Modeling and Simulation of Membrane Structure and Transport Properties

2010 ◽  
pp. 29-74 ◽  
Author(s):  
V.N. Burganos
Keyword(s):  
Modeling And Simulation ◽  
Transport Properties ◽  
Membrane Structure

Production and Characterization of Nanoporous Polymer Membranes Produced by an Electrospraying Process

2000 ◽  
Author(s):  
Phillip Gibson ◽  
Heidi Schreuder-Gibson
Keyword(s):  
Transport Properties ◽  
Membrane Structure ◽  
Protective Clothing ◽  
Theoretical Calculations ◽  
Electrospun Fiber ◽  
Air Flow ◽  
Filtration Efficiency ◽  
Thin Layers ◽  
Direct Result ◽  
Fiber Mats

Abstract Electrospinning is a process by which high voltages are used to produce an interconnected membrane-like web of small fibers (10 to 500 nanometers in diameter). This novel fiber spinning technique provides the capacity to lace together a variety of types of polymers, fibers, and particles to produce ultrathin layers which are useful for chemical protective clothing. Of particular interest are electrospun membranes composed of elastomeric fibers, which are under development for several protective clothing applications. The various factors influencing electrospun nonwoven fibrous membrane structure and transport properties are discussed. Performance measurements on experimental electrospun fiber mats compared favorably with transport properties of textiles and membranes currently used in protective clothing systems. It was found that electrospun layers presented minimal impedance to moisture vapor diffusion required for evaporative cooling. There may be special considerations in the application of elastomeric membranes for protective clothing. Effects of membrane distortion upon transport behavior of the structure might be significant. Preliminary measurements have found that changes in elastomeric membrane structure under different states of biaxial strain were reflected in measurements of air flow through the membrane. Changes in membrane structure were also evident in environmental scanning electron microscope images of the pore/fiber rearrangement as the membrane was stretched. Experimental measurements and theoretical calculations show electrospun fiber mats to be extremely efficient at trapping airborne particles. The high filtration efficiency is a direct result of the submicron-size fibers generated by the electrospinning process. Electrospun nanofiber coatings were applied directly to an open cell polyurethane foam. The air flow resistance and aerosol filtration properties correlated with the electrospun coating add-on weight. Particle penetration through the foam layer, which is normally very high, was eliminated by extremely thin layers of electrospun nanofibers sprayed on to the surface of the foam. Electrospun fiber coatings produce an exceptionally lightweight multifunctional membrane for protective clothing applications which exhibits high breathability, elasticity, and filtration efficiency.

Carbon Nanotubes: Good Candidate for VLSI Interconnects

2013 ◽  
Vol 378 ◽  
pp. 165-171
Author(s):  
Neeraj Jain ◽  
A.K. Aggarwal ◽  
P.K. Chaudhary
Keyword(s):  
Carbon Nanotubes ◽  
Modeling And Simulation ◽  
Transport Properties ◽  
Electronic Materials ◽  
Thermal Conductance ◽  
Tube Length ◽  
Vlsi Interconnects ◽  
New Class ◽  
Geometrical Features ◽  
Dependent Model

Carbon nanotubes are being seen as a promising new class of electronic materials owing to the change in their properties with chirality and geometry of the nanotube. They are being considered for future VLSI applications due to their superior conductance and inductance properties which are important parameters while considering any material for an interconnect or via applications.In this paper, we report the variation in electrical and thermal conductance as well as inductance of a CNT with its geometrical features using a diameter dependent model. Also the dependence of conductance and inductance of a CNT on the type of nanotubes, tube length and tube diameter has been studied. As we know that at nanometre scale, the electrical and thermal transport properties of the components become extremely important as regards the functioning of the device and it is difficult to accurately measure these properties, therefore predictions using modeling and simulation play an important role in providing a guideline for design and fabrication of CNT interconnects and understanding the working of various other CNT based devices.

High ionic liquid content polymeric gel membranes: Correlation of membrane structure with gas and vapour transport properties

2012 ◽  
Vol 415-416 ◽  
pp. 801-809 ◽  
Author(s):  
Karel Friess ◽  
Johannes Carolus Jansen ◽  
Fabio Bazzarelli ◽  
Pavel Izák ◽  
Veronika Jarmarová ◽  
...  
Keyword(s):  
Ionic Liquid ◽  
Transport Properties ◽  
Membrane Structure ◽  
Vapour Transport ◽  
Liquid Content ◽  
Polymeric Gel ◽  
Gel Membranes

Spectroscopic Diagnostics of Tokamaks

1988 ◽  
Vol 102 ◽  
pp. 165-174
Author(s):  
C. de Michelis
Keyword(s):  
Transport Properties ◽  
Power Losses ◽  
Spectroscopic Diagnostics ◽  
Important Concern

AbstractImpurities being an important concern in tokamaks, spectroscopy plays a key role in their understanding. Techniques for the evaluation of concentrations, power losses and transport properties are surveyed, and a few developments are outlined.

Bimolecular and Monomolecular Lipid Films: Selected Area Electron Diffraction

1969 ◽  
Vol 27 ◽  
pp. 338-339
Author(s):  
Robert M. Glaeser ◽  
David W. Deamer
Keyword(s):  
Electron Diffraction ◽  
Membrane Structure ◽  
Molecular Organization ◽  
Membrane Material ◽  
X Ray Diffraction ◽  
Membrane Systems ◽  
X Ray ◽  
Selected Area Electron Diffraction ◽  
Lipid Films ◽  
Ultimate Objective

In the investigation of the molecular organization of cell membranes it is often supposed that lipid molecules are arranged in a bimolecular film. X-ray diffraction data obtained in a direction perpendicular to the plane of suitably layered membrane systems have generally been interpreted in accord with such a model of the membrane structure. The present studies were begun in order to determine whether selected area electron diffraction would provide a tool of sufficient sensitivity to permit investigation of the degree of intermolecular order within lipid films. The ultimate objective would then be to apply the method to single fragments of cell membrane material in order to obtain data complementary to the transverse data obtainable by x-ray diffraction.

Cellulose Acetate Reverse Osmosis Membrane Structure

1972 ◽  
Vol 30 ◽  
pp. 528-529
Author(s):  
H. K. Plummer ◽  
E. Eichen ◽  
C. D. Melvin
Keyword(s):  
Cellulose Acetate ◽  
Reverse Osmosis ◽  
Membrane Structure ◽  
Freeze Drying ◽  
Dense Layer ◽  
Water Removal ◽  
Reverse Osmosis Membrane ◽  
Correct Interpretation ◽  
Electron Image ◽  
Scanning Electron

Much of the work reported in the literature on cellulose acetate reverse osmosis membranes has raised new and important questions with regard to the dense or “active” layer of these membranes. Several thickness values and structures have been attributed to the dense layer. To ensure the correct interpretation of the cellulose acetate structure thirteen different preparative techniques have been used in this investigation. These thirteen methods included various combinations of water substitution, freeze drying, freeze sectioning, fracturing, embedding, and microtomy techniques with both transmission and scanning electron microscope observations.It was observed that several factors can cause a distortion of the structure during sample preparation. The most obvious problem of water removal can cause swelling, shrinking, and folds. Improper removal of embedding materials, when used, can cause a loss of electron image contrast and, or structure which could hinder interpretation.

Structure and Orientation of As Precipitates in LT-MBE Grown GaAs

1991 ◽  
Vol 49 ◽  
pp. 900-901 ◽  
Author(s):  
Alain Claverie ◽  
Zuzanna Liliental-Weber
Keyword(s):  
Transport Properties ◽  
Layer Thickness ◽  
Growth Temperature ◽  
Low Temperatures ◽  
Lattice Parameter ◽  
Crystalline Quality ◽  
Insulating Properties ◽  
Lt Gaas

GaAs layers grown by MBE at low temperatures (in the 200°C range, LT-GaAs) have been reported to have very interesting electronic and transport properties. Previous studies have shown that, before annealing, the crystalline quality of the layers is related to the growth temperature. Lowering the temperature or increasing the layer thickness generally results in some columnar polycrystalline growth. For the best “temperature-thickness” combinations, the layers may be very As rich (up to 1.25%) resulting in an up to 0.15% increase of the lattice parameter, consistent with the excess As. Only after annealing are the technologically important semi-insulating properties of these layers observed. When annealed in As atmosphere at about 600°C a decrease of the lattice parameter to the substrate value is observed. TEM studies show formation of precipitates which are supposed to be As related since the average As concentration remains almost unchanged upon annealing.

Warm and freeze-fracture of cotton seed radicles

1987 ◽  
Vol 45 ◽  
pp. 984-985
Author(s):  
E. L. Vigil ◽  
E. F. Erbe
Keyword(s):  
Thin Film ◽  
Water Vapor ◽  
Fracture Surface ◽  
Membrane Structure ◽  
Room Temperature ◽  
Freeze Fracture ◽  
Longitudinal Axis ◽  
Fracture Plane ◽  
Cotton Seeds ◽  
Condensed Water

In cotton seeds the radicle has 12% moisture content which makes it possible to prepare freeze-fracture replicas without fixation or cryoprotection. For this study we have examined replicas of unfixed radicle tissue fractured at room temperature to obtain data on organelle and membrane structure.Excised radicles from seeds of cotton (Gossyplum hirsutum L. M-8) were fractured at room temperature along the longitudinal axis. The fracture was initiated by spliting the basal end of the excised radicle with a razor. This procedure produced a fracture through the tissue along an unknown fracture plane. The warm fractured radicle halves were placed on a thin film of 100% glycerol on a flat brass cap with fracture surface up. The cap was rapidly plunged into liquid nitrogen and transferred to a freeze- etch unit. The sample was etched for 3 min at -95°C to remove any condensed water vapor and then cooled to -150°C for platinum/carbon evaporation.

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