A blue-colored coating containing CoAl₂O₄ crystals was successfully prepared through the anodic oxidation of aluminum with pulsed wave under spark discharge in an electrolytic bath with 10 g/L Co(OH)₂. Cobalt aluminate, CoAl₂O₄, was formed by the chemical reaction of Al₂O₃ and Co(OH)₂ on the Al surface during the anodic oxidation process. The properties of the crystalline species, film thickness, surface roughness and color of the films can be controlled by regulating the spark discharge energy through the variation of the frequency of the applied current density with a square wave during the anodic oxidation under spark discharge.

Carbon dioxide (CO₂) gas was fixed in ultrafine bubble (UFB) water. Two methods were used to fix CO₂ gas in this research. One method involved blowing CO₂ gas into the UFB water. In this method, the CO₂ gas concentration was either 21 % or 100 %. This method was called the blowing method. The other method involved preparing the UFB water while contacting it with CO₂ gas. This method was called the contacting method. Calcium hydroxide was added to the UFB water to determine the amount of CO₂, and calcium carbonate was formed as a result. The volume of fixed CO₂ was calculated using thermogravimetric analysis of the samples. Both methods successfully fixed CO₂ in the UFB water. For 500 cm³ of the UFB water, the blowing method with 100 % CO₂ gas fixed up to 453 cm³ of CO₂. Additionally, the volume of CO₂ fixed by the contacting method was 192 cm³. The UFB water prepared by the contacting method retained CO₂ for a longer time compared to the blowing method.