Carbon Fibre Composite Surface Research Articles

Preparation and properties of a simple super‐hydrophobic carbon fiber composite surface

AbstractSuper‐hydrophobic surface is widely used in waterproof, antifouling, and anticorrosion fields because of its unique wetting characteristics. However, the rough structure of super‐hydrophobic surface is easily damaged in service, which leads to the loss of various properties, making it difficult to apply super‐hydrophobic surface on a large scale in actual production. In this paper, epoxy resin was used as adhesive, mixed with hydrophobic silica particles and sprayed on the surface of carbon fiber composites. After curing, the surface of super‐hydrophobic carbon fiber composites with contact angle of 158 ± 2° and sliding angle of 1 ± 0.5° was formed. The surface had excellent dynamic water repellent performance, and the droplets could bounce more than three times on the surface. Furthermore, the super‐hydrophobic surface had excellent wear resistance and mechanical stability. After the friction damage test, the surface structure of the sample was slightly damaged. The amount of wear was small, and the surface was still in super‐hydrophobic state. Through soaked in solutions with different pH values, the microstructure of the surface was not obviously damaged by corrosion, the contact angle of water droplets was greater than 155°. The preparation method of super‐hydrophobic surface of carbon fiber composite proposed in this study is simple and rapid, and the prepared surface has excellent performance, the practical application of super‐hydrophobic surface is promoted.

The Influence of Laser Process Parameters on the Adhesion Strength between Electroless Copper and Carbon Fiber Composites Determined Using Response Surface Methodology.

Laser process technology provides a feasible method for directly manufacturing surface-metallized carbon fiber composites (CFCs); however, the laser's process parameters strongly influence on the adhesion strength between electroless copper and CFCs. Here, a nanosecond ultraviolet laser was used to fabricate electroless copper on the surface of CFCs. In order to achieve good adhesion strength, four key process parameters, namely, the laser power, scanning line interval, scanning speed, and pulse frequency, were optimized experimentally using response surface methodology, and a central composite design was utilized to design the experiments. An analysis of variance was conducted to evaluate the adequacy and significance of the developed regression model. Also, the effect of the process parameters on the adhesion strength was determined. The numerical analysis indicated that the optimized laser power, scanning line interval, scanning speed, and pulse frequency were 5.5 W, 48.2 μm, 834.0 mm/s, and 69.5 kHz, respectively. A validation test confirmed that the predicted results were consistent with the actual values; thus, the developed mathematical model can adequately predict responses within the limits of the laser process parameters being used.

Directing helical CNT into chemically-etched micro-channels on aluminum substrate for strong adhesive bonding with carbon fiber composites

This study presents a simple technique for positioning helical carbon nanotubes (CNTs) into chemically-etched vertical micro-channels on an aluminum (Al) substrate for strong adhesive bonding with carbon fiber composites. Helical CNTs with diameter up to 100 nm and length up to 10 μm were dispersed evenly in an acetone-diluted resin pre-coating (RPC) solution consisting of 90 wt% acetone + 10 wt% resin (without hardener), then applied onto the chemically etched Al substrate with vertical micro-channels. CNTs were dragged into those vertical micro-cavities through the capillary action during the evaporation process of acetone. The shear bond strength was more than doubled by the quasi-Z-directional CNTs, confirming the critical role of CNT bridging across the interface between the epoxy adhesive and Al substrate. Scanned electron microscope (SEM) and focused ion beam (FIB) were used to reveal micro-channels on the Al substrate. RPC on the surface of carbon fiber composites is also beneficial.

Study on cutting performance of diamond-coated rhombic milling cutter in machining carbon fiber composites

The anisotropy characteristic of carbon fiber reinforced plastic (CFRP) easily results in defects such as delamination, tear, and burr in the milling procedure, which seriously restrict its widespread application. Thus this work conducted an experimental research in the cutting performance of the diamond-coated rhombic milling cutter in machining carbon fiber composites. Tool wear procedure and wear mechanism were analyzed, and the variation of both surface quality and cutting force under different tool wear conditions were obtained. It was found that the tool wear process can be divided into two stages, that is, coating wear dominated by abrasive wear and coating shedding by fatigue wear mechanism. In the stage of coating wear, the machined surface of carbon fiber composites was flat and regular, and chips were mainly granular. Whereas in the stage of coating shedding, cutting forces increased substantially; some defects such as stratification, tearing, and fiber pull-out got to occur on the machined surface, and lots of burrs were produced at the edge of machined surface. And here chips were a blend of granular and long-strip ones. The analysis of tool wear mechanism and machined surface morphology in machining carbon fiber composites can provide a significant theoretical reference to improving the machining quality of carbon fiber composites.

Synthetic hydroxyapatite and its use in bioactive coatings.

An approach to solve the limitations of autologous bone grafting procedures in bone injury treatment is to develop bioactive coatings in the implantation system. The objective of this work is to compare the temperature effect on the stability of hydroxyapatite, graphene, and collagen colloidal suspensions to be used as biocompatible and bioactive coatings on a carbon fiber composite surface. Synthesized hydroxyapatite was assessed by X-ray diffraction. Zeta potential at different temperatures was evaluated. Specimens were characterized using scanning electron microscopy and Raman analysis. The results showed that the best hydroxyapatite/graphene ratio was 85/15, while those of the hydroxyapatite/collagen mixtures were 85/15. A hydroxyapatite/graphene/collagen mixture was synthesized based on these results.

Progress in the Development of CFC/CuCrZr Components for HL-2M Divertor

The HL-2M divertor consists of a flat-type carbon fiber composite (CFC)/CuCrZr component and a cassette structure. The CFC/CuCrZr component is made of a water-cooled CuCrZr heat sink armored with carbon CFC tiles. The CFC surface was modified by using Cr slurry to improve its wettability to copper. The Cr layer was deposited by a simple screen-printing technique and then sintered at 1300 °C in a vacuum furnace. An oxygen-free copper (OFC) buffer layer was cast on the modified CFC surface in order to mitigate the internal stresses caused by mismatch in the coefficient of thermal expansion of CFC and CuCrZr. The brazing of the cast OFC/CFC tiles to the CuCrZr heat sink was performed by using a silver-free brazing alloy. Microstructural observations and shear strength tests demonstrate high quality of joining for the CFC/CuCrZr joints. The brazed CFC/CuCrZr mock-up experienced cyclic loading tests of 7 MW/m2 for 1000 cycles with no degradation of heat removal, which meets the requirement of HL-2M divertor.

Microstructure characterization of advanced protective Cr/CrN+a-C:H/a-C:H:Cr multilayer coatings on carbon fibre composite (CFC).

Studies of advanced protective chromium-based coatings on the carbon fibre composite (CFC) were performed. Multidisciplinary examinations were carried out comprising: microstructure transmission electron microscopy (TEM, HREM) studies, micromechanical analysis and wear resistance. Coatings were prepared using a magnetron sputtering technique with application of high-purity chromium and carbon (graphite) targets deposited on the CFC substrate. Selection of the CFC for surface modification in respect to irregularities on the surface making the CFC surface more smooth was performed. Deposited coatings consisted of two parts. The inner part was responsible for the residual stress compensation and cracking initiation as well as resistance at elevated temperatures occurring namely during surgical tools sterilization process. The outer part was responsible for wear resistance properties and biocompatibility. Experimental studies revealed that irregularities on the substrate surface had a negative influence on the crystallites growth direction. Chromium implanted into the a-C:H structure reacted with carbon forming the cubic nanocrystal chromium carbides of the Cr23 C6 type. The cracking was initiated at the coating/substrate interface and the energy of brittle cracking was reduced because of the plastic deformation at each Cr interlayer interface. The wear mechanism and cracking process was described in micro- and nanoscale by means of transmission electron microscope studies. Examined materials of coated CFC type would find applications in advanced surgical tools.

Surface damage characteristics of CFC and tungsten with repetitive ELM-like pulsed plasma irradiation

Surface damage of carbon fiber composite (CFC) and tungsten (W) due to repetitive ELM-like pulsed plasma irradiation has been investigated by using a magnetized coaxial plasma gun. CX2002U CFC and stress-relieved W samples were exposed to repetitive pulsed deuterium plasmas with duration of ∼0.5ms, incident ion energy of ∼30eV, and surface absorbed energy density of ∼0.3–0.7MJ/m2. Bright spots on a CFC surface during pulsed plasma exposures were clearly observed with a high-speed camera, indicating a local surface heating. No melting of a W surface was observed under a single plasma pulse exposure at energy density of ∼0.7MJ/m2, although cracks were formed. Cracking of the W surface grew with repetitive pulsed plasma exposures. Subsequently, the surface melted due to localized heat absorption.

Experimental verification of FOREV-2D simulations for the plasma shield

Analysis of experiments in the MK-200UG facility dedicated to verify the FOREV-2D simulations of ITER core contamination with carbon vaporized during ELMs has been performed. In these experiments the carbon fibre composite (CFC) of NB31 grade have been treated with plasma heat fluxes relevant for ITER ELMs. The analysis revealed that thin layer of few hundred microns on CFC surface is damaged and its thermoconductivity effectively reduced approximately three times, but the CFC bulk has the reference thermoconductivity. Good agreement between the measured and the calculated profiles for carbon plasma electron density at various hydrogen plasma heat loads as well as the agreement between the measured and the simulated dependences of the absorbed energy density on the applied heat load provide reliable validation of the carbon plasma shields simulated with the FOREV-2D code. High carbon plasma shield densities of 10 23–10 24 m −3 predicted in the simulations for ELM-produced shields has been proved in these MK-200UG experiments.

Localization by TEM and EELS of deuterium trapping sites in CFC exposed to plasma irradiation in Tore Supra

Carbon fiber composite (CFC) Sepcarb ® N11 is used in the tokamak Tore Supra as plasma-facing components. To investigate the fuel retention capability of this material, a mobile sample holder was used to expose CFC N11 samples to direct irradiation by the scrape-off layer plasma of Tore Supra at fluences up to 1 × 10 25 m −2. Deuterium (D) elemental mapping using nuclear reaction analysis for the most-exposed CFC sample showed that D retention occurs at depths greater than 8 μm due to the presence of deep (>3.5 μm) local retention sites. In this work, combining transmission electron microscopy (TEM) and electron energy-loss spectroscopy (EELS), we describe at a high spatial resolution where and how D atoms are trapped in these sites. TEM experiments performed on thin cross-sections of the plasma-modified surface show evidence of the presence of a 3.5 μm-thick deuterated amorphous carbon layer deposited on the CFC surface. We show that specific localized retention sites correspond to the filling of relatively large (∼3 μm.) and deep (at least 3 μm below the initial CFC surface) cracks between fibres and matrix by the deuterated amorphous carbon layer.

Saturation in deuterium retention of CFC graphite targets exposed to beryllium-seeded plasmas on PISCES-B

ITER strike-plates are foreseen to be of carbon-fiber-composite (CFC). In this study the CFC bulk deuterium retention in ITER-relevant conditions is investigated. DMS 701 (Dunlop) CFC targets were exposed to plasma in PISCES-B divertor plasma simulator. Samples were exposed to both pure deuterium plasma and beryllium-seeded plasma at high fluences (up to 10 27 m - 2 ) and high surface temperature (1070 K). The deuterium contents of the exposed samples have been measured using both thermal-desorption-spectrometry (TDS) during baking at 1400 K and ion beam nuclear reaction analysis (NRA). The total deuterium inventory has been obtained from TDS while NRA measured the deuterium depth distribution. In the analysed fluence range at target temperature of 1070 K, no fluence dependence was observed. The measured released deuterium is 1.4 × 10 21 m - 2 . In the case of target exposure with beryllium-seeded plasma no change in the released amount of deuterium was found. The deuterium concentration inside the samples is almost constant until the probed depth of ≫ 10 μ m, except in the first 1 μm surface layer, where it is 5 times higher than in the bulk. No C erosion/redeposition was observed in the Be-seeded plasma cases. The measured retention, applied to 50 m 2 of ITER CFC surface, would imply a tritium saturated value of 0.3 gT, much lower than the ITER safety limit of 350 g.

Développement d'une liaison entre une briquette en composite carbone/carbone et une structure de refroidisseur en cuivre

Bonding developpement between a tile made of carbon fibre composite and a copper cooling structure. The bond between a tile made of carbon fibre composite (CFC) and a metallic heat sink is similar to a ceramic/metal bond.It is difficult to perform due to the mismatch between the material expansions, which create high internal stresses. However in the Tore Supra controlled fusion machine (CEA Cadarache, 13108 St Paul Lez Durance, France), this kind of bond, in development since many years, has allowed a 7.6 m 2 toroidal limiter to be achieved, which led to perform CFC/metal bonds for more than 12000 tiles. The used process consists of a geometrical structuring of the CFC surface to be joined, using a laser treatment, which allows a good mechanical coupling of the tile to the brazing material or cast metal.

R&D of the heat-resistant LH antenna

Two different types of Lower Hybrid Current Drive (LHCD) antenna having high-heat resistant property are developed according to a pulse length and/or working frequency. In the first type of LH antenna, heat resistive material is installed at the antenna mouth only and should be attachable using bolts. This heat-resistant mouth is exchanged for a new one when it is damaged. The heat-resistant mouth is made of Carbon Fiber Composite (CFC)-block bonded with stainless steel-base machined to fit the waveguides. This mouth has no Cu-plating for reducing rf-losses, because the antenna is designed to operate during 10–100 s injection of 2 GHz in JT-60SC. The second antenna consists of a compact multi-junction (MJ) part and a power divider designed for the next generation tokamak machine like ITER. This MJ must be made of low-Z material as a plasma facing component allowing no degradation in confinement. The test module for the MJ is made of rods and plates of CFC with Cu-plating ∼30 cm in length. The test module shows transmitted power availability up to 45 MW/m 2 over 1000 s with cooling at 3.7 GHz. For improvement of transmitted power availability, R&D of strong Cu-plating on CFC surface has been progressed using an electrochemical method.

Outgassing of plasma facing antenna front for lower hybrid wave launcher

A 3.7 GHz mock-up antenna module using carbon fiber composite (CFC) was fabricated and tested for the development of a heat-resistive front of the lower hybrid current drive (LHCD) antenna. This module has four waveguides and a water cooling channel, the length is 206 mm. The CFC surface was coated with a thin titanium layer and was plated with copper in order to reduce RF losses, to bond rods and septum plates and to assemble them with cooling channel. The RF losses and the outgassing rates of this CFC module at high RF power were measured during long pulses. When the injected power varies between 30 and 100 kW, the RF losses measured by calorimetery, were found to be in the range of 1.0–1.2%. It is found that this experimental value is 2.5–3.0 times higher than the theoretical value of pure copper. Stationary operation of the CFC module with water cooling is performed at the RF power density of 45 MW m −2 during 1000 s. The outgassing rates from the CFC module are in the range of 0.93∼1.3×10 −6 Pam −3 s −1 m −2 at the module temperature of 120°C, it is low enough for an antenna material. No significant bonding defects occurred during the steady-state operation. It is assessed that a CFC module is an attractive candidate for a heat-resistive front of LHCD antenna.

Development of plasma facing component for LHCD antenna

A mock-up module of an antenna tip made of carbon fiber composite (CFC) was fabricated for the development of a heat-resistive front of the lower hybrid current drive (LHCD) antenna. The CFC surface was coated with a thin Ti layer and was plated with Cu. The mock-up module has three waveguides and is designed to simulate the front tip of the 8 GHz LHCD antenna. The module has an active water cooling channel and the length is 200 mm, the mouth dimension is 19.5×50 mm 2. The mock-up module was tested with heat fluxes up to 20 MW m −2 due to electron beam irradiation. No damage of the waveguide mouth was observed up to the heat flux of 3.2 MW m −2 for 2 min, though a maximum temperature of 762°C was measured at the septum plate. The obtained heat load of 3.2 MW m −2 is about 10 times higher than the steady-state surface-averaged heat load of the first wall required in the ITER design.