sol gel chemistry
DESCRIPTION
TRANSCRIPT
SOL-GEL TECHNIQUE
A SOL IS A DISPERSION OF THE SOLID PARTICLES (~ 0.1-1 ΜM) IN A LIQUID
A GEL IS A STATE WHERE BOTH LIQUID AND SOLID ARE DISPERSED IN EACH OTHER, WHICH
PRESENTS A SOLID NETWORK CONTAINING LIQUID COMPONENTS. THE SOL-GEL COATING PROCESS
USUALLY CONSISTS OF 4
STEPS:
(1) THE DESIRED COLLOIDAL PARTICLES ONCE DISPERSED IN A LIQUID TO FORM A SOL.
(2) THE DEPOSITION OF SOL SOLUTION PRODUCES THE COATINGS ON THE SUBSTRATES BY SPRAYING, DIPPING OR
SPINNING.
(3) THE PARTICLES IN SOL ARE POLYMERIZED THROUGH THE REMOVAL OF THE STABILIZING COMPONENTS AND PRODUCE A
GEL IN A STATE OF A CONTINUOUS NETWORK.
(4) THE FINAL HEAT TREATMENTS PYROLYZE THE REMAINING ORGANIC OR INORGANIC COMPONENTS AND FORM AN
AMORPHOUS OR CRYSTALLINE COATING[1-4]
COLLOIDS=MICROSCOPIC MATERIALS+DISPERSION PHASE
• A COLLOID IS A SUBSTANCE MICROSCOPICALLY DISPERSED THROUGHOUT ANOTHER SUBSTANCE.
• THE DISPERSED-PHASE PARTICLES HAVE A DIAMETER OF BETWEEN APPROXIMATELY 1 AND 1000 NANOMETERS.[2] SUCH PARTICLES ARE NORMALLY INVISIBLE IN AN OPTICAL MICROSCOPE, THOUGH THEIR PRESENCE CAN BE CONFIRMED WITH THE USE OF AN ULTRA MICROSCOPE OR AN ELECTRON MICROSCOPE.
LIGHT BEING SHINED THROUGH WATER AND MILK. THE LIGHT IS NOT REFLECTED WHEN PASSING THROUGH THE WATER BECAUSE IT IS NOT A COLLOID. IT IS HOWEVER REFLECTED IN ALL DIRECTIONS WHEN IT PASSES THROUGH THE MILK, WHICH IS COLLOIDAL.
PRECURSOR ORGANOMETALLIC COMPOUND
(M-OR)
ORGANOMETALLIC COMPOUND(M-OR) +WATER (H20)
METAL-OXIDE SOLUTION M-OH +R-OH
COATING XEROGEL
GELLING WET GEL
PRECIPITATING UNIFORM PARTICLES
Sol
SOL-GEL FOR NORMAL COATING
SOL GEL FOR SPIN COATING
ADVANTAGES OF SOL-GEL METHOD
( SIMPLE , ECONOMIC & EFFECTIVE )
HIGHLY PURE PRODUCTS
UNIFORM NANOSTRUCTURE &EASILY SHAPEABLE
HAVE LOW TEMP. SINTERING CAPABILITY
DISADVANTAGES OF SOL-GEL TECHNIQUE
SUBSTRATE dependentNON_UNIFORM THERMAL EXPANSION
APPLICATIONS
CAPACITORS IN PIEZOELECTRICITY APP.
TRANSPARENT SEMICONDUCTORS
GLASSES ,LENSES
NANOPOWDER FOR DENTAL &BIOMEDICAL APP.
PROTECTION WITH HARD COAT