Zinc Oxide Nanostructures Synthesized by

Oxidization of ZincOxidization of Zinc

Syed Nasimul Alam ♦, Madhukar Poloju, Shakti Swarup

Sahu, Manish Kumar, Animesh Kumar Singh

♦ Corresponding author. Email: nasimulalam@yahoo.com (S.N.Alam)

Department of Metallurgical and Materials Engineering,National Institute of Technology-Rourkela,

Rourkela, Orissa, Pin-769008, India

(a) (b)

(c)SEM showing the surface of the as-received pure metallic Zn.

Element Wt.% At.%

Zn K 100.00 100.00

Totals 100.00

(c)

(b) SEM of Zn oxidized at 300oC for 2 h. (c) EDX analysis of the oxidized sample.

(a) (b)

(a-b) SEM images of pure Zn oxidized at 400oC for 2 h.

(c) (d)

(c-d) SEM images of pure Zn oxidized at 500oC for 2 h.

(a) (b)

(a-b) SEM images of pure Zn oxidized at 600oC for 2 h.

(c) (d)( ) ( )

(c-d) SEM images of pure Zn oxidized at 700oC for 2 h.

(a) (b)

(a)(b)

(a-b) SEM images of pure Zn oxidized at 800oC for 2 h.

(c) (d)

(c-d) SEM images of pure Zn oxidized at 900oC for 2 h.

(a) (b)

(a-b) SEM images of pure Zn oxidized at 1000oC for 2 h.

XRD plots of Zn oxidized at 300, 400,700 and 800oC for 2 h.

Study of the Oxidation of Zn Powder

Oxidized at 200oC for 2 h Oxidized at 300oC for 2 h

Oxidized at 400oC for 2 h Oxidized at 500oC for 2 h

Study of the Oxidation of Zn Powder

Oxidized at 600oC for 2 h Oxidized at 700oC for 2 h

Oxidized at 800oC for 2 h

ZnO Nanostructures in the Zn Electrode of a Zn-C Dry Cell

Zn(s) → Zn2+ + 2 e−( )2NH4

+(aq) + 2 e- → H2(g) + 2NH3(aq) 2MnO2(s) + H2(g) → Mn2O3(s) + H2O(l)

Zn2+ + 2NH3(aq) → Zn(NH3)22+ (aq)

Although there could be several other reactionsAlthough there could be several other reactions taking place the overall reaction in a Zn-C dry cell can be represented as:________________________________

Zn(s) + 2MnO (s) + 2NH +(aq) → Mn O (s) +Zn(s) + 2MnO2(s) + 2NH4 (aq) → Mn2O3(s) + Zn(NH3)2

2+ (aq) + H2O(l)________________________________One of the reactions that could lead to the formation of ZnO in the Zn electrode is,of ZnO in the Zn electrode is,

H2O(l) → H+(aq) + (OH)- (aq)Zn(s) + 2 OH- (aq) → ZnO + H2O + 2e-

________________________________

Zn casing that serves both as the container and the - ve terminal.

C or graphite rod + ve terminalsurrounded by the electrolyte.

The electrolyte is a mixture MnO2, NH4Cl and ZnCl2.

(a)

ZnO structure illustrating clearly the SRAS

60

60distribution.

60

60

6060

60

60 60

60

(b)

(a) SEM image of the surface of the Zn electrode of a Zn-C dry cell. (b) Schematic showing the relative position of the SRAS.

(a)

(b)Element Wt. % At. %

O K 17.42 44.79

Cl K 6.16 7.14

( )

Zn L 76.42 48.07

Totals 100.00

(a) SEM image of the surface of the Zn electrode of a Zn-C dry cell.(b) EDX analysis of the ZnO formed in the Zn electrode of a Zn-C dry cell.

(a) (b)

(c) (d)

(a-d) SEM images of Zn casings of various used Zn-C drycells showing the formation of ZnO nanorods.

Conclusions1. The simple technique of oxidation of metallic Zn in air has been demonstrated as a very

economical and effective technique for the synthesis of ZnO. The ZnO nanostructures were successfully synthesized by oxidizing pure Zn in the temperature range 400-600oC. A large variety of nanostructures were seen at these oxidizing temperatures. The

t t d i f Z O t l d d th idi i t tstructure and size of ZnO strongly depends on the oxidizing temperature.

2. It is found that the growth of ZnO structures increases with increasing temperature of oxidation. The scanning electron microscopy observation shows that needle like or rod like structures of ZnO could be formed at temperatures above 700oC.

3. The needle like or rod like structure of ZnO were found to grow very uniformly in size and shape and were very densely located on the metallic Zn surface at oxidation temperatures ranging from 700-900oC in comparison to the various nanostructured ZnO which grew less densely and looked more scattered and nonuniform in size and structurestructure.

4. Formation of ZnO was confirmed only at temperatures above 300oC. Comparison of the results of thermogravimetric and SEM analysis suggests that oxidation takes place only above 200oC and structures of ZnO could be seen at oxidizing temperatures above 300oC.

5. There is clear indication of the fact that the Zn casing of the Zn-C dry cell gets oxidized due to the electrochemical reaction with the electrolyte of the cell forming ZnO nanostructures. The nanostructures of ZnO are of various shapes. Rod-like, wire-like and star-like nanostructures of ZnO have been found in the surface of the Zn electrode

f h Z C d ll h i i i h h l l Th Z O dof the Zn-C dry cell that is in contact with the electrolyte. The ZnO nanostructures do not have very high purity and are also not highly stoichiometric.

References1. Subramanyam, T. K., Naidu, B. Srinivasulu, Uthana, S., Cryst. Res. Technol. Vol. 34

(1999) (8), pp. 981–988.

2. Wang, Z. L., J. Phys.: Condens. Matter. 16 (2004) R829–R858.

3. Wu, D., Bai, Z., Jiang, K., Materials Letters 63 (2009), pp.1057–1060.

4. Yawong,O., Choopun, S., Mangkorntong, P., Mangkorntong, N., Chiang M. University Journal Special Issue On Nanotechnology Vol. 4 (2005) (1).

5. Stolt, L., Hedstrom, J., Kessler, M., Ruckh, Velthaus, K. O., Schock, H. W., Appl. Phys. Lett. Vol. 62 (1993), pp. 597.

6. Eveready Carbon Zinc (Zn/MnO²), Application Manual Eveready Battery Co. Inc., 2001, y ( ), pp y y , ,Page 1-13.

7. Roy, S., Basu, S., Bull. Mater. Sci. Vol. 25 (2002) (6), pp. 513–515.

8 Subramanyam T K Naidu B Srinivasulu Uthanna S Cryst Res Technol Vol 358. Subramanyam, T. K., Naidu, B. Srinivasulu, Uthanna, S., Cryst. Res. Technol. Vol. 35 (2000) (10), pp. 1193–1202.

9. Zhang, J., Yang, Y., Xu, B., Jiang, F. and Li, J., Journal of Crystal Growth, Vol. 280 (2005) (3-4), pp. 509–515.

10. Sekar, A., Kim, S. H., Umar, A. and Hahn, Y. B., J. Cryst. Growth Vol. 277 (2005) (1-4), pp. 471–478.