Synthesis of CdO Ultradisperse Powders Using Atmospheric Pressure Glow Discharge in Contact With Solution and the Investigation of Intermediate Products

A new plasma-solution method of the CdO ultradisperse powders synthesis was described. The atmospheric pressure direct current discharge was excited in the ambient air by applying a high direct voltage to two pointed titanium electrodes placed above liquid anode and liquid cathode in the H-shaped cell. The discharge current was 40 mA and the total input power was about 40 W. The action of the DC glow discharge on the cadmium nitrate water solution in the absence of additional reagents and without electrodes-solution contact was shown to result in the production of the solids in the liquid phase. The kinetics of particles formation was studied using turbidimetry and nephelometry methods. Powders' chemical composition and morphology was obtained using X-ray diffraction spectroscopy (XRD), electron-dispersive X-ray spectroscopy (EDX), thermogravimetric analysis (TGA), differential-scanning calorimetry (DSC) and scanning electron microscopy (SEM). It was found that as-synthesized powders are not the pure cadmium hydroxide but the mixture of the cadmium nitrate, hydroxy nitrate and hydroxide. Some assumptions regarding the mechanisms and pathway of the chemical processes both under the plasma action on the solution and during the calcination of as-synthesized powders were discussed.