Pitch-based Carbon Fibers Research Articles

Stress analysis and fracture toughness of notched polyacrylonitrile (PAN)-based and pitch-based single carbon fibers

The stress analysis and fracture toughness of high tensile strength polyacrylonitrile (PAN)-based (T1000GB, IMS60, and T300), high modulus PAN-based (M60JB), high modulus pitch-based (K13D), and high ductility pitch-based (XN-05) single carbon fibers were investigated using notched specimens and a focused ion beam. The maximum stress of T1000GB, IMS60, T300, M60JB, K13D, and XN-05 single fibers was calculated as 30.5, 29.4, 25.6, 44.3, 68.6, and 15.5 GPa, respectively. The critical stress intensity factor of T1000GB, IMS60, T300, M60JB, K13D, and XN-05 single carbon fibers was calculated as 1.91, 1.82, 1.67, 3.09, 4.84, and 1.02 MPa m1/2, respectively. The critical energy release rate of T1000GB, IMS60, T300, M60JB, K13D, and XN-05 single carbon fibers was calculated as 478, 502, 763, 3064, 13266, and 237 J/m2, respectively. These results indicate that a linear relationship exists between the fracture toughness (critical stress intensity factor and critical energy release rate) and tensile modulus and maximum stress. The results indicate that the maximum stress is an effective parameter for evaluating the fracture toughness of PAN-based and pitch-based single carbon fibers.

Effects of stabilization variables on mechanical properties of isotropic pitch based carbon fibers

Optimization of the stabilization process for manufacturing low-cost carbon fibers was performed. By simply varying both heating rate (0.5–10°C/min) and starting temperature (25–230°C), the resulting fibers possessed different properties such as densities, oxygen contents, and weight gains due to the oxygen up-takes. Subsequent oxidative reactions led to changes in chemical compositions of the fibers. Therefore, this study suggests that more concerned design with complementary parameters such as starting temperature and heating rate, significantly reducing stabilization time down to 56.5min with the comparable mechanical properties of the conventional isotropic pitch based CFs.

研究と研究者 : ピッチ系炭素繊維の開発( 社会を支える化学)

研究と研究者 : ピッチ系炭素繊維の開発( 社会を支える化学)

Meltblown Solvated Mesophase Pitch-Based Carbon Fibers: Fiber Evolution and Characteristics

Potentially low-cost continuous carbon fibers are produced from solvated mesophase pitch through a patented meltblowing process. The structural evolution and properties of the fibers are characterized by various analytical methods. The meltblown fibers are continuous fibers which are collected into a fibrous web form, and the diameter of the filaments is attenuated by the flow rate of air streams. The spun fibers can be rapidly stabilized in air due to the high melting mesogens and the removable solvent. The carbonized fibers show a high carbon yield of 75 wt % (or 86 wt % if the solvents are neglected) and a mean diameter of 8–22 μm with typical fiber diameter distribution and variation. The evolution of the fiber structure depends not only on the processing temperature but also on the fiber diameter. The processed carbon fibers retain the same form as the spun fibers and have a low packing density and reasonable mechanical properties.

Thermal conductivity and mechanical properties of pitch-based carbon fibre reinforced aluminium composites fabricated by squeeze casting

Pure aluminium and high-silicon aluminium alloy were reinforced with the discontinuous pitch-based carbon fibres by squeeze casting, then the thermal conductivity and the mechanical properties of the composites were investigated. Optical microscopy revealed that the fibres were in a random planar arrangement, and the transmission electron microscopy revealed that there is no interfacial reaction between the matrices and the fibres. The random planar arrangement of the fibres leads to the anisotropy of the composite. The fibre-reinforcement increased the thermal conductivity in the parallel direction for both pure aluminium and its alloy matrices, while the thermal conductivity decreased in the vertical direction. The increase in the elastic modulus by the reinforcement was not observed for both matrices. The proof stress of the pure aluminium increased by the reinforcement especially in the parallel direction, while that of the high-silicon alloy decreased by the reinforcement.

Measurement method of multi scale thermal deformation inhomogeneity in CFRP using in situ FE-SEM observations

The measurement of nano scale thermal deformation and strain inhomogeneity in the transverse direction in carbon fiber-reinformed polmer (CFRP) in the temperature range 170–370K has been carried out by in-situ Field Emission Scanning Electron Microscopy (FE-SEM) observation using a heating and cooling stage in the FE-SEM chamber. A grid pattern and also random patterns were drawn on the polished sample surface at different length scales. The electron moiré method was applied to measure the macroscopic deformation and the digital imaging correlation method was applied to measure the nano-scale deformation around the fiber/matrix interface. The strain inhomogeneity of the pitch-based carbon fiber in the transverse direction and the debonding at the interface between fiber and matrix has been evaluated quantitatively.

Activated carbon–carbon composites made of pitch-based carbon fibers and phenolic resin for use of adsorbents

Activated carbon–carbon composites (ACCC) were prepared from low-cost, nonwoven like, continuous mesophase pitch-based carbon fibers and phenolic resin. The carbon fiber/phenolic resin composite was first fabricated by using a vacuum bagging resin infusion technique. The composite was carbonized in N2 at 1050 °C and then activated with CO2/H2O at 850 °C for about 5 h to obtain an ACCC. Optical microscope and SEM observations reveal that tiny cracks and channels are formed in the entire carbonized material due to the carbonization/shrinkage of the matrix, which are beneficial for the activation of carbon materials within the composite. After activation, the ACCC has a specific surface area of 800 m2/g and a resistivity of 470 μΩ m. Mini filters assembled with the ACCC is permeable and has high contact efficiency with the methylene blue in the breakthrough test. Gas adsorption experiments show that the ACCC material has a good adsorption performance for a variety of volatile organic compounds at room temperature. The prepared ACCC is expected not only to be used as an adsorbent but also as potential for use as an electrode material.

Investigation of the degradation of pitch-based carbon fibers properties upon insufficient or excess thermal treatment

To overcome the disadvantages of discontinuous conventional batch extruders, a continuous screw extruder is introduced to manufacture pitch-based carbon fibers. For a carbon fiber preparation process, an oxidation time of 8 h was determined to be optimal for obtaining desirable mechanical properties of the fibers acquiring employing the screw extruder. It is hypothesized that the differences in the properties of the carbon fibers fabricated utilizing the batch and screw extruders originate from the melt spinning time; therefore, a combined equation for the total amount of heat treatment from the pitch precursor through the oxidation process is established in this study. The crystallinity of the carbon fibers is confirmed to correspond to the differences in mechanical properties as the oxidation time increases. The poor mechanical properties of the carbon fibers that are insufficiently oxidized are a result of irregular oxidation from the sheath to the core of the fiber cross section. However, the over-oxidized carbon fibers also show poor mechanical properties than the optimal fibers. This result further affirms that excessive oxidation times cause unstable chemical bonding, which interrupts the formation of stable crystal structures after carbonization.

Mechanical and electrical properties of cement paste incorporated with pitch-based carbon fiber

The compressive strength and electrical resistance of pitch-based carbon fiber (CF) in cementitious materials are explored to determine the feasibility of its use as a functional material in construction. The most widely used CFs are manufactured from polyacrylonitrile (PAN-based CF). Alternatively, short CFs are obtained in an economical way using pitch as a precursor in a melt-blown process (pitch-based CF), which is cheaper and more eco-friendly method because this pitch-based CF is basically recycled from petroleum residue. In the construction field, PAN-based CFs in the form of fabric are used for rehabilitation purposes to reinforce concrete slabs and piers because of their high mechanical properties. However, studies have revealed that construction materials with pitch-based CF are not popular. This study explores the compressive strength and electrical resistances of a cement paste prism using pitch-based CF.

Enhanced thermal conductivity for mesophase pitch-based carbon fiber/modified boron nitride/epoxy composites

Carbon fiber reinforced epoxy composites are of great interest in advanced components which require light weight and high thermal conductivity (TC). However, the epoxy-rich interlayer makes even highly thermal conductive mesophase pitch-based carbon fibers (MPCF) less effective in the out-of-plane direction. In this study, boron nitride (BN) particles are incorporated in MPCF/epoxy composites with 20% volume fraction to study the enhancement of TC (TCE) for the composites. After an efficient surface treatment by coupling agent KH550 for BN particles, TC of composite has achieved 7.9 W/(mK) which is higher than that without surface treatment (4.4 W/(mK)). Such a high TCE is attributed to the reinforced adhesion among modified BN (mBN), epoxy matrix and the prepreg of MPCF achieved by silanol groups of KH550 which enable to not only reduce the thermal resistance but also increase efficient packing between fillers and the polymer matrix. Besides, TC of composites with mBN also shows good stability during the process of temperatures increasing.

Surface treatments of solvated mesophase pitch-based carbon fibers

The effects of oxidation treatments and surface coating on the surface properties of the solvated mesophase pitch-based carbon fiber (CF) are investigated to improve the mechanical properties of the potentially low-cost CF composites. The CFs were treated with air, O3, CO2/H2O, or HNO3 solution or modified with an epoxy coating. The surface of the treated fibers was characterized by adsorption of methylene blue, NaOH uptake, fragmentation test, composite flexural test, and optical microscopy and SEM examination. Gaseous oxidization is considered a suitable and economical process for this potentially low-cost and low packing density CFs. O3 oxidation is more effective than other oxidation treatments and introduces more acidic functional groups and a suitable surface area on the surface of the treated CFs, leading to a shorter fiber critical length and higher interfacial shear strength between the CF and the epoxy resin. Surface coating in 5 wt% of epoxy/acetone solution also effectively reduces fiber critical length due to improved fiber surface wettability. After surface treatment, the CFs can be directly fabricated into composite materials without weaving and knitting. Increased flexural strength and modulus of the composites are achieved by the use of O3-oxidized fibers and fiber surface coatings. Optical microscopy and SEM confirm that the composites fabricated with the surface-treated fibers have less debonded area or voids than the untreated ones.

Thermal expansion behaviour of squeeze-cast aluminium matrix composites reinforced with PAN- and Pitch-based carbon fibres

Aluminium composites reinforced with the PAN- and pitch-based short carbon fibres were fabricated by squeeze casting, then the thermal expansion behaviour of the composites was investigated. Optical microscopy revealed that the fibres were in a random arrangement on the plane parallel to the pressed plane during the melt infiltration process. TEM observation and hardness test revealed that the PAN-based fibre bonds strongly with the aluminium matrix while the pitch-based fibre bonds poorly. The difference in the bonding strength affected the thermal strain response; the heating and cooling curve approximately traced the same paths during the heating-cooling cycles for the PAN-based fibre composite, while the curve did not trace the same path for the pitch-based fibre composite. The fibre-reinforcement decreased the coefficient of the thermal expansion (CTE) of matrices in the direction parallel to the pressed plane. For example, the CTE of the pure aluminium and its composite at 333 K were 23.0 and 19.0 × 10−6/K, respectively.

Solvated mesophase pitch-based carbon fibers: thermal-oxidative stabilization of the spun fiber

Potentially low-cost, continuous carbon fiber (CF) was prepared by meltblown spinning of solvated mesophase pitch, followed by drying, oxidation and carbonization. The drying and oxidation stabilization of the spun fiber was investigated by thermal analysis to understand the thermal behavior of the fiber and to improve the mechanical properties of the resulting CFs. The solvents in the spun fiber can be almost completely removed by heating the fiber in the flowing N2 or argon. In contrast, less amounts of solvents were removed as the spun fiber was dried in air because some solvents could be oxidized and/or trapped by the oxidized pitch materials. The separate drying and oxidation processes not only remove solvents effectively, but also promote oxidation stabilization. Thin fiber gains more weight (oxygen uptake) than the thick fiber at the same stabilization conditions. Moisture is easily adsorbed onto the stabilized fibers due to the formation of oxygen-containing groups. The moisture uptake increases proportionally with oxidation time. As compared with simultaneous drying and oxidation in air, the separate drying and oxidation processes provide the prepared CF with a significant improvement in tensile strength and modulus. For larger diameter fibers, the optimum oxidation condition is 350 °C for 30–60 min; for smaller diameter fibers, it is only about 2 min. Due to shorter oxidation time, higher carbon yield is achieved in resulting CFs.

Transverse compressive properties of polyacrylonitrile (PAN)-based and pitch-based single carbon fibers

In this study, transverse compressive properties of high tensile strength polyacrylonitrile (PAN)-based (T1000GB), high modulus PAN-based (M60JB), high modulus pitch-based (K13D), and high ductility pitch-based (XN-05) single carbon fibers were measured using a direct compression test. The transverse compressive modulus, Ef (TC), of T1000GB, M60JB, K13D, and XN-05 single fibers corresponded to 8.94 GPa, 3.30 GPa, 1.44 GPa, and 17.49 GPa, respectively. The transverse compressive strengths, σf (TC), of T1000GB, M60JB, K13D, and XN-05 single fibers corresponded to 0.894 GPa, 0.999 GPa, 0.037 GPa, and 1.438 GPa, respectively. The results indicate that the high ductility pitch-based, the high strength PAN-based, and the high modulus PAN-based single carbon fibers possess high compressive modulus and strength. In contrast, the high modulus pitch-based single carbon fiber possess low compressive strength and modulus. Statistical distributions of transverse compressive strength were characterized. The Weibull modulus for T1000GB, M60JB, K13D, and XN-05 single fibers corresponded to 6.86, 7.57, 9.72, and 5.41, respectively. The result indicate that the structure/microstructure parameters are clearly correlated with transverse compressive properties of PAN-based and pitch-based single carbon fibers and especially with the transverse compressive modulus/strength and the Weibull modulus of transverse compressive strength.

Improving the performance of microbial fuel cells by reducing the inherent resistivity of carbon fiber brush anodes

Abstract This study investigated the effect of carbon fibers as brush anode materials on the performance of microbial fuel cells (MFCs). Two types of carbon fibers with different electrical resistivity and functionality – polyacrylonitrile (PAN) ( ρ : 28.0 μΩ m) and pitch ( ρ : 2.05 μΩ m) were investigated. X-ray photoelectron spectroscopy analysis showed that the PAN- and pitch-based carbon fibers presented almost the same surface elements and functional groups, and there was no significant difference in microbial growth on the brush anodes. Current interrupt and steady discharging methods demonstrated the pitch-based carbon brush anodes had lower ohmic resistance and generated higher power density. After nitric acid treatment, the power density generated by the PAN- and pitch-based anodes increased by 29.3% and 26.7%, achieving 816 and 895 mW m −2 , respectively. Using pitch-based carbon fiber brush as anode attained better performance than the widely used PAN-based carbon brush. The acid treated pitch-based carbon fibers provide a promising alternative to highly efficient anode materials for the extensive application of MFCs.

Effect of carbonization temperature on crystalline structure and properties of isotropic pitch-based carbon fiber

carbonized at temperatures ranging from 800 to 1600oC to investigate their crystalline structure and physical properties as a function of the carbonization temperature. The in-plane crystallite size (La) of the carbonized pitch fiber from X-ray diffraction increased monotonously by increasing the ca...

Effect of carbon fiber crystallite size on the formation of hafnium carbide coating and the mechanism of the reaction of hafnium with carbon fibers

The effect of carbon source crystallite size on the formation of hafnium carbide (HfC) coating was investigated via direct reaction of hafnium powders with mesophase pitch-based carbon fibers (CFs) heat-treated at various temperatures. X-ray diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy analyses reveal that uniform and dense HfC coatings are preferentially formed on CFs containing larger and more ordered graphite crystallites. The carbide synthesis temperature and the sizes of crystallites in the CFs have a remarkable influence on the integrity and thickness of the coatings. The formation the HfC coatings can be attributed to the surface diffusion of hafnium and the bi-directional diffusion of hafnium and carbon sources inside the HfC coating. The reaction of HfC coated carbon fibers with zirconium powders leads to the growth of ZrC on the HfC coating and this has been shown to occur by the diffusion of carbon from the carbon fiber core through the carbide coating to its surface.

Tensile Strength of Cement Mortar using Pitch-based Carbon Fiber Derived from Oil Residues

Tensile Strength of Cement Mortar using Pitch-based Carbon Fiber Derived from Oil Residues

Mechanical Properties of Aluminum Composites Reinforced with PAN- and Pitch-Based Short Carbon Fibers

Mechanical Properties of Aluminum Composites Reinforced with PAN- and Pitch-Based Short Carbon Fibers

ロックインサーモグラフィ式周期加熱法による炭素系複合材料の面内方向熱拡散率測定（界面熱抵抗の影響と熱拡散モデルによる検証）

Measurement of thermal conductivity for anisotropic material is difficult or troublesome for conventional measurement techniques. Then periodic heating method using lock-in thermography was proposed as a convenient measurement technique. In this paper, thermal diffusivity distribution of pitch based carbon fiber reinforced plastics (CFRP) was measured by periodic heating method using lock-in thermography. The results showed that thermal diffusivity of several CFRPs depend on heating frequency. Then CFRPs were made using autoclave in various conditions and thermal diffusivities were measured. The results showed that thickness directional thermal diffusivities of CFRPs which were made at low pressurization are smaller than that of CFRPs which were made at standard pressurization, and in-plane thermal diffusivities of CFRPs which were made at low pressurization depend on heating frequency. It means that thermal contact resistance between prepregs causes heating frequency dependencies. Next, numerical model for pitch based CFRP was constructed using control volume method, and parametric study about thermal contact resistance was carried out in order to find the cause of heating frequency dependencies. Numerical results supported the results of experimental study.