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Continuous SiC fiber is a kind of high–performance ceramic fiber that combines many advantages, such as high strength, high modulus, high hardness and low density. It has excellent mechanical properties, high–temperature and oxidation resistance, which could be applied as essential reinforcement in advanced ceramic matrix composites (CMCs) in the fields of aerospace and advanced weaponry. Melt–spinnable polytitanocarbosilane (PTCS) is an important precursor, which can be used to prepare continuous SiC fibers through a precursor–derived method. In this work, low–softening–point polycarbosilane (LPCS) and tetrabutyl titanate were used to prepare polytitanocarbosilane with a ceramic yield of 67.5 wt% at 1000 °C. FT–IR, TGA, GPC, 1H NMR, 29Si NMR, and elemental analysis were used to analyze the composition and structure of the PTCS precursor. Finally, Si–C–Ti–B fibers with an average tensile strength of 1.93 GPa were successfully prepared by melt spinning, pre–oxidation, pyrolysis, and high–temperature sintering of the PTCS precursor. The strength retention rates were 71.5% and 79.8% after heat treatment at 1900 °C and 2000 °C under an argon atmosphere for 1 h, respectively. The strength retention rates of Si–C–Ti–B fibers are higher than those of commercial Hi–Nicalon fibers, Tyranno ZMI fibers and Hi–Nicalon S fibers. This work can lay a theoretical foundation and technical support for developing high-performance SiC ceramic fibers containing titanium and their ceramic matrix composites.

In this study, PyC coating with different thickness was prepared on SiC fibers via chemical vapor deposition method. Uncoated and PyC coated SiC fibers were heat treated in Ar atmosphere under different annealing condition. The effects of PyC coating on the mechanical properties of SiC fibers at room temperature were investigated. The morphology, composition, structure and mechanical properties of SiC fibers after high temperature treatment were also studied. The results showed that PyC coating could reduce the dispersion of tensile strength for SiC fibers. Weibull modulus increased from 4.19 (SiC fiber) to 5.59 (PyC700 fiber), while the tensile strength decreased a little with the increment of PyC coating thickness. Furthermore, PyC coating could remarkably retard Si sublimation from SiC fiber at high temperature. Uncoated SiC fiber was converted to porous pure-carbon fiber after being annealed at 2000 °C for 5 h, while PyC700 fiber still showed relative dense SiC core after the same treatment. To a certain extent, the inhibition ability was improved with increment of PyC coating thickness. In addition, PyC coated SiC fibers could maintain more tensile strength after being annealed at 1800 °C for 1 h. The tensile strength retention of uncoated SiC fiber was 27.3%, while that of PyC700 fiber could reach up to 43.2%.

A novel ternary layered ceramic of Y3Si2C2 was successfully in-situ synthesized on the surface of home-made third-generation KD-SA SiC fiber for the first time by molten salt method aimed at improving the electromagnetic wave (EMW) absorption. After in-situ synthesis of Y3Si2C2 ceramic layer on SiC fiber (SiCf/Y3Si2C2), significantly improved EMW absorption performance was obtained. The minimum reflection loss (RLmin) of −16.97 dB was reached in SiCf/Y3Si2C2 composites at the thickness of only 2.19 mm, and the effective absorption bandwidth (EAB) was up to 5.44 GHz (12.56–18 GHz) at a thin thickness of 2.64 mm. The improvement in EMW absorption of SiCf/Y3Si2C2 is mainly attributed to enhanced dielectric loss and conduction loss resulting from increased heterogeneous interfaces and multiple reflections and scattering originating from net structure. The SiCf/Y3Si2C2 could be a promising EMW absorber for application in high-performance EMW absorbing materials.

C/SiBCN composites are promising self-healing materials, which can be applied as structural materials in high-temperature oxidation environments in the aerospace industry; therefore, it is important to investigate their mechanical properties after oxidation treatment. In this study, C/SiBCN composites were oxidized at elevated temperature in 1200 °C-1700 °C in static air. The C/SiBCN composites demonstrated a desirable oxidation resistance at 1200 °C and 1600 °C. The flexural strength of the composites was retained at 168 MPa after static oxidation at 1200 °C for 30 min, owing to the low diffusion rate of oxygen into the composites. Even after an oxidation of 60 min, the strength was retained at 101 MPa. Furthermore, the strength of the composites was stable at approximately 130 MPa after oxidation at 1600 °C for 120 min, because of the formation of a dense oxide scale. The strength of C/SiBCN composites decreased at 1700 °C due to the interface reaction and oxidative damage of fibers. In 1200 °C-1500 °C, the carbon fiber in the composites was preferentially oxidized, and the strength of the composites decreased as the oxidation time increased.

On account of the excellent oxidation resistance of precursor-derived SiBCN ceramics, carbon-fiber-reinforced SiBCN (C/SiBCN) composites are increasingly being used in high-temperature aerospace applications. However, very few studies have investigated the high-temperature oxidation behavior of C/SiBCN composites for their application to high-heat engines. Herein, C/SiBCN composites prepared by precursor infiltration and pyrolysis were tested in static air up to an oxidation temperature of 1700 °C. The composites’ structural evolution after oxidation and their potential oxidation mechanisms were investigated in detail. The carbon fibers were preferentially oxidized at temperatures in the range of 1200–1500 °C and completely oxidized at 1500 °C. The oxidation of the fibers at 1500 °C resulted in the formation of abundant oxygen channels and consequently a high oxide scale growth rate of 5–7 μm2 h−1 and a large mass loss of 54.6 wt%. At elevated temperatures in the range of 1600–1700 °C, a dense SiO2 oxide layer was formed by the sacrificial oxidation of the SiBCN matrix. The oxidation rate of the composites was therefore controlled by the diffusion rate of oxygen through the protective SiO2 oxide layer and the weight loss of the composites decreased to 28.6% after oxidation at 1600 °C for 60 min. The structural integrity of the composites was maintained after long-term oxidation at 1600 °C.

Radioprotectors for acute injuries caused by large doses of ionizing radiation are vital to national security, public health and future development of humankind. Here, we develop a strategy to explore safe and efficient radioprotectors by combining Hantzsch’s reaction, high-throughput methods and polymer chemistry. A water-soluble polymer with low-cytotoxicity and an excellent anti-radiation capability has been achieved. In in vivo experiments, this polymer is even better than amifostine, which is the only approved radioprotector for clinical applications, in effectively protecting zebrafish embryos from fatally large doses of ionizing radiation (80 Gy X-ray). A mechanistic study also reveals that the radioprotective ability of this polymer originates from its ability to efficiently prevent DNA damage due to high doses of radiation. This is an initial attempt to explore polymer radioprotectors via a multi-component reaction. It allows exploiting functional polymers and provides the underlying insights to guide the design of radioprotective polymers., Nuclear technology has created a significant interest in developing radio-protectants. Here, the authors combine Hantzsch’s reaction with high-throughput techniques for the development of a polymer radio-protectant and demonstrate protection of cells and zebrafish embryos against ionizing radiation.

Soluble and meltable Zr-containing preceramic polymers were synthesized in this work by the polymerization of ZrCl4 and different diamines, followed by preparation of Zr(C, N) multinary ceramics via pyrolysis. The composition, structure and morphology were investigated by Fourier transform infrared spectroscopy, nuclear magnetic resonance, as well as thermogravimetric-mass spectrometry, X-ray diffraction, elemental analysis, scanning electron microscopy (SEM) and transmission electron microscopy. Results showed that although the precursor could be formed by the reaction between Zr–Cl and N–H bonds, the ceramic yield was low due to the release of NH3 and CH4 gases during the ceramization process. To improve the ceramic yield, allyl amine was applied to tailor the polymer structure. With allyl groups acting as the “bridge” during crosslinking process, the precursor had a higher ceramic yield of 62.5% and melting point of 280–300 °C with Zr content of 49.7 wt% in the derived Zr(C, N) ceramics. Annealing experiments in an inert atmosphere at temperatures in the range of 1200–1400 °C showed the transformation of the amorphous state to dense polycrystalline ceramics. When temperature was increased to 2000 °C, the ceramics got quite dense without obvious phase separation. The precursors could be applied as promising candidates for non-oxide ceramic matrix composites and fibers at ultra-high temperatures and even in harsh environments.

A novel preceramic polymer polyzirconocenyborazane (PZCBN) was synthesized by the polymerization of Bis(cyclopentadienyl)zirconium divinyl and borazine, introducing Zr, B, C, N together. The formation and concentration of elements Zr, C, B, N in the precursor and ceramic were detected through FTIR NMR, XRD, SEM and TEM. From the analysis, the Cp 2 Zr(CH˭CH 2 ) 2 and borazine linked together via the addition reaction between C˭C and B-H. And after pyrolysis at 1200 °C, the precursor turned to ZrC/ZrB 2 /BN composite ceramics, with a yield of 52 wt%. EDX resulted showed that the elements were well dispersed in the ceramics. According to SEM and TEM, the ceramic had a relatively dense structure with nano crystalline areas of ZrC embedded in the amorphous Zr-C-B-N matrix. TGA in air demonstrated that the ceramic had a favorable property on oxidation resistance.

A brand-new way to diverse Zr/Si/C/O preceramic polymers from dilithiozirconocene complex and chlorosilanes was designed for the first time. This simple route was fulfilled in normal pressure and at room temperature, without heating, cooling, pressurizing or electrolyzing. The pyrolysis of polymers and crystallization of polymer-derived Zr/Si/C/O ceramics were investigated by a combinational characterization of TGA, XRD, TG-FTIR, TG-GC-MS, SEM and EDS. By such polymers, Zr/Si/C/O ceramic foams with 3D networks were obtained at 1000 °C. The specific surface area of such ceramic foams was 78.18 m2/g, while the pure skeleton density and geometrical density were as low as 1.66 and 0.056 g/cm3. Interestingly, such ceramic foam showed fair thermal stability, whose cellular structure and mesoporous microstructure could maintain from 1000 °C to 1800 °C. Also, such non-ferrous materials performed attractive wave-absorbing properties at tunable frequencies from 15 GHz to 4 GHz, with maximum reflection loss of −39 dB (1000 °C) and −37 dB (1800 °C). These lightweight mesoporous Zr/Si/C/O ceramic foams with wave-absorbing and heat-resisting properties are promising candidates for high-temperature absorbents. Keywords: Zr/Si/C/O ceramics, Polymer-derived, Ceramic foam, Polyzirconocenesilane, High temperature resistance

In order to prepare ZrC-ZrB 2 nanocomposite ceramics with high temperature stability from single-source precursors, the reactions of ZrCl 4 , allyl amine, allyl-MgCl and borane were employed to synthesize suitable precursors. The meliorated ZrNCB precursor had favorable solubility and higher ceramic yield (68.8 wt%), which was then transformed to ZrC-ZrB 2 ceramics at different temperatures. The main phase of the ceramics was amorphous at 1000 °C. As the temperature increased, the amorphous phases started to crystallize, resulting in the appearance of ZrC and ZrB 2 peaks. The content of ZrC and ZrB 2 phases was relatively high in the nanocomposite ceramics at 1600 °C (over 80 wt%). The ZrC-ZrB 2 nanocomposite ceramics showed good high temperature stability up to 2000 °C. Oxidation test indicated that an oxide layer was formed on the ceramic surface at 1700 °C under air to prevent further oxidation of the ceramics. With excellent high temperature and oxidation resistances, the ZrC-ZrB 2 nanocomposite ceramics have potential application for advanced rocket engines and nuclear industry.

B4C ceramic is one of widely used ceramics with properties of low density, high hardness, high thermal-stability and high neutron absorption cross-section. However, the high melting point and high hardness of B4C make it difficult to be prepared as materials with complex shape. Precursor derived method is an effective approach to prepare special-shaped ceramics. In the early research of B4C ceramic precursors, highly toxic and unstable decaborane was generally used as the boron source material, and precursors were also unstable and difficult to synthesize. In this work, a new B4C precursor is designed and synthesized, and m-carborane, which has stable chemical properties and high thermal stability, is used as the boron source. Firstly, m-carborane is converted into lithium salt after removing active hydrogen by n-butyllithium. Then, catalyzed by Cu(I), the lithium salt reacts with m-chloroiodobenzene so that monomer, bis(3-chlorophenyl)-m-carborane, is prepared. The monomer is polymerized through Ullmann Coupling reaction at the present of Ni(0) catalyst and Zinc powder, and precursor poly[bis(3-chlorophenyl)-m-carborane] is finally synthesized. The precursor is stable at room temperature in air and soluble in Tetrahydrofuran, with Mw of 1013g/mol, and ceramic yield of 62.20% at 900°C in N2. The precursor pyrolytic product is composed of B4C and graphite after heat treated at 1600°C in inert atmosphere.

Millimeter-sized boron carbide ceramic hollow microspheres have promising practical application in the encapsulation of nuclear fusion materials in the field of inertial confinement fusion. However, the fabrication of millimeter-sized compact boron carbide ceramic hollow microspheres from poly(6-hexenyldecaborane) precursor has not been reported yet. In this work, poly(6-hexenyldecaborane)s with decaborane in the main chain and the branched chain, respectively, were synthesized using 6-CH2CH(CH2)4-B10H13 as the monomer. Furthermore, compact boron carbide ceramic hollow microspheres were fabricated by the combination of emulsification-solvent evaporation technique and precursor derived method. With smooth surface and good sphericity, the hollow ceramic microspheres had an average outer diameter of 1.0 mm and shell thickness ranging from 15 to 30 μm. Keywords: Boron carbide, Ceramic hollow microspheres, Precursor, Decaborane, Ceramization

Melt-spinnable polyaluminocarbosilane (PACS) is of importance as the precursor to prepare the Si–C–Al–O ceramic fibers, which can be employed for the preparation of SiC fibers with high tensile strength and good thermal stability. In this work, low-softening-point polycarbosilane (LPCS) was synthesized by pyrolysis of polydimethylsilane and applied to prepare PACS precursors with variable aluminum content by the reaction with aluminum(III) acetylacetonate. GPC, 1H NMR, UV–Vis, FT-IR, 29Si NMR, 27Al MAS NMR, TGA, and elemental analysis were used to analyze the composition and structure of the PACS precursors. Finally, Si–C–Al–O fibers were obtained successfully by melt-spinning, curing, and final pyrolysis of the precursors. The method demonstrated in this work can be further extended to synthesize other melt-spinnable metal-containing polycarbosilane (PMCS, M: Zr, Ti, Fe, Co, et.) of high ceramic yield and adjustable M content by reacting LPCS with other corresponding metal-containing compounds.

Aluminum-containing silicon carbide (SiC) fiber, such as Tyranno SA fiber, is the typical 3rd generation SiC fiber. Polyaluminocarbosilane (PACS) is the precursor of Al-containing SiC fiber. PACS was synthesized via elimination of HCl during the reaction between dimethyaluminium chloride ((CH 3 ) 2 AlCl) and polycarbosilane (PCS) in this work. Composition and structure of the as-synthesized PACS were characterized by elemental analysis, FT IR, GPC, and TG, respectively. The results showed that, the yield of the reaction was 72.5% and the reaction degree of Si–H bonds was 16.5%. The obtained PACS had melting point of about 218.8 °C, experimental formula as SiC 2.003 Al 0.023 O 0.048 H 3.713 , number average molecular weight M n of 1859, weight average molecular weight M w of 4895, polydispersity index ( M w / M n ) of 2.632. The molecular structure of PACS was similar to that of PCS. Four stages could be divided during pyrolysis process of PACS according to TG spectrum. The ceramic yield was found to be around 67.3% at 1000 °C in N 2 atmosphere. The PACS precursor is melt spinnable into flexible and uniform green fibers with the diameter about 12.6 μm.

Silicon carbide (SiC) has been considered a promising metal-free photocatalyst due to its unique photoelectrical properties and thermal/chemical stability. However, its performance suffers from the fast recombination of charge carriers. Herein, we report mesoporous SiC nanofibers with in situ embedded graphitic carbon (SiC NFs-Cx) synthesized via a one-step carbothermal reduction between electrospun carbon nanofibers and Si powders. In the absence of a noble metal co-catalyst, the hydrogen evolution efficiency of SiC NFs-Cx is significantly improved under both simulated solar light (180.2 μmol·g–1·h–1) and visible light irradiation (31.0 μmol·g–1·h–1) in high-pH solution. The efficient simultaneous separation of charge carriers plays a critical role in the high photocatalytic activity. The embedded carbon can swiftly transfer the photogenerated electrons and improve light absorption, whereas the additional hydroxyl anions (OH–) in highpH solution can accelerate the trapping of holes. Our results demonstrate that the production of SiC NFs-Cx, which contains exclusively earth-abundant elements, scaled up, and is environmentally friendly, has great potential for practical applications. This work may provide a new pathway for designing stable, lowcost, high efficiency, and co-catalyst-free photocatalysts.

Linear and star PVBCz-b-PDMAEMA block copolymers with different arm numbers and PDMAEMA block lengths were successfully synthesized via ATRP using the PVBCz homopolymers with a low degree of polymerization as macro-initiators and DMAEMA as the second monomer. The properties of different PVBCz-b-PDMAEMA block copolymers were investigated including ultraviolet-visible absorption, fluorescence emission, stimulus-response and fluorescence–stimulus-response. The experimental results showed that both the arm number and PDMAEMA segment length of the block copolymers had significant effects on the properties and the special fluorescence–stimulus-responses. The block copolymers represented lower phase transition temperatures with more arm numbers and longer PDMAEMA segment length. Moreover, the phase transition temperatures also changed with respect to different pH values of the solution. The fluorescence emission intensity and emission wavelength of block copolymers varied with different ratios of THF and water, pH value and temperature of the solution. The unique function could be adjusted to meet various specific practical demands by varying the arm number and the block length, which is of great research significance. The multifunction of the block copolymers endows them with a wide application prospect, especially in the field of sensors and intelligent photoelectric materials.

In this work, the preparation of polymer-derived Fe/Si/C ceramics was achieved by synthesis and pyrolysis of the preceramic hyperbranched polyferrocenylsilane. The Fe/Si/C ceramics obtained under various experimental conditions such as different pyrolytic temperatures, atmospheres and heating rates, were investigated by TG–MS, XRD, and XPS. Moreover, the magnetic properties of the ceramics were investigated by the vibrating sample magnetometer (VSM). Experimental results indicated that the pyrolysis of the preceramic polymer started above 250 °C and completed among 800–1000 °C. The crystallization of the pyrolytic product started at 500 °C. Besides the heat treatment temperature, the atmosphere and heating rate also played important roles in the composition and magnetic properties of the corresponding Fe/Si/C ceramics. Fe existed as α -Fe in ceramics sintered at 900 °C under N 2 and NH 3 atmospheres. However, the main components in ceramic product sintered under air were γ -Fe 2 O 3 and carbon. Although all of the three ceramic products sintered under different atmosphere were ferromagnetic with low remanent magnetization and coercivity, the ceramics sintered under NH 3 had the largest saturation magnetization. The saturation magnetization of the Fe/Si/C ceramics further ascended when fabricated under NH 3 with a slower heating rate, in which Fe existed as α -Fe, Fe 3 O 4 and γ ′-Fe 4 N.

The strategy of combining highly conductive frameworks with abundant active sites is desirable in the preparation of alternative catalysts to commercial Pt/C for the oxygen reduction reaction (ORR). In this study, N-doped graphene (NG) and carbon nanotubes (CNT) were grown in-situ on Co-containing carbon nanofibers (CNF) to form three-dimensional (3D) interconnected networks. The NG and CNT bound the interlaced CNF together, facilitating electron transfer and providing additional active sites. The 3D interconnected fiber networks exhibited excellent ORR catalytic behavior with an onset potential of 0.924 V (vs. reversible hydrogen electrode) and a higher current density than Pt/C beyond 0.720 V. In addition, the hybrid system exhibited superior stability and methanol tolerance to Pt/C in alkaline media. This method can be extended to the design of other 3D interconnected network architectures for energy storage and conversion applications.

As organometallic polymers containing Fe and Si in the main chain, hyperbranched polyferrocenylsilanes (PFS) have great potential to be Fe/Si/C ceramic precursors. In this study, three kinds of hyperbranched PFS with different crosslinking structures were synthesized by the reaction between ferrocenyl dilithium and one or two of trichloromethylsilane, dichlorodimethylsilane, and dichloromethylvinylsilane. The compositions and structures of these polymers were characterized by nuclear magnetic resonance spectroscopy, gel permeation chromatography, Fourier transform infrared (FT-IR) spectroscopy, and thermal gravimetric analysis. With respect to their ceramic yield and solubility, the potential of the obtained PFS to be used as ceramic precursors was evaluated. Moreover, ceramic microspheres with porous structures were obtained by pyrolysis of the hyperbranched PFS at different temperatures, which were characterized by FT-IR, X-ray diffraction, vibrating sample magnetometer, and element analysis. By introducing Fe to the original precursors, the ceramic microspheres exhibited catalytic properties with the presence of Fe nanoparticles on the surface of the internal pores. The porous Fe/Si/C ceramic microspheres made from the hyperbranched PFS have significant potential applications in the field of catalyst supports, energy storage, and gas separation, especially in harsh environments.

In the present study, ZrB 2 precursor which met the requirements of polymer infiltration-pyrolysis process, was synthesized and characterized. ZrB 2 precursor was synthesized with bis(cyclopentadienyl)zirconium dihydride (Cp 2 ZrH 2 ), borane-dimethyl sulfide complex (BH 3 ·S(CH 3 ) 2 ), and vinyltrimethylsilane ((CH 3 ) 3 Si(CH CH 2 ), VTMS). The molecular structure of the precursor, pyrolysis behavior, and the composition of the derived ceramics were investigated. The results showed that, the as-synthesized precursor was an oligomer based on Zr–H–B polycentric bridge bonds. The precursor was stable in an inert atmosphere. The ceramic yield of the precursor at 1200 °C was around 65.5% under N 2 atmosphere. The derived ceramics obtained under 1200 °C were composed of h-ZrB 2 , m-ZrO 2 and t-ZrO 2 . When the temperature was up to 1400 °C, peaks of ZrC emerged due to carbothermic reduction. m-ZrO 2 and t-ZrO 2 disappeared with the pyrolysis temperature above 1600 °C. The derived ceramics pyrolyzed at 1800 °C were composed of h-ZrB 2 and ZrC, and the former was the predominant phase.

Boron containing silicon-based ceramics with enhanced high-temperature stability have attracted great attention. An ultrafine and flexible silicon boron oxycarbide (SiBOC) fiber mat fabricated by electrospinning with a sol–gel system and subsequent pyrolysis is reported. The formation, composition and structure of the SiBOC fibers were studied by FT-IR, XRD, TG-MS, FE-SEM, HRTEM, XPS and MAS NMR. In comparison with the SiOC fibers, the SiBOC fibers showed better high-temperature stability. After being heated at 800 °C in air for 1 h, or immersed in 2 M NaOH and 1 M H2SO4 solutions for 24 h, the SiBOC fibers remained intact without of any detectable change. The SiBOC fibers illustrated superior amphiphilic affinity to water and xylene. Such a flexible SiBOC fiber mat may be of interest as a high-temperature catalyst support, LIB anode, capacitor, and so on.

A novel polyborosilazane (PBSZ) precursor was synthesized via single source precursor route, in which B existed in the form of B–N hexatomic ring in the main chain. The conversion from precursor to ceramic was completed at 800 °C with the ceramic yield of 48.5 wt%. The pyrolyzed SiBCN ceramics can remain amorphous up to 1600 °C. In view of above-mentioned properties, the polymer was employed to fabricate carbon fiber reinforced SiBCN matrix composites (C/SiBCN composites) via precursor infiltration and pyrolysis. The composites were dense with a density of 1.61 g cm−3 and an open porosity of 6.05% due to the effective infiltration of the precursor and an improved pyrolysis process. And the flexural strength and modulus were 324 MPa and 56.9 GPa, respectively.

Synthetic glycopolymers are important natural oligosaccharides mimics for many biological applications. To develop glycopolymeric drugs and therapeutic agents, factors that control the receptor-ligand interaction need to be investigated. A library of well-defined glycopolymers has been prepared by the combination of copper mediated living radical polymerization and CuAAC click reaction via post-functionalization of alkyne-containing precursor polymers with different sugar azides. Employing Concanavalin A as the model receptor, we explored the influence of the nature and densities of different sugars residues (mannose, galactose, and glucose) on the stoichiometry of the cluster, the rate of the cluster formation, the inhibitory potency of the glycopolymers, and the stability of the turbidity through quantitative precipitation assays, turbidimetry assays, inhibitory potency assays, and reversal aggregation assays. The diversities of binding properties contributed by different clustering parameters will make it possible to define the structures of the multivalent ligands and densities of binding epitopes tailor-made for specific functions in the lectin-ligand interaction. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2588-2597.

One-dimensional electrospun nanofibers have emerged as a potential candidate for high-performance oxygen reduction reaction (ORR) catalysts. However, contact resistance among the neighbouring nanofibers hinders the electron transport. Here, we report the preparation of interconnected Fe-N/C nanofiber networks (Fe-N/C NNs) with low electrical resistance via electrospinning followed by maturing and pyrolysis. The Fe-N/C NNs show excellent ORR activity with onset and half-wave potential of 55 and 108 mV less than those of Pt/C catalyst in 0.5 M H2SO4. Intriguingly, the resulting Fe-N/C NNs exhibit 34% higher peak current density and superior durability than generic Fe-N/C ones with similar microstructure and chemical compositions. Additionally, it also displays much better durability and methanol tolerance than Pt/C catalyst. The higher electroactivity is mainly due to the more effective electron transport between the interconnected nanofibers. Thus, our findings provide a novel insight into the design of functional electrospun nanofibers for the application in energy storage and conversion fields.

Porous SiC has attracted extensive attention for its wide applications, especially in harsh environment, due to its unique properties. In the present paper, novel macro-meso-microporous SiC ultrathin fibers (MMM-SFs) were synthesized through electrospinning process associated with polymer-derived ceramics route. And the porous structure in the SFs can be conveniently tailored by tuning the composition of the spinning solvents and the concentration of the precursor (polycarbosilane). The surface features and microstructures of the resultant MMM-SFs were characterized in detail. These fibers presented a high specific surface area of 86.1–128.2 m2 g−1. The formation mechanism of hierarchically porous structure was discussed as well. DMF played a critical role in forming macropores, while the decomposition of SiOxCy phase was responsible for the meso-/micropores. Our method utilized to synthesize hierarchically porous SFs is easily capable to design other ceramic fibers.