BET specific surface area

The Fe-B nanocomposite was synthesized by the so-called pillaring technique using layered bentonite clay as the starting material. The detailed procedures were described in our previous study [4]. X-ray diffraction (XRD) analysis revealed that the Fe-B nanocomposite mainly consists of Fc203 (hematite) and Si02 (quartz). The bulk Fe concentration of the Fe-B nanocomposite measured by a JOEL X-ray Reflective Fluorescence spectrometer (Model JSX 3201Z) is 31.8%. The Fe surface atomic concentration of Fe-B nanocomposite determined by an X-ray photoelectron spectrometer (Model PHI5600) is 12.25 (at%). The BET specific surface area is 280 m /g. The particle size determined by a transmission electron microscope (JOEL 2010) is from 20 to 200 nm. 

KoTHmex activated carbon fiber fabrics AW-1101 (BET specific surface area of 880m /g, average pore diameter of 2nm) was provided by Taiwan Carbon Technology Co. Ltd. The support is pretreated in a boiling aqueous solution of 6.5wt.% HNO3 for 1 h. Then the support is rinsed with distilled water, air-dried for 12h at room temperature and for 5h at 393 K. BET specific surface area of the ACF is 950m /g. 

The following natural precursors have been selected for KOH activation coal (C), coal semi-coke (CS), pitch semi-coke (PS) and pitch mesophase (PM). An industrial activated carbon (AC) was also used. Activation was performed at 800°C in KOH with 4 1 (C KOH) weight ratio, for 5 hours, followed by a careful washing of the samples with 10% HC1 and distilled water. The activation process supplied highly microporous carbons with BET specific surface areas from 1900 to 3150 m2/g. The BET surface area together with the micro and the total pore volume of the KOH-activated carbons are presented in Table 1. The mean micropore width calculated from the Dubinin equation is designed as LD. 

As detailed in the literature background, it is often attempted to relate the irreversible capacity either with the BET specific surface area or with the presence of surface groups. Below, we will show two experiments, which disclaim these kinds of correlations. 

Figure 1 presents the plot of the BET specific surface area vs the irreversible capacity measured for graphite samples milled in different atmospheres and sometimes post-treated by pyrolytic carbon deposition. The experimental values are quite scarce and, contrarily to several claims [7-9], there is not any linear dependence between these two parameters. It seems that the linearity would exist only for samples from the same family with comparable microtextures. 

Figure 1. Relation between the BET specific surface area and the irreversible capacity x of graphite samples treated in different conditions, (a) 10 h in vacuum (b) 10 h in vacuum + pyrolytic carbon deposition (c) 10 h under Hf (d) 10 h under H2 + pyrolytic carbon deposition (e) 10 h under O2 (f) 10 h under O2 + pyrolytic carbon deposition (g) 20 h in vacuum (h) 20 h in vacuum + pyrolytic carbon deposition. 

In this paper, we presented new information, which should help in optimising disordered carbon materials for anodes of lithium-ion batteries. We clearly proved that the irreversible capacity is essentially due to the presence of active sites at the surface of carbon, which cause the electrolyte decomposition. A perfect linear relationship was shown between the irreversible capacity and the active surface area, i.e. the area corresponding to the sites located at the edge planes. It definitely proves that the BET specific surface area, which represents the surface area of the basal planes, is not a relevant parameter to explain the irreversible capacity, even if some papers showed some correlation with this parameter for rather low BET surface area carbons. The electrolyte may be decomposed by surface functional groups or by dangling bonds. Coating by a thin layer of pyrolytic carbon allows these sites to be efficiently blocked, without reducing the value of reversible capacity. 

The XRD patterns demonstrated that the MCM-22 zeolites were well crystallized and pillars have been created in the MCM-36 sample, respectively. Thus, the last material exhibited a typical intense peak at 29 2°, corresponding to a Aspacing of 4 nm. The textural properties of solids (Table 1) indicated that the pillaring in MCM-36 resulted in increases in BET specific surface area and external surface area compared with the MCM-22 zeolite. 

Platinum-based nanoparticles (e.g., Pt [1-15], Pt-Re [10,15], and Pt-W [5,6,15]) supported on granular activated carbon (KOH-activation, BET specific surface area 3100 m2/g, pore volume 1.78 cm3/g, average particle size 13 pm, average pore size 2.0 nm, Kansai Netsukagaku Co. Ltd. [32]) were mainly used as the dehydrogenation catalysts in the present study. 

The comparison of catalytic properties was made under identical reaction conditions, among three important candidate catalysts, namely, the Pt/y-Al203, Au/a-Fe203, and Cu Ce, x02 y systems [50], The catalytic tests were performed in the reactant feed containing CO, H2, C02, and HzO — the so-called reformate fuel. The effects of the presence of both C02 and H20 in the reactant feed on the catalytic performance (activity and selectivity) of these catalysts as well as their stability with time under reaction conditions have been studied. The composition of the prepared samples and their BET specific surface areas are presented in Table 7.6. The results obtained with the three catalysts in the presence of 15 vol% COz and of both 15 vol% COz and 10 vol% H20 in the reactant feed (with contact time wcat/v = 0.144 g sec/cm3 and X = 2.5) are shown in Figure 7.12. For comparison, the corresponding curves obtained under the same conditions but without water vapor in the feed are also shown in Figure 7.12. 

Prior to nitrogen adsorption experiment to determine surface properties, ACC sample was degassed at 130°C under vacuum (up to 10 torr) for 12 h. The adsorption data were obtained at the Central Laboratory of Middle East Technical University (METU) with a Quantachrome Autosoib-l-C/MS apparatus over a relative pressure ranging from 10" to 1. The BET specific surface area, total pore volume, micropore volume, mesopore volume, and pore size distribution, PSD, of ACC were yielded by using the software of the apparatus. 

Fig. 6 a-d. Schematic illustration of the ways in which the BET specific surface area can differ from that derived from particle size measurements All particles have a similar equivalent spherical diameter but in a the particle is solid b the particle is porous c the particle has a rough surface d the particle is anisotropic... 

The N2 adsorption /desorption isotherms (Figure 2) for calcined STO shows abrupt step at P/Po = 0.1—0.4 and no obvious hysteresis loop at low relative pressure, indicating the pore size of this materials is uniform. The BET specific surface area and BJH pore diameter are 934 m2/g and 4.3nm, respectively. 

The BET specific surface area, mesopore volumes, and pore wall thickness of the calcined and water-treated samples are given in Table 3. BET surface area of the samples prepared with Cm surfactants were found to be less affected by hydrothermal treatment. When the samples synthesized without TPA+ subjected to hydrothermal treatment the sharp inflection in the isotherm became very broad indicating wide distribution of pores. In contrast, the mesopore distribution of the samples prepared with TPA was found to be less affected by hydrothermal treatment. For the samples prepared without TPA, the mesopore volume was found to decrease sharply and the pore diameter was broadened over a large range indicating loss of the mesopore structure. Addition of TPA was found to minimize the structural collapse and thereby helps to preserve the mesoporosity. 

Sbet - BET specific surface area V, - single-point total pore volume w - pore width at the maximum of the pore size distribution calculated using the BJH method with the corrected form of the Kelvin equation [34]. 

BET specific surface area AS(BET) total pore volume Vp BJH mean pore diameter dgjHl average pore diameter Dh = 4 Vp/AS(BET). 

The pore volume and surface area of sol-PILB-Cn samples are closer to those of the corresponding MCM41 solid prepared with silica fume and the same surfactant used in the preparation of sol-PILB-Cn, rather than to that of sol PILB. For example, the total pore volume and BET specific surface area of sol-PILB-C16 are 0.84 cm3/g and 756 m2/g, respectively, much larger than those for sol-PILB, 0.24 cm3/g and 404 m2/g, but comparable to those for MCM41-C16, 0.94 cm3/g and 790 m2/g. These results suggest that treatment with surfactants of quaternary ammonium salts alters the structure of the sol pillared clay radically. 

The BET specific surface area [28] was calculated in the relative pressure range between 0.04 and 0.2. The total pore volume was determined from the amount adsorbed at a relative pressure of 0.99 [28], The primary mesopore volume and external surface area were evaluated using the as-plot method [24, 28, 29] with the reference adsorption isotherm for macroporous silica [29], The pore size distributions were determined using the Kruk-Jaroniec-Sayari (KJS) equation [30] and the calculation procedure proposed by Barrett, Joyner and Halenda (BJH) [31]. 

Data for calcined samples dioo - XRD (100) interplanar spacing, Sbet - BET specific surface area, V, - total pore volume, Vp - primary mesopore volume, Sex - external surface area, wkjs - primary mesopore diameter. Data for uncalcined samples mreS due - mass percent of residue at 1263 K, mSdir - mass decrease in the temperature range of the surfactant decomposition and desorption of the decomposition products (between about 373 and 623 K). Notes a - no peak on XRD spectrum, d,0o cannot be evaluated, b - no linear region on the Os-plot, which would be suitable for the Vp and Sex evaluation. XRD and adsorption data (except for those for HR-A2 sample) taken from Refs. 24 and 26. Thermogravimetric data for DS-AD taken from Ref. 19. 

The new composite (SC-155) and some of its precursors and derivatives were characterized by LOI (loss on ignition), XRD ( X ray diffraction), 1R (infrared spectra), BET specific surface area, nitrogen adsorption desorption isotherms, pore size distribution (mercury porosimetry), dynamic methylene blue adsorption and SEM (Scanning Electron... 

Typical OAN Numbers from DBPA, BET Specific Surface Area, Relative Conductivity, Dispersibility, and Purity of Various Conductive Carbon Blacks from Different Manufacturing Processes... 

FIGURE 8.8 Normalized capacitance (gravimetric capacitance divided by the BET specific surface area) vs. average pore size of a series of CDCs models of the structure of EMI and TFSI ions. (From Largeot, C., et al., J. Am. Chem. Soc., 130, 2730, 2008. With permission.)... 

FIGURE 8.10 Gravimetric capacitance in various electrolytes (lmolL-1 H2S04, 6molL 1 KOH, and ImolL-1 TEABF4 in acetonitrile) vs. BET specific surface area for a series of bituminous coal-derived carbons activated by KOH at 800°C. (Adapted from Raymundo-Pinero, E., et al., Carbon, 44, 2498, 2006.)... 

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