Membrane inorganic oxide

A significant recent advance has been the development of MF and UF membranes composed of inorganic oxides.1113 These are currently produced by two main techniques ... 

Basically, three kinds of membranes are being studied inorganic oxide membranes, polymer-based membranes, and metal and metal alloy membranes. Some combinations of these are also used, such as impregnating inorganic oxide membranes with catalytic materials. A key term in this held is permselective membrane, which is a thin material that can allow a certain component of a mixture, but not other components, to pass through (or permeate) from one side to the other. 

A significant recent advance has been the development of microfiltration and ultrafiltration membranes composed of inorganic oxide materials. These are presently produced by two main techniques (a) deposition of colloidal metal oxide on to a supporting material such as carbon, and (b) as purely ceramic materials by high temperature sintering of spray-dried oxide microspheres. Other innovative production techniques lead to the... 

One final example of multiple layer MPL was presented by Karman, Cindrella, and Munukutla [172]. A four-layer MPL was fabricated by using nanofibrous carbon, nanochain Pureblack carbon, PIPE, and a hydrophilic inorganic oxide (fumed silica). The first three layers were made out of mixtures of the nanofibrous carbon, Pureblack, carbon, and PTFE. Each of these three layers had different quantities from the three particles used. The fourth layer consisted of Pureblack carbon, PTPE, and fumed silica to retain moisture content to keep the membrane humidified. Therefore, by using these four layers, a porosity gradient was created that significantly improved the gas diffusion through the MEA. In addition, a fuel cell with this novel MPL showed little performance differences when operated at various humidity conditions. 

Develop microporous inorganic oxide-based membranes of Ti02 with high proton conductivity that can operate at above 100°C with minimal water management problems. 

Membrane materials are available in various shapes, such as flat sheets, tubular, hollow fiber, and monolithic. Flat sheets have typical dimensions of 1 m by 1 m by 200 pm thickness. Tubular membranes are typically 0.5 to 5.0 cm in diameter and up to 6 m in length. The thin, dense layer is on either the inside or the outside of the tube. Very small-diameter hollow fibers are typically 42 pm i.d. by 85 pm o.d. by 1.2 m long. They provide a very large surface area per unit volume. Honeycomb, monolithic elements of inorganic oxide membranes are available in hexagonal or circular cross section. The circular flow channels are typically 0.3 to 0.6 cm in diameter (Seader and Henley, 2006). 

Most applications of GP use dense membranes of cellulose acetates and polysulfones. For high-temperature applications where polymers cannot be used, membranes of glass, carbon, and inorganic oxides are available, but they are limited in their selectivity. Almost all large-scale applications of GP use spiral-wound or hollow-fiber modules, because of their high packing density. 

Major Hazards Highly corrosive to the eyes, skin, and mucous membranes powerful oxidizing agent that ignites on contact or reacts explosively with many organic and inorganic substances. 

Shao, Z.G., Xu, H., Li, M. and Hsing, I.M. 2006. Hybrid Nafion-inorganic oxides membrane doped with heteropolyacids for high temperature operation of proton exchange membrane fuel cell. 177(7-8) 779-785. 

Blending of sulfonated PEEK with other polymers sueh as PPSU in sulfonated form or with inorganie eomponent such as SiCU and inorganic oxides like zirconia, as well as with solid heteropolyacids as HPA, TPA and Na-TPA or with BPO4, it is possible significantly to improve the membrane swelling behaviours, the mechanical properties and the proton conductivity. Other efforts have been earried to reaeh the same results following different... 

The ideal additive would enhance proton conductivity and stabihty. One demonstration of this was in a composite PFSA membrane using Pt nanoparticles supported on titania or silica [63]. The composite membranes when employed in MEAs demonstrated unhumidifled fuel cell performance comparable to that of a similar humidified fuel cell. Whether adding Pt to the membrane will help durability or hurt it is still a matter of some debate [64, 65]. Unfortunately, it is not commercially feasible at this time to add additional Pt to the MEA and so this approach while novel is not practical. The HPAs are known peroxide decomposition catalysts and so these inorganic oxides have been demonstrated to improve performance and decompose peroxide in fuel cells and if they could be immobilized would present a practical solution to this problem [66]. 

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