Moreover, polycrystalline hydroxyapatite is reported to exhibit plasticity at higher temperature [19, 20], but no plasticity has been reported at room temperature for nanostructured transparent ceramics. Furthermore, for ceramic materials, the

plasticity is limited at low loads, and the influence of dislocation can be important [21, 22]. GW-572016 supplier Thus, the faceted pile-up region suggests that dislocations generated during the indentation are attributed to the residual strain of nanostructured transparent ceramics. Figure 2 SPM image and corresponding cross-sectional profile. SPM image of an indented area (A) and the corresponding cross-sectional profile (B) along the bluish grey line in (A). In order to further investigate the mechanical properties of nanostructured transparent ceramics, we used HRTEM to examine the microstructures of the sample indented at 9,000 μN. The HRTEM image is shown in Figure 3.

The inset in this figure is a selected area electron diffraction pattern of the indented sample, indicative of a magnesia-alumina spinel crystal structure. The left part of the HRTEM image reveals well-ordered atomic structures. However, there are dislocations close to the triangular grain boundary, suggesting that the generation, movement, and interaction of dislocations check details during the indentation play an important role in the plastic deformation as well as the resulting mechanical properties. Figure 3 HRTEM image of the nanostructured transparent MgAl ADP ribosylation factor 2 O 4 ceramic. Inset shows the selected area

diffraction pattern. Hardness and Young’s modulus of the nanostructured transparent MgAl2O4 ceramics are shown in Figure 4 as a function of the applied load. Both hardness and Young’s modulus decrease with increasing loads. Furthermore, it also indicates that there appears to be a larger decrease in the hardness than in the Young’s modulus with increasing load. These phenomena have been attributed to the well-known indentation size effect. Gong et al. [14] studied an alumina ceramic by nanoindentation testing and found that more cracks were generated at higher loads. However, the absence of cracks in the vicinity of the indented zone (Figure 2) suggests that it should not be reasonable to explain the load-dependent mechanical properties of our nanostructured transparent ceramics only by the indentation size effect. Dislocation activity, as evidenced in Figure 3, compared to HRTEM images of the sample at atmospheric pressure [11] should be considered as an important factor that can influence the mechanical properties of nanostructured transparent ceramics. A more detailed study is clearly needed to understand how the dislocation activity influences the mechanical properties. Figure 4 Hardness (A) and Young’s modulus (B) as a function of applied load. Inset shows TEM image of the sample.