| Summary: | 博士 === 國立臺北科技大學 === 電機工程系 === 106 === This study used Polyvinyl alcohol (PVA) as an additive medium in the process of preparing colloidal silver(CS) by a micro-electrical discharge machine(Micro-EDM), to discuss the effect of PVA on Ag ions(Ag+)/Ag nanoparticles (Ag0)concentration electrical conductivity and absorption peak, arcing rate, peak value, and field emission scanning electron microscope(FE-SEM). The electrical conductivity meter and UV-Visible spectrometer (UV-Vis) were employe in the experiment to test the correlations among electrical conductivity, absorption spectrum, and concentration in the colloid silver solutions at different concentrations. The equations and data of electrical conductivity, concentration, and ultraviolet (UV) absorbance were then utilize to detect high and low concentrations of Ag+. Finally, the PVA was take as an additive to discuss its effect on colloid silver concentration, arcing rate, peak value, FE-SEM, and suspension mechanism.
The CS for this experiment is prepared by using Micro-EDM of real-time monitoring, whereby the silver metal is dissolved in deionized water (DW) by the energy of arc discharge through the Submerged Arc Discharge Method (SADM) so as to prepare the metal colloid with Nano-and Sub-micron particles. The preparation process is free of any chemical agent and the process is fast and simple. The important process parameters of Micro-EDM include discharge voltage, current, and pulse discharge on-off duration, and the sample concentration can be controlle under appropriate conditions. The nano-characteristics are validate by UV-Vis, Laser light scatterometer and FE-SEM.
According to the fitting equation in the experimental results, the UV-Vis is for the measurement when the concentration is low, and the conductivity meter is for the measurement when the concentration is high. The activity of Ag+ concentration increases under different dilution conditions and increases contrarily with the dilution rate. The absorbance of Ag+ and Ag0 rises with time, and the activity is 1~2 times greater after the Ag+ is diluted. Therefore, silver ion and the silver nanoparticles accompany each other.
The concentration of Ag0/Ag+ solution increases with the increasing addition of the PVA, i.e., the concentration of Ag0/Ag+ solution is approximately proportional to the addition of PVA. Addition of PVA also enables to increase the successful rate of CS and Ag+ electrode arcing. Meanwhile, the peak response of the absorbance of UV is thus higher and displacement phenomena also occurre due to the rising of suspensibility as well as the ability to absorb UV being promoted. Inspection via SEM, it is found that smaller Ag+ particles and more amount of Ag+ particles will be obtained with the addition of PVA. Moreover, since the PVA with the properties of covering, dispersion and stability, the addition of PVA makes the particles distribution in CS more uniform.
|
|---|
