SOL-GEL METHOD •The sol-gel process may be described as: ”Formation of an oxide network through hydrolisis and polycondensation reactions of a molecular precursor in a liquid.”

SOL-GEL METHOD

•The sol-gel process may be

described as: ”Formation of an oxide network through

hydrolisis and polycondensation reactions of a molecular

precursor in a liquid.”

• Sol is a stable dispersion of colloidal particles or polymers in a solvent;

• Gel consists of a three dimensional

network, which contains a liquid phase.

SOL-GEL METHOD

Solution :

Organic compounds of elements (alkoxides, esters), or inorganic salts (nitrates, chlorides);

Solvent – usually alcohol (methanol, ethanol)

Water

Catalyst of chemical reactions (HCl, NaOH);

SOL-GEL METHOD

Basic chemical reactions

hydrolysis(1)

polycondensation(2)

(OR)₃SiOH + HOSi(OR)₃ (OR)₃Si-O-Si(OR)₃ + H₂O (2)

O C ₂H ₅ C ₂H ₅O S i O C ₂H ₅

O C ₂H ₅

+

O C ₂H ₅ C ₂H ₅O S i O H

O C ₂ H ₅

H ₂ O + C ₂ H ₅O H

O C ₂H ₅ C ₂H ₅O S i O H

O C ₂H ₅ +

O C ₂H ₅ S i O H

O C ₂H ₅

O C ₂H ₅ S i C ₂H ₅O

O C ₂H ₅

O C ₂H ₅ S i O H O C ₂H ₅

O ⁺ H ₂O

O C ₂H ₅

Hydrolysis and polycondensation depend mainly on:

 Kind of catalyst, pH of solution;

 Temperature; ;

 Amount of solvent and water;

 Ligand structure and steric effect;

SOL-GEL METHOD

Basic physical transformation:

solution

sol

gel

Solid body

40 – 250^oC drying; evaporation of water and solvent;

250 – 400^oC oxidation of organic matter;

400 – 1000^oC removal of OH groups, densification;

Application..

• Obtaining of materials impossible to produce another methods;

• Homogeneity in molecular scale due to reaction in solution;

• very high purity of obtained materials (because substrates are p.a.);

• Low process temperature in comparison with other methods (i.e. melting of glass);

• Obtaining thin layers on different base materials (glass, metal, plastic);

Benefits

Disadvantages

• Expensive starting compounds;

• Difficulties to obtaining large scale monolits, free from crack;

• Sol-gel reactions are not reversible and

impossible to completely inhibit;

COATING TECHNIQUES (main)

 dipping dipping

 spinning spinning

 spraying spraying

 glazing glazing

 brush painting brush painting

 roller coating roller coating

 screen printing screen printing

Dip coating

Dip coating techniques can be described as a process where the substrate to be coated is immersed in a liquid and then withdrawn with a well-defined withdrawal

speed under controlled temperature and atmospheric conditions. The coating thickness is mainly defined by the withdrawal speed, by the solid content and the

viscosity of the liquid.

Stages of the dip coating process

Glazing

Glazing techniques can be described as a process where the substrate to be coated is glazed with a liquid. The coating thickness is mainly defined by the sol viscosity

and depression angle of coated material.

Glazing process ^zol

powłoka

podłoże

wanna

sol

coated material layer

Spinnig

Spinning techniques can be described as a process where the layer is formed by centrifugal force on spinning substrate; The coating thickness and quality is mainly

defined by the sol viscosity and centrifugal driving force.

.

Spinning process

nanoszona

warstwa podłoże

layer coated material

sol

Spraying

Spraying techniques can be described as a process where the layer is formed by spraying sol on the substrate. The coating thickness and quality is mainly defined by

the sol viscosity and worker talent.

.

aerograph

WHAT ARE HYBRIDS ?

S i O S i O S i O S i O

C C H

O O

C C H

H H

H H

O

H C H

H H

H

Hybrid material - any organic-inorganic or bio-mineral system in which at least one of the components, organic or inorganic, is present with a size scaling from tenths to tens of nanometers.

Components making up the hybrids could be molecules, oligomers or polymers, aggregates and even particles.

CLASSIFICATION OF HYBRIDS

(following the nature of chemical bonding between the organic and inorganic species criterion)

Class I: Includes hybrids systems where one of the component (organic, biologic or inorganic), which can be molecules, oligomers or polymers is entrapped within a network of the other component.

The systems of this kind are essentially based on Van der Walls, hydrogen bonding or electrostatic interactions

Class II: Gathers the hybrids materials where the inorganic and organic parts are chemically bonded by a covalent or iono-covalent bonds

ORMOCER

ORMOCER ® ® s s

ORganically MOdified CERamics – inorganic-organic hybrid materials

on the molecular scale

Si

O O

O O

Si O O

Al., Ti, Zr O O O

Si R

(R)

Si

functional groups

(1) heteroatoms in

inorganic structures (2)

organic crosslinking inorganic silica (4)

network (3)

STRUCTURE’S ELEMENTS

Structural units of inorganic-organic hybrid are connected by strong covalent bonds.

The building units of these hybrid polymers base on different types of precursor molecules.

These precursors can be classified by their network forming or modifying roles.

Basically four different types of precursors can be used for the synthesis of hybrid polymers …

TYPES OF PRECURSORS

OF HYBRID MATERIALS

TYPES OF PRECURSORS TYPES OF PRECURSORS

TYPE 1: inorganic network formers, alkoxides of Si (TMOS, TEOS), Al (Al-tri-sec-butylate), Ti (Ti-isopropylate) and Zr (Zr- butylate); TEOS Si(OCTEOS Si(OC₂₂HH₅₅))₄₄

TYPE 2: inorganic network formers with organic non-reactive group; phenyltriethoxysilanephenyltriethoxysilane (PhTES) (PhTES)

[(OC[(OC₂₂HH₅₅))₃₃Si(CSi(C₆₆HH₅₅)])]

TYPE 3: inorganic network formers with reactive organic group for cross linking/polymerization reactions;

3–glycidoksypropyltrimethoxysilane 3–glycidoksypropyltrimethoxysilane ((GPTMSGPTMS)) [(OCH

[(OCH₃₃))₃₃Si(CHSi(CH₂₂))₃₃OCHOCH₂₂CHOCH]CHOCH]

TYPE 4: organic monomers which can react via chemical cross linking or polymerization reactions with modified metal alkoxides;

 Protective coatings for sensitive surfaces (scratch and abrasion resistance)

 Increasing chemical resistance (corrosion protection)

 Barrier layers for gases, solvents, flavors, ions

APLICATIONS …

 Decorative coatings

 Antireflective coatings

APLICATIONS …

 Hydrophilic/-phobic and oleophobic functions (antiadhesive coatings)

 Antistatic coatings

 Sensor layers (for gases and ions)

 Adhesive systems (e.g. for optical fibers)

 Doped optical coatings for photonics

 Powder coatings and water-based lacquers

APLICATIONS …

alkoxides

hydrolysis + condensation

water, catalyst

alcohol, water

SOL GEL

dip- spray-

spin- coating

wet film substrate

temperature,

radiation alcohol, water

R_nSi(OR’)_4-n

Si-, Al-, Zr-alkoxides etc.

coating

SOL-GEL PROCESSING SCHEME FOR ORMOCER®

COATINGS