Design of Polymeric Si−B−C−N Ceramic Precursors for Application in Fiber-Reinforced Composite Materials

Abstract

The synthesis, detailed spectroscopic characterization, polymer-to-ceramic conversion, and high-temperature behavior of a new class of polymeric precursors for Si-B-C-N composites are discussed. The title compoundsCH 2 -CH 2 ; 5a: R 1 , R 2 ) H; 5b: R 1 ) H, R 2 ) CH 3 ; 5c: R 1 , R 2 ) CH 3 ) were designed especially for the preparation of ceramic films and fiber-reinforced ceramic composite matrixes. They are obtained in quantitative yields by the reaction of oligovinylsilazane [(H 2 CdCH)SiH-NH] n (4) with tris(hydridosilylethyl)boranes of general type B(C 2 H 4 SiHR 1 R 2 ) 3 (C 2 H 4 ) CHCH 3 , CH 2 CH 2 ; 3a: R 1 , R 2 ) H; 3b: R 1 ) H, R 2 ) CH 3 ; 3c: R 1 , R 2 ) CH 3 ) in a thermally induced hydrosilylation reaction without catalyst and/or solvent and without the formation of byproducts. Ceramic yields are 83% for 5a, 82% for 5b, and 63% for 5c as shown by thermogravimetric analysis (TGA). High-temperature TGA of the as-obtained amorphous ceramic materials, carried out in an argon atmosphere, reveals a thermal stability toward degradation of the 5b-derived material 6b up to 2000 °C. In contrast, the 6a material, which was obtained from 5a, decomposes around 1850 °C. The least stable is the 6c ceramic, which decomposes at 1450 °C. The microstructure development of 6a-6c was investigated in the temperature range of 1400-2000 °C by X-ray diffraction (XRD), indicating that preferentially crystalline R-silicon carbide is formed at 1700 °C for 6a, 1500 °C for 6b, and 1600 °C for 6c. In addition, there are less intensive reflections observed in the XRD patterns of 6a, caused by the formation of β-silicon nitride.

Pyrolytic conversion of an AlSiNC precursor prepared via hydrosilylation between [Me(H)SiNH]4 and [HAlN(allyl)]m[HAlN(ethyl)]n

“…• C. 44 ) As shown in the 1 H NMR spectra of ISP and AE-alane, the integral ratio of the CH 2 = CH -signal to the CH 3 -CH 2 -signal decreases from 1 : 9 in AE-alane to 0.7 : 9 in ISP. This result indicates that the relative amounts of the allyl groups in ISP are slightly lower than those in AE-alane, and it consequently suggests that hydrosilylation occurs partially.…”

Progress of a novel non-oxide Si-B-C-N ceramic and its matrix composites

“…When the amorphous ceramic is used at high temperatures for a long duration, it may crystallize, decompose or lose weight, and macro deformation may occur to the ceramic components. The thermogravimetric curve of the polymer-derived amorphous Si-B-C-N ceramic in the helium atmosphere (a) [15], and the XRD patterns of the Si-B-C-N ceramics annealed at different temperatures for 3 h in the nitrogen atmosphere (•, α-SiC; ♦, β-Si 3 N 4 ) (b) [8]. The phase composition of the as-annealed nano Si-B-C-N ceramic may be varied, if raw materials or polymer synthetic process changes.…”

“…Additionally, the film also 1 cm Fig. 26 Carbon fiber fabrics before (left) and after resin-transfer-molding and thermolysis (right) (a) [8], and the cross section morphology of the Si-B-C-N coating prepared by spinning and pyrolyzing technology on the surface of SiO 2 -Si (b) [74].…”

“…When pyrolyzing is finished, the remaining substance is an inorganic ceramic, mainly consisting of Si, B, C and N. The as-pyrolyzed ceramic generally has an amorphous structure [6], a high structural stability [7,8], a large viscosity and a nice oxidation resistance [9,10]. When the amorphous ceramic is annealed at 1800 ℃-2000 ℃ in an inert atmosphere for several hours, its structure will change into a thermodynamically stable one [8,11]. That is, the amorphous ceramic will crystallize into a nano composite ceramic, with a phase composition of B-N-C, SiC and/or Si 3 N 4 .…”

Silicon-Based Polymer-Derived Ceramics: Synthesis Properties and Applications-A Review

“…Many examples of polysilazanes and polycarbosilazanes synthesized by means of dehydrocoupling reaction of hydrosilanes have been reported in recent years, 58,164,165 showing the importance of hydrosilanes as suitable starting materials in these processes. Polyborosilylcarbodiimides are another important class of precursors for SiBCN ceramics.…”