Mesopore volume fraction

Kim and Yang [14] prepared ACNF from electro spun PAN nano fibers activated in steam at 700-800 °C and found that the specific surface area of the ACNF activated at 700 °C was the highest but the Mesopore volume fraction was the lowest. However, the work by Lee et al. [38] showed an opposite result. Song et al. [21] investigated the effect of activation time on the formation of ACNF (ultra-thin PAN fiber based) activated in steam at 1000 °C. Ji et al. [39] made mesoporous ACNF produced from electros-pun PAN nano fibers through physical activation with silica and conducted chemical activations by potassium hydroxide and zinc chloride to increase specific surface area and pore volume of ACNF [40]. It must be pointed out that different methods and conditions of activation lead to very different physical properties and adsorption capacities for ACNF. 

The type of mesostructure obtained depends strongly on the surfactant to inorganic ratio. In fact, there is a close correlation between the surfactant to solvent ratio in the phase diagram of a surfactant and the surfactant to inorganic ratio in the mesostructured materials obtained. Alberius et al. demonstrated this correlation by the so-called general predictive synthesis approach. They used the phase diagrams of the water-surfactant system to guide the synthesis of mesoporous silica and titania films. There was a very close correlation between the values of the volume fraction of the surfactant over which different phases are obtained in the water-surfactant system and in the silica-surfactant and titania-surfactant systems. 

X-ray data revealed no considerable effect of grinding on the phase composition of AC [19]. The total pore volume of composite catalysts varies only slightly, while their micropore and mesopore volumes and the specific surface area changes non-monotonically (Tables 1, 2) which will be discussed later. For the finest fraction of AC, specific surface area decreases markedly, while the micropore volume for fiactions less than 0.25 nun is negligible (Table 3). Probably, the number of cracks per particle decreases for fine fiactions of AC, so grinding leads only to further disappearance of cracks due to percussion riveting. However, it has no effect on the specific activity of AC (related per gram) (Fig.9)... 

Table III shows XRD and porosimetry data for calcined USY and AFS zeolites. All samples show shrinkage of the unit cell to comparable values following calcination. As a result, calcined samples are compared at similar silica-alumina framework ratios. All calcined samples have well developed microporous structures and comparable total pore volumes. These porosimetry data confirm that the hydrothermally dealuminated materials contain a significant fraction of mesopores relative to chemically dealuminated materials. The extensive washing given to AFS-1 results in higher micropore surface area and volume compared to AFS-2 and suggest that AFS-2 contains occluded fluoroaluminate and fluorosilicate compounds within the microporous structure.

Figure 1. SANS of evacuated mesoporous Figure 2. Dependence of I(Q) for sample silica, SIM (dp - 6nm). SANS contains two SIM in the Porod Scattering region (at Q = components (a) at low Q - Porod Scattering 10-2A-1) on fractional volume filling of (b) at high Q - Diffraction. mesopores, 0, with matched benzene.

The Brunauer method assumes that the slope of the t-plot, even in non-linear regions, is proportional to the surface of the not yet filled micropores. The analysis is thus limited to t values lower than the second linear portion of the /-plot. The cumulative surface of micropores can be evaluated as minus S t, i e. as the fraction of the total surface that cannot be explained by the mesopores. ext being overestimated, it should not be surprising that Vs underestimates the true microporous volume. 

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