Materials surface area

Both xerogels and aerogels are characteristically high surface area materials (surface areas normally exceed 500 m2/g). Unlike wet gels, many uses exist for dried gels due to their high surface areas and small pore sizes (typically, < 20 nm diameters). Examples include catalyst supports (12.). ultrafiltration media (18), antireflective coatings (19-20), and ultra-low dielectric constant films. (Lenahan, P. M. and Brinker, C. J., unpublished results.)... 

Section Construction and coverage material Surface area, m2... 

The silica networks of mesoporous sihcas are terminated at the surfaces of the amorphous pore walls, thus resulting in terminal silanol groups on the walls. The density of the silanol groups of all mesoporous sihcas (1 to 3 nm 2) is somewhat lower than usually found for other typical silica materials (4 to 6 nm 2) [27], The specific surface areas of the different mesoporous silicas vary depending on their pore sizes, the thicknesses of their pore walls, and the density of their sihca networks. For some MCM-41- and MCM-48-type materials, surface areas of about 1000 to 1400 m2 g 1 have been reported. The surface areas of SBA-15-type materials can be > 600 m2 g 1 [27],... 

Surfactants have been explored widely for their effects on drug absorption, in particular using experimental animals (Gibaldi and Feldman, 1970 Gibaldi, 1976). Surfactants alter dissolution rates (of lipid materials), surface areas of particles and droplets, and membrane characteristics, all of which affect absorption. 

Material Surface Area (cmVg) Wt. Loss % per unit cnt per day... 

Material Surface area Pore volume [cm g- ] Pore diameter [A]... 

Type of Material Surface Area (MVM9 Void Volume (%)... 

Materials Surface Area (m2/g) Porous Volume (mL/g) Pore Diameter (A) BET parameter C... 

Other herbal materials prepared by roller compaction included St. John s wort (22) and Eschscholtzia californica Cham (23). Tableting of the granulated extract markedly reduced the problems associated with dust and material feed as well as the incidence of capping. Tablets produced from granulated extracts disintegrated three limes faster than those tabletted from the powder blend. Hygroscopicity of . californica Cham, extracts decreased after roller compaction due to decreased material surface area. 

As previously described, the parameters which affect the properties of the hydrogel affect the texture of the aerogel. Chitosan aerogel surface area can be doubled but the benefit of such an increase, which is clear in the first catalytic test (98% conversion, 12 h), becomes a drawback in the successive re-uses of the catalyst (second run 47% conversion). Therefore a balance has to be met between dispersion of the material (surface area) and the mechanical stabiUty of the chitosan beads. 

Figure 19. Plot of material surface area as a function of tethered complex, showing coUapse of pore structure as the amount of metal complex increases. [Adapted from (56).]...

Packing Materials Surface area Pore diameter Mean pore size Carbon content Loss on CH CN in Methyl red Capacity... 

Material Surface area (m /g) cNa C-p Cyclohexanol + cyclohexanone (M) Cyelohexanone/ eyelohexanol... 

Electrolyte Material Surface Area (m g ) Capacitance (Fg- ) Voltage (V) Energy Density (Wh kg ) Power Density (Wkg- ) ESR (E2) References... 

Figure 4.19 Water sorption test on two calcium oxide samples. Samples were exposed at 100-200 Pa water partial pressure at 23 °C. Sample A was prepared by SAES according to a proprietary process to increase material surface area and porosity.

These mass loss tests consist of preparing metallic coupons, cleaning them before testing, weighing them before exposure, exposing them to the corrosive media, post-test removal of visible corrosion products, and reweighing. The corrosion rate is calculated from the mass loss measured, converted to a volume of metal loss by the material density, and finally to a corrosion rate by dividing this volume by the material surface area and the test time. 

In the case of microporous materials, surface areas estimated from N2 adsorption usually suffer from activated diffusion of N2, because of the low temperature of adsorption. Therefore, CO2 adsorption at room temperature was also used for pore structure characterization of the activated carbons. Figures 7 and 8 show the CO2 isotherms of samples with the same burn-off as those used for the N2 adsorption isotherms (Figures 4 and 5). Adsorption isotherms show that the amount of CO2 adsorbed, is affected by the degree of activation and increases considerably for carbons produced from demineralized lignite. 

Carbon Material Surface Area (m2.gr ) Electrolyte Differential Capacitance (x 10 F.cm 2) Specific Capacitance (F.g2)... 

Type of Adsorbent Adsorbent Material Surface Area (mVg) Strength of the Adsorbent Type of Compounds Remarks... 

Name Material Surface area m /in fteeVol % Nmn. diam. mm... 

Material Surface Area, BET Method (nnVg) Uptake (wt.%) Conditions Refs. 

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