Nitrogen absorption

Table 9 shows the classification system for blacks most commonly used in mbber. The ASTM numbering system is based on the fundamental particle si2e of the black. Particle si2e is deterrnined by several methods, including iodine absorption, nitrogen absorption, and light scattering. 

Surface Area. The most important features influencing the performance of carbon blacks are aggregate size and surface area. Surface area is measured by gas- and Hquid-phase adsorption techniques, and depends on the amount of adsorbate required to form a surface monolayer. If the area occupied by a single-adsorbate molecule is known, a simple calculation will yield the surface area. A low temperature nitrogen absorption method, based on the original method of Bmnauer, Emmett, and Teller (BET) (30), has been adopted by ASTM as standard method D3037-86 (2). 

Porosity and surface area are routinely measured by nitrogen absorption-desorption, mercury intrusion, and low-angle X ray. The electron microscope (EM) provides direct visual evidence of pore size and pore-size distribution. Thus, a combination of EM and conventional methods of pore-size measurement should provide reliable information on the pore structure of polymers. 

For haffle trays, the coefficient equation given under packed columns, the values of m = 1.18 and n= 0.44 with Ci depending on the system. For example, for a nitrogen/absorption oil system, Ci = 0.00250. See the reference and Table 10-48 for more details. 

This technique has also been used in combination with nitrogen absorption to study the pore structure of some excipients, particularly MCC in both the powdered and compacted state. The intraparticulate porosity of MCC has been shown to be unaffected by tableting the interparticular pores, however, are gradually reduced in size [38]. Recently this method has been used to evaluate the internal structure of tablets prepared from microcapsules [150]. 

The low-frequency band in the spectrum of sample Af was superposed on a rather intense high background absorption band its exact shape could not be determined. The conclusion that these bands are due to the presence of CO at the surface follows from their close similarity to those found upon adsorption of CO on the same samples. Hence, dissociative chemisorption of C02 does indeed take place. However, the CO bands observed upon dissociative adsorption of C02 are much weaker than those produced by CO directly adsorbed as such. This becomes evident if we compare them with the nitrogen absorption bands in Figs. 8 and 9 where... 

Nitrogen absorption studies were carried out on the three materials to learn of any differences in their porosity (Table 3). 

Fig. 35. Effect of N2 adsorption at 77 K on CO-precovered (low-0) LaCrC>3 samples out-gassed at HOOK for coverages ranging from 6 = 1 (5.33 kPa) to0 - 0. (left) nitrogen absorption region and (right) CO absorption region (unpublished data).

Acetamide and Glycocoll absorb little nitrogen, and the quantity of the latter seems to depend upon the nitrogen absorption capacity of the respective acids. 

Continuous heating of the reduced metal is stated to result in a small amount of nitrogen absorption,9 as also exposure of the finely divided reduced metal at the ordinary temperature to nitrogen.10... 

To assess the thermal stability of the polymers and the effect of calcination on the porosity of the materials, samples of POSS copolymer were calcined under a steady flow of oxygen [78]. For each temperature studied, a sample was heated at 10 °C/min and allowed to remain at the set temperature for a period of 200 min. After being allowed to cool to room temperature, nitrogen absorption was used to determine the surface area. The reported results show a steady decrease in accessible surface area as the calcination temperature is increased. TG results showed that, at 400 °C, the mass lost by the sample is almost enough to account for all the organic component of the polymer and that the residue was essentially a mesoporous unordered silica. 

The partial IR spectrum of acid Subfraction 1 shows IR absorption at 3460 cm because of the pyrrolic nitrogen N-H absorption of carba-zole-like compounds. Amide carbonyl absorption appears at 1685 cm" The partial IR spectrum of acid Subfraction 2 shows the same two IR bands and additional bands at 3585 cm and 1650 cm owing to phenols and a second amide type. The partial IR spectrum of acid Subfraction 3 shows phenol absorption at 3585 cm S pyrrolic nitrogen absorption at 3460 cm S and strong carbonyl absorption at 1695 cm and 1725 cm characteristic of carboxylic acid dimers and monomers. In addition, absorption of hydrogen-bonded carboxylic acid and phenolic hydroxyl groups can be seen in the region of 3500-2300 cm" ... 

Nitrogen absorption isotherms and the hysterisis loops are affected by the nature of A1 distribution in ZSM-5, with shape of the loop being more symmetrical and larger for a more uniform distribution (11). The shape selectivity of ZSM-5 catalysts (12) and the hydrophobicity (13, 14) are dependent on the zoning of A1 in the crystals. 

Large, hard, transparent, mesoporous silica spheres1282 (see Figure 8.55) were synthesized in one step by using oil-in-water emulsion chemistry under basic conditions with cationic surfactants and TBOS. The pores are shown by TEM and nitrogen-absorption studies to be monodispersed in size, with total surface area over 1000 m2/g. 

Void volume can be calculated using this equation after determining the surface area by nitrogen absorption (BET method) or by filling the voids with liquid. Typical values of void volume are 0.6-0.7 cm /g for carbon black and 0.5-0.97 cm /g for silica. 

The total surface area or specific surface area (area/unit weight) is determined by the nitrogen absorption method known as the BET (Brunauer, Emmett, and Teller) absorption isotherm of an inert gas. The principle of this technique is based on the monolayer adsorption of nitrogen at low temperature, which has a fixed spherical volume. Thus, the amount of nitrogen adsorbed is proportional to the total surface area of the sample. 

Surface areas were determined using the B.E.T. method with nitrogen absorption at -196°C on a Carlo Erba instmment... 

FIGURE 8.24 Flow diagram of an unsegmented flow system with distillation. S = sample Ri and R2 — acidic and alkaline reagents R(1 — coiled reactor RC2 = coiled reactor for nitrogen absorption DU — distillation unit N2 = nitrogen stream H — heated glass helix WC = water cooled condenser PS = sample carrier stream D = detector. For details, see text. 

Table 5. Corrected relative intensities of some nitrogen absorptions for various thermal decomposition temperatures of MDI-based polymers3...

The alternative to sapphire and its complement is diamond. Type II diamond is transparent for wavelengths of 0.4 fjim and above, except between 4 and 6 ji,m where two-phonon absorption bands occur. Type I diamonds have an additional nitrogen absorption band at around 7.5 xm. The initial cost of diamond windows is more than offset by their performance, which allows very-low-mass optical plugs and cells to be used, and thus there is a considerable... 

Figure 19.13 shown the mesopore size distribution obtained nitrogen absorption-desorption of an aggregated colloidal silica slurry. 

Tsu] Tsuchiyama, T, Takaki, S., Thermodynamics of Nitrogen Absorption into Solid Solution in Fe-Cr-Mn Ternary Alloys , Mater. Sci. Forum, 426—432, 957—962 (2003) (Experimental, Meehan. Prop., Phase Diagram, Phase Relations, Thermodyn., 8)... 

Kinetics measurements of nitrogen absorption in liquid alloys at 1600°C show that Cr decreases slightly the absorption rate of nitrogen [1967Cho], The transfer of N across flic gas/metal interlace is controlled by the transport in the metal. 

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