Loading...

Production and Properties of Reduced Graphene Oxide- Zinc Nanocomposite Coating on Steel

Moshgi Asl, Somayyeh | 2015

490 Viewed
  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 48173 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Afshar, Abdollah
  7. Abstract:
  8. In this project, graphene oxide was produced by chemical method (modified hummers method) because of simplicity and reproductiblity in the manufacuring process. Zinc nanoparticles were produced from pure zinc anode in the graphene oxide solution (anodic dissolution). Nanocomposite coating of reduced graphene oxide – zinc was created by electrochemical reduction with voltage pulse. Optimization of corrosion current density of the coating was done by design of experiments software (central composite design). To achieve this goal, several parameters such as cycles of zinc dissolution, frequency, duty cycle, total time of coating and applied voltage were examined. Using analysis of variance (ANOVA), it was found that the relationship of these variables to obtain corrosion current density is based on the interaction of two factors (2FI). Results showed that in terms of dissolution cycles 80, time 22 minutes, duty cycle 21%, frequency 145 Hz, potential -1.47 V, optimized coating with desirability of 72% is created. Plarization and electrochemical impedance spectroscopy tests were conducted to evaluate the the corrosion behaviour of coating. The results indicat that in the presence of rGO-Zn coating , due to simultaneous presence of graphene and zinc with two different mechanisms for corrosion prevention (zinc as a sarificial agent and graphene as barrier layer), the corrosion potential shifts from -0.58 to -0.77 (more negative values) and polarization resistance increases from 5.9 KΩ.cm2 to 1462.7 KΩ.cm2 . Decline in corrosion current density from 1.5 µA.cm-2 to 7µ10-3 µA.cm-2 and corrosion rate from 17.1 µm.year-2 to 0.08 µm.year-2 showed that the corrosion rate of steel in case of nanocomposite coating decreases by 99.5%. The morphology and structure of coating were examined by XRD,raman spectroscopy, FT-IR, XPS, AFM and FE-SEM . Shift of D and G bands to 1313 cm-1 and 1562 cm-1 in raman spectroscopy and removal of peaks related to oxygen-containing groups in FT-IR and XPS spectrum indicated electrochemical reduction of graphene oxide nanosheets. XPS spectrum and FE-SEM images confirmed presence of zinc nanoparticles and their uniform distribution on the graphene nanosheets. Surface roughness was estimated about 65 nm by AFM and coating thickness was measured 3.2 µm using scanning electron microscopy. Friction coeficient of the optimized coating was calculated about 0.47 by nanoscratch test
  9. Keywords:
  10. Nanocomposite ; Optimization ; Corrosion Resistance ; Experiments Design ; Reduced Graphene Oxide ; Nano-Composite Coating

 Digital Object List

 Bookmark

No TOC