Abstract:
XRD, SEM, and Particle Size Analysis was
performed on nanocrystalline Titanium Dioxide
powders synthesized via sol-gel methods (specifically:
solvothermolysis of Titanium Butoxide). The use of solgel
TiO2 as a feedstock in the initial stages of the
Hydrogen Assisted Magnesiothermic Reduction (HAMR)
process was investigated for the production of lowoxygen
Titanium metal. The addition of dopant rareearth
element Y was investigated to determine if such
species affect the HAMR process. The evolution of
HAMR intermediate and product phases in response to
the reduction parameters of temperature, duration,
and Hydrogen partial pressure was studied with XRD
and SEM techniques.
The literature-studied HAMR phase-transition
pathway was confirmed by XRD, with early formation of
magnesium titanite phases that subsequently
decreased with the formation of greater levels of α-Ti
(with dissolved oxygen in solid solution) or Ti2O phases.
The presence of two distinct magnesium titanites were
observed to be depth-dependent, with leeching
experiments demonstrating higher levels of Mg2TiO4 at
particle surfaces and higher levels of MgTiO3 within
particle cores. Traces of β-Ti were observed, indicating
occasional extensive deoxygenation of TiO2. Evidence
that Y-doping may have accelerated the HAMR process
was observed in powders with similar size distributions.
Particle cross-sections demonstrated a significant
departure from the literature morphologies, with
significant interior remodelling and a lack of distinct
phase migration fronts. Microstructure differences
were posited to arise from low-temperature formation
of the precursor, nanocrystalline TiO2. Further
investigation and modelling of the observed, new
microstructures, contrasted against literature
investigations of highly-crystalline TiO2, was identified
as a potential area of novelty for future work. A
leeching procedure was established to inform laterstage
HAMR work, and experiment improvement
recommendations were made for future work.