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In the present study, a polymer‐derived silicon oxycarbide (SiOC) ceramic layer has been coated on stainless steel 304 (SS304) to improve corrosion resistance in a seawater environment. The surface of SS304 is dip‐coated with vinyl‐functionalized polysiloxane, followed by pyrolysis under argon at 800°C to obtain SiOC layer with a thickness of about 1 μm after two‐fold coating/pyrolysis steps. Structural characterization of the samples was performed by fourier transform infrared (FTIR), X‐ray diffraction, Raman spectroscopy, and scanning electron microscopy. Electrochemical characterization of SS304 and SiOC‐coated SS304 is performed in 0.6 M NaCl solution. Potentiodynamic polarization measurements showed improved corrosion resistance of SiOC‐coated SS304 with a very low corrosion current density of 4.14 × 10−9 A/cm2 whereas for uncoated SS304 corrosion current density of 4.56 × 10−7 A/cm2 was measured. Electrochemical impedance spectroscopic study confirmed superior corrosion resistance behavior of SiOC‐coated SS304 over uncoated SS304. [ABSTRACT FROM AUTHOR]

We present here the single-source-precursor synthesis of Fe3Si and Fe5Si3-containing SiOC ceramic nanocomposites and investigation of their magnetic properties. The materials were prepared upon chemical modification of a hydroxy- and ethoxy-substituted polymethylsilsesquioxane with iron (III) acetylacetonate (Fe(acac)3) in different amounts (5, 15, 30 and 50wt%), followed by cross-linking at 180°C and pyrolysis in argon at temperatures ranging from 1000°C to 1500°C. The polymer-to-ceramic transformation of the iron-modified polysilsesquioxane and the evolution at high temperatures of the synthesized SiFeOC-based nanocomposite were studied by means of thermogravimetric analysis (TGA) coupled with evolved gas analysis (EGA) as well as X-ray diffraction (XRD). Upon pyrolysis at 1100°C, the non-modified polysilsesquioxane converts into an amorphous SiOC ceramic; whereas the iron-modified precursors lead to Fe3Si/SiOC nanocomposites. Annealing of Fe3Si/SiOC at temperatures exceeding 1300°C induced the crystallization of Fe5Si3 and β-SiC. The crystallization of the different iron-containing phases at different temperatures is considered to be a consequence of the in situ generation of a Fe–C–Si alloy within the materials during pyrolysis. Depending on the Fe and Si content in the alloy, either Fe3Si and graphitic carbon (at 1000–1200°C) or Fe5Si3 and β-SiC (at T >1300°C) crystallize. All SiFeOC-based ceramic samples were found to exhibit soft magnetic properties. Magnetization versus applied field measurements of the samples show a saturation magnetization up to 26.0emu/g, depending on the Fe content within the SiFeOC-based samples as well as on the crystalline iron silicide phases formed during pyrolysis. [ABSTRACT FROM AUTHOR]

Low-layered, transparent graphene is accessible by a chemical vapor deposition (CVD) technique on a Ni-catalyst layer, which is deposited on a <100> silicon substrate. The number of graphene layers on the substrate is controlled by the grain boundaries in the Ni-catalyst layer and can be studied by micro Raman analysis. Electrical studies showed a sheet resistance ( Rsheet) of approximately 1435 Ω per □, a contact resistance ( Rc) of about 127 Ω, and a specific contact resistance ( Rsc) of approximately 2.8×10−4 Ω cm2 for the CVD graphene samples. Transistor output characteristics for the graphene sample demonstrated linear current/voltage behavior. A current versus voltage ( Ids- Vds) plot clearly indicates a p-conducting characteristic of the synthesized graphene. Gas-sensor measurements revealed a high sensor activity of the low-layer graphene material towards H2 and CO. At 300 °C, a sensor response of approximately 29 towards low H2 concentrations (1 vol %) was observed, which is by a factor of four higher than recently reported. [ABSTRACT FROM AUTHOR]

Abstract: Mesoporous SiOC/TiO2 and SiOC/N-doped TiO2 (nitrogen-doped TiO2) ceramic composites were prepared by the incorporation of TiO2 (containing 65wt.% anatase and 35wt.% rutile) and N-doped TiO2 powders into vinyl-functionalized polysiloxane polymer followed by pyrolysis at 700–900°C for 2h in argon atmosphere. The N-doped TiO2 powders were obtained by ammonolysis of commercial TiO2 nanopowders. The resulting samples were characterized by means of X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy and nitrogen physisorption. The specific surface area (S BET) values of the as-prepared SiOC ceramic and SiOC/TiO2 and SiOC/N-doped TiO2 ceramic composites decreased with increasing the pyrolysis temperature due to a gradual collapse of small pores. A transformation from microporous SiOC ceramic (pore-size <2nm) to mesoporous SiOC/TiO2 and SiOC/N-doped TiO2 ceramic composites (pore-size ∼4nm) was analyzed. Adsorption and photocatalytic activity of the resulting samples were evaluated by measuring the decrease in concentration of methylene blue (MB) after adsorption in the dark and photodegradation reaction under UV–vis light irradiation, respectively. Pure microporous SiOC ceramic showed no significant adsorption as well as photocatalytic activity for MB because of its high microporosity and low solid acidity, respectively, whereas mesoporous SiOC/TiO2 and SiOC/N-doped TiO2 ceramic composites exhibited higher adsorption and photocatalytic activities. The photodegradation rate constant k(×10−3 min−1) of the samples increased in the following order: 1.3 for SiOC ceramic <2.2 for SiOC/TiO2 <3.4 for SiOC/N-doped TiO2. The highest k for the SiOC/N-doped TiO2 ceramic composite is discussed in terms of the change of the electronic structures and crystallinity of N-doped TiO2 if compared with pure TiO2. These polymer-derived ceramic composites can be applied for the purification of water contaminated with organic dyes without the need for hydrogen peroxide. [Copyright &y& Elsevier]

Highlights: [•] Nitrogen-doped porous TiO2 monolith was fabricated by sol–gel and ammonolysis. [•] Nitrogen-doped porous TiO2 monolith has macrochannels with the diameter of 1.5–3.0μm. [•] The O Ti N bonds were formed after nitrogen doping into the lattice of TiO2. [•] The photocatalytic activity of the samples was investigated under visible light. [•] About 50% of Rhodamine B was degraded by N-doped TiO2 porous monolith within 120min. [ABSTRACT FROM AUTHOR]

Abstract: Macroporous TiO2 monolith was first prepared by the sol–gel method and then macroporous TiO2–SrTiO3 heterostructured monolith was obtained by the impregnation of the as-prepared macroporous TiO2 monolith in the strontium-containing aqueous solution followed by calcination at different temperatures. The formation of SrTiO3 crystals in the TiO2 network was confirmed by X-ray diffraction and electron microscopy analyses. Macroporous structure of the heterostructured monolith was analyzed by mercury porosimetry. The photocatalytic activity of macroporous TiO2–SrTiO3 heterostructured monolithic photocatalyst was evaluated for the photodegradation of Rhodamine B over the samples under visible light irradiation. The obtained results reveal that the samples show an enhanced photocatalytic activity for the degradation of organic dye molecules. [Copyright &y& Elsevier]

Low-layered, transparent graphene is accessible by a chemical vapor deposition (CVD) technique on a Ni-catalyst layer, which is deposited on a <100> silicon substrate. The number of graphene layers on the substrate is controlled by the grain boundaries in the Ni-catalyst layer and can be studied by micro Raman analysis. Electrical studies showed a sheet resistance (R(sheet)) of approximately 1435 Ω per □, a contact resistance (R(c)) of about 127 Ω, and a specific contact resistance (R(sc)) of approximately 2.8×10(-4)  Ω cm(2) for the CVD graphene samples. Transistor output characteristics for the graphene sample demonstrated linear current/voltage behavior. A current versus voltage (I(ds)-V(ds)) plot clearly indicates a p-conducting characteristic of the synthesized graphene. Gas-sensor measurements revealed a high sensor activity of the low-layer graphene material towards H(2) and CO. At 300 °C, a sensor response of approximately 29 towards low H(2) concentrations (1 vol %) was observed, which is by a factor of four higher than recently reported., (Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)