Matches in SemOpenAlex for { <https://semopenalex.org/work/W333847420> ?p ?o ?g. }
- W333847420 abstract "This PhD thesis focuses on the synthesis and characterization of multifunctional polymer-derived SiOCN ceramics. The main objective is to synthesize N-doped silicon oxycarbides (SiOCs), to characterize their structure and their properties (mainly electrical conductivity) and correlate them with the presence of N in the structure. We also aim to understand how the architecture of the starting polymer can influence the retention of N into the SiOC structure. First, N-doped SiOC polymer precursors were synthesized via hydrosilylation reaction between Si-H groups present in a commercial polysiloxane (PHMS) and –CH=CH2 groups of three different commercial N-containing compounds. The structural characterization of as-synthesized preceramic polymer precursor was investigated by FT-IR and NMR. Thermal degradation was studied by TGA. The results show that the architecture of the polymer precursors plays an important role on the pyrolythic transformation. Then, SiOCN ceramics were obtained by pyrolysis of the as-synthesized polymer precursors in nitrogen atmosphere at various temperatures for 1h using a tubular furnace. Subsequently, high temperature structural evolution was studied using combined techniques such as XRD, FT-IR, NMR, Elemental analysis, and XPS. The obtained results show that the type of N-containing compounds impacts on the crystallization behavior of the final ceramics. Elemental analysis clearly indicates that N is present in the SiOC matrix and the degree of N retention after pyrolysis is related to the type of N-containing starting compounds. XPS data indicate that N-C bonds are present in the SiOC ceramic samples even if only N-Si bonds exist in the starting N-containing precursor. However, a larger fraction of N-C bonds is present in the final SiOCN ceramic when N atoms form bonds with sp2 carbon atoms in the pre-ceramic polymer. We have also studied electrical and optical properties of the SiOCNs. Electrical conductivity of the powdered ceramic samples was determined using powder-solution-composite technique. The results show an increase in room temperature AC conductivity of three orders of magnitude, from ≈10-5 (S/cm) to ≈10-2 (S/cm), with increasing pyrolysis temperature from 1000 to 1400 °C. Furthermore, the electrical conductivity of the SiOCN ceramic derived from N-C bond bearing precursor is three to five times higher than that of the sample derived from N-Si containing precursor at each pyrolysis temperature. The combined structural study by Raman spectroscopy and chemical analysis suggests that the increase of electrical conductivity with the pyrolysis temperature is due to the sp3-to-sp2 transition of the amorphous carbon phase. The higher conductivity of the amine-derived SiOCN is also discussed considering features like the volume % of the free-carbon phase and its possible N-doping. Fluorescence of the SiOCN samples treated at low temperatures, 400 and 600 °C, has been studied. The spectra show that the heated precursors fluoresce in the visible range with a dominant blue emission. Since the non-heated polymer precursors do not fluoresce, emitting centers must be formed during the polymer-to-ceramic transformation and associated with the structural changes. The origin of the luminescence could be originated from defects related to C, O and/or Si. Finally, we investigated the gas sensing behavior of the SiOCNs pyrolyzed at low and high temperatures. Regarding the electrical gas sensing of the SiOCN ceramics pyrolyzed at 1400 °C, the response to two target gases NO2 and H2 was tested by in situ DC conductance measurements at operating temperatures from 200 to 550 °C. The SiOCN ceramics are sensitive to NO2 at temperatures below 400 °C and to H2 at temperatures above 400 °C. In addition, the response observed for the studied SiOCN ceramics is higher than that reported in the previous studies for SiOC ceramic aerogels. With regard to the optical gas sensing of the SiOCNs obtained from the heat treatment of the polymer precursors at 400 and 600 °C, fluorescence spectra in the presence of organic vapors such as acetone and hexane were recorded. The results show that these tested vapors quench the fluorescence of the studied SiOCN. In conclusion, the SiOCN ceramics can be promising materials for the gas sensing application." @default.
- W333847420 created "2016-06-24" @default.
- W333847420 creator A5050878543 @default.
- W333847420 date "2015-04-16" @default.
- W333847420 modified "2023-09-24" @default.
- W333847420 title "Synthesis and Characterization of Multifunctional Polymer-Derived SiOCN" @default.
- W333847420 cites W142304997 @default.
- W333847420 cites W143426376 @default.
- W333847420 cites W1498970371 @default.
- W333847420 cites W1508015035 @default.
- W333847420 cites W15668222 @default.
- W333847420 cites W1584365695 @default.
- W333847420 cites W1646785497 @default.
- W333847420 cites W1847852556 @default.
- W333847420 cites W1965649382 @default.
- W333847420 cites W1966960868 @default.
- W333847420 cites W1967486143 @default.
- W333847420 cites W1968736282 @default.
- W333847420 cites W1968837950 @default.
- W333847420 cites W1969667948 @default.
- W333847420 cites W1970747467 @default.
- W333847420 cites W1972265838 @default.
- W333847420 cites W1973528308 @default.
- W333847420 cites W1977294658 @default.
- W333847420 cites W1978385544 @default.
- W333847420 cites W1979112224 @default.
- W333847420 cites W1982072818 @default.
- W333847420 cites W1983835849 @default.
- W333847420 cites W1984099391 @default.
- W333847420 cites W1985021358 @default.
- W333847420 cites W1985483136 @default.
- W333847420 cites W1986169753 @default.
- W333847420 cites W1988919656 @default.
- W333847420 cites W1990028068 @default.
- W333847420 cites W1991777389 @default.
- W333847420 cites W1993065824 @default.
- W333847420 cites W1993244445 @default.
- W333847420 cites W1994779514 @default.
- W333847420 cites W1994820025 @default.
- W333847420 cites W1999329786 @default.
- W333847420 cites W2002366259 @default.
- W333847420 cites W2005851497 @default.
- W333847420 cites W2008365892 @default.
- W333847420 cites W2011280659 @default.
- W333847420 cites W2013243015 @default.
- W333847420 cites W2013330851 @default.
- W333847420 cites W2016379499 @default.
- W333847420 cites W2017272049 @default.
- W333847420 cites W2022880493 @default.
- W333847420 cites W2024519113 @default.
- W333847420 cites W2029850902 @default.
- W333847420 cites W2030325548 @default.
- W333847420 cites W2030745358 @default.
- W333847420 cites W2035776948 @default.
- W333847420 cites W2038885948 @default.
- W333847420 cites W2041732417 @default.
- W333847420 cites W2042367586 @default.
- W333847420 cites W2045899405 @default.
- W333847420 cites W2046072685 @default.
- W333847420 cites W2046619568 @default.
- W333847420 cites W2050967523 @default.
- W333847420 cites W2054655763 @default.
- W333847420 cites W2055629108 @default.
- W333847420 cites W2059584357 @default.
- W333847420 cites W2063121638 @default.
- W333847420 cites W2065906124 @default.
- W333847420 cites W2066146888 @default.
- W333847420 cites W2066931959 @default.
- W333847420 cites W2069424591 @default.
- W333847420 cites W2070340842 @default.
- W333847420 cites W2071257625 @default.
- W333847420 cites W2072467524 @default.
- W333847420 cites W2074709295 @default.
- W333847420 cites W2078936620 @default.
- W333847420 cites W2081857143 @default.
- W333847420 cites W2082778589 @default.
- W333847420 cites W2084259509 @default.
- W333847420 cites W2084811969 @default.
- W333847420 cites W2087189988 @default.
- W333847420 cites W2087398162 @default.
- W333847420 cites W2088760019 @default.
- W333847420 cites W2089619996 @default.
- W333847420 cites W2100368246 @default.
- W333847420 cites W2101138488 @default.
- W333847420 cites W2101314826 @default.
- W333847420 cites W2108705976 @default.
- W333847420 cites W2109774183 @default.
- W333847420 cites W2111675757 @default.
- W333847420 cites W2116661563 @default.
- W333847420 cites W2118054485 @default.
- W333847420 cites W2120285188 @default.
- W333847420 cites W2133548889 @default.
- W333847420 cites W2135355861 @default.
- W333847420 cites W2135839795 @default.
- W333847420 cites W2136578251 @default.
- W333847420 cites W2149862979 @default.
- W333847420 cites W2155314010 @default.
- W333847420 cites W2160344538 @default.
- W333847420 cites W2169032536 @default.
- W333847420 cites W2235679284 @default.