January 1, 2016.
Deposits from hard water can be problematic as they can form scaling on boilers and cooling towers. Scaling can reduce thermal efficiency. Coatings can be used to prevent mineral fouling by changing the surface energy. Some deposits have inverse solubility; such as calcium sulfate. This means that as temperature rises, they become less soluble and can crystallize out of solution. Calcium sulfate is often found in hard water. Crystalization tests were done to determine how coatings such as various POSS (Polyhedral oligomeric silsesquioxane) compounds acted as nucleating surfaces for calcium sulfate. POSS compounds were tested in particular because they have very low surface energy. This would theoretically make nucleation difficult. Solutions of calcium sulfate were placed in microwave vials with different nucleating surfaces. The vials were sealed and heated to 95˚C. After cooling, tests were done to determine the amount of calcium sulfate that had come out of solution.
California Polytechnic State University (Cal Poly SLO)
This project has been made possible with support from Chevron (www.chevron.com) and the California State University STEM Teacher Researcher Program.