Reaction Of Carbon Fibers Research Articles

One-pot synthesis of carbon fiber/carbon nanotube hybrid using lanthanum (III) chloride for tensile property enhancement of epoxy composites

This study presents a one-pot method for facile synthesis of carbon fiber (CF) / carbon nanotube (CNT) hybrid, which is achieved by the surface reaction of CF and carboxylated carbon nanotubes (CNT-COOH) in the eco-friendly lanthanum (III) chloride (LaCl3)-urea-ethanol solution. The control variate method is utilized to investigate the formation mechanism of the CF/CNT hybrid. Based on the scanning electron microscopy, X-ray powder diffraction, Fourier transform infrared and X-ray photoelectron spectroscopy results, it is found that La (III) coordinates with two or more atoms from different material surface so as to link different material, and urea serves as lone electron pair donor to provide extra binding sites for La (III), then both La (III) and urea play the role of bridge to connect CF and CNT-COOH. The prepared CF/CNT hybrid improves the tensile strength (modulus) of epoxy composites by 59.0% (78.5%), and corresponding improving mechanism has been revealed. The one-pot synthesis of CF/CNT hybrid is convenient, eco-friendly and thus suitable for green industrial application.

Spontaneous formation of multilayer refractory carbide coatings in a molten salt media

Refractory materials hold great promise to develop functional multilayer coating for extreme environments and temperature applications but require high temperature and complex synthesis to overcome their strong atomic bonding and form a multilayer structure. Here, a spontaneous reaction producing sophisticated multilayer refractory carbide coatings on carbon fiber (CF) is reported. This approach utilizes a relatively low-temperature (950 °C) molten-salt process for forming refractory carbides. The reaction of titanium (Ti), chromium (Cr), and CF yields a complex, high-quality multilayer carbide coating composed of 1) Cr carbide (Cr3C2), 2) Ti carbide, and 3) Cr3C2 layers. The layered sequence arises from a difference in metal dissolutions, reactions, and diffusion rates in the salt media. The multilayer-coated CFs act as a permeable oxidation barrier with no crystalline degradation of the CFs after extreme temperature (1,200 °C) and environment (oxyacetylene flame) exposure. The synthesis of high-quality multilayer refractory coating in a fast, efficient, easy, and clean manner may answer the need for industrial applications that develop cheap and reliable extreme environment protection barriers.

Creep Behaviors of 3D C/SiC in High Speed Combustion Gas at 1300°C

To understand the creep damage mechanism of a standard 3D Carbon fiber reinforced silicon carbide composite (C/SiC) in high temperature combustion gas at 1300 °C, the creep tests were carried out in a combustion wind tunnel and the mechanisms were investigated by the extension of specimens and the microstructure of fracture section. It was found that the external tensile load was bore by the carbon fibers in the active region during the stressed oxidation process. The oxidation mechanisms of the active region were determined by a normalized threshold stress. Below the normalized threshold stress, the oxidation was controlled by internal diffusion of oxidizing gases through microcracks in SiC matrix. Above the normalized threshold stress, the oxidation was controlled by the reaction of carbon fiber with oxygen and water vapor.

Synthesis of SiC microtube with villus-like morphology and SiC fiber

Silicon carbide (SiC) microtubes were synthesized and characterized via a vapor–solid (VS) reaction of carbon fiber (Csolid) and SiO(gas). The synthesis mechanisms were investigated. The precursor led complete conversion of [SiO(gas) + C(solid)] into [SiC(solid) + CO(gas)] through overall reaction under inert gas flow at and above 1350 °C. Carbon fibers with small surface area (0.7–2.0 m2 g−1) were gradually converted to SiC microtubes with large specific surface area (45–63 m2 g−1). Inner surface of SiC microtubes indicated a villus-like morphology, which consisted of submicron-sized SiC villi. The outer surface of the SiC microtubes was smooth. Inner surface morphology of SiC microtubes was dependent upon synthesizing temperature. Thickness of villus-like layer in SiC microtubes increased with increasing synthesizing temperature, showing 0.25 and 0.5 at 1350 and 1400 °C, respectively. Both VS and gas–liquid–solid (VLS) growth mechanisms were investigated in synthesis of SiC fiber as a reaction byproduct, and the reaction was governed by both growth mechanisms.

Helical nanocables with SiC core and SiO2 shell

A novel one-dimensional helical nanocable structure has been synthesized through the reaction of carbon fiber with SiO vapor. The crystalline SiC core typically has diameters of 10–20nm with a helical periodicity of 30–40nm and is covered by a uniform layer of 10–20nm thick amorphous SiO2. A growth mechanism is proposed on the basis of difference in the growth rate between crystalline SiC core and amorphous SiO2 shell.

Reaction of carbon fibers with magnesium

1. Carbon fibers in contact with a magnesium-base matrix experience no loss of strength during heating for 100–500 h at temperatures up to 400–450°C. In contrast to the aluminum-carbon-fibers system, 5-min contact with molten magnesium in the temperature range 660–780°C brings about no loss of fiber strength; interaction between the phases in this case is apparently restricted to diffusion across the interfaces. 2. In the temperature range 450–660°C carbon fibers vigorously react with a magnesium-base matrix, as a result of which their strength falls. The loss of strength suffered by carbon fibers during heat treatment for 100 h at 550°C may amount to 60–70% of their starting strength; under these conditions the cross-sectional area of the fibers decreases by 15–20%.