Aluminum phosphate was deposited onto bundles of carbon fibers and flat glassy carbon substrates using atomic layer deposition by exposing them to alternating pulses of trimethylaluminum and triethylphosphate vapors. Energy dispersive X-ray spectroscopy (EDXS) and solid state nuclear magnetic resonance (SS-NMR) spectra confirmed that the coating comprises aluminum phosphate (orthophosphate as well as other stoichiometries). Scanning electron microscopic (SEM) images revealed that the coatings are uniform and conformal. After coating, the fibers are still separated from each other like the uncoated fibers. Thermogravimetric analysis (TGA) indicates an improvement of oxidation resistance of the coated fibers compared to uncoated fibers.
Layers of alumina were deposited on to bundled carbon fibers in an atomic layer deposition (ALD) process via sequential exposure to vapors of aluminium chloride and water, respectively. Scanning electron microscopic (SEM) images of the coated fibers revealed that each individual fiber within a bundle was coated evenly and separately, fibers are not bridged by the coating. SEM and transmission electron microscopic (TEM) images indicate that the coating was uniform and conformal with good adhesion to the fiber surface. Average deposition rate, measured from SEM images, was 0.06 nm per cycle at 500 °C. SEM also revealed that at deposition temperatures of 500 °C few of the fibers were damaged. At temperatures of 300 °C, no damaged fibers were observed, the average deposition rate decreased down to 0.033 nm per cycle. Oxidation resistance of the alumina-coated fibers was characterized by thermogravimetric analysis (TGA). The alumina coating improved oxidation resistance of the carbon fiber significantly. Oxidation onset temperature was 600 °C for fibers coated with a 45 nm thick alumina. Uncoated fibers, on the other hand, started to oxidize at temperatures as low as 250 °C.
Bundles of carbon fibers were successfully coated with alumina by atomic layer deposition via sequential exposures to trimethylaluminum and water at 77°C. Fibers were not damaged by this procedure. Scanning electron microscopy (SEM) images revealed that individual filaments were coated separately with a smooth layer; no bridging of fibers was observed. Transmission electron microscopy (TEM) and SEM images indicate that the coating was conformal and adhered well to the fiber surface. The average deposition rate was 0.25±0.02 nm/cycle, calculated from SEM images obtained at various positions of the fibers and of fibers coated with various numbers of cycles. In addition to image analysis, the coating thickness was as well estimated from the elemental composition of selected parts of a fiber bundle that was coated by 450 cycles. Along the fiber axis, the weight fraction of aluminum of the coated fibers varied from 5.3 to 6.5 wt% and perpendicular to the bundle axis it varied from 4.8 to 7.4 wt%. This translates into a variation of the estimated coating thickness along the fiber from 166 to 126 nm and perpendicular to it from 114 to 183 nm. One can estimate independently an average coating thickness from the analysis of SEM images of this specific bundle of 126 nm. The alumina coating improved oxidation resistance of the carbon fiber significantly. The oxidation onset temperature was 600°C for fibers coated with a 30‐nm‐thick layer of alumina and increased gradually with increasing coating thickness up to 660°C at a thickness of 120 nm. On the other hand, uncoated fibers started to oxidize already at 300°C.
T HERE was a mistake in Fig. 8 of the original article. The thermogravimetric analysis of the uncoated fibres was assigned to the wrong time scale and this gave rise to incorrect assignments of oxidation temperatures. The correct diagram is shown below.Taking the corrected diagram into account, the following passages in the text need to be replaced.In the abstract, the last two sentences need to be replaced by:The oxidation onset temperature was 630°C for both uncoated fibers and fibers coated with a 30-nm-thick layer of alumina. The oxidation onset temperature increased gradually with increasing coating thickness up to 660°C at a thickness of 120 nm.Page 2014, left column, last paragraph, last two sentences and right column, first paragraph, first sentence need to be replaced byThe results are shown in Fig. 8; the oxidation onset temperature (3% weight loss) for the uncoated fiber is approximately 630°C and the fibers are completely burned at temperatures of approximately 825°C. In case of fibers coated with a 33-nm-thick layer of alumina, the oxidation starts at almost the same temperature and the fibers are burned completely at a temperature of approximately 870°C. With increasing thickness of the coating, the oxidation onset temperature increases slightly and also the amount of ash. Oxidation onset temperature reached a plateau value of 660°C for fibers bearing a coating of a thickness of 120 nm or more. Thus, there might be a moderate oxidation protection of the fibres by the alumina coating.The following statements in the paper cannot be considered true anymore:Page 2014, abstract: The alumina coating improved oxidation resistance of the carbon fiber significantly Page 2020, last paragraph: A comparatively thin layer is already sufficient to delay oxidation significantly Page 2021, conclusions: The coating is efficient in slowing down the oxidation of carbon fibers Fig. 8. Thermogravimetric analysis of coated fibers with various coating thicknesses. The specimens were heated from 30°C to 900°C with a heating rate of 5°C/min and subsequently held at 900°C for 30 min in synthetic air. Oxidation onset temperature increases slightly with increasing coating thickness and levels off for coating thicknesses exceeding approximately 100 nm. 3604
Globalization, the scarcity of resources and climate change constantly raise new questions in the field of production engineering. One promising approach to the challenges involved is to reduce component weight with the aid of lightweight design. The integration of sensors and actuators made of “smart materials” into lightweight composites facilitates enhanced characteristics and functions such as ultra‐lightweight design, superior dynamic properties, and structural health monitoring. This essay presents the strategy adopted by Collaborative Research Center/Transregio 39 “High‐volume compatible production technologies for light metal and fiber composite‐based components with integrated sensors and actuators” (PT‐PIESA) in connection with research and development targeting the acquisition of the requisite scientific fundamentals. It also presents a concept for the holistic analysis of complex process chains for function‐integrated lightweight components with embedded piezoceramic elements.
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