ShadowWarrior4444
Hazard to Others
Posts: 226
Registered: 25-4-2008
Member Is Offline
Mood: Sunlight on a pure white wall.
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Sol-Gel Procedure
I had seen a forum member request a "cookbook" method for producing Sol-Gels of various sorts, and recently over the course of my research I have
found a patent that fits that descrition nicely:
United States Patent 6445861
http://www.freepatentsonline.com/6445861.html
The salient part transcribed:
"A first embodiment includes mixing 20 ml of TEOS, 20 ml of deionized water, 20 ml of ethanol, 2.5 ml of Hydrochloric acid 0.1 N, and 3 mg calcofluor
or fluorescein, to form a solution; placing the solution into a reaction chamber in a sealed chamber, for approximately 15 minutes, heating to 100
degrees C. during which solution is stirred; venting the reaction chamber by opening a gas release valve 100% for approximately 20 minutes or until
microreactor reaches 8 psig (pounds per square inch gauge, where 0 psig˜14 psi absolute) during which the solution cools at room temperature through
conduction of the microreactor, so that the temperature of the solution is approximately 80 degrees C. when removed, without using induced cooling;
placing the solution into a micro dialysis syringe; and pumping the solution into a Tygon™ tubing which holds a piece of cleaved hollow core fiber.
Although Tygon™ tubing is specified, it is noted that any tubing could be used so long as it does not react with the sol-gel material and the
sol-gel material will not stick to it."
The patent also describes in some detail which materials would be suitable for use as dopants, allowing the production of fiber optic sensors ranging
from scintillators to chemical detectors.
From my own knowledge, I believe metal alkoxides may be used instead of TEOS in this process. I can also recall Aluminum Chloride being used with
citric acid to serve as the organic ligand--further research would be required along those routes.
As a related aside, I am aware of an electrolytic method to produce a wide range of metal alkoxides as follows (methanol analogs):
Electrolysis of a completely anhydrous cell of methanol using a quaternary amine chloride as the electrolyte and the metal as the anode. (I recommend
Choline Chloride, as it is easy to obtain from nutrition suppliers, however, it is hygroscopic, and therefore a vacuum desiccators may be necessary.
I should note that alkoxide methods do not produce as much variety in Sol-Gel procedures, and as such many researchers have switched over to using
Epoxides. I personally am not well versed in those methods, (yet.) *Will be continuing his research in sol-gel technology.*
[Edited on 5-2-2008 by ShadowWarrior4444]
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solo
International Hazard
Posts: 3967
Registered: 9-12-2002
Location: Estados Unidos de La Republica Mexicana
Member Is Offline
Mood: ....getting old and drowning in a sea of knowledge
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Reference Information
Sol-gel Process in Preparation of Organic-inorganic Hybrid Materials
J. Macan;
Chemistry in industry, Vol.57 No.7-8 July 2008.
Language Craoatian
Abstracts
Organic-inorganic hybrid materials are a sort of nanostructured material in which the organic and inorganic phases are mixed at molecular level. The
inorganic phase in hybrid materials is formed by the sol-gel process, which consists of reactions of hydrolysis and condensation of metal (usually
silicon) alkoxides. Flexibility of sol-gel process enables creation of hybrid materials with varying organic and inorganic phases in different ratios,
and consequently fine-tuning of their properties. In order to obtain true hybrid materials, contact between the phases should be at molecular level,
so phase separation between thermodynamically incompatible organic and inorganic phases has to be prevented. Phase interaction can be improved by
formation of hydrogen or covalent bonds between them during preparation of hybrid materials. Covalent bond can be introduced by organically modified
silicon alkoxides containing a reactive organic group (substituent) capable of reacting with the organic phase. In order to obtain hybrid materials
with desired structures, a detailed knowledge of hydrolysis and condensation mechanism is necessary. The choice of catalyst, whether acid or base, has
the most significant influence on the structure of the inorganic phase. Other important parameters are alkoxide concentration, water: alkoxide ratio,
type of alkoxide groups, solvent used, temperature, purity of chemicals used, etc. Hydrolysis and condensation of organically modified silicon
alkoxides are additionally influenced by nature and size of the organic supstituent.
[Edited on 7-12-2008 by solo]
Attachment: Sol-gel Process in Preparation of Organic-inorganic Hybrid Materials(croatian).pdf (348kB)
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It's better to die on your feet, than live on your knees....Emiliano Zapata.
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