Acid structure, surface area

The surface acid-base properties of polycrystalline MgO surfaces have been assessed by means of thermogravimetry and DSC of desorption of pyridine and CO2 in the room temperature to 400 °C temperature range [44]. The endotherms and corresponding AH of desorption were discussed in relation with results determined previously using differential adsorption calorimetry and taking into account the structure, surface area and defects of the studied surfaces. 

Chemical composition. Crystalline Structure, Surface Area and Acid-base Properties of MgyAlOx, MgO and AI2O3 Oxides. 

An advanced solution to the problem of decreasing the free mobility of the electrolyte in sealed batteries is its gel formation. By adding some 5-8 wt.% of pyrogenic silica to the electrolyte, a gel structure is formed due to the immense surface area (-200-300 m2 g ) of such silicas, which fixes the sulfuric acid solution molecules by van der Waals bonds within a lattice. These gels have thixotropic properties i.e., by mechanical stirring they can be liquefied and used to Filled into the... 

The physicochemical properties of carbon are highly dependent on its surface structure and chemical composition [66—68], The type and content of surface species, particle shape and size, pore-size distribution, BET surface area and pore-opening are of critical importance in the use of carbons as anode material. These properties have a major influence on (9IR, reversible capacity <2R, and the rate capability and safety of the battery. The surface chemical composition depends on the raw materials (carbon precursors), the production process, and the history of the carbon. Surface groups containing H, O, S, N, P, halogens, and other elements have been identified on carbon blacks [66, 67]. There is also ash on the surface of carbon and this typically contains Ca, Si, Fe, Al, and V. Ash and acidic oxides enhance the adsorption of the more polar compounds and electrolytes [66]. 

The presence of o-qulnone surface waves seems, at the present time, to be coincidental to activation particularly In the case of ascorbic acid oxidation. On the other hand. Its presence may serve as a criterion of cleanliness and activation. Thus, the surface waves at 0.250 and 0.190 are Indicators or signatures for active GCE electrodes and should be used as diagnostic for a clean GCE surface as Is the hydrogen fine structure for platinum (31). It Is unfortunate that the o-qulnone peaks do not appear to be proportional to the surface area as Is the platinum fine structure. 

Because of the larger surface area (compared with solid-ceramic refractories) the chemical resistance of fibers is relatively poor. Their acid resistance is good, but they have less alkali resistance than solid materials because of the absence of resistant aggregates. Also, because they have less bulk, fibers have lower gas-velocity resistance. Besides the advantage of lower weight, since they will not hold heat, fibers are more quicHy cooled and present no thermal-shock structural problem. 

To evaluate the catalytic activity or to investigate the reaction mechanism, planar electrodes with well-defined characteristics such as surface area, surface and bulk compositions, and crystalline structure have often been examined in acidic electrolyte solutions. An appreciable improvement in CO tolerance has been found at Pt with adatoms such as Ru, Sn, and As [Watanabe and Motoo, 1975a, 1976 Motoo and Watanabe, 1980 Motoo et al., 1980 Watanabe et al., 1985], Pt-based alloys Pt-M (M = Ru, Rh, Os, Sn, etc.) [Ross et al., 1975a, b Gasteiger et al., 1994, 1995 Grgur et al., 1997 Ley et al., 1997 Mukeijee et al., 2004], and Pt with oxides (RuO cHy) [Gonzalez and Ticianelli, 2005 Sughnoto et al., 2006]. 

Catalyst Mg/Me Structure Acid sites, pmol/ga Basic sites, pmol/g1 Surface area, m2/g... 

Fig. 8. Calculated values of (top) /(0), (center) /(75), and (bottom) J (653) for acid-unfolded apoMb, pH 2.3, 25°C. The horizontal lines show the mean values of J (75) (0.19 ns rad-1) and /(653) (0.020 ns rad-1), and the 10% trimmed mean value of J (0) (0.97 ns rad-1). The average buried surface area, calculated using the values of Rose and co-workers (Rose et al., 1985) and averaged over a seven-residue window, is also shown in the center figure (solid line, no data points, right-hand scale). Black bars indicate the positions of the helices in the folded structure of myoglobin.

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