Thermoformable Boron Nitride Based All‐Ceramics

Abstract

Thermoforming processing, traditionally reserved for thermoplastic polymers and sheet metals, is extended here to boron‐based all‐ceramics. Specifically, sintered boron nitride composite sheets manufactured via a combined vibration and tape‐casting photopolymerization process exhibit a highly oriented microstructure that allows these preform sheets to flow as viscous Bingham pseudoplastics during compression molding. These sintered all‐ceramic preforms are thermoformed into thin, complex parts with features down to 200 µm. Further, a new workflow is leveraged to generate bespoke all‐ceramic heat spreaders that can be press‐fit onto printed circuit boards and outperform metal heat sinks as a low‐profile thermal management solution. This work offers a route for other all‐ceramics that may be thermoformed through first fabricating pre‐forms with highly‐ordered anisotropic microstructures.

YAG:Ce PiGF@Alumina‐Substrate in a Reflection Mode for High‐Brightness Laser‐Driven Projection Display

“…[47][48][49] However, the reported BN-added PiGFs still required the supporting substrate such as alumina or sapphire plate. We believe that cosintering YAG:Ce phosphors with h-BN slurry to produce novel YAG:Ce composite film using h-BN as thermoformable all-ceramic matrix [50] is an effective and feasible route to avoid the usage of alumina substrate. The related investigation has been carried out in our lab.…”