Abstract
This study developed a micro-electrical discharge machining (micro-EDM) system for producing TiO2 nanocolloids. When a proportional–integral–derivative controller designed using the Ziegler–Nichols method was adopted to control the interelectrode gap, TiO2 nanocolloids were obtained from spark discharges generated between two titanium wires immersed in deionized water. For a pulse on time–off time of 40–40 μs and a colloid production time of 100 min, TiO2 nanocolloids were produced that had an absorbance of 1.511 at a wavelength of 245 nm and a ζ potential of −47.2 mV. They had an average particle diameter of 137.2 nm, and 64.2% of particles were smaller than 91.28 nm. The minimum particles were spherical. The characteristics of colloids confirmed that the micro-EDM system can produce TiO2 nanocolloids with excellent suspension stability. The colloid production method proposed in this study has the advantages of low equipment cost and no dust diffusion in the process environment. These advantages can improve the competitiveness of the electric spark discharge method for high-quality TiO2 nanoparticle production. The colloids produced in this study did not contain elements other than titanium and oxygen, and they may prevent secondary environmental pollution.
Highlights
The range of applications of titanium dioxide (TiO2 ) nanoparticles (NPs) has recently been extended to personal protective products [1,2], biomedical materials [3], environmental pollution prevention [4,5,6], and anticancer care [7]
The electric spark discharge method (ESDM) for producing TiO2 nanocolloids can solve the aforementioned shortcomings of using chemical methods for producing TiO2 NPs
The principle of producing TiO2 NPs by using the ESDM is to use the high temperature generated by electric sparks to evaporate the surface of Ti metal wires immersed in deionized water (DW) [13]
Summary
The range of applications of titanium dioxide (TiO2 ) nanoparticles (NPs) has recently been extended to personal protective products [1,2], biomedical materials [3], environmental pollution prevention [4,5,6], and anticancer care [7]. Because TiO2 nanocolloids produced using chemical methods contain elements other than titanium and oxygen due to the suspending agent added during the process [8,9,10,11], these TiO2 nanocolloids can only be employed in certain fields. The electric spark discharge method (ESDM) for producing TiO2 nanocolloids can solve the aforementioned shortcomings of using chemical methods for producing TiO2 NPs. The principle of producing TiO2 NPs by using the ESDM is to use the high temperature generated by electric sparks to evaporate the surface of Ti metal wires immersed in deionized water (DW) [13]. The evaporated steam is rapidly cooled by DW and condensed into TiO2 NPs. The crystal structure of the sample prepares by ESDM was measured by XRD, which contained both titanium oxide and Ti simultaneously [14]
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