Pitch-based Carbon Fibers Research Articles

Mesophase Pitch-Based Carbon Fibers: Accelerated Stabilization of Pitch Fibers under Effective Plasma Irradiation-Assisted Modification.

Stabilization is the most complicated and time-consuming step in the manufacture of carbon fibers (CFs), which is important to prepare CFs with high performance. Accelerated stabilization was successfully demonstrated under effective plasma irradiation-assisted modification (PIM) of mesophase pitch fibers (PFs). The results showed that the PIM treatment could obviously introduce more oxygen-containing groups into PFs, which was remarkably efficient in shortening the stabilization time of PFs with a faster stabilization heating rate, as well as in preparing the corresponding CFs with higher performance. The obtained graphitized fiber (GF-5) from the PF-5 under PIM treatment of 5 min presented a higher tensile strength of 2.21 GPa, a higher tensile modulus of 502 GPa, and a higher thermal conductivity of 920 W/m·K compared to other GFs. Therefore, the accelerated stabilization of PFs by PIM treatment is an efficient strategy for developing low-cost pitch-based CFs with high performance.

Pitch-based carbon fibers: preparation and applications

Attention to carbon fiber (CF) conditioned by their unique physicochemical, mechanical and electrical properties, which makes them in demand in various fields of activity. Today there are several kinds of carbon fibers, most of which (about 90%) are made of polyacrylonitrile (PAN). Even though carbon fibers are produced from several types of different precursors, their widespread commercial use is limited by the high cost of the product. Has, many research and engineering groups sought to reduce the cost of production by using cheap carbon raw materials. A likely solution to this problem is the exploitation of coal, petroleum, and coal tar as an effective progenitor for CF production. This review discusses neoteric accomplishment in CF synthesis using various carbon pitches. The possibility of obtaining carbon fibers based on resin with the addition of PAN is presented, and the prospects for their use in energy storage systems and various reinforced composite materials are described in detail.

Effect of heat transfer channels on thermal conductivity of silicon carbide composites reinforced with pitch-based carbon fibers

In this study, silicon carbide (SiC) composites reinforced with pitch-based carbon fibers and composed of heat transfer channels were fabricated by combining chemical vapor infiltration and reactive melting infiltration method. It was observed that the internal heat conduction skeleton of pitch-based carbon fibers was sequentially formed. The thermal conductivities from room temperature to 500 °C along through-thickness direction and in-plane direction were investigated. The results showed that Cpf/SiC composites with heat transfer channels possessed excellent thermal conductvity in two directions, and the thermal conductivity increased with increasing volume content of heat transfer channels. The thermal conductivity in through-thickness direction reached 38.89 W/(m·K), and that for in-plane direction reached 112.42 W/(m·K). Theoretical calculations were empolyed to study the temperature dependence of the Cpf/SiC composites. The variations in slope A′ and intercept B′ values of fitted curves were in good agreement with the experimental results. To verify the reliablilty of the theoretical model, the Cpf/SiC composites were heated at 1650 °C for 2 h and the thermal conductivity exhibited further improvement due to the formation of more perfect crystalline structure. Thermal conductivity through thickness direction improved to 43.49 W/(m·K), and that in in-plane direction improved to 142.49 W/(m·K), which could be identified by the theoretical model. Finally, the leading edge model was established by using ABAQUS finite element analysis software to evaluate the potential application of the composites. Owing to the outstanding thermal conductivity, the leading edge obtained by using Cpf/SiC composites in this study exhibited lower temperature gradient and a more uniform temperature distribution. Moreover, less thermal stress and displacement were generated during heating process.

Microstructure of high thermal conductivity mesophase pitch-based carbon fibers

The microstructural characteristics of high thermal conductivity mesophase pitch-based carbon fibers were investigated by XRD, Raman spectroscopy, SEM and TEM. The relationship between microstructural characteristics and thermal conductivity is discussed. Results show that the radial structure is always accompanied by a splitting structure. La has more significant impact on the thermal conductivity than Lc. The Raman spectroscopy ID/IG value of the cross section was used as an essential index to evaluate the thermal conductivity of the carbon fibers. The microstructural characteristics including large graphite crystallite size, high preferred orientation along the fiber axis, and few defects contribute to the high thermal conductivity of the carbon fibers.

Performance and Cost-Effectiveness of Short Pitch-Based Carbon Fiber Reinforced Mortar Composite.

This paper discusses the performance of the short pitch-based carbon fiber reinforced mortar (CFRM) composite considering its key properties and cost-effectiveness. Five different types of mortar composite were produced using 0–4% volume contents of short pitch-based carbon fibers. The mortar composites were tested for inverted slump cone flow (flow time and volume flow), unit weight, air content, compressive strength, flexural strength, impact resistance, and water absorption. The cost-effectiveness of CFRM was assessed based on the performance to cost ratio (PCR), which was calculated for each mortar composite, considering its workability, mechanical properties, and durability. The inverted slump cone volume flow was counted as a measure of workability, whereas the compressive strength, flexural strength, and impact resistance were considered as the major attributes of the mechanical behavior. In addition, the water absorption was used as a measure of durability. The test results revealed that the mortar composite made with 3% carbon fibers provided adequate workability, a relatively high unit weight and low air content, the highest compressive strength, excellent flexural strength, good impact resistance, and the lowest water absorption. It was also found that the PCR increased up to 3% carbon fibers. Beyond a 3% fiber content, the PCR significantly decreased. The overall research findings revealed that the mortar with 3% carbon fibers was the optimum and most cost-effective mortar composite.

Factors that govern the electric permittivity of carbon materials in the graphite allotrope family

Through comparing carbons in the graphite allotrope family, namely isotropic graphite (IG), exfoliated-graphite-based flexible graphite (FG), graphite-flake thick film (not sintered), carbon fibers (PAN, pitch) and highly-oriented pyrolytic graphite (HOPG), all differing in the microstructure, this work addresses for the first time the factors (including the structure-property relationship) that govern the electric permittivity (kHz frequency) of carbons. The permittivity is more sensitive to the microstructural heterogeneities than the resistivity, which only slightly influences the permittivity. Smaller crystallite dimensions promote the permittivity. PAN-based carbon fibers exhibit higher permittivity than pitch-based carbon fibers, IG, FG or HOPG. The crystallographic preferred orientation is not influential to the permittivity, though it influences the resistivity. Interfaces (e.g., the grain boundaries in IG and the interface between the carbon layer ribbons in a fiber) promote the permittivity, being sites for the carrier-atom interaction that enables the polarization. A large number of sites is more important than a large site size for promoting the permittivity. The fiber diameter is not influential to both permittivity and resistivity. The thick film exhibits the highest relative permittivity (5 × 105), due to its low electrical connectivity. IG (grain size 12 μm) gives the lowest relative permittivity (5 × 102), due to its coarse microstructure.

Absorption and Strength Properties of Short Carbon Fiber Reinforced Mortar Composite

This paper presents the water absorption and strength properties of short carbon fiber reinforced mortar (CFRM) composite. Four CFRM composites with 1%, 2%, 3%, and 4% short pitch-based carbon fibers were produced in this study. Normal Portland cement mortar (NCPM) was also prepared for use as the control mortar. The freshly mixed mortar composites were tested for workability, wet density, and entrapped air content. In addition, the hardened mortar composites were examined for compressive strength, splitting tensile strength, flexural strength, and water absorption at the ages of 7 and 28 days. The effects of different carbon fiber contents on the tested properties were observed. Test results showed that the incorporation of carbon fibers decreased the workability and wet density, but increased the entrapped air content in mortar composite. Most interestingly, the compressive strength of CFRM composite increased up to 3% carbon fiber content and then it declined significantly for 4% fiber content, depending on the workability and compaction of the mortar. In contrast, the splitting tensile strength and flexural strength of the CFRM composite increased for all fiber contents due to the greater cracking resistance and improved bond strength of the carbon fibers in the mortar. The presence of short pitch-based carbon fibers significantly strengthened the mortar by bridging the microcracks, resisting the propagation of these minute cracks, and impeding the growth of macrocracks. Furthermore, the water absorption of CFRM composite decreased up to 3% carbon fiber content and then it increased substantially for 4% fiber content, depending on the entrapped air content of the mortar. The overall test results suggest that the mortar with 3% carbon fibers is the optimum CFRM composite based on the tested properties.

FEM analysis of flexural modulus of carbon fiber monofilament considering anisotropy

Carbon fibers are highly anisotropic materials and it is necessary to understand their mechanical properties in various directions as well as their axial tensile property, for accurate prediction of mechanical properties of carbon fiber reinforced plastics (CFRP). In this study, finite element method (FEM) analysis of three-point bending test of carbon fiber monofilament was carried out on two types of carbon fibers, PAN-based and high modulus pitch-based carbon fibers. The effect of anisotropy of mechanical properties of carbon fibers on flexural modulus was studied by investigating the span length dependence of the flexural modulus obtained by FEM analysis. The experimentally determined elastic parameters, longitudinal tensile, torsional, transverse, and axial compressive moduli, were used as the analysis parameters to consider the anisotropy of carbon fiber in this study. These analyzed results of the dependence of the flexural modulus on the span length showed good agreement with the experimental ones.

Manufacturing Pitch and Polyethylene Blends-Based Fibres as Potential Carbon Fibre Precursors.

The advantage of mesophase pitch-based carbon fibres is their high modulus, but pitch-based carbon fibres and precursors are very brittle. This paper reports the development of a unique manufacturing method using a blend of pitch and linear low-density polyethylene (LLDPE) from which it is possible to obtain precursors that are less brittle than neat pitch fibres. This study reports on the structure and properties of pitch and LLDPE blend precursors with LLDPE content ranging from 5 wt% to 20 wt%. Fibre microstructure was determined using scanning electron microscopy (SEM), which showed a two-phase region having distinct pitch fibre and LLDPE regions. Tensile testing of neat pitch fibres showed low strain to failure (brittle), but as the percentage of LLDPE was increased, the strain to failure and tensile strength both increased by a factor of more than 7. DSC characterisation of the melting/crystallization behaviour of LLDPE showed melting occurred around 120 °C to 124 °C, with crystallization between 99 °C and 103 °C. TGA measurements showed that for 5 wt%, 10 wt% LLDPE thermal stability was excellent to 800 °C. Blend pitch/LLDPE carbon fibres showed reduced brittleness combined with excellent thermal stability, and thus are a candidate as a potential precursor for pitch-based carbon fibre manufacturing.

Self‐damage sensing of electrically conductive self‐compacting concrete incorporating short carbon fibers

This study focused on the incorporation of pitch-based short carbon fibers in the self-compacting concrete (SCC) to obtain electrically conductive carbon fiber-based SCC (CFBSCC) composite. The dispersion of carbon fiber in the SCC was done utilizing a low-speed mechanical churner along with a surfactant. The ultimate goal was to impart the smart properties of carbon fiber into SCC to form electrically conductive CFBSCC which could sense its own stress, strain, or damage without using external sensors thereby developing a self-sensing concrete. The impact of the volume of carbon fibers on the compressive strength and electrical properties for 10 SCC mixes were investigated. The conductive CFBSCC was further investigated for its smart self-sensing behavior by correlating it with the piezoresistive properties. Test results showed that the incorporation of carbon fibers in SCC can improve its compressive strength properties and electrical conducting properties depending upon the percentage of carbon fibers employed. It was also found that the self-sensing ability can be developed in SCC using carbon fibers.

A comprehensive investigation on the chemical structure character of spinnable pitch for improving and optimizing the oxidative stabilization of coal tar pitch-based fiber

Oxidative stabilization is the critical step to maintain the fibrous morphology of pitch fiber and affects mechanical properties of resultant carbon fiber, but the detailed oxidation mechanism is still unclear because of the complex polycyclic aromatic hydrocarbons composition in pitch fiber. In here, pitch fiber was obtained from coal tar pitch followed by air-blowing and spinning. The chemical structure character of corresponding fibers before and after oxidative stabilization at different temperatures (260–320 °C) and durations (2–12 h) were analyzed. The results indicated that aromatic nucleus in spinnable pitch was gradually increased, while aliphatic chains were gradually shorten with prolongation of air-blowing time. The spinnable pitch obtained by air-blowing at 330 °C for 4 h showed excellent spinning performance, and the as-spun pitch fiber displayed a higher oxidative stabilization efficiency because the lower oxygen content was introduced and more C-O-C groups were formed in the resultant oxidative stabilized pitch fiber. The obtained pitch-based carbon fiber, after carbonizing at 1000 °C, showed excellent mechanical properties with tensile strength of 1068.7 ± 100.0 MPa and Young's modulus of 52.5 ± 9.8 GPa. This work provided a facile approach to improve and optimize the oxidative stabilization efficiency for pitch carbon fiber preparation.

Stress graphitization in carbon/carbon composites reinforced with isotropic pitch-based carbon fiber felt

Stress graphitization in carbon/carbon composites reinforced with isotropic pitch-based carbon fiber felt

Process optimization, microstructure characterization and thermal properties of mesophase pitch-based carbon fiber reinforced aluminum matrix composites fabricated by vacuum hot pressing

Continuous mesophase pitch-based carbon fiber (MPCF) reinforced aluminum (Al) matrix composites were fabricated by vacuum hot pressing to meet the requirements of good thermal conductivity (TC), low coefficient of thermal expansion (CTE) and resistance to deformation for thermal management materials. The effect of process parameters on the microstructures and TC of 40 vol % MPCF/Al composites and the influence of MPCF volume fraction on the thermal-mechanical properties of MPCF/Al composites were studied. The results reveal that the composites with 20–50 vol % MPCF fabricated at 650 °C/45 MPa/60 min have longitudinal TC of 230.3–288.3 W/(m⋅K), over 90% of the predictions by rule of mixture, longitudinal CTE of 2.28−-0.22 ppm/K and elastic modulus of 147.5–324 GPa. The interface is mainly composed of an amorphous interface layer of 2–5 nm and a very small amount of carbide crystals. Furthermore, these composites have moderate TC, lower CTE and higher specific modulus compared with other Al matrix composites and Al alloys, which indicates they are expected to become unidirectional thermal management materials with integrated structure and function.

Thermal conductivity enhancement and synergistic heat transfer of z-pin reinforced graphite sheet and carbon fiber hybrid composite

This paper successfully developed a fiber z-pin reinforced graphite sheet (GS) and carbon fiber (CF) hybrid composite laminate. By taking advantages of the superior thermal conductivities of graphite sheet and z-pins, three-dimensional highly conductive paths were constructed to achieve the multifunctions of advanced polymer composites. The effects of ply scheme and z-pin type on the thermal conductivity and heat transfer process of z-pin reinforced GS/CF composites were investigated to reveal the interfacial heat exchange between z-pin and laminas. The results show that both through-thickness and in-plane thermal conductivities are enhanced significantly by implanting through-thickness z-pins in GS/CF composites. This is ascribed to the effective through-thickness conductive paths of z-pins and the synergistic heat transfer of graphite ply and carbon fiber pins. For [GS/CF4/GS]-PAN-pin composite, about 15% laser flash energy transfers through z-pins with a volume fraction of only 2.18%. More obvious heat exchange between z-pins and lamina may be achieved by implanting pitch-based carbon fiber z-pins with higher thermal conductivity and smaller diameter. The resultant through-thickness and in-plane thermal conductivities of [GS/CF4/GS]-pitch-1-pin are measured to be 8.80 W·m−1K−1 and 18.50 W·m−1K−1, which are 13.7 and 8.3 times higher than those of control sample, respectively.

Carbon fiber synthesis from pitch: Insights from ReaxFF based molecular dynamics simulations

Despite the potential to lowering fabrication costs of pitch-based carbon fiber (CF) compared to polyacrylonitrile-based CF, large scale utilization is currently limited by the complexity in manufacturing. This is mainly due to the lack of consistency between the pitch structure/chemistry and CF properties under different processing conditions. Here, we employed full atomistic simulations based on reactive force fields to investigate the conversion of pitch precursors to CFs. It was found that at the carbonization stage, the consumption rates of precursors, gas formations, and solid yields (carbonized CFs) are all dependent on the composition and arrangement of molecular moieties in the precursor. Specifically, precursors with sp3 carbons in the cata-condensed core area have limited decomposition pathways (i.e., limited reaction sites), which leads to the formation of carbonized CFs with similar compositions. Furthermore, carbonized CFs possess distinct structural characteristics, and finally lead to the formation of CFs with different moduli. By analyzing CF crystallinity and elemental composition, general rationales are proposed for the selection of optimal precursors and processing conditions, and thus shed lights on parameter screening during industrial CF synthesis. For instance, inclusion of sp3 carbons in cata-condensed rings can be preferred over the presence of sp3 carbons on side chains.

Remarkably improved interfacial adhesion of pitch-based carbon fiber composites by constructing a synergistic hybrid network at interphase

Ultralow interfacial adhesion of pitch-based carbon fiber composites has always a disturbing problem in reality since the fiber surface is of high graphite degree. Herein, a novel strategy for remarkably increasing the interfacial shear strength (IFSS) of composites via incorporating silane coupling agent (APTES)-polydopamine (PDA) -polyether amine (PEA) ternary organic materials on fiber surface is reported. Due to the solid connection of pitch-based carbon fiber with APTES-PDA-PEA through previous carboxylation and hydroxylation, as well as the increased surface energy and improved wettability, a synergistic hybrid network is formed at the interphase, where various interfacial interactions, including covalent bonding, hydrogen bonding, π-π conjugated bonding and intermolecular entanglement, cooperate with each other. The IFSS of modified fiber composites exhibits an amazing 427.7% increase, much higher than publicly reported pitch-based carbon fiber composites (20.3%~235.1%). The findings in this article offer a unique insight on the design of synergistic hybrid bridging transition strategy addressing the weak interphase in pitch-based carbon fiber composites.

Accurate measurement of pitch-based carbon fiber electrical resistivity

This study investigated the appropriate methodology required to measure single carbon fibers electrical resistivity. Two- and four-probe methods were evaluated for this measurement. Comparing results for single filaments of pitch-based and PAN-based fibers shows that the two-probe method gives acceptable results for PAN-based fibers, but much higher deviations from adjusted resistivity for pitch-based fibers (>15%). The four-probe method shows small deviations (<1%) for both precursors and is the most suitable for measurements of pitch-based carbon fibers. The four-probe method gives higher accuracy than the two-probe for all samples tested.

Stress Graphitization Behavior of c/c Composites Fabricated from Milled Short Pitch-Based Carbon Fibers and their Electrical Properties

Stress Graphitization Behavior of c/c Composites Fabricated from Milled Short Pitch-Based Carbon Fibers and their Electrical Properties

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.