Materials science imaging

As a special development in recent years, SEMs have been designed which no longer necessitate high vacuum (enviromnental SEM, ESEM variable pressure SEM, VPSEM). This development is important for the imaging of samples with a residual vapour pressure, such as aqueous biological or medical samples, but also samples in materials science (wet rock) or organic chemistry (polymers). 

The construction of an aberration-corrected TEM proved to be teclmically more demanding the point resolution of a conventional TEM today is of the order of 1-2 A. Therefore, the aim of a corrected TEM must be to increase the resolution beyond the 1 A barrier. This unplies a great number of additional stability problems, which can only be solved by the most modem technologies. The first corrected TEM prototype was presented by Flaider and coworkers [M]- Eigure BE 17.9 shows the unprovement in image quality and interpretability gained from the correction of the spherical aberration in the case of a materials science sample. 

Figure 4.12 Spherulites of poly( 1-propylene oxide) observed through crossed Polaroid filters by optical microscopy. See text for significance of Maltese cross and banding in these images. [From J. H. MaGill, Treatise on Materials Science and Technology, Vol. lOA, J. M. Schultz (Ed.), Academic, New York, 1977, with permission.]...

The first detailed book to describe the practice and theory of stereology was assembled by two Americans, DeHoff and Rhines (1968) both these men were famous practitioners in their day. There has been a steady stream of books since then a fine, concise and very clear overview is that by Exner (1996). In the last few years, a specialised form of microstructural analysis, entirely dependent on computerised image analysis, has emerged - fractal analysis, a form of measurement of roughness in two or three dimensions. Most of the voluminous literature of fractals, initiated by a mathematician, Benoit Mandelbrot at IBM, is irrelevant to materials science, but there is a sub-parepisteme of fractal analysis which relates the fractal dimension to fracture toughness one example of this has been analysed, together with an explanation of the meaning of fractal dimension , by Cahn (1989). 

The Stereoscan instruments were a triumphant success and their descendants, mostly made in Britain, France, Japan and the United States, have been sold in thousands over the years. They are indispensable components of modern materials science laboratories. Not only that, but they have uses which were not dreamt of when Oatley developed his first instruments thus, they are used today to image integrated microcircuits and to search for minute defects in them. 

The scanning acoustic microscope is a powerful new tool for the study of the physical properties of materials and has been successfully used for imaging interior structures and for nondestructive evaluation in materials science and biology. 

Materials science and engineering is a vital field of endeavor for industry and defense and also with regard to its sheer intellectual content. This field is no longer a disparate collection of disciplines. Its unity and coherence can be seen in a tetrahedron this image captures the essence of the field. The four aspects to any materials-related activity are as follows ... 

The density weighted images and their absolute quantification demonstrated through concrete drying experiments are very powerful tools for material science. 

The measurement applications of density weighted drying profiles, water ingress, water phase transitions, crack detection, chlorine, sodium and lithium imaging applied to cement-based materials can be easily translated to other porous media. Density weighted MRI will no doubt prove to be a powerful tool in material science research. 

K. Rombach, S. Laukemper-Ostendorf, P. Bluemler 1998, (Applications of NMR flow imaging in materials science), in Spatially Resolved Magnetic Resonance, eds. P. Bluemler, B. Bluemich, R. Botto, E. Fukushima, Wiley-VCH, New York. 

E.W. Muller, in Modem Diffraction and Imaging Techniques in Materials Science, S. Amelinckx, R. Gevers, G. Remault and J. van Landuyt (Eds.), North Holland, Amsterdam, 1970. 

Thiel, B.L. (2004). Imaging and analysis in materials science by low vacuum scanning electron microscopy. International Materials Reviews 49 109-122. 

Due to its unique ability to directly image the local structure of a thin object with atomic resolution, HRTEM is an extremely powerful tool for materials research. Metals, ceramics, and semiconductors are some examples of prominent materials of interest. HRTEM imaging used to be a high-end research tool mostly used in academia, but has now become standard for a wide variety of applications from materials science research to defect analysis in industrial semiconductor fabrication lines. 

A.R.LANG, in Modem diffraction and imaging techniques in materials science, eds. S. AMELINCKX, R.GEVERS J.VAN LANDUYT, Vol. 2 (North-Holland, Amsterdam, 1970) p. 623. ... 

Studies on fundamental interactions between surfaces extend across physics, chemistry, materials science, and a variety of other disciplines. With a force sensitivity on the order of a few pico-Newtons, AFMs are excellent tools for probing these fundamental force interactions. Force measurements in water revealed the benefits of AFM imaging in this environment due to the lower tip-sample forces. Some of the most interesting force measurements have also been performed with samples under liquids where the environment can be quickly changed to adjust the concentration of various chemical components. In liquids, electrostatic forces between dissolved ions and other charged groups play an important role in determining the forces sensed by an AFM cantilever. 

Fig. 3 TEM and (insets) EFT images of mesoporous MSU-Ge-2 obtained by heat-treating the NRj -exchanged material. The images shows (a) a periodic hexagonal array along the [001] direction and (b) a periodic array of parallel pore channels along the [110] direction. Reproduced with permission from [43]. Copyright 2007 American Association for the Advancement of Science...

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