Electron microscopy; proceedings of the Electron microscopy; proceedings of the Stockholm Conference, September, 1956 electronmicrosco00euro Year: 1957 Selective Oxidation of y:-Brass 323 Fig. 7. Electron ditVraction pattern ofa-brass withZnO. Fig. 8. Two relative orientations between a-brass and ZnO. Fig. 9. Corresponding electron micrograph of Fig. 7. Fig. 10. Electron micrograph for fmal stage of oxydalion for a-brass. Fig. 11. Secondary diffraction effect for Cu.,0. and the small black points are distributed uniformly on the surface of a-brass. Furthermore, when a-brass is heated in so
Electron microscopy; proceedings of the Electron microscopy; proceedings of the Stockholm Conference, September, 1956 electronmicrosco00euro Year: 1957 Selective Oxidation of y:-Brass 323 Fig. 7. Electron ditVraction pattern ofa-brass withZnO. Fig. 8. Two relative orientations between a-brass and ZnO. Fig. 9. Corresponding electron micrograph of Fig. 7. Fig. 10. Electron micrograph for fmal stage of oxydalion for a-brass. Fig. 11. Secondary diffraction effect for Cu.,0. and the small black points are distributed uniformly on the surface of a-brass. Furthermore, when a-brass is heated in some bad vacuum, one may see the agglomerations with the definite external shape as shown in fig. 6, which can be considered as CuaO. Formation of ZnO.—When heating the a-brass over 450 C in the electron microscope, ZnO appears in the state of single crystals. Fig. 7 shows the electron diffraction image of ZnO which was obtained by heating a-brass at 450 C during 30 min. The larger spots correspond to a-brass and the other spots are due to ZnO. The arrangement shows that ZnO develops as a hexagonal prism which has the situation of perpendicularity to the cubic face of a-brass. The diagonal of (0001) of ZnO is parallel to the direction of [100] of a-brass. Fig. 8 shows schematically the two relative orienta- tions between ZnO and a-brass, that is, (0001 )z„o// (00 1 ),.brass and [ 1! 20]znO, \ [ 1 TOJa-brass (4) and (0001)zno//(00I),.b,.assand [1 I 20]z„o//[l lOUrass- (5) The diffraction spots around the direct electron beam in hg. 7 show the above two orientations. Discussion.—(1) Relative orientations between t/ie oxides and The appearance of the orienta- tion (I) can be understood easily by the fact that oxygen atoms enter in the lattice of a-brass to form CU2O. The orientations (2) and (3) seem to devel- op after the formation of the orientation (I): copper atoms traverse into the layer of oxide already pro- duced and at the surface of the oxide layer copper
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