Abstract
Hydrothermal synthesis of particles is usually carried out at subcritical conditions in batch reactors. In supercritical region, reaction rate increases dramatically due to low dielectric constant (ɛ) of SCW. Therefore, fine particles (e.g., metal oxides) are rapidly synthesized (e.g., 0.4 s∼2 min) in a continuous SCW process. In the oxide synthesis, an ionic metal salt is first hydrolyzed to metal hydroxide, which is then dehydrated to form metal oxide crystals by precipitating from SCW solution. Here, three types of reactors (batch, flow and diamond anvil cell) are introduced in details for the study of SCW synthesis of particles. In general, batch reactors are used for long time process, and flow reactors for short time synthesis. Diamond anvil cell is used for in-situ visual and spectroscopic study of particle formation. Continuous flow reactors allow a better control of experimental conditions (e.g., temperature, pressure, time, concentration, pH and heating rate) that lead to formation of smaller particles with uniform size.
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Fang, Z. (2010). Supercritical Water Process. In: Rapid Production of Micro- and Nano-particles Using Supercritical Water. Engineering Materials. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-12987-2_2
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DOI: https://doi.org/10.1007/978-3-642-12987-2_2
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