Ceramic Fibers for Matrix Composites in High-Temperature Engine Applications

Abstract

High-temperature engine applications have been limited by the performance of metal alloys and carbide fiber composites at elevated temperatures. Random inorganic networks composed of silicon, boron, nitrogen, and carbon represent a novel class of ceramics with outstanding durability at elevated temperatures. SiBN(3)C was synthesized by pyrolysis of a preceramic N-methylpolyborosilazane made from the single-source precursor Cl(3)Si-NH-BCl(2). The polymer can be processed to a green fiber by melt-spinning, which then undergoes an intermediate curing step and successive pyrolysis. The ceramic fibers, which are presently produced on a semitechnical scale, combine several desired properties relevant for an application in fiber-reinforced ceramic composites: thermal stability, mechanical strength, high-temperature creep resistivity, low density, and stability against oxidation or molten silicon.

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

“…During the heating only a slight increase in weight of 0.49 % up to 1300 °C is observable. This effect is credited to the formation of a passivating surface double layer which protects the ceramic against further oxidation [6]. The in comparison to SiB 1.44 N 2.20 C 0.92 O 0.21 [36] improved oxidation stability, which showed a mass loss of 6.5 % at 700 °C while releasing carbon dioxide, is indicative for the absence of carbonaceous regions within the network.…”

“…As measured by the combination of properties relevant for an application as structural ceramics at high temperature, the Si/B/N/C ceramics show superior performance [6]. In particular its creep resistance and stability in oxygen (compared to the other non -oxide ceramics) is without precedent [6]. By applying various analytical probes, the basic structural features have been revealed.…”

“…Single source molecular precursors of the general type R 1 R 2 R 3 Si-X-BR 4 R 5 with X = NH [1, [8][9][10], N(CH 3 ) [11][12][13], CH 2 [14,15], C 2 H 4 [16] and R 1 -R 5 = CH 3 or Cl have proven to perform particularly well with respect to versatility and quality of the final ceramic. As measured by the combination of properties relevant for an application as structural ceramics at high temperature, the Si/B/N/C ceramics show superior performance [6]. In particular its creep resistance and stability in oxygen (compared to the other non -oxide ceramics) is without precedent [6].…”

“…Random networks consisting of Si, B, N, and C represent a new class of ceramics that are exclusively accessible along a molecular -polymer precursor route [1][2][3][4][5][6][7]. Single source molecular precursors of the general type R 1 R 2 R 3 Si-X-BR 4 R 5 with X = NH [1, [8][9][10], N(CH 3 ) [11][12][13], CH 2 [14,15], C 2 H 4 [16] and R 1 -R 5 = CH 3 or Cl have proven to perform particularly well with respect to versatility and quality of the final ceramic.…”

Interfaces fracas em compósitos de matriz cerâmica de alumina/alumina

“…As fibras conferem uma maior tolerância ao dano, tornando esses compósitos aptos a aplicações extremas em que sejam requisitadas altas temperaturas de operação, baixa densidade, resistência à corrosão e tolerância adequada ao dano [1][2][3][4][5][6][7][8][9][10].…”