Development of magnetic and conductive cellulosic materials for absorption of electromagnetic waves

Cellulose is one of the most important representatives of biopolymers; it is available in large quantities, it has good mechanical properties, high hydrophillicity and is bio-degradable. But on the other hand, its use in technical field is inhibited by some disadvantageous properties. Combining cellulose fibres with nano particles presents an alternative to conventional finishing procedures of cellulosic materials and allows for the enhancement of existing and addition of new properties. Addition of nano particles influences or yields better mechanical properties, electrical conductivity, decreased flammability, enhanced chemical activity,…   Cellulose fibrous materials - regenerated cellulose fibres and pulp fibres - will be activated by swelling in alkali solutions and the expected enhancement of their uptake/absorption ability of precursor solutions will be characterised, since this improved property will enable higher loading of particles onto fibres’ surface and in fibres’ inner structure.   In order to obtain magnetic properties of cellulose fibres, soft magnetic particles (magnetite) and hard magnetic particles (cobalt ferrite), as well as composites of these two, will be used. As a consequence of their properties (low thermal stability, degradation in acidic media), cellulose fibres put forward certain limitations when synthesizing particles in their presence. This requires, that the second phase in the project will be a thorough study of the magnetic particles’ synthesis and also modification of the existing synthesis procedures form a point of view of subsequent application to fibres. Modified synthesis procedures will still have to ensure the required size, crystalline structure, surface morphology and colloidal properties of magnetic particles, i.e. properties, which enable their optimal functionality.   Coating of activated fibrous cellulose substrates with nano particles will be achieved using two basic principles; in situ synthesis of particles in the presence of fibres and adsorption of pre-formed particles from a stable dispersion. Real systems with cellulose fibres present a very complex environment, which is due to the inhomogeneous nature of the fibres themselves and due to the contents of the reaction mixture, i.e. treatment bath, therefore we will perform a thorough study of particles’ adsorption onto cellulose model films. A quartzy crystal microbalance (QCM) method will be used, where an adsorption procedure will be monitored on differently pre-treated model surfaces, representing the real ones. QCM method will allow us to determine the amount of adsorbed particles, nature of the adsorbed layer, whether they are rigid or soft and we will be able to perform multilayer build-up of particles.   Properties of the composite fibres with magnetic particles will be evaluated especially from the viewpoint of their magnetic properties (saturation magnetisation, remanent magnetisation, coercivity) and the ability to absorb electromagnetic radiation.

Post-doctoral project Development of magnetic and conductive cellulosic materials for absorption of electromagnetic waves and the results obtained present a new contribution to the field of technical polymeric materials. Combination of the cellulose substrate with magnetic nano particles presents a new approach to functionalization of biodegradable and biocompatible materials with an aim to create intelligent technical textiles. Results of the study of the fibres’ activation, in order to obtain optimal coatings of their surface and formation of particles inside their inner structure, supply new insight on the nucleation of particles on the solid surfaces, especially from the point of view of altered supramolecular structure and surface morphology of fibres.

New composite products, especially the ones which use biodegradable and sustainable materials as a base carrier, such as cellulose, present a very important group of intelligent technical materials with a high commercial potential. Final product of the post-doctoral project exhibits high applicability, since it combines inexpensive renewable material with a functional inorganic component, making it an efficient platform for the development of products with a high added value. It is this type of products which will ensure opening of new job positions and establish Slovenia and its economy as competitive and technologically advance.