Develop lighter and tougher natural cellulose blocks
The development of new lightweight, high-strength materials with comprehensive performance that surpasses traditional structural materials such as engineering plastics, ceramics and metal materials has important strategic significance for aerospace and other related fields.
Recently, the team of academician Yu Shuhong of the University of Science and Technology of China has developed a new method of manufacturing nano-cellulose biomimetic structural materials, and successfully developed a class of natural nano-cellulose high-performance biomimetic structural materials. The material has excellent comprehensive performance, the density is only one-sixth of steel, and the specific strength and specific toughness are more than traditional alloy materials, ceramics and engineering plastics. This new type of biomass biomimetic structural material is expected to replace existing projects Plastics have broad application prospects in the fields of aviation, aerospace, military, national defense, and people's livelihood.
In Yu Shuhong's team laboratory, we saw the basic material for making this new material: a white jelly-like semi-solidified body. "It is mainly made of natural cellulose, not to mention its plain appearance, but it can be derived from a series of dense and breathable material products. For example, it can be used to make the filter layer of medical masks, which is expected to be used to replace the scarce meltblown cloth. ; Can manufacture lightweight, durable, beautiful, and fireproof furniture; Can be made into aircraft parts, environmentally friendly coatings, packaging bags, etc. "Yu Shuhong introduced. Because a large amount of available cellulose exists in the biomass of shrubs and straws in nature, the cost of raw materials is lower, and even waste can be turned into treasure.
"The reason why it is a bionic material is because it is inspired by nature." Yu Shuhong said that the material's light weight and high toughness mainly come from the design of the micron layer structure and nano three-dimensional network structure of the material. The high crystallinity inside the cellulose nanofiber can Provides extremely high strength. The fibers are combined through a large number of reversible interaction networks such as hydrogen bonds. Under the action of external forces, this high-density reversible interaction network can quickly dissociate and reconstruct, absorb a lot of energy, and make the material have High strength and high toughness are achieved at the same time, which overcomes the problem that traditional structural materials are difficult to have both high strength and high toughness. It is foreseeable that it will have broad application prospects in the fields of lightweight anti-impact protection and cushioning materials, space materials, precision instrument structural parts and other fields.
Projecting natural revelation in the laboratory
Over the years, many of Shu Shuhong's inspirations in scientific research have come from nature.
"Based on the inspiration of nature, since I returned to China in 2002, I have been engaged in research work in the field of biomimetic materials. From the biomimetic synthesis of inorganic nanomaterials in the early years, to the biomimetic preparation and application of macroscale nanocomposite materials in recent years, A more systematic exploration and research. "Yu Shuhong said. At present, he led the research team to make a series of progress in biomimetic materials, including the development of a series of inorganic nanomaterials biomimetic synthesis, self-assembly technology and simulated biomineralization methods, and based on these technical methods successfully biomimetic synthesis of a variety of magical macro Lightweight, high-strength new materials. For example, synthetic mother-of-pearl that is highly similar to natural mother-of-pearl, a new type of lightweight, thermal insulation, thermal insulation carbon material inspired by the hollow structure of polar bear hair, bionic polymer wood for fire prevention, thermal insulation, corrosion resistance, etc.
"Mother of pearl is the inner material in the shell and has a similar composition and structure to pearls, usually containing more than 95% calcium carbonate. But this calcium carbonate is not a powder in the traditional sense, it forms a special structure "Yu Shuhong said. The shell is a very good layered structure, just like the common brick wall and ladder classrooms on the macro level, which are built up layer by layer. This type of brick wall structure is very good in strength and toughness. With reference to the wall-building strategy of mollusks synthesizing natural mother-of-pearl, the team of Yu Shuhong proposed a new "assembly and mineralization" method, which mimics the formation process and chemical composition of the natural shell nacre from the source, and was successfully mineralized for the first time in the world Synthetic artificial mother-of-pearl. The chemical composition and structure of this kind of mother-of-pearl material are similar to those of natural mother-of-pearl, with similar mechanical properties, lower density, and superior fracture resistance.
Multi-field cooperation makes "1 + 1> 2"
It is worth noting that large-scale macro preparation and small-scale laboratory preparation are completely different physical and chemical processes. Therefore, how to ensure the consistency and stability of the composition and morphology of macro-prepared nanomaterials also involves a large number of basic scientific issues, which requires researchers to have an in-depth and detailed understanding of the conditions, mechanisms and processes of nanomaterial synthesis .
Recently, Yu Shuhong led the research team to realize the macro preparation of cellulose nanofibers. Compared with the traditional preparation method with high cost, complicated process and time consuming more than 3 days, the method they developed can achieve cellulose nanofibers within half an hour. Rapid macro preparation of fibers, and has better morphology and performance.
There must be corresponding scientific principles behind the magic materials. Obtaining inspiration from the macro, to the micro experiment, and finally returning to the macro application has always been the work of Yu Shuhong's team. Yu Shuhong said that in terms of specific materials, there is no best in the field of materials, only better, so with the advancement and improvement of technology and people ’s living standards, we will continue to develop better and more practical excellent materials, such as calcium carbonate It was used to make cement as early as 200 years ago. Nowadays, calcium carbonate can not only make cement, but also prepare other new composite new materials, and it has already played an important role in the fields of aviation, aerospace, military, national defense, and people's livelihood. "
At present, China is being "stuck neck" abroad in many high-tech fields. In fact, a very important aspect is that the key material is "stuck neck". "We must closely aim at the original innovation from 0 to 1, set a higher goal for ourselves, solve more the material" neck "problem, and make more contributions to national development." Yu Shuhong said. In recent years, he and his team have made it a scientific research goal to realize the serialization of bionic materials and improve the performance of traditional materials.