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Summarization of Liquid Phase/Wet Chemical Synthesis (Sol-Gel Method…
Summarization of Liquid Phase/Wet Chemical Synthesis
Hydrothermal Method
Any heterogenous chemical reactions with the present of solvent at T>RT & P>=11 atm in a
close system
process is carried out in a hardened steel autoclave (close chamber)
Important parameters to be considered
solvent
temperature
pressure
:check: high purity
:check: controlable size & shape of desire product
:check: produce fine crystal
:red_cross: processing parameters influence properties of product
:red_cross: expensive equipment
Precipitation Method
Important Parameters:!:
reactant concentration
temperature
pH
formation of a solid product from a liquid solution
to prepare multi-component ceramic products through formation of intermediate precipitates (
hydrous oxides or oxalates
)
Sol-Gel Method
transformation of starting materials solution into
sol/gel
through chemical reaction
General stages in Sol-Gel
Hydrolisis
Condensation
Drying
Categories of Sol-Gel
Alcohol-based
Aqueous-based
:check: Homogenous
:check: High Purity
:check: Low processing T and cost
:red_cross: expensive starting materials
:red_cross: starting materials sensitive to humidity
:red_cross: long processing period
Soft Combustion Method
self-propagating high temperature synthesis
combustion
refers to
flaming (gas phase)
smouldering (solid-gas phase)
explosive rxn
highly exothermic redox chemical reaction between an
oxidizer
and a
fuel
Preparation of oxide material
metal nitrates (oxidizer)
+
fuel agent
mix these in stoichiometry
+
water to get aqueos redox mixture
combustion
ash useful oxide
Critical Factor:!:
nature of fuel
fuel oxidizer
initial furnace temperature
Advantages :check:
simple preparation
high purity of end product
good stability of metastable phase
variety formation of any size and shape of product
Nanoemulsion Method
Emulsion:question:
a mixture of two or more liquids that are immiscible (unblendable)
Substance (the dispersed phase) will disperse in the continuos phase and form a cloudy apperance
Surfactant
: to stabilize the unblendable liquids (water & organic)
How :question:
by reducing the surface tension of the immisicible liquids
but potentially toxic:!:
Types of Emulsion
Emulsion
Microemulsion
Nanoemulsion