Small-angle neutron scattering membranes

Roche and co-workers used SAXS and small-angle neutron scattering (SANS) to study the morphology of 1200 EW Nafion membranes in the acid and neutralized forms with a range of water contents. ... 

Small-angle neutron scattering Transmission electron microscopy Scanning probe technologies Membrane and vapor pressure osmometry Light-scattering methods Nuclear magnetic resonance... 

Furthermore, in 2001, Ballard entered an alliance with Victrex to produce two new membrane alternatives. One membrane is based on sulfonated poly(arylether) ketone (a variant of PEEK) supplied by Victrex, which may be better suited to PEMFC fabrication applications. In March 2002, U.S. Patent 6,359,019 was issued to Ballard Power for a graft-polymeric membrane in which one or more trifluorovinylaromatic monomers are radiation graft polymerized to a preformed polymeric base. The strucmres of BAM membranes have been studied by way of small-angle neutron scattering (SANS) [97]. The study of the ionomer peak position suggests the existence of relatively small ionic domains compared to Nalion, despite large water content. Phase separation in the polymer matrix is possibly crucial for the membrane s mechanical and transport properties. 

Alumina membranes containing monodispersed cylindrical pores have been characterised by a combination of three ditferent techniques Field emission scanning electron microscopy, mercury porosimetry and small angle neutron scattering (SANS). SANS is a method which can provide details of the highly anisotropic texture in such model porous materials. 

Other recently developed methods have also become available for adsorption studies. The availability of synchrotrons as excellent x-ray sources allows x-ray studies at liquid interfaces (Mohwald et al. 1990, Meunier Lee 1991, Daillant et al. 1991). The same applies for small angle neutron scattering (SANS, based on the different scattering cross section of hydrogen and deuterium). The use of SANS for dynamic studies of structures in membranes and at interfaces has been shown by different authors (Grundy et al. 1988, Bayerl et al. 1990, Vaknin et al. 1991). The method is characterised by a fast data acquisition and should allow dynamic investigations at freshly formed surfaces, as discussed by several authors (Blake, Howe, Penfold, private communication). 

G. Gebel, O. Dial, C. Stone, Microstructure of BAM (R) membranes A small-angle neutron scattering study. Journal of New Materials for Electrochemical Systems 2003, 6,17-23. 

A combination of characterization techniques for the pore structure of meso-and microporous membranes is presented. Equilibrium (sorption and Small Angle Neutron Scattering) and d)mamic (gas relative permeability through membranes partially blocked by a sorbed vapor) methods have been employed. Capillary network and EMA models combined with aspects from percolation theory can be employed to obtain structural information on the porous network topology as well as on the pore shape. Model membranes with well defined structure formed by compaction of non-porous spherical particles, have been employed for testing the different characterization techniques. Attention is drawn to the need for further development of more advanced sphere-pack models for the elucidation of dynamic relative permeability data and of Monte-Carlo Simulation for the analysis of equilibrium sorption data from microporous membranes. 

For the case of equilibrium methods, for mesoporous materials gas porosimetry is complemented by Small Angle Neutron Scattering to obtain information on pore size distribution. For microporous membranes the extraction of structural information from the equilibrium sorption measurements can be based on techniques like Grand Canonical Monte Carlo Simulation. 

There are other modern spectroscopic methods such as X-ray photoelectron spectroscopy (XPS), small angle neutron scattering (SANS), Raman spectroscopy (RS), electron spinning resonance (ESR) and nuclear magnetic resonance (NMR). These techniques are well known in the membrane field. Static secondary ion mass spectrometry (SSIMS), energy dispersive X-ray spectroscopy (EDS), laser confocal scanning microscopy (FCSM) and environmental scanning electron microscopy (ESEM) can also be added to new microscopic methods to characterize the membranes [84]. 

Mosdale R., Gebel G., Pineri M. Water profile determination in a running proton exchange membrane fuel cell using small-angle neutron scattering. J. Membr. Sci. 1996 118 269-277 Motupally S., Becker A.J., Weidner J.W. Diffusion of water in Nafion 115 membranes. J. Elec-trochem. Soc. 2000 147(9) 3171-3177... 

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