Abstract
Composite ceramic fibers comprising about 80 wt% boron nitride (h-BN) and 20 wt% Si3N4 were fabricated through melt-spinning, electron-beam curing, and pyrolysis up to 1600 °C in atmospheres of NH3 and N2, using a mixture of poly[tri(methylamino)borazine] (PBN) and polysilazane (PSZ). By analyzing the microstructure and composition of the pyrolyzed ceramic fibers, we found the formation of binary phases including crystalline h-BN and amorphous Si3N4. Further investigations confirmed that this heterogeneous microstructure can only be formed when the introduced ratio of Si3N4 is below 30% in mass. The mean modulus and tensile strength of the fabricated composite fibers were about 90 GPa and 1040 MPa, twice the average of the pure h-BN fiber. The dielectric constant and dielectric loss tangent of the composite fibers is 3.06 and 2.94 × 10−3.
Highlights
With the development of the aerospace industry, there is an urgent demand for high-performance wave-transparent materials such as antenna windows or domes equipped on hypersonic flight vehicles.These materials should have high thermal stability, good dielectric behavior, and excellent mechanical properties to meet the requirement of extreme working conditions
Boron nitride (BN) ceramic fiber can be a good candidate for reinforcing fiber in wave-transparent applications due to its low density, high melting point, and low dielectric constant and loss tangent
BN/Si3 N4 composite fibers can be prepared by the blends of poly[tri(methylamino)borazine]
Summary
With the development of the aerospace industry, there is an urgent demand for high-performance wave-transparent materials such as antenna windows or domes equipped on hypersonic flight vehicles. These materials should have high thermal stability, good dielectric behavior, and excellent mechanical properties to meet the requirement of extreme working conditions. We have prepared BN fibers with excellent dielectric properties by using poly[tri(methylamino)borazine] as a preceramic polymer [10]. BN/Si3 N4 composite fibers can be prepared by the blends of poly[tri(methylamino)borazine]. 3 N4 composite fiber by using blends of poly[tri(methylamino) comprehensive performances with high mechanical properties good dielectric borazine] and polysilazane, with other techniques the same asand those of BN fiber. Material and Methods and properties of the obtained fiber were analyzed
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