Glass is an amorphous solid with a random structure (microscopically, glass is also a liquid), and its atoms do not have a long-range order in space like crystals, but have short-range order similar to liquid. The glass maintains a specific shape like a solid, unlike gravity, which flows with gravity. Glass has four basic properties: (1) Isotropic: The atomic arrangement of glass is irregular, and its atoms have statistical uniformity in space. In an ideal state, the physical and chemical properties (such as refractive index, hardness, modulus of elasticity, coefficient of thermal expansion, thermal conductivity, electrical conductivity, etc.) of the homogeneous glass are the same in all directions. (2) No fixed melting point: The conversion of solid from glass to liquid is carried out in a certain temperature range (ie, softening temperature range). Unlike crystalline materials, there is no fixed melting point. The softening temperature range is Tg~T1, Tg is the transition temperature, T1 is the liquidus temperature, and the corresponding viscosity is 10 dPa·s and 10 dPa·s, respectively. (3) Metastability: The glassy substance is generally obtained by rapid cooling of the melt. When the transition from the molten state to the glass state, the viscosity increases sharply during the cooling process, and the particles do not have a regular arrangement to form crystals, which are not released. The latent heat of crystallization, therefore, the glassy substance contains a higher internal energy than the crystalline material, and its energy is between the molten state and the crystalline state, and is metastable. From a mechanical point of view, glass is an unstable high-energy state, such as the tendency of low-energy state transformation, that is, the tendency of crystallization, so glass is a metastable solid material. (4) Graduality and reversibility: The process of the glassy substance from the molten state to the solid state is gradual, and the changes in physical and chemical properties are also continuous and gradual. This is markedly different from the crystallization process of the melt, and a new phase is inevitable in the crystallization process, and many properties are mutated near the crystallization temperature point. The glassy substance is completed from a molten state to a solid state in a wide temperature range. As the temperature gradually decreases, the viscosity of the glass melt gradually increases, and finally a solid glass is formed, but no new phase is formed in the process. On the contrary, the process of heating the glass into a melt is also gradual. Ningbo Kyson Cool Electronic Technology Co., Ltd. , https://www.kysoncool.com