NMR imaging in materials science

The image illustrates two important features of materials imaging. First, novel contrast features can be exploited to locate previously unknown material heterogeneities. 

7 [Blii2] Stress image of a stretched polydimethyl-siloxane band with a cut (right). 

A heterogeneous stress distribution is observed which results from the cut as well as from filler inhomogeneities. The grey scale indicates local stress in the range from 0 to 2.4 MPa. 

---

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. 

Rombach K, Laukemper-Ostendorf and Blumler P 1998 Applications of NMR flow imaging in materials science Spatially Resolved Magnetic Resonance, Proc. 4th Int. Conf. on Magnetic Resonance Microscopy and Macroscopy ed P Blumler, B Blumich, R E Botto and E Fukushima (Weinheim Wiley-VCH) pp 517-29... 

In materials science applications of NMR imaging the geometry of the object can often be chosen at liberty. For example, cylindrical samples can be used for studies of porosity by diffusion and flow in rocks and catalyst pellets [Maj2], and investigations of deterioration in polymers and elastomers. Furthermore, many biological samples show radial or close... 

Applications of NMR imaging outside the medical field have been published in a variety of books and journals [8-13, 21, 86, 108-115]. A rather important subject for applications of NMR imaging is polymer science, as polymers are rich in protons, the most sensitive, stable NMR nucleus, and many polymer materials are often soft, so that the homonuclear dipole-dipole interaetion among protons is partially averaged by molecular motion. Thus, polymers are far more suitable to NMR imaging than for instance ceramic materials. 

Altobelli, S. A., Caprihan, C., Fukushima, E., and Majors, P.D., NMR Imaging Studies of Velocity and Concentration Distributions in Flows, in Magnetic Resonance Microscopy. Methods and Applications in Materials Science. Agriculture and Biomedicine (Bluemich, B., and Kuhn, W., eds.), 1992. 

A new design of a hand-size elliptical permanent magnet suitable for unilateral NMR spectroscopy and one-dimensional (ID) MRI was presented with possible applications in materials science, biology, environmental science and medicine. The magnet configuration is optimized to get a penetration depth of up to 1 cm and ID imaging capabilities. 

Localized NMR spectroscopy, which is often called as MRS in comparison with MRI, is not so familiar technique in food science, because a specific pulse sequence such as ISIS and a facility which can precisely follow the pulse sequence without any contamination from other position is needed for localization of position. The localized NMR is usually used together with NMR imaging. The study of solid/liquid ratios, fat structure and polymorphism and the kinetics of fat crystallization was reviewed [24], The potential of applications in food process development and control was offered. The localized spectra of sausages in areas of 0.3 mm X 0.05 mm (thickness of sample =1.5 mm) were obtained by the spin echo 2DFT method [113], in which the difference in the tissue structure was discussed with relation to the process and original materials. McCarthy et al. determined mobility of water in foams by using a localized spectroscopy [114]. T2 relaxation time varies in the foam as function of diameter and its variation was analyzed by the classic 2-state fast exchange model. 

Solid-state NMR spectroscopy has been demonstrated as a well established technique for characterization of zeolites and other porous materials with respect to structure elucidation, pore architecture, catalytic behaviour and mobility properties. The latest progress in the development of NMR techniques, both with respect to software and hardware improvements, has contributed to the present state of the art for NMR within the field of characterization of zeolitic materials. Furthermore, the introduction of NMR imaging (110), two-dimensional quintuple-quantum NMR spectroscopy (111) and transfer of populations in double resonance (TRAPDOR) NMR (112,113) will extent the horizons of zeolite characterization science. As a final example, the Al => Si TEDOR experiment directly proves, for the first time, that silicon substitutes for phosphorous atoms in the framework of SAPO-37 (114). The Al... 

The noninvasive nature of NMR spectroscopy combined with the chemical specificity of the NMR method provides direct access to the distribution of various chemical constituents for the histochemistry of plant materials in situ NMR spectroscopy can be used to identify the major constituents, and chemical-.shift imaging can be used to spatially localize them. The latter can be applied to localize aromatics, carbohydrates, as well as water and fat or oil in plant samples. The suitability of many fresh fruits and living plants to be studied by NMR imaging results in a variety of applications in agriculture and food science [Mcc I, Mcc2]. 

Many methods for improvements of the spatial resolution in NMR imaging of solid materials have been proposed with different impact on applications in polymer science [8, 9, 11-13, 21]. For the great variety of techniques only those are reviewed in Sections 5.1.3 and 5.1.4 below, which are being applied successfully to problems in polymer science. Depending on the dominating features, the techniques can be classified into frequency and phase encoding approaches. 

---