Gas-to-nanotextile: high-performance materials from floating 1D nanoparticles

Suspended in the gas phase, 1D inorganic nanoparticles (nanotubes and nanowires) grow to hundreds of microns in a second and can be thus directly assembled into freestanding network materials. The corresponding process continuously transforms gas precursors into aerosols into aerogels into macroscopic nanotextiles. By enabling the assembly of very high aspect ratio nanoparticles, this processing route has translated into high-performance structural materials, transparent conductors and battery anodes, amongst other embodiments. This paper reviews progress in the application of such manufacturing process to nanotubes and nanowires. It analyses 1D nanoparticle growth through floating catalyst chemical vapour deposition (FCCVD), in terms of reaction selectivity, scalability and its inherently ultra-fast growth rates (107-108 atoms per second) up to 1000 times faster than for substrate CVD. We summarise emerging descriptions of the formation of aerogels through percolation theory and multi-scale models for the collision and aggregation of 1D nanoparticles. The paper shows that macroscopic ensembles of 1D nanoparticles resemble textiles in their porous network structure, high flexibility and damage-tolerance. Their bulk properties depend strongly on inter-particle properties and are dominated by alignment and volume fraction. Selected examples of nanotextiles that surpass granular and monolithic materials include structural fibres with polymer-like toughness, transparent conductors, and slurry-free composite electrodes for energy storage.Comment: 36 pages, 25 figure

Simulated Behavior of CNT Wires Irradiated in the HiRadMat Experimental Line at CERN

International audienceWith the planned increase of luminosity at CERN for HL-LHC and FCC, instruments for beam quality control must meet new challenges. The current wires, made up of plain carbon fibers and gold-plated tungsten would be damaged due to their interactions with the higher luminosity beams. We are currently testing a new and innovative material, with improved performance: carbon nanotube fibers (CNTF). The HiRadMat (High Radiation for Material) experimental line at the output of the SPS is a user facility which can irradiate fix targets up to 440 GeV/c. CNTF with various diameters were irradiated in HiRadMat with different intensities, later imaged with a SEM microscope and tested for their mechanical properties. In addition, simulations have been carried out with the FLUKA particle physics Monte-Carlo code, in order to better understand the mechanisms and assess the energy deposition from protons at 440 GeV/c in those CNTF wires, depending mainly on their diameters and densities. This could lead to a good estimation of the CNTF temperature during irradiation. In this contribution, we first present the HiRadMat experimental setup and then we discuss the results of our FLUKA simulations

Post-Treatments for Multifunctional Property Enhancement of Carbon Nanotube Fibers from the Floating Catalyst Method

We investigated the effects of the synthesis conditions and condensation processes on the chemical compositions and multifunctional performance of the directly spun carbon nanotube (CNT) fibers. On the basis of the optimized synthesis conditions, a two-step post-treatment technique which involved acidification and epoxy infiltration was also developed to further enhance their mechanical and electrical properties. As a result, their tensile strength and Young’s modulus increased remarkably by 177% and 325%, respectively, while their electrical conductivity also reached 8235 S/cm. This work may provide a general strategy for the postprocessing optimization of the directly spun CNT fibers. The treated CNT fibers with superior properties are promising for a wide range of applications, such as structural reinforcements and lightweight electric cables

Continuous Carbon Nanotube-Based Fibers and Films for Applications Requiring Enhanced Heat Dissipation

The production of continuous carbon nanotube (CNT) fibers and films has paved the way to leverage the superior properties of individual carbon nanotubes for novel macroscale applications such as electronic cables and multifunctional composites. In this manuscript, we synthesize fibers and films from CNT aerogels that are continuously grown by floating catalyst chemical vapor deposition (FCCVD) and measure thermal conductivity and natural convective heat transfer coefficient from the fiber and film. To probe the mechanisms of heat transfer, we develop a new, robust, steady-state thermal characterization technique that enables measurement of the intrinsic fiber thermal conductivity and the convective heat transfer coefficient from the fiber to the surrounding air. The thermal conductivity of the as-prepared fiber ranges from 4.7 ± 0.3 to 28.0 ± 2.4 W m^–1 K^–1 and depends on fiber volume fraction and diameter. A simple nitric acid treatment increases the thermal conductivity by as much as a factor of ∼3 for the fibers and ∼6.7 for the thin films. These acid-treated CNT materials demonstrate specific thermal conductivities significantly higher than common metals with the same absolute thermal conductivity, which means they are comparatively lightweight, thermally conductive fibers and films. Beyond thermal conductivity, the acid treatment enhances electrical conductivity by a factor of ∼2.3. Further, the measured convective heat transfer coefficients range from 25 to 200 W m^–2 K^–1 for all fibers, which is higher than expected for macroscale materials and demonstrates the impact of the nanoscale CNT features on convective heat losses from the fibers. The measured thermal and electrical performance demonstrates the promise for using these fibers and films in macroscale applications requiring effective heat dissipation

Revealing Chemical Heterogeneity of CNT Fiber Nanocomposites via Nanoscale Chemical Imaging

Lightweight nanocomposites reinforced with carbon nanotube (CNT) assemblies raise the prospects for a range of high-tech engineering applications. However, a correlation between their heterogeneous chemical structure and spatial organization of nanotubes should be clearly understood to maximize their performance. Here, we implement the advanced imaging capabilities of atomic force microscopy combined with near-field infrared spectroscopy (AFM-IR) to analyze the intricate chemical structure of CNT fiber-reinforced thermoset nanocomposites. As an example, we unravel the chemical composition of a nanothin polymer interphase exclusively from CNT assemblies and visualize in a two- and three-dimensional format with resolution of sub-30 nm. We furthermore introduce a contact frequency map colocalized with CNTs and surrounding polymer, which might correlate the local mechanical properties with polymer chemistry and the high anisotropy of CNTs. Nanoresolved chemical imaging offers possibilities for in-depth characterization of next-generation composite materials and devices based on CNT assemblies interacting with a certain chemical environment