Chars and carbonised chars were produced from three different oxygen-rich precursors (Pinus radiata wood, Phormium tenax leaf fibres, and sucrose crystals). These nongraphitisable carbons were analysed with Raman spectroscopy in order to study the nanostructural development which occurs with increasingly severe heat treatments up to approximately 1000 °C. The thermal reduction of a graphene oxide sample was similarly studied, as this is considered to involve the development of nanometre-scale graphene-like domains within a different oxygen-rich precursor. Increasing the heat treatment temperatures used in the charring and carbonisation processes, led to significant changes in a number of parameters measured in the Raman spectra. Correlations based on these parameter changes could have future applications in evaluating various char samples and estimating the heat treatment temperatures employed during their manufacture. After production heat treatment temperatures exceeded 700 °C, the Raman spectra of the carbonised chars appeared to be largely precursor independent. The spectra of these carbonised chars were similar to the spectra obtained from thermally-reduced graphene oxides, especially when compared to a wide range of other carbonaceous materials analysed using this particular methodology. Partial reduction of a graphene oxide sample due to reasonably mild laser exposures during Raman analysis was also observed.

Following a review of the literature evidence, an updated model is presented to describe the kind of nanometer-scale structures that occur in non-graphitizing carbons (also known as chars, biocarbons, and biochars) produced from the carbonization of oxygen-containing precursors (especially carbohydrates and lignocellulosic biomass). This is not intended to be a new model, because it is still essentially the same general model and concepts put forward by Franklin in 1951 and updated through integrating additional experimental evidence, ideas, and key features published over the last 64 years. The updated model uses evidence and concepts from recent publications on graphene oxide and reduced graphene oxide to assist in explaining a potential role of heteroatoms (especially oxygen) in the cross-linking, which is considered important in the development of the distinct nanostructure of non-graphitizing carbons. A three-dimensional molecular/atomic model is presented to approximate the nanostructure formed as carbonization temperatures approach 1000 °C. The development of this nanostructure over a range of carbonization temperatures is also described.

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Additive manufacturing can be a valuable tool to process polymeric composites reinforced with bio-based fibres, extending their use and opening new opportunities for more environmentally friendly materials. In this work, poly(lactic acid) (PLA) composites reinforced with regenerated cellulose fibres (lyocell) were processed into novel filaments and used for 3D printing. The Young’s modulus of the filaments increased with the addition of fibres, but substantial porosity was observed in formulations with 20 and 30 wt% of fibre content. Nonetheless, the composites were easily printed, and the formulation with 10 wt% of fibres presented the best tensile properties of 3D printed samples with average tensile strength, Young’s modulus, and strain at break of 64.2 MPa, 4.56 GPa, and 4.93%, respectively. It has been shown in this study that the printing process contributes to fibre alignment with small variations depending on the printing speed. Printed composite samples also had superior thermo-mechanical stability with a storage modulus up to 72 times higher than for neat PLA at 80 °C after the composite samples were heat-treated. In general, this work supports the potential use of regenerated cellulose fibres to reinforce PLA for 3D printing applications.

A biobased composite material with heat-triggered shape memory ability was successfully formulated for threedimensional (3D) printing. It was produced from cellulose nanocrystals and cellulose micro-powder particles within a bioderived thermally cured polyester matrix based on glycerol, citric acid, and sebacic acid. The effect of curing duration on the material's shape memory behavior was quantified by using two thermo-mechanical approaches to measure recovery: (1) displacement in three-point bending and (2) angular recovery from a beam bent at 90°in a single cantilever setup. Extending curing duration increased the material's glass-transition temperature from-26°C after 6 h to 13°C after 72 h of curing. Fourier-transform infrared spectroscopy confirmed the associated progressive conversion of functional groups consistent with polyester formation. Slow recovery rates and low levels of shape recovery (22-70%) were found for samples cured less than 24 h. Those results also indicated a high dependence on the measurement approach. In contrast, samples cured for 48 and 72 h exhibited faster recovery rates, a significantly higher recovery percentage (90-100%) and were less sensitive to the measurement approach. Results demonstrated that once a sufficient curing threshold was achieved, additional curing time could be used to tune the material glass-transition temperature and create heattriggered 3D-printed products.