Engineers at the University of Maryland have created a new class of thermal insulation material that has a performance of at least 10°C compared to foam or aerogel, is more than 30 times stronger than foam, and is more environmentally friendly. The staff called it Nanowood, which was cut from ordinary wood (in the early stages of the experiment, it was selected from the United States) and then removed all the lignin (the main cause of the brown/yellow wood and hardness of the wood). ).
The appearance of 'nano-wood' after isolation for one year (before) under normal environmental conditions
When the color of the wood is completely 'bleached' from white to white, it means that the lignin has been completely removed. In fact, this process is very similar to papermaking. After the wood is cut, it can pay attention to its texture.
Add sodium hydroxide and sodium sulfite to boil and then treat with hydrogen peroxide (hydrogen peroxide) to remove lignin and most of the hemicellulose. Freeze-dry to keep the structure of the wood, instead of holding it as you would expect. Go to papermaking.
Can be processed into 'volume', 'paper', 'block' and other forms
After the lignin has been extracted from the wood block, what remains is a very lightweight, white cellulose, that is, the original support structure of the wood. Compared to polyethylene, or silicon materials commonly used for domestic insulation, The thermal effect is several levels higher.
At the same time, its tubular shape also gives anisotropic properties. Heat can freely travel through the fiber strands, but in the other direction, it is not so easy.
Microstructure map - heat is easily evacuated through the tunnel tube, not through the past, producing a strong anisotropy.
Designers can use this feature to transfer heat to where they see fit, and stop it elsewhere - change the direction of nanofibers.
In addition, the natural cellulose fiber also has low strain. In the one-way collapse test, its strength is measured as more than 30 times that of the foaming material (polystyrene). In addition, since the entire body appears white, its effect of reflecting sunlight is also very high. Outstanding.
"Nano-wood" in the laboratory
Pictured above shows how ordinary wood becomes 'nano-wood'
The study was led by post-doctoral student Tian Li and assistant professor Liangbing Hu. They believe this is a very attractive material, but there are still many tasks to be completed before it goes into the tens of millions of households, such as fire prevention.
After all, due to the highly flammable nature of wood, to use in the construction industry, it must meet the fire protection requirements. However, on the other hand, nano-wood has biodegradable environmental characteristics, and is easily processed into paper, wood, or Curly and other forms.
'Nano-wood' production process
Finally, the key to blocking the large-scale commercialization of this technology is the cost of 'drying and bleaching' the wood. If the cost remains high, it cannot be put into practical use in a short time.
Details of this study have been published in the March 9 issue of the Science Advances journal.
