| Date | 12th, Jul 2022 |
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Rice University scientists who “flash” materials to synthesize substances like graphene have turned their attention to boron nitride, highly valued for its thermal and chemical stability.
Particles of mechanically sheared flash boron nitride, as seen through a scanning electron microscope. The arrow shows the direction of shear force applied to the material. The flash Joule heating process developed at Rice creates turbostratic materials with weak interactions between layers, making them easier to separate. Image credit: Tour Group
Microscope images showed the flakes are turbostratic — that is, misaligned like badly stacked plates — with weakened interactions between them. That makes the flakes easy to separate.
They’re also easily soluble, which led to the anticorrosion experiments. The lab mixed flash boron nitride with polyvinyl alcohol (PVA), painted the compound on copper film and exposed the surface to electrochemical oxidation in a bath of sulfuric acid.
The flashed compound proved more than 92% better at protecting the copper than PVA alone or a similar compound with commercial hexagonal boron nitride. Microscopic images showed the compound created “tortuous diffusion pathways for corrosive electrolytes,” to reach the copper, and also prevented metal ions from migrating.
Chen said the conductivity of the precursor can be adjusted not only by adding carbon but also with iron or tungsten.
He said the lab sees potential for flashing additional materials. “Precursors that have been used in other methods, such as hydrothermal and chemical vapor deposition, can be tried in our flash method to see if we can prepare more products with metastable features,” Chen said. “We’ve demonstrated flashing metastable phase metal carbides and transition metal dichalcogenides, and this part is worth more research.”
Source: Rice University
