Direct Growth of Transparent Boron Nitride Neutron Shielding Layer for Space Window

Area of Science:

• Materials Science
• Nuclear Engineering
• Space Technology

Background:

• Cubic boron nitride (c-BN) and hexagonal boron nitride (h-BN) possess transparency and high ¹⁰B density, crucial for neutron shielding.
• Previous research has not explored the potential of c-BN and h-BN for space neutron shielding applications.
• Fabrication of transparent c-BN films is challenging, and controlled growth of thick, uniform h-BN films is limited.

Purpose of the Study:

• To explore the potential of boron nitride materials for space neutron shielding.
• To develop a novel space window design integrating neutron, bulletproof, and gamma-ray shielding layers.
• To achieve transparent and stable growth of thick hexagonal boron nitride (h-BN) films with controlled properties.

Main Methods:

• Development of a space window design incorporating an h-BN-based neutron shielding layer with advanced ceramic bulletproof and gamma-ray shielding layers.
• Incorporation of Carbon (C) and Oxygen (O) into h-BN to create sp²-sp³ hybridized BN (HBN), reducing refractive index mismatch with SiO₂ substrates.
• Chemical vapor deposition growth of HBN films up to 79.2 µm thickness with precise control and high uniformity.

Main Results:

• Achieved 90.9% transmission at 550 nm for an 11.9 µm thick HBN film.
• Enabled stable, transparent growth of HBN up to 79.2 µm with minimized thermal expansion mismatch.
• Optically optimized HBN (B_0.39N_0.39C_0.06O_0.16) demonstrated compensated boron density through enriched c-BN formation (63.4%), resulting in a density of 3.01 g cm^-3.
• HBN achieved equivalent neutron shielding efficiency to h-BN at 3% reduced thickness.

Conclusions:

• The developed HBN material and space window design show significant promise for effective space neutron shielding.
• The integration of HBN offers a stable, transparent, and efficient solution for protecting spacecraft and astronauts from neutron radiation.
• This research opens new avenues for utilizing advanced boron nitride materials in demanding space environments.