Electron microscopy of some inorganic crystals with novel morphologies
Abstract
This project concerns crystal growth of some inorganic crystals which have novel
morphologies. In order to study their crystal growth routes and further reveal their crystal
growth mechanism, intermediate samples were collected and analysed, including samples
produced after reduced reaction time, with different concentration of reactant or at reduced
reaction temperature. The analysis was mainly completed by scanning electron microscopy
and high resolution transmission electron microscopy. Other complementary techniques are
powder X-ray diffraction, energy dispersive X-ray spectroscopy, selected area electron
diffraction, mass spectrometry, inductively coupled plasma - optical emission spectrometry
and photoelectrochemical measurement.
Investigated inorganic crystals include hematite nanotubes and nanorings, silver dendrites
and copper dendrites, and graphene-based metal oxides. Hematite nanotubes and nanorings
can be fabricated through hydrolysis of ferric chloride in different concentrations of
phosphate via hydrothermal reaction. Intermediate samples at a range of different times were
collected and characterised. It was revealed that hematite nanocrystallites form from
decomposition of β-FeOOH nanorods, and that the final morphology depends on the
competition between aggregation of β-FeOOH nanorods and decomposition into hematite
nanocrystallites. Silver dendrites and copper dendrites can be produced via replacement
reaction at room temperature. When synthetic conditions were changed, dendrites of different
morphologies can be synthesised. The crystal growth direction and growth mechanism were
investigated. Metal oxides such as manganese oxide nanoparticles and nickel oxide hollow
particles can form on electrochemically exfoliated graphene via hydrolysis and
polymerisation process. It was found that polymerisation is a vital process in the formation of
metal oxides on graphene since polymers have multiple interaction sites with the surface of
graphene. The intermediate samples and growth process were studied in detail.
Type
Thesis, PhD Doctor of Philosophy
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