Microwave characterisation of typical Australian wood-based biomass materials

The global use of woody biomass in the energy and manufacturing sectors is of growing importance. Many of the processes associated with the utilisation of woody biomass in the above application areas are underpinned by physical (e.g. density, moisture content, permeability) and structural properties (e.g. fibre and cellular structures, grain direction, porosity, evolution of porous structure during reactions) of wood. This has created a need for effective characterisation techniques for process development and quality control. Methods based on non-destructive evaluation of wood products have succeeded in monitoring the properties of wood at both macroscopic and microscopic levels. However, the use of microwave-based techniques has been limited despite their merits (technical merits, cost-effectiveness, portability, adaptability, ease of operation and health safety) over conventional methods based on x-ray, infrared, ultrasonic, and nuclear magnetic resonance. The goal of the research work presented in this thesis was to examine the interactions between complex microwave fields and typical wood structures, with the aim of developing a range of innovative microwave-based techniques for determination of physical and structural properties of wood-based materials in real-time. To achieve the broad objectives of the project, three sets of overlapping studies were carried out, namely: (i) dielectric studies, (ii) drying studies, and (iii) diagnostic tool development studies. The scope of work was however limited to typical Australian soft- and hard-wood species, specifically Slash pine (Pinus elliottii) and Spotted gum (Eucalyptus maculate).