Probe Method Using Gas Adsorption

Since Avnir and Pfeifer s pioneer works regarding the characterization of the snrface irregnlarity at the molecnlar level by applying the fractal theory of snrface science, molecnlar probe method nsing gas adsorption has played an important role in the determination of the snrface fractal dimensions of the porons materials. 

There are two molecnlar probe methods available for the determination of the snrface fractal dimension. One is the mnltiprobe method (MP method), which nses several kinds of mnltiprobe molecnles with different molecnlar sizes. If the probe molecnle is varied throngh a series of spheres with radins r, the snrface fractal dimension is given by 

The MP method is widely applicable to varions solid snrfaces in whose system Mmono can be accmately determined. It was recently reported that even for the micropore whose pore width is greater than the bilayer thickness of N2 (abont 0.7 mn), surf,MP can be determined nsing Eq. (14) if the monolayer evalnation fit for the micropore is introdnced. 

The other molecnlar probe method is the single-probe method (SP method), which is separately proposed by Pfeifer 

The detailed stractnre of the layer of the adsorbed molecnles is not important and is regarded as a liqnid film. 

N ono is the number of adsorbed molecules to form a monolayer for each probe molecule and isurf,MP is the surface fractal dimension determined by using the MP method. The probe molecules need not to be spherical, provided they belong to a homologous series for which the ratio [linear extent to 

The MP method is widely applicable to various solid surfaces in whose system can be accurately determined. It was 

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Besides the molecular probe method using gas adsorption,107 162 recently, the TEM image analysis method163"167 has been applied to evaluate the surface fractal dimension of porous materials. The most attractive fact in this method is that the pores in different size ranges can be extracted from the TEM images which include contributions from many different pore sizes by the inverse fast Fourier transform (FFT) operation by selecting the specific frequency range.165 167... 

F,SP Surface fractal dimension determined by single-probe method using gas adsorption the... 

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