Silica and silica-like films and method of production
A method of producing a silica or silica-like coating by forming a precursor formulation from oligomeric organosilicate. The precursor formulation is coated on a substrate as a continuous liquid phase. The precursor formulation is then cured in an ammoniacal atmosphere to produce a continuous, interconnected, nano-porous silica network.
1. A method of forming a silica or silica-like film coated on a substrate including the steps of:
producing a precursor formulation having a ratio of reagents of 1.0 part by volume oligomeric organosilicate; 0.1 part by volume water; 10.0 parts by volume;
coating a substrate with the precursor formulation; and
curing the precursor formulation onto the substrate in an ammoniacal environment.
2. The method of claim 1 wherein the precursor formulation is formed by adding an oligomeric organosilicate comprising silicic acid tetraethyl ester homopolymer, tetraethoxysilane and ethanol, to the solvent comprising an alcohol.
3. The method of claim 1 wherein the coating is performed by spin coating or dipping.
4. The method of claim 1 wherein the coating further includes allowing the coating to settle before curing.
5. The method of claim 1 wherein the film comprises a continuous, interconnected, nano-porous silica network.
6. The method of claim 1 wherein the curing is carried out by placing the coated substrate in a closed ammoniacal environment.
7. The method of claim 6 wherein the ammoniacal environment contains water, ammonia and alcohol.
8. The method of claim 7 wherein the alcohol contained in the ammoniacal environment is the same alcohol as used in the formation of the precursor formulation.
9. The method of claim 1 further including controlling the alcohol content to control characteristics of the film.
10. The method of claim 7 further including controlling the alcohol content in the ammoniacal environment to control characteristics of the film.
11. The method of claim 1 further including controlling a pore size of the film by controlling the alcohol content and type in the precursor formulation.
12. The method of claim 7 further including controlling a pore density of the film by controlling the alcohol content and type in the ammoniacal environment.
13. The method of claim 7 further including controlling a porosity of the film by controlling the alcohol content and type in the precursor formulation and alcohol content and type in the ammoniacal environment.
14. A method of forming a silica or silica-like film coated on a substrate including the steps of:
producing a precursor formulation having a ratio of reagents of 1.0 part by volume oligomeric organosilicate; 0.1 part by volume water; 10.0 parts by volume;
coating a substrate with the precursor formulation;
placing the coated substrate in a closed solvent environment;
establishing equilibrium between the alcohol in the precursor formulation and the solvent environment; and
curing the precursor formulation onto the substrate in an ammoniacal environment containing solvent by introducing ammonia vapour and water vapour to the closed solvent environment.
15. The method of claim 1 wherein the oligomeric organosilicate is not silicic acid tetramethyl ester homopolymer.