Surface Porosity Measurements

To describe fouling in membrane pores, was the parameter quantified from 2D images [6]. Pj is the fraction of the pore surface in which a fluorescent foulant has been detected  

The processing of the CSLM images included identifying the features to be analyzed and then segmenting and extracting the measurements of interest. The 

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D.M. Mattox, autoradiography for nondestructive/noncontaminating surface porosity measurements, in R. Dobrozemky, et al., (Eds.), Proceedings of the 7th International Vacuum Congress and 3rd International Conference on Solid Surfaces, vol. 3, Pergamon Press, 1977, p. 2659. 

Physical properties of catalysts also may need to be checked periodically, includiug pellet size, specific surface, porosity, pore size and size distribution, and effective diffusivity. The effectiveness of a porous catalyst is found by measuring conversions with successively smaller pellets until no further change occurs. These topics are touched on by Satterfield (Heterogeneous Cataly.sls in Jndustiial Practice, McGraw-Hill, 1991). 

The single-point BET surface area measurement was used to check for open pores. The results for some soft and hard carbon samples heated at 700°C and 1000°C are presented in Table 2 for comparison. The hard carbon samples studied here have about ten times more open porosity than the soft carbons. 

Methods for synthesizing highly porous microspheres were investigated, and surface area measurements were used to confirm the porous nature of the samples [19]. A high surface area was measured and was compared with the calculated surface area value. The measured value was 35 times that of a nonporous particle, indicating the extensive porosity of the spheres. The surface area was also used to explain the drug release mechanisms in the pores of these systems. 

The water for the substrate was distilled from a Stokes still and foamed in a 600-ml. medium porosity sintered glass funnel the foam was removed several times by sweeping the surface. The water gave adequately stable base line readings for both the surface potential and surface pressure measurements. 

Porous Membrane DS Devices. The applicability of a simple tubular DS based on a porous hydrophobic PTFE membrane tube was demonstrated for the collection of S02 (dilute H202 was used as the scrubber liquid, and conductometric detection was used) (46). The parameters of available tubular membranes that are important in determining the overall behavior of such a device include the following First, the fractional surface porosity, which is typically between 0.4 and 0.7 and represents the probability of an analyte gas molecule entering a pore in the event of a collision with the wall. Second, wall thickness, which is typically between 25 and 1000 xm and determines, together with the pore tortuosity (a measure of how convoluted the path is from one side of the membrane to the other), the overall diffusion distance from one side of the wall to the other. If uptake probability at the air-liquid interface in the pore is not the controlling factor, then items 1 and 2 together determine the collection efficiency. The transport of the analyte gas molecule takes place within the pores, in the gas phase. This process is far faster than the situation with a hydrophilic membrane the relaxation time is well below 100 ms, and the overall response time may in fact be determined by liquid-phase diffusion in the boundary layer within the lumen of the membrane tube, by liquid-phase dispersion within the... 

Computer Controlled Vacuum Microbalance Techniques Of Surface Area And Porosity Measurements. K. A. Thompson and E. L. Fuller, Langmuir 3 (5) (1987)699-703... 

Fig. 6 Comparison between X-ray refraction and high pressure mercury intrusion results of mean pore sizes and specific surface corresponding to Al203-samples of varying mean porosities. The differences of the calculated mean pore sizes may be explainable by considering the different pore models. The specific surface S measured by X-ray refraction solely is caused by geometric characteristics of the sample and agree well with the results of mercury porosimetry using a cylindrical capillary model.

Surface roughness A is defined as the ratio of the geometric ( oeo) to the BET (5bet) surface areas (Helgeson, 1971). For a perfectly smooth surface, without internal porosity, the two surface area measurements should be the same, i.e., A = 1. For nonideal surfaces of geometric spheres, the roughness can be related directly to the particle diameter d and the mineral density p such that... 

Physical characterization of TBO includes particle size and size distribution measurement by laser diflraction (macroporosity) as well as specific surface area measurement (microporosity). Particle size measurement by FSSS (Fisher Sub-Sieve Sizer), as also sometimes used, is misleading, because of the porosity of the TBO particles. An empirical relationship between FSSS and particle size measured by laser scattering can, however, be detected if the microporosity of the samples is uniform (constant blueing conditions). 

Porosity can be measured indirectly via the particle and bulk densities as described by equation 5.2. This is the same method as currently used in many commercial instruments for surface area measurement by permeability in that a known mass of powder is packed into a known volume (i.e. the bulk density is known) and the porosity is evaluated from the knowledge of particle density. 

This result suggests that, for this family of structures at least, the value of 1.6 mL g 1 provides sufficient weakness to allow total breakdown and full access to all of the catalyst surface. This inference is also supported by a comparison of results obtained with the best commercial silica gels and with a pyrogenic or "fumed silica (Cabosil) formed by flame hydrolysis of SiCl4. The latter has no pore structure, and no such structural limitations. That the two exhibit similar activities indicates that the silica gel had disintegrated to the level at which nearly all of the surface contributed to the polymerization. Furthermore, once friability of the solid is obtained because the pore volume is sufficiently high, activity can still be influenced by the surface area. However, these are only general trends, and some small exceptions are evident in the data in the table as well. It is the structure itself, rather than any porosity measurement, that determines friability. 

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