In this work, stability of dispersions and foams containing CaCO₃-based pigments and cellulose nanofibrils (CNF) was evaluated with the aim to reveal the mechanisms contributing to the overall stability of the selected systems. The utmost interest lies in the recently developed hydrocolloid hybrid CaCO₃ pigments and their potential to form bionanocomposite structures when incorporated with CNF. These pigments possess a polyelectrolyte layer deposited on the surface of the particle which is expected to enhance the compatibility between inorganic and organic components. Stability assessment of both dispersions and foams was conducted using turbidity profile scanning. In dispersions, CNF provides stability due to its ability to form a firm percolation network. If surface-modified pigments are introduced, the favourable surface interactions between the pigments and CNF positively influence the stability behaviour and even large macro-size pigments do not interfere with the stability of either dispersions or foams. In foams, the stability can be enhanced due to the synergistic actions brought by CNF and particles with suitable size, shape and wetting characteristics resulting in a condition where the stability mechanism is defined by the formation of a continuous plateau border incorporating a CNF network which is able to trap the inorganic particles uniformly.

The excellent functional properties of graphene and micro-nanofibrillated cellulose (MNFC) offer plenty of possibilities for wide ranging applications in combination as a composite material. In this study, flexible graphene/microfibrillated cellulose (MFC) composite films were prepared by a simple method of co-exfoliation of graphite in an MFC suspension by high-shear exfoliation. We show that pristine graphene, without any chemical treatment, was homogeneously dispersed in the MFC matrix, and the produced composites showed enhanced thermal, electrical and mechanical properties compared to a non-co-exfoliated control. The film properties were studied by XPS, XRD, Raman, SEM, FTIR, TGA, nitrogen sorption, UV-vis spectroscopy, optical and formation analysis tests. At 0.5 wt% loading, the specific surface area of graphene/MFC composites increased from 218 to 273 m² g⁻¹ while the tensile strength and Young's modulus for the graphene/MFC composites increased by 33% and 28% respectively. Thermal stability was enhanced by 22% at 9 wt% loading and the composites showed a high electrical conductivity of 2.4 S m⁻¹. This simple method for the fabrication of graphene/MFC composites with enhanced controlled functional properties can prove to be industrially beneficial, and is expected to open up a new route for novel potential applications of materials based largely on renewable resources.