Benefitting from the combined properties of intrinsic ceramic materials and advanced porous configuration, lightweight porous ceramics with porosity ranging from 2.3 to 99% and pore size distribution within 3 nm - 3 mm exhibit low density, large specific surface area, high toughness, strong thermal shock resistance, good thermal insulation capability, excellent high temperature stability, and low dielectric constant, which are barely offered by metal, polymer or even their dense counterpart. This unique set of features endow porous ceramics an indispensable role in the future development of sustainable energy and environmental applications. To be successfully applied in these applications, precise selection of the type of ceramics and creation of their detailed structural features of the pores are the most important stages that require intensive investigations and comprehensive understanding. For a given ceramic, the synthesis process is critical for achieving the desired pore configuration and geometry which eventually determines the final properties of the products, including both the usual mechanical properties and other advanced functionalities. In this review, we will first focus on the fabrication processes that determine the pore structures and geometries. Four mainstream fabrication methods: partial sintering, replica template, sacrificial template, and direct foaming will be discussed, in addition to the additive manufacturing technique which has emerged as a promising process for the direct fabrication of porous ceramics components. Each approach demonstrates its unique suitability for a specific range of materials, porosity, pore size, pore connectivity, and pore distribution. The principles and challenges of each synthesis strategies will be summarised and discussed, the progress that can be made to meet the requirement of advanced applications has been clarified. We then focus on the properties derived from different pore features. The superior damage tolerance and thermal insulation capability of porous ceramics, as compared with their dense counterpart, are presented. Thirdly, the great potentials of these interesting porous ceramics for the energy- and environmental-based applications, including filters, catalyst support, energy storage and conversion components, energy harvesting devices, and insulators are highlighted, in association with the criteria and demands for manufacturing processes. It is envisaged that this review will provide a guidance in the manufacture of advanced porous ceramics with desired pore structures and properties tailored for specific applications. Finally, we will demonstrate how these porous ceramics could contribute to the development of current and future energy and environment technologies.

Porous ceramics: Light in weight but heavy in energy and environment technologies

Graphitized carbon materials from biomass resources were successfully synthesized with an iron catalyst, and their electrochemical performance as anode materials for lithium-ion batteries (LIBs) was investigated. Peak pyrolysis temperatures between 850 and 2000 °C were covered to study the effect of crystallinity and microstructural parameters on the anodic behavior, with a focus on the first-cycle Coulombic efficiency, reversible specific capacity, and rate performance. In terms of capacity, results at the highest temperatures are comparable to those of commercially used synthetic graphite derived from a petroleum coke precursor at higher temperatures, and up to twice as much as that of uncatalyzed biomass-derived carbons. The opportunity to graphitize low-cost biomass resources at moderate temperatures through this one-step environmentally friendly process, and the positive effects on the specific capacity, make it interesting to develop more sustainable graphite-based anodes for LIBs.

Iron-Catalyzed Graphitic Carbon Materials from Biomass Resources as Anodes for Lithium-Ion Batteries

The fabrication and mechanical properties of SiC/SiC composites prepared by SLS combined with PIP

Hierarchical porous ceramics with 3D reticular architecture and efficient flow-through filtration towards high-temperature particulate matter capture

Foam glasses have potential of using in several fields due to their high porosity. Usually, the foam glasses are prepared though chemical approach where the powdered glass is mixed with foaming agents at high temperatures. However, in such approach, the emission of gaseous pollutants (e.g. CO2) from the most used foaming agents can be harmful to the environment. Thus, understanding the mechanisms of foam formation is quite important to eliminate the drawbacks afore mentioned, as well as, give us more information on the processing steps. Herein, we propose a new chemical route to obtain foam glasses from soda-lime glass waste using sodium hydroxide and borax as foaming and flow agents, respectively. The reaction mechanism was investigated by thermogravimetric and differential thermal analysis, mass spectroscopy, mercury porosimetry, optical dilatometry, X-ray diffraction, and infrared spectroscopy. At the glass transition temperature (587o C), the crystallization of a new phase of hydrated sodium and calcium silicate (Na2CaSi2O6.2H2O) was observed. As demonstrated by mass spectrometry, when the mixture was heated to a temperature above the softening point, the foaming occurred only due to steam released from the hydrated sodium and calcium silicate. This foaming process provided a foam glass with 86% of porosity, low permeability and bulk density of 0.3 g/cm3. The results indicate the proposed approach is environmentally safe, besides being relatively cheap and easy to prepare.

Foam glass using sodium hydroxide as foaming agent: Study on the reaction mechanism in soda-lime glass matrix

https://digital.csic.es/bitstream/10261/149782/1/Permeability_Final.pdf

M.P. Orihuela

Papers

Permeability and mechanical integrity of porous biomorphic SiC ceramics for application as hot-gas filters

Thermal conductivity of porous biomorphic SiC derived from wood precursors

Flame confinement in biomass combustion systems for particles abatement