Titanium dioxide protection against Al 4 C 3 formation during fabrication of aluminum-TiO 2 coated MWCNT composite

L. A. Ardila-Rodríguez, B. R.C. Menezes, L. A. Pereira, A. C. Oliveira, D. N. Travessa

Research output: Contribution to journalArticleScientificpeer-review

8 Citations (Scopus)


Aluminum and aluminum alloys have been very useful in the industry, mainly in the transport sector. So, is important to improve their mechanical properties to increase their applications. Carbon nanotubes (CNTs) could be an excellent reinforcing phase for metal matrix composites, specifically for composites with aluminum or aluminum alloy matrix. However, CNTs dispersion, wettability, and interaction with the matrix must be improved, without damaging their structure. In this work, multi-walled CNTs (MWCNTs) were coated by the sol-gel process with a titanium oxide (TiO 2 ) layer with three different thickness and calcined at two different temperatures: 500 °C and 750 °C. The resultant powder was mixed by electrostatic adsorption method with aluminum powder and cold compacted. To simulate high temperature processing, the compacted disks were pressureless heated at 850 °C, aiming to check the effect of TiO 2 in protecting the MWCNT when in contact with melted Al. The TiO 2 coated MWCNT samples were characterized by a range of analytical techniques including Field-Emission Gun Scanning Electron Microscopy (FEG-SEM), X-ray diffraction (XRD), Z-Potential, Brunauer–Emmett–Teller (BET), Energy Dispersive X-Ray Spectroscopy (EDS) and Raman Spectroscopy (RS). The effect of the TiO 2 layer as a protective barrier on the MWCNT against the Al 4 C 3 formation during the heating process and the hardness of the Al/MWCNT (coated and uncoated) composite were studied. The results show that the MWCNT were successful coverage by a uniform amorphous TiO 2 layer. After calcination at 500 °C and 750 °C, the layer was completely crystallized into a TiO 2 film, with reduced surface area and pore volume. Electrostatic adsorption between TiO 2 covered MWCNT and Al powders in aqueous suspension was found to disperse the reinforcing phase prior to consolidation. On the heat-treated discs, the formation of Al 4 C 3 phase was observed to occur only for uncoated MWCNT samples, showing that the TiO 2 layer effectively protected the nanotubes in presence of melted Al. The microhardness of the heated samples was increased up to 26% when reinforced with MWCNT and up to 46% when reinforced with TiO 2 coated MWCNT, compared with pure aluminum.

Original languageEnglish
Pages (from-to)772-782
Number of pages11
JournalJournal of Alloys and Compounds
Publication statusPublished - 5 Apr 2019
Externally publishedYes


  • Al C
  • Carbon nanotubes
  • Metal matrix composites
  • TiO coating
  • Al4C3
  • TiO2 coating


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