Atomic layer deposition onto carbon fiber fabrics

Abstract

Carbon fiber fabrics, consisting of interwoven bundles of 3000 single fibers, were coated with Al2O3 using the atomic layer deposition (ALD) process, exposing the fabrics to alternating pulses of trimethyl aluminium and water vapors. The thickness and uniformity of the coatings were investigated using scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The obtained coatings were conformal, 84 ALD cycles gave rise to approximately 20‐nm‐thick coatings and 168 ALD cycles to approximately 40‐nm‐thick coatings. It was found, that a uniform coating can be obtained at a purge time of 40 seconds. Reducing purge times below 20 seconds gives rise to increased particle growth and thus the coating becomes inhomogeneous. Initially, the samples that were coated had a size of 2×10 cm (thickness 0.3 mm). The size of the fabric was subsequently increased up to 8×20 cm and a uniform coating of the same quality was obtained. By oxidizing the coated fabrics, fabrics composed of interwoven alumina microtubes were obtained. Infiltration of the microtubes with solutions of two distinguishable fluorescent dyes showed that interchange of the dyes between warp and weft microtubes occurs, but is absent at approximately 20% of the crossovers. Taking all our findings into account, we conclude that the majority of the fibers were separated from each other by the coating prior to the oxidation. This work demonstrates that ALD is a suitable method to produce thin, conformal coatings on the surface of carbon fiber fabrics.

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“…Meanwhile, carbon fibers are sensitive to oxidation and tensile properties will deteriorate strongly when temperatures exceeding 400 o C in oxidizing humid conditions [39][40][41][42]…”

Amorphous Alumina Thin Films Deposited on Carbon Microfibers As Interface Layer for Thermal Oxidation Barriers

“…1,10−13 Indeed, ALD relies on the sequential injection of two coreactants, thus allowing for the deposition of a conformal layer through self-limitation of the half-reactions, constrained in thickness to one atomic layer of the deposited elements. 1,10,11,14,15 Owing to the gas phase process that is ALD, the conformal deposition was also successfully reported on three-dimensional substrates and textured surfaces. 1,10,11,15−17 To answer the multipart problem of deposition of an efficient refractory OBL on a carbon surface exhibiting a sharp interface with the carbon microfiber and with thermal expansion coefficients in a compatible range and a density light enough to limit the loss in elongation modulus, several compositions of thin films have been explored, namely, vitreous materials such as boron, 18 zirconium, 7,18 or silicon, 2,9 and light metal oxides such as alumina or titania.…”

Functionalization of Carbon Electrodes with Nanotitania by Atomic Layer Deposition

“…Several studies have been conducted on ALD coating bers for various applications [z5]. e application of TiO 2 ALD as a photocatalytic is plausible due to the physicochemical properties of titania and the possibility of its coupling with other semiconductors [6,7], while Al 2 O 3 is for its hydrophobicity [8,9]. e capacity of ALD to form a controlled thin lm, even on very porous and intricate structures, has already been demonstrated before.…”