Mechanisms Underlying Foam-Based Electronucleation of Hydrates

2018 ◽  
Author(s):  
Palash V. Acharya ◽  
Denise Lin ◽  
Vaibhav Bahadur
Keyword(s):  
Induction Time ◽  
Metal Ion ◽  
Electrical Potential ◽  
Carbon Foam ◽  
Molar Ratio ◽  
Electrical Potential Difference ◽  
Carbon Foams ◽  
Voltage Dependent ◽  
Open Cell Foams ◽  
Induction Times

Nucleation of clathrate hydrates at low temperatures is constrained by very long induction (wait) times, which can range from hours to days. Electronucleation (application of an electrical potential difference across the hydrate forming solution) can significantly reduce the induction time. This work studies the use of porous open-cell foams of various materials as electronucleation electrodes. Experiments with tetrahydrofuran (THF) hydrates reveal that aluminum and carbon foam electrodes can enable voltage-dependent nucleation, with induction times dependent on the ionization tendency of the foam material. Furthermore, we observe a non-trivial dependence of the electronucleation parameters such as induction time and the recalescence temperature on the water:THF molar ratio. This study further corroborates previously developed hypotheses which associated rapid hydrate nucleation with the formation of metal-ion coordination compounds. Overall, this work studies various aspects of electronucleation with aluminum and carbon foams.

Mechanisms Underlying Rapid Electronucleation and Freezing of Hydrates

2017 ◽  
Author(s):  
Palash V. Acharya ◽  
Arjang Shahriari ◽  
Denise Lin ◽  
Vaibhav Bahadur
Keyword(s):  
Induction Time ◽  
Metal Ion ◽  
Electrical Potential ◽  
Hydrate Formation ◽  
Precursor Solution ◽  
Aluminum Foams ◽  
Bubble Generation ◽  
Porous Aluminum ◽  
Induction Times ◽  
Formation Of Hydrates

Nucleation of hydrates is constrained by very long induction (wait) times, which can range from hours to days. Electronucleation (application of an electrical potential across the precursor solution) can significantly reduce the induction time for nucleation. This study shows that porous aluminum foams (open-cell) enable near-instantaneous electronucleation at very low voltages. Experiments with tetrahydrofuran hydrates reveal that aluminum foam electrodes enable voltage-dependent nucleation with induction times of only tens of seconds at voltages as low as 20 V. Foam-based electrodes can reduce the induction time by up to 150X when compared to non-foam electrodes. Furthermore, this study reveals that electronucleation can be attributed to two distinct phenomena, namely bubble generation (due to electrolysis), and the formation of metal-ion coordination compounds. These mechanisms affect the induction time to different extents and depend on electrode material and polarity. Overall, this work uncovers the benefits of using foams for formation of hydrates, with foams aiding nucleation as well as propagation of the hydrate formation front.

scholarly journals Composite Carbon Foams as an Alternative to the Conventional Biomass-Derived Activated Carbon in Catalytic Application

Materials ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4540
Author(s):  
Mahitha Udayakumar ◽  
Renáta Zsanett Boros ◽  
László Farkas ◽  
Andrea Simon ◽  
Tamás Koós ◽  
...  
Keyword(s):  
Weight Loss ◽  
Activated Carbon ◽  
Metal Ion ◽  
Carbon Foam ◽  
Active Surface ◽  
Gas Production ◽  
Polyurethane Foams ◽  
Carbon Catalyst ◽  
Carbon Foams ◽  
Composite Carbon

The suitability of a new type of polyurethane-based composite carbon foam for several possible usages is evaluated and reported. A comparison of the properties of the as-prepared carbon foams was performed with widely available commercial biomass-derived activated carbon. Carbon foams were synthesized from polyurethane foams with different graphite contents through one-step activation using CO2. In this work, a carbon catalyst was synthesized with a moderately active surface (SBET = 554 m2/g), a thermal conductivity of 0.09 W/mK, and a minimum metal ion content of 0.2 wt%, which can be recommended for phosgene production. The composite carbon foams exhibited better thermal stability, as there is a very little weight loss at temperatures below 500 °C, and weight loss is slower at temperatures above 500 °C (phosgene synthesis: 550–700 °C). Owing to the good surface and thermal properties and the negligible metallic impurities, composite carbon foam produced from polyurethane foams are the best alternative to the conventional coconut-based activated carbon catalyst used in phosgene gas production.

OSMOTIC INHIBITION OF THE NATRIFERIC RESPONSE OF THE TOAD URINARY BLADDER TO VASOPRESSIN

1975 ◽  
Vol 67 (1) ◽  
pp. 119-125
Author(s):  
P. J. BENTLEY
Keyword(s):  
Urinary Bladder ◽  
Water Movement ◽  
Short Circuit ◽  
Electrical Potential ◽  
Short Circuit Current ◽  
Toad Bladder ◽  
Toad Urinary Bladder ◽  
Electrical Potential Difference ◽  
Osmotic Gradient

SUMMARY The electrical potential difference and short-circuit current (scc, reflecting active transmural sodium transport) across the toad urinary bladder in vitro was unaffected by the presence of hypo-osmotic solutions bathing the mucosal (urinary) surface, providing that the transmural flow of water was small. Vasopressin increased the scc across the toad bladder (the natriferic response), but this stimulation was considerably reduced in the presence of a hypo-osmotic solution on the mucosal side, conditions under which water transfer across the membrane was also increased. This inhibition of the natriferic response did not depend on the direction of the water movement, for if the osmotic gradient was the opposite way to that which normally occurs, the response to vasopressin was still reduced. The natriferic response to cyclic AMP was also inhibited in the presence of an osmotic gradient. Aldosterone increased the scc and Na+ transport across the toad bladder but this response was not changed when an osmotic gradient was present. The physiological implications of these observations and the possible mechanisms involved are discussed.

Reversal of glibenclamide and voltage block of an epithelial KATP channel

1996 ◽  
Vol 271 (4) ◽  
pp. C1122-C1130 ◽  
Author(s):  
O. Mayorga-Wark ◽  
W. P. Dubinsky ◽  
S. G. Schultz
Keyword(s):  
Hydrophobic Interactions ◽  
Basolateral Membrane ◽  
Electrical Potential ◽  
Membrane Vesicles ◽  
Voltage Gating ◽  
Electrical Potential Difference ◽  
Outer Solution ◽  
Channel Inhibition ◽  
K Concentration ◽  
Voltage Gate

K+ channels present in basolateral membrane vesicles isolated from Necturus maculosa small intestinal cells and reconstituted into planar phospholipid bilayers are inhibited by MgATP and sulfonylurea derivatives, such as tolbutamide and glibenclamide, when these agents are added to the solution bathing the inner mouth of the channel. In addition, these channels possess an intrinsic "voltage gate" and are blocked when the electrical potential difference across the channel is oriented so that the inner solution is electrically positive with respect to the outer solution. We now show that increasing the concentration of permeant ions such as K+ or Rb+ in the outer solution reverses channel inhibition resulting from the addition of 50 microM glibenclamide to the inner solution and also inhibits intrinsic voltage gating; these effects are not elicited by increasing the concentrations of the relatively impermeant ions, Na+ or choline, in the outer solution. Furthermore, increasing the K+ concentration in the outer solution in the absence of glibenclamide inhibits voltage gating, and, under these conditions, the subsequent addition of glibenclamide to the inner solution is ineffective. These results are consistent with a model in which the voltage gate is an open-channel blocker whose action is directly reversed by elevating the external concentration of relatively permeant cations and where the action of glibenclamide is to stabilize the inactivated state of the channel, possibly through hydrophobic interactions.

Membranes and Membrane Processes

MRS Bulletin ◽  
1999 ◽  
Vol 24 (3) ◽  
pp. 19-22 ◽  
Author(s):  
Vasilis N. Burganos
Keyword(s):  
Membrane Separation ◽  
Transport Coefficients ◽  
Electrical Potential ◽  
Artificial Organs ◽  
Energy Storage And Conversion ◽  
Electrical Potential Difference ◽  
Catalytic Reactors ◽  
Membrane Processes ◽  
Separation Science ◽  
Structural And Functional Properties

Membrane separation science has enjoyed tremendous progress since the first synthesis of membranes almost 40 years ago, which was driven by strong technological needs and commercial expectations. As a result, the range of successful applications of membranes and membrane processes is continuously broadening. An additional change lies in the nature of membranes, which is now extended to include liquid and gaseous materials, biological or synthetic. Membranes are understood to be thin barriers between two phases through which transport can take place under the action of a driving force, typically a pressure difference and generally a chemical or electrical potential difference.An attempt at functional classification of membranes would have to include diverse categories such as gas separation, pervaporation, reverse osmosis, micro- and ultrafiltration, and biomedical separations. The dominant application of membranes is certainly the separation of mixed phases or fluids, homogeneous or heterogeneous. Separation of a mixture can be achieved if the difference in the transport coefficients of the components of interest is sufficiently large. Membranes can also be used in applications other than separation targeting: They can be employed in catalytic reactors, energy storage and conversion systems, as key components of artificial organs, as supports for electrodes, or even to control the rate of release of both useful and dangerous species.In order to meet the requirements posed by the aforementioned applications, membranes must combine several structural and functional properties.

High Specific Strength Carbon Foam Prepared from Sucrose and Multi-Walled Carbon Nanotube

2015 ◽  
Vol 830-831 ◽  
pp. 545-548
Author(s):  
Rajaram Narasimman ◽  
Sujith Vijayan ◽  
Kuttan Prabhakaran
Keyword(s):  
Compressive Strength ◽  
Carbon Nanotube ◽  
Cellular Structure ◽  
Carbon Foam ◽  
Specific Strength ◽  
High Specific Strength ◽  
Multi Walled Carbon Nanotube ◽  
Uniform Dispersion ◽  
Carbon Foams ◽  
Maximum Compressive Strength

Multi-walled carbon nanotube (MWNT) reinforced carbon foams were prepared by thermo-foaming of MWNT dispersions in molten sucrose followed by dehydration and carbonization. The rheological studies showed that the uniform dispersion of MWNT was achieved up to 1.5 wt.%. The carbon foams showed cellular structure. The density of the carbon foams increased with an increase in the MWNT concentration up to 0.25 wt.% and then remained more or less constant. The maximum compressive strength of 4.9 MPa was achieved at the MWNT concentration of 0.5 wt.%.

Active electrolyte transport in mammalian buccal mucosa

1988 ◽  
Vol 255 (3) ◽  
pp. G286-G291 ◽  
Author(s):  
R. C. Orlando ◽  
N. A. Tobey ◽  
V. J. Schreiner ◽  
R. D. Readling
Keyword(s):  
Buccal Mucosa ◽  
Short Circuit ◽  
Basolateral Membrane ◽  
Electrical Potential ◽  
Short Circuit Current ◽  
Electrolyte Transport ◽  
Electrical Potential Difference ◽  
Ussing Chambers ◽  
Net Fluxes

The transmural electrical potential difference (PD) was measured in vivo across the buccal mucosa of humans and experimental animals. Mean PD was -31 +/- 2 mV in humans, -34 +/- 2 mV in dogs, -39 +/- 2 mV in rabbits, and -18 +/- 1 mV in hamsters. The mechanisms responsible for this PD were explored in Ussing chambers using dog buccal mucosa. After equilibration, mean PD was -16 +/- 2 mV, short-circuit current (Isc) was 15 +/- 1 microA/cm2, and resistance was 1,090 +/- 100 omega.cm2, the latter indicating an electrically "tight" tissue. Fluxes of [14C]mannitol, a marker of paracellular permeability, varied directly with tissue conductance. The net fluxes of 22Na and 36Cl were +0.21 +/- 0.05 and -0.04 +/- 0.02 mueq/h.cm2, respectively, but only the Na+ flux differed significantly from zero. Isc was reduced by luminal amiloride, serosal ouabain, or by reducing luminal Na+ below 20 mM. This indicated that the Isc was determined primarily by active Na+ absorption and that Na+ traverses the apical membrane at least partly through amiloride-sensitive channels and exits across the basolateral membrane through Na+-K+-ATPase activity. We conclude that buccal mucosa is capable of active electrolyte transport and that this capacity contributes to generation of the buccal PD in vivo.

Effect of Structure Modification on the Microwave Absorbing Performance of Carbon Foams

2011 ◽  
Vol 197-198 ◽  
pp. 536-539 ◽  
Author(s):  
Zhi Gang Fang ◽  
Yu Xin Gao ◽  
Chun Fang
Keyword(s):  
Electric Conductivity ◽  
Carbon Foam ◽  
Structure Design ◽  
Structure Modification ◽  
Replication Process ◽  
Microwave Absorbing Properties ◽  
Carbon Foams ◽  
Microwave Absorbing Property ◽  
Microwave Absorbing ◽  
Absorbing Property

Carbon foams were prepared by a polymer sponge replication process and their microwave absorbing properties were investigated. The electric conductivity of carbon foam has a direct effect on its microwave absorbing property, as the carbon foam with a medium electric conductivity of 0.46S/m has got a relatively excellent microwave absorbing property and demonstrated a characteristic of broadband absorption. Some structure modification has been made on carbon foams to fruther imrove their microwave absorbing performance. The result shows that making slots, especially gradient slots on the surface of carbon foams can greatly improve their microwave absorbing properties, while the reflection coefficients for a three-layered carbon foam structure exceeds -10dB with the combination effect of multilayer structure design and parameters gradient variatioin in the whole frequency range of 2.6-18GHz, which is usually to be considered as the practical application standard for microwave absorbing materials.

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