J. Rebelo Kornmeier et al. Materials Characterization 58(2007)922-927 filled with solder, thus providing the desired homogeneity figure the fibre orientation and integrity, matrix homoge of the connection. As an advantage with respect to neity, dimensions and distributions of micro pores can measurements with X-rays, the high density of the Niob clearly be seen. Using image analysis it is also possible to flange is not a problem for neutron radiation obtain quantitative characterisation of the C/SiC material 2. 4. Synchrotron tomography of a nozzle sample 2.5. Neutron residual stress Characterisation of the composite material on the fibre The non-destructive analysis of phase-specific residual scale is not possible by neutron tomography as the fibre stresses is only possible by means of diffraction methods diameter is only 6 to 7 um. However, synchrotron While conventional X-ray diffraction stress analysis only tomography is able to reveal three dimensionally the yields information from a small surface layer, between 5- orientation of carbon fibres and their integrity [7]. Such a 100 um, the large penetration depth of neutrons offers the characterisation tool can identify if the silicon has reacted que possibility for non-destructive residual stre with the fibre. In the Sic matrix unreacted silicon can be analysis within bulk samples and components. detected and the dimensions and distributions of pores in Residual stress measurements in the sic matrix of the any desired location or orientation can be quantified. C/SiC nozzles were carried out at the neutron diffraction Respective exemplary measurements were carried out at facilities of Hahn Meitner Institut(HMi) Ber the X-ray microtomographic device at the Materials thermal neutrons. The measurements were performed at Science Beamline MS of the Swiss Light Source(SLS) the throat region of a temperature tested nozzle in the three using an energy of 15 ke V and a pixel resolution of 1. 4 um principal directions, axial, tangential and radial, as ( the data being binned). Using a 2048 x 2048 pixel CCD- indicated in Fig. 5(b). During the prior temperature test, camera [7] this creates a 1. 4 mm field of view. Therefore the nozzle had been subjected to a temperature of 1900C the high resolution requires samples smaller than 1. 4 mm for two and an half hours, see Fig. 5(a). The residual stress to be measured. In our case samples of I mm cross measurements were carried out with the centre of the section were examined, see Fig. 4. Five hundred two- gauge volume at 3 different points in depth, the first one dimensional projections of the sample in equidistant being located 2 mm underneath the surface. The othertwo ngular intervals from 0o to 180 were acquired. The points were chosen in increments of2 mm, at 4 and 6 mm exposure time was 5 s for each projection resulting in a depth, respectively. The gauge volume element was total scan time of approximately 40 min. Flat and dark defined with a size of 4 x 4x4 mm by slits in the primary field corrected data have been reconstructed with a and reflected beam. In order to maintain an identical gauge standard filtered-backprojection algorithm [5]. The result- volume at different sample orientations, the diffraction ng three-dimensional image is shown in Fig 4. In this angle 20 had to be near 90o. Therefore, for a wavelength Point Imn : Fig. 6. Residual stress values for different positions in depth at the throat of the temperature tested nozzle.filled with solder, thus providing the desired homogeneity of the connection. As an advantage with respect to measurements with X-rays, the high density of the Niob flange is not a problem for neutron radiation. 2.4. Synchrotron tomography of a nozzle sample Characterisation of the composite material on the fibre scale is not possible by neutron tomography as the fibre diameter is only 6 to 7 μm. However, synchrotron tomography is able to reveal three dimensionally the orientation of carbon fibres and their integrity [7]. Such a characterisation tool can identify if the silicon has reacted with the fibre. In the SiC matrix unreacted silicon can be detected and the dimensions and distributions of pores in any desired location or orientation can be quantified. Respective exemplary measurements were carried out at the X-ray microtomographic device at the Materials Science Beamline MS of the Swiss Light Source (SLS) using an energy of 15 keVand a pixel resolution of 1.4 μm (the data being binned). Using a 2048× 2048 pixel CCD￾camera [7] this creates a 1.4 mm field of view. Therefore the high resolution requires samples smaller than 1.4 mm to be measured. In our case samples of 1 mm2 cross section were examined, see Fig. 4. Five hundred two￾dimensional projections of the sample in equidistant angular intervals from 0° to 180° were acquired. The exposure time was 5 s for each projection resulting in a total scan time of approximately 40 min. Flat and dark field corrected data have been reconstructed with a standard filtered-backprojection algorithm [5]. The result￾ing three-dimensional image is shown in Fig. 4. In this figure the fibre orientation and integrity, matrix homoge￾neity, dimensions and distributions of micro pores can clearly be seen. Using image analysis it is also possible to obtain quantitative characterisation of the C/SiC material. 2.5. Neutron residual stress The non-destructive analysis of phase-specific residual stresses is only possible by means of diffraction methods. While conventional X-ray diffraction stress analysis only yields information from a small surface layer, between 5– 100 μm, the large penetration depth of neutrons offers the unique possibility for non-destructive residual stress analysis within bulk samples and components. Residual stress measurements in the SiC matrix of the C/SiC nozzles were carried out at the neutron diffraction facilities of Hahn Meitner Institut (HMI) Berlin using thermal neutrons. The measurements were performed at the throat region of a temperature tested nozzle in the three principal directions, axial, tangential and radial, as indicated in Fig. 5(b). During the prior temperature test, the nozzle had been subjected to a temperature of 1900 °C for two and an half hours, see Fig. 5(a). The residual stress measurements were carried out with the centre of the gauge volume at 3 different points in depth, the first one being located 2 mm underneath the surface. The other two points were chosen in increments of 2 mm, at 4 and 6 mm depth, respectively. The gauge volume element was defined with a size of 4×4×4 mm3 by slits in the primary and reflected beam. In order to maintain an identical gauge volume at different sample orientations, the diffraction angle 2θ had to be near 90°. Therefore, for a wavelength Fig. 6. Residual stress values for different positions in depth at the throat of the temperature tested nozzle. 926 J. Rebelo Kornmeier et al. / Materials Characterization 58 (2007) 922–927