Periodic Reporting for period 2 - DESCALE (De-railing scaling: From fundamentals of crystallization fouling on nano-materials to rational design of scale-phobic surfaces)
Reporting period: 2021-08-01 to 2023-01-31
Crystallization fouling, a process where limescale forms on surfaces, is pervasive in nature and technology, negatively impacting the energy conversion and water treatment industries. Despite significant work, rationally designed materials that are intrinsically resistant to crystallization fouling without the use of active methods like antiscalant additives (which can persist long after their disposal and the toxicological impact of which in effluent is questioned) remain elusive. This is because antiscalant surfaces are constructed today without sufficient reliance on an intricate but necessary science-base, of how interweaved interfacial thermofluidics, nucleation thermodynamics, and surface nanoengineering control the onset of nucleation and adhesion of frequently encountered scaling salts like calcium carbonate and calcium sulfate. Such scaling salts are common components of fouling deposits in industrial heat exchangers and membranes, which significantly inhibit heat transfer and flow performance. Therefore, guided by interfacial thermofluidic and thermodynamics theories, and employing advanced experimental methods in the areas of surface nanoengineering and diagnostics, this project will develop an integrated knowledge-base for how engineered surfaces can beneficially interact with interfacial transport phenomena in order to significantly advance antiscalant surfaces. We aim to pinpoint mechanisms for inhibiting scale nucleation and reducing adhesion in order to design and engineer antiscalant materials based on the collaborative action of their composition and topography. The effects of surface texture curvature, surface composition, and substrate compliance on scale nucleation and adhesion have intertwined and sometimes competing impacts, which we aim at elucidating to realize high performance scale-phobic surfaces. Connected to this are cutting edge materials fabrication techniques and considerations to the development of surfaces for future applications.
We recruited and trained the research team, including two doctoral students, acquired the necessary equipment, and developed our methodologies for investigation the fundamentals of crystallization fouling. Building on this, we were able to design and realize nanoengineered surfaces which are promising regarding crystallization inhibition. This is the basis of a peer-reviewed publication that we are writing and planning to submit in early 2022. We were also able to design, fabricate, and test promising low adhesion surfaces with inherent scale-phobicity properties. This is the basis of an additional peer-reviewed publication that we are writing and planning to submit in late 2021. Using a fouling experimental unit, which mimics a water-cooled heat exchanger, we have also identified promising nanotextured metallic surfaces for repelling the formation of calcium carbonate and calcium sulfate. Results from this investigation will be reported as a conference paper for the 10th Conference on Experimental Heat Transfer, Fluid Mechanics and Thermodynamics.
Guided by nucleation theory, we have identified specific surface nanotexture and composition, which acts to delay the onset of crystallization fouling of calcium carbonate. We expect to create a knowledge-base on the relationship between surface nanotexture and super-saturation and the onset of nucleation of both calcium carbonate and calcium sulfate as well as their polymorphs. We expect this to be the contributions of a doctoral student. Guided by interfacial transport theories, we have identified and fabricated compliant surfaces--which we have studied with the necessary microscale resolution--with low-adhesion to micro-foulants including scale.