official account, WeChat uses WeChat scan code

to share with friends and friends circle

WeChat public address, Zhejiang University. In June 25th, the reunification is a well-known idiom story. It tells about the death of Chen in the Southern Dynasty, when Prince Xu Deyan broke a bronze mirror and held half of his wife as a token. Later, as expected, half of the mirror was used as a clue to reunite the couple < p > the ending of the story is perfect, but can the broken mirror really "reunite"? Maybe from the macro point of view, the two half mirrors are combined into one, but in fact, there are still many cracks and gaps in the interior, and the round mirror is easy to break again

source: WeChat official account "Zhejiang University", drawing: Gao Yuhua

, Zhejiang University chemistry department, Professor Tang Ruikang, and Liu Zhaoming researchers, the latest research found that by adjusting the internal structure of amorphous Calcium Carbonate Granules water content and external pressure to achieve the integration of amorphous Calcium Carbonate Granules. This strategy overcomes the shortcomings of traditional sintering and provides a new method for the preparation of inorganic bulk materials, especially an important preparation strategy. According to this method, the broken mirror can really be "reunited" as it appears < p > on June 25, Beijing time, this achievement was published by science, a top international journal. The first author of this paper is mu Zhaohe Kong kangren, a doctoral student in the Department of chemistry of Zhejiang University. The corresponding authors are Professor Tang Ruikang and researcher Liu Zhaoming in the Department of chemistry of Zhejiang University. The research work was supported by associate researcher Jiang Kai of East China Normal University, Dr. Dong Hongliang of Beijing high voltage Science Center and Professor Xu xurong of Qiushi Institute of higher research of Zhejiang University < p > "hard bone" inorganic matter how to change from powder to block < p > calcium carbonate is one of the common substances on the earth, which widely exists in aragonite, calcite, chalk, limestone, marble, travertine and other rocks. It is also the main component of animal skeleton or shell. At the same time, as an inorganic compound, it is also a common material in industry < p > if the existing artificial methods are used to produce calcium carbonate, only micron size white powder can be obtained. But in the actual production and life, what we need are generally "big" materials. How to turn powder materials into bulk materials is a key to improve the performance of inorganic materials < p > "organic materials with high elasticity and plasticity are relatively easy to deform, and inorganic compounds such as calcium carbonate are hard and brittle, so it is more difficult to make block materials." Tang Ruikang said that in many inorganic repair fields, such as cultural relics protection and tooth repair, organic repair materials are commonly used. However, as like as two peas, the organic material is similar to the original inorganic compound. However, due to poor internal compatibility, cracks and damage will occur. p> < p > how to achieve "similarity in form and spirit"? The fundamental way is to use inorganic materials to repair inorganic materials. A key problem to be solved here is the preparation of inorganic bulk materials < p > in the past, inorganic bulk materials were usually prepared by sintering inorganic particles. For example, ceramics were fired at a high temperature of about 1000 ℃. However, on the surface, it seems to be "hand in hand" bonded together, but in fact it is not completely fused. There are still gaps between the particles, and the internal structure is still "you are you, I am me", which ultimately affects the mechanical properties of the material. Moreover, many temperature sensitive biominerals and biomaterials can not be prepared by high temperature sintering Where is the breakthrough? Scientists try to find out from nature. Since more and more studies have found that organisms can produce continuous structure mineral skeleton through the fusion of amorphous precursor particles, can we bionically solve the problem of powder bulking in traditional methods and realize the preparation of inorganic bulk materials in mild environment < p > several stones merge into one stone < / P > < p > a previous achievement of Tang Ruikang's team - "inorganic ion polymerization" can realize the rapid preparation of centimeter sized calcium carbonate crystal materials in the laboratory, and the preparation process of these calcium carbonate has strong plasticity, which can grow into various shapes according to the mold shape like plastic, The study was published in the top international journal Nature in October 2019 < p > "this research in 2019 is to synthesize calcium carbonate crystal bulk materials from scratch. Our work is to study how to turn the existing calcium carbonate powder materials into bulk materials, such as fusing several stones into a big stone. It can be said that the two tasks come to the same end by different routes. " Tang Ruikang said < p > it is in the research process of the previous work that Mu Zhao found an interesting phenomenon that the boundary of amorphous calcium carbonate particles gradually disappeared during the pressing process, and finally completely fused into one < p > at that time, Mu Zhao did not understand the reasons behind the phenomenon, but Tang Ruikang encouraged Mu Zhao to continue to dig deeper and ask more why Water molecules play an important role in the crystallization of amorphous calcium carbonate particles. Although scientists have noticed this phenomenon before, there is still a lack of in-depth study on the relationship between the function, fluidity and structural stability of structural water Further research by Mu Zhaohe and Kong kangren found that if water molecules can be kept at a suitable amount, dynamic water channels can be formed in calcium carbonate, thus promoting the internal material transport process and eventually leading to the fusion of amorphous particles“ Too much water will form a new kind of water cluster, leading to the crystallization of amorphous calcium carbonate particles When one calcium carbonate molecule corresponds to 0.2-1.1 water molecule, and then 0.6-3.0 GPA pressure is applied, the fusion of amorphous calcium carbonate particles under pressure can be realized. The team has successfully constructed calcium carbonate bulk materials with continuous structure < p > in order to verify the results, the team labeled the gold nanoparticles on the surface of calcium carbonate particles and observed them by high-resolution transmission electron microscope after extrusion. It was found that there was no interface or gap between the calcium carbonate particles and they were completely fused“ Stone is rigid, water is flexible, when the stone contains a suitable amount of structural water, under pressure, this kind of stone is like plasticine, which melts when squeezed ?
2023-03-22 10:04:37