Nanostructured, electroactive and bioapplicable materials

1.5. Characterization Methods for Porous Materials
Reliable porosity characterization methods are important for developing porous
materials. To evaluate exact pore parameters such as pore size, size distribution and
surface area, the most commonly used methods include, among others, gas sorption
measurement, mercury porosimetry, small angle X-ray scattering, fluid flow methods
(permeation and diffusion), flow microcalorimetry and electron microscopy.
The gas sorption measurement is a widely used nondestructive method to analyze
pore size and distribution. Its best working range is from micropores up to 200 nm pore
width. 58 Gas sorption measurement is one of the most applicable methods for sol-gel
silica materials which are either mesoporous or microporous. This method will be
reviewed later in more detail.
Mercury porosimetry 59 is a method of measuring pore size and pore size
distribution by injecting mercury into pores. Due to the high pressure involved (up to 400
MPa) and the limiting size of pores for penetration by pressurized mercury (~2 nm), this
method is more suitable to characterize mesoporous or macroporous materials. Safety
requirement and sample disposal are major concerns for this technique.
In small angle X-ray scattering measurement, X-rays from a source are focused
into a fine beam and directed on to the sample. A small fraction of the beam is scattered
and detected. The intensity and the way the intensity varies with the scattering angle are
determined by the variations of electron density within a sample, which originate from
the structure of the sample. The electron density is high in the solid wall area and falls to
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