Nitrogen adsorption technique

Measurement of Surface Area. The Teachability determined by these methods is usually reported as g/cm day. The total surface area of particulate material can be assessed 1) by assuming a particle shape e.g.spherical) and estimating the number of particles, or 2) by measurements using the Brunauer-Emmett-Teller (BET) nitrogen adsorption technique ( ). Unfortunately, the BET method measures the area of surfaces to which nitrogen has access this is not necessarily the same as the area to which a solution has access. Access by solutions requires much larger pore areas. 

Materials. The degree of exchange and surface area of the faujasites are given in Table I. The experimental surface areas v ere obtained by nitrogen adsorption techniques, using the Langmuir method. 

Table 3.4 The composition of typical end-member particles from the Clyde and Humber. Fe and Mn were determined following extraction by hydroxylamine hydrochloride-acetic acid. Carbon and nitrogen were determined using an elemental analyser. Specific surface area (SSA) was determined using a BET nitrogen adsorption technique (nd = not determined). REM and MEM denote river and marine end-members, respectively.

As an alternative to networks prepared with n-decane, the toluene-modified copolymers exhibit narrower pore size distribution and smaller pore volume. A substantial part of the porous volume is provided by small voids [319] located within the initially swollen primary microgels. These pores are poorly accessible even to the small molecules of methanol. This is the reason why the surface area of the toluene-modified copolymers calculated from adsorption of methanol vapors proves to be markedly smaller than that determined by the conventional nitrogen adsorption technique [320]. In addition to micropores with a diameter below 15 A, the polymer exhibits mesopores with diameters up to 300 A, representing the space between the microgels and their aggregates. Owing to the increased portion of small pores, the surface area of the toluene-modified networks can achieve large values and exceed that of the polymen prepared with pre-cipitants [321, 315]. In order to raise both the pore volume and the pore size of solvent-modified materials, a precipitant needs to be added to toluene [322-326]. 

Another important physical property of the ash zeolites is their pore radius Rp. This parameter helps in studying the adsorption properties of zeolites as an adsorbent. Rp can be correlated with the specific surface area SSAbet, which can be determined by nitrogen adsorption technique (i.e., by employing BET method and the relationship, Rp = 2 VpISSAbet> where Vp is the pore volume) [44]. The pores are assumed to be cylindrical in shape for natural zeolites Clinoptilolite and Mordenite, for which SSAbet generally lies between 11-16 m and 115-120 m /g, respectively. The trend depicted in Fig. 2.4 exhibits an initial increase in Rp with an increase in SSAbet, up to 20 m /g, beyond which it decreases sharply [8]. This trend violates the inverse relationship between the two parameters as mentioned above. 

Figure 10.13 Comparison of SSAs determined by the Blaine test and the nitrogen adsorption technique. (Data from Arvaniti, E. C. et al., Materials and Structures, 1-15, 2014a Mantellato, S. et al.. Impact of sample preparation on the specific surface area of synthetic ettringite. In preparation, 2015b.)...

Sample preparation is the crucial step during surface area and porosity measurement by nitrogen adsorption technique. As explained in Section 10.3.4.2, the reliability of the obtained values will depend mainly on the method employed to stop cement hydration and the degassing procedure (temperature, pressure and time). For each sample, measurements should be repeated at least three times. 

The PSD, the SSA and the porosity of cementitious materials are frequently measured as they have a direct effect on the kinetics of cement hydration and/or on other engineering properties of concrete. In this chapter the crucial parameters in analysing these parameters by LD and nitrogen adsorption techniques are described. 

Several properties of the filler are important to the compounder (279). Properties that are frequentiy reported by fumed sihca manufacturers include the acidity of the filler, nitrogen adsorption, oil absorption, and particle size distribution (280,281). The adsorption techniques provide a measure of the surface area of the filler, whereas oil absorption is an indication of the stmcture of the filler (282). Measurement of the sdanol concentration is critical, and some techniques that are commonly used in the industry to estimate this parameter are the methyl red absorption and methanol wettabihty (273,274,277) tests. Other techniques include various spectroscopies, such as diffuse reflectance infrared spectroscopy (drift), inverse gas chromatography (igc), photoacoustic ir, nmr, Raman, and surface forces apparatus (277,283—290). 

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). 

The samples were characterized by chemical analysis induced coupled plasma and atomic absorption techniques apparatus), nitrogen adsorption isotherms (at 77 K), XRD patterns ( Siemens diffractometer and (3uKa radiation), SEM observations (Hitachi S800 apparatus of the University C. Bernard, Lyon I) and TGA-DTA (Setaram 92-12 apparatus). The IR spectra were recorded with a Bruker IPS 48 FTIR spectrometer. 

Minimization of agricultural losses from soil toxins Toxins from soils appear to be responsible for inhibition of nitrogen fixation, metabolism and nodulation in legumes. Removal of toxins could be achieved by proper adsorption techniques and also by growing companion plants that contribute organic matter to microoranisms which help to destroy or degrade toxic chemicals. 

For membranes with pore diameters smaller than 3.5 nm, the nitrogen adsorption/desorption method based on the widely used BET theory ean be employed. This measurement technique, however, is good only for pore diameters ranging from 1.5 nm to 100 nm ( = 0.1 micron). Typical data from this method are split into two portions adsorption and desorption. The nitrogen desorption curve is usually used to describe the pore size distribution and corresponds better to the mercury intrusion curve. Given in Figure... 

The specific surface area was measured by nitrogen adsorption at -195 C. The cumene cracking reaction was conducted by pulse technique under the following conditions O.IO g catalyst, H, flow rate 75 ml/nin, pulse volume 1 ul. 

The BET surface areas and pore diameters were determined by nitrogen adsorption/ desorption isotherms at 77 K using a static volumetric technique (Quantachrome Autosorb 1). Before the physisorption measurements the samples were outgassed at 100° C for 15 hours under vacuum. 

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