Carbon/carbon composites with heat-treated pitches

Manocha, L.M.; Patel, Mukta; Manocha, S.; Vix‐Guterl, Cathie; Ehrburger, P.

doi:10.1016/s0008-6223(00)00178-0

Cited by 41 publications

(12 citation statements)

References 12 publications

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“…It is accompanied by cross-linking of the hydrocarbons through oxygen molecules, which leads to a reduced level of elemental carbon blow off in the form of hetroatoms. A somewhat similar trend for coal tar based pitch stabilized in air at 350°C was reported by Manocha et al [11]. They found that the TGA bulk yield of the pitch increases up to 5 h stabilization duration and then started decreasing after 5 h, whereas in our case the TGA bulk yield continue to increase with stabilization duration up to 20 h and then only started decreasing after 20 h. The main reason behind the drop in the TGA bulk yield beyond 5 h stabilization, as reported by Manocha et al [11], is the possibility of the reaction of oxygen with carbon leading to removal of elemental carbon.…”

Section: Ftir Spectroscopysupporting

confidence: 86%

“…A somewhat similar trend for coal tar based pitch stabilized in air at 350°C was reported by Manocha et al [11]. They found that the TGA bulk yield of the pitch increases up to 5 h stabilization duration and then started decreasing after 5 h, whereas in our case the TGA bulk yield continue to increase with stabilization duration up to 20 h and then only started decreasing after 20 h. The main reason behind the drop in the TGA bulk yield beyond 5 h stabilization, as reported by Manocha et al [11], is the possibility of the reaction of oxygen with carbon leading to removal of elemental carbon. http://carbonlett.org ing point with OMG is accompanied by structural change of the matrix precursor by the formation of more condensed aromatic units and conversion of lighter fractions of the pitch into heavier fractions [12].…”

Section: Ftir Spectroscopysupporting

confidence: 86%

“…Further, they concluded by citing the diffusion mechanism of oxygen in a solid mesophase pitch artifact. Although oxygen diffusion is an appropriate hypothesis for the varying degree of stabilization with respect to OMG for differ- The low temperature stabilization performed in the present study may be the reason for the increase in the TGA bulk yield of the pitch samples up to stabilization duration of 20 h compared to that of Manocha et al [11]. The severity of the reaction of oxygen with carbon to pluck it out may be greater for shorter duration stabilization at 350°C than longer duration stabilization at 200°C.…”

Section: Ftir Spectroscopymentioning

confidence: 59%

“…Stabilization, as reported in the literature [8][9][10][11][12], is attempted in order to increase the yield of pitches and pitch based matrix precursors by oxygen diffusion and cross linking thereafter. The yield increases with oxygen mass gain (OMG).…”

Section: Characterization Of Sp Samplesmentioning

confidence: 99%

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Yield enhancement of matrix precursor in short carbon fiber reinforced randomly oriented carbon/carbon composite

Raunija¹,

Verma²

2016

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Isroaniso matrix precursor synthesized from commercially available petroleum pitch was stabilized in air. The influence of oxygen mass gain during stabilization on the yield of matrix precursor was studied. Additionally, the influence of pressure on the yield of the stabilized matrix precursor in a real system was studied. The fourier transform infrared spectrometry (FTIR), thermogravimetric analysis (TGA), yield, yield rate, and yield impact were used to check the effect of stabilization and pressure on the yield of the matrix precursor and the end properties of the composite thereafter. The results showed that the yield increased with stabilization duration up to 20 h whereas it decreased for stabilization duration beyond 20 h. Further results showed that the stabilized matrix precursor for a duration of 5 h could withstand almost two-fold greater hot-pressing pressure without resulting in exudation as compared to that of a 1 h stabilized matrix precursor. The enhanced hot-pressing pressure significantly improved the yield of the matrix precursor. As a consequence, the densification and mechanical properties were increased significantly. Further, the matrix precursor stabilized for a duration of 20 h or more failed to provide proper and uniform binding of the reinforcement.

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Section: Ftir Spectroscopysupporting

confidence: 86%

Section: Ftir Spectroscopysupporting

confidence: 86%

Section: Ftir Spectroscopymentioning

confidence: 59%

Section: Characterization Of Sp Samplesmentioning

confidence: 99%

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Yield enhancement of matrix precursor in short carbon fiber reinforced randomly oriented carbon/carbon composite

Raunija¹,

Verma²

2016

Carbon letters

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“…It was shown that the contact angles of the carbon fibers by the pitch that were calculated using wetting data for the model liquids agreed with the directly measured values. Addition of myristic acid equalized the polar and dispersive components of the pitch-melt surface free energy and improved the wettability.Coal-tar pitch is widely used in industry, in particular, as a precursor matrix in carbon materials [1][2][3]. Low porosity that provides high strength and operational characteristics with a low density is one of the key quality indicators of such materials [4,5].…”

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confidence: 99%

Wetting of Carbon Fibers by Coal-Tar Pitch Melts

et al. 2016

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Wetting of carbon fibers by model liquids (water and octane) and melts of pure coal-tar pitch and that with myristic acid added as a surfactant was studied by the Wilhelmy method. It was shown that the contact angles of the carbon fibers by the pitch that were calculated using wetting data for the model liquids agreed with the directly measured values. Addition of myristic acid equalized the polar and dispersive components of the pitch-melt surface free energy and improved the wettability.Coal-tar pitch is widely used in industry, in particular, as a precursor matrix in carbon materials [1][2][3]. Low porosity that provides high strength and operational characteristics with a low density is one of the key quality indicators of such materials [4,5]. The porosity is affected by several factors, including the mass fraction of volatiles (coke residue) and the adhesion of the binder to the reinforcing component. High-quality medium-and high-temperature pitches with low volatiles contents have high coke residues [6]. Drawbacks of them are the high melt viscosity and poor adhesion to fibers.Pitch melts adhere poorly to fibers because of the chemical surface properties of the latter. The polar component is largely responsible for the melt surface free energy; the dispersive, for that of the fiber [7,8]. Recently, surface modification of carbon fibers with functional groups, nanostructures, a variety of finishes, etc. has been studied extensively. These should improve the chemical affinity of the fiber and matrix and provide a stronger interaction [8][9][10]. These approaches with the exception of the finishes are labor intensive if scaled up and give inconsistent results. The affinity of the polymeric matrix and reinforcing component can be increased by adding a suitable surfactant (SA) that improves the wetting without affecting other matrix properties.As a rule, the improvement in the adhesion of the matrix for the reinforcing filler is evaluated by studying the effect of fiber surface treatment on the properties of the obtained material. This is not entirely justified because modification of the fiber involves the complicated action of various factors and can affect its mechanical properties among others. Therefore, the method used to evaluate the effect of fiber modification on its surface chemistry is important. The wetting contact angle in various types of liquid media could be a criterion for the change of fiber surface properties. The goal of the present work was to use the Wilhelmy method to study the wetting of carbon fibers by water, octane, and pitch melts with and without a modifier.Carbon fibers (Zoltek, Hungary) in the finished condition and after heat treatment at 2800°C were studied. Wetting of the fibers by water, octane, high-temperature Bx95KS pitch melt (Rutgers Basic Aromatics GmbH, Germany), and Bx95KS with myristic acid (5 mass%) was studied.The surface free energy (SFE) of the pitch melts and wetting of carbon fibers were determined by the Wilhelmy method on a Sigma 701 tensiometer (Attension, Fi...

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