Scientists transform balsa into ‘wood carbon sponge’
A new ‘wood carbon sponge’ that can endure extreme conditions could be used in products including strain sensors found in wearable health-monitoring electronics, water-purification devices and energy storage and conversion technologies.
Soft, sturdy and versatile, balsa wood has long been the material of choice for the production of all manner of wooden structures.
Now, scientists in the United States and China have enhanced the possibilities of balsa even further by using a unique combination of chemical and physical treatments to transform it into a ‘wood carbon sponge’ that can endure extreme conditions.
Dr Liangbing Hu, Nano-Engineer and Materials Scientist at the University of Maryland and Senior Co-Author of the study, said the results reveal the naturally rigid and incompressible balsa can now be carbonised without becoming too fragile to withstand repeated mechanical compression. It is also fatigue resistant and maintains electrical response sensitivity surpassing that of most other compressible materials containing carbon.
"Since this wood carbon sponge is fabricated completely from natural wood with a simple and cost-effective method, the source material is exceptionally renewable and sustainable, as opposed to popular options like carbon nanotubes or graphene," Dr Hu said.
The scientists achieved this new bendable yet resilient balsa by treating the wood with common chemicals to destroy the rigid hemicellulose and lignin fibres which maintain the cell-wall structure. They then heated the wood to 1,000 degrees Celsius, transforming the organic material into carbon.
The process resulted in the collapse of the rectangular pockets typically found in the microstructure of balsa, replacing them with wavy, interlocking carbon sheets, which Dr Hu described as resembling “a cross between a coiled spring and a honeycomb”.
Traditionally, carbonised wood has been produced using only the heating step, impacting on its strength to such an extent that it is relatively easy to destroy. To the surprise of the researchers, however, balsa wood carbonised using this new method withstood up to 10,000 substantial compressions before showing signs of deformation.
Source: Science Daily
Image credit: University of Maryland