Maxime Noël

Incorporation of CNT-yarns into metals by laser melting of powder

Carbon Nanotubes, CNTs, have extraordinary properties and they can be spun into several meter long yarns with a diameter of the order of micrometer, and even be woven into fabrics. By embedding CNT-yarns or CNT-fabrics into metals, a new kind of composite material could be achieved that would enables the modification of the mechanical properties of a product along a designed path or domain. This paper discusses a preliminary experiment in which CNT-yarns and CNT-fabrics were successfully embedded between a steel substrate and a preplaced metal powder that was melted with an Yb:fibre laser. Suitable parameters were identified. The wire shape remained, i.e. the carbon did not dissolve or evaporate, but remained in the metal matrix. Ti-sputtering of the CNT-yarns prior to welding was advantageous for wetting and embedding. Certain powder materials such as Co-base alloy or Al-bronze turned out to be advantageous to the process. Raman spectroscopy has shown that the CNT-structure is lost for CNT-yarns too close to the molten zone. Further studies are needed, particularly mechanical testing to understand the interaction and reinforcement potential of CNT-yarn in a metal matrix under load. Preliminary bending tests and Finite Element Analysis have shown promise. Creative design solutions can be expected.Carbon Nanotubes, CNTs, have extraordinary properties and they can be spun into several meter long yarns with a diameter of the order of micrometer, and even be woven into fabrics. By embedding CNT-yarns or CNT-fabrics into metals, a new kind of composite material could be achieved that would enables the modification of the mechanical properties of a product along a designed path or domain. This paper discusses a preliminary experiment in which CNT-yarns and CNT-fabrics were successfully embedded between a steel substrate and a preplaced metal powder that was melted with an Yb:fibre laser. Suitable parameters were identified. The wire shape remained, i.e. the carbon did not dissolve or evaporate, but remained in the metal matrix. Ti-sputtering of the CNT-yarns prior to welding was advantageous for wetting and embedding. Certain powder materials such as Co-base alloy or Al-bronze turned out to be advantageous to the process. Raman spectroscopy has shown that the CNT-structure is lost for CNT-yarns too clos...

Effects of non-hydrostatic pressure on electrical resistance of bundled single-wall carbon nanotubes

Recent studies have shown that single wall carbon nanotubes (SWCNT) exhibit a sequence of phase transitions and demonstrate a high structural stability up to 35 GPa of quasi-hydrostatic pressure [1] beyond which an irreversible structural transformation occurs. Here we report on the study of electrical resistance of SWCNTs at pressures up to 34 GPa in the temperature range of 293 – 395 K. In the pressure range 10–25 GPathe rate of resistance change decreases considerably. We associate such behavior of the resistance with a structural modification of the SWCNTs or/and change of the conductivity character at high pressure. Raman spectra of the samples recovered after 30 GPa exhibit a large increase of defect concentration in the CNTs. Isobaric temperature dependences of the CNT resistance R(T) measured in the temperature range 300–400 K reveal some changes with pressure whereas the semiconducting character of the R(T) remains unaltered.