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Structure-dependent mechanical properties of ultrathin zinc oxide nanowires.

Lee WJ, Chang JG, Ju SP, Weng MH, Lee CH - Nanoscale Res Lett (2011)

Bottom Line: As the width of the nanowire decreases, Young's modulus, stress-strain behavior, and yielding stress all increase.In addition, the yielding strength and Young's modulus of Type III are much lower than the other two types, because Type I and II have prominent edges on the cross-section of the nanowire.These results indicate that the ultrathin nanowire possesses very high malleability.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Mechanical and Electro-Mechanical Engineering, Center for Nanoscience and Nanotechnology, National Sun Yat-sen University Kaohsiung, 804, Taiwan. jushin-pon@mail.nsysu.edu.tw.

ABSTRACT
Mechanical properties of ultrathin zinc oxide (ZnO) nanowires of about 0.7-1.1 nm width and in the unbuckled wurtzite (WZ) phase have been carried out by molecular dynamics simulation. As the width of the nanowire decreases, Young's modulus, stress-strain behavior, and yielding stress all increase. In addition, the yielding strength and Young's modulus of Type III are much lower than the other two types, because Type I and II have prominent edges on the cross-section of the nanowire. Due to the flexibility of the Zn-O bond, the phase transformation from an unbuckled WZ phase to a buckled WZ is observed under the tensile process, and this behavior is reversible. Moreover, one- and two-atom-wide chains can be observed before the ZnO nanowires rupture. These results indicate that the ultrathin nanowire possesses very high malleability.

No MeSH data available.


Related in: MedlinePlus

Atomic configurations of Type I under uniaxial loading. (a)-(f) show the corresponding snapshots of Type I at strain of 0.00%, 11.74%, 12.00%, 21.50%, 73.45%, and 100.00% respectively.
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Figure 5: Atomic configurations of Type I under uniaxial loading. (a)-(f) show the corresponding snapshots of Type I at strain of 0.00%, 11.74%, 12.00%, 21.50%, 73.45%, and 100.00% respectively.

Mentions: For Type I, the stress-strain curve is quite different than Type II and III. Figure 5 shows the deformation structure at different specific strains. Compared to Type II and III, the deformation behavior of Type I is totally different. As can be seen in Figure 5b, unlike the symmetrical phase transformation of Type II or III, the yielding of Type I is caused by a ZnO bond breaking, as shown by the arrow labeled 1. The unstable Zn and O atoms, then, lead to the first local buckling of the HX structure at the prominent edge of the cross-section of the Type I nanowire. Continuing, the local buckling of the HX structure induces the bending deformation of nanowire at the middle region and causes the second and third local buckling deformations as shown by arrows labeled 2 and 3. As the strain increases, the nucleation happens at the middle region (as illustrated in Figure 5c), and then the deformation region in the middle of the nanowire nucleates to a thinner HX structure (as illustrated in Figure 5d) until a strain of 21.5%. After the strain of 21.5%, the local HX structure gradually becomes a buckled structure. The buckled structure gradually extends to include the entire nanowire until a strain of 73.45%, as depicted in Figure 5e. Therefore, the stress-strain curve appears to show a significant zigzag fluctuation. After a strain of 73.45%, the middle region, marked by an arrow, starts to form the single atom chain. During the single atom chain growth, the buckled structure at both sides of the nanowire gradually relaxes and is restored to the original HX structure. The clear single atom chain bridged between two tubular tips is observed as shown in Figure 5f. Up until strain of 125%, the single atom chain is still not fractured.


Structure-dependent mechanical properties of ultrathin zinc oxide nanowires.

Lee WJ, Chang JG, Ju SP, Weng MH, Lee CH - Nanoscale Res Lett (2011)

Atomic configurations of Type I under uniaxial loading. (a)-(f) show the corresponding snapshots of Type I at strain of 0.00%, 11.74%, 12.00%, 21.50%, 73.45%, and 100.00% respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211442&req=5

Figure 5: Atomic configurations of Type I under uniaxial loading. (a)-(f) show the corresponding snapshots of Type I at strain of 0.00%, 11.74%, 12.00%, 21.50%, 73.45%, and 100.00% respectively.
Mentions: For Type I, the stress-strain curve is quite different than Type II and III. Figure 5 shows the deformation structure at different specific strains. Compared to Type II and III, the deformation behavior of Type I is totally different. As can be seen in Figure 5b, unlike the symmetrical phase transformation of Type II or III, the yielding of Type I is caused by a ZnO bond breaking, as shown by the arrow labeled 1. The unstable Zn and O atoms, then, lead to the first local buckling of the HX structure at the prominent edge of the cross-section of the Type I nanowire. Continuing, the local buckling of the HX structure induces the bending deformation of nanowire at the middle region and causes the second and third local buckling deformations as shown by arrows labeled 2 and 3. As the strain increases, the nucleation happens at the middle region (as illustrated in Figure 5c), and then the deformation region in the middle of the nanowire nucleates to a thinner HX structure (as illustrated in Figure 5d) until a strain of 21.5%. After the strain of 21.5%, the local HX structure gradually becomes a buckled structure. The buckled structure gradually extends to include the entire nanowire until a strain of 73.45%, as depicted in Figure 5e. Therefore, the stress-strain curve appears to show a significant zigzag fluctuation. After a strain of 73.45%, the middle region, marked by an arrow, starts to form the single atom chain. During the single atom chain growth, the buckled structure at both sides of the nanowire gradually relaxes and is restored to the original HX structure. The clear single atom chain bridged between two tubular tips is observed as shown in Figure 5f. Up until strain of 125%, the single atom chain is still not fractured.

Bottom Line: As the width of the nanowire decreases, Young's modulus, stress-strain behavior, and yielding stress all increase.In addition, the yielding strength and Young's modulus of Type III are much lower than the other two types, because Type I and II have prominent edges on the cross-section of the nanowire.These results indicate that the ultrathin nanowire possesses very high malleability.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Mechanical and Electro-Mechanical Engineering, Center for Nanoscience and Nanotechnology, National Sun Yat-sen University Kaohsiung, 804, Taiwan. jushin-pon@mail.nsysu.edu.tw.

ABSTRACT
Mechanical properties of ultrathin zinc oxide (ZnO) nanowires of about 0.7-1.1 nm width and in the unbuckled wurtzite (WZ) phase have been carried out by molecular dynamics simulation. As the width of the nanowire decreases, Young's modulus, stress-strain behavior, and yielding stress all increase. In addition, the yielding strength and Young's modulus of Type III are much lower than the other two types, because Type I and II have prominent edges on the cross-section of the nanowire. Due to the flexibility of the Zn-O bond, the phase transformation from an unbuckled WZ phase to a buckled WZ is observed under the tensile process, and this behavior is reversible. Moreover, one- and two-atom-wide chains can be observed before the ZnO nanowires rupture. These results indicate that the ultrathin nanowire possesses very high malleability.

No MeSH data available.


Related in: MedlinePlus