Amorphous materials

Amorphous materials are also called amorphous or glassy materials. This is a large class of rigid solids with high hardness and high viscosity coefficient comparable to crystalline materials (usually 10 poise, that is, 10 Pa·s or more, It is 10 times the viscosity coefficient of a typical fluid).

Amorphous materials are also called amorphous or glassy materials. This is a large class of rigid solids with high hardness and high viscosity coefficient comparable to crystalline materials (usually 10 poise, that is, 10 Pa·s or more, It is 10 times the viscosity coefficient of a typical fluid). However, the spatial arrangement of its constituent atoms and molecules does not show periodic and translational symmetry, and the long-range order of the crystalline state is destroyed; it is only due to the interaction between the atoms that it is in a small area of a few atoms (or molecules) in diameter. There are short programs in the domain. Since there is no effective experimental method to accurately determine the atomic structure of amorphous materials, the above definitions are relatively speaking.

Amorphous materials have three basic characteristics.

① There are only short programs in the cell, but no long programs; the wave vector k is no longer a good quantum number describing the state of motion (see the energy band of a solid).

② Its electron diffraction, neutron diffraction and X-ray diffraction patterns are composed of wide halos and dispersed rings; with an electron microscope, no contrast between grain boundaries, crystal defects, etc. can be seen.

③ The amorphous solid of any system is metastable compared with its corresponding crystalline material. When the temperature is continuously increased, a significant structural change occurs in a very narrow temperature range, from an amorphous state to a crystalline state. This crystallization process mainly depends on the atomic diffusion coefficient, interface energy and melting entropy of the material ( See structural relaxation)