Biomass based aerogels reinforced with carbon nanostructures as a nanocomposite material for construction

Abstract

The construction sector contributes significantly to environmental pollution, with increasing environmental concerns associated with sustainability and waste disposal challenges, materials derived from renewable resources such as nanocellulose and biomass are receiving more attention. Nanocellulose, the most renewable and biodegradable polymer, has been extracted from various plant resources through mechanical and chemical means and has been used as reinforcement for composites. Aerogels are lightweight and highly porous materials which can withstand thousands of times their own weight and have very low thermal conductivity, both properties could be of interest to construction materials. This thesis considers recent advances in cellulose nanoparticles and composites and proposes new approaches for their application in construction materials, with reduced ecological impact. A key consideration in determining the materials used for this work was their availability and renewable origin, paper waste was used as raw material for the extraction of cellulose nanocrystals (CNCs) by acid hydrolysis. In particular, office printing paper CNCs showed crystallinity index values as high as 62.81%), making it a suitable eco-friendly candidate. Fruit pulp, due to its inherent porous structure when freeze-dried, was selected as the matrix for the preparation of aerogels. Iron is a common catalyst for the growth of carbon nanostructures, and preliminary experiments showed that treatment of biomass from commercial freeze-dried raspberry and blackberry fruits, with iron salts, produced a carbon aerogel, with iron particles. The proposed process for obtaining the initial aerogels from fruit pulp and CNCs, is freeze-drying, the resulting aerogel being the basis for a carbon-carbon composite by pyrolysis, followed by growth of carbon nanostructures by Chemical Vapor Deposition (CVD). Iron nanoparticles would be the basis for subsequent growth of carbon nanostructures by Chemical Vapor Deposition (CVD). The carbon-carbon composites resulting from the proposed approach are expected to exhibit unique hierarchical meso-macroporous structures from the natural structures of the fruit, with improved mechanical properties by the addition of CNCs, and from carbon nanotubes or other nanostructures growing over the fruit pulp based carbon aerogel. The resulting materials are expected to exhibit excellent mechanical and thermal properties. The contribution of this dissertation is to further study aerogels, proposing an alternate material for their composition that is more eco-friendly and can be an alternative for waste recycling. The intent is to use this sustainable material to acquire new characteristics and properties, besides those known for aerogels, by using nanomaterials that make them more mechanically stable. Main emphasis is placed in the construction sector, for more beneficial and efficient materials, compared to concrete and steel; however it can also be used in other applications such as supercapacitors, filtration systems and catalysts, among others.