According to the traditional theory, the concept of the mesophase can be explained as: the general material exhibits optical anisotropy if it exists in a crystalline state, and exhibits optical isotropy when it exists in a liquid state. However, there is a class of substances that can assume an optically anisotropic turbid fluid state in the intermediate stage from crystal to liquid process (or reverse process), which is both liquid form and crystal optical anisotropy. Crystallography It is called liquid crystal, and it is called mesophase in the phase theory [1]. Mesophase pitch (liquid crystal phase pitch) is a mixture of a variety of flat disk fused aromatic hydrocarbons having a relative molecular mass of 370 to 2000. It is generally believed that in 1961 Tayler discovered optically anisotropic mesophase globules when studying coal coking in Australia. In 1965, he and Brooks [2] studied the microstructure and formation mechanism of mesophase spheres and explained for the first time the conversion of isotropic pitch to anisotropic asphalt. This has opened a new chapter in the research of liquid phase carbonization and the development of the carbon industry, and also laid the foundation for the preparation of high performance new carbon materials. In the course of 50 years of development, mesophase pitch as a typical carbonaceous mesophase raw material is recognized for its wide range of sources, excellent performance, low price, high carbon yield and high processability. It is an excellent precursor for advanced functional carbon materials, such as needle coke, mesophase pitch-based carbon fiber, mesophase pitch-based foamed carbon, mesophase pitch-based electrode material, mesophase pitch-based carbon/carbon composite. These functional materials will play a huge role in the defense industry, aerospace, cutting-edge technology, and daily life. China's research in this field started late, but Tianjin University, Dalian University of Technology, Beijing University of Chemical Technology and the Shanxi Coal Research Institute of the Chinese Academy of Sciences have done a lot of work and made gratifying progress. (Citation: "Chemical Progress")
The following is a high-resolution picture of the asphalt mesophase taken by a well-known research institution in China using the German Leica DM4P intelligent polarizing microscope:
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