Using Freeze-Casting Method to Create Lamellar Copper Structures – An Experimental Study of the Freezing Behavior of Cupric Oxide Colloidal Suspensions

Abstract

This study investigates the directional solidification behavior and the effects of initial freezing temperature on the formation of porous structure. The aqueous suspension with 10 vol.% cupric oxide (CuO) particles is prepared by mixing CuO particles, polyvinyl alcohol, and polyvinylpyrrolidone in deionized water. Additionally, potassium hydroxide is used to adjust the pH values between 8–10. Based on the measurement of the suspension viscosity, the optimal amount of the dispersant and the range of pH values that enable a well dispersed and stable suspension is identified. The freezing curves of the suspensions are measured to obtain the freezing point of the suspension as well as the effect of the potassium hydroxide on the freezing behavior. The suspensions then undergo directional freezing under various initial freezing temperatures. After sublimation under a near vacuum pressure, the green samples are infiltrated with epoxy to facilitate visualization and characterization of the pore morphology and orientation using an optical microscope. We believe that the obtained relationship between the freezing conditions, and the structural specifics of freeze-cast porous CuO lays the groundwork for freeze-cast porous copper with desirable pore morphology and structures for thermal management and energy storage applications.