08 sol-gel - Sol-Gel Methods Sol-Gel methods are...

Info iconThis preview shows pages 1–7. Sign up to view the full content.

View Full Document Right Arrow Icon
Sol-Gel Methods Sol-Gel methods are increasingly applied for ceramic materials Fabrication of Powders, Fibers Thin layers, Monoliths It always starts with a dispersed colloidal system in an aqueous or organic dispersing medium/solvent. Each colloid system can be in either one of the following two states Sol , i.e. colloidal dispersion Gel , i.e. gelled mass (jelly)
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Overview and definitions Sol colloidal particles can move freely Gel three dimensional network connects particles – free movement blocked. – jelly stiffness
Background image of page 2
Sol-Gel-methods increase particle size from homogeneous solution (molecular size) to solid gels. Strongly reduced temperatures Biggest advantage is homogeneity – solution/sol starts at a molecular level Even more important for engineered materials that decompose or phase separate during high temperature fabrication. b t 200 diff t id t d About 200 different oxide systems were prepared successfully by sol-gel
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Coagulation Transform sol to gel. Peptisation Many gels (not all) can be reversed into sols Reversible Colloid: ol el Koagulation   Coagulation Sol Gel Peptisation  reversible Colloid: Irreversible Colloid: ol el Koagulation Coagulation Sol Gel
Background image of page 4
Chemical Sol-Gel Methods Monomer solution Particle synthesis Synthesis cross linking cross linking cross linking Branched polymers Uniform particles Linear polymers olymer etwork Main reactions ydrolyses of alkoxides e(OR)x = Alkyl (CH3 C2H5 )) Particle network Aggregate- network Polymer- network 1. Hydrolyses of alkoxides Me(OR)x (R Alkyl (CH3, C2H5, . ..)) 2. Condensation
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Influence of preparation method Influence of pH-value on crosslinking Hydrolysis of Tetra ethoxy silane i(OR) ith R C (Si(OR) 4
Background image of page 6
Image of page 7
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 03/04/2010 for the course MSE 6448 taught by Professor Sigmund during the Spring '10 term at University of Florida.

Page1 / 24

08 sol-gel - Sol-Gel Methods Sol-Gel methods are...

This preview shows document pages 1 - 7. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online