Brunauer-Emmette-Teller

A vast amount of research has been undertaken on adsorption phenomena and the nature of solid surfaces over the fifteen years since the first edition was published, but for the most part this work has resulted in the refinement of existing theoretical principles and experimental procedures rather than in the formulation of entirely new concepts. In spite of the acknowledged weakness of its theoretical foundations, the Brunauer-Emmett-Teller (BET) method still remains the most widely used procedure for the determination of surface area similarly, methods based on the Kelvin equation are still generally applied for the computation of mesopore size distribution from gas adsorption data. However, the more recent studies, especially those carried out on well defined surfaces, have led to a clearer understanding of the scope and limitations of these methods furthermore, the growing awareness of the importance of molecular sieve carbons and zeolites has generated considerable interest in the properties of microporous solids and the mechanism of micropore filling. 

In writing the present book our aim has been to give a critical exposition of the use of adsorption data for the evaluation of the surface area and the pore size distribution of finely divided and porous solids. The major part of the book is devoted to the Brunauer-Emmett-Teller (BET) method for the determination of specific surface, and the use of the Kelvin equation for the calculation of pore size distribution but due attention has also been given to other well known methods for the estimation of surface area from adsorption measurements, viz. those based on adsorption from solution, on heat of immersion, on chemisorption, and on the application of the Gibbs adsorption equation to gaseous adsorption. 

PCNTs are marketed commercially by Hyperion Catalyst International Inc. (Cambridge, Mass. USA), based on a patent [22] Graphite Fibrils. The method of production appears to be essentially the same as that used for Endo PCNTs. The material consists of MWCNTs, 10-20 nm in diameter and 10-12 j,m long, with ca. 10 coaxial layers within each tube. The tubes have hollow cores of ca., 2 nm diameter. The Brunauer-Emmett-Teller (BET) analysis characteristically shows a surface area of 250 m /g, true density 2.0 g/cm- and bulk density of less than 0.1 g/cm (95% void vol). 

In addition to actual synthesis tests, fresh and used catalysts were investigated extensively in order to determine the effect of steam on catalyst activity and catalyst stability. This was done by measurement of surface areas. Whereas the Brunauer-Emmett-Teller (BET) area (4) is a measure of the total surface area, the volume of chemisorbed hydrogen is a measure only of the exposed metallic nickel area and therefore should be a truer measure of the catalytically active area. The H2 chemisorption measurement data are summarized in Table III. For fresh reduced catalyst, activity was equivalent to 11.2 ml/g. When this reduced catalyst was treated with a mixture of hydrogen and steam, it lost 27% of its activity. This activity loss is definitely caused by steam since a... 

Selected OSC values are reported in Table 8.1 for ceria and cerium-zirconium mixed oxides. These results confirm that the isomorphous substitution of Ce4+ by Zr4+ ions clearly improves the catalyst stability. BET (Brunauer, Emmett, Teller) area of ceria treated at 900°C is close to 20m2g 1 while it amounts to 35 15 m2g 1 for most mixed... 

Winter M., Novak P. and. Monnier A. Graphites for Lithium-ion Cells The Correlation of the First-Cycle Loss with the Brunauer-Emmett-Teller Area. J. Electrochem. Soc., 145, 428-435 (1998). 

Specific surface area (SSA), total pore volume and average pore diameter were measured by N2 adsorption-desorption isotherms at 77K using Micromeritics ASAP 2020. The pore size was calculated on the adsorption branch of the isotherms using Barrett-Joyner-Helenda (BJH) method and the SSA was calculated using the Brunauer-Emmett-Teller (BET) method. 

Nitrogen adsorption was performed at -196 °C in a Micromeritics ASAP 2010 volumetric instrument. The samples were outgassed at 80 °C prior to the adsorption measurement until a 3.10 3 Torr static vacuum was reached. The surface area was calculated by the Brunauer-Emmett-Teller (BET) method. Micropore volume and external surface area were evaluated by the alpha-S method using a standard isotherm measured on Aerosil 200 fumed silica [8]. Powder X-ray diffraction (XRD) patterns of samples dried at 80 °C were collected at room temperature on a Broker AXS D-8 diffractometer with Cu Ka radiation. Thermogravimetric analysis was carried out in air flow with heating rate 10 °C min"1 up to 900 °C in a Netzsch TG 209 C thermal balance. SEM micrographs were recorded on a Hitachi S4500 microscope. 

Hall et al. (2001) measured the biosorption of copper by P. syringae, fitting the experimental data to the Freundlich, Brunauer-Emmett-Teller (BET), and Langmuir equations. Meaningful maximum sorption capacities... 

Structural characterization of the prepared Co/alumina catalysts was studied by using the following techniques Brunauer-Emmett-Teller (BET), temperature-programmed reduction (TPR), H2 chemisorption by temperature-programmed desorption (TPD) with 02 pulse reoxidation, and powder x-ray diffraction (XRD). 

Brunauer-Emmett-Teller (BET) adsorption describes multi-layer Langmuir adsorption. Multi-layer adsorption occurs in physical or van der Waals bonding of gases or vapors to solid phases. The BET model, originally used to describe this adsorption, has been applied to the description of adsorption from solid solutions. The adsorption of molecules to the surface of particles forms a new surface layer to which additional molecules can adsorb. If it is assumed that the energy of adsorption on all successive layers is equal, the BET adsorption model [36] is expressed as Eq. (6) ... 

Many models have been developed that deal with the sorption properties of wood in the presence of moisture these have been discussed in a number of works (e.g. Skaar, 1972 Siau, 1984). They can be approximately divided into sorption models, such as the Brunauer-Emmett-Teller (BET) model, or solution models (such as the Hailwood-Horrobin, H-H, model). The sigmoidal shapes of sorption or desorption isotherms can be deconvoluted into two components. These are often taken to represent a monomolecular water layer (associated with the primary sorption sites, OH groups), and a multilayer component where the cell wall bound water molecules are less intimately associated with the fixed cell wall OH groups. 

Popper and Bariska (1972) studied the moisture sorption properties of wood chemically modified with acetic (or phthalic) anhydride and analysed the results using Brunauer-Emmett-Teller (BET) theory and the H-H model. Acetylation was found to reduce the number of sorption sites, whereas little effect was noted with phthaloylation. By dividing the sorption isotherm into a monolayer component and a multilayer component using the H-H model, it was shown that there was a large reduction in the... 

Finally, the other factor that could contribute to the improved performance of the nanotubule electrode is its higher surface area. This higher surface area would make the true current density at the nanotubular material lower than at the control material. In order to access the contribution of surface area, Brunauer-Emmett-Teller (BET) measurements were made on both the nanotubular and control electrodes [124], The specific surface areas were found to be 40 m g (nanotubule electrode) and 13 m g (control electrode). This factor of 3 increase in surface area cannot account for the factor of 12 improvement in capacity observed at the highest current... 

Ball et al. investigated the effect of carbon surface area on carbon corrosion at 1.2 V for 24 h and found that, for commercial carbon blacks, cumulative carbon corrosion correlated with carbon BET (Brunauer Emmett Teller) area, although when analyzed as specific carbon corrosion (weight of carbon corroded per unit of carbon area), some variation was observed. The effect of Ft on carbon corrosion has also been studied and conflicting results have been reported. Roen, Paik, and Jarvi found that Ft did increase carbon corrosion... 

BET equation See Brunauer-Emmett-Teller equation. be e te i kwa-zhon betula oil See methyl salicylate. bech-3-l3, 6il ... 

EA = elemental analysis IR = infrared spectroscopy PXRD = powder X-ray diffraction BET = Brunauer-Emmett-Teller method (specific BET surface area) and BJH = Barrett-)oyner-Halenda method (determination of pore volume and diameter), both determined by nitrogen physisorption ... 

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