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CNT films show the conductivity benefits of including metallic NPs

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Flexible conductive sheets should be used in elastic electronic equipment due to their superior conductivity and deformability. In a study published in Scientific reportsfour types of stretchable conductive sheets were created by combining metallic nanoparticles on the surface of carbon nanotubes and distributing them in a polydimethylsiloxane framework.

Study: Modeling and characterization of electrical conductivity on metallic nanoparticle/carbon nanotube/polymer composites. Image Credit: Rost9/Shutterstock.com

Maintaining the flexibility of carbon nanotubes

Carbon nanotubes (CNTs) are frequently used in electronic equipment, transducers, sensors and biomaterials due to their exceptional electrical, mechanical and thermal characteristics. Several stretchable conductive composites based on carbon nanotubes and flexible polymers such as polydimethylsiloxane (PDMS) have been extensively studied.

The key to producing elastic polymer composites with high conductivity is to grow a conduction framework of carbon nanotubes in a virtually isolated polymer matrix. Increasing the CNT concentration of polymer composites can generally improve their conductance, but this will eventually decrease their flexibility.

Increasing the conductance of carbon nanotubes rather than increasing their quantity is a more advantageous technique for maintaining the flexibility of composites.

Ensure high conductivity of carbon nanotubes for good flexibility

Many studies on increasing the conductance of carbon nanotube/polymer composites at the nanometer scale have been published to date. Adding metallic nanoparticles (NPs) to the polymer structure is one of many techniques to increase the conductance of the composite.

Another viable way to increase the conductance of a carbon nanotube system is to coat it with a high conductivity alloy or metal particles (like gold and copper). Unfortunately, gold is too expensive for scalable use.

On the other hand, copper is much cheaper, but it is difficult to regulate the size of its nanoparticles (

The size of the nickel nanoparticles synthesized on the CNTs can be precisely regulated. Only a sufficient number of metallic nanoparticles deposited on the surface of the CNT can guarantee a good conductance of the carbon nanotube system.

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Block diagram of (a) Au/CNT and AuCu/CNT preparation process, (b) Ni/CNT preparation process, (c) Cu/CNT preparation process and (d) Metal films preparation process /CNT/PDMS. © Wang, Y., Lu, S. et al. (2022).

Research Methodology

This study fused NPs of nickel, gold, copper and AuCu alloys on the surface of carbon nanotubes. The resulting metal/CNT was then disseminated through a polydimethylsiloxane matrix to create an elastic Metal/CNT/PDMS composite sheet.

X-ray diffraction (XRD), scanning electron microscopy with high angle annular dark field test (HAADF-STEM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to analyze the microscopic architecture of specimens.

The electrical conductance of the resulting composites was determined using a four point approach. The metal/CNT/PDMS elastic sheets showed approximately two orders of magnitude higher electrical conductance than the CNT/PDMS elastic sheets.

A computational framework based on Metropolis methods and percolation theory was used to study the effect of metallic nanoparticles on the conductance of metal/CNT/PDMS foils.

The main parameters influencing the conductance of the developed metal/CNT/polymer composite were examined based on the experimental and computational results. In addition, the model estimated the electrical conductance information of elastic composites by combining various metallic or alloy NPs and changing different characteristics of the carbon nanotube structure.

Important Study Findings

By combining metal nanoparticles evenly distributed on the surface of carbon nanotubes, Au/CNT, Cu/CNT, Ni/CNT and AuCu/CNT were efficiently produced. HAADF-STEM and XRD results indicated that AuCu alloy particles with similar atomic ratios were fused to the surface of the nanotube.

Based on these results, conductive elastic sheets on PDMS substrate with various loadings of carbon nanotubes were produced. Electrical conductance test results revealed that the majority of metal/CNT/PDMS sheets produced possessed higher electrical conductance than CNT/PDMS sheets.

The addition of metallic nanoparticles increased the electrical conductance of carbon nanotubes and tunneling at nanotube intersections. Unlike simple CNT intersections, electrons must penetrate the metal nanoparticles of the nanotube at the metal/CNT interfaces and then pass through the polymeric insulating layer to cross to the next nanotube.

The calculation results revealed that the inherent conductance and aspect ratio of CNTs, as well as the inherent conductance, size and coverage ratio of metal nanoparticles were the main parameters influencing the electrical conductance of metal sheet/CNT. /polymer.

The numerical results also revealed that the conductance of elastic composites could exceed 100 S/m in Au/CNT/PDMS, Cu/CNT/PDMS, AuCu/CNT/PDMS, Ag/CNT/PDMS or CuAg/CNT/PDMS films. when the concentration of carbon nanotubes is 8% by weight, the coverage ratio of the metal nanoparticles is 100% and the inherent conductance of the nanotubes is 10 6 S/m.

Reference

Wang, Y., Lu, S. et al. (2022). Modeling and characterization of electrical conductivity on metallic nanoparticle/carbon nanotube/polymer composites. Scientific reports. Available at: https://doi.org/10.1038/s41598-022-14596-x

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