Pitch-based Carbon Fibers Research Articles

Accelerating the oxidative stabilization of pitch fibers and improving the physical performance of carbon fibers by modifying naphthalene-based mesophase pitch with C9 resin

A spinnable mesophase pitch with 95 vol.% optical anisotropy and 267 °C softening point was prepared through co-polymerization of 95 wt.% naphthalene pitch and 5 wt.% C9 resin. The effects of introducing C9 resin on the formation, structure and properties of naphthalene-derived mesophase pitch and the oxidative stabilization of resulting pitch fibers as well as the final physical properties of carbon fibers were systematically investigated. The results suggest that C9 resin could effectively facilitate the generation and development of liquid crystals in synthetic naphthalene pitch during the heat soaking process and introduce a certain amount of methyl side chains linking in polycyclic aromatic hydrocarbon molecules, so as to reduce the melt viscosity of modified mesophase pitch and improve its flow-spinnability and oxidative reaction capability. The pre-oxidation process of the modified pitch-spun fibers could be completed ahead of 4 h at 240 °C in an air atmosphere, compared with unmodified pitch fibers. This shows a possibility to decrease the production cost of mesophase pitch-based carbon fibers. Although the tensile strength of 1000 °C carbonized fibers prepared from the modified mesophase pitch (1.23 GPa) is slightly higher than that of original carbon fibers (1.18 GPa), the axial electrical resistivity and the thermal conductivity of corresponding graphite fibers after 3000 °C graphitization are 2.0 μΩ m and 677 W/(m K), respectively, which are significantly enhanced in comparison with those of original graphite fibers (3.2 μΩ m and 473 W/(m K).

Interfacial shear strength and interaction between polycarbonate and reinforcement fibers

We aim to investigate the ordered polycarbonate (PC) structure around a reinforcement fiber and the interfacial properties of the interaction between PC and the reinforcement fiber. Pitch-based carbon fiber (piCF) and E-glass fiber (GF) were used as reinforcement fibers. From the results of the present Raman analysis of PC/piCF and PC/GF composite, we concluded that the interaction of the phenyl ring (π electrons) between PC and piCF is attributed to the formation of the ordered structure of PC at the piCF surface. In the case of the PC/GF composite, neither the interaction nor the formation of the ordered structure of PC is identified. It is confirmed that the interfacial shear strength of PC/piCF is higher than that of PC/GF. It is concluded that the interaction of π electrons between PC and piCF affects the interfacial shear strength.

Carbon Fibers with High Electrical Conductivity: Laser Irradiation of Mesophase Pitch Filaments Obtains High Graphitization Degree

Carbon fibers have promising applications in the efficient transmission of electric power with less resource consumption. Laser graphitization of the mesophase pitch-based carbon fiber (MPCF) was p...

Investigations on the effect of plasma treatment on the adhesive bonding behavior of ultra high modulus K13C2U/cyanate ester fiber composites

Surface preparation of ultra-high modulus fiber composites for adhesive bonding is challenging due to the subsurface damages that can occur during a standard abrasion operation that could weaken the laminate cohesion. Therefore, it is highly desirable to utilize a non-contact method that can clean and activate the composite surface without exerting an external force to eliminate potential damage. This investigation focuses on the use of atmospheric plasma treatment (APT) for the surface preparation of unidirectional ultra-high modulus, composites for adhesive bonding. The laminates were manufactured using Mitsubishi K13C2U pitch-based carbon fiber with Tencate’s RS-3C cyanate-ester resin and bonded with Henkel 9394 epoxy. Surface analysis of plasma-treated samples revealed a significant reduction of surface contamination and increased chemical modification of the matrix material resulting in improved wetting and the formation of chemical groups conducive to bonding. The plasma treatment also produced a minor increase in surface roughening, well below levels expected to contribute to mechanical interlocking. APT epoxy-bonded lap-shear specimens (LSS) exhibited a 50% increase in strength as compared to mechanically abraded samples. It was also shown that solvent rinsing after APT removed a highly-oxidized, poorly bonded carbonate component from the treated resin surface as evidenced by XPS. This surface ash is observed at fairly high concentrations after APT of cyanate ester resin composites limiting functional group contributions. The removal of this ash resulted in increases in LSS of 25% as compared to unrinsed APT surfaces. Lap shear strengths and GIC delamination resistance tests showed improvements over abrasion surface treated samples. Image analysis of the fracture faces for both surface treatments showed that abrasion treated surfaces resulted in sub-surface damage to the fibers that translated into brittle fracture through weak, highly aligned layers within these graphitic fibers. On the other hand, plasma treatment was successfully applied to minimize subsurface damage and resulted in crack propagation along with the more tortuous fiber-matrix interface. The degree of the improvements was ultimately limited by the interlaminar strength of these composites.

Experimental investigation on mechanical properties of carbon fiber reinforced aluminum metal matrix composite

Many research works were carried out in the field of material science; these researches show that the composite materials are better than the conventional materials due to their enhanced mechanical properties. The recent manufacturing trends, aluminium based composite materials are popular in most of the application like automotive, aircraft, military, and others. The carbon fiber reinforced aluminum metal matrix composites are highly potential materials for aerospace and electronic industries. In the present work, an open die casting method is used to fabricate the AA 6061 based composite material. The AA 6061 is used as a base metal, and the uncoated continuous long spool-type pitch-based carbon fibers are used as reinforcement. The carbon fibers were placed in the format with two-levels of weight percentage 5% and 10%; the carbon fibers were reinforced with a certain distance with AA6061 aluminium alloy; the composite is fabricated with the help of an electric furnace. The composite's mechanical properties were studied by the various mechanical tests and they were compared with the base alloy of AA 6061. The morphological characteristic was studied by the SEM images, which exhibit the uniform distribution of carbon fibers in the composite material.

Effect of initial density on thermal conductivity of new micro‐pipeline heat conduction C/SiC composites

AbstractC/SiC composites prepared by chemical vapor infiltration technique (CVI) have been regarded as thermal structural materials widely. However, these composites still suffer from poor functional properties like low thermal conductivity, especially in thickness direction of the composites, limiting their large‐scale applications. Herein, mesophase pitch based carbon fiber (MPCF) and continuous wave laser machining were utilized to construct highly effective heat conductive micro‐pipelines within CVI C/SiC composite. The effect of initial density on the final density and thermal conductivity of the as‐obtained MPCF‐C/SiC composites were investigated. The results revealed that higher initial density would directly enhance the thermal conductivity and reduce the negative impact of the bottle‐neck effect. At temperatures between 100°C and 500°C, MPCF‐C/SiC composites preserved more than threefold of the thermal conductivity (340%) when compared to reference C/SiC composites. This work provides a highly effective route for enhancing the thermal conductivity of C/SiC, which would broaden their future applications.

Quasi-isotropic fiber metal laminate with high specific modulus and near-zero coefficient of thermal expansion

On the basis of lamination theory, a quasi-isotropic fiber metal laminate (FML) with a near-zero coefficient of thermal expansion (CTE) and high specific modulus was designed, using pitch-based carbon fiber reinforced plastic (CFRP) prepreg and stainless steel (SST). The SST to CFRP thickness ratio was determined so that the laminates had an exact-zero CTE at room temperature (25 °C). The CTE of a fabricated FML was accurately measured using embedded fiber Bragg grating (FBG) sensors, to verify that the CTE had a near-zero value around room temperature. The temperature dependence of the FML CTE from 20 to 120 °C was investigated via finite element analysis (FEA) taking the temperature-dependent material properties into account. It was demonstrated from the experiment and FEA that the present FML had a near-zero CTE around room temperature (20–45 °C) and a higher Young's modulus and specific modulus compared with other relevant materials.

Preparation, microstructure and properties of three-dimensional carbon/carbon composites withhigh thermal conductivity

Three-dimensional (3D) carbon/carbon(C/C) composites with high thermal conductivity were prepared from a preform prepared by orthogonallyweaving continuous mesophase pitch-based fibers in the x and y directions andcommercial PAN-based carbon fibers in the z-direction, which were densified by three cycles of chemical vapor infiltration(CVI) and graphitization to a density of 1.58 g/cm3 (3CVI), followed by four cycles of liquid pressure impregnation (LPI), carbonization and graphitization to give a density of 1.84 g/cm3 (3CVI+4LPI). The effects of the microstructure and the relative contributionsof the fibers and matrix carbon to the thermal conductivity and mechanical properties of the C/C composites were investigated. Results indicate that the CVI pyrolytic carbon (PyC) is highly crystalline and oriented along the fiber axis. Thethermal conductivities of the 3CVI and 3CVI+4LPI C/C composites in the x-y plane are respectively 115.9and 234.7W/m·K, while those in the z-direction are only 18.6 and 41.5 W/m·K. The thermal diffusivity and thermal conductivity mainly depend on the fiber type, the volume fractions of the fibers and the type of pyrolytic carbon. The thermal conductivity of the composites is improved by increasing the volume fraction of pitch-based carbon fibers and using matrix carbon that is easily graphitized. The mechanical properties of the two C/C composites are greatly improved compared with those of 1D-C/C and 2D-C/C composites.

Remarkable promotion effect of 2,3-Dimethyl-2,3-diphenylbutane on the oxidation stabilization of coal tar pitch

Oxidation stabilization is an extremely important step for maintaining microstructure as well as boosting performance of pitch-based carbon fibers, carbon/carbon composites, etc. However, the low reactivity of pitch molecules with oxygen and the sluggish diffusion kinetics of oxygen seriously hinder the oxidation process, leading to tremendous consumption on energy and time thereby. To overcome the problem, a novel free-radical-induced oxidation strategy is proposed through the modification of raw pitch with 2,3-Dimethyl-2,3-diphenylbutane (DMDPB). The strategy allows oxidation stabilization of pitch not relying solely on oxygen diffusion and self-reactivity of pitch molecules, but also on the substantial free radicals generated from thermolabile covalent bonds of DMDPB. Particularly, the free radical concentration of the modified pitch with 10 wt.% DMDPB reaches almost 2.2 times than that of raw pitch. Consequently, the crosslinking reactions between pitch molecules are homogeneously promoted and their average molecular weight, softening point, and carbon yields are also elevated significantly. The induced reaction mechanism of DMDPB and its synergistic reaction mechanism with oxygen have also been investigated explicitly. The rapid homogeneous stabilization approach has been applied in the preparation of carbon fiber (with a diameter of ~ 18 μm) and spherical activated carbon (with a diameter of ~ 600 μm), offering an attractive perspective on low-cost preparation of pitch-based carbon materials.

Constructing the Bridge from Isotropic to Anisotropic Pitches for Preparing Pitch-Based Carbon Fibers with Tunable Structures and Properties.

Synthetic naphthalene pitches (SNPs) with isotropy and anisotropy were prepared by a simple thermal polycondensation method to fabricate pitch-based carbon fibers. The structural characteristic, thermal stability, phase-separation behavior, and melt-spinnability of the SNPs and the structural properties of the derived carbon fibers were systematically investigated. The results show that spinnable SNPs with controllable mesophase contents ranging from 0 to 100 vol % and softening points (210–290 °C) could be easily obtained by a nitrogen-bubbling treatment to improve their thermal stability and melt-spinnability by avoiding the phase separation of liquid crystal (LC) in the pitch. An experimental phase diagram of spinnability and mesophase content is newly proposed for predicting the spinnability of a mesophase-containing pitch. The LC has a significant influence not only on the constituents, structure, and physical properties of the SNPs but also on the final structure and properties of the corresponding pitch-based carbon fibers. The low ash content (less than 0.15 wt %) in the pitch precursor is found to have no obvious effect on the pitch spinnability and the mechanical properties of derivative large-diameter carbon fibers.

Structural Design of Hybrid CFRP Using Pitch-Based and PAN-Based Carbon Fibers and Their Mechanical Properties

Structural Design of Hybrid CFRP Using Pitch-Based and PAN-Based Carbon Fibers and Their Mechanical Properties

Preparation of Copper-coated Mesophase Pitch-based Carbon Fibers by Electroless Plating Technique with the APTES Grafting Modification

An upgrade synthesis method of electroless copper plating was developed to prepare the copper-coated mesophase pitch-based carbon fibers (Cu@CF) with APTES (3-Aminopropyl triethoxysilane) grafting modification. The microstructure and properties of the fibers which were prepared by the APTES sensitization method were investigated and compared with those prepared by the conventional SnCl2 sensitization method. The results showed that as-coated fibers sensitized by APTES demonstrated to have better interfacial cohesion between the copper layer and the fiber surface than those sensitized by SnCl2 did. Moreover, the resistivity of Cu@CF-APTES declined to 2.3±0.9 µΩ·cm, while that of Cu@CF-SnCl2 was 9.3±3.7 µΩ·cm. Besides, not only the strength of Cu@CF-APTES increased, but the strength discreteness of them reduced due to the fact that no peeling phenomenon was observed between the copper layer and fiber during the stretch test.

Discovering Biomass Structural Determinants Defining the Properties of Plant-Derived Renewable Carbon Fiber

SummaryTraditional lignocellulosic feedstock research has focused on biomass characteristics essential for improving saccharification efficiency, yet the key biomass features underlying high-quality renewable lignin materials remain unknown. Nevertheless, modern biorefinery cannot achieve sustainability and cost-effectiveness unless the lignin stream can be valorized. We hereby addressed these scientific gaps by investigating biomass characteristics defining lignin-based carbon materials properties. Lignin from eight sorghum samples with diverse characteristics was fabricated into carbon fibers (CFs). Remarkably, only lignin uniformity was found to define CF mechanical performance, highlighting the new structure-property relationship. Contrarily, lignin content and composition did not impact on carbon material properties. Mechanistic study by XRD and Raman spectroscopy revealed that higher lignin uniformity enhanced CF microstructures, in particular, turbostratic carbon content. The study for the first time highlighted lignin uniformity as an important biomass structure determinant for renewable products, which opened up new avenues for feedstock design toward diverse products enabling sustainable and cost-effective bioeconomy.

Observation of Distribution of π-Orbital-Oriented Domains in PAN- and Pitch-Based Carbon Fibers Using Scanning Transmission X-ray Microscopy

The mechanical properties of carbon fibers (CFs) can be controlled by their internal structures such as the distribution of π-orbital-oriented domains, as well as the diameter and cross-sectional shape of the fiber. In this study, we investigated the carbon chemical structure maps of commercial polyacrylonitrile (PAN)- and pitch-based CFs using scanning transmission X-ray microscopy to evaluate the differences in the distribution of π-orbital-oriented domains. The graphene sheets in the PAN-based CFs have a fiber texture that is aligned along the fiber direction and randomly oriented within the cross section. The domain sizes within the cross section are less than the resolution limit (i.e., 50 nm). By contrast, the graphene sheets in the pitch-based CFs are aligned parallel to each other and form aggregates with a size ranging from approximately 100 nm to 1 μm within the cross sections. They form 200–300-nm stripes along the CF axis in the longitudinal sections.

Adverse effect of mesophase pitch draw-down ratio on carbon fiber strength

The adverse effect of draw-down ratio (DDR) during melt-spinning of mesophase pitch on resulting properties of carbon fibers (CFs) is reported. Precursor fibers were obtained using spinneret capillaries of various diameters. For CFs with equivalent diameters (ranging between 8 and 13 μm), the tensile strength of CFs increased from 1.4 to 2.3 GPa as the DDR of precursor fibers decreased from 189 to 14. This is contrary to that observed for CFs derived from polyacrylonitrile precursor, where strength increases with increasing precursor fiber DDR. Raman spectroscopy revealed an inverse relationship between pitch fiber DDR and CF coherence length (increase from 58 to 85 nm when DDR decreased from 189 to 14). Further, x-ray diffraction results confirm a larger CF crystalline orientation with decreasing DDR. Thus, a smaller DDR during mesophase spinning could facilitate intra-crystalline graphitic-plane orientation and decrease defects in the inter-crystalline regions along fiber axis in resulting CFs, leading to increased strength (a defect-controlled property). Thus, while it is generally known that tensile strength increases with decreasing CF diameter, for mesophase pitch-based carbon fibers this relationship is not fully valid if the diameter reduction is obtained by merely increasing the draw-down ratio of precursor fibers during melt-spinning.

Development of UHTCMCs via water based ZrB2 powder slurry infiltration and polymer infiltration and pyrolysis

Cf/ZrB2-SiC ultra-high temperature composites were manufactured via aqueous slurry impregnation coupled with polymer infiltration and pyrolysis, using a allylhydrido polycarbosilane precursor. For the first time we used ultra-high modulus pitch-based carbon fibres for the PIP process, investigating three different architectures, 0/0°, 0/90°, and 2D. Microstructure, mechanical properties and oxidation resistance in air at 1650 °C were investigated. As expected, the mechanical properties showed the tendency to decrease with increase of the preforms complexity, due to the higher amount of flaws and residual stresses. For instance, the flexural strength was approaching 500 MPa for 0/0°, 370 MPa for 0/90° and 190 MPa for 2D. The materials showed an optimal resistance to oxidation at 1650 °C thanks to formation of a viscous borosilicate glass that guaranteed a self-healing functionality.

Effect of PAN-based and pitch-based carbon fibres on microstructure and properties of continuous Cf/ZrB2-SiC UHTCMCs

In this paper the microstructure and mechanical properties of two different Cf/ZrB2-SiC composites reinforced with continuous PyC coated PAN-derived fibres or uncoated pitch-derived fibres were compared.Pitch-derived carbon fibres showed a lower degree of reaction with the matrix phase during sintering compared to PyC/PAN-derived fibres. The reason lies in the different microstructure of the carbon. The presence of a coating for PAN-derived fibres was found to be essential to limit the reaction at the fibre/matrix interface during SPS. However, coated bundles were more difficult to infiltrate, resulting in a less homogeneous microstructure.As far as the mechanical properties are concerned, specimens reinforced with coated PAN-derived fibres provided higher strengths and damage tolerance than uncoated pitch-derived fibres, due to the higher degree of fibre pull-out. On the other hand, the weaker fibre/matrix interface resulted in lower interlaminar shear, off-axis strength and ablation resistance.

Synergistic Effects of Hybrid Carbonaceous Fillers of Carbon Fibers and Reduced Graphene Oxides on Enhanced Heat-Dissipation Capability of Polymer Composites.

In this study, we investigated the synergistic effects of thermally conductive hybrid carbonaceous fillers of mesophase pitch-based carbon fibers (MPCFs) and reduced graphene oxides (rGOs) on the thermal conductivity of polymer matrix composites. Micro-sized MPCFs with different lengths (50 μm, 200 μm, and 6 mm) and nano-sized rGOs were used as the thermally conductive fillers used for the preparation of the heat-dissipation polymer composites. For all MPCF fillers with a different length, the thermal conductivity values of the MPCF/epoxy composites were proportional to the MPCF length and loading amount (0–50 wt%) of MPCFs. For an MPCF:rGO weight ratio of 49:1 (total loading amount of 50 wt%), the thermal conductivity values of MPCF-rGO/epoxy composites loaded with MPCFs of 50 μm, 200 μm, and 6 mm increased from 5.56 to 7.98 W/mK (approximately 44% increase), from 7.36 to 9.80 W/mK (approximately 33% increase), and from 11.53 to 12.58 W/mK (approximately 9% increase) compared to the MPCF/epoxy composites, respectively, indicating the synergistic effect on the thermal conductivity enhancement. The rGOs in the MPCF-rGO/epoxy composites acted as thermal bridges between neighboring MPCFs, resulting in the formation of effective heat transfer pathways. In contrast, the MPCF-rGO/epoxy composites with MPCF:rGO weight ratios of 48:2 and 47:3 decreased the synergistic effect more significantly compared to rGO content of 1 wt%, which is associated with the agglomeration of rGO nanoparticles. The synergistic effect was inversely proportional to the MPCF length. A theoretical approach, the modified Mori-Tanaka model, was used to estimate the thermal conductivity values of the MPCF-rGO/epoxy composites, which were in agreement with the experimentally measured values for MPCF-rGO/epoxy composites loaded with short MPCF lengths of 50 and 200 μm.

Effective thermal conductivity of 3D-printed continuous fiber polymer composites

3D printing, especially fused filament fabrication, presents a potentially attractive manufacturing technique for thermal applications such as polymer heat exchangers due to the ability to create complex internal geometries which can be used to enhance convective heat transfer. Recently, commercial and modified open-source printers have utilized continuous fibers such as carbon fiber to create continuous fiber reinforced polymer composites (FRPCs) which enhance the mechanical properties of the printed products. This continuous filler network can also serve to improve thermal conductivity. In this study, the effective thermal conductivity of 3D-printed FRPCs is characterized using a steady-state, modified, guarded hot plate apparatus. The effect of the fiber direction and volume fraction on the effective thermal conductivity of the 3D-printed composites was characterized experimentally and modeled analytically using series and parallel models. Thermal conductivities of up to 2.97 W/mK were measured for samples in which the fibers were aligned with the direction of heat flow. Measured values were in good agreement with analytical model predictions. The importance of fiber conductivity on overall performance of the FRPCs was further demonstrated using a handlaid-up, pitch-based carbon fiber sample which exhibited an effective thermal conductivity of 23.6 W/mK.

Mechanical anisotropy of PAN-based and pitch-based carbon fibers

Mechanical anisotropy of PAN-based and pitch-based carbon fibers