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1.
Inorg Chem ; 62(25): 10014-10020, 2023 Jun 26.
Artigo em Inglês | MEDLINE | ID: mdl-37307143

RESUMO

The high-temperature durability of SiBCN ceramics is significantly influenced by the boron concentration and synthesis methods. Although single-source synthetic routes allow one to obtain homogeneous ceramics at the atomic level, the content of the boron element therein is limited by borane (BH3). In this study, the synthesis of carborane-substituted polyborosilazanes was performed via a simple one-pot reaction of polysilazanes with alkyne bonds on the main chain and decaborododecahydrodiacetonitrile complexes with different molar ratios. This enabled one to vary the boron content from ∼0 to 40.00 wt %. The ceramic yields were in the range of 50.92-90.81 wt %. Independently of the borane concentration, SiBCN ceramics started to crystallize at 1200 °C, and B4C appeared as a new crystalline phase with increasing boron content. The introduction of boron inhibited the crystallization of Si3N4 and increased the crystallization temperature of SiC. The presence of the B4C phase improved both thermal stability and functional properties such as neutron-shielding characteristics of the ceramics. Therefore, this research opens up new prospects for the design of novel polyborosilanzes with great application potential.

2.
Materials (Basel) ; 16(3)2023 Jan 25.
Artigo em Inglês | MEDLINE | ID: mdl-36770061

RESUMO

Polyborosilazanes with controllable B/N ratio were synthesized using high-boron-content m-carborane, dichloromethylsilane, and hexamethydisilazane. After high-temperature pyrolysis, Si-B-C-N quaternary ceramics with SiC and B4C as the main phases were obtained. The B/N ratio in the precursors corresponded to the change in the feeding ratio of carborane and dichloromethylsilane. The effects of boron content and B/N ratio on the ceramic precursors and microphase structure in Si-B-C-N quaternary ceramics were explored in detail through a series of analytical characterization methods. A high boron content results in a significant increase in the ceramic yield (up to 71 wt%) of polyborosilazanes, and at the same time, the B/N molar ratio was regulated from 28.4:1 to 1.62:1. The appearance of the B4C structure in the Si-B-C-N quaternary ceramics through the regulation of the B/N ratio, has rarely been reported.

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