Light ceramics Based on Boron Phosphide for Ballistic Applications – CAPBAB

The objective of this project is to develop ballistic protections that would be made of very low-density ceramics based on boron phosphides. The intrinsic performances (i.e. hardness, mechanical resistance) of these latter would be improved compared to metallic materials or structural ceramics. This objective requires the implementation of suitable ceramic processes integrating all the stages of the elaboration of these ceramics, from the synthesis of specific powders by original routes up to the rapid densification stage allowing the control of (micro- ), nano-structures of the sintered specimens. The promising intrinsic properties (low density, high hardness) of these new ceramics and their elaboration method which should lead to the production of fully densified and nano-structured ceramics, this project could be correlated to a drastic reduction in on-board masses for ballistic protection.
Furthermore, the compounds BP and B12P2 are the most stable “boron phosphide” phases in the B-P binary system. Currently, these phases are not commercially available in the form of powders or ceramics, so they remain laboratory "curiosities" and are still very little known. However, their physical properties remain exceptional: high thermal stability, high thermal conductivity and a high hardness value (> 30 GPa). Currently, the processes studied for the synthesis and shaping of BP and B12P2 powders require the combination of high temperatures and high pressures (a few GPa) and rely on chemical reactions that are often slow and sometimes even explosive.
In this project, we propose:
- to develop processes to synthetize fine and pure BP and B12P2 powders;
- to manufacture by SPS dense boron phosphide-based ceramics whose micro-, nano-structure would be homogeneous and well-controlled;
- to develop a complete ceramic process including synthesis and "flash" sintering steps of batches of boron phosphide powders allowing the manufacturing of large ceramic pieces;
- to evaluate and well understand the mechanical properties of these new ceramics under impact loading leading to an understanding of the relationship between performances and microstructural characteristics.
The originality of this project is mainly related to the elaboration of low density and very high hardness boron phosphide ceramics by implementing synthesis and sintering processes that are easy to implement, quick and economical. It is a technological breakthrough that can have far-reaching consequences, both civilian and military. The scientific and technological locks of this project mainly relate to the control both of the purity of boron phosphide powders during the SHS or mechanosynthesis stage and the chemical composition as well as the microstructural homogeneity of the large ceramic parts during sintering.
The consortium is composed of four academic laboratories, a transfer center, recognized in their fields of expertise with a history of fruitful collaborations. These collaborations notably led to the first full dense boron phosphide ceramics by using SPS method.