Synthesis, mechanical properties and microstructure of carbon nanotube reinforced magnesium metal composites
Final Report Abstract
In the funded project, carbon nanotube reinforced Mg composites via melting stirring were produced and characterised. Different approaches were applied to help improving CNT dispersion and their wettability in metal melt and composites, such as coating different metal nano-clusters on CNTs. A customised melt stirring furnace was designed and built with special features such as swtichable protective gas lines, HEPA filteration for nanoparticle safe handling, and attached devices for assissing nanoparticle dispersion directly in metal melt. An optimised manufacturing process was determined for composite production. The sample quality was also checked. Future modification on the furnace will be carried out such as a controlled cooling rate and different cover gas, in order to further understand the solidication interact with CNT dispersion, as well as to improve the cast quality. In order to help CNT dispersion and wettability in metal composites, CNTs were coated with different metals. Ni-coated CNTs were purchased and Pt coated CNTs were succesfully synthesisd in the lab. HRTEM and EDX confirmed the succesful coating of Pt on CNTs. Metal coated CNT Mg composites were also produced following the same procedure of pure AZ91 and CNT-AZ91composites. Their mechanical properties were measured and the microstructure was investigated. For Ni-coated CNT AZ91 composites. There was no clear improvement of compressive strength and yield strength although individual CNTs were observed on the fracture surface and improved wettabilit can be deducted. It may be explained that despite of those separated CNTs, there were still many big agglomerates observed on the fracture surface, acting as defects during the mechanical testing. Hardness tests showed an increasing trend for adding more Ni coated CNTs. The hardness had 15% improvement compared to pure AZ91. For Pt-coated CNT AZ91 composites, there was a clear trend of mechanical property improvement. The mechanical properties increased up to 21% compared to pure AZ91 and 10% compared to CNT-AZ91 composites without the coating. Further experiments are required to observe the interactions among metal coating – CNT – Mg matrix. The coating parameters will be studied to control the coating results, which may influence the composite properties as well. In the present study, the corrosion behaviour was also investigated. Results showed that the corrosion rate of MWNT/Mg composites was significantly higher than the corrosion rate of Mg. The corrosion rate of the composites also depends on the degree of dispersion of MWNTs during melt stirring process. The role of the MWNTs in increasing the corrosion rate clearly can be attributed to their high cathodic activity. In view of modifying the electrochemical behaviour of the composite materials it will be interesting to explore variations of the nano-carbon modifications coupled with Mg, as the electronic properties vary between them. Moreover, further work is planned to explore the effects of different size of nano-carbon clusters on the electrochemical behaviour of actively and passively dissolving Mg. As in the present case the orientation of the CNTs in the matrix is arbitrary and the CNTs have a tendency to clustering, the dimensions of the cathodically active sites may be larger than expected for single CNTs. It would be of interest to clarify, if a size limit for the here reported corrosion accelerating effects exists, for instance due to rapid overgrowth of truly nanosize-cathodes by oxide/hydroxide layers.
Publications
- “Fabrication of carbon nanotube/Mg alloy composites by melt stirring”. WCPT6 2010. Germany
Li Qianqian, Rottmair C, Singer R
- “Corrosion behaviour of multiwall carbon nanotube/magnesium composites in 3.5% NaCl“. Electrochimica Acta 2011; 56: 7141-7148
Turhan M, Li Qianqian, Jhaa H, Singer RF, Virtanen S
(See online at https://doi.org/10.1016/j.electacta.2011.05.082) - “Mg composites reinforced by metal coated CNTs”. Carbon 2011. China
Li Qianqian, Singer R
- “Influence of Dispersion Process on Corrosion of Multiwall Carbon Nanotube/Magnesium Alloy Composites”. Materials and Corrosion 2012; 63: 384-387
Li Qianqian, Turhan M, Rottmair CA, Singer RF, Virtanen S
(See online at https://doi.org/10.1002/maco.201006023) - “Carbon Nanotubes-reinforced copper matrix composites produced by melt stirring”. Journal of Nanoengineering and Nanosystems 2013; 227: 63-66
Hippmann S, Li Qianqian, Addinal R, Volk W
(See online at https://doi.org/10.1177/1740349912467730) - “Nanoparticle reinforced lightweight metal composites: An overview”. 2019, the 4th International Chinese Composite Congress. 2019, China
Li Qianqian, Markcoons D, Nasiri S, Zaiser M
- “Nickel coated carbon nanotubes in aluminum matrix composites: a multiscale simulation study”. European Physical Journal 2019; B 92 (8): 186
Nasiri S, Wang K, Yang M, Li Qianqian, Zaiser M
(See online at https://doi.org/10.1140/epjb/e2019-100243-6) - “Overview of different nanoparticle reinforced lightweight metal composites”. 2019. EUROMAT2019. Sweden
Li Qianqian, Markcoons D, Nasiri S, Zaiser M
- “Surface treatment of carbon nanotubes”. Euromat 2019
Hisham S, Shaffer M, Li Qianqian
- “Multilayer Structures of Graphene and Pt Nanoparticles: A Multiscale Computational Study”. Advanced Engineering Materials 2020; 22: 2000207
Nasiri S, Greff C, Wang K, Yang M, Li Qianqian, Moretti P and Zaiser M
(See online at https://doi.org/10.1002/adem.202000207)
