Quantitative Measurement of the Pore Structure
This is a special area of research in which there are numerous techniques, equipment and software that allow determination of the pore structure with respect to the number of pores, pore size and shape distributions (Kocer et al. 2007; Hicsasmaz et al. 2003), number of cell faces, cell wall thickness, pore interconnectivity and polydispersity index (Trater et al. 2005). Pore structure analysis is a high technology field in which microscopic techniques such as light microscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) besides numerous image analysis techniques primarily used to visualize the human body for purposes of medical diagnosis are well-adapted. X-ray microtomography (Frisullo et al. 2012; Trater et al. 2005) is one such technique in which 2-D sections can be imaged non-destructively, and then a qualitative 3-D reconstruction can be performed. 2-D micro-tomography images and related software allow measurement of cell wall thicknesses with accuracy. Magnetic resonance imaging (MRI) (Wagner et al. 2008; Ishida et al. 2001), SEM and environmental scanning microscopy (ESEM) (Stokes and Donald 2000) also provide data on the pore structure, SEM being one of the most widely used methods. Ultrasound (Lagrain et al. 2006) is used in microstructure measurements. Mercury porosimetry (Hicsasmaz and Clayton 1992) and liquid extrusion porosimetry (Datta et al. 2007) are quantitative methods which do not use imaging techniques, but that use the capillary penetration technique.