Agglomerate structure

The other approach is more complicated and requires a deeper knowledge of the agglomerate structure or yields more fitting parameters. In this approach, the porous-electrode equations are used, but now the effectiveness factor and the agglomerate model equations are incorporated. Hence, eq 64 is used to get the transfer current in each volume element. The gas composition and the overpotential... 

For agglomerated structures, the dipolar interaction between two neighboring crystals contributes to the anisotropy energy. This contribution increases when the inter-crystal distance decreases. 

Hao Y., Qunfeng Z., Fei W., Weizhong Q., Guohua L. Agglomerated CNTs synthesized in a fluidized bed reactor Agglomerate structure and formation mechanism. Carbon, 2003, 41(14), 2855-2863. 

From the above results we can propose the following mechanism for hexagonal MCM-41 synthesis. At low crystallization temperature or short crystallization time a fibrous agglomerate structure is often observed by SEM on intermediate samples. The 100 and 200 reflections are not detected by XRD and the value of the specific surface area is low. This reflects the initial step of synthesis which is generally referred to the nucleation step in zeolite synthesis. After this step, the 100 and 200 reflections are present on the XRD diffraction pattern. The value of the specific surface area is between 700 and 900 m /g. The fibrous agglomerate structure disappears and crystals of MCM-41 appear. This corresponds to the crystallization step. Finally if both the synthesis temperature and time are continuously raised, a triphasic mixture MCM-41, MCM-50 and amorphous phase is identified by XRD. The... 

According to the porosity data of Uchida et al. [102] the matrix of carbon grains (20-40 nm) forms an agglomerated structure with a bimodal psd. Primary pores (micropores, 5-40 nm) exist within agglomerates, between the carbon grains. Larger, secondary pores (macropores, 40-200 nm) form the pore spaces between agglomerates. The relation between the relative pore volume fractions of the two pore types depends on the contents of PFSI and PTFE. Due to their molecular size these components are not able to penetrate micropores. They affect only the macropore volume. The experimental study revealed that an increased PFSI content leads to a decrease of the macropore volume fraction. The opposite effect was found for PTFE. 

An electron micrograph of an alumina agglomerate is shown in Fig. 8.1. An agglomerate can be considered to be composed of Np primary particles of radius apo. There is usually some variation in size among the primary particles but this is neglected in the theory. The factors that determine primary particle size are discussed in Chapter 12. The agglomerate structure has a characteristic radius, R, which for Fig. 8.1 is of the order of a few tenths of a micron. The value of R is defined more completely later. 

Fractal-like agglomerate structures form as coalescence ceases. 

In the second edition, I have sharpened the focus on aerosol dynamics. The field has grown rapidly since its original applications to the atmospheric aerosol for which the assumption of panicle sphericity is u.sually adequate, especially for the accumulation mode. Major advances in the eighties and nineties came about when we learned how to deal with (I) the formation of solid primary panicles, the smallest individual panicles that compose agglomerates and (ii) the formation of agglomerate structures by collisions. These phenomena, which have important industrial applications, are covered in two new chapters. One chapter describes the extension of classical coagulation theory for coalescing... 

Fig. 3.23. Scanning electron micrographs of PAM obtained from 3BS pastes (a) porous PAM (b) agglomerate structure of macroporous mass (c) agglomerate comprising particles of various shapes [38].

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