Incorporating boron carbide into fused silica imparts multiple mechanisms to facilitate vat photopolymerization

Abstract

Rapid manufacturing of complex-shaped ceramic components has long been a pressing issue in the aerospace industry. Recent progress in this direction takes advantage of additive manufacturing, by employing vat photopolymerization (VPP) followed by sintering. Here we demonstrate a new recipe/protocol that enables the VPP route to deliver silica products of high relative density as well as high strength. This is achieved by incorporating 2.5 wt% of boron carbide (B4C) into the fused silica slurry, which offers beneficial effects in multiple fronts. During the VPP process, the added black B4C, together with the refractive index difference between the two components in the mixture, effectively increased the light absorbance. Upon sintering, the boron oxide produced by the oxidation of B4C played the role of a sintering aid. The boron oxide also helped to suppress the crystallization of the amorphous silica and therefore the formation of cracks. As a result, the overall quality (forming precision, density, strength and dielectric constant) of the product surpasses by far those prepared previously via VPP-sintering. In particular, the flexural strength reached 60.7 MPa, a factor of 2.5 better than the previously reported highest value. Extending the success above further, we have manufactured a complex-structured silica radome, as a demonstration of the high-quality products achievable for practical applications.