Pristine Fibers Research Articles

Innovative fabrication of CNT/SiC composite fibers via impregnation-wet twisting-pyrolysis: Advancements in strength, conductivity, and EMI shielding

Floating catalyst chemical vapor deposition (FCCVD) is a key method for synthesizing high-strength, electrically conductive carbon nanotube (CNT) fibers. However, the high porosity of FCCVD CNT fibers limits the full utilization of the intrinsic performance of CNTs. It remains a challenge to assemble and continuous fabricate high-performance CNT fibers. Herein, this study proposed an impregnation-wet twisting-pyrolysis process to fabricate continuous CNT/SiC composite fibers to enhance the mechanical and electrical properties by reducing pore sizes and improving the interaction between CNTs. The resulting compact structure and enhanced interfacial interactions of the CNT/SiC fibers exhibited both high strength (2015.27 MPa) and high electrical conductivity (7.2 × 105 S/m), representing increases of 130.8 % and 69.9 % compared to pristine CNT fibers. The unidirectional laminates assembled by continuous CNT/SiC fibers demonstrated high electromagnetic interference (EMI) shielding effectiveness of 66.33 dB. This innovative continuous process holds significant potential for the industrial utilization of CNT/SiC fibers.

Mechanical and dielectric properties of SiCf/NBAS composites with dip-coated La2Ti2O7 interphase

To improve the properties of SiC fiber-reinforced ceramic-matrix composites for potential use as radar-absorbing materials, La2Ti2O7 interphase was dip-coated on the surface of the SiC fibers, and the SiCf/NBAS composites were then prepared. The pristine SiC fibers with relatively high electrical resistivity were mainly composed of amorphous SixCyO and a small amount of β-SiC and free carbon. A weak La2Ti2O7 interphase improved the flexural strength and toughness of the composites due to the fiber pull-out and crack deflection. The measured room-temperature complex permittivity of the composites increased, and the dielectric loss was greater than that of the pristine SiC fibers owing to the production of excess free carbon in the degradation of SiC fibers during the preparation of SiCf/NBAS composites. The excess free carbon with higher electrical conductivity was also believed to play a significant part in the increase of dielectric permittivity of the composites with the increasing heat-treatment temperatures even below 1000 °C. A dual-layer structure was designed to expand the bandwidth for microwave absorption.

Effect of material extrusion process parameters on tensile performance of pristine and discontinuous fibre reinforced PLA composites: A review

Effect of material extrusion process parameters on tensile performance of pristine and discontinuous fibre reinforced PLA composites: A review

Surface decoration of Nb2O5 hollow fibers by graphene oxide for enhanced photocatalytic degradation of methylene blue

AbstractThis paper describes the fabrication of ceramic Nb2O5 hollow fibers covered by a thin graphene oxide (GO) layer using the vacuum‐assisted dip‐coating process for the efficient photocatalysis degradation of methylene blue (MB) under UVC light irradiation. Pristine and GO‐coated Nb2O5 hollow fibers were evaluated for photocatalytic degradation at different initial dye concentrations and pH values. A photodegradation of 66.4% of the dye molecules was achieved using the pristine Nb2O5 hollow fibers at 57.4 ± 0.1 mg mL1, initial MB concentration of 10 mg L−1, and pH of 11. Under the same experimental conditions, the GO‐coated Nb2O5 hollow fibers degraded 100% of the MB molecules. Additionally, the GO‐coated Nb2O5 hollow fibers were successfully reused for four reaction cycles and exhibited suitable long‐term stability. Thus, the proposed ceramic Nb2O5 hollow fibers with a surface decorated by a GO layer presented suitable characteristics for use as a photocatalyst in MB degradation.

Tailoring of steel fiber surface by coating cellulose nanocrystal for enhanced flexural properties of UHPC

Ultra-high-performance concrete (UHPC) is an advanced generation of cementitious composites with excellent compressive strength and durability. However, the relatively poor interfacial transition zone (ITZ) between steel fibers and UHPC matrix leads to insufficient flexural properties and hinders its further applications. This study proposed a cost-effective, sustainable, and highly reactive coating material, cellulose nanocrystals (CNCs), to densify the ITZ of steel fiber surfaces, thus enhancing the flexural properties of UHPC. Utilizing the Herschel-Bulkley model, the critical concentration of 1.0 % is determined for enabling uniform dispersion of CNCs, enhancing the coating performance and reliability. The performance of CNCs as coating materials was evaluated by flexural test of UHPC with CNCs-coated steel fibers, pull-off test, scanning electron microscope (SEM), atomic force microscope (AFM), energy-dispersive spectroscopy (EDS), and Fourier-transform infrared spectroscopy (FTIR). Results showed that compared to UHPC with pristine steel fibers, the flexural strength and toughness of UHPC with CNCs-coated steel fibers were increased by up to 14 % and 18 %, because the single fiber pull-off energy was increased by 50 %. It can be attributed to the densified ITZ which is validated by the increased UHD C-S-H and HD C-S-H on ITZ. However, when the concentration of CNCs suspension (i.e., 1.5 %) exceeds the critical value, the CNCs coating film would stick the uniformly dispersed steel fibers together and then affect their distribution, thus reducing the mechanical performance of UHPC. This work provides a green and effective approach for promoting flexural properties and an in-depth understanding of CNCs coating mechanism.

Comparing the effects of pristine and UV–VIS aged microplastics: Behavioural response of model terrestrial and freshwater crustaceans

Physico-chemical properties of microplastics (MPs) change during weathering in the environment. There is a lack of knowledge about the effects of such environmentally relevant MPs on organisms. We investigated: 1) the physico-chemical changes of MPs due to UV–VIS weathering, and 2) compared the effect of pristine and aged MPs on the behaviour of the water flea Daphnia magna and terrestrial crustacean Porcellio scaber. Dry powders of MPs were produced from widely used polymer types: disposable three-layer polypropylene (PP) medical masks (inner, middle and outer), polyester textile fibres, car tires and low-density polyethylene (LDPE) bags and were subjected to accelerated ultraviolet–visible (UV–VIS) ageing. Our results show that the extent of transformation depends on the type of polymer, with PP showing the most changes, followed by LDPE, textile fibres and tire particles. Obvious fragmentation was observed in PP and textile fibres. In the case of PP, but not polyester textile fibres, changes in FTIR spectra and surface properties were observed. Tire particles and LDPE did not change in size, but clear changes were observed in their FTIR spectra. Most MPs, aged and pristine, did not affect the swimming of daphnids. The only effect observed was a significant increase in path length and swimming speed for the pristine tire particles when the recording was done with particles remaining in the wells. After transfer to a clean medium, this effect was no longer present, suggesting a physical rather than chemical effect. Similarly, woodlice showed no significant avoidance response to the MPs tested, although there was a noticeable trend to avoid soils contaminated with pristine polyester textile fibers and preference towards the soils contaminated with aged MP of the middle mask layer. Overall, the apparent changes in physico-chemical properties of MPs after accelerated ageing were not reflected in their effects on woodlice and daphnids.

Integrated process for eco-friendly synthesis and coating of ZrB2 onto carbon fiber substrates

In aerospace engineering, the demand for lightweight materials with superior strength and endurance drives the search for advanced composites. Carbon fiber composites offer exceptional strength-to-weight ratios but are vulnerable to high-temperature oxidation. To address this, protective coatings are crucial. Zirconium diboride (ZrB2) shows promise due to its high melting point and stability but faces challenges in application. Here, we propose a sustainable solution-based method using gum arabic, a natural polysaccharide, as a precursor to coat carbon fibers followed by pyrolysis to form ZrB2. Our technique simplifies production while enhancing coating effectiveness and adhesion. X-ray diffraction and microscopy analyses confirm successful ZrB2 formation and uniform coating. Thermal analysis demonstrates improved oxidative stability compared to pristine carbon fibers. This eco-friendly approach presents a novel avenue for aerospace materials synthesis, offering enhanced performance and sustainability. The study underscores the potential of solution-based techniques and natural precursors in advancing composite materials for extreme environments.

Monolithic Polyepoxide Membranes for Nanofiltration Applications and Sustainable Membrane Manufacture.

The present work details the development of carbon fiber-reinforced epoxy membranes with excellent rejection of small-molecule dyes. It is a proof-of-concept for a more sustainable membrane design incorporating carbon fibers, and their recycling and reuse. 4,4'-methylenebis(cyclohexylamine) (MBCHA) polymerized with either bisphenol-A-diglycidyl ether (BADGE) or tetraphenolethane tetraglycidylether (EPON Resin 1031) in polyethylene glycol (PEG) were used to make monolithic membranes reinforced by nonwoven carbon fibers. Membrane pore sizes were tuned by adjusting the molecular weight of the PEG used in the initial polymerization. Membranes made of BADGE-MBCHA showed rejection of Rose Bengal approaching 100%, while tuning the pore sizes substantially increased the rejection of Methylene Blue from ~65% to nearly 100%. The membrane with the best permselectivity was made of EPON-MBCHA polymerized in PEG 300. It has an average DI flux of 4.48 LMH/bar and an average rejection of 99.6% and 99.8% for Rose Bengal and Methylene Blue dyes, respectively. Degradation in 1.1 M sodium hypochlorite enabled the retrieval of the carbon fiber from the epoxy matrix, suggesting that the monolithic membranes could be recycled to retrieve high-value products rather than downcycled for incineration or used as a lower selectivity membrane. The mechanism for epoxy degradation is hypothesized to be part chemical and part physical due to intense swelling stress leading to erosion that leaves behind undamaged carbon fibers. The retrieved fibers were successfully used to make another membrane exhibiting similar performance to those made with pristine fibers.

Unveiling the Multifunctional Carbon Fiber Structural Battery.

Structural batteries refer to the multifunctional device capable of both storing electrical energy and bearing mechanical loads concurrently. In this context, carbon fibers emerge as a compelling choice of material and serve dual purpose by storing energy and providing stiffness and strength to the battery. Previous investigation has demonstrated proof-of-concept of functional positive electrodes against metallic lithium in structural battery electrolyte. Here, an all-carbon fiber-based structural battery is demonstrated utilizing the pristine carbon fiber as negative electrode, lithium iron phosphate (LFP)-coated carbon fiber as positive electrode, and a thin cellulose separator. All components are embedded in structural battery electrolyte and cured to provide rigidity to the battery. The energy density of structural battery is enhanced by use of the thin separator. The structural battery composite demonstrates an energy density of 30Whkg-1 and cyclic stability up to 1000 cycles with ≈100% of Coulombic efficiency. Remarkably, the elastic modulus of the all-fiber structural battery exceeds 76GPa when tested in parallel to the fiber direction - by far highest till date reported in the literature. Structural batteries have immediate implication in replacing structural parts of electric vehicles while reducing the number of conventional batteries. Thus, offering mass savings to future electric vehicles.

Development of Bromine Adsorbing Carbon Felt Electrode by Coating of Nitrogen-Doped Mesoporous Carbon Layer for Highly Stable Flowless Zinc-Bromine Battery

Renewable energy is well known for the extreme volatility of power production, and secondary battery-based energy storage systems (BESS) are the key to the novel and safe energy industry to expand the supply of renewable energy. Currently, lithium-ion battery-based ESS is commonly used, but the frequent ignition accidents from these ESSs rather become an obstacle to the growth of the renewable energy field. Among the redox batteries, the flowless zinc-bromine battery (FLZBB) is studied as the alternative since it uses a non-flammable and cost-effective aqueous Zn- Br2 electrolyte. However, its main challenges are that bromine (Br2) and polybromide anions (), formed at the positive electrode during the charging process, cross over to the negative electrode due to the difference in chemical potential between the electrodes. The diffused Br2 oxidizes the zinc metal, electrodeposited on the negative electrode, and causes a self-discharge reaction that consumes the charging active material and Br2 the battery performance and life. Herein, we present a nitrogen-doped mesoporous carbon coated on the pristine graphite felt fibers (NMC/GF). By uniformly forming a nitrogen-doped porous carbon material on the GF fibers through the evaporation-induced self-assembly (EISA) method, it is a simple and cost-effective method to develop the structural and properties of the GF positive electrode to increase the ability of adsorption and storing the active materials, Br2 and polybromide anions (,, and ) generated during the charging process. In addition, it also improved the bromine redox reaction kinetics by having a strong affinity with the aqueous Zn-Br2 electrolyte. This facilitates long-term charge/discharge cycles, enabling high performance and improved durability for Coulombic efficiency over 95% for 5000 cycles in the FLZBB single-cell platform at a current density of 20 mA cm-2 and a high-rate areal capacity of 2 mAh cm-2.

Gamma‐ray‐induced modification of poly(ethylene terephthalate) and polypropylene solid materials with halogen‐containing olefins for X‐ray CT image contrast enhancement

AbstractIt is known that X‐ray CT of organic polymer materials usually provides low‐contrast images because of the low X‐ray absorption of these materials. In this paper, we describe a new method to enhance the contrast of X‐ray CT images of organic polymer materials. We demonstrate that gamma‐ray irradiation of poly (ethylene terephthalate) (PET) fibers in dichloromethane containing 2‐bromoethyl methacrylate, 2‐chloroethyl methacrylate, or 4‐bromostyrene results in the grafting of halogen‐containing oligomeric chains onto the PET fibers. Focused ion beam scanning electron microscopy (FIB‐SEM) and time‐of‐flight secondary ion mass spectrometry (TOF‐SIMS) analyses revealed a homogeneous distribution of bromine atoms within the 2‐bromoethyl methacrylate‐modified PET fibers, not only on the surface. This uniform incorporation translated to a significant improvement in X‐ray CT image contrast compared with pristine fibers. Similar treatment of polypropylene pellets also enhanced the contrast of their X‐ray CT images. This is a new simple and effective method to enhance the X‐ray CT image contrast and potentially applicable to various polymer materials including polymer composites and porous polymer materials, readily allowing the observation of their 3D microstructures finely.

Comparative degradation behavior of polybutylene succinate (PBS), used PBS, and PBS/Polyhydroxyalkanoates (PHA) blend fibers in compost and marine–sediment interfaces

Amid increasing concerns over microplastic pollution and the persistence of nonbiodegradable polymers in the ocean, this study evaluates the biodegradability of polybutylene succinate (PBS)-based fishing gear under different conditions: pristine PBS fibers, PBS fibers utilized in fishing (PBS_used), and PBS fibers blended with 10% polyhydroxyalkanoate (PHA). By simulating compost and marine–sediment interface environments with reference to ISO 14855 and ISO 19679 standards, respectively, we aimed not only to assess the degradation performance of these fibers but also to examine the physical and chemical property changes pre and postdegradation. PBS, PBS_used, and PBS/PHA (9:1) fibers exhibited degradation rates of 31.9%, 35.5%, and 39.5% in compost environments, and 20.3%, 22.1%, and 25.9% at the seawater–sediment interface, respectively. Through comprehensive physicochemical analyses involving molecular weight measurement, field emission–scanning electron microscope, Fourier transform infrared spectroscopy, tensile property evaluation, and thermogravimetric analysis, the degradation behavior of PBS-based fibers depending on the degradation environment was compared. This study suggests that PBS-based fishing gear can biodegrade under various conditions encountered in the actual fishing sector, thereby preventing ghost fishing and mitigating the issue of abandoned, lost, or otherwise discarded fishing gear.

Thermal energy storage performance of liquid polyethylene glycol in core–shell polycarbonate and reduced graphene oxide fibers

Thermal energy storage is a promising, sustainable solution for challenging energy management issues. We deploy the fabrication of the reduced graphene oxide (rGO)–polycarbonate (PC) as shell and polyethylene glycol (PEG) as core to obtain hydrophobic phase change electrospun core–shell fiber system for low-temperature thermal management application. The encapsulation ratio of PEG is controlled by controlling the core flow rate, and ~ 93% heat energy storage efficacy is apparent for 1.5 mlh−1 of core flow rate. Moreover, the prepared fiber possesses maximum latent melting and freezing enthalpy of 30.1 ± 3.7 and 25.6 ± 4.0 Jg−1, respectively. The transient dynamic temperature vs. time curve of the rGO-loaded phase change fiber demonstrates the delay of fiber surface temperature change compared to pristine fiber. We indeed show that the tunable heat transfer and thermal energy storage efficacy of phase change fiber is achieved via controlled liquid PEG delivery and the addition of rGO in shell architecture. Notably, the effectiveness of unique phase change material (PCM)–based core–shell fibers is concluded from advanced scanning thermal microscopy (SThM) and self-thermoregulation tests.

Structural Positive Electrodes Engineered for Multifunctionality.

Multifunctional structural batteries are of high and emerging interest in a wide variety of high-strength and lightweight applications. Structural batteries typically use pristine carbon fiber as the negative electrode, functionalized carbon fiber as the positive electrode, and a mechanically robust lithium-ion transporting electrolyte. However, electrochemical cycling of carbon fibre-based positive electrodes is still limited to tests in liquid electrolytes, which does not allow for to introduction of multifunctionality in real terms. To overcome these limitations, structural batteries with a structural battery electrolyte (SBE) are developed. This approach offers massless energy storage. The electrodes are manufactured using economically friendly, abundant, cheap, and non-toxic iron-based materials like olivine LiFePO4. Reduced graphene oxide, renowned for its high surface area and electrical conductivity, is incorporated to enhance the ion transport mechanism. Furthermore, a vacuum-infused solid-liquid electrolyte is cured to bolster the mechanical strength of the carbon fibers and provide a medium for lithium-ion migration. Electrophoretic deposition is selected as a green process to manufacture the structural positive electrodes with homogeneous mass loading. A specific capacity of 112mAhg-1 can be reached at C/20, allowing the smooth transport of Li-ion in the presence of SBE. The modulus of positive electrodes exceeded 80GPa. Structural battery-positive half-cells are demonstrated across various mass-loadings, enabling them to be tailored for a diverse array of applications in consumer technology, electric vehicles, and aerospace sectors.

Self-Poled Piezoelectric Nanocomposite Fiber Sensors for Wireless Monitoring of Physiological Signals.

Self-powered sensors have the potential to enable real-time health monitoring without contributing to the ever-growing demand for energy. Piezoelectric nanogenerators (PENGs) respond to mechanical deformations to produce electrical signals, imparting a sensing capability without external power sources. Textiles conform to the human body and serve as an interactive biomechanical energy harvesting and sensing medium without compromising comfort. However, the textile-based PENG fabrication process is complex and lacks scalability, making these devices impractical for mass production. Here, we demonstrate the fabrication of a long-length PENG fiber compatible with industrial-scale manufacturing. The thermal drawing process enables the one-step fabrication of self-poled MoS2-poly(vinylidene fluoride) (PVDF) nanocomposite fiber devices integrated with electrodes. Heat and stress during thermal drawing and MoS2 nanoparticle addition facilitate interfacial polarization and dielectric modulation to enhance the output performance. The fibers show a 57 and 70% increase in the output voltage and current compared to the pristine PVDF fiber, respectively, at a considerably low MoS2 loading of 3 wt %. The low Young's modulus of the outer cladding ensures an effective stress transfer to the piezocomposite domain and allows minute motion detection. The flexible fibers demonstrate wireless, self-powered physiological sensing and biomotion analysis capability. The study aims to guide the large-scale production of highly sensitive integrated fibers to enable textile-based and plug-and-play wearable sensors.

Carbon Dot Synthesis in CYTOP Optical Fiber Using IR Femtosecond Laser Direct Writing and Its Luminescence Properties.

Luminescent carbon dots (CDs) were locally synthesized in the core of CYTOP fibers using IR femtosecond laser direct writing (FLDW), a one-step simple method serving as a post-treatment of the pristine fiber. This approach enables the creation of several types of modifications such as ellipsoid voids. The CDs and photoluminescence (PL) distribute at the periphery of the voids. The PL spectral properties were studied through the excitation/emission matrix in the visible range and excitation/emission spectra in the UV/visible range. Our findings reveal the presence of at least three distinct luminescent species, facilitating a broad excitation range extending from UV to green, and light emission spanning from blue to red. The average laser power and dose influence the quantity and ratio of these luminescent CD species. Additionally, we measured the spatially resolved lifetime of the luminescence during and after the irradiation. We found longer lifetimes at the periphery of the laser-induced modified regions and shorter ones closer to the center, with a dominant lifetime ~2 ns. Notably, unlike many other luminophores, these laser-induced CDs are insensitive to oxygen, enhancing their potential for display or data storage applications.

Application of multi-layered composite fiber films with enhanced piezoelectric performance in flexible energy harvesting devices

Flexible electronic components such as wearable sensors, energy harvesting devices, and human health monitoring systems based on piezoelectric materials have garnered significant attention within the scientific community. In this study, PZT nanofibers were modified with dopamine hydrochloride prior to their integration into PVDF fibers, serving as piezoelectric reinforcements to enhance the mechanical and piezoelectric characteristics of composite fiber films. Subsequently, a facile hot-pressing method was employed to fabricate multilayered films characterized by a densely packed surface fiber arrangement and a loosely organized internal fiber orientation, which markedly improved the self-supporting ability and fiber density of the electrospun fiber films. A detailed investigation into the micro-morphology, crystallinity, and enhanced piezoelectric properties of the films was conducted. Notably, the composite fiber film containing 6 wt% PZT NFs exhibited a peak piezoelectric coefficient (d33) of 29 pC/N, resulting in an output voltage of 13.8 V. This represents a 2.23-fold enhancement in d33 value and a 4.6-fold increase in output voltage when compared to the pristine PVDF fiber film, which had a d33 of 13 pC/N and an output voltage of 3 V. The power density achieved by the sensor is 0.73 μW/cm2. This performance is underpinned by a high piezoelectric coefficient, outstanding output characteristics, and robust stability, which collectively enhance the sensor's efficacy in various applications. This research presents an effective approach for augmenting the piezoelectric performance of PVDF-based composite films and paves the way for the advancement of piezoelectric energy harvesting applications.

Production and characterization of bacterial cellulose by Rhizobium sp. isolated from bean root

Bacterial cellulose (BC) is a natural polymer renowned for its unique physicochemical and mechanical attributes, including notable water-holding capacity, crystallinity, and a pristine fiber network structure. While BC has broad applications spanning agriculture, industry, and medicine, its industrial utilization is hindered by production costs and yield limitations. In this study, Rhizobium sp. was isolated from bean roots and systematically assessed for BC synthesis under optimal conditions, with a comparative analysis against BC produced by Komagataeibacter hansenii. The study revealed that Rhizobium sp. exhibited optimal BC synthesis when supplied with a 1.5% glucose carbon source and a 0.15% yeast extract nitrogen source. Under static conditions at 30 °C and pH 6.5, the most favorable conditions for growth and BC production (2.5 g/L) were identified. Modifications were introduced using nisin to enhance BC properties, and the resulting BC-nisin composites were comprehensively characterized through various techniques, including FE-SEM, FTIR, porosity, swelling, filtration, and antibacterial activity assessments. The results demonstrated that BC produced by Rhizobium sp. displayed properties comparable to K. hansenii-produced BC. Furthermore, the BC-nisin composites exhibited remarkable inhibitory activity against Escherichia coli and Pseudomonas aeruginosa. This study contributes valuable insights into BC’s production, modification, and characterization utilizing Rhizobium sp., highlighting the exceptional properties that render it efficacious across diverse applications.

Unlocking the superior flexibility and enhanced catalytic oxidation performance of CoTiO3 nanofibrous membranes through zirconium doping

The development of continuous CoTiO3 (CTO) fibers with prominent catalytic oxidation activity, tunable fibrous structures, and improved recyclability is appealing for application in efficient organic wastewater treatment; however, inescapable flaws remain, such as their inherent brittleness and adverse operability. Herein, a facile and effective strategy is proposed for the fabrication of flexible and mechanically robust CTO nanofibrous membranes through a combination of element doping and sol–gel-assisted electrospinning. Compared with pristine CTO fibers, the resulting zirconium-doped CoTiO3 (ZCTO) nanofibrous membranes displayed remarkably enhanced flexibility and tensile mechanics, which were attributed to their lower crystallinity, smaller grain size, and fewer fiber surface defects. The developed ZCTO fibrous membrane demonstrated exceptional resistance to bending fatigue, retaining a polymer-like bending rigidity of approximately 25 mN even after undergoing 200 reciprocating bending cycles. Furthermore, the incorporation of zirconium into CTO clearly had an advantageous effect on the formation of oxygen vacancies, thereby enhancing the surface adsorption of peroxymonosulfate (PMS), accelerating the electron transfer process, and weakening the peroxy bonds. The tetracycline degradation efficiency of the ZCTO fibers remained at 81.4% within 10 min after 5 continuous cycles. Benefiting from their robust mechanical properties and excellent catalytic activity, the fabricated membranes demonstrated outstanding dynamic catalytic performance under gravity-driven conditions. More importantly, the reported strategy might be adopted and extended to develop a wide range of ceramic fibers with enhanced flexibility and mechanics for catalytic oxidation.

Assessment of the anisotropy development of mechanical properties of pitch-based carbon fibers

Carbon fiber XN-P9 derived from anisotropic pitch was heat treated at different temperatures (2000, 2500, and 3000℃) and the mechanical properties of those single filament in various directions were tested with some methods we have developed. The anisotropy of the mechanical properties of those pitch-based carbon fibers was evaluated to be developed by heat treatment. As a comparison, the properties of carbon fiber XN-05 derived from isotropic pitch were also tested. The ratio of the longitudinal tensile modulus to the shear modulus of XN-05 fiber was approximately 3. In contrast, for pristine XN-P9 fiber, the longitudinal tensile modulus was more than nine times greater than the shear modulus, and the difference between these moduli increased with the elevating heat treatment temperatures. It was suggested that the anisotropy of mechanical properties of pitch-based carbon fibers was developed by heat treatment. In compressive deformation in the transverse direction to the fiber axis, a yielding and a softening was clearly observed with the elevating heat treatment temperature. The effect of anisotropy development on the span-length dependence of flexural modulus obtained from the three-point bending test of the single filament was assessed.