Low temperature self-densification of high strength bulk hexagonal boron nitride.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 30787275.
- Also identified by DOI 10.1038/s41467-019-08580-9 and PMC identifier 6382832.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Hexagonal boron nitride (hBN) ceramics are expected to have wide applications at high temperatures as both a structural and functional material. However, because of its flake structure and general inertness, it is currently impossible to sinter hBN powder to a dense bulk (with a relative density of above 96%) even at 2000 °C. Here, we report dense bulk hBN with 97.6% theoretical density achieved at a lower preparation temperature (1700 °C) via a self-densifying mechanism without sintering additives. During the sintering process, cubic boron nitride particles incorporated into the hBN flake powders transform into BN onions with a significant volume increase, thus filling in voids among the hBN flakes and highly densifying the hBN bulks. The resulting dense hBN ceramics possess 2-3 times the strength of traditional hBN ceramics. This phase-transition-induced volume expansion strategy could lead to dense sintered compacts with high performance in other ceramic systems.