Abstract

Titanium oxide particles were treated by water jet cavitation (WJC) generated and multifunction cavitation (MFC) using an ejector nozzle. Generation, growth, and collapse of cavitation are repeated with the particles of titanium oxide and platinum. Because the cavitation has an extremely high collapse pressure, the surface of the titanium oxide particles is processed by the microjets of cavitation in a reactor comprising the ejector nozzle. In the multifunction cavitation, ultrasonic irradiation of a waterjet during floating cavitation was used to generate microjets with hot spots. Hot working can be performed at the nanoscale on a material surface using this MFC process, resulting in morphological changes and variations in the surface electrochemical characteristics. The fundamental characteristics of multifunction cavitation were investigated theoretically and experimentally. Furthermore, the additional nozzle was put on the ejector nozzle in order to increase the temperature and pressure of bubble and the mechanism was clarified. The quantities of hydrogen and oxygen generated from titanium dioxide particles treated by multifunction cavitation in response to UV and visible light irradiation were remarkably increased compared to the amounts produced by particles treated by WJC processing. In this chapter, the methods and their results of processing particles by cavitation are introduced.

Highlights

  • In recent years, a variety of industrial applications have been identified for cavitation processing, including peening, surface and molecular structure modifications, fatigue strength improvement, and surface cleaning

  • The microjet hot spots were found to peel the ITO film from the glass to generate particles consisting of a combination of the ITO film and the soda-lime glass

  • It is considered that the titanium surface was processed by the micro-jet of cavitation, when the cavitation approaches to the surface of the titanium particles in the ejector reactor

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Summary

Introduction

A variety of industrial applications have been identified for cavitation processing, including peening, surface and molecular structure modifications, fatigue strength improvement, and surface cleaning. The authors have developed the multifunction cavitation, which is caused by ultrasonic irradiation of a waterjet during floating cavitation to generate microjets with hot spots. Hydrogen generation via the decomposition of water using a photocatalyst has been studied extensively, and photocatalytic hydrogen generation under UV irradiation has been developed, typically using titanium oxide as a substrate. This technology would exhibit high efficiency in the visible light portion of the electromagnetic spectrum. It was determined that multifunction cavitation is effective at improving the photocatalytic properties of TiO2 under visible light irradiation.

Multifunction cavitation mechanism
Blake threshold
Multifunction cavitation induced by low pressure liquid flow
Multifunction cavitation induced by liquid flow circulation
The Rayleigh-Plesset equation
Ultra-high temperature and pressure cavitation
Experimental
Results and discussion
Conclusions
Full Text
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