User talk:Melissamoz/sandbox

My edits to the following paragraph: BEFORE: Silica Aerogel Synthesis

Silica aerogels are typically synthesized by using a sol-gel process where the first step is the creation of a colloidal suspension of solid particles known as a “sol”. The process starts with a liquid alcohol such as ethanol which is mixed with a silicon alkoxide precursor, such as tetramethoxysilane (TMOS), tetraethoxysilane (TEOS), and polyethoxydisiloxane (PEDS) are often used as precursors (earlier work used sodium silicates) [45]. The solution of silica and a catalyst is mixed and allowed to gel. Silica aerogel is made by the creation of colloidal silica. A hydrolysis reaction forms particles of silicon dioxide forming a sol solution.[46] The oxide suspension begins to undergo condensation reactions which result in the creation of metal oxide bridges (either M–O–M, “oxo” bridges or M–OH–M, “ol” bridges) linking the dispersed colloidal particles.[47] When this interlinking has stopped the flow of liquid within the material, this is known as a gel. This process is known as gelation. These reactions generally have moderately slow reaction rates, and as a result either acidic or basic catalysts are used to improve the processing speed. Basic catalysts tend to produce more transparent aerogels and minimize the shrinkage during the drying process and also strengthen it to prevent pore collapse during drying. [46] AFTER:

Silica aerogels are typically synthesized by using a sol-gel process. The first step is the creation of a colloidal suspension of solid particles known as a “sol”. The precursors are a liquid alcohol such as ethanol which is mixed with a silicon alkoxide, such as tetramethoxysilane (TMOS), tetraethoxysilane (TEOS), or polyethoxydisiloxane (PEDS) (earlier work used sodium silicates). [45] The solution of silica is mixed with a catalyst and allowed to gel. A hydrolysis reaction forms particles of silicon dioxide forming a sol solution.[46] The oxide suspension begins to undergo condensation reactions which result in the creation of metal oxide bridges (either M–O–M, “oxo” bridges or M–OH–M, “ol” bridges) linking the dispersed colloidal particles.[47] When this interlinking has stopped the flow of liquid within the material, this is known as a gel. This process is known as gelation. These reactions generally have moderately slow reaction rates, and as a result either acidic or basic catalysts are used to improve the processing speed. Basic catalysts tend to produce more transparent aerogels and minimize the shrinkage during the drying process and also strengthen it to prevent pore collapse during drying. [46]

NOTE: The paragraph seems to explain the same process twice.. going from a sol to a gel. It's a bit confusing and I think there may be some overlap.