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Fe-modified SiOC ceramic microspheres with different Fe/Si ratio were synthesized by solvothermal method with vinyltriethoxysilane and ferrous acetylacetonate as precursors. Effects of Fe/Si molar ratio and pyrolysis temperature on structure of SiOC ceramics were investigated. The carbothermal reduction results in the transformation of Fe2O3 into Fe3O4 as elevation of temperature from 600 oC to 800 oC, and Fe and Fe3C are formed with further increase the temperature to 1000 oC. Fe reacts firstly with free carbon (Cfree) to form Fe3C, and which preferentially reacts with SiC to form Fe3Si as the Fe/Si ratio is below (0.1) Only Fe3C phase retains with the Fe/Si ratio increases to (0.2) The transformation from Fe3C to Fe3Si takes precedence over conversion from Fe to Fe3Si. The Fe-incorporation reduces the phase separation temperature to 1000 oC. The graphitic carbon appears when the Fe/Si ratio is above 0.1, which is produced by the catalytic graphitization of Fe and conversion of Fe3C to Fe3Si. However, the Cfree content decreases as increase of pyrolysis temperature, structural transformation of Fe3C to Fe3Si is dominant for the formation of graphitic carbon. [ABSTRACT FROM AUTHOR]

The hollow SiOC ceramic microspheres were synthesized by using solvothermal method in NaHCO3 solution and followed by chemical etching with HF and NaOH solution. The oxygen-enriched unit of SiOC ceramics increases as increase of the pyrolysis temperature, and SiC nanowires are formed by carbothermal reduction reaction at 1400 °C. Although the C content increases after removing SiO2 by HF and NaOH solution, the etching effect of NaOH is inferior to that of HF etching. Independent of oxygen-rich units, SiOC ceramics with high graphitic C structure exhibit favorable structure and chemical durability. NaOH etching produces only mesopores and HF etching generates more micropores, both of which increases the specific surface area of SiOC ceramics as increase of pyrolysis temperature. Furthermore, HF etching results in the insertion of F element in SiOC ceramics and formation of F–Si bond. NaOH etching causes the residual Na element on surface of SiOC ceramics, which decreases the initial oxidation temperature of SiOC ceramics. The thermogravimetric analysis reveals that the oxidation resistance of SiC is superior to that of SiOC and C. [ABSTRACT FROM AUTHOR]

Mesoporous silicon oxycarbide (SiOC) ceramics were prepared by using the solvothermal method with vinyltriethoxysilane as precursor in hexamethylenetetramine solution, and N-doped porous carbon materials (SiOC-DC) were derived by selective etching with HF solution. SiOC ceramics prepared at 1200 °C exhibits the highest degree of graphitization, and the O/Si ratio in SiOC ceramics decreases as increase of the pyrolysis temperature. The phase separation generates limited SiC nanograins, and SiC nanowires is formed mainly by carbothermal reduction reaction. Besides the presence of mesopores, more micropores are generated in SiOC-DC when the pyrolysis temperature increases to 1400 °C. The N content of SiOC-DC increases as the elevation of pyrolysis temperature, and the N element exists mainly in the form of pyridinic N. As the adsorbent to remove phenol, the adsorption capacity of SiOC-DC increases not only with the elevation of pyrolysis temperature, but also with the increased initial concentration of phenol. SiOC-DC with the specific surface area of 1054.2 m2g−1, micropore volume of 0.48 cm3g−1 and N content of 3.5 wt% exhibits a good phenol adsorption performance, and the equilibrium adsorption capacity of HMTA-1400-HF is 72.3 mgg−1. [ABSTRACT FROM AUTHOR]

Highly microporous nitrogen-doped silicon oxycarbide (SiOC) derived materials were obtained by solvothermal process of vinyltriethoxysilane in urea solution and followed by HF etching. SiOC ceramics synthesized at 1200 oC exhibits good chemical durability in HF solution due to the formation of more SiO2C2 unit. Increasing the pyrolysis temperature not only increases the specific surface area and pore volume of SiOC derived materials, but also generates more pyridinic N and pyrrolic N functionalities. Furthermore, after HF etching, only incorporation of fluorine in SiOC ceramics (F − Si bond) and no C − F bond is found. The phase separation occurs during the pyrolysis process, and the generation of SiC is mainly caused by the carbothermal reduction reaction between SiO2 and free C (Cfree). The thermogravimetric analysis shows the oxidation resistance of SiC is superior to that of SiOC and C, while SiOC has better thermal stability than C. Both the high specific surface area, micropore volume and N-doping contribute the good supercapacitor performance. SiOC derived carbon materials with a high specific surface area of 1109.0 m2g− 1 and pore volume of 0.77 cm3g− 1 exhibit the specific capacitance of 272.2 Fg− 1 at the current density of 0.2 Ag− 1 in 6 M KOH aqueous electrolyte and good cycling stability of 89.7% retention after 10,000 cycles at 5 Ag− 1. In addition, the specific capacitance can reach up to 33.2 F g− 1 at 0.2 A g− 1 for a symmetrical supercapacitor, and a stable capacitance of 29.1 F g− 1 retains over 6000 cycles at 1 A g− 1. [ABSTRACT FROM AUTHOR]

The hollow mesoporous silicon oxycarbide (SiOC) ceramics without mixed Si−O−C units (SiO2/C composites) were synthesized through the solvothermal route in Na2CO3 solution, and porous carbon materials were prepared by HF etching. Amorphous SiO2 is transformed into cristobalite SiO2 as the increase in pyrolysis temperature from 1000 to 1400 °C, while the free C (Cfree) content decreases as the elevation of pyrolysis temperature. The carbothermal reduction reaction of SiO2 with Cfree not only results in the formation of SiC nanowires, but also further reduces the C content. However, after HF etching, the C content in carbon materials increases as elevation of pyrolysis temperature, and more micro-/mesopores are created by removal of SiO2. The microstructure and porosity of carbon materials are tailorable by simple changing the pyrolysis temperature. Furthermore, the HF etching results in the insertion of F only in SiO2 and which has no effect on the Cfree. The hierarchical porous structure in conjunction with surface oxygen-containing functional group make the carbon materials obtained at 1400 °C exhibit the good rhodamine B (RhB) and CO2 adsorption performance. The maximum RhB and CO2 adsorption capacity is 130.9 mgg−1 and 1.31 mmolg−1, respectively. [ABSTRACT FROM AUTHOR]

The effect of vinyltriethoxysilane (VTES) addition on the pyrolytic conversion of tetraethoxysilane (TEOS) based silica gel had been studied. Thermogravimetric analysis coupled with mass spectroscopy was carried out to study the thermal decomposition behavior of precursor gels. The ceramic yield of precursor gels was decreased with the increase of the VTES content. Si magic angle spinning nuclear magnetic resonance indicated that the incorporation of VTES into TEOS not only changed the composition and structure of precursor gels, but also increased carbon-enriched SiOC units of silicon oxycarbide ceramics during the pyrolysis conversion. The carbon content of SiOC ceramic was almost unchanged between 1,000 and 1,500 °C. However, the O/Si ratio of the silicon oxycarbide ceramic was reduced and the free carbon content was increased with the increasing molar ratios of VTES/TEOS. Moreover, the carbothermal reduction reaction led to the free carbon content decreased with the increase of the sintering temperature. [ABSTRACT FROM AUTHOR]

To explore the relationship between expressions of NF-κBp50, p53 and Bcl-2 in tissue of cervical cancer and human papillomavirus (HPV) infection. The expressions of NF-κBp50, p53 and Bcl-2 were detected using immuohistochemical staining in 46 specimens of cervical cancer and 26 specimens of normal cervical tissue. The infection of HPV DNA were determined by PCR. The expressions of NF-κBp50, p53 and Bcl-2 in tissue of cervical cancer were significantly higher than that in normal cervical tissue ( P<0.01), and the expressions of NF-κBp50 and p53 or Bcl-2 were closely related ( P<0.05). The expression of NF-κBp50 in HPV DNA positive group was significantly higher than that in HPV negative group ( P<0.05), but there were no significantly differences in the expressions of p53 and Bcl-2 between HPV DNA positive group and HPV negative group ( P>0.05). The expressions of NF-κBp50, p53 and Bcl-2 were significantly correlated with cervical carcinogenesis. NF-κBp50 may be activated by HPV infection. [ABSTRACT FROM AUTHOR]