Particle-loaded membranes preparation

Ware GM, Price G, Carter L, Eitenmiller RR (2000) Liquid chromatographic preparative method for isolating ergot alkaloids, using a particle-loaded membrane extracting disk. J AOAC Int 83 1395-1399... 

A membrane emulsification method has been applied for the preparation of glutaraldehyde-cross-linked CS particles loaded with BSA as a model dmg. The diameter of the particles depended on the membrane pore size and was in the range of 0.65-26.06pm. ... 

Both the approaches were combined together to evaluate the performance of these HPA-loaded membranes with small particles [17] and MEA stabilization techniques to yield a stabiUzed MEA for operation at 120°C and 35% relative humidity (RH). MEAs were prepared using Nafion /phosphotungstic acid composite membranes with phosphotungstic acid (HPW) particle size of 30-50 nm and the HPW additive stabilized by substituting its protons with cesium counter ions. The Nafion in the membrane and electrodes were simultaneously converted to the Cs form by an imi-exchange process. The melt processability of the Nafion in the Cs form permitted the MEA to be heat treated at 200°C and 30 atm, promoting the development of a durable membrane/electrode interface. The prior stabilization of the HPW permitted MEA reprotonation with minimal additive loss which was confirmed by FTIR, TGA, and in situ electrochemical impedance spectroscopy (EIS). 

Fig. lc. Electronmicrograph of isolated sarcoplasmic reticulum membranes loaded with calcium oxalate46. The preparation was negatively stained with potassium phosphotungstate. Size and shape of the calcium oxalate precipitates differ considerably. Fine particles which are present on the surface of most vesicles are clearly visible. In all pictures the length of the bars measures 0.1 pm... 

Taylor et al.8 were the first to report an electrochemical method for preparation of MEAs for PEMFCs. In their technique, Pt was electrochemically reduced and deposited at the electrode membrane interface, where it was actually utilized as an electrocatalyst. Nation, which is an ion exchange polymer membrane, is first coated on a noncatalyzed carbon support. The Nafion-coated carbon support is then immersed into a commercial acidic Pt plating solution for electrodeposition. Application of a cathodic potential results in diffusion of platinum cations through the active Nation layer. The migrated platinum species are reduced and form Pt particle at the electrode/membrane interface only on the sites which are both electronically and ionically conductive. The deposition of Pt particles merely at the electrode/membrane interface maximizes the Pt utilization. The Pt particles of 2-3.5 nm and a Pt loading of less than 0.05 mg cm-2 were obtained employing this technique.8 The limitation of this method is the difficulty of the diffusion of platinum... 

Another drawback of a realistic mockup is that preparing complete sensors is extremely costly. Since only the behavior of the MEMS component is of interest, we decided to build a test bed that enabled unpackaged membrane chips to be tested. For the severest possible shock load, the membrane was positioned vertical to the air and thus to the particle stream. The intensity, velocity, and size of the particles could be adjusted individually to separate the effects of energy and momentum. 

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