Two-dimensional Fiber Research Articles

Three-dimensional carbon nanofiber networks encapsulated in cobalt–molybdenum metal clusters on nitrogen-doped carbon as ultra-efficient electrocatalysts for hydrogen evolution reactions

Efficient and cost-effective catalysts have been developed for the production of hydrogen via water electrolysis. In this study, we develop a strategy for the fabrication of carbon nanofiber catalysts loaded with CoMo clusters covered by a nitrogen-doped carbon network (CoMo/CN@CNFs/MEL). The surface of two-dimensional carbon fibers was coated with a nitrogen-doped carbon network via melamine pyrolysis, thereby forming three-dimensional (3D) networks. These 3D network catalysts exhibited excellent catalytic performance in the hydrogen evolution reaction with 1 M KOH, requiring an overpotential of only 148 mV to reach a current density of 10 mA cm−2 owing to synergistic effects resulting from their structure and composition. The catalytic performance of the CoMo/CN@CNFs/MEL catalysts was comparable to that of commercial Pt/C at high current densities owing to their unique structural features, including restricted Co–Mo clusters, porous nitrogen-doped carbon frameworks, continuous conducting carbon nanofibers, and carbon nitride networks. This work provides a promising approach to transition metal-based catalysts with improved stability and atom utilization efficiency.

Single-core multi-channel moiré fiber grating and multi-wavelength LMA fiber grating fabricated based on two-dimensional spatially encoded phase mask

A two-dimensional optical fiber grating with multi sub-gratings based on a 2D spatially encoded phase mask is designed in this study. The 2D fiber Bragg grating (FBG) is composed of two non-overlapping sub-FBGs, which are laterally separated along the radial direction of the fiber core. Unlike traditional FBGs, the refractive index of the 2D FBG is modulated both on the axial and radial directions of the fiber core, which are realized by spatially encoded diffraction based on a 2D spatially encoded phase mask. Compared with the overlapping grating, the 2D FBG can be fabricated at one time to achieve multi-wavelength output, and its compact structure provides a new idea for multi-wavelength multiplexing. As examples, a single-core multi-channel moiré fiber grating and 2D FBG with three subgratings are designed and fabricated on a single-mode fiber and LMA fiber, respectively. Using a 2D spatially encoded mask can improve the optical fiber refractive index modulation from one- to two- or even three-dimensions, which is helpful for precise manipulation of the complex optical field of optical fiber.

Investigations on the influence of the boundary conditions when computing the effective crack energy of random heterogeneous materials using fast marching methods

Recent stochastic homogenization results for the Francfort–Marigo model of brittle fracture under anti-plane shear indicate the existence of a representative volume element. This homogenization result includes a cell formula which relies on Dirichlet boundary conditions. For other material classes, the boundary conditions do not effect the effective properties upon the infinite volume limit but may have a strong influence on the necessary size of the computational domain. We investigate the influence of the boundary conditions on the effective crack energy evaluated on microstructure cells of finite size. For periodic boundary conditions recent computational methods based on FFT-based solvers exploiting the minimum cut/maximum flow duality are available. In this work, we provide a different approach based on fast marching algorithms which enables a liberal choice of the boundary conditions in the 2D case. We conduct representative volume element studies for two-dimensional fiber reinforced composite structures with tough inclusions, comparing Dirichlet with periodic boundary conditions.

Two-dimensional Fe3O4-MnO2 hollow fiber ceramic membrane for hybrid catalytic ozonation-membrane filtration process for TCH degradation

In this work, a novel 2D Fe3O4-MnO2 hollow fiber ceramic membrane (HFCM) with both excellent separation performance and high catalytic activity was constructed. The Fe3O4 nanoparticles were deposited on 2D MnO2 nanoplates to increase the Mn3+ content, and then the nanoplates were pressure-driven and sintered on the surface of the hollow fiber ceramic supports to obtain 2D Fe3O4-MnO2-HFCMs. Electron spin resonance analysis confirmed that hydroxyl radicals and superoxide radicals played a major role in oxidative degradation and tetracycline hydrochloride (TCH) removal was 86.9 %. Noteworthily, TCH was concentrated on the membrane interface due to the concentration polarization effect, which increases the probability of binding free radicals from the catalytic membrane layer, thus enhancing the catalytic performance and the anti-fouling capability of the membrane. The 2D Fe3O4-MnO2-HFCM can be applied in wastewater treatment due to its superior catalytic ozonation activity and high separation performance.

Microstructure and mechanical properties of three-dimensional oxide/oxide composite fabricated by a slurry infiltration and sintering process

Oxide/oxide composites reinforced by two-dimensional fiber fabrics are important structural materials at high temperatures but exhibit low delamination resistance. This study developed a simple slurry infiltration and sintering (SIS) process to fabricate three-dimensional oxide/oxide composites. The results showed that a homogeneous microstructure in three directions was obtained. This composite possessed a weak matrix, which had a porous structure and low elastic modulus. Typical mechanical properties of the composite were not lower than those of two-dimensional oxide/oxide composites since the flexural strength and fracture toughness were 332.4 MPa and 11.6 MPa·m1/2, respectively. Particularly, the composite had a good interlaminar shear strength of 25.4 MPa and a superior transthickness tensile strength of 5.6 MPa. X-ray computed tomography showed that fiber yarns in the through-thickness direction effectively impeded crack propagation and enhanced delamination resistance. Therefore, the reported SIS process is a very promising method for manufacturing three-dimensional oxide/oxide composites.

Fabrication of Multilayered Two-Dimensional Micelles and Fibers by Controlled Self-Assembly of Rod-Coil Block Copolymers.

Fabricating hierarchical nanomaterials by self-assembly of rod-coil block copolymers attracts great interest. However, the key factors that affect the formation of the hierarchical nanomaterials have not been thoroughly researched. Herein, we have synthesized two diblock copolymers composed of poly(3-hexylthiophene) (P3HT) and polyethylene glycol (PEG). Through a heating, cooling, and aging process, a series of multilayered hierarchical micelles and fibers were prepared in alcoholic solutions. The transition from fibers to hierarchical micelles are strictly influenced by the strength of the π-π stacking interaction, the PEG chain length, and solvent. In isopropanol, the P3HT22-b-PEG43 could self-assemble into hierarchical micelles composed of several two-dimensional (2D) laminar layers, driven by the π-π stacking interaction and van der Waals force. The P3HT22-b-PEG43 could not self-assemble into well-defined nanostructures in methanol and ethanol, but could self-assemble into fibers in isobutanol. However, the P3HT22-b-PEG113 with a longer corona block only self-assembled into fibers in four alcoholic solutions, due to the increase in dissolving capacity and steric hindrance. The sizes and the size distributions of the nanostructures both increased with the increase in polymer concentration and the decrease in solvent polarity. This study shows a method to fabricate the hierarchical micelles.

Effects of local fiber discontinuity on the fatigue strength parameter at the fiber inclusion corner in fiber-reinforced composites

Abstract To comprehend the fatigue failure mechanism at the fiber discontinuity in fiber-reinforced composites, it is necessary to evaluate the local mechanical behaviors. The fatigue strength depends on the stress distribution at the fiber inclusion corner. An improved advanced finite element method (IAFEM) is proposed for the stress intensity factor (SIF) analysis at the fiber inclusion corner. In the IAFEM, the element stiffness matrix of singular inclusion corner element (SICE) is obtained, and the singular elastic field at the tip of the fiber inclusion is determined. The effects of load direction, fiber distribution, fiber geometry, and material properties on SIFs are analyzed numerically using the IAFEM. The difference in stress field distribution between two-dimensional and three-dimensional fiber inclusions is discussed. The IAFEIM and calculation results can provide reference for fatigue strength analysis and preparation of composite materials.

Nonlinear flutter of 2D variable stiffness curvilinear fibers composite laminates by a higher-order shear flexible beam theory with Poisson’s effect

In this work, the nonlinear supersonic panel flutter characteristics of two-dimensional variable stiffness curvilinear fibres based laminated composite panels are studied using a higher-order shear flexible theory represented by sine function coupled with first-order approximation leading to quasi-aerodynamic theory. The structural formation takes care of geometric nonlinearity with von Karman’s assumptions. The beam constitutive equation is modified for the laminated beam with general lay-up by accounting for Poisson’s effect. The nonlinear dynamic equilibrium equations developed by Lagrangian equations of motion are solved using finite element approach in conjunction with the direct iterative solution procedure. For limit cycle oscillation, critical dynamic pressure is predicted iteratively through eigenvalue analysis, thereby identifying the first coalescence of vibrational modes. Also, the flutter behavior of two-dimensional panel under static differential pressure is investigated considering nonlinear static equilibrium position of panel obtained by Newton-Raphson’s iterative approach and then followed by modes coalescence approach. These solution procedures are tested against the results in literature. A thorough numerical investigation is done to show the effect of the curvilinear fiber path orientation, limited cycle amplitude, static differential pressure, panel thickness, panel end condition flexibilities and thermal environment on the nonlinear supersonic panel flutter of two-dimensional variable stiffness laminated panels.

Reproducibility of Neuroretinal Rim Measurements Obtained from High-Density Spectral Domain Optical Coherence Tomography Volume Scans.

PurposeTo compare the reproducibility of two-dimensional (2D) peripapillary retinal nerve fiber layer (RNFL) thickness and three-dimensional (3D) neuroretinal rim measurements using spectral domain optical coherence tomography (SDOCT) in normal and glaucoma subjects.MethodsOne eye per subject for 27 normal and 40 glaucoma subjects underwent repeat SDOCT RNFL thickness scans and optic nerve volume scans on the same day. From the volume scan, custom software calculated five neuroretinal rim parameters: 3D minimum distance band (MDB) thickness, 3D MDB area, 3D rim volume, 2D rim area, and 2D rim thickness. Within-subject variance (Sw), coefficient of variation (CV), and intraclass correlation coefficient (ICC) were analyzed.ResultsMDB thickness and RNFL thickness have similar reproducibility among normal and glaucoma subjects (eg, global MDB thickness CVs of 2.4% and 3.6%, and global RNFL thickness CVs of 1.3% and 2.2%; P > 0.05 for both comparisons). Reproducibility of MDB thickness was lower in glaucoma patients for the superior and inferior quadrants compared to normal subjects (CVs of 9.6% versus 3.4% and 6.9% versus 2.7%; P < 0.05, respectively). There were no statistically significant differences between both groups for RNFL thickness in the four quadrants. For both patient groups and for all regions, MDB thickness had the lowest CVs among all five neuroretinal rim parameters (eg, global MDB thickness CVs of 2.4% and 3.6% versus 3.0% and 18.9% for the other four neuroretinal rim parameters).ConclusionGlobal MDB and global RNFL thickness are similarly reproducible among normal and glaucoma subjects, though MDB thickness for the superior and inferior quadrants is less reproducible among glaucoma subjects.

An investigation of Al2O3 coating on quartz fiber fabric in aqueous solution near room temperature

Quartz fiber fabric is widely used in national defense, military and aerospace industries due to its good high-temperature resistance, chemical stability and excellent thermal shock resistance. However, the tendency of quartz fiber fabric to undergo thermal degradation due to crystallization at high temperature may destroy its high-temperature performance, particularly its high-temperature mechanical properties. In this study, an aluminum oxide (Al2O3) ceramic coating was synthesized on the surface of two-dimensional quartz fiber fabric in aqueous solution near room temperature. The surface morphology and chemical composition were studied to evaluate the quality of the coating by scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. The annealing behavior at high temperature was evaluated by using an electronic universal testing machine after high-temperature processing. The annealing behavior of the aluminum oxide coating could be improved effectively. The maximum load that the coated fabric can bear was 2.5 times higher than that of the original fabric, proving the superior high-temperature mechanical properties of the coated fabric. The coating on the surface of the fiber could block the damage of high temperature to the quartz fiber, improving the crystallization phenomenon of the quartz fiber at high temperature, followed by improvement in the high-temperature mechanical properties of the fabric.

Disk-shaped cellulose fibers from red algae, Eucheuma cottonii and its use for high oxygen barrier

We could prepare disk-shaped fibers without particular mechanical treatments from Eucheuma cottonii, the commonly used red algae for obtaining carrageenan. After carrageenan extraction from cottonii, the residues were bleached using chlorine dioxide and hydrogen peroxide. The morphology of the bleached fiber was disk-shaped one with a very thin fiber wall thickness of less than 100 nm and a diameter of approximately 100 μm. The sugar analysis and X-ray diffraction of the bleached fibers showed that they consisted of mostly glucose and had the same pattern as cellulose I with more than 50% crystalline structure, respectively. Compared to one-dimensional cellulose micro- or nanofibrils, which exhibits slow drainage and possess intolerably high drying energy, these two-dimensional disk-shaped fibers, when formed a layer in water medium, exhibit fast drainage and low drying energy. The formed sheet resulted in excellent transparency and high oxygen barrier property. Therefore, by using these disk-shaped, thin fibers from cottonii, we expect that the biodegradable and transparent oxygen barrier layer can be produced at a paper machine, which is, if possible, extremely difficult in the case of cellulose micro- or nanofibrils due to their slow drainage and high drying energy.

Rapid and One-Step Screening of Taxane Compounds by a Two-Dimensional Carbon Microfiber Fractionation System Combined with Tandem Mass Spectrometry.

Taxane compounds have attracted wide attention due to the basic chemical structure of taxol as an alternative anticancer drug. The full-scan tandem mass spectrometry (MS/MS) fragmentation behaviors of seven taxane compounds were studied. For taxanes of Sc-T and Sc-T-Xyl types, diagnostic product ions are originated from a cleavage in the ester bond of the C13 position and the C-O bond of the C7 position, and the subsequent fragmentation pattern is similar to those of M-type taxanes with the loss of different numbers of acetic acid moieties (AcOH), benzoic acid moieties (BzOH), and H2O molecules. A rapid (7 min) and one-step screening method of two-dimensional microscale carbon fiber and active carbon fiber columns combined with tandem mass spectrometry (2DμCFs-MS/MS) was developed for the screening of taxane compounds from Taxus cuspidata samples. Before MS/MS analysis, the 2DμCFs system can group the sample extract without any pretreatment into three chromatographic-type fractions of strong, medium, and weak polarity to avoid matrix interference, such as lipids and pigments. The 2DμCFs-MS/MS can also conduct qualitative and quantitative analysis of taxane compounds, which is evaluated by limits of detection ranging from 3 to 50 ng mL-1, limits of quantitation ranging from 10 to 150 ng mL-1, satisfactory recoveries from 75.2 to 112.2%, and reproducibilities with relative standard deviations from 1.4 to 11.7%.

Insights into fracture mechanisms and strength behaviors of two-dimensional carbon fiber reinforced silicon carbide composites at elevated temperatures

Carbon fiber reinforced silicon carbide (C/SiC) composites are usually subjected to thermal-mechanical-oxidation-coupled loads during service. However, their mechanical properties at ultra-high temperatures in oxidizing environments have rarely been reported. In this paper, a method based on the induction heating technology is proposed for testing the ultra-high-temperature mechanical properties of materials in air. The flexural behaviors of a 2D plain-weave C/SiC material prepared via chemical vapor infiltration are investigated in air up to 1800 °C for the first time. Inverse temperature dependences of the flexural modulus and strength are observed. New fracture mechanisms that are responsible for the mechanical behaviors at elevated temperatures are elucidated. Fracture modes at different temperatures are proposed. A high-temperature fracture strength model for oxidizing environments is developed, which is in good agreement with the experimental results. The factors affecting the fracture strength behaviors of the C/SiC in air at elevated temperatures are characterized quantitatively.

High-temperature compressive performance of the pre-impacted 2D-C/SiC composites: Coupling effect of pre-impact energy, temperature, temperature-keeping duration, and strain rate

Two-dimensional carbon fiber reinforced silicon carbide (2D-C/SiC) composites are well-known for the high-temperature performance in aeronautical and aerospace fields, but they are susceptible to foreign object damage in service. Therefore, the high-temperature performance of pre-impacted 2D-C/SiC is closely connected with flight security. In this study, the pre-impact testing was conducted using a stress-reversal split Hopkinson bar, and the pre-impact energies were set from 0.1J to 0.9J. Subsequently, the pre-impacted specimens were heated for a period in the temperature-keeping procedure from 20 °C to 1600 °C. Oxidation kinetics of the pre-impacted 2D-C/SiC specimens were obtained based on the weight loss-temperature trends. Finally, the specimens were compressed under high temperatures at the strain rates from 10−4/s to 1000/s, so the residual compressive strength (RCS)-temperature trends were achieved. Hence, the correlation between the weight loss and the RCS was established. Interestingly, the pre-impact strengthening effect on the compressive strength was found. The results revealed that the RCS of 2D-C/SiC is affected by various parameters, providing new sights into the high-temperature damage tolerance of ceramic matrix composites.

Finite element parametric analysis of RC columns strengthened with FRCM

Fiber reinforced cementitious matrix (FRCM), a noncorrosive two-dimensional high strength fiber reinforced polymer (FRP) mesh saturated with inorganic cementitious mortar is evolving as a viable option for retrofitting damaged RC structures. While numerous studies investigated the potential of FRCM strengthening in shear and flexural applications, limited studies explored the confinement of short and slender columns, particularly using finite element (FE) analysis. In this study, a three-dimensional (3D) nonlinear finite element (FE) model is developed using ABAQUS to study the behavior of corrosion damaged RC columns retrofitted with poly-paraphenylene-ben-zobisoxazole (PBO) FRCM systems. Geometric and material nonlinearities in concrete, cement mortar and composite are incorporated in the FE model that is validated through axial capacity and failure mode comparisons against published literature. A comprehensive parametric study involving 180 models is conducted considering the effects of five parameters: (a) cross section type (square vs circular), (b) FRCM wraps (1, 2, 3 and 4 layers), (c) pre-damage level (mild, moderate and severe), (d) eccentricity ratio (0.0, 0.3, 0.5, 0.75, 1.0, 1.25 and 1.5) and (e) column length (short and slender). Concrete compressive strength of 30 MPa and a longitudinal reinforcement ratio of 2% are adapted in all models. Results indicated that retrofitting corrosion damaged RC columns with PBO-FRCM effectively resorted and enhanced the original axial capacity and ductility of all column specimens and at all damage levels. A positive correlation between number of FRCM layers and axial capacity and ductility enhancement was observed and was more pronounced in circular columns. Increasing the number of FRCM layers also increased the axial capacity of eccentrically loaded columns irrespective of damage level and eccentricity ratio. Finally, comparison of axial capacity using ACI 549.4R-13 provisions against FE results disclosed that the code provisions underestimated the axial capacity of short RC columns retrofitted with PBO-FRCM by about 20%.

Thermal shock response behaviour of carbon fibre reinforced silicon carbide matrix composites prepared by chemical vapour infiltration at different heating rates

The present work investigated the effects of thermal cycles in air on the tensile properties of a two-dimensional carbon fibre reinforced silicon carbide composite (2D C/SiC) prepared by chemical vapour infiltration at different heating rates. The composite was exposed to different cycles of thermal shock between 20 °C and 1300 °C in air. The damage mechanisms were investigated by AE online monitoring and fractured morphology offline analysis. The tensile strength of 2D-C/SiC decreases with increasing thermal cycles. However, the modulus only decrease within 40 cycles. Due to oxidation, with the decrease in heating rate, the residual properties of the material decrease more obviously. Meanwhile, the results of AE online monitoring and fracture analysis show that the matrix damage is more serious at higher heating rate and that more delamination occours in tensile fractures. The above results indicate that for the thermal shock of 2D C/SiC composites in air, oxidative damage plays a key role in the residual properties.

Isogeometric finite element-based simulation of the aortic heart valve: Integration of neural network structural material model and structural tensor fiber architecture representations.

The functional complexity of native and replacement aortic heart valves (AVs) is well known, incorporating such physical phenomenons as time-varying non-linear anisotropic soft tissue mechanical behavior, geometric non-linearity, complex multi-surface time varying contact, and fluid-structure interactions to name a few. It is thus clear that computational simulations are critical in understanding AV function and for the rational basis for design of their replacements. However, such approaches continued to be limited by ad-hoc approaches for incorporating tissue fibrous structure, high-fidelity material models, and valve geometry. To this end, we developed an integrated tri-leaflet valve pipeline built upon an isogeometric analysis framework. A high-order structural tensor (HOST)-based method was developed for efficient storage and mapping the two-dimensional fiber structural data onto the valvular 3D geometry. We then developed a neural network (NN) material model that learned the responses of a detailed meso-structural model for exogenously cross-linked planar soft tissues. The NN material model not only reproduced the full anisotropic mechanical responses but also demonstrated a considerable efficiency improvement, as it was trained over a range of realizable fibrous structures. Results of parametric simulations were then performed, as well as population-based bicuspid AV fiber structure, that demonstrated the efficiency and robustness of the present approach. In summary, the present approach that integrates HOST and NN material model provides an efficient computational analysis framework with increased physical and functional realism for the simulation of native and replacement tri-leaflet heart valves.

Development and analysis of surface plasmon resonance based refractive index sensor for pregnancy testing

In the proposed work, a two-dimensional photonic crystal fiber (PCF) based on the surface plasmon resonance (SPR) refractive index sensor has been demonstrated and designed which is so much helpful to gain a better sensitivity response in urine observation. In order to detect the pregnancy, the simulation and analysis have been performed in both normal and pregnant urine with the effective refractive indices values of 1.335, 1.34, 1.342 and 1.343 within the range of working wavelength from 1.75 µm to 2 µm. From this testing sensor, the optical parameters of the dispersion relation, birefringence, coupling length, confinement loss, insertion loss, sensor length, crosstalk, sensitivity response, resonance wavelength, resolution, and sensitivity per line-width have been analyzed. Besides, Finite element method (FEM) is used for the numerical investigations. From this investigation, the highest value of sensitivity response, sensitivity per line-width, and the resolution of 68051.344 nm/RIU, 314 RIU−1, and 9.39 × 10−6 RIU are gained. It is noted that the proposed sensor offers significant sensing performances for the polarized modes. The main goal of this investigation is to develop the concepts of optoelectronics and laser bio-sensor in the field of biological detection systems. As a result, this structure of optical biosensor will be applicable through the modified optical fiber in biological changes.

Radiation damage of a two-dimensional carbon fiber composite (CFC)

Carbon fiber composites (CFC) are, among other applications, already in use as low-impedance collimating elements for intercepting TeV-level protons machines, like the CERN Large Hadron Collider. Towards a comprehensive understanding of these materials’ properties and behavior, a series of radiation damage campaigns have been undertaken in order to quantitively investigate the response of AC-150 K CFC to high proton fluences. The CFCs dimensional changes, stability, micro-structural evolution, and structural integrity below and above 5 × 1020 p/cm2 fluence threshold were studied. The irradiating particles were protons of kinetic energies in the range of 130–200 MeV. The effects of the irradiation temperature (~90–180 °C and 280–500 °C) combined with the proton fluence on the dimensional stability and the microstructural evolution of this anisotropic two-dimensional composite structure were studied using precision dilatometry and X-ray diffraction. Our results shed light on the fluence-based limitations for these composite materials. Furthermore, we compare these results with reference unirradiated graphite, and we discuss the similarities and differences in the dimensional changes and post-irradiation annealing properties.

Kilometers Long Graphene-Coated Optical Fibers for Fast Thermal Sensing.

The combination of optical fiber with graphene has greatly expanded the application regimes of fiber optics, from dynamic optical control and ultrafast pulse generation to high precision sensing. However, limited by fabrication, previous graphene-fiber samples are typically limited in the micrometer to centimeter scale, which cannot take the inherent advantage of optical fibers—long-distance optical transmission. Here, we demonstrate kilometers long graphene-coated optical fiber (GCF) based on industrial graphene nanosheets and coating technique. The GCF shows unusually high thermal diffusivity of 24.99 mm2 s−1 in the axial direction, measured by a thermal imager directly. This enables rapid thermooptical response both in optical fiber Bragg grating sensors at one point (18-fold faster than conventional fiber) and in long-distance distributed fiber sensing systems based on backward Rayleigh scattering in optical fiber (15-fold faster than conventional fiber). This work realizes the industrial-level graphene-fiber production and provides a novel platform for two-dimensional material-based optical fiber sensing applications.