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The surface condition effect of Cu2O flower/grass-like nanoarchitectures grown on Cu foil and Cu film.

Hu L, Ju Y, Hosoi A, Tang Y - Nanoscale Res Lett (2013)

Bottom Line: The FGLNAs are approximately 3.5 to 12 μm in size, and their petals are approximately 50 to 950 nm in width.The high compressive stress caused by a large oxide volume in the Cu2O layer on the specimen surface played an important role in the growth of FGLNAs.PACS: 81.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Mechanical Science and Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan. ju@mech.Nagoya-u.ac.jp.

ABSTRACT
Cu2O flower/grass-like nanoarchitectures (FGLNAs) were fabricated directly on two category specimens of Cu foils and Cu film using thermal oxidation method. The FGLNAs are approximately 3.5 to 12 μm in size, and their petals are approximately 50 to 950 nm in width. The high compressive stress caused by a large oxide volume in the Cu2O layer on the specimen surface played an important role in the growth of FGLNAs. The effects of surface conditions, such as the surface stresses, grain size, and surface roughness of Cu foil and Cu film specimens, on the FGLNA growth were discussed in detail. PACS: 81. Materials science; 81.07.-b Nanoscale materials and structures: fabrication and characterization; 81.16.Hc Catalytic methods.

No MeSH data available.


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X-ray stress of unpolished Cu foil, polished Cu foil (400 grit), and Cu film specimens before heating.
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Figure 7: X-ray stress of unpolished Cu foil, polished Cu foil (400 grit), and Cu film specimens before heating.

Mentions: To further investigate the effect of surface conditions on the generation of FGLNAs, the X-ray sin2ψ method [24] was used to measure the residual stresses in unpolished Cu foil, polished Cu foil (400 grit), and Cu film specimens before thermal oxidation, respectively. Before heating, the X-ray diffraction (sin2ψ) method was employed using the {222} diffraction Cu peak, occurring at a diffraction angle of approximately 2θ = 95.2°. As shown in Figure 6, slow step scanning in the range of approximately 92.5° to 97.5° of 2θ was conducted for ψ-angles in the range of 0° to 45°. Based on the results of Figure 6, the stresses were calculated using JADE software (version 6.5). As shown in Figure 7, compressive stresses were measured for unpolished Cu foil, polished Cu foil (400 grit), and Cu film specimens to be 10, 99, and 120 MPa, respectively. Therefore, the polishing put a pre-stress in the Cu foil specimen. During polishing, the grits of abrasive paper squeeze the surface of the Cu foil and rub it into the rough surface which will leave a compressive residual stress on the surface of the polished Cu foil specimen [25]. It can be found that Figure 7 has a similar shape with Figure 2, which indicates that the initial compressive stress on the specimen surface has a relationship with the density of FGLNAs grown on the specimen. It is considered that initial compressive stress has an action to obstruct the volume expansion of the oxide layer which formed on the specimen surface during the heating process. Therefore, a higher effective VGS would occur for the same oxide volume expansion, which induces more and faster diffusion of Cu atoms to the specimen’s surface, thereby increasing the density of grown FGLNAs. On the other hand, the heating time for the first appearance of FGLNAs was also observed for the specimens of unpolished Cu foil, polished Cu foil (400 grit), and Cu film. As shown in Figure 8, the heating time for the specimens of unpolished Cu foil, polished Cu foil (400 grit), and Cu film is 3, 2, and 1.5 h, respectively. Compared with the results shown in Figure 7, higher initial compressive stress in the specimen leads to shorter heating time for the first appearance of FGLNAs. It indicates that higher vertical gradient stress promotes the diffusion of Cu atoms, thereby speeding up the growth of FGLNAs. Therefore, the same heating time results in the highest density of FGLNAs grown on the Cu film specimen. Moreover, the thickness of the Ni catalyst can also affect the growth time of Cu2O FGLNAs but does not affect the morphology and size. Thinner thickness of the Ni film would lead to a longer time for the growth of FGLNAs.


The surface condition effect of Cu2O flower/grass-like nanoarchitectures grown on Cu foil and Cu film.

Hu L, Ju Y, Hosoi A, Tang Y - Nanoscale Res Lett (2013)

X-ray stress of unpolished Cu foil, polished Cu foil (400 grit), and Cu film specimens before heating.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4231356&req=5

Figure 7: X-ray stress of unpolished Cu foil, polished Cu foil (400 grit), and Cu film specimens before heating.
Mentions: To further investigate the effect of surface conditions on the generation of FGLNAs, the X-ray sin2ψ method [24] was used to measure the residual stresses in unpolished Cu foil, polished Cu foil (400 grit), and Cu film specimens before thermal oxidation, respectively. Before heating, the X-ray diffraction (sin2ψ) method was employed using the {222} diffraction Cu peak, occurring at a diffraction angle of approximately 2θ = 95.2°. As shown in Figure 6, slow step scanning in the range of approximately 92.5° to 97.5° of 2θ was conducted for ψ-angles in the range of 0° to 45°. Based on the results of Figure 6, the stresses were calculated using JADE software (version 6.5). As shown in Figure 7, compressive stresses were measured for unpolished Cu foil, polished Cu foil (400 grit), and Cu film specimens to be 10, 99, and 120 MPa, respectively. Therefore, the polishing put a pre-stress in the Cu foil specimen. During polishing, the grits of abrasive paper squeeze the surface of the Cu foil and rub it into the rough surface which will leave a compressive residual stress on the surface of the polished Cu foil specimen [25]. It can be found that Figure 7 has a similar shape with Figure 2, which indicates that the initial compressive stress on the specimen surface has a relationship with the density of FGLNAs grown on the specimen. It is considered that initial compressive stress has an action to obstruct the volume expansion of the oxide layer which formed on the specimen surface during the heating process. Therefore, a higher effective VGS would occur for the same oxide volume expansion, which induces more and faster diffusion of Cu atoms to the specimen’s surface, thereby increasing the density of grown FGLNAs. On the other hand, the heating time for the first appearance of FGLNAs was also observed for the specimens of unpolished Cu foil, polished Cu foil (400 grit), and Cu film. As shown in Figure 8, the heating time for the specimens of unpolished Cu foil, polished Cu foil (400 grit), and Cu film is 3, 2, and 1.5 h, respectively. Compared with the results shown in Figure 7, higher initial compressive stress in the specimen leads to shorter heating time for the first appearance of FGLNAs. It indicates that higher vertical gradient stress promotes the diffusion of Cu atoms, thereby speeding up the growth of FGLNAs. Therefore, the same heating time results in the highest density of FGLNAs grown on the Cu film specimen. Moreover, the thickness of the Ni catalyst can also affect the growth time of Cu2O FGLNAs but does not affect the morphology and size. Thinner thickness of the Ni film would lead to a longer time for the growth of FGLNAs.

Bottom Line: The FGLNAs are approximately 3.5 to 12 μm in size, and their petals are approximately 50 to 950 nm in width.The high compressive stress caused by a large oxide volume in the Cu2O layer on the specimen surface played an important role in the growth of FGLNAs.PACS: 81.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Mechanical Science and Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan. ju@mech.Nagoya-u.ac.jp.

ABSTRACT
Cu2O flower/grass-like nanoarchitectures (FGLNAs) were fabricated directly on two category specimens of Cu foils and Cu film using thermal oxidation method. The FGLNAs are approximately 3.5 to 12 μm in size, and their petals are approximately 50 to 950 nm in width. The high compressive stress caused by a large oxide volume in the Cu2O layer on the specimen surface played an important role in the growth of FGLNAs. The effects of surface conditions, such as the surface stresses, grain size, and surface roughness of Cu foil and Cu film specimens, on the FGLNA growth were discussed in detail. PACS: 81. Materials science; 81.07.-b Nanoscale materials and structures: fabrication and characterization; 81.16.Hc Catalytic methods.

No MeSH data available.


Related in: MedlinePlus