Membrane ultra-thin

The mechanism of facilitated transport involves using the metal ion only in its reduced state in the oxidized state the oxygen-carrying capacity is virtually nil. It is thus natural that electrochemical processes should be attempted to improve both the flux and selectivity obtained with the membranes described above by exploiting this 02 capacity difference. For example, the best of the ultra-thin membranes developed by Johnson et al. [24] delivered oxygen at a rate equivalent to a current density of only 3 mA/cm2, at least an order lower than that achievable electrochemically. Further, the purity was but 85% and the lifetime of the carrier less than a year. 

Miura S, Teramura Y, Iwata H (2006) Encapsulation of islets with ultra-thin poly ion complex membrane through polyethylene glycol)-phospholipids anchored to cell membrane. Biomaterials 27 5828-5835... 

Teramura Y, Kaneda Y, Iwata H (2007) Islet-encapsulation in ultra-thin layer-by-layer membranes of poly(vinyl alcohol) anchored to poly(ethylene glycol)-lipids in the cell membrane. Biomaterials 28 4818 -825... 

Immobilization of bilayer membranes as ultra thin polymer films... 

R.L. Riley, H.K. Lonsdale, L.D. LaGrange and C.R. Lyons, Development of Ultra-thin Membranes, Office of Saline Water Research and Development Progress Report No. 386, PB 207036 (January, 1969). 

Myler S, Eaton S, Higson S. Poly(o-phenylenediamine ultra-thin polymer-film composite membranes for enzyme electrodes. Analytica Chimica Acta 1997, 357, 55-61. 

We report here on the structure and gas transport properties of asymmetric membranes created by the Langmuir-Blodgett deposition of ultra-thin polymeric lipid films on porous supports. Transmission and grazing angle FTIR spectroscopy provide a measure of the level of molecular order in the n-alkyl side-chains of the polymeric lipid. The level of orientational order was monitored as a function of the temperature. Gas permeation studies as a function of membrane temperature are correlated to the FTIR results. 

Planar SOFCs are composed of flat, ultra-thin ceramic plates, which allow them to operate at 800°C or even less, and enable less exotic construction materials. P-SOFCs can be either electrode- or electrolyte- supported. Electrolyte-supported cells use YSZ membranes of about 100 pm thickness, the ohmic contribution of which is still high for operation below 900°C. In electrode-supported cells, the supporting component can either be the anode or the cathode. In these designs, the electrolyte is typically between 5-30 pm, while the electrode thickness can be between 250 pm - 2 mm. In the cathode-supported design, the YSZ electrolyte and the LSM coefficients of thermal expansion are well matched, placing no restrictions on electrolyte thickness. In anode-supported cells, the thermal expansion coefficient of Ni-YSZ cermets is greater than that of the YSZ... 

Jansen, J. C., Buonomenna, M. G, Figoli, A., and Drioli, E. (2006), Asymmetric membranes of modified poly(ether ether ketone) with an ultra-thin skin for gas and vapour separations,/. Membr. Sci., 272,188-197. 

An ideal pervaporation membrane should consist of an ultra thin defect free skin layer (dense layer) supported by a porous support. The skin layer is perm-selective and hence responsible for the selectivity of the membrane. However, the porous support also plays an important role in overall performance of the membrane. The effect of the porous support, of a composite membrane, on the permeation properties of the membrane is discussed in details in the composite membranes... 

Ma SH, Lepak LA, Hussain RJ, Shain W, Shuler ML. An endothelial and astrocyte co-culture model of the blood-brain barrier utilizing an ultra-thin, nanofabricated silicon nitride membrane. Lab Chip 2005 5 74-85. 

The most demanding support requirements are those for ultra thin micro-porous gas separation membranes, which are currently being developed in several research organisations worldwide including ECN (Petten, the Netherlands). In principle, a mesoporous Knudsen or UP membrane can serve as support for these membranes if the defect density in the substrate surface, i.e. the mesoporous layer, is low enough. Indeed, the quality of the Knudsen or UF membrane as support for a microporous gas separation membrane should be higher than is usually needed for the UF or Knudsen function [4]. This means that not every mesoporous ceramic membrane is a suitable support for micro-porous or dense amorphous gas separation membranes. 

Fig. 8.27. Three dimensional picture of a ultra thin microporous silica membrane on a y-alumina support (pore diameter 4 nm), obtained with atomic force microscopy. From de Lange et al. [46].

With very smooth, high quality y-alumina supporting layers on a a-alumina support ultra-thin (100 nm) silica membranes with a pore diameter of 0.45-0.5 nm could be obtained. High quedity membranes with low defect levels are obtained in a two-step coating process. The thermal stability of these systems is limited to about 500°C and relatively low water partial pressures. Reseeirch to improve this is necessary. 

G.Z. Cao, H.W. Brinkman, J. Meijerink, K.J. de Vries and A.J. Burggraaf, Pore narrowing and formation of ultra thin yttria-stabilised zirconia layers in ceramic membranes by chemical vapor deposition. /. Am. Cer. Soc., 76 (1993) 2201-2208. 

H. Suzuki, Composite membrane having a single layer of an ultra thin film of cage shaped zeolite and process for production thereof. US patent 5.069.794. 

In asymmetric supported membranes the use of permeability data can give rise to much confusion and erroneous conclusions for several reasons. In most cases the layer thickness is not precisely known and usually it is not known whether this layer is homogeneous or has property gradients (e.g. a "skin" and a more porous part). In many cases the material of the layer penetrates the support to some extent and so it is not possible to separate properties of separation layer and support without giving account of the interface effect. Finally, even if all these complications can be avoided, a comparison based on separation layer properties expressed in terms of permeabilities can give a completely wrong impression of the practical possibilities (as done in e.g. Ref. [109]). This is illustrated by comparison of hydrogen permeabilities of ultra-thin silica layers (see Tables 9.14-9.16) with other materials such as zeolites and metals. The "intrinsic" material properties of these silica layers are not impressive ... 

The interfaclal-polymerization technology for the preparation of ultra-thin composite membranes with its self-sealing capability... 

We have completed experiments label the ionic domains. We have found evidence of a precipitation phenomenon of particles of iron oxide or hydroxide when an iron form of membrane was exchanged by different other ions like K+, Na+, etc. We therefore have analyzed these particles by different techniques -like X rays, Mossbauer spectroscopy, magnetic measurements and electron microscopy- with two goals in mind. First of all the formation of ultra thin particles is very important in different domains and especially in catalysis when these membranes are used in the solid polymer electrolyte process. Second, we expect some correlation between the sizes and distribution of precipitates with the starting ionic domains. 

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