Microstructure microtomography

A first example of application of microtomography is taken from life sciences. Here X-ray microscopy and microtomography allows to reconstruct the internal three-dimensional microstructure without any preparation and sometimes even of living objects. Fig. la shows an X-ray transmission microscopical image of bone (femoral head). Several reconstructed cross-sections are shown in Fig.lb. Fig.lc shows the three-dimensional reconstruction of this bone. 

X-ray microtomography is a new development of great promise for reconstructing, displaying, and analyzing three-dimensional microstructures. Resolution of around 1 pm has been demonstrated with currently available synchrotron sources of x-rays, x-ray detectors, algorithms, and large-scale computers. The potential for microstructural research in composites, porous materials, and suspensions at this and finer scales appears to be tremendous. 

Successful development of such systems will lead to foamed materials having useful stress-absorbing characteristics in addition to controlled physics properties. Although our work in this area is currently in a very early stage, prototype materials have been successfully synthesized and assessed structurally using three-dimensional (3D) X-ray microtomography. The technique offers a unique insight into the internal microstructure of cellular materials (see Fig. 3). The diameter of the mainly open cell pores varies from approximately 100 to 250 pm (the resolution of the instrument is 5 pm), with cell walls of variable thickness. 

The microstructure of bread and other microporous foods can be conveniently studied by applying synchrotron radiation X-ray microtomography (X-MT) (Falcone et al., 2004a Maire et al., 2003) to centimeter- or millimeter-sized samples (Lim and Barigou, 2004). X-MT application only requires the presence of areas of morphological or mass density heterogeneity in the sample materials. The use of this technique for food microstructure detection is of recent date. It was traditionally used for the analysis of bone quality (Peyrin et al., 1998, 2000 Ritman et al., 2002). 

Trater, A. M., Alavi, S., and Rizvi, S. S. H. (2005). Use of non-invasive x-ray microtomography for characterizing microstructure of extruded biopolymer foams. Food Research International, 38(6), 709-719. 

X-ray microtomography reconstruction of the carbon paper GDL microstructure. (Source Ref. 23.)... 

Leonard, A., Blacher, S., Nimmol, C., Devahastin, S., 2008. Effect of far-infrared radiation assisted drying on microstructure of banana slices An illustrative use of X-ray microtomography in microstructural evaluation of a food product. /. Food Eng. 85(1) 154-162. 

Important features in microscopy are in situ methods, quantitative interpretation of the object microstructure and the definition of 3D information. Of the techniques available to the microscopist today, only transmission X-ray microscopy gives nondestructive high-resolution information from the internal structure of an object under natural conditions. By combining the X-ray transmission technique with tomographical reconstruction 3D information about the internal microstructure can be derived [729], X-ray microtomography (/rCT) requires an X-ray microscanner (8 nm spot size), precision object manipulator. X-ray CCD camera, and microtomographical data processing [730]. 

X-ray microtomography with sub-micrometer resolution has been used to investigate the evolution of the microstructure of semi-crystalline polymers during tensile deformation [41]. 

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