I have residue of solid silica and I want amorphous nano-silica in 4-6 hours? Which technique or process will be more efficient to bring down the size of silica below 100nm in 4-6 hours?
Is solid silica available in powder form or can you pulverize it? Once you have them in a size range of 45- 75 microns, you can pass it though a flame of a flame spraying machine and deposit them in chilled water. Chances are high that you will receive a significant amorphous fraction.
P.P. Bandyopadhyay
Yes, solid silica is available in powder form
Gourav Kumar Dewangan
The normal route to nanosized SiO2 is via flame pyrolysis of SiCl4. So, first convert your SiO2 to SiCl4 as per the attached patent and then flame pyrolyze as per the attached paper. Alternatively order fumed silica (e.g. Aerosil from Degussa) - probably the cheapest route.
You'll never be able to mill down (a top down process) your SiO2 to < 100 nm. See (registration required):
Metal colloids - their preparation, application and characterization
https://www.malvernpanalytical.com/en/learn/events-and-training/webinars/W160218MetalColloids.html
although the Bredig route may be interesting (slide 34 onward in the above webinar)
Chingakham Chinglenthoiba
P.P. Bandyopadhyay
Alan F Rawle
Thank You for your valuable answers!
Is the flame pyrolysis route applicable for industrial level (industrial scale) nano-silica production? Is this route cheap and environmentally friendly?
1 more question, can the advanced air-jet milling or any other top-down process produce industrial level nano-silica (less than 100nm)?
Gourav Kumar Dewangan
The answers to your 2 questions:
- Is the flame pyrolysis route applicable for industrial level (industrial scale) nano-silica production? Is this route cheap and environmentally friendly?
- Yes, this is the route used for industrial production of fumed silica - one of the 2 nanomaterials (the other is carbon black) made in largest tonnage. The route is cheap, yes, but I don't understand your comment about 'environmentally friendly'. The process ends up with amorphous silica which is as inert as sand and does not pose silicosis issues as does crystalline silica of a certain size range (0.5 - 5 μm approx.)
- 1 more question, can the advanced air-jet milling or any other top-down process produce industrial level nano-silica (less than 100nm).
- The answer to this question is 'No' as there is a comminution limit (Google this term) for all materials. Here they will either plastically deform (and not fracture) or the fracturing and recombination will come to equilibrium as a size (for most materials) in the 0.5 - 1μm level. This sets the limits for dry comminution. See (registration required):
- Dispersion and nanotechnology https://www.malvernpanalytical.com/en/learn/events-and-training/webinars/W190528DispNanoMat In particular slides 40 onward in the above - slide 42 normally comes as a surprise to many...
- In pursuit of perfect packing https://www.malvernpanalytical.com/en/learn/events-and-training/webinars/W151021PerfectPacking.html
- Controlling powder bulk density by optimizing particle size and shape distribution https://www.malvernpanalytical.com/en/learn/events-and-training/webinars/W161006PowderParticleSizeShape
An attached application note may be helpful.
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