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A brief Introduction of Ultrasonic on the Crystallization

Crystal is the material from a variety of substances directly into a crystal state of the process. It is a phase transition, accompanied by thermal effects. Therefore, some thermodynamic crystallization should take place under the conditions. Phase change of state from the perspective of crystallization can be divided into gas – solid crystal, liquid – solid crystal and solid – solid crystalline three categories. Including liquid – solid phase crystallization is crystallization from the crystal, which includes solution crystallization and melts crystallization. Solution crystallization process material from the liquid crystalline state into the process, go through three processes: the formation of supersaturated solutions, crystallization nucleation and crystal growth. Nucleation in supersaturated solution generates a certain number of nuclei; basis in the nuclei grow into crystals, crystal growth was.

In a variety of external conditions for the formation of nuclei and crystal growth, such as the addition of seed, application of physical field (ultrasound, electromagnetic fields, magnetic fields), etc., of various physical fields have an important effect on the crystal. This paper focuses on a variety of physical field of research in the solution crystallization conditions, promote the physical field enhancement of solution crystallization process, and promote the development of solution crystallization theory.

Ultrasonic propagation in liquid medium, as “vibration” and “cavitation” effect, would crystallization induction period and metastable zone into the impact of nuclear size. Christian used cooling crystallization method, under stirring and ultrasonic, were used to measure metronidazole crystal nucleation in the metastable zone and the induction period. Study found that ultrasonic cavitation bubble collapse generated trap a lot of energy when released, made available to the molecules together to become nuclear free energy required to promote metronidazole, the nucleation. Ultrasonic effectively change the crystal size of metronidazole and improve the crystallization yield.

Brandon and other studies of the ammonium molybdate solution under ultrasonic crystallization process, reveals the four ammonium ultrasonic crystal is studied. The results show that in the absence of ultrasound generated β-4 under the reaction of ammonium molybdate need 1 ~ 2 d, in just 10 minutes under ultrasound can be completed, and the crystal is changed to produce a powder-type four-molybdate.

Alejandro, such as microwave crystallization process under analysis, that the microwave on the crystallization of mainly the following three aspects: (1) microwave to speed up the reaction and to promote the deposition of crystalline precipitation; (2) Microwave hasrefinement, both the role of crystallization; (3) Microwave will not change the crystal morphology, crystal structure and crystal form. Microwave irradiations can Al/ PE/ Al interfacial layer affect the crystalline structure, with the microwave irradiation time, the crystal face size increases. Microwave irradiation ordered orthorhombic phase macromolecular chain regularity down, lattice defects increase, reducing the effective length slip chain. Polyethylene interface layer can be realized to some of the orthogonal crystal to change the six-party, large orthogonal crystal grain size and degree of disorder. With the interface layer increases, the microwave crystal structure of polyethylene decreased gradually.

Crystallization of a complex process, external field, the transfer process, nucleation, growth mechanism and kinetics of Jiu Gengjiafuza, we should strengthen the process of mechanism study with a view to modeling, Shebeikaifa Yijigongcheng based amplification provide Enhancement of Solution crystallization in recent decades developed a new chemical separation method. Ultrasonic field, the microwave field, electric field, magnetic field enhancement of solution crystallization process of nuclei formation and crystal growth mechanism of the impact of different mechanisms, in-depth study of the mechanism should be established based model. Meanwhile, the crystallization of different physical fields in the interaction in solution is also a hot research.

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