Ferritic ODS steels show improved high temperature strength and irradiation tolerance compared with conventional ferritic steels, and are one of the key potential materials for fusion blanket structural applications. The processing of ODS steels is critical to their subsequent performance; however knowledge of the optimum processing approaches for these alloys is not complete. The microstructural evolution of ODS steels containing Y₂O₃ and other additions during manufacture has been investigated and the processing conditions optimised based on microstructural and mechanical investigations. Ferritic powders with Y₂O₃ and other additions were investigated, primarily using analysis on the micro- and nano-scale, with an emphasis on identifying the requirements for homogenization of the Y within the steel matrix. The Y₂O₃ dispersion and subsequent development of the nano-precipitates during thermal treatment was investigated using in-situ neutron diffraction. The nano-precipitates were resolved at approximately 900◦C after 1hr, with coarsening and/or re-precipitation progressively increasing at higher temperatures. A significantly increased number density of nano-precipitates (∼2x10²³m−3 to ∼7x10²³m−3) was established by hot isostatically pressing an Fe-14Cr-3W-0.2Ti0.25Y₂O₃ alloy at 950◦C compared with more traditional temperatures at 1150◦C, attributed to the increased coarsening and/or re-precipitation of the nano-precipitates at the higher temperatures. The influence of the mechanical alloy (MA)ing conditions on bulk mechanical properties was investigated using four point bend. The highest fracture toughness of ∼55MN/m^3/2 and ultimate strength of ∼1450MPa was achieved under conditions that minimised the mechanical alloying time and increased the average final size of the powders. An Fe-14Cr-3W-0.2Ti-0.25Y₂O₃ (wt%) ODS alloy manufactured under optimised conditions showed a bi-modal grain structure size distribution and had a comparatively high yield strength of >1200MPa at 20◦C and >330MPa at 700◦C. The grain structure and high yield strength were attributed to the random distribution of 25nm radius of gyration (R_g) Y, Ti and O rich nano-precipitates randomly dispersed throughout the alloy. Long term thermal ageing (750hr at 1000◦C) reduced the room temperature yield strength and increased the proportion of larger grains in the bi-modal distribution, but high temperature yield strength was remarkably stable.

<p dir="ltr">Flow patterns in a toroidal-fluidized bed granulator were analyzed using the effects of wall friction on the bed pressure drop. Toroidal flows were generated by directionally inclined jets from a radially-slotted distributor plate. The relatively small open area of the slotted distributor provides significant jet velocities, inducing toroidal flow even at relatively low superficial airflows. In this aspect, the process is of interest to fluidized bed granulation wherein the toroidal flow can assist spray flux without excessive elutriation. The current dissertation explores the effect of toroidal multiphase flow on wall friction and pressure drop. Relevant process parameters include particle size, airflow, temperature, and bed inventory. Particle size growth is especially important in fluidized bed granulation; airflow and temperature parameters must balance with the binder spray enthalpy; and the bed inventory is relevant to capacity and throughput analyses. An empirical process model was developed to guide fluidized bed granulation with a consistent pressure-drop balance across the distributor plate and product bed during the granulation process.</p><p dir="ltr">Fluidized bed granulation integrates several process transformations into a single unit operation. Transformations include powder fluidization, atomization of binder solution and wetting of the fluidized powder, growth and consolidation of granules, drying, and discharge of the fluidized product. The balance of the binder addition and drying rates is used in combination with fluidization (i.e., flow field) parameters to control the process. Balanced control of fluidization can be challenging in the context of micronized powders, prone to elutriation, for example as required in some pharmaceutical formulations. This manuscript explores the effects of thermodynamic and flow field parameters on the size and shape distributions of a challenging pharmaceutical formulation. Pre-wetting the powder mixture prior to fluidization effectively reduces elutriation, stabilizes the fluidization process, and results in narrower granule size distributions. Optimizing blowback pressure can further stabilize the process. These strategies contribute to improved control of fluidized bed granulation, particularly for challenging pharmaceutical formulations, enhancing both product quality and process efficiency.</p><p dir="ltr">A regime map for a challenging pharmaceutical formulation was developed to link operational parameters to granule characteristics, establishing a stable processing space that connects moisture gain with particle size and shape distributions and uniformity. This comprehensive framework supports scale-up and reliable application of fluid bed granulation in pharmaceutical and related industries, contributing to improved process efficiency and product quality. The findings presented here advance the scientific understanding of toroidal fluid bed granulation and offer practical and actionable strategies for controlling this process.</p>