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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%.

In this work, a new approach to fabricate B4C/SiC ceramic hollow microsphere was established through combination of slurry-coating and precursor conversion method. Firstly, different slurries were prepared using modified B4C powder with addition of PCS and LPCS. Subsequently, slurry was coated on a POM microsphere, followed by crosslinking, POM decomposition and heat-treatment at 1100 °C. Finally, the B4C/SiC hollow microspheres with average diameter of 1.6–1.9 mm and thickness of 10–60 μm were obtained. The roughness (Ra) of outer surface was as low as 40.3 nm with high sphericity of 99.6%. Deoxidation was also explored by heat treatment at 1700 °C. The oxygen content was decreased from 11.06 wt.% to 0.37 wt.%, and crush load was promoted from 1.73 N to 4.50 N. The preparative method of B4C/SiC ceramic hollow microspheres in this work can be easily extended for large-scale production.

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.

Continuous graphene fibers (GFs) and graphene/SiC fibers (G/SiCFs) are fabricated from silicon carbide (SiC) fibers through vacuum annealing. The transformation gradually happens from the surface to the core of the fiber until complete conversion. Graphene sheets are in-situ formed after Si sublimation of 3C–SiC grains in the SiC fiber. Although porous structure is formed inevitably, the fiber shape is well maintained with circular cross section. The continuous GFs exhibit low density (1.63 g/cm3), excellent electric conductivity (53,900 S/m), high tensile strength (0.22 GPa) and elastic modulus (23 GPa, gauge length: 25 mm). Good properties can be probably attributed to interconnected graphene sheets. GFs have great electromagnetic interference shielding effectiveness of 62.8 dB, while G/SiCFs have outstanding microwave absorption properties. The minimum reflection loss (RL) value of −54.86 dB is achieved with sample thickness of 2.1 mm. When sample thickness is 1.4 mm, the effective absorption bandwidth of G/SiCFs can reach 4.4 GHz. Excellent flexibility is also possessed by a bundle of 1000 graphene filaments. Taking advantages of the facile conversion of silicon carbide fibers, the method demonstrated in this work can be further extended to prepare metal-containing GFs (Ti, Al, Zr, et.) and achieve large-scale production.

Layer-by-layer (LBL) assembly of concanavalin A (Con A), peanut agglutinin (PNA) plant lectins, and well-defined synthetic glycopolymers via their biological affinities have been prepared using a quartz crystal microbalance with dissipation monitoring (QCM-D). We demonstrate the use of mannose/galactose glycopolymers as lectin binders due to their selective binding to Con A/PNA, respectively. A detailed analysis of the adsorption processes and the adsorbed layer are provided and tuning the composition of multilayers using a series of well-defined glycopolymers differing only in the pendant sugar ratio is discussed.

The development of biofriendly UV-protective materials is important because current UV-screening inorganic nanoparticles and organic small molecules have potential safety risks. In this research, new polymers with dramatic UV-protective capabilities have been effectively prepared through post-polymerization modification (PPM) of a Biginelli-type copolymer. The resulting polymers are fluorescent because of the heterocyclic structures generated by PPM; thus, the endocytosis of these polymers could be easily detected. The conjugated polymers obtained by the PPM method present low cytotoxicity and are superior to the unconjugated original Biginelli-type polymer in preventing UV-induced DNA damage and cell necrosis. This work demonstrates that the combination of the Biginelli reaction with the PPM method is a viable strategy for developing biocompatible UV-protective polymers for practical applications.

The polymer-derived SiC fibers have broad application prospects in the fields of aerospace, nuclear industry and high-tech weapon. Oxygen plays an essential role in adjusting the composition, structure and tensile strength of SiC fibers. Our studies have found that introducing too much oxygen during air curing process will form the skin-core structure in nearly stoichiometric polycrystalline SiC fibers. In order to reveal the formation mechanism of the skin-core structure, gradient oxygen was introduced into the fibers. The morphologies, phase distributions and defects of the fibers were well characterized. By strictly controlling the introduction of oxygen, the polycrystalline product fiber exhibits intragranular fracture behavior and excellent high-temperature resistance. The retention rate of its tensile strength can reach up to 91% and 61% after exposure at 1800 °C for 1 h and 10 h, respectively. The present results give valuable insights into the structural optimization of the nearly stoichiometric polycrystalline SiC fibers.

Compared with the first and second generations SiC fibers, the third generation SiC fibers have obvious improvement in heat-resistance, oxidation-resistance and creep-resistance, which promote the development of SiCf/SiC composite materials. Therefore, the third generation SiC fibers have more advantages and broader prospects in engineering applications. In this paper, the fabrication and properties of the third generation SiC fibers are compared and discussed. The preparation processes of the third generation SiC fibers reinforced SiC matrix composites and their application in aeroengine and nuclear energy fields are summarized, while their future development is prospected as well.

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.

C/SiBCN composites with a density of 1.64 g/cm 3 were prepared via precursor infiltration and pyrolysis and the bending strength and modulus at room temperature was 305 MPa and 53.5 GPa. The precursor derived SiBCN ceramics showed good thermal stability at 1600 °C and the SiC and Si 3 N 4 crystals appeared above 1700 °C. The bending strength of the composites was 180 MPa after heat treatment at 1500 °C, and maintained at 40 MPa-50 MPa after heat treatment for 2 h at 1600 °C-1900 °C. In C/SiBCN composites, SiBCN matrix could retain amorphous up to 1500 °C and SiC grains appeared at 1600 °C but without Si 3 N 4 . The reason for no detection of Si 3 N 4 was that the carbon fiber reacted with Si 3 N 4 to form an interface layer (composed of SiC and unreacted C) and a polycrystalline transition layer (composed of B and C elements), leading to the degradation of the mechanical properties.

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.

Continuous SiC fibers have attracted increasing research interest for their significant application in aerospace and nuclear energy. Control of inhomogeneity and decrement of defects are crucial for improving the mechanical and high-temperature performance of SiC fibers. Thus an understanding of fine and detailed microstructural and microchemical distribution of SiC fibers is urgently needed. In the present work, the cross-sectional phase distributions, morphologies and defects of amorphous, non-stoichiometric and near-stoichiometric SiC fibers were well characterized. From surface to core, the amorphous and non-stoichiometric fibers exhibited uniform microstructures, but a gradient change along the radial direction was observed in the near-stoichiometric fiber. Nanosized SiC and turbostratic carbon (2–4 nm) were randomly distributed inside the amorphous fiber. A large amount of graphite surrounding SiC grains appears in the non-stoichiometric fiber which possess low strength and weak thermal stability. The near-stoichiometric fiber has transgranular fracturing, high strength and favorable thermal stability, and the graphite planes are turbostratic inside the fiber but straight on the surface. The results of both energy-dispersive X-ray spectrometry measurements and first-principles calculations demonstrate that Al atoms can occupy Si sites in the SiC grains. Our findings offer fine understanding for fabricating SiC fibers with superior properties.

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.

Boron carbide is one of the most widely used non-oxide ceramics as it possesses excellent physical and chemical properties. Much attention has been paid to prepare boron carbide ceramics via precursor derived method. In this work, poly(6-norbornenyldecaborane)- b -poly(6-cyclooctenyldecaborane) (PND- b -PCD) block copolymer was synthesized by the ruthenium-catalyzed ring-opening metathesis polymerization (ROMP) of 6-norbornenyldecaborane with 6-cyclooctenyldecaborane. The synthesized boron carbide preceramic polymer had good solubility and film-forming ability with a high ceramic yield of 75% at 850 °C. TGA, XRD and TG-IR-GC–MS were used to investigate the ceramization process of the precursor. Boron carbide ceramic foams were prepared by the precursor via replicating polyurethane foam template. The component, crystalline and morphology were investigated in detail. The ceramic foams showed a good high temperature performance and could keep their structure even up to 1800 °C.

Precursors for Zr/Si/C multiphase ceramics were synthesized by the reactions of dilithiozirconocene complex with dichlorodimethylsilane, methyltrichlorosilane and dichloromethylvinylsilane, respectively. The precursor-to-ceramic process of the precursor was investigated by TG-GC–MS and TG-FTIR analyses, confirming a complete transformation from organometallic polymers into ceramics below 800 °C. Annealing experiments of the derived ceramics at temperatures from 1000 °C to 2000 °C indicated the crystallization from ZrSiO 4 , ZrO 2 to ZrC. Furthermore, micrometer-sized Zr/Si/C ceramic microspheres were successfully fabricated from the precursor at 1000 °C, showing surface morphology like wrinkled pea. According to the XRD, HRTEM and XPS analyses, such multiphase ceramic microspheres consist of ZrSiO 4 , ZrO 2 , and amorphous SiO x C y . Interestingly, the ceramic microspheres performed satisfactory electromagnetic wave absorbing capacity with the RL max reaching −34 dB, which could be potential candidates for electromagnetic micro-devices.

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.

SiC fibers have been intensively developed for application in advanced aerojet engines, stationary gas turbines and nuclear reactors of the future. In this work, SiC fibers with controllable carbon-rich layer were prepared by sintering under vacuum, which could be attributed to the release of gaseous silicon under vacuum at high temperature. The thickness of the carbon-rich layer on the fiber surface could be adjusted by changing the sintering temperature. Moreover, the carbon-rich layer was well distributed on the fiber surface, combining closely with the interior of the fiber. The as-prepared SiC fibers had high tensile strength and relatively low elastic modulus, which was favorable for weaving into different fabrics. Furthermore, the fibers also exhibited excellent ultra-high temperature resistance due to the presence of carbon-rich layer on the surface, which was better than that of the Hi-Nicalon and Hi-Nicalon S fibers.

Due to their fantastic mechanical and high-temperature resistant properties, SiC fibers with electrical resistivity of different orders of magnitude are of great interest for the fabrication of advanced composites with electromagnetic wave absorbent performance as both structural and functional materials. On the basis of well-developed route to prepare SiC fibers, in this work, we demonstrated a facile strategy to fabricate SiC fibers with electrical resistivity of 10−1–106 Ω cm by simply employing hydrogen and ammonia as the reactive atmospheres. The SiC fibers with different electrical resistivity had favorable morphologies, with uniform elemental distribution and stable C/Si ratio towards the fiber interior. Moreover, these fibers exhibited excellent mechanical strength and high temperature performance. Due to the innovative strategy, convenient operation and scalable preparation, the method in this work can be further extended to prepare SiC base fibers with adjustable electrical resistivity from other precursors.

Chemotherapy has contributed greatly in clinical anti-tumor treatment. However, the traditional method of drug delivery by intravenous injection has several drawbacks, such as low delivery efficiency, high toxicity and frequent pain caused by injection. To overcome these defects, intra-tumor injection has been proposed in recent years, and the development of suitable carriers to locate the drug at the desired position for optimum dispersal is crucial to realize the superiority of intra-tumor injection. Herein, we report the application of a chitosan-based self-healing hydrogel, constructed through Schiff's bases, as an injectable drug carrier for in vivo intra-tumor therapy. This smart carrier could deliver highly concentrated anti-tumor drug (Taxol) to the desired position (human hepatocarcinoma tumor) for steady in situ release at a safe level. The self-healing drug carrier could adapt to the intra-tumor structure and regenerate as a whole, thus avoiding the fast leak of loaded drug, leading to admirable therapeutic effects compared with controls (direct injection of drug solution or use of non-self-healable thermal-sensitive hydrogel as the drug carrier). Due to its excellent biocompatibility and high operability, this injectable self-healing hydrogel might be a promising drug carrier for tumor chemotherapy and other medical applications.

ZrC-SiC multiphase ceramics are the most promising candidates as ultra high temperature ceramics for aerospace applications. In this work, preceramic polymers with tunable compositions have been synthesized by hydrosilylation reactions. FTIR and NMR spectra illustrate that the Zr N bonds are formed by Zr Cl and N H replacement for an incomplete extent. Then Grignard reagent (allyl-MgCl) is used to consume the residue Zr Cl bonds and tailor the structure of the precursors. The meliorated ZrNCSi precursors have higher ceramics yields and good solubility. Annealing experiments of the derived ZrC-SiC ceramics in an inert atmosphere at temperatures in the range of 1400–2000 °C show good high temperature resistance. The precursor-derived ZrC-SiC multiphase ceramics get dense with well dispersed nano ZrC crystallites when temperature rises. Oxidation test indicates that the ceramics have postponed oxidation process at low temperature and could keep stable at high temperature (1700 °C) with the formation of oxidation layer at the surface.

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

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.

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.

Increasing demands for detection of harmful gases in harsh environments have stimulated considerable efforts to develop a novel gas sensor with high sensitivity, superior thermal/chemical stability and fast response/recovery rate. In this paper, we report the vertical growth of ultrathin SnO2 nanosheets (SnO2 NSs) on quasi-one-dimensional SiC nanofibers (SiC NFs) forming a hierarchical architecture via a simple hydrothermal method. In comparison to pure SnO2 NSs, the SnO2 NS@SiC NF hierarchical composite shows an ultrafast response/recovery rate, high sensitivity, and simultaneously excellent reproducibility to various target gases including ethanol, methanol, hydrogen, isopropanol, acetone and xylene, even at high temperature. The response times are less than 5 s with corresponding recovery times

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.

B, N-codoped carbon nanofibers were massively prepared by heat treatment of electrospun carbon nanofibers with the mixture of boric acid/urea in N 2 (BNC f -N) and subsequently activated in NH 3 (BNC f -NA). The directly electrospun self-standing 3D non woven structure with void spaces between each fiber facilitates the mass transport of reactant and resulted molecules. Further NH 3 activation gives BNC f -NA a high surface area of 306.3 m 2 g −1 with micro/mesoporous structure, providing abundant passageway for proton transfer. Simultaneously, NH 3 activation also realizes the optimization of surface functionalities, such as more B–N–C and pyridinic-N. These intriguing features render BNC f -NA excellent catalytic behavior with nearly four-electron oxygen reduction reaction (ORR) process in alkaline media, especially much better stability and methanol tolerance than the commercial Pt/C catalyst. Our work provides a large-scale preparation method for efficient metal-free catalysts toward ORR, thus further intensifying the commercial application of fuel cells.

A high throughput (HTP) system has been developed to exploit new functional polymers. We synthesized 25 monomers in a mini-HTP manner through the tricomponent Biginelli reaction with high yields. The starting materials were five aldehydes extracted from essential oils. The 25 corresponding polymers were conveniently prepared via mini-HTP radical polymerization initially realizing the benefit of HTP methods to quickly fabricate sample libraries. The distinct radical scavenging ability of these Biginelli polymers was evaluated through a HTP measurement to choose the three best radical scavengers. This confirms the superiority of the HTP strategy to rapidly collect and analyze data. The selected polymers have been upgraded and screened according to different requirements for biomaterials and offer water-soluble and biocompatible copolymers that effectively protect cells from the fatal UV damage. This research is a straightforward way to establish new libraries of monomers with abundant diversity. It offers polymers with interesting functionalities. This suggests that a broader study of multicomponent reactions and HTP methods might be useful in many interdisciplinary fields. To the best of our knowledge, this is the first report of a HTP study of the Biginelli reaction to develop a promising polymeric biomaterial, which might have important implications for the organic chemistry and polymer communities.

Modification of material surfaces with polymers is an effective method to develop applicable polymer-material composites. Recently, multicomponent reactions (MCRs) have found their roles in advanced polymer chemistry and applied in surface modification. In this mini review, recent results of MCRs for surface modification are summarized, including the utilization of MCRs as coupling tools to link polymers on material surfaces, and polymers containing multicomponent structures for surface modification. The unique properties of these polymer-material composites stemming from MCRs are introduced, and the preliminary applications of these composites are also discussed.

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. N,N′-dimethylformamide (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 of designing other ceramic fibers.

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.

Zirconium diboride (ZrB2) is one of the most important ultrahigh temperature ceramics (UHTCs). ZrB2 precursor was synthesized with bis(cyclopentadienyl)zirconium dihydride (Cp2ZrH2) and borane-dimethyl sulfide complex (BH3·S(CH3)2). The influences of molar ratio of reactants and reaction temperature on the solubility of the as-synthesized precursors were investigated. The molecular structure of the precursor, pyrolysis behavior, and the composition of the derived ceramics were investigated by X-ray photoelectron spectroscopy (XPS), Fourier Transformed Infrared Spectroscopy (FT IR), Raman Spectroscopy (RMS), 1H Nuclear Magnetic Resonance Spectroscopy (1H NMR), 11B Nuclear Magnetic Resonance Spectroscopy (11B NMR), Thermogravimetric-Mass Spectroscopy (TG-MS), X-ray Diffraction (XRD), and Scanning Electron Microscopy (SEM), respectively. The results showed that, the precursor was an oligomer based on Zr–H–B polycentric bridge bonds with molecular weight of 750 and formula as (Cp2Zr(BH4)2)3. The precursor would probably further polymerize under vacuum or at high temperature and lead to an insoluble polymer. The ceramic yield of the precursor at 1000 °C was around 66% under N2 atmosphere. After pyrolyzed at 1800 °C, the derived ceramics were composed of h-ZrB2, ZrC, and free carbon with a formula as ZrB1.38C2.18.