Permeability as a function of temperature

Figure 19. Methanol permeability as a function of temperature and diffusiv-ity data evaluated using the atomistic simulation method.138 Reprinted from Journal of Electrochemical Society, X. Zhou, Z. Chen, F. Delgado, D. Brenner, R. Srivastava, J. Electrochem. Soc. 154, B82 (2007)- Reproduced by permission of the Electrochemical Society.

FIGURE 27.11 (See color insert following page S88.) H2 permeability as a function of temperature and RH. Upper limit (solid line) defined by crossover losses (assuming no contribution from O2 crossover), lower Umit (dotted Une) defined by electrode ionomer film-transport requirements, and data are for wet and dry Nafion 1100 EW-based membranes. (Reproduced from Gasteiger, H.A. and Mathias, M. F., in Proceedings of the Symposium on Proton Conducting Membrane Fuel Cells III, 2003. The Electrochemical Society of America. With permission from The Electrochemical Society, Inc.)... 

The rates of change (slopes of the curves) of many important properties (such as the refractive index, surface tension, and gas permeabilities) as a function of temperature, the value of the dielectric constant, and many other optical and electrical properties, often change considerably at Tg. These changes enable the measurement of Tg by using techniques such as refractometry and dielectric relaxation spectroscopy. Refractometry provides results which are similar to those obtained from dilatometry, because of the correlation between the rates of change of the specific volume and of the refractive index with temperature. Dielectric relaxation spectroscopy is based on general physical principles which are similar to those in dynamic mechanical spectroscopy, the main difference being in its use of an electrical rather than a mechanical stimulus. 

Therefore, although rather cumbersome, the Tree-volume theory permits one to prepare theoretical plots of permeability as a function of temperature, penetrant pressure, and arantphous volume fraction in the rubbery polymer. 

Figure 9. Dry oxygen permeability as a function of temperature for the electron grafted organofunctlonal silane, Saran 468. Barex 210 and EVAL-E (E 44Z ethylene). The data are presented as a function of increasing temperature (after Watanabe (15)).

Measurement of the initial permeability as a function of temperature can therefore be used as a material characterisation method. The value of Tq depends only on the composition the verticality of the permeability drop at the Curie point indicates the degree of homogeneity in the sample composition (Cedillo et at., 1980 Valenzuela, 1980). 

Fig. 4.47. Initial permeability as a function of temperature in Zn,Nii, spinels for various compositions.

Cedillo, E., Ocampo, J., Rivera, V. Valenzuela, R. (1980). An apparatus for the measurement of initial magnetic permeability as a function of temperature. Journal of Physics F Scientific Instruments, 13, 383-6. 

Fig. 5.4. Initial permeability as a function of temperature for Zno 4Nio.36Fej04 femtes. Short sintering times (at 1150°C) result in a lower degree of homogeneity and smaller permeability variations near the Curie point (Globus Valenzuela, 1975).

Figure 5.12 Model prediction of permeability as a function of temperature. Modes of transport are indicated for the following pore sizes activated diffusion (d = 6.8 A), surface diffusion (d = 10 A), Knudsen diffusion (d = 10 A), parallel transport (d = 10A), and resistance In series transport (d rraii = 6.8A, d/a,ge = loA, Xk = 0.8)...

Figure 5.2 Robeson diagram showing CO2/N2 selectivity versus CO2 permeability for the membranes BPDA-PEC2000-ODA2/1 and BPDA-PEG2000-BNZ 2/1 after different temperatures of treatment. An insert showing their CO2 permeability as a function of temperature is also included.

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