Barrier Properties of Small Gas Molecules in Amorphous cis- 1,4-Polybutadiene Estimated by Simulation

2016 ◽  
pp. 146-159
Keyword(s):  
Barrier Properties ◽  
Gas Molecules

scholarly journals Diamine vapor treatment of viscoelastic graphene oxide liquid crystal for gas barrier coating

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Seung Eun Choi ◽  
Sung-Soo Kim ◽  
Eunji Choi ◽  
Ji Hoon Kim ◽  
Yunkyu Choi ◽  
...  
Keyword(s):  
Graphene Oxide ◽  
Liquid Crystal ◽  
Diffusion Length ◽  
Barrier Properties ◽  
Gas Barrier ◽  
Barrier Coating ◽  
Coating Method ◽  
Gas Molecules ◽  
Pet Film ◽  
Vapor Treatment

AbstractA layered graphene oxide/ethylenediamine (GO/EDA) composite film was developed by exposing aqueous GO liquid crystal (GOLC) coating to EDA vapor and its effects on the gas barrier performance of GO film were systematically investigated. When a GO/EDA coating with a thickness of approximately 1 μm was applied to a neat polyethylene terephthalate (PET) film, the resultant film was highly impermeable to gas molecules, particularly reducing the gas permeance up to 99.6% for He and 98.5% for H2 in comparison to the neat PET film. The gas barrier properties can be attributed to the long diffusion length through stacked GO nanosheets. The EDA can crosslink oxygen-containing groups of GO, enhancing the mechanical properties of the GO/EDA coating with hardness and elastic modulus values up to 1.14 and 28.7 GPa, respectively. By the synergistic effect of the viscoelastic properties of GOLC and the volatility of EDA, this coating method can be applied to complex geometries and EDA intercalation can be spontaneously achieved through the scaffold of the GOLC.

Organization of tight junctions in the choroid plexus epithelium

1978 ◽  
Vol 36 (2) ◽  
pp. 336-337
Author(s):  
B. Van Deurs ◽  
J. K. Koehler
Keyword(s):  
Choroid Plexus ◽  
Present Report ◽  
Freeze Fracture ◽  
Barrier Properties ◽  
Cell Junctions ◽  
Structural Basis ◽  
Apical Surface ◽  
Choroid Plexus Epithelium ◽  
Solid Nitrogen ◽  
Special Composition

The choroid plexus epithelium constitutes a blood-cerebrospinal fluid (CSF) barrier, and is involved in regulation of the special composition of the CSF. The epithelium is provided with an ouabain-sensitive Na/K-pump located at the apical surface, actively pumping ions into the CSF. The choroid plexus epithelium has been described as “leaky” with a low transepithelial resistance, and a passive transepithelial flux following a paracellular route (intercellular spaces and cell junctions) also takes place. The present report describes the structural basis for these “barrier” properties of the choroid plexus epithelium as revealed by freeze fracture.Choroid plexus from the lateral, third and fourth ventricles of rats were used. The tissue was fixed in glutaraldehyde and stored in 30% glycerol. Freezing was performed either in liquid nitrogen-cooled Freon 22, or directly in a mixture of liquid and solid nitrogen prepared in a special vacuum chamber. The latter method was always used, and considered necessary, when preparations of complementary (double) replicas were made.

Growth of near noble metal Pd and Pt thin film silicides morphology and structure

1984 ◽  
Vol 42 ◽  
pp. 498-499
Author(s):  
E. I. Alessandrini ◽  
M. O. Aboelfotoh
Keyword(s):  
Noble Metals ◽  
Annealing Temperature ◽  
Chemical Compounds ◽  
Barrier Properties ◽  
Solid State Reactions ◽  
Transmission Electron ◽  
Stable Chemical ◽  
Metal Thickness ◽  
Amorphous Si ◽  
Si Films

Considerable interest has been generated in solid state reactions between thin films of near noble metals and silicon. These metals deposited on Si form numerous stable chemical compounds at low temperatures and have found applications as Schottky barrier contacts to silicon in VLSI devices. Since the very first phase that nucleates in contact with Si determines the barrier properties, the purpose of our study was to investigate the silicide formation of the near noble metals, Pd and Pt, at very thin thickness of the metal films on amorphous silicon.Films of Pd and Pt in the thickness range of 0.5nm to 20nm were made by room temperature evaporation on 40nm thick amorphous Si films, which were first deposited on 30nm thick amorphous Si3N4 membranes in a window configuration. The deposition rate was 0.1 to 0.5nm/sec and the pressure during deposition was 3 x 10 -7 Torr. The samples were annealed at temperatures in the range from 200° to 650°C in a furnace with helium purified by hot (950°C) Ti particles. Transmission electron microscopy and diffraction techniques were used to evaluate changes in structure and morphology of the phases formed as a function of metal thickness and annealing temperature.

The effects of surface absorbed monolayer microdiffraction patterns

1988 ◽  
Vol 46 ◽  
pp. 680-681
Author(s):  
M. Pan ◽  
J.M. Cowley
Keyword(s):  
Surface Potential ◽  
Electron Probe ◽  
Potential Distribution ◽  
Crystal Surface ◽  
Normal Direction ◽  
Surface Image ◽  
Extended Surface ◽  
Gas Molecules ◽  
Surface Nature ◽  
Electron Microdiffraction

Electron microdiffraction patterns, obtained when a small electron probe with diameter of 10-15 Å is directed to run parallel to and outside a flat crystal surface, are sensitive to the surface nature of the crystals. Dynamical diffraction calculations have shown that most of the experimental observations for a flat (100) face of a MgO crystal, such as the streaking of the central spot in the surface normal direction and (100)-type forbidden reflections etc., could be explained satisfactorily by assuming a modified image potential field outside the crystal surface. However the origin of this extended surface potential remains uncertain. A theoretical analysis by Howie et al suggests that the surface image potential should have a form different from above-mentioned image potential and also be smaller by several orders of magnitude. Nevertheless the surface potential distribution may in practice be modified in various ways, such as by the adsorption of a monolayer of gas molecules.

Changes in corneocyte element concentrations occur in skin inner stratum corneum

1990 ◽  
Vol 48 (2) ◽  
pp. 146-147
Author(s):  
R. R. Warner
Keyword(s):  
Stratum Corneum ◽  
Human Skin ◽  
Element Concentration ◽  
Skin Barrier ◽  
Barrier Properties ◽  
Brick Wall ◽  
Inorganic Elements ◽  
Dry Skin ◽  
Skin Biopsies ◽  
Intercellular Lipid

Keratinocytes undergo maturation during their transit through the viable layers of skin, and then abruptly transform into flattened, anuclear corneocytes that constitute the cellular component of the skin barrier, the stratum corneum (SC). The SC is generally considered to be homogeneous in its structure and barrier properties, and is often shown schematically as a featureless brick wall, the “bricks” being the corneocytes, the “mortar” being intercellular lipid. Previously we showed the outer SC was not homogeneous in its composition, but contained steep gradients of the physiological inorganic elements Na, K and Cl, likely originating from sweat salts. Here we show the innermost corneocytes in human skin are also heterogeneous in composition, undergoing systematic changes in intracellular element concentration during transit into the interior of the SC.Human skin biopsies were taken from the lower leg of individuals with both “good” and “dry” skin and plunge-frozen in a stirred, cooled isopentane/propane mixture.

Principles of Low-Vacuum SEM

1992 ◽  
Vol 50 (2) ◽  
pp. 1304-1305
Author(s):  
Klaus-Ruediger Peters
Keyword(s):  
New Technologies ◽  
High Vacuum ◽  
Optical Microscope ◽  
Specimen Surface ◽  
Electrical Field ◽  
Gaseous Environment ◽  
New Information ◽  
Gas Molecules ◽  
New Interactions ◽  
Gas Pressures

Only recently it became possible to expand scanning electron microscopy to low vacuum and atmospheric pressure through the introduction of several new technologies. In principle, only the specimen is provided with a controlled gaseous environment while the optical microscope column is kept at high vacuum. In the specimen chamber, the gas can generate new interactions with i) the probe electrons, ii) the specimen surface, and iii) the specimen-specific signal electrons. The results of these interactions yield new information about specimen surfaces not accessible to conventional high vacuum SEM. Several microscope types are available differing from each other by the maximum available gas pressure and the types of signals which can be used for investigation of specimen properties.Electrical non-conductors can be easily imaged despite charge accumulations at and beneath their surface. At high gas pressures between 10-2 and 2 torr, gas molecules are ionized in the electrical field between the specimen surface and the surrounding microscope parts through signal electrons and, to a certain extent, probe electrons. The gas provides a stable ion flux for a surface charge equalization if sufficient gas ions are provided.

Environmental cell studies of deformation and fracture

1990 ◽  
Vol 48 (4) ◽  
pp. 516-517
Author(s):  
H. K. Birnbaum ◽  
I. M. Robertson
Keyword(s):  
National Laboratory ◽  
Argonne National Laboratory ◽  
Damage Threshold ◽  
Chromatic Aberration ◽  
Good Choice ◽  
Point Of View ◽  
Deformation And Fracture ◽  
Environmental Cell ◽  
Gas Molecules ◽  
The University

Studies of the effects of hydrogen environments on the deformation and fracture of fcc, bcc and hep metals and alloys have been carried out in a TEM environmental cell. The initial experiments were performed in the environmental cell of the HVEM facility at Argonne National Laboratory. More recently, a dedicated environmental cell facility has been constructed at the University of Illinois using a JEOL 4000EX and has been used for these studies. In the present paper we will describe the general design features of the JEOL environmental cell and some of the observations we have made on hydrogen effects on deformation and fracture.The JEOL environmental cell is designed to operate at 400 keV and below; in part because of the available accelerating voltage of the microscope and in part because the damage threshold of most materials is below 400 keV. The gas pressure at which chromatic aberration due to electron scattering from the gas molecules becomes excessive does not increase rapidly with with accelerating voltage making 400 keV a good choice from that point of view as well. A series of apertures were placed above and below the cell to control the pressures in various parts of the column.

Recent Progress In High-Resolution Shadowing For Biological Transmission Electron Microscopy

1990 ◽  
Vol 48 (1) ◽  
pp. 510-511 ◽  
Author(s):  
Heinz Gross ◽  
Katarina Krusche ◽  
Peter Tittmann
Keyword(s):  
Heavy Metal ◽  
High Resolution ◽  
Freeze Drying ◽  
Atmospheric Conditions ◽  
Vacuum Equipment ◽  
Transmission Electron ◽  
Gas Atmosphere ◽  
Gas Molecules ◽  
Residual Gas ◽  
Backing Layer

Freeze-drying followed by heavy metal shadowing is a long established and straight forward approach to routinely study the structure of dehydrated macromolecules. Very thin specimens such as isolated membranes or single macromolecules are directly adsorbed on C-coated grids. After rapid freezing the grids are transferred into a suitable vacuum equipment for freeze-drying and heavy metal shadowing.To improve the resolution power of shadowing films we introduced shadowing at very low specimen temperature (−250°C). To routinely do that without the danger of contamination we developed in collaboration with Balzers an UHV (p≤10-9 mbar) machine (BAF500K, Fig.2). It should be mentioned here that at −250°C the specimen surface acts as effective cryopump for practically all impinging residual gas molecules from the residual gas atmosphere.Common high resolution shadowing films (Pt/C, Ta/W) have to be protected from alterations due to air contact by a relatively thick C-backing layer, when transferred via atmospheric conditions into the TEM. Such an additional C-coat contributes disturbingly to the contrast at high resolution.

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