Silicon Carbide Nanofibers Research Articles

Thermal insulated C/SiC nanofiber aerogel with high thermal stability and superior electromagnetic wave absorption performance

Integration of thermal insulation and electromagnetic wave absorption was crucial in stealth technology and hypersonic vehicles but challenging. Herein, silicon carbide nanofibers were synthesized by in situ chemical vapor deposition within a carbon foam skeleton to form a wave absorbing and heat insulating integrated composite aerogel with a hierarchical porous structure. The unique hierarchical porous structure provided an excellent platform for the absorption of electromagnetic waves, achieving a minimum reflection loss (RLmin) of −51.46 dB at 17.20 GHz. Meanwhile, the C/SiC nanofiber aerogel maintained a low density of 0.013 g/cm3, an ultra-low thermal conductivity of 0.030 W/(m⋅K) and a high thermal stability up to 1000 °C. Furthermore, to enhance the electromagnetic wave (EMW) absorption property of the aerogel, polypyrrole (PPy) was coated on the surface of C/SiC nanofiber aerogel by facile impregnation and chemical polymerization. The multiple conductor-semiconductor-conductor structure of C/SiC-PPy composite aerogel leads to various EMW loss mechanisms and excellent impedance match, resulting in an outstanding EMW absorption performance, with a RLmin of −60.31 dB at 2.96 GHz.

Structure and properties of fiber-reinforced LiZn ferrite ceramics prepared via spark plasma sintering

In order to improve the matrix cracking of LiZn ferrite (LZF) ceramics during spark plasma sintering, fiber-reinforced LZF materials were prepared using silicon carbide nanofibers (SCFs) and alumina whiskers (AWs) as reinforcement phases. The effect of fiber reinforcement on the microstructure and mechanical, electrical, and magnetic properties of LZF was systematically studied. The results reveal that SCFs lead to an increase in grain size of SCF-reinforced LiZn ferrites (LZF-S) and a deterioration of grain morphology due to the transgranular behavior of SCFs. The increase in complex dielectric constant and dielectric loss, as well as the decrease in resistance of LZF-S, is due to the increase in Fe2+ concentration in ceramics and low resistance of SCFs. AW-reinforced LiZn ferrites (LZF-A) show the opposite effect due to the high porosity caused by AWs and the high resistance of AWs. LZF-S exhibits high fiber/matrix bonding strength, which permits the transfer of the load from the matrix to the fiber to be more effective, leading to a high fracture toughness (KIC) of 5.1 MPa m1/2. The bonding strength between fiber and matrix of LZF-A is low, but a large number of pores passivate the crack tip. At an SCF content of less than 2.5 wt%, the saturation magnetization (Ms) of LZF does not decrease obviously, but a small amount of AWs leads to a significant decrease in Ms (pure LZF: 83 emu·g−1; 1.0 wt% SCFs: 80 emu·g−1; 1.0 wt% AWs: 62 emu·g−1), which can be ascribed to the partial substitution of Fe3+ by nonmagnetic Al3+ ions. When the content of reinforcement phases is 1 wt%, the ferroresonance linewidth increases significantly due to the high porosity caused by the secondary phases (pure LZF: 234 Oe; 1.0 wt% SCFs: 2161 Oe; 1.0 wt% AWs: 1020 Oe).

The impact of various carbon nanomaterials on the morphological, behavioural, and biochemical parameters of rainbow trout in the early life stages

With the increasing production and the number of potential applications of carbon nanomaterials, mainly from the graphene family, their release into the natural environment, especially to aquatic ecosystems, is inevitable. The aim of the study was to determine the effects of various carbon nanomaterials (graphene nanoflakes (GNF), graphene oxide (GO), reduced graphene oxide (RGO) and silicon carbide nanofibers (NFSiC) in the concentration of 4 mg L−1 on the early life stages of the rainbow trout Oncorhynchus mykiss. The survival rates of O. mykiss were not affected after 36 days of exposure to studied materials, except for RGO, which caused significant mortality of both embryos and larvae compared to the control conditions. Larvae exposed to GO and NFSiC were characterized by a smaller standard body length at hatch, whereas at the end of the experiment, the growth of fish exposed to all materials was accelerated, especially in GO and RGO treatment, in which higher body weight and length were accompanied by lower volume of the yolk sac. Neither the markers of the oxidative damage nor the antioxidant enzymes activities were significantly affected in embryos, newly hatched larvae and larvae after 26-day exposure to studied carbon nanomaterials. Also, no neurotoxic effect expressed by the activity of the whole-body acetylcholinesterase was observed. Nevertheless, the significant increase in the velocity and the overall activity of larvae exposed to GNF (not investigated after exposure to other materials) must be highlighted. The most pronounced effect of RGO might be connected with its large particle size, sharp edges, and the presence of TiO2 nanoparticles. The results indicate for the first time that various carbon nanomaterials potentially released into aquatic ecosystems may have serious developmental implications for the early life stages of salmonid fish.

Tough monolithic TiO2 materials fabricated by the sol-gel process accompanied with phase separation in solutions of SiC nanofibers and preceramic polymers

In recent decades, the sol-gel process accompanied with phase separation has been employed to fabricate porous monolithic ceramic materials. However, it is challenging to obtain crack-free samples by using this method, due to the fragile nature of porous ceramic materials and the large internal stress generated from drying and calcination process. In this work, tough monolithic titania (TiO2) materials were fabricated by the sol-gel process accompanied with phase separation in solutions of silicon carbide (SiC) nanofibers and preceramic polymers. It was found that polyethylene oxide (PEO) and ethylenediamine (EDA) can promote phase separation and sol-gel process respectively, and the micro-morphology of porous monolithic TiO2 materials can be flexibly tuned by adjusting the contents of PEO and EDA. The addition of SiC nanofibers effectively enhanced the mechanical performance and photocatalytic activity of porous TiO2 materials without altering their bicontinuous micro-morphology. Taking TiO2 materials as an example, this work demonstrates a novel methodology to fabricate ceramic nanofibers reinforced porous monolithic ceramic materials.

A comparative study on the effect of different fibrous nanofillers on the properties of natural rubber nanocomposites

AbstractThe specific geometry and distinct properties of one‐dimensional nanostructures make them the most ideal candidates as reinforcing elements in composites and the dependence of physical, mechanical, thermal, and wear properties of polymer composites on their dimensionality, nature, and dispersion is interesting. The upsurging demands for high‐performance elastomer composites require the application of such nanomaterials as reinforcing agents. Here, we offer a detailed characterization of some of the novel fibrous nanofillers such as silicon carbide nanofibers, aramid nanofibers, carbon nanotubes, and graphite nanofibers. Morphology, crystallinity, surface chemistry, polarity, and thermal stability of these nanofibers were analyzed using techniques such as electron microscopy, X‐ray diffraction, infrared and Raman spectroscopy, and thermogravimetric analysis. Natural Rubber nanocomposites were developed using these fibrous nanofillers, and their rheometric, mechanical, dynamic mechanical, and thermal properties were studied. ANF‐reinforced compounds gave the highest increment in 300% modulus while the highest tensile strength was obtained by CNT reinforced compounds at 4 phr filler loading. CNT and GNF‐reinforced compounds improved the wear resistance simultaneously by 43% and 33% respectively, while SiC and ANF improved it by 10% and 8% respectively. Lower tan delta and better thermal stability were also recorded. Future exploration may involve the use of these nanofibers in conjunction with carbon black or silica to achieve high‐performance elastomer compounds for real‐life applications.

MECHANICAL PROPERTIES OF NATURAL RUBBER AND STYRENE–BUTADIENE RUBBER NANOCOMPOSITES WITH NANOFILLERS HAVING DIFFERENT DIMENSIONS AND SHAPES AT LOW FILLER LOADING

ABSTRACT Reinforcement of rubber by nanofillers has been a topic of great interest in recent years. This work compares the reinforcing efficiency of nanofillers with different topologies such as spherical (carbon black and silica), fibrous (silicon carbide nanofibers and carbon nanotubes), and sheetlike (nanoclays, expanded graphite, and graphene) in two different diene rubbers (natural rubber [NR] and styrene–butadiene rubber [SBR]) at low loadings. Tensile strength improved by 88% in the case of NR and 57% in the case of SBR by the addition of just 3 phr of graphene nanoplatelets with high aspect ratio and surface area. An increase in the Mooney–Rivlin constant (C1) with filler loading variation was also observed for these filler systems in NR and SBR. The analysis of the composites using a tube model showed that the confinement of rubber chains due to the presence of fillers with a high aspect ratio gave rise to a lower tube diameter. The addition of nanofillers resulted in higher hysteresis losses, confirming their ability for higher energy dissipation. A higher Payne effect was observed in the composites due to the formation of a percolating filler network, which was accompanied by a weak strain overshoot in the loss modulus. Dynamical mechanical analysis of the composites showed a significant increase in the storage modulus of the composites at both low and room temperatures. The reduction observed in the tan δ was correlated with the crosslink density of the composites.

Simple in situ synthesis of SiC nanofibers on graphite felt as a scaffold for improving performance of paraffin-based composite phase change materials.

A paraffin phase change material absorbed in a composite material of silicon carbide nanofibers and graphite fibers was prepared by vacuum impregnation to solve problems of current organic phase change materials, such as the low thermal response rate, low thermal conductivity, and high vulnerability to leakage. A composite material containing a phase change material as the scaffold combined with silicon carbide nanofibers is prepared by a simple vapor–solid reaction using industrially produced porous graphite felt as the raw material. The thermal conductivity of the composite phase change material is increased to 1.29 W m−1 K−1 by thermal strengthening of the supporting scaffold. Compared with the thermal conductivity of pure paraffin of 0.25 W m−1 K−1, not only is the thermal response rate improved, but the composite phase change material also exhibits chemical stability, shape stability, and stable thermal properties. The phase change enthalpies of the melting and freezing processes are 180.5 and 176.4 J g−1, respectively. In addition, the use of low-cost graphite felt and the simple synthetic process of the composite phase change material facilitates large-scale production. Moreover, the composite is extremely flexible in terms of its shape design and has good energy storage properties in terms of photo-thermal conversion. These features promise to accelerate the effective application of the prepared composite phase change material in solar and buildings energy storage with great potential for application practices.

In-situ growth of silicon carbide nanofibers on carbon fabric as robust supercapacitor electrode

Silicon carbide nanofibers (SiCnf) that possess high electron mobility and wide bandgap have attracted tremendous research attention in the past decades, and they have been of paramount importance in promoting the application of novel energy technologies. Herein, we proposed a facile and efficient method to accelerate the in-situ growth of SiCnf on a carbon fabric with fused KCl. The carbon fabric impregnated with KCl solution can realize an efficient reaction between the active carbon atom and the silicon source at a temperature as low as 1100 °C. The as-obtained composite yields a porous structure with an enhanced graphitization degree. It is suggested that the fused KCl can promote the growth of SiCnf with much lower energy consumption, and the proposed method is facile, eco-friendly, and easy to be scaled-up. When evaluated as a supercapacitor electrode, the as-prepared material exhibits a capacitance as high as 4.36 mF⋅cm−2 at a scan rate of 0.05 V⋅s−1. Furthermore, the capacitance of the as-assembled supercapacitor exhibits an increase of 6.51% after 10000 cycles at room temperature. Therefore, the prepared SiCnf is a good candidate for supercapacitor electrodes. This work may facilitate the design of high-performing supercapacitor electrodes in the future.

Enhanced Photocatalytic Activity of Boron Doped Silicon Carbide Nanofibers and Its Composite with Polyvinyl Borate

ABSTRACT Boron doped silicon carbide (B-SiC) and its composite with polyvinyl borate (PVB) were studied due to the role of boron acting as an electron-acceptor, which can reduce the recombination rate of the photoinduced electron–hole pair on SiC upon UV light irradiation. The structure and morphology of SiC and B-SiC, and their PVB composites were characterized by FTIR, X-ray diffraction spectroscopy and field emission scanning electron microscopy. The optical property and the band gap energy of the as prepared samples were evaluated from UV-Vis absorption spectroscopy. When compared to SiC and PVB/SiC, boron doped SiC and its PVB composite exhibited enhanced photocatalytic activity toward the model dye (methylene blue) degradation owing to the effective separation of the photoinduced electron-hole pair on the photocatalyst nanofibers.

Moisture absorption characteristics and effects on mechanical properties of Kolon/epoxy composites

Para-aramid fibers (Kolon) are high performance polymeric fibers characterized by their high tenacity and impact resistance. They are used for the soft body armor structures in ballistics. In this study, the testing specimens were made from multilayered Kolon fabrics impregnated with epoxy resin where silicon carbide (SiC) microparticles or SiC nanofibers were added as reinforcement. The laminated composite samples were fabricated by hot compression and curing of epoxy resin.The tensile and impact strengths of the untreated specimens were compared with the ones that underwent water absorption in duration of 72 h (immersion or humidity) followed by desorption. The immersion of the specimens in water and exposure to high humidity (70%) were performed according to the ISO 62 standard while the tensile test was carried out in accordance with the ASTM D 3039 standard. In the end, the tensile test simulation of the laminated composite by using software Abaqus® was accomplished.

Rational design of meso-/micro-pores for enhancing ion transportation in highly-porous carbon nanofibers used as electrode for supercapacitors

Carbon nanofiber has been one of the promising electrode materials for supercapacitors. It is desirable but still challenging to optimize meso-/micro-pore ratio and configuration while achieving a high specific surface area in carbon nanofibers. Here, we present the design and preparation of carbon nanofiber mats with both high specific surface area and rational meso-/micropore configuration by electrospinning tetraethyl orthosilicate (TEOS)/phenolic resin (PR)/polyvinylpyrrolidone (PVP)/F127 blend solution, followed by carbothermal reduction, removal of carbon and chlorination. Silicon carbide nanofibers constructed by regulatable secondary nanostructure were achieved by adjusting TEOS content in the spinning solution, derived from which microporous carbon nanofibers with considerable mesopores (60–70% in mesoporosity), diverse secondary nanostructure (24–44 nm), and high specific surface area (1765–1890 m2 g−1) were prepared. The formation mechanism of the diverse secondary nanostructure in carbon nanofiber was proposed. The carbide-derived carbon nanofibers showed an excellent specific capacitance (316 F g−1 at 0.1 A g−1) and high-rate capability (186 F g−1 at 100 A g−1) due to the enhanced ion transportation, which was achieved by shortening micropore channels and offering convenient mesoporous channel towards microporous domains.

Self-Propagating High-Temperature Synthesis of Silicon Carbide Nanofibers

Self-Propagating High-Temperature Synthesis of Silicon Carbide Nanofibers

Features of Synthesizing Ceramic Composites Discretely Reinforced by Carbon Fibers and SiC Nanowires Formed in situ in the Combustion Wave

A new method is proposed for the engineering of SiC-based ceramic-matrix composite materials strengthened by discrete carbon fibers and single-crystal silicon carbide nanowires. Depending on the macrokinetic characteristics of the combustion process, either diffusion layers, particles of silicon carbide, or silicon carbide nanowires with a diameter of 10–50 nm and a length of 15–20 μm can be formed on the surface of carbon fibers. The sequence of chemical transformations and structure formation in the combustion wave of Si–C–C2F4 and Si–C–C2F4–Ta mixtures was studied. Silicon carbide nanowires formed in the combustion wave had high crystallinity and a defect-free TaSi2/SiC interface. The misorientation of the lattices at the interface is about 6%. Nanowires are able to relax the mechanical stresses during growth via the rotation along the growth direction. The optimal combustion temperature for the growth of silicon carbide nanofibers is 1700 K at a ratio of C2F4 : C = 2. The lower temperature threshold for the growth of silicon carbide nanowires is caused by a decrease in the yield of reactive fluorides, while the upper-temperature threshold is caused by a failure of the adsorption blocking mechanism on the surface of the nanofibers and the destabilization of the TaSi2 + Si eutectic droplet. Composites with a SiC–TaSi2 ceramic matrix and a relative density of 98%, a hardness of 19 GPa, a flexural strength of 420 MPa, and fracture toughness of 12.5 MP m1/2 were obtained by hot pressing. An increase in the strength of the carbon fiber-matrix interface has manifested in the suppression of carbon fiber pull-out from the matrix.

Excavating the unique synergism of nanofibers and carbon black in Natural rubber based tire tread composition

AbstractThe article portrays the synergistic reinforcement of new generation nanofillers such as silicon carbide nanofibers (SiCs), carbon nanotubes (CNTs), and graphite nanofibers (GNFs) when used along with carbon black (CB) in a typical tire tread composition. The unique synergism in these composites, which were fabricated by a liquid phase mixing method, was reflected in their enhanced failure resistance and dynamic mechanical properties. At 4 phr loading of the nanofiber, the tensile strength, tear strength, modulus at 300% elongation, storage modulus, rolling resistance, and abrasion resistance were improved by 29, 45, 36, 110, 15, and 14%, respectively. The role of nanofibers in the development of a hybrid microstructure was investigated by scanning and transmission electron microscopy. Tribological characteristics were studied using a Laboratory Abrasion Tester (LAT 100), and the abrasion loss of the samples was correlated with energy dissipation occurring during the process. The fatigue properties indicated the ability of the CB‐nanofiber dual filler system to arrest crack growth. The study also serves to establish a correlation between the wear loss and fatigue properties of the hybrid nanocomposites containing different fibrous nanofillers. A mechanism of reinforcement by hybrid fillers is proposed.

Self-propagating high-temperature synthesis of silicon carbide nanofibers

The article presents the results of studies into the gas-phase synthesis of silicon carbide fibers using silicon powder, polytetrafluoroethylene (PTFE) energy additive and polyethylene (PE) powder by self-propagating high-temperature synthesis (SHS). Stoichiometric mixtures were used for experiments. Green mixture components were mixed in a 3 liter drum with tungsten carbide balls for 30 min. The green mixture weight was 500 g. Experiments were conducted in the SHS-30 industrial reactor. Silicon + PTFE mixture combustion was accompanied by a rapid increase in pressure from 0.5 to 4.0 MPa in less than 1 s, and a relatively rapid pressure drop to 1.5 MPa in 1.5 min. The combustion rate was more than 50 cm/s. It was established that there was a spread of the mixture components during the combustion due to the high combustion rate and intense gas emission. A cottonlike material of light blue color was obtained; it consisted of 100-500 nm thick silicon carbide fibers. The maximum pressure in the reactor reached 3.1 MPa in 1 s during the silicon + PTFE + PE combustion and then decreased to 1.5 MPa in 3 min. The combustion rate was about 40 cm/s. The entire volume of the reactor was filled with blue-grey cotton-like silicon carbide and SiC powder with equiaxed 0.5-3,0 μ m particles merged into conglomerates. Needle-like silicon crystals were formed in the transition layer between the powder and silicon carbide fibers. The results of experiments proved the possibility of obtaining silicon carbide nanofibers in relatively large quantities during the combustion of exothermic mixtures.

Fabrication of lightweight and porous silicon carbide foams as excellent microwave susceptor for heat generation

Lightweight and porous silicon carbide (SiC) foams due to its outstanding properties have attracted attention by many researchers and industries and are a well-studied material for microwave absorption. In this paper, SiC foam has been synthesized from the reaction of phenolic resin and silicon powder by replica method using polyurethane (PU) foam followed by heat treatment (sintering) at a higher temperature for formation into SiC. SiC foams were also modified by incorporating different microwave absorbing additives such as ZrO2, Fe3O4, and NiO. Further, SiC foams were also modified with SiC nanofibers by the sol-gel process. All SiC foams including as such and modified with additives were studied probably for time for generation of heat by self-heating properties on radiating the samples under microwave of frequency 2.45 GHz in a furnace. The ZrO2–SiC foam modified with SiC nanofibers was found to be the best sample and exhibited a temperature of 1130 °C in 480 s.

Features of synthesizing ceramic composites discretely reinforced by carbon fibers and SiC nanowires formed in situ in the combustion wave

A new method is proposed for the engineering of SiC-based ceramic-matrix composite materials strengthened by discrete carbon fibers and single-crystal silicon carbide nanowires. Depending on the macrokinetic characteristics of the combustion process, either diffusion layers, particles of silicon carbide or silicon csrbide nanowires with a diameter of 10–50 nm and a length of 15–20 μm can be formed on the surface of carbon fibers. The sequence of chemical transformations and structure formation in the combustion wave of Si–C–C 2 F 4 and Si–C–C 2 F 4 –Ta mixtures was studied. Silicon carbide nanowires formed in the combustion wave had high crystallinity and a defect-free TaSi 2 /SiC interface. The misorientation of the lattices at the interface is about 6 %. Nanowires are able to relax the mechanical stresses during growth via the rotation along the growth direction. The optimal combustion temperature for the growth of silicon carbide nanofibers is 1700 K at a ratio of C 2 F 4 : C = 2. The lower temperature threshold for the growth of silicon carbide nanowires is caused by a decrease in the yield of reactive fluorides, while the upper temperature threshold is caused by a failure of the adsorption blocking mechanism on the surface of the nanofibers and the destabilization of the TaSi 2 + Si eutectic droplet. Composites with a SiC–TaSi 2 ceramic matrix and a relative density of 98 %, a hardness of 19 GPa, a flexural strength of 420 MPa, and a fracture toughness of 12.5 MPa·m 1/2 were obtained by hot pressing An increase in the strength of the carbon fiber-matrix interface has manifested in the suppression of carbon fiber pull-out from the matrix.

NATURAL RUBBER NANOCOMPOSITES BASED ON NEW FIBROUS NANOFILLERS WITH IMPROVED BARRIER PROPERTIES FOR USE IN TIRE INNERLINER APPLICATIONS

ABSTRACT Hybrid nanocomposites were prepared by predispersion of new nanofibers such as aramid nanofibers, carbon nanotubes, silicon carbide nanofibers (SiC), cellulose nanofibers, and graphite nanofibers in natural rubber (NR) latex prior to melt mixing in an internal mixer to ensure the exquisite dispersion of nanofibers in NR. The competency of these nanofibers in reinforcing NR as well as enhancing its barrier properties has not been widely investigated. The fabricated nanocomposites showed enhanced curing as well as mechanical and dynamic mechanical properties. Morphology of the composites was analyzed through electron microscopy. The increase in tortuosity created by the presence of the hybrid filler system consisting of carbon black and nanofibers was studied using permeability models. At higher tearing energies, it was seen that the nanofiber-reinforced composites showed comparable crack growth properties; however, at lower energies, the fabricated composites exhibited higher crack propagation rates compared with the control compound when studied using a tear fatigue analyzer. The improved mechanical, dynamic mechanical, and barrier properties along with comparable fatigue crack growth properties offer an opportunity to apply these systems in high-end applications such as a thinner tire inner liner with a higher NR blend ratio, which can result in improved processability and reduced hysteresis, fuel consumption, and cost.

Improving ultraviolet light photocatalytic activity of polyaniline/silicon carbide composites by Fe‐doping

ABSTRACTIt was aimed to prepare polyaniline (Pani) composites, including silicon carbide (SiC) nanofibers doped with iron (Fe) ions. The Fe‐doping of SiC was performed to enhance the photocatalytic activity of the composites through the separation of photoexcited mobile charge carriers. For comparison purposes, Pani composites were also prepared with undoped SiC nanofibers. The composite samples were characterized by FTIR, XRD, SEM, EDX, and UV–Vis spectroscopies. Experiments on photocatalytic degradation of methylene blue under ultraviolet light irradiation revealed that Pani/SiC‐Fe composites exhibited higher photocatalytic activity when compared with Pani/SiC composites. Almost 22% dye removal was obtained within 300 min with the Pani composite, containing 15 wt.% SiC‐Fe. FTIR, XRD, SEM, EDX, and UV–Vis spectroscopies demonstrated that SiC nanofibers were successfully doped with iron ions and incorporated into the polyaniline matrix. The original aspect of this study was to research the photocatalytic activity of polyaniline composites containing Fe‐doped SiC nanofibers. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48524.

Friction and wear behaviors of SiCNF modified carbon/carbon sealing materials

Silicon carbide nanofibers grew on the surface of carbon fibers of a unidirectional carbon preform by CCVD and then chemical vapor infiltration was used to densify the preform to obtain SiCNF-C/C composites. The effects of Silicon carbide nanofibers on friction and wear properties of SiCNF-C/C composites were deeply analyzed. Results show that the friction and wear properties of SiCNF-C/C composites are well improved due to the melioration of microstructure after modified by SiCNFs. The friction coefficient of SiCNF-C/C composites is more stable along with friction speed than that of C/C composites, it maintains high even at high friction speed. The wear of SiCNF-C/C composites is much lower and more stable than that of C/C composites with the increase of friction speed, especially in the vertical direction.