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Polyborosilazane synthesized from trichlorosilane (SiHCl 3 ), boron trichloride (BCl 3 ) and methylamine (MeNH 2 ) is highly sensitive to moisture for hydrolysis of -NHMe unites and is easy to cross-link for dehydrogenation of Si-H, N-H, which affected the industrial scale production of SiBNC ceramic fibers. In this paper,a new nitrogen source(n-propylamine, C 3 H 7 NH 2 ) was used instead of MeNH 2 to synthesis polyborosilazane precursor. The influences of nitrogen sources on the structures and properties of SiBNC ceramic fiber precursors were investigated. As compared to SiHCl 3 /BCl 3 /CH 3 NH 2 system, polyborosilazane precursor synthesized from the SiHCl 3 /BCl 3 /C 3 H 7 NH 2 system exhibited lower crosslink density, lower sensitivity to moisture and good melt spinnability, and the obtained ceramic fibers showed higher tensile strength (1.03 GPa, an increase of about 37.3%). This synthesis route (SiHCl 3 /BCl 3 /C 3 H 7 NH 2 ) may serve as a suitable synthetic route for a large-scale production of SiBNC ceramic fibers. [ABSTRACT FROM AUTHOR]

A novel processable and high yield polyborosilazane (PBSZ) precursor for SiBNC ceramic fibers was synthesized via boron trichloride (BCl 3 ), co-polymerization of trichlorosilane (SiHCl 3 ) and methylamine (MeNH 2 ), followed by trans-amination with NH 3 . The synthesized PBSZ precursor was characterized and the results showed that the polymeric precursor exhibited good melt–processability and green fibers with a diameter of 45 µm could be easily obtained by melt spinning. The green fibers were subsequently pyrolyzed at 1200 °C in nitrogen atmospheres to provide SiBNC ceramic fibers with a cylindrical hollow structure, ca.32 µm in diameter and 720 MPa in tensile strength. The green fibers had an approximately ceramic yield of 78% at 900 °C. [ABSTRACT FROM AUTHOR]

In this paper, polyborosilazane precursor was synthesied from HMDZ, HSiCl 3 , BCl 3 and CH 3 NH 2 using a multistep method. By controlling the storage conditions, parts of the polyborosilazane fibers were hydrolyzed. FT-IR, NMR, XRD, TEM and monofilament tensile strength test were employed to study the effects of hydrolysis of precursor on the structures and properties of polymer-derived SiBN ceramic fibers. FT-IR and NMR results indicate that Si-N group in PBSZ reacts with H 2 O to form Si-O-Si group. After pyrolysis reaction at 1400℃, Si-O-Si group will finally transformed into highly ordered cristobalite and β-quartz, resulting in formation of the wrinkled surface of the obtained SiBN ceramic fiber. The strip-like defects on fiber surface, according to monofilament tensile strength test, had a significant effect on mechanical property of the obtained SiBN ceramic fiber and caused no increase in fiber tensile strength of hydrolytic polyborosilazane fiber before and after pyrolytic process. [ABSTRACT FROM AUTHOR]