earth from the uppermost crust (pressure solution in basin compaction, creep on faults), reactive fluid flow systems (serpentinisation), the deeper crust (orogenic metamorphism), the upper mantle (diffusion creep), the transition zone (phase changes in stressed subducting slabs) to the lower mantle and core mantle boundary (diffusion creep).

scholarly journals Dislocation and diffusion creep of synthetic anorthite aggregates

2000 ◽  
Vol 105 (B11) ◽  
pp. 26017-26036 ◽  
Author(s):  
E. Rybacki ◽  
G. Dresen
Keyword(s):  
Diffusion Creep ◽  
And Diffusion

scholarly journals Ductile saline ice

1994 ◽  
Vol 40 (136) ◽  
pp. 566-568
Author(s):  
G. A. Kuehn ◽  
E. M. Schulson
Keyword(s):  
Fresh Water ◽  
Tensile Ductility ◽  
Compressive Deformation ◽  
Dislocation Creep ◽  
Diffusion Creep ◽  
Water Ice ◽  
The Matrix ◽  
And Diffusion

AbstractExperiments have shown that tensile ductility of about 5% or more can be imparted to columnar, saline ice by pre-compressing the material by about 3.5%. This effect is similar to that observed in granular, fresh-water ice and is attributed to the operation of both dislocation creep and diffusion creep within that part of the matrix which recrystallized during the pre-compressive deformation.

Enhanced Oil-recovery and Its Environmental and Economic Implications in the United States

1981 ◽  
Vol 8 (1) ◽  
pp. 5-18 ◽  
Author(s):  
Douglas Argyle Campbell
Keyword(s):  
United States ◽  
Enhanced Oil Recovery ◽  
Oil Recovery ◽  
Oil Production ◽  
The United States ◽  
Chemical Processes ◽  
Environmental Research ◽  
Thermal Processes ◽  
Microbiological Processes ◽  
The Earth

This survey has described the foreseeable environmental and economic impacts of enhanced oil-recovery (EOR) on U.S. oil production between 1980 and 2000. It has indicated that EOR production may be expected to rise from the approximately 4% of total U.S. oil production in 1980, to the projected approximations of 10.5% in 1985, 18.5% in 1990, 23% in 1995, and perhaps 30% in 2000. These percentages are substantial, particularly as this form of oil production has been, up until recently, quite limited. Many of the processes are still in the laboratory stage of development—particularly chemical and microbiological processes. With continued laboratory experimentation and field research, it is possible that the percentages could be even greater than the above suggestions as we reach into the 21st Century.The potential for EOR is very considerable and probably great, as it could involve some two-thirds of all the oil already identified in the United States and assumed to be unrecoverable by primary or secondary means. The U.S. Department of Energy (DOE) has given important incentives to the EOR industry to make such increased production worth while through raising prices to compensate for the cost of equipment, and deducting expenditure on such equipment from a new ‘Windfall Profit Tax’.Along with EOR's economic potential, there are two major ecological dangers: air pollution through thermal processes, and ground-water pollution through chemical processes. It is essential to the well-being of the United States that clean air standards be adhered to, and that the equipment necessary to purify the air (particularly in California) be available and operate to reduce emissions.A great deal more research needs to be undertaken towards developing safeguards to ensure that drinkingwater is not contaminated by dangerous chemicals which may be used in ‘chemical flooding’ of depleted oil-wells. Many of these chemicals have merely ‘come out of the laboratory’ and are sold by chemical companies without sufficient field-testing. How far these chemicals could travel underground must still be determined. It is also important to ensure that carbon dioxide, fed into a geological formation, can be recaptured and re-injected without escaping into the atmosphere, where there is the potential danger of a global ‘greenhouse effect’ upon the world's temperature. Finally, it is important to safeguard the Earth against microbes which could be injected into its geological strata without sufficient knowledge of their impact on the ecology of the Earth. Thus, much environmental research will be called for with these new methods of producing oil for Man's use.This study has reviewed the four major methods of EOR that are currently being utilized or proposed— thermal processes, miscible and semi-miscible processes, chemical processes, and microbiological processes, and found that they could all have ongoing possibilities.Given appropriate environmental safeguards, EOR should become a major force in the production of energy for the United States over the next 20 years, and it seems reasonable to expect that much the same could apply to other parts of the world. However, it is important that safeguarding the environment should guide the DOE in terms of its incentive programmes for specific processes.

Strain localisation during diffusion creep: influence of grain coarsening and grain boundary sliding

2020 ◽  
Author(s):  
John Wheeler ◽  
Lynn Evans ◽  
Robyn Gardner ◽  
Sandra Piazolo
Keyword(s):  
Grain Size ◽  
Grain Boundary ◽  
Earth Pressure ◽  
Grain Boundary Sliding ◽  
Mechanical Anisotropy ◽  
Limited Attention ◽  
Diffusion Creep ◽  
Pressure Solution ◽  
Grain Coarsening ◽  
Boundary Sliding

<p>Diffusion creep and the wet low temperature version, pressure solution, are major deformation mechanisms in the Earth. Pressure solution operates in many metamorphosing systems in the crust and may contribute to slow creep on fault surfaces. Diffusion creep prevails in areas of the upper mantle deforming slowly, and possibly in most of the lower mantle. Both mechanisms contribute to localisation since small grain sizes can deform faster.</p><p>However, there has been limited attention paid to the evolution of microstructure during diffusion creep. In some experiments grains coarsen; in some but not all experiments grains remain rather equant. We have developed a grain-scale numerical model for diffusion creep, which indicates that those processes are very important in influencing evolving strength. Our models illustrate three behaviours.</p><ol><li>Strain localises along slip surfaces formed by aligned grain boundaries on all scales. This affects overall strength.</li> <li>Diffusion creep is predicted to produce elongate grains and then the overall aggregate has intense mechanical anisotropy. Thus strength during diffusion creep, and localisation on weak zones, is influenced not just by grain size but by other aspects of microstructure.</li> <li>Grain coarsening increases grain size and strength. Our most recent work shows how it interacts with ongoing deformation. In particular grain growth can lead to particular grain shapes which are directly related to strain rate, and influence strength. Consequently, understanding localisation during diffusion creep must encompass the effects of diffusion itself, grain boundary sliding and grain coarsening.</li> </ol>

scholarly journals Influence mechanism of excipients on drug crystallization: experimental investigation and model analysis and prediction

2022 ◽  
Author(s):  
Qiao Chen ◽  
Jingyun Weng ◽  
Gabriele Sadowski ◽  
Yuanhui Ji
Keyword(s):  
Crystal Growth ◽  
Growth Kinetics ◽  
Surface Reaction ◽  
Chemical Potential ◽  
Potential Gradient ◽  
Reaction Model ◽  
Reaction Rate Constant ◽  
Crystal Growth Kinetics ◽  
Kinetics Of ◽  
And Diffusion

The influence of temperature, stirring speed, and excipients on crystal growth kinetics of mesalazine and allopurinol was investigated through experiment and chemical potential gradient model. The results indicated that the Diffusion-Surface Reaction model (DSR (1,2)) showed good performance in modeling API crystal growth kinetics within the ARDs of 4%. Excipients played a crucial role in inhibiting crystal growth in all the systems. It can not only improve the API solubility, but also reduce the crystal growth rate. By comparing diffusion rate and surface-reaction rate constant within the DSR (1,2) model, it was found that the controlling step of mesalazine crystallization was surface-reaction. Allopurinol crystallization was dominated by both surface-reaction and diffusion. Meanwhile, the crystal growth kinetics of mesalazine and allopurinol were predicted successfully with the ARDs of 2.53% and 4.78%. This work provided a mechanistic understanding of polymer influence on the inhibition of API crystal growth.

Evaluation of Creep Properties in Soldering Ball by Nanoindentation Creep

2005 ◽  
Author(s):  
Tadahiro Shibutani ◽  
Qiang Yu ◽  
Masaki Shiratori
Keyword(s):  
Chemical Potential ◽  
Early Stage ◽  
Hydrostatic Stress ◽  
Equivalent Stress ◽  
Nanoindentation Test ◽  
Diffusion Creep ◽  
Creep Properties ◽  
Last Stage ◽  
Power Law Creep ◽  
The Relationship

In this paper, the behavior the behavior of creep deformation in low melting point alloy during a nanoindentation test was examined. Nanoindentation creep test was performed for eutectic tin-lead solder ball. Estimated creep exponent from the relationship between hardness and indenter dwell-time decreases as a function of time. The morphology of indented area shows that the transition from the deformation due to the tip in the early stage to another one in the last stage. Each grain near the indenter tip was transformed in the last stage. Stress analysis using a finite element method reveals that relaxation of equivalent stress progresses rapidly and the residual hydrostatic stress is dominant. Then, the gradient of the residual hydrostatic stress affects the chemical potential on grain boundaries and diffusion creep is activated. Therefore, the transition from the power-law creep to diffusion creep takes place during the nanoindentaion creep.

Atomic Understanding of the Swelling and Phase Transition of Polyacrylamide Hydrogel

2016 ◽  
Vol 08 (07) ◽  
pp. 1640002 ◽  
Author(s):  
Shuai Xu ◽  
Ying Wang ◽  
Jianying Hu ◽  
Zishun Liu
Keyword(s):  
Phase Transition ◽  
Continuum Mechanics ◽  
Chemical Potential ◽  
Polymer Network ◽  
Point Of View ◽  
Dynamics Simulation ◽  
Mechanics Model ◽  
Basic Parameters ◽  
Solvent Molecules ◽  
And Diffusion

A polymer network can imbibe copious amounts of solvent (water) and swell, and the resulting state is known as a hydrogel. In this study, we have made the modification for the all-atom consistent valence force field (CVFF) to investigate the swelling property of polyacrylamide (PAM) hydrogel by molecular dynamics simulation. We have built 21 hydrogel models with different solvent contents and calculate the average chemical potential and diffusion coefficient of solvent molecules in PAM hydrogel. We find that when the mass fraction of solvent is about 90%, PAM hydrogel reaches its free swelling limitation and loses the motivation of absorbing solvent. Furthermore, it is also found that PAM hydrogel has a phase transition phenomenon when the values of solvent chemical potential are between [Formula: see text][Formula: see text]kcal/mol and [Formula: see text][Formula: see text]kcal/mol. This study will provide insight into the basic parameters which are widely used in continuum mechanics analysis of hydrogels from atomic point of view and help researchers to improve the continuum mechanics model for neutral hydrogel.

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