In a serendipitous discovery, researchers at the University of British Columbia have created a new ultra-black material that absorbs almost all light, opening up potential applications in fine jewelry, solar cells and precision optical devices.
Professor Philip Evans and PhD student Kenny Cheng experimented with high-energy plasma to make wood more water-repellent. However, when they applied the technique to the cut ends of the wood cells, the surfaces became extremely black.
Measurements by Texas A&M University’s Department of Physics and Astronomy confirmed that the material reflected less than one percent of visible light, absorbing nearly all of the light that struck it.
Instead of dismissing this serendipitous discovery, the team decided to focus on designing ultra-black materials, bringing a new approach to the search for Earth’s darkest materials.
“Ultra-black or super-black materials can absorb more than 99 per cent of the light that hits them, much more than regular black paint, which absorbs about 97.5 per cent of light,” says Dr. Evans, a professor in the Faculty of Forestry and BC Leadership Chair in Advanced Forest Products Manufacturing Technology.
Ultra-black materials are increasingly sought after in astronomy, where ultra-black coatings on devices help reduce stray light and improve image clarity. Ultra-black coatings can improve the efficiency of solar cells. They are also used in the manufacture of art and luxury consumer items such as watches.
The researchers have developed prototypes of commercial products using their ultra-black wood, initially focusing on watches and jewelry, with plans to explore other commercial applications in the future.
Wonderful wood
The team named and trademarked their discovery Nxylon (niks-uh-lon), after Nyx, the Greek goddess of the night, and xylon, the Greek word for wood.
Most surprisingly, Nxylon remains black even when coated with an alloy, such as the gold coating applied to wood to make it electrically conductive enough to be observed and studied under an electron microscope. This is because Nxylon’s structure inherently prevents light from escaping rather than relying on black pigments.
The UBC team demonstrated that Nxylon can replace expensive and rare black woods like ebony and rosewood for watch dials, and it can be used in jewelry as a replacement for the black gemstone onyx.
“Nxylon’s composition combines the benefits of natural materials with unique structural characteristics, making it lightweight, stiff and easy to cut into complex shapes,” Dr Evans said.
Made from basswood, a tree widely found in North America and valued for hand carving, boxes, shutters and musical instruments, Nxylon can also use other types of wood such as European basswood.
Breathing new life into forestry
Dr. Evans and his colleagues plan to launch a start-up company, Nxylon Corporation of Canada, to develop Nxylon applications in collaboration with jewelers, artists and technology product designers. They also plan to develop a commercial-scale plasma reactor to produce larger super-black wood samples, suitable for non-reflective ceiling and wall tiles.
“Nxylon can be made from sustainable, renewable materials that are widely available in North America and Europe, opening the door to new applications for wood. The wood industry in British Columbia is often viewed as a declining, commodity-based industry. Our research demonstrates its great untapped potential,” said Dr. Evans.
Other researchers contributing to this work include Vickie Ma, Dengcheng Feng and Sara Xu (all UBC Faculty of Forestry); Luke Schmidt (Texas A&M); and Mick Turner (Australian National University).
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