Hydraulic conductivity of natural clays permeated with simple liquid hydrocarbons

1985 ◽  
Vol 22 (2) ◽  
pp. 205-214 ◽  
Author(s):  
Federico Fernandez ◽  
Robert M. Quigley
Keyword(s):  
Dielectric Constant ◽  
Hydraulic Conductivity ◽  
Pore Water ◽  
Void Ratio ◽  
Pore Space ◽  
Water Soluble ◽  
Low Dielectric Constant ◽  
Simple Liquid ◽  
Liquid Hydrocarbons ◽  
Low Dielectric

The hydraulic conductivity, k, of clayey soils is strongly influenced by the physicochemical properties of permeating liquid hydrocarbons. Tests on natural Sarnia soils mixed with pure liquids at a void ratio of 0.8 yielded k values that increased from 5 × 10−9 to 1 × 10−4 cm/s as the dielectric constant of the permeant decreased from 80 to 2.Sequential permeation of compacted, water-wet samples (k ≈ 10−8 cm/s) showed no changes in hydraulic conductivity when permeated with water-insoluble hydrocarbons of low dielectric constant (benzene, cyclohexane, xylene). These hydrophobic liquids were forced through microchannels or macropores and displaced less than 10% of the pore water from samples at a void ratio of unity.Permeation with water-soluble alcohols resulted in extensive removal of the pore water and up to 10-fold increases in k. Subsequent permeation with liquid aromatics of very low dielectric constant resulted in 1000-fold increases in k with only 30% of the pore space occupied by the aromatics. Association liquids such as alcohol that are mutually soluble in water and the aromatics seem to be required to initiate huge increases in k over testing periods of short duration. Key words: hydraulic conductivity, liquid hydrocarbons, clay barriers, dielectric constant.

Viscosity and dielectric constant controls on the hydraulic conductivity of clayey soils permeated with water-soluble organics

1988 ◽  
Vol 25 (3) ◽  
pp. 582-589 ◽  
Author(s):  
F. Fernandez ◽  
R. M. Quigley
Keyword(s):  
Dielectric Constant ◽  
Hydraulic Conductivity ◽  
Double Layer ◽  
Pore Space ◽  
Water Soluble ◽  
Organic Liquids ◽  
Clayey Soils ◽  
Compacted Clay ◽  
High Concentrations ◽  
Water Saturated

Water-soluble organic liquids may, under some circumstances, dramatically increase the hydraulic conductivity, k, of water-saturated clayey soils, thus destroying their effectiveness as barriers for contaminants. Double-layer contraction at constant void ratio with resultant increases in the pore space available for flow has been identified as a primary mechanism for such increases in k. This paper shows, however, that the increased viscosity of solutions of some organics in water results in significant decreases in k.Pure alcohols (ethanol and methanol) and other water solubles (dioxane) when permeated through water-compacted clay samples produce an initial decrease in k, followed by a gradual increase to equilibrium values. The "hydrocarbon" front raises the viscosity of the pore fluid and causes an initial drop in k. Tests using aqueous solutions of ethanol and dioxane show decreases in k at concentrations up to ~70%. Only at high concentrations does the dielectric constant, double-layer effect overcome the viscosity effect and produce net increases in k.Effective stresses σ′vof 160 kPa during permeation with ethanol and dioxane prevent the increases in k. Physicochemically induced consolidation and increased K0-shearing effects that close shrinkage cracks are operative. Key words: hydraulic conductivity, liquid hydrocarbons, clay, viscosity, dielectric constant.

Structire, Properties, and Process Characteristics of Low-K Materials Prepared by PECVD

1999 ◽  
Vol 565 ◽  
Author(s):  
Y. Shimogaki ◽  
S. W. Lim ◽  
E. G. Loh ◽  
Y. Nakano ◽  
K. Tada ◽  
...  
Keyword(s):  
Growth Rate ◽  
Dielectric Constant ◽  
Gas Flow ◽  
Structural Changes ◽  
Silicon Oxide ◽  
Reactive Species ◽  
Low Dielectric Constant ◽  
Low Dielectric ◽  
Step Coverage ◽  
Low K

AbstractLow dielectric constant F-doped silicon oxide films (SiO:F) can be prepared by adding fluorine source, like as CF4 to the conventional PECVD processes. We could obtain SiO:F films with dielectric constant as low as 2.6 from the reaction mixture of SiH4/N2 O/CF4. The structural changes of the oxides were sensitively detected by Raman spectroscopy. The three-fold ring and network structure of the silicon oxides were selectively decreased by adding fluorine into the film. These structural changes contribute to the decrease ionic polarization of the film, but it was not the major factor for the low dielectric constant. The addition of fluorine was very effective to eliminate the Si-OH in the film and the disappearance of the Si-OH was the key factor to obtain low dielectric constant. A kinetic analysis of the process was also performed to investigate the reaction mechanism. We focused on the effect of gas flow rate, i.e. the residence time of the precursors in the reactor, on growth rate and step coverage of SiO:F films. It revealed that there exists two species to form SiO:F films. One is the reactive species which contributes to increase the growth rate and the other one is the less reactive species which contributes to have uniform step coverage. The same approach was made on the PECVD process to produce low-k C:F films from C2F4, and we found ionic species is the main precursor to form C:F films.

Defect free monolayer and bilayer graphene exfoliated by solvent with low dielectric constant

2020 ◽  
Author(s):  
Vedanki ◽  
Chandrabhan Dohare ◽  
Pawan KumarSrivastava ◽  
Premlata Yadav ◽  
Subhasis Ghosh
Keyword(s):  
Dielectric Constant ◽  
Bilayer Graphene ◽  
Low Dielectric Constant ◽  
Low Dielectric
Sign in / Sign up

Export Citation Format

Share Document