When a solid is heated, atomic and molecular vibrations of various frequencies are excited in the solid, causing crystallization.Generally, when a solid is vibrated, the vibration amplitude increases at a specific frequency, and this frequency is determined by the shape and size of the solid.

　The research group found that the filling rate of atoms and molecules varies in the glass, which appears to be an irregular arrangement of atoms and molecules, and each region vibrates strongly at a specific frequency depending on the size of the sparse and dense regions. It was presumed that it was present, and it was thought that crystallization would be possible without heating if it was vibrated at that frequency.

　Colloidal glass is a collection of fine particles of about 1 micron (100 / 1 meter) in an aqueous solution that are randomly arranged.The feature is that it has the same random structure as glass, but all phenomena occur slowly.That is, in colloidal glass, since the frequency of fine particle vibration corresponding to atomic / molecular vibration is low, it is possible to verify amorphous crystallization using an existing device.This time, as a result of experiments while changing the frequency finely, we discovered rapid crystallization due to vibration around 70 Hz.This phenomenon cannot be explained by the crystallization theory proposed in the past, and elucidation of the mechanism is a topic for future research.

　This achievement shows the feasibility of a crystallization method using sound, and leads to the development of a new ultra-high-strength material production method that replaces heat treatment.In addition, selective crystallization by ultrasonic irradiation is also possible, and it is expected that a new substance (phononic crystal) composed of glass and crystals will be developed.

Paper information: [Scientific Reports] Accelerated crystallization of colloidal glass by mechanical oscillation