Novel Materials for Radiation Shielding
Researchers have developed ultrathin, stretchable, and 3D-printable composites utilizing single-walled carbon nanotubes (SWCNTs) and boron nitride nanotubes (BNNTs). These materials are designed to provide shielding for electronics against both electromagnetic interference (EMI) and high-energy neutron radiation.
The Need for Advanced Shielding
Electronic systems in environments such as space, nuclear facilities, medical radiation settings, and defense applications are susceptible to disruption or damage from EMI and neutron radiation. Traditional shielding methods, like metals and concrete, are often too heavy or rigid for modern lightweight and flexible electronics. This study aimed to create a solution that addresses these limitations.
Dual-Function Nanotube Architecture
The new material system integrates two types of nanotubes, each serving a distinct function:
- SWCNTs: These are electrically conductive and effective in attenuating electromagnetic waves.
- BNNTs: These contain boron atoms with a high neutron absorption cross-section, making them suitable for neutron shielding.
Previous research typically examined these materials separately; this study combined them into a single multifunctional system.
"The new material system integrates two types of nanotubes, each serving a distinct function, combining what was previously examined separately into a single multifunctional system."
From Suspension to 3D Print
The material creation process involved several key steps:
- SWCNTs and BNNTs were dispersed in a solution using surfactants to ensure stable suspensions and uniform mixing.
- Free-standing hybrid films, typically 10 to 20 micrometers thick, were produced through vacuum filtration. Microscopy revealed a coaxial architecture, with SWCNT bundles wrapped around BNNT cores.
- To create printable composites, the nanotube network was incorporated into a polydimethylsiloxane (PDMS) elastomer matrix.
- The resulting ink was processed via direct ink writing, an extrusion-based 3D-printing method, enabling the fabrication of complex geometries. Rheological testing confirmed the ink's suitability for printing.
Impressive Performance Across Metrics
Hybrid Nanotube Films
The hybrid nanotube films formed a dense, interconnected network that supported charge transport and electromagnetic shielding. In the X-band frequency range, the films achieved EMI shielding effectiveness exceeding 50 dB at micrometer thicknesses. This shielding was predominantly absorption-dominated, with energy dissipation occurring primarily through ohmic losses in SWCNT pathways.
For neutron shielding, a composite with an SWCNT:BNNT ratio of 2:8 demonstrated a neutron attenuation coefficient of approximately 1.27 mm⁻¹, resulting in about 72% attenuation at a 1 mm thickness. This performance was largely attributed to the boron atoms within the BNNT structure.
Printable Composites
When embedded in PDMS, the material became stretchable, exhibiting fracture strains above 125%, while retaining shielding capabilities. EMI shielding effectiveness reached up to about 23 dB at sub-millimeter thicknesses, remaining stable through repeated deformation. Thermal stability was observed across a wide range, from approximately -196 °C to 250 °C.
Geometric Advantages
Direct ink writing allowed for the creation of geometrically tunable designs, such as honeycomb lattices. These architectures were observed to enhance electromagnetic attenuation by promoting multiple internal reflections, suggesting that shielding performance can be adjusted through geometry in addition to material chemistry.
Future of Protective Electronics
These findings outline a strategy for developing multifunctional shielding solutions for harsh environments. The approach combines low weight, mechanical durability, thermal resilience, and dual shielding capabilities within a single platform.
"This approach combines low weight, mechanical durability, thermal resilience, and dual shielding capabilities within a single platform, indicating potential utility for future electronic systems requiring robust protection in demanding operational conditions."