Innovative production processes of advanced ceramic materials for the energy sector

This Thesis investigates the production of novel lithium orthosilicate based materials to be used for two different applications in the energy sector as carbon dioxide (CO2) mitigation strategies. Lithium orthosilicate has recently gained increasing research interest since it could be used as solid sorbent for post-combustion CO2 capture at high temperature and as breeder blanket component in the future fusion reactors connected with the ITER (International Thermonuclear Experimental Reactor) project. The aim of this PhD activity is to provide different production processes to obtain suitable lithium orthosilicate items to be used in both these fields of the energy sector. In particular, in the first part of the Thesis, the research activity on solid sorbents for CO2 capture focuses on lithium orthosilicate synthesis, using different methods and precursors, and a doping method by addition of potassium carbonate is proposed, to promote the adsorption process by reducing diffusive phenomena. Macro-porous cylindrical pellets are produced, and the sorption performance at different temperatures and CO2 concentrations is evaluated by carrying out lab-scale CO2 adsorption tests in a thermogravimetric analyzer. This first part of the Thesis aims also to examine the sorption mechanism by kinetic and parametric modeling. A sorption kinetic model, based on the Shrinking Core Model (SCM), is developed for the doped-lithium orthosilicate sorbent even in pellet form. The second part of the Thesis deals with the research activity on lithium orthosilicate pebbles production as breeding material. A new low-temperature fabrication method based on the drip casting forming technique is presented and discussed, which overcome the manufacturing problems related to the typical high-temperature pebbles production processes. An experimental device has been designed and constructed for this purpose, and several experimental tests have been carried out to develop a suitable methodology for obtaining spherical and homogeneous lithium orthosilicate pebbles, with desired characteristics of high density and good mechanical resistance for the use in breeding blankets of future demonstrating fusion reactors