A Novel Gelcast SiO₂-Si₃N₄-BN Ceramic Composites for Radome Applications

Abstract

Fused silica (SiO₂) ceramics composites were widely used in missile applications (radomes). In the present work, the required properties (flexural strength without disturbing the dielectric properties) were attained through a novel gelcasting process by adding Silicon Nitride (Si₃N₄) and Boron Nitride (BN) to the fused silica. The experiments were conducted using Response Surface Methodology (RSM) and the process parameters of gelcasting process such as solid loading, monomer ratio, monomer content and additives (Si₃N₄& BN) were considered as input parameters and flexural strength, porosity and dielectric constant as response parameters. Single parameter and interaction parameter effect on responses were studied. The effectiveness of derived models was compared with Analysis of Variance (ANOVA). Statistical analysis proven that input parameters have critical effect on responses. The derived RSM mathematical models have a higher R² values (Flexural strength 98.93%, Porosity 94.89% and Dielectric constant 95.93%) which shows the critical relation between actual and predicted values. The optimal responses obtained were flexural strength 111.67 MPa, porosity 33.18% and dielectric constant 4.42 corresponding parameters process parameters solid loading 49.99%, additives Si₃N₄ 5 wt%, BN 15 wt%, monomer content 13.87 wt% and monomer ratio 4.56.