G. Brauer et al. / Applied Surface Science 252(2006)3342-335 3345 (d) 0 1.0 Fig. 2. AFM images of the SiC/SiC composite a)10 um x 10 um image representing the overall sample morphology. The grey scale range is 500 nm. (b)2.5 um x 2.5 um AFM ima ifferent sample position. The grey scale range is 200 nm. The 3D crystallites are eithe arranged along the furrows on a fibre ply, or are distributed on the surface. (c)I um x I um AFM image showing a small fraction of a fibre ply in the left part of the image. The arrow a larger ridge with a step. The grey scale range is 50 nm. ( d)Section analysis along the line indicated in(c) first, small three-dimensional (3D) crystallites and crystallites are rather uniform. second, unidirectional oriented elongated structures sized 30+ 5 nm in diameter can I nd in irregular The latter can clearly be addressed to the Sic fibres of arrays over a few percent of arger the composite sample. Whereas individual isolated crystallites with 75+ 15 nm diameter, occupyin fibres are rarely observed, a large fraction of them about 15%o of the area of the surface, are frequently occurs in densely packed two-dimensional(2D) observed along the furrows between the fibres arrays. It seems that such 2D-ply fibres are embedded (Fig. 2b). Due to the overall roughness of the sample in the matrix of 3D crystallites. One ply usually it was impossible to reveal the 3D shape(facets)of the extends over an area of about 5 um x 5 um(Fig 2a) crystallites with frayed edges. From the line section presented In addition to the crystallites and fibre plies Fig 2d, we can assume that the fibres have a circular larger ridges are occasionally observed-indicated cross-section. Their diameters range between 40 and by arrows in Fig. 2c and d. These ridges have a 55 nn ateral size of about 250 nm and are on average The 3D crystallites have an average diameter of 50 nm high. The line section in Fig. 2d reveals a about 50 nm ranging from 25 to almost 100 nm. This second step on top of the larger ridge, which is about finding is in excellent agreement with the results from 12 nm high. The nature of these features is not yet Xrd discussed above. Within certain areas the clearfirst, small three-dimensional (3D) crystallites and second, unidirectional oriented elongated structures. The latter can clearly be addressed to the SiC fibres of the composite sample. Whereas individual isolated fibres are rarely observed, a large fraction of them occurs in densely packed two-dimensional (2D) arrays. It seems that such 2D-ply fibres are embedded in the matrix of 3D crystallites. One ply usually extends over an area of about 5 mm
5 mm (Fig. 2a) with frayed edges. From the line section presented in Fig. 2d, we can assume that the fibres have a circular cross-section. Their diameters range between 40 and 55 nm. The 3D crystallites have an average diameter of about 50 nm ranging from 25 to almost 100 nm. This finding is in excellent agreement with the results from XRD discussed above. Within certain areas the crystallites are rather uniform. Small crystallites sized 30 5 nm in diameter can be found in irregular arrays over a few percent of the surface. Larger crystallites with 75 15 nm diameter, occupying about 15% of the area of the surface, are frequently observed along the furrows between the fibres (Fig. 2b). Due to the overall roughness of the sample it was impossible to reveal the 3D shape (facets) of the crystallites. In addition to the crystallites and fibre plies, larger ridges are occasionally observed—indicated by arrows in Fig. 2c and d. These ridges have a lateral size of about 250 nm and are on average 50 nm high. The line section in Fig. 2d reveals a second step on top of the larger ridge, which is about 12 nm high. The nature of these features is not yet clear. G. Brauer et al. / Applied Surface Science 252 (2006) 3342–3351 3345 Fig. 2. AFM images of the SiC/SiC composite sample. (a) 10 mm
10 mm image representing the overall sample morphology. The grey scale range is 500 nm. (b) 2.5 mm
2.5 mm AFM image of a different sample position. The grey scale range is 200 nm. The 3D crystallites are either arranged along the furrows on a fibre ply, or are irregularly distributed on the surface. (c) 1 mm
1 mm AFM image showing a small fraction of a fibre ply in the left part of the image. The arrow indicates a larger ridge with a step. The grey scale range is 50 nm. (d) Section analysis along the line indicated in (c).