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@PHDTHESIS{Schler:908576,
author = {Schüßler, Martina Claudia Beate},
title = {{O}n the {F}ormation {M}echanism of {A}morphous
{C}arbonates: {P}recursors in {N}onclassical
{C}rystallization and for {F}unctional {M}etal {O}xides},
school = {Erlangen},
type = {Dissertation},
address = {Erlangen},
reportid = {FZJ-2022-02700},
pages = {188 p.},
year = {2022},
note = {Dissertation, Erlangen, 2022},
abstract = {This work is dedicated to the highly discussed formation
mechanism of amorphous calcium carbonate (ACC), its role in
nonclassical crystallization, and amorphous carbonates as a
precursor for functional metal oxides. Decrypting the
formation mechanism of ACC provides a new environmentally
benign synthesis pathway for complex hierarchically
structured nanomaterials. Therefore, different ACC synthesis
pathways and the corresponding ACC is studied: ACC synthesis
via carbonate released by hydrolysis, manual rapid mixing of
calcium chloride and sodium carbonate, and controlled
turbulent mixing in a stopped-flow device. Particularly
three-dimensional nanonetworks of ACC are received, applying
the stopped-flow synthesis approach, which indicates a
formation mechanism via liquid-liquid phase separation and
spinodal decomposition. Moreover, the existence of a
liquid-condensed phase in the formation mechanism is
emphasized by the break-down of the nanonetwork to
energetically favored droplets over time and a pH-dependent
hydration rate of ACC. The extraordinary synthesis pathway
via liquid-liquid phase separation is further transferred to
other alkaline earth and transition metal carbonates.
Thereby, three-dimensional highly hydrated amorphous
carbonates or hydroxycarbonates, depending on the relevant
solubility products, are accessible, demonstrating the
potential and applicability of the mechanism studied herein.
The cation hydration enthalpy and radius are suggested to
limit the ability of liquid phase formation. Amorphous zinc
carbonate hydroxide reveals a peculiar pH dependency,
regarding its morphology, composition, and hydration.
Moreover, it serves as a tuneable precursor for zinc oxide
formation. Besides nanostructured zinc oxide offering a high
surface area, copper oxide is synthesized via a stable
amorphous copper carbonate hydroxide precursor, georgeite.
In contrast to the highly structured porous nanonetworks,
smooth georgeite thin films are formed by assembly of the
liquid-condensed phase at the air-water interface, utilizing
the stabilizing effect of the additive polyacrylic acid
(PAA) on georgeite. The obtained high surface area is
particularly suited for catalytical applications, cobalt
oxide, which was synthesized via an amorphous cobalt
carbonate hydroxide precursor, shows promising properties as
an electrode material in water-splitting. Further, the
synthesis approach via a liquid-condensed phase is utilized
for coatings. The results clearly demonstrate that liquid-
condensed phases are a powerful concept towards new
synthesis approaches for functional metal oxides.},
cin = {JCNS-FRM-II / MLZ},
cid = {I:(DE-Juel1)JCNS-FRM-II-20110218 / I:(DE-588b)4597118-3},
pnm = {6G4 - Jülich Centre for Neutron Research (JCNS) (FZJ)
(POF4-6G4)},
pid = {G:(DE-HGF)POF4-6G4},
experiment = {EXP:(DE-MLZ)KWS1-20140101 / EXP:(DE-MLZ)KWS3-20140101},
typ = {PUB:(DE-HGF)11},
url = {https://juser.fz-juelich.de/record/908576},
}