Pore size and structure

The issues and challenges in molecular sieve science have dramatically changed in recent years and will continue to be redefined. As new and clever approaches to nanoporous materials are developed, the pore size and structural limitations that presently exist will no doubt be vanquished. As bolder endeavors expand the scope of this field, many new applications should also emerge. It seems the progress and innovations described in this chapter reflect a growing interdisciplinary nature in molecular sieve research. It is likely that the importance of large pore zeolites and molecular sieves will evolve in many nontraditional areas. 

Biocompatibility and Hemocompatibility Strength of Material Pore Size and Structure Surface-to-Volume Ratio Mass Transport through Device High Degree of Interconnected Cells Void Volume... 

The control of pore size and structure during preparation is a complex process that has been mastered by few manufacturers, but it is true to say that pore size distribution and uniformity is more readily achieved in silica particles than it is in polymeries. This is not to say that polymeries are inferior, because in contrast these stationary phases have a more uniform particle size. 

Table 4.1 Pore size and structural topographic species of various redox molecular sieves...

Bore, M.T., Pham, H.N., Switzer, E.E., Ward, T.L., Fukuoka, A., and Datye, A.K. 2005. The role of pore size and structure on the thermal stability of gold nanoparticles within mesoporous silica. Journal of Physical Chemistry B 109, 2873-2880. 

The structure breaker salts decrease the bound water whereas the structure maker salts Increase the bound water. To explain the observed bound water trend. It Is hypothesized that structure breakers decrease the critical pore size and structure makers Increase this value. The viscosities of aqueous salt solutions are used as criteria to separate structure breaker from structure maker salts. 

Polymer gels are an excellent example of an organic system that can be morphologically tailored. The synthesis of numerous polymer gels with a wide variation in the pore size and structure, and overall porosity has been achieved... 

Apart from the EDL structure and capacitance, the dynamical properties of the IL electrolytes confined in nanopores and its relationship with the effect of pore size and structure have also been investigated [592,593]. MD simulation demonstrated the confined cations moved faster than the anions of the [BMIMJlPFg] IL electrolyte inside MWCNTs, and the confinement remarkably decreased the ion dynamics [593]. 

The CMS membranes are prepared by carbonizing (under pyrolysing conditions) the precursor membranes in a high temperature tube furnace, as shown in Figure 15.4. The step-by-step method (several dwells) most commonly used as the protocol for the carbonization process is described elsewhere. Many researchers report different carbonization conditions in their research works illustrating very well that each precursor will need different protocols in order to be pore tailored for specific applications. " The carbonization process is the most important step for fabrication of CMS membranes and is used to tailor the pore size and structure of the carbon membranes. Therefore, how to control the carbonization conditions is crucial for the resulting CMS membrane performance. Su and Lua reported that the statistical 2" factorial... 

In the diffusion-limited case, the exchange time is limited by the diffusion coefficient of the solvent(s) and the pore size and structure of the gel. Diffusive processes are strongly temperature dependent. This is the reason why washing and exchange steps during APD processes are often carried out at moderate temperatures in the 40-70°C range. 

One of the most unique and useful features of the M41S family of materials is the ability to tailor both pore size and structure. Through the methods that will be described below, one may, in a systematic fashion, design a mesoporous material with regular, well-defined pore dimensions ranging from ca. 15 A to > 100 A. The well-documented approaches to accomplishing this pore size variation stand in stark contrast to the ability to accomplish such goals for traditional zeolitic materials. However, it should be pointed out that pore size control in amorphous materials has been successfully achieved in a number of examples [40]. 

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