A new borazine-type single source precursor for Si/B/N/C ceramics

Abstract

The new borazine derivative [B{CH(CH 3 )(SiCl 3 )}NH] 3 (TSEB) was prepared by reacting Cl 3 Si-CH(CH 3 )-BCl 2 (TSDE) with hexamethyldisilazane (hmds) at ambient conditions. TSEB was characterized by infrared spectroscopy (IR), nuclear magnetic resonance (NMR), and by mass spectrometry (MS). The specially designed molecule serves as a single source precursor for the synthesis of a highly durable Si/B/N/C ceramic material via the well known 'polymer route'. Pursuing this philosophy, polymerization of TSEB with methylamine as the cross-linking reagent has lead to a highly homogeneous pre-ceramic polymer, which was further characterized by spectroscopic methods. Subsequent thermal degradation of the as-obtained polyborocarbosilazane was monitored by means of DTA/TG/MS up to 1400 uC. The resulting amorphous silicon boron carbonitride of the approximate elemental composition Si 3 B 3 N 5 C 4 exhibits an outstanding thermal durability at 2000 uC under inert conditions and is also stable in pure oxygen up to at least 1300 uC. The ceramic material still contains borazine rings from the TSEB precursor molecule embedded in the covalent Si/B/N/C network, acting as rigid structural units which reinforce the ceramic material on an atomic scale.

Borazine Based Molecular Single Source Precursors for Si/B/N/C Ceramics

“…In accordance to the pyrolysis of other polyborocarbosilazanes [8,20,21] the polymer degrades in three stages. Mainly the polycondensation is completed at 450 °C evolving methylamine (m/z = 31), however, also as a first product of fragmentation small amounts of HCN (m/z = 27) are cleaved.…”

“…In the borazine based precursors studied so far, boron and silicon are linked by carbon atoms or chains [19][20][21] linkage that is not constitutive of the first generation of Si/B/N/C ceramics. Thus, during the process of condensing a respective polymer by pyrolysis manifold rearrangements of B-C and Si-C bonds would be required, most probably resulting in a higher concentration of dangling bonds.…”

Physicochemical Characterization of Annealed PolySi/NIDOS/SiO2 Structures

“…The peak located around 1100 cm À1 corresponds with B-B bonds, [16] and moves toward the low wavelengths as the annealing duration increases, which indicated the transformation of B-B bonds into B-N bonds located at 1083 cm À1 . [17] Absorption intensities bonds that contain boron and nitrogen such as B-N (1400 and 626 cm À1 ) [17][18][19] and B-N-B (750 cm À1 ) [20] , decrease with the duration increasing. In the same way, the absorption intensity of the Si-N bond located at 1250 cm À1 [21] decreases with the annealing duration.…”

Synthesis, Characterization and Performance Study of Borosilazane as UV-Curable Borazine-Type Single Source Precursors for SiBNC Ceramic

“…目前针对陶瓷先驱体 UV 光固化的研究, Bowman 等 [5,6] 用乙烯基聚硅氮烷 (VL20)与巯基化合物组成共聚体系, 重点研究了巯基与 乙烯基配比、UV 辐照强度和引发剂浓度对巯基和乙烯 基官能团转化率、固化物尺寸收缩的影响. 李义和等 [7,8] [18,19] . 因此可以确定: …”