Polymer derived nitride matrix composites reinforced by 2·5-dimensional silica fibre

Abstract

Polyborosilazane, a low viscosity preceramic polymer with good infiltration efficiency and high char yield, was used to prepare amorphous composites with polymer derived nitride matrix reinforced by 2?5-dimentional silica fibre, and the mechanical properties and microstructures were investigated. The composites without fibre coating showed typical brittle fracture behaviour with a smooth fracture surface and a longitude flexural strength of just 46?3 MPa whereas the composites with fibre coating exhibited non-brittle fracture behaviour with distinct fibre pull-out on the fracture surface and a high longitude flexural strength of 129?5 MPa. It was the controlled fibre/matrix interface by precoating treatment that contributed to the high mechanical property of the composites.

High-temperature properties and associated structure evolution of continuous SiNO fiber-reinforced BN composites for wave transparency

“…Wave-transparent materials for use in radomes must be of low dielectric constant and loss tangent to minimize wave energy reflection and absorption. Generally, for frequencies ranging from 0.3 to 30 GHz, suitable wave-transparent materials should have a dielectric constant of 1-4 and a loss tangent of 10 À1 -10 À3 [26]. A dielectric constant and loss tangent that remain stable at the service temperature are also critical because optimization of the radome wall thickness is based on the values of these parameters at room temperature, and a significant variation at a high service temperature will decrease the wave transparency.…”

Synthesis and processing of silicon nitride and related materials using preceramic polymer and non-oxide sol-gel approaches

“…14) [174]. A polyborosilazane polymer produced from perhydropolysilazane and borazine was found to effectively wet silica fibres to produce ceramic composites [175] and these composites were found to have good ablation resistance and to be microwave transparent, suggesting radar window applications for vehicles re-entering the atmosphere from space [176]. Porous structures can be produced by infiltration of liquid polymers around templates, e.g.…”

A novel quartz fibre reinforced dense polyimide matrix composite: effect of preform stitching

“…The mechanical properties of polyimides can be significantly enhanced by reinforcing them with high-strength fibres, like glass fibre [5-7], basalt fibre [8], carbon fibre [9], etc., as such, the polyimide matrix composites can show high flexural strength (≈150 MPa) and can be served at 177°C for long-term service [10]. Among the well-developed reinforcing fibres, the quartz fibre (QF) is specialised by its low permittivity (≈3.78) and low electric loss (≈0.0002), which is advantageous for microwave transparency [11]. The QF reinforced polyimide matrix (quartz/PI) composites are thus promising candidates as high temperature radome or antenna window materials.…”