N-doped polymer-derived Si(N)OC: The role of the N-containing precursor
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Nadhira Bensaada Laidani Fondazione Bruno Kessler, Centro Materiali e Microsistemi, Plasma, Advanced Materials and Surface Engineering (PAM-SE), Trento 38123, Italy
Gian Domenico Sorarù Department of Industrial Engineering, University of Trento, Trento 38123, Italy (Received 17 October 2014; accepted 30 January 2015)
Polymer precursors for Si(N)OC ceramics have been synthesized by hydrosilylation reaction of polyhydridomethylsiloxane (PHMS) with three different nitrogen containing compounds. The results obtained by combining characterization techniques such as FTIR, 13C- and 29Si-NMR confirm the occurrence of the cross-linking reaction between Si–H and vinyl groups. The structural characterization of the corresponding ceramic phase shows that the type of N-containing compounds strongly influences the pyrolytic transformation as well as the crystallization behavior of the final ceramics. Elemental analysis clearly indicates that N is present in the Si(N)OC matrix and the degree of N retention after pyrolysis is related to the type of N-containing starting compound. XPS data show that N–C bonds are present in the Si(N)OC ceramic samples even if only N–Si bonds are present in the starting N-containing precursors. However, if nitrogen atoms form bonds with sp2 carbon atoms in the preceramic polymer then a larger fraction of C–N bonds is retained in the final Si(N)OC ceramic.
Contributing Editor: Paolo Colombo a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2015.44
extensively characterized using different techniques1 and also modeled by ab initio molecular dynamic simulation.20 These materials can be doped with extra elements to further extend the range of interesting properties. In particular, B- and N-doping, resulting into Si(B)OC and Si(N)OC systems, have been reported in the literature.21,22 In the B-doped system, boron atoms are present either in the amorphous silicon oxycarbide network as BC3 yOy, 0 # y # 3, units or in the sp2 C layers of the free C phase as substitutional BC3 units.23,24 As a consequence, B addition has a strong impact on different properties of Si (B)OC such as the photoluminescence,25 the electrical conductivity26 and the high temperature stability.26,27 On the other side, few studies have focused on the synthesis and characterization of N-doped SiOC.10,22 The objective of this paper is to synthesize N-doped SiOC ceramics using different N-containing precursors and then to characterize their structure and high temperature behavior, in particular, the thermal stability and crystallization behavior. Accordingly, we report here for the first time how the molecular structure of the precursors influences both the nitrogen content and its chemical bonding nature in the final ceramics. In this work, three different preceramic polymer precursors for Si(N)OC ceramics are studied. The polymer precursors are synthesized via hydrosilylation reaction between a linear polysiloxane containing Si–CH3
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Ó Materials Research Society 2015
I. INTRODUCTION
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