The effects of surface treatments of fibers on the interfacial properties in single-fiber composites

The interfacial properties between fibers and the matrix contribute to the overall properties in high performance composites. Plasma treatments (Ar, O₂, CF₄/O₂, N₂/H₂) have been performed on carbon fibers to improve the fiber-matrix interaction. The treatment efficiency was checked by the single-fiber technique, while the surface chemistry and morphology were characterized by X-ray photoelectron spectroscopy (XPS), static secondary ion mass spectroscopy (SSIMS), and scanning electron microscopy (SEM). The O₂- and N₂/H₂-plasma treatments proved most effective both for introducing oxygen-containing functionalities at the fiber surface and for improving the interfacial shear strength of carbon fiber/epoxy composites. A relationship between the oxygen concentration at the fiber surface and the interfacial shear strength is demonstrated.     

The Magnetism Properties and Surface Microstructure of NBR/Fe3O4 Composites

For preparing the good magnetism properties of rubber, NBR/Fe₃O₄ composites are prepared. In the experiment, the surface microstructure of NBR/Fe₃O₄ and distribution of nano-Fe₃O₄ particles are analyzed. The results showed that after the addition of nano-Fe₃O₄, the surface microstructure of NBR/Fe₃O₄ is greatly improved. The interface bonding of nano-Fe₃O₄ and NBR are close-knit. With adding different mass fractions of nanoparticles, the maximum elongation 300% stress at definite elongation and the tensile strength of composites are decreased, but the shore A hardness of composites is improved. The magnetic property of composites can only rely on mass fraction of nano-Fe₃O₄, while uncorrelated to the degree of scatter of nano-Fe₃O₄.     

Influence of Fe3O4 nanoparticles decoration on dye adsorption and magnetic separation properties of Fe3O4/rGO nanocomposites

Magnetite (Fe₃O₄) nanoparticles were prepared by solvothermal method and its composites with reduced graphene oxide namely FG1, FG2, and FG3 (changing magnetite precursor loading 0.1, 0.5, and 1 respectively) were used as adsorbents for the removal of methyl violet (MV) dye. The structural and morphological results confirm that rGO sheets were decorated with Fe₃O₄ and it ensures the variation of active sites toward dye removal property. The maximum adsorption capacity obtained for FG2 was 196 mg/g. The adsorption isotherms and kinetics better fit Langmuir and pseudo-second-order kinetic model for FG1 and FG2. Increasing of Fe₃O₄ loading on rGO reduces the dye adsorption sites and too low Fe₃O₄ loading affects the magnetic separation. The optimal loading of Fe₃O₄ on rGO is important parameter for the adsorption process and fast separation of adsorbent.     

Effect of fiber type on mechanical properties of short carbon fiber reinforced B4C composites

In order to enhance the mechanical properties of B₄C without density increase, the short carbon fibers M40, M55J and T700 reinforced B₄C ceramic composites were fabricated by hot-pressing process. The addition of the carbon fibers accelerates the densification of the B₄C, decreases their densities, and improves their strength and toughness. The enhancement effects of the three kinds of carbon fibers were studied by investigating the density, Vickers hardness and the mechanical properties such as flexural strength, flexural modulus and fracture toughness of the composites. The fiber type has a great influence on the mechanical properties and enhancement of the short carbon fiber reinforced B₄C composites. The flexible carbon fiber with high strength and low modulus such as T700 is appropriate to reinforce the B₄C matrix ceramic composites.     

THE INFLUENCE OF OXIDATION OF THE FIBERS ON THE TRIBOLOGICAL PROPERTIES OF CARBON FIBER-REINFORCED NYLON COMPOSITES

Three-dimensional braided carbon fiber-reinforced nylon composites (C_3D/MCN) were prepared in order to investigate the influence of oxidation of carbon fibers on the tribological properties of the C_3D/MCN composites. Friction and wear tests of the C_3D/MCN composites with untreated and treated carbon fabric were conducted. The characteristics of the carbon fiber, the interface strength, the hardness, and the worn surface morphologies of the C_3D/MCN composites were analyzed. The results show that the specific surface area of treated carbon fiber was far higher than that of untreated carbon fiber and there formed a functional group of –C=O on the carbon fiber surface after air oxidation. The oxidation of the carbon fibers improved the interface strength between the carbon fibers and the matrix and had little effect on the hardness of the composites. The friction coefficient and wear rate of C_3D/MCN composites with oxidized carbon fibers were apparently lower than those with untreated carbon fibers. In conclusion, the oxidation of the fibers showed good effects on the improvement of the interface strength and the tribological properties of the composites.     

Mechanical properties of carbon fiber composites modified with nano-SiO2 in the interphase

The performance of carbon fibers-reinforced composites is dependent to a great extent on the properties of fiber–matrix interface. To improve the interfacial properties in carbon fibers/epoxy composites, nano-SiO₂ particles were introduced to the surface of carbon fibers by sizing treatment. Atomic force microscope (AFM) results showed that nano-SiO₂ particles had been introduced on the surface of carbon fibers and increase the surface roughness of carbon fibers. X-ray photoelectron spectroscopy (XPS) showed that nano-SiO₂ particles increased the content of oxygen-containing groups on carbon fibers surface. Single fiber pull-out test (IFSS) and short-beam bending test (ILSS) results showed that the IFSS and ILSS of carbon fibers/epoxy composites could obtain 30.8 and 10.6% improvement compared with the composites without nano-SiO₂, respectively, when the nano-SiO₂ content was 1 wt % in sizing agents. Impact test of carbon fibers/epoxy composites treated by nano-SiO₂ containing sizing showed higher absorption energy than that of carbon fibers/epoxy composites treated by sizing agent without nano-SiO₂. Scanning electron microscopy (SEM) of impact fracture surface showed that the interfacial adhesion between fibers and matrix was improved after nano-SiO₂-modified sizing treatment. Dynamic mechanical thermal analysis (DMTA) showed that the introduction of nano-SiO₂ to carbon fibers surface effectively improved the storage modulus of carbon fibers/epoxy.     

Multifuctional Fe3O4@C/YVO4:Dy nanopowers: Preparation,luminescence and magnetic properties

As-synthesized Fe₃O₄ nanoparticles were encapsulated with carbon layers through a simple hydrothermal process. Fe₃O₄/C nanoparticles were coated with YVO₄:Dy³⁺ phosphors to form bifunctional Fe₃O₄@C@YVO₄:Dy³⁺ composites. Their structure, luminescence and magnetic properties were characterized by XRD, SEM, TEM, HRTEM, PL spectra and VSM. The experimental results indicated that the as-prepared bifunctional composites displayed well-defined core–shell structures. The ∼12 nm diameter YVO₄:Dy³⁺ shell exhibited tetragonal structure. Additionally, the composites exhibited a high saturation magnetization (13 emu/g) and excellent luminescence properties, indicating their promising potential as multifunctional biosensors for biomedical applications.     

Mn3O4 nanoparticles embedded into graphene nanosheets: Preparation, characterization, and electrochemical properties for supercapacitors

Mn₃O₄/graphene nanocomposites were synthesized by mixing graphene suspension in ethylene glycol with MnO₂ organosol, followed by subsequent ultrasonication processing and heat treatment. The as-prepared product consists of nanosized Mn₃O₄ particles homogeneously distributed on graphene nanosheets, which has been confirmed by field emission scanning electron microscopy and transmission electron microscopy analysis. Atomic force microscope analysis further identified the distribution of dense Mn₃O₄ nanoparticles on graphene nanosheets. When used as electrode materials in supercapacitors, Mn₃O₄/graphene nanocomposites exhibited a high specific capacitance of 175 F g⁻¹ in 1 M Na₂SO₄ electrolyte and 256 F g⁻¹ in 6 M KOH electrolyte, respectively. The enhanced supercapacitance of Mn₃O₄/graphene nanocomposites could be ascribed to both electrochemical contributions of Mn₃O₄ nanoparticles, functional groups attached to graphene nanosheets, and significantly increased specific surface area.     

Microwave Absorption Studies on Superparamagnetic Conducting Nanocomposites as Signal Coating Materials

In this paper, preparation and characterization of superparamagnetic nanoparticles and their polymer composites prepared by varing doping level of conducting polymer and their microwave absorption studies at radar system in 8–12 GHz frequency range have been discussed. These composites are conducting polymers have been widely used because of their lower density as well their good environmental stability as in the case of polyaniline (PAN). In the present work, in situ polymerization of aniline was carried out in the presence of 30 mole% Fe₃O₄ nanoparticles to synthesize polyaniline/Fe₃O₄(PAN/Fe₃O₄) composites in epoxy resin matrix. The composites, thus synthesized have been characterized by infrared (IR) spectroscopy and X-ray diffraction. The morphology of these composites was studied by scanning electron microscopy. The measurement of % absorption was carried out in X and K band microwave region.     

Fabrication and mechanical properties of short ZrO2 fiber reinforced NiFe2O4 matrix composites

Short ZrO₂ fibers (ZrO_2(f)) reinforced NiFe₂O₄ ceramic composites were fabricated by cold pressing process. The phase composition, microstructure, mechanical properties and fiber/matrix interface of the composites were investigated by X-ray diffraction, scanning electron microscopy and mechanical testing machines. ZrO_2(f) show good thermodynamic and chemical compatibility with NiFe₂O₄ ceramic matrix and effectively enhanced the mechanical properties. The toughening mechanisms are fiber bridging, interfacial debonding, fiber pullout, phase transformation and the matrix constraint effect. By incorporation of 3 wt% fibers with the average length of 5～6 mm, the bending strength and fracture toughness of the composites reached 88.92 MPa and 4.62 MPa m^1/2, respectively, while the strength conservation ratio after thermal shock increased from 48.85% to 75.86%. The weak interface bonding built up between ZrO_2(f) and NiFe₂O₄ facilitates the reinforcing effects of the fibers to operate.     

High strength polyimide fibers with functionalized graphene

Graphene possesses unprecedented physical and chemical properties and has been thought to be ideal filler for reinforcing fibers' mechanical properties. However, graphene is difficultly dispersed in polymer which severely restrict to prepare high-strength and high-modulus composites. In this work, we report an effective method to fabricate a kind of organ-soluble polyimide (PI)/graphene composite fiber using in situ polymerization. Graphene oxide (GO) is modified by 4,4′-diaminodiphenyl ether (ODA) to obtain the GO-ODA nanosheets which exhibit excellent dispersibility and compatibility with the organ-soluble PI matrix. WAXD results show that these 2D nanosheets have a significant influence on the crystallization, aggregation or assembly behaviors of the polymer chains. The PI/graphene composite fiber containing 0.8 wt% of GO-ODA presents a tensile strength of 2.5 GPa (1.6 times higher than the pure PI fiber), and tensile modulus of 126 GPa (223% raises compared with pure PI fiber). Furthermore, the incorporation of graphene significantly improves the glass transition temperature and thermal stability of the composite fibers. Thanks to the excellent hydrophobic properties of graphene, the hydrophobic behavior of the composite fibers is greatly improved. This effective approach shows a potential application in fabricating multifunctional polymer-based composite fibers.     

Enhanced cycling performance of Fe3O4-graphene nanocomposite as an anode material for lithium-ion batteries

Fe₃O₄-graphene nanocomposite was prepared by a gas/liquid interface reaction. The structure and morphology of the Fe₃O₄-graphene nanocomposite were characterized by X-ray diffraction, scanning electron microscopy and high-resolution transmission electron microscopy. The electrochemical performances were evaluated in coin-type cells. Electrochemical tests show that the Fe₃O₄-22.7 wt.% graphene nanocomposite exhibits much higher capacity retention with a large reversible specific capacity of 1048 mAh g⁻¹ (99% of the initial reversible specific capacity) at the 90th cycle in comparison with that of the bare Fe₃O₄ nanoparticles (only 226 mAh g⁻¹ at the 34th cycle). The enhanced cycling performance can be attributed to the facts that the graphene sheets distributed between the Fe₃O₄ nanoparticles can prevent the aggregation of the Fe₃O₄ nanoparticles, and the Fe₃O₄-graphene nanocomposite can provide buffering spaces against the volume changes of Fe₃O₄ nanoparticles during electrochemical cycling.     

Improvement of interface between Al and short carbon fibers by α-Al2O3 coatings deposited by sol–gel technology

This paper describes an investigation on an improvement of the interface between Al and short carbon fibers (SCFs) with α-Al₂O₃ coating by sol–gel technology. The composites of Al/uncoated SCFs and Al/α-Al₂O₃-**coated SCFs were fabricated successfully by vacuum press infiltration. The formation of α-Al₂O₃ coating during calcination was analysed by Fourier transform infrared (FTIR) and X-ray diffraction (XRD). Scanning electron microscopy (SEM), energy-dispersive analysis of X-ray (EDAX) and transmission electron microscope (TEM) were used to observe the coated SCFs and the interface of composites. The results showed that the average thickness of the α-Al₂O₃ coating was about 200–250 nm and the formation of Al₄C₃ at the interface between Al matrix and SCFs was controlled by the α-Al₂O₃ coatings.     

Ultra-high compression and wear resistant hybrid filled polyimide composite: Synergistic effect of Fe2O3 decorated RGO

Herein, the tribological performance, thermal and compression resistance behavior of polyimide (PI) reinforced by Fe₂O₃ decorated reduced graphene is systematically investigated. The remarkable synergistic effect of Fe₂O₃ decorated reduced graphene oxide (RGO) is demonstrated in its PI wear resistance, and PI/RGO/Fe₂O₃ composites show good thermal stability and much higher compression resistant ability than PI, PI/RGO, and PI/Fe₂O₃ composites when the filling contents are same. Additionally, the PI/RGO/Fe₂O₃ composites also exhibited ultra-wear-resistant properties under high load condition, and the lowest wear rate is 3.18 × 10⁻⁸ mm³N⁻¹ m⁻¹, which is an order of magnitude lower than that of pure PI. The investigation of its tribological mechanism also showed strong synergistic effect and interface force of Fe₂O₃ decorated RGO, which contribute to its high-performance friction-reducing behaviors. These findings give an inside view to Fe₂O₃ decorated RGO and its polyimide composites, and open an avenue for the graphene oxide (GO) based composite to act as compression wear-resisting solid fillers and lubricants when polymer composite with excellent compressive, thermal and tribological properties is required.     

High-strength superparamagnetic composite fibers

The polymer composites of magnetic nanoparticles can be possibly used in a bulk form by preserving all the novel characteristics of magnetic nanoparticles such as superparamagnetic behavior. By introducing magnetic properties of Fe₃O₄ nanoparticles into polymer fibers, novel magnetic properties combine with the advantages of composite fibers such as light-weight and ease-of-use. Using dry-jet-wet fiber spinning technology, we have successfully fabricated iron oxide/polyacrylonitrile (Fe₃O₄/PAN) composite fibers with 10 wt% nanoparticle in the polymer matrix. Composite fiber with a diameter as small as 15 μm can achieve tensile strength and tensile modulus values as high as 630 MPa and 16 GPa, respectively. Superparamagnetic properties of Fe₃O₄ nanoparticles were preserved in the composite fibers with saturation magnetization at 80 emu/g and coercivity of 165 G.     

A multiscale methodology quantifying the sintering temperature‐dependent mechanical properties of oxide matrix composites

A novel methodology combining multiscale mechanical testing and finite element modeling is proposed to quantify the sintering temperature‐dependent mechanical properties of oxide matrix composites, like aluminosilicate (AS) fiber reinforced Al₂O₃ matrix (AS_f/Al₂O₃) composite in this work. The results showed a high‐temperature sensitivity in the modulus/strength of AS fiber and Al₂O₃ matrix due to their phase transitions at 1200°C, as revealed by instrumented nanoindentation technique. The interfacial strength, as measured by a novel fiber push‐in technique, was also temperature‐dependent. Specially at 1200°C, an interfacial phase reaction was observed, which bonded the interface tightly, as a result, the interfacial shear strength was up to ≈450 MPa. Employing the measured micro‐mechanical parameters of the composite constituents enabled the prediction of deformation mechanism of the composite in microscale, which suggested a dominant role of interface on the ductile/brittle behavior of the composite in tension and shear. Accordingly, the AS_f/Al₂O₃ composite exhibited a ductile‐to‐brittle transition as the sintering temperature increased from 800 to 1200°C, due to the prohibition of interfacial debonding at higher temperatures, in good agreement with numerical predictions. The proposed multiscale methodology provides a powerful tool to study the mechanical properties of oxide matrix composites qualitatively and quantitatively.     

Fabrication of graphene/prussian blue composite nanosheets and their electrocatalytic reduction of H2O2

In this work, graphene/prussian blue (PB) composite nanosheets with good dispersibility in aqueous solutions have been synthesized by mixing ferric-(III) chloride and potassium ferricyanide in the presence of graphene under ambient conditions. Transmission electron microscopy (TEM) shows that the average size of the as-synthesized PB nanoparticles on the surface of graphene nanosheets is about 20 nm. Fourier-transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) patterns have been used to characterize the chemical composition of the obtained graphene/PB composite nanosheets. The graphene/PB composite nanosheets exhibit good electrocatalytic behavior to detection of H₂O₂ at an applied potential of −0.05 V. The sensor shows a good linear dependence on H₂O₂ concentration in the range of 0.02-0.2 mM with a sensitivity of 196.6 μA mM⁻¹ cm⁻². The detection limit is 1.9 μM at the signal-to-noise ratio of 3. Furthermore, the graphene/PB modified electrode exhibits freedom of interference from other co-existing electroactive species. This work provides a new kind of composite modified electrode for amperometric biosensors.     

The effect of silica (SiO2) nanoparticles and ammonia/ethylene plasma treatment on the interfacial and mechanical properties of carbon-fiber-reinforced epoxy composites

A nanoparticle dispersion is known to enhance the mechanical properties of a variety of polymers and resins. In this work, the effects of silica (SiO₂) nanoparticle loading (0–2 wt%) and ammonia/ethylene plasma-treated fibers on the interfacial and mechanical properties of carbon fiber–epoxy composites were characterized. Single fiber composite (SFC) tests were performed to determine the fiber/resin interfacial shear strength (IFSS). Tensile tests on pure epoxy resin specimens were also performed to quantify mechanical property changes with silica content. The results indicated that up to 2% SiO₂ nanoparticle loading had only a little effect on the mechanical properties. For untreated fibers, the IFSS was comparable for all epoxy resins. With ethylene/ammonia plasma treated fibers, specimens exhibited a substantial increase in IFSS by 2 to 3 times, independent of SiO₂ loading. The highest IFSS value obtained was 146 MPa for plasma-treated fibers. Interaction between the fiber sizing and plasma treatment may be a critical factor in this IFSS increase. The results suggest that the fiber/epoxy interface is not affected by the incorporation of up to 2% SiO₂ nanoparticles. Furthermore, the fiber surface modification through plasma treatment is an effective method to improve and control adhesion between fiber and resin.     

Tailoring Carbon Fiber/Carbon Nanotubes Interface to Optimize Mechanical Properties of Cf‐CNTs/SiC Composites

C_f/SiC composites were fabricated using fiber coatings including CNTs and matrix infiltration using the polymer impregnation and pyrolysis process. Interface between fiber and CNTs (CF/CNTs) was tailored to optimize mechanical properties of hybrid composites. The tailored interphases, such as Pyrocarbon (PyC) and PyC/SiC, protect fibers from degradation during the growth of CNTs successfully. Hybrid composites with well‐tailored CF/CNTs interface displayed significantly increased mechanical strength (352 ± 21 MPa) compared with that (34 ± 3 MPa) of composites reinforced with CNTs, which grown on carbon fibers directly. The interfacial bonding strength of hybrid composites was improved and optimized by tailoring the CF/CNTs interface. Interfacial failure modes were studied, and a firm interface bonding at the joint where CNTs grown was observed.     

Facile Synthesis of FeCo/Fe3O4 Nanocomposite with High Wave-Absorbing Properties

The FeCo/Fe₃O₄ nanocomposite was synthesized using the hydrothermal approach, in which the FeCo alloy and Fe₃O₄ are formed by one step. The structure of the FeCo/Fe₃O₄ nanocomposite was characterized by means of Scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray energy-dispersive spectrometer spectroscopy (EDX). They show that the mass ratio of FeCo/Fe₃O₄ strongly depends on the reaction temperature. Such various architectures follow a stepwise growth mechanism of the composites prepared in various reaction temperatures were also discussed. It indicates that this strategy is facile, effective and controllable for the synthesis of FeCo/Fe₃O₄ by the one-step method. Furthermore, the magnetic and wave-absorbing properties of the nanocomposites with various structures were investigated in detail. The results show that the FeCo/Fe₃O₄ with higher mass ratio has higher magnetic properties. Moreover, the FeCo/Fe₃O₄ nanocomposite shows high wave-absorbing properties (e.g., −37.9 dB), which are expected to apply in microwave absorbing materials.