1. IntroductionSonochemistry is the

1. Introduction

Sonochemistry is the research area in which mole- cules undergo a chemical reaction due to the application of powerful ultrasound radiation (20 kHz–10 MHz) [7]. The physical phenomenon responsible for the sono- chemical process is acoustic cavitation. Let us first ad- dress the question of how 20 kHz radiation can rupture chemical bonds (the question is also related to 1 MHz radiation), and try to explain the role of a few para- meters in determining the yield of a sonochemical reaction, and then describe the unique products obtained when ultrasound radiation is used in materials science.
A number of theories have been developed in order to explain how 20 kHz sonic radiation can break chemical bonds. They all agree that the main event in sono- chemistry is the creation, growth, and collapse of a bubble that is formed in the liquid. The stage leading to the growth of the bubble occurs through the diffusion of solute vapor into the volume of the bubble. The last stage is the collapse of the bubble, which occurs when the bubble size reaches its maximum value.
From here we will adopt the hot spot mechanism, one of the theories that explains why, upon the collapse of a bubble, chemical bonds are broken. This theory claims that very high temperatures (5000–25,000 K) [7] are obtained upon the collapse of the bubble. Since this collapse occurs in less than a nanosecond [8,9], very high cooling rates, in excess of 1011 K/s, are also obtained. This high cooling rate hinders the organization and crystallization of the products. For this reason, in all cases dealing with volatile precursors where gas phase reactions are predominant, amorphous nanoparticles are obtained. While the explanation for the creation of amorphous products is well understood, the reason for the nanostructured products is not clear. One explana- tion is that the fast kinetics does not permit the growth of the nuclei, and in each collapsing bubble a few nucleation centers are formed whose growth is limited by the short collapse. If, on the other hand, the pre- cursor is a non-volatile compound, the reaction occurs in a 200 nm ring surrounding the collapsing bubble [10]. In this case, the sonochemical reaction occurs in the li- quid phase. The products are sometimes nanoamor- phous particles, and in other cases, nanocrystalline. This depends on the temperature in the ring region where the reaction takes place. The temperature in this ring is lower than inside the collapsing bubble, but higher than the temperature of the bulk. Suslick has estimated the temperature in the ring region as 1900 C [10]. In short, in almost all the sonochemical reactions leading to inorganic products, nanomaterials were obtained. They varied in size, shape, structure, and in their solid phase (amorphous or crystalline), but they were always of nanometer size.

Hasil (Bahasa Indonesia) 1:

1. PendahuluanSonochemistry adalah daerah penelitian di mana mol-cules mengalami reaksi kimia karena penerapan kuat USG radiasi (20 kHz-10 MHz) [7]. Fenomena fisik yang bertanggung jawab untuk proses sono-kimia adalah kavitasi akustik. Mari kita posisi iklan gaun-pertanyaan tentang bagaimana 20 kHz radiasi dapat pecah ikatan kimia (pertanyaan juga berhubungan dengan radiasi 1 MHz), dan mencoba untuk menjelaskan peran dari beberapa ayat-meter dalam menentukan hasil reaksi sonochemical, dan kemudian menjelaskan produk unik diperoleh ketika USG radiasi digunakan dalam ilmu material.Beberapa teori telah dikembangkan untuk menjelaskan bagaimana 20 kHz sonik radiasi dapat mematahkan ikatan kimia. Mereka semua setuju bahwa acara utama di sono-kimia penciptaan, pertumbuhan, dan runtuhnya gelembung yang dibentuk dalam cairan. Tahap menuju pertumbuhan gelembung terjadi melalui diffusion uap terlarut ke dalam volume yang gelembung. Tahap akhir yaitu runtuhnya gelembung, yang terjadi ketika gelembung ukuran mencapai nilai maksimum.From here we will adopt the hot spot mechanism, one of the theories that explains why, upon the collapse of a bubble, chemical bonds are broken. This theory claims that very high temperatures (5000–25,000 K) [7] are obtained upon the collapse of the bubble. Since this collapse occurs in less than a nanosecond [8,9], very high cooling rates, in excess of 1011 K/s, are also obtained. This high cooling rate hinders the organization and crystallization of the products. For this reason, in all cases dealing with volatile precursors where gas phase reactions are predominant, amorphous nanoparticles are obtained. While the explanation for the creation of amorphous products is well understood, the reason for the nanostructured products is not clear. One explana- tion is that the fast kinetics does not permit the growth of the nuclei, and in each collapsing bubble a few nucleation centers are formed whose growth is limited by the short collapse. If, on the other hand, the pre- cursor is a non-volatile compound, the reaction occurs in a 200 nm ring surrounding the collapsing bubble [10]. In this case, the sonochemical reaction occurs in the li- quid phase. The products are sometimes nanoamor- phous particles, and in other cases, nanocrystalline. This depends on the temperature in the ring region where the reaction takes place. The temperature in this ring is lower than inside the collapsing bubble, but higher than the temperature of the bulk. Suslick has estimated the temperature in the ring region as 1900 C [10]. In short, in almost all the sonochemical reactions leading to inorganic products, nanomaterials were obtained. They varied in size, shape, structure, and in their solid phase (amorphous or crystalline), but they were always of nanometer size.