Interparticle pores

For L=NH3 (1) and L=Pr2NH (3), the isotherms are of type II as expected for non-porous materials [27]. Sample 2 shows a significant uptake at 0.6

narrow particle-size distribution which results in a more regular packing with interparticle pores of size similar to that of the particles [27]. The latter shows that the ligand-assisted synthesis does not only allow one to affect the total surface area and particle size, but also the size distribution which is an important tool for tailoring the particle properties. 

Sample 5 is close to an H2-type hysteresis, whereas 6 and 7 can be tentatively assigned to H3- and Hi-type hystereses, respectively [27]. The hystereses are caused by capillary condensation in interparticle pores and the shape is an indication of a particular particle morphology. Sample 7 has a more regular narrow mesopore size distribution, whereas sample 5 is more complex with pores of... 

Recently various kinds of porous materials have been developed and their properties and structures have been gathering great concerns in science. There are two types of pores of intraparticle pores and interparticle ones[l]. The intraparticle pores are in the primary particle itself, while the interparticle pores originate from the interparticle void spaces. Zeolites are the most representative porous solids whose pores come from the structurally intrinsic intraparticle pores. The pore geometry can be evaluated by their crystallographic data. The carbon nanotube of which pore wall is composed of graphitic sheets is also the... 

Density Types Density Definitions Solid Material Volume Volumes in Definition Closed- Open- Interparticle Pore Pore Void Volume Volume Volume ... 

Figure 7-12 Dynamic and total liquid holdup as a function of average gas interparticle pore velocity in a 10.2-cm-i.d. column packed with 1.9-cm x 1.9-cm ceramic cylinders.22...

Therefore, it is conceivable that the micropore and macropore are interparticle pores, while the mesopore presumably is the intra-particle pore. During the course of calcination, the connection of interparticle was destroyed and this finally resulted in the vanishing of macropore. Because the mesopore was the intraparticle pores, it had relative fine thermal stability though the pore size was enlarged in the calcination. The reasons may be attributed to the steric dispersant effect of non-ionic surfactant PEG [12]. In the synthesis course, PEG gave steric hindrance to the assembling of mesophase and improved the pore structure. 

Comparison of the porous structure of different columns was discussed in Section 3.2 here we emphasize that with a packed column the ratio of particle size to the average interparticle pores (space) is on the level of 3-3.5 while with monolithic columns trough-pores are on the level of 6000 A and silica material is only about 1 u thick, which makes this ratio 0.5-0.2 or about 10 times smaller, thus significantly decreasing the time needed for analyte molecules to diffuse into the mesoporous space for the interaction with main surface. This allows for much faster flow rates without the loss of the dynamic equilibrium conditions (otherwise known as the slow mass transfer term (C) in the Van Deemter equation). 

A packed column as used in chromatography is a porous medium with a multimodal pore distribution. There are usually two modes in this distribution, but three-mode distributions may also be encormtered, as we see later. In a classical column made by packing the porous particles of an adsorbent, the first mode is made of the interparticle pores, the fraction of the column volume through which the mobile phase flows. The second one is made of the intrapartide pores, within... 

The average dimension of the interparticle pores in a packed bed is of the order of a fraction of the particle diameter. As the particles are generally convex and the packed bed is not consolidated (f.e., the particles are not fused but remain independent), the structure of the extrapartide space is relatively simple, the porosity distribution is rather narrow, and the channel anastomosis that is illustrated in Figure 5.3 does not leave any significant part of the bed isolated over more than a few particle diameters [75]. 

In the modeling of chromatography, the contributions of aU the phenomena that contribute to axial mixing are lumped into a single axial dispersion coefficient. Two main mechanisms contribute to axial dispersion molecular diffusion in the interparticle pores and eddy diffusion. In a first approximation, their contributions are additive, and the axial dispersion coefficient, Di, is given by... 

The pore structure of zeolite membranes is formed by arrays of intergrown zeolite particles or zeolite particle packings with interparticle pores filled with another material. The intracrystalline pores are a part of the crystallographic structure and are the ones which should be responsible for the selectivity. 

In carbon fiber felts, however, only one kind of pores, interparticle pores, are observed among the fibers (Fig. 27.4). The surface of each fiber is smooth and no pores are inside of the fibers. Felts composed of polyacrylonitrile (PAN)-based and isotropic pitch-based carbon fibers were used as sorbents in the present work. 

Accurate values of the small areas existing in macropore systems make it difficult to use Eq. (8-26) to calculate d for interparticle pores. Hence the average radius for systems such as the UO2 pellets discussed in Example 8-6 should be obtained by integrating under the cumulative-volume-vs-u curve shown in Fig. 8-7. Also a single value of d has no meaning for a bidisperse pore system such as that in an alumina pellet. Thus using the total pore volume in Table 8-5 for the low-pressure pellet gives... 

The N2 physisorption measmements show that the composite material has a higher BET surface area than the nanoZSM-5 and a much larger total pore volume. The adsorption isotherm of nanoZSM-5 is a type I isotherm with an extra adsorption step at high relative pressure values due to interparticle pore... 

Based on their origin Intraparticle pores Interpartide pores Intrinsic Intraparticle pores Extrinsic intraparticle pores Rigid interparticle pores Flexible interpartide pores... 

Based on their origin, the pores can be classified into two classes, Intraparticle and interparticle pores. The intraparticle pores are further classified into two, intrinsic and extrinsic intraparticle pores. The fonner class owes its origin to the crystal stmcture, of which... 

As an example, spray drying of nanosized porous particles yields spherical agglomerates with a bimodal pore size distribution the pores according to the primary particles (intraparticle pores) and the secondary pores (interparticle pores) made by the void fraction of the agglomerated nanobeads. Figure 3.19 shows spherically agglomerated nanoparticles that build up a porous bead. For a given size dp of the nanopartides the pore diameter of the interstitial pores... 

The small interparticle pore size of HPLC columns requires stable, uniform, spherical particles to avoid their packing together in a fashion which will block uniform flow through these tiny passages. Mobile phase solvents must be filtered to remove micron-size particles which could plug up these interstitial pores and block or channel mobile phase flow. 

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