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) Si(OR)4 +H2O (OR)3SiOH + ROH polycondensation(2) (OR)3SiOH + HOSi(OR)3 (OR)3Si-O-Si(OR)3 + H2O (2)

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 solution sol gel Solid body Basic physical transformation: 40 – 250oC drying; evaporation of water and solvent; 250 – 400oC oxidation of organic matter; 400 – 1000oC removal of OH groups, densification; solution sol gel Solid body

Application..

Benefits 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);

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 spinning spraying glazing brush painting roller coating screen printing

Dip coating Stages of the dip coating process Dip coating techniques can be described as a process where the substrate to be coated is immersed in a liquid and then withdrawn with a well-defined withdrawal speed under controlled temperature and atmospheric conditions.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 sol Glazing process coated material layer 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. sol Glazing process coated material layer

Spinnig Spinning process coated material sol layer 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 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 ? 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®s ORganically MOdified CERamics – inorganic-organic hybrid materials on the molecular scale

STRUCTURE’S ELEMENTS O O R Al., Ti, Zr Si O O O (R) Si O O Si Si O O functional groups (1) O O R heteroatoms in inorganic structures (2) Al., Ti, Zr Si O O O (R) Si organic crosslinking (4) O O inorganic silica network (3) Si Si O O

TYPES OF PRECURSORS OF HYBRID MATERIALS 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 TYPE 1: inorganic network formers, alkoxides of Si (TMOS, TEOS), Al (Al-tri-sec-butylate), Ti (Ti-isopropylate) and Zr (Zr-butylate); TEOS Si(OC2H5)4 TYPE 2: inorganic network formers with organic non-reactive group; phenyltriethoxysilane (PhTES) [(OC2H5)3Si(C6H5)] TYPE 3: inorganic network formers with reactive organic group for cross linking/polymerization reactions; 3–glycidoksypropyltrimethoxysilane (GPTMS) [(OCH3)3Si(CH2)3OCH2CHOCH] TYPE 4: organic monomers which can react via chemical cross linking or polymerization reactions with modified metal alkoxides;

APLICATIONS … 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

SOL-GEL PROCESSING SCHEME FOR ORMOCER® COATINGS RnSi(OR’)4-n Si-, Al-, Zr-alkoxides etc. alkoxides water, catalyst hydrolysis + condensation alcohol, water SOL GEL substrate dip- spray- spin- coating wet film temperature, radiation alcohol, water coating