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The aim of this study is to characterize the microstructure and high temperature induced structural changes within fiber reinforced silicon carbide (SiC/SiC) composites by means of non-destructive techniques. In order to understand their properties, the characterization of the microstructure of SiC/SiC composites is the crucial issue. Porosity within composites is unavoidable with currently available manufacturing processes, and reduces significantly the life time and performance of the composites under harsh environments. Moreover, the internal pores, created in the manufacturing process cause the degradation most of the outstanding properties such as thermal conductivity, mechanical properties at high temperature, and radiation stability. Cold neutron tomography and diffusion structural diagnostic techniques were applied in the investigation of the microstructure of SiC/SiC composites to gain complementary information. One of the main obstacles to using these composites in fusion technology and other applications are a change of the porous structure and a swelling at high temperatures and in a severe radiation environment. Cold neutron tomography enables visualization of the microstructure of the composite and consequently the pore distributions within the SiC/SiC composite were observed with a suitable resolution. The diffusion structural diagnostic technique was used to characterize the thermal behavior of SiC/SiC composites on heating up to 1300 °C. [ABSTRACT FROM AUTHOR]

Knowing the distribution of a magnetic field in bulk materials is important for understanding basic phenomena and developing functional magnetic materials. Microscopic imaging techniques employing X-rays, light, electrons, or scanning probe methods have been used to quantify magnetic fields within planar thin magnetic films in 2D or magnetic vector fields within comparable thin volumes in 3D. Some years ago, neutron imaging has been demonstrated to be a unique tool to detect magnetic fields and magnetic domain structures within bulk materials. Here, we show how arbitrary magnetic vector fields within bulk materials can be visualized and quantified in 3D using a set of nine spin-polarized neutron imaging measurements and a novel tensorial multiplicative algebraic reconstruction technique (TMART). We first verify the method by measuring the known magnetic field of an electric coil and then investigate the unknown trapped magnetic flux within the type-I superconductor lead. Mapping the distribution of magnetic fields inside bulk materials is challenging but crucial to understand and develop functional magnetic materials. Here the authors demonstrate the capability to visualize 3D vector magnetic fields inside materials using spin-polarized neutron tomography and tensorial reconstruction techniques. [ABSTRACT FROM AUTHOR]

The process of neutron radiography image formation can be described in terms of a point-spread function (PSF) superposition for a given space discretization. In this way all distortions in the radiography picture obtained at different experimental conditions can be described as alterations in the corresponding PSF. The scattered neutrons are one of the main sources of such distortions in radiography experiments. Monte Carlo simulations (MCNP-4b[sup (c)] code) were performed for calculations of the PSF for different materials, thicknesses and distances between sample and detector. A set of radiography experiments was performed at the thermal neutron radiography facility NEUTRA at PSI to confirm the PSF superposition procedure. The good agreement between the superposition method and the experimental data allows to use the Monte Carlo simulations as a base for corrections in radiography images. [ABSTRACT FROM AUTHOR]