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Dry Sintered Metal Coating of Halloysite Nanotubes

Advanced Characterization and Processing Group, Oak Ridge Associated Universities, Savannah River National Laboratory, Aiken, SC 29803, USA
Center for Biomedical Engineering and Rehabilitation Science, Louisiana Tech University, Ruston, LA 71272, USA
Molecular Science and Nanotechnology, Louisiana Tech University, Ruston, LA 71272, USA
Nanosystem Engineering Program, Louisiana Tech University, Ruston, LA 71272, USA
Author to whom correspondence should be addressed.
Academic Editor: Raed Abu-Reziq
Appl. Sci. 2016, 6(9), 265;
Received: 31 May 2016 / Accepted: 6 September 2016 / Published: 19 September 2016
Halloysite nanotubes (HNTs) are a naturally-occurring aluminosilicate whose dimensions measure microns in length and tens of nanometers in diameter. Bonding defects between the alumina and silica lead to net negative and positive charges on the exterior and interior lumen, respectively. HNTs have been shown to enhance the material properties of polymer matrices and enable the sustained release of loaded chemicals, drugs, and growth factors. Due to the net charges, these nanotubes can also be readily coated in layered-depositions using the HNT exterior lumen’s net negative charge as the basis for assembly. These coatings are primarily done through wet chemical processes, the majority of which are limited in their use of desired chemicals, due to the polarity of the halloysite. Furthermore, this restriction in the type of chemicals used often requires the use of more toxic chemicals in place of greener options, and typically necessitates the use of a significantly longer chemical process to achieve the desired coating. In this study, we show that HNTs can be coated with metal acetylacetonates—compounds primarily employed in the synthesis of nanoparticles, as metal catalysts, and as NMR shift reagents—through a dry sintering process. This method was capable of thermally decaying the metal acetylacetonate, resulting in a free positively-charged metal ion that readily bonded to the negatively-charged HNT exterior, resulting in metallic coatings forming on the HNT surface. Our coating method may enable greater deposition of coated material onto these nanotubes as required for a desired application. Furthermore, the use of chemical processes using toxic chemicals is not required, thus eliminating exposure to toxic chemicals and costs associated with the disposal of the resultant chemical waste. View Full-Text
Keywords: 3D printing; filaments; additive manufacturing; halloysite 3D printing; filaments; additive manufacturing; halloysite
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MDPI and ACS Style

Nicholson, J.C.; Weisman, J.A.; Boyer, C.J.; Wilson, C.G.; Mills, D.K. Dry Sintered Metal Coating of Halloysite Nanotubes. Appl. Sci. 2016, 6, 265.

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