Biomorphous porous oxide ceramics, A review

Abstract

Porous ceramics are a class of materials which have found a large number of applications in various industrial fields. Thanks to their interesting physico-chemical properties, these compounds have been exploited both in environmental and energy areas, demonstrating optimal performances. The development of innovative and affordable manufacturing pathways to produce highly porous ceramics is therefore always required. In recent years, researchers’ attention has been focused on the conversion of lignocellulosic biomass into porous carbide or oxide ceramics, also named biomorphous ceramics. The peculiar internal structure of lignocellulosic materials could indeed represent the perfect template for the formation of promising hierarchically porous ceramics, with unique characteristics that could not be obtained throughout other synthetic methods. Moreover, these lignocellulosic materials such as wood, fibers, pollen grains and leaves can be easily collected, and have a low market cost or are waste materials and byproducts, making the entire process more eco-friendly and less expensive. An interesting example of a wood biomass template that combines peculiar internal microstructure with economic and environmental sustainability is cork. The microstructure of the cork wood is composed of numerous hexagonal honeycomb cells which make it an optimal thermal, acoustic and vibrational insulator. Furthermore, cork is periodically harvested from the tree without harming the plant, making cork oak one of the best examples of a working tree being used for carbon storage. Nowadays, literature is mainly focused on the production of biomorphous carbide ceramics, while less attention has been paid to the formation of biomorphous oxide ceramics, with no review totally dedicated to their description. In this thesis, the state of the art of the hierarchically porous oxide ceramics derived from lignocellulosic materials as starting templates will be discussed. The thesis is intended to provide a comprehensive picture of the accessible production procedures, together with a presentation of the best performing practical applications of the various oxide ceramics. In addition, new possible investigation areas will be considered, so as to open up new interesting routes to explore.