Enhancing mechanical properties of clay aerogel composites: An overview

While aerogel is a new classification of materials and considered most promising candidate for the advanced thermal insulation, clay aerogel shows significant potentials as it is natural, non-toxic, biodegradable and biocompatible material. To date most aerogels are produced through a supercritical drying process and most reviewed aerogels are silica based aerogels, nevertheless, more environmentally friendly aerogels have been attempted through the use of clays through an environmentally freeze-drying process. This paper presents a comprehensive overview of developing robust clay aerogels, including enhancing clay aerogel with various natural and synthetic polymers, and the reinforcement of clay-polymer aerogel with carbon nanotubes, natural fibres, glass fibre lamination and dip coatings. The results show that many factors could contribute to the classification of clay aerogels, including processing parameters and methodologies, raw materials as well as minor additives. One of the most significant setbacks regarding clay aerogels is their mechanical properties and in the past several years significant efforts have been spent on the improvement. The most successful method demonstrated so far was the incorporation of a water-soluble polymer and reinforcing aerogel composites with fibrous materials to achieve various levels of enhancements of clay-aerogels. This review shall provide a much useful concise database for the development, production and potential utilisation of clay aerogel for various industrial sectors.