Introduction of KRI’s sol–gel technologies with reference to the shape classification of the materials

KRI has been successful in conducting many sol–gel related projects. In this article, we review KRI’s sol–gel projects that fall into the following four categories: zero dimensions (particle applications), one dimension (fiber applications), two dimensions (coating applications), and three dimensions (bulk applications). (1) Zero dimensions: at KRI, we have developed a new process to not only synthesize large-sized (over 10 µm) silica particles by using a microreactor device, but also synthesize core–shell particles that eliminate the photocatalytic effect of TiO₂. (2) One dimension: KRI has developed the electrospinning deposition method which is a process used to form nanofibers by discharging raw material liquid from a syringe under high voltage. We have successfully formed polysilsesquioxane (PSQ) nanofibers for application in Li batteries as separators, as well as metal oxide nanofibers such as TiO₂ and ZnO. (3) Two dimensions: KRI has developed organic–inorganic hybrid hard coatings. Recently, we have focused on PSQ materials for hydrophobic coatings and hydrophilic coatings. (4) Three dimensions: we have successfully developed large-sized silica glasses as well as organic–inorganic hybrids as transparent materials for bulk applications.