AUTHOR=Chen Chao , Liu Yongsheng , Yue Wei , Ye Fang , Wang Jing , Zeng Qingfeng 

TITLE=The Influence of Si3N4w Volume Fraction on the Microstructure and Properties of Si3N4w/Si3N4 Composites via CVI Technique

JOURNAL=Frontiers in Materials

VOLUME=7

YEAR=2020

URL=https://www.frontiersin.org/journals/materials/articles/10.3389/fmats.2020.588716

DOI=10.3389/fmats.2020.588716

ISSN=2296-8016

ABSTRACT=<p>Wave-transparent ceramic composites with excellent comprehensive performances are of particular significance for the development of space vehicles. In this study, Si<sub>3</sub>N<sub>4w</sub> was prepared by the gel-casting process and then combined with chemical vapor infiltration (CVI)-obtained Si<sub>3</sub>N<sub>4</sub> to yield Si<sub>3</sub>N<sub>4w</sub>/Si<sub>3</sub>N<sub>4</sub> composites with five Si<sub>3</sub>N<sub>4w</sub> volume fractions. The influence of the Si<sub>3</sub>N<sub>4w</sub> volume fraction on the microstructures, mechanical properties, and dielectric characteristics of the Si<sub>3</sub>N<sub>4w</sub>/Si<sub>3</sub>N<sub>4</sub> composites were all studied. The results showed that Si<sub>3</sub>N<sub>4w</sub>/Si<sub>3</sub>N<sub>4</sub> composites possess A sandwich structures. Higher Si<sub>3</sub>N<sub>4w</sub> volume fractions led to less incorporated amounts of the Si<sub>3</sub>N<sub>4</sub> matrix at the same depth. The 25 vol% Si<sub>3</sub>N<sub>4w</sub>/Si<sub>3</sub>N<sub>4</sub> composites integrated relatively higher Si<sub>3</sub>N<sub>4w</sub> volume fraction and load transfer ability of the matrix, leading to better flexural strengths reaching up to 41.37 MPa. The dielectric constants of the five prepared Si<sub>3</sub>N<sub>4w</sub>/Si<sub>3</sub>N<sub>4</sub> composites ranged from 2.25 to 4.0. The dielectric losses were all lower than 0.005, demonstrating the good dielectric properties of the Si<sub>3</sub>N<sub>4w</sub>/Si<sub>3</sub>N<sub>4</sub> composites.</p>