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2. Sol-Gel Technology and Solid State Reaction
Prepared by:
Adnan Majeed
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3. Table of contents
Introduction
Sol and Gel
Sol gel process
Factors influencing sol-gel process
Applications
Advantages
Limitations
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4. Introduction
• Sol gel processing designates a type of solid material synthesis,
performed in a liquid and at low temperature.
• It’s a typical nanotechnology. Because all gel products contain
nanoparticles or nanocomposites.
• Synthesis schemes used depends on initial precursors.
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Sol and Gel
Sol is a stabledispersionof colloidalparticlesor polymers ina solvent.
Consist of liquidwithcolloidalparticleswhichareno dissolved,butdo not
sediment.
Gel is a three dimensional continous network which encloses liquidphase.

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Suspension of finesolidparticles or liquid droplets in a gas.
Aerogel
Drying is performed atsupercriticalconditions, network structuremay be retained
and a gel withlargepores may be found.
Xerogel
Gelis dried by evaporation ,capillaryforceswillresultinshrinkage, the gel network
collapse.
Aerosol

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Xerogel
Aerogel

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Sol gel process
 Hydrolysisandcondensationofmolecule
 Gelation
 Ageing
 Drying
 Firing
 Densification

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Factors influencing sol-gel process
• Parameters influencing hydrolysis
• Typeand amount ofcatalyst
• Parameters influencing condensation
• Type ofprecursor
• pH
• Type ofsolvent

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Applicationsof Sol-Gel Technology
• Optical and photonic applications
• Mechanical applications
• Biomedical application
• Bioreactors
• Chemical Applications
• Electronic applications
• Thermal applications

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 Can produce thin bond-coating to provide excellentadhesion between the
metallic substrate andthe top
 Can produce thick coating to provide corrosion protection performance.
 Can easily shape materials into complexgeometries in a gel state.
 Can producehigh purityproducts.
Advantages

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 Can havelow temperature usually200-600°C.
 Can providea simple,economicand effectivemethod to
produce high quality coatings.
 Through sol-gel processing, homogeneous, high-purity
inorganic oxide glasses can be made.

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Weakbonding
High permeability
Difficulty in controlling porosity
Substratedependency
Limitations

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Solid-state reaction
• The solid-state reaction route is the most widely used
method for the preparation of polycrystalline solids from a
mixture of solid starting materials.
• The factors on which the feasibility and rate of a solid state
reaction depend include, reaction conditions, structural
properties of the reactants, surface area of the solids,
their reactivity and the thermodynamic free energy change
associated with the reaction.

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Outline of the experimental procedure
Reagents
• These are the solid reactants from which it is proposed
to prepare a solid crystalline compound.
• The selection of reactant chemicals depends on the
reaction conditions and expected nature of the
product.
• The reactants are dried thoroughly prior to weighing.
• As increase in surface area enhances the reaction
rate, fine grained materials should be used if possible.

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• After the reactants have been weighed out in the required amounts, they
are mixed.
• For manual mixing of small quantities, usually an agate mortar and
pestle are employed.
• Sufficient amount of some volatile organic liquid –
preferably acetone or alcohol – is added to the mixture to aid
homogenization.
• This forms a paste which is mixed thoroughly. During the process of
grinding and mixing, the organic liquid gradually volatilizes and has usually
evaporated completely after 10 to 15 minutes.
Mixing

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• For the subsequent reaction at high temperatures, it is necessary to
choose a suitable container material which is chemically inert to
the reactants under the heating conditions used.
• The noble metals, platinum and gold, are usually suitable.
• Containers may be crucibles or boats made from foil.
Container material

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• The heating program to be used depends very much on
the form and reactivity of the reactants.
• In the control of either temperature or atmosphere, nature
of the reactant chemicals are considered in detail.
• A good furnace is used for heat treatment.
Heat treatment

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The product materials are analyzed using various
characterization techniques such as X-ray
diffraction (XRD), scanning electron microscopy
(SEM), transmission electron microscopy (TEM), etc.
Analysis

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