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Unique mechanical properties of nanostructured transparent MgAl2O4 ceramics.

Zhang J, Lu T, Chang X, Wei N, Qi J - Nanoscale Res Lett (2013)

Bottom Line: These tests were carried out on samples at different applied loads ranging from 300 to 9,000 μN.The elastic recovery for nanostructured transparent MgAl2O4 ceramics at different applied loads was derived from the force-depth data.Finally, the experimentally measured hardness and Young's modulus, as derived from the load-displacement data, are as high as 31.7 and 314 GPa, respectively.

View Article: PubMed Central - HTML - PubMed

Affiliation: School of Physics and Optoelectronic Engineering, Ludong University, Yantai 264025, People's Republic of China. zhjie126@126.com.

ABSTRACT
Nanoindentation tests were performed on nanostructured transparent magnesium aluminate (MgAl2O4) ceramics to determine their mechanical properties. These tests were carried out on samples at different applied loads ranging from 300 to 9,000 μN. The elastic recovery for nanostructured transparent MgAl2O4 ceramics at different applied loads was derived from the force-depth data. The results reveal a remarkable enhancement in plastic deformation as the applied load increases from 300 to 9,000 μN. After the nanoindetation tests, scanning probe microscope images show no cracking in nanostructured transparent MgAl2O4 ceramics, which confirms the absence of any cracks and fractures around the indentation. Interestingly, the flow of the material along the edges of indent impressions is clearly presented, which is attributed to the dislocation introduced. High-resolution transmission electron microscopy observation indicates the presence of dislocations along the grain boundary, suggesting that the generation and interaction of dislocations play an important role in the plastic deformation of nanostructured transparent ceramics. Finally, the experimentally measured hardness and Young's modulus, as derived from the load-displacement data, are as high as 31.7 and 314 GPa, respectively.

No MeSH data available.


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Hardness (A) and Young’s modulus (B) as a function of applied load. Inset shows TEM image of the sample.
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Figure 4: Hardness (A) and Young’s modulus (B) as a function of applied load. Inset shows TEM image of the sample.

Mentions: 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.


Unique mechanical properties of nanostructured transparent MgAl2O4 ceramics.

Zhang J, Lu T, Chang X, Wei N, Qi J - Nanoscale Res Lett (2013)

Hardness (A) and Young’s modulus (B) as a function of applied load. Inset shows TEM image of the sample.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3672023&req=5

Figure 4: Hardness (A) and Young’s modulus (B) as a function of applied load. Inset shows TEM image of the sample.
Mentions: 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.

Bottom Line: These tests were carried out on samples at different applied loads ranging from 300 to 9,000 μN.The elastic recovery for nanostructured transparent MgAl2O4 ceramics at different applied loads was derived from the force-depth data.Finally, the experimentally measured hardness and Young's modulus, as derived from the load-displacement data, are as high as 31.7 and 314 GPa, respectively.

View Article: PubMed Central - HTML - PubMed

Affiliation: School of Physics and Optoelectronic Engineering, Ludong University, Yantai 264025, People's Republic of China. zhjie126@126.com.

ABSTRACT
Nanoindentation tests were performed on nanostructured transparent magnesium aluminate (MgAl2O4) ceramics to determine their mechanical properties. These tests were carried out on samples at different applied loads ranging from 300 to 9,000 μN. The elastic recovery for nanostructured transparent MgAl2O4 ceramics at different applied loads was derived from the force-depth data. The results reveal a remarkable enhancement in plastic deformation as the applied load increases from 300 to 9,000 μN. After the nanoindetation tests, scanning probe microscope images show no cracking in nanostructured transparent MgAl2O4 ceramics, which confirms the absence of any cracks and fractures around the indentation. Interestingly, the flow of the material along the edges of indent impressions is clearly presented, which is attributed to the dislocation introduced. High-resolution transmission electron microscopy observation indicates the presence of dislocations along the grain boundary, suggesting that the generation and interaction of dislocations play an important role in the plastic deformation of nanostructured transparent ceramics. Finally, the experimentally measured hardness and Young's modulus, as derived from the load-displacement data, are as high as 31.7 and 314 GPa, respectively.

No MeSH data available.


Related in: MedlinePlus