1H nuclear magnetic resonance spectra and images have been acquired during polymerization of a mixture of soluble reactive methacrylamide (monomer) and N,N‘-methylenebisacrylamide (cross-linking molecule). The mixture was polymerized by adding ammonium persulfate (initiator) and tetramethylethylenediamine (accelerator) to form long-chain, cross-linked polymers. Study of the time-varying spin−lattice relaxation times (T 1) during the polymerization was conducted at 25 and 35 °C and the variation of spectra and T 1 with respect to the extent of polymerization was determined. To verify homogeneous polymerization, multidimensional 1H NMR imaging was utilized for in-situ monitoring of the process. The intensities from the images are modeled and the correspondence shows a direct extraction of T 1 data from the images.

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Electron beam‐induced polymerization of trimethylolpropane triacrylate (TMPTA) and its methacrylate analog (TMPTMA) was studied using nuclear magnetic resonance (NMR) relaxation time measurements. Free induction decays (FID) of partially polymerized samples consist of a short Gaussian component and a longer component comprised of a distribution of simple exponentials. The relative intensity of the Gaussian component increases with radiation dose. T1 and T1ρ values were measured as a function of temperature and radiation dose. The relaxation is due primarily to methyl group reorientation at low temperatures, ethyl group reorientation at intermediate temperatures, and whole‐molecule reorientation at high temperatures. In both compounds, the T1 and T1ρ values at the high temperature minima increase with increasing dose, and the minima values can be used to estimate the degree of polymerization. The temperature at which the T1ρ minimum occurs increases with dose, suggesting an increase in the glass transition temperature, Tg, with polymerization. The polymerization appears to have very little effect on the low temperature CH3 reorientation in TMPTA. In TMPTMA the polymerization appears to reduce the mobility of the methacrylate methyl groups.

Ceramic matrix composites are being developed for numerous high temperature applications, including rotors ad combustors for advanced turbine engines, heat exchanger and hot-gas filters for coal gasification plants. Among the materials of interest are silicon-carbide-fiber-reinforced-silicon-carbide (SiC@SiC), silicon-carbide-fiber-reinforced-silicon-nitride (SiC@Si3N4), rduminum-oxide-reinforced-ahtmina (A1203(f)/A1203), etC.In the manufacturing of these ceramic composites, the conditions of the fiber/matrix interface are critical to the mechanical and thermal behavior of the component. Defects such as dehtrninations and non-uniform porosity can directly effect the performance. A nondestructive evaluation (NDE) method, developed at Argonne National Laboratory has proved beneficial in analyzing as-processed conditions and defect detection created during manufacturing. This NDE method uses infrmd thermal imaging for fill-field quantitative measurement of the distribution of thermal diffusivity in large components. Intensity transform algorithms have been used for contrast enhancement of the output image. Nonuniformity correction and automatic gain control are used to dynamically optimize video contrast and brightness, providing additional resolution in the acquired images. Digital filtering, interpolation, and least-squares-estimation techniques have been incorporated for noise reduction and &ta acquisition. The Argonne NDE system has been utilized to determine thermal shock damage, density variations, and variations in fiber coating in a full array of test specimens.

The method of gelcasting requires making a mixture of a slurry of ceramic powder in a solution of organic monomers and casting it in a mold. Gelcasting is different from injection molding in that it separates mold filling from setting during conversion of the ceramic slurry to a formed green part. In this work, nuclear magnetic resonance (NMR) spectroscopy and imaging has been used for in-situ monitoring of the gelation process and gelcasting of alumina. 1H N M R spectra and images are obtained during polymerization of a mixture of soluble reactive acrylamide monomers. Polymerization was initiated by adding an initiator and an accelerator to form long-chain, cross-linked polymers. Multidimensional NMR imaging was utilized for in-situ monitoring of the process and for verification of homogeneous polymerization. Comparison of the modeled intensities with acquired images shows a direct extraction of T1 data from the images.