How to reduce crystal size

[willowchar]

Can anyone suggest a method to reduce crystal size during crystallization.

My understanding is that slowly reducing temperature during the process results in a more pure product but large crystals. Faster temperature reduction results in less pure product but smaller sized crystals. I am aiming to produce crystals around 90 microns. Will continuous stirring during crystallization help?

Thanks in advance.

[Piccaso]

It all depends on what you are making. What are you trying to make crystals of?

[Mumbles]

There are a lot of things that will help. Faster agitation and quicker cool down both tend to make finer crystals. Depending on what you're making, adding an anti-solvent can also tend to crash things out faster and give finer crystals. A lesser known, but effective method is introducing additives to help keep crystals small. Dextrin is actually surprisingly effective at keeping particle sizes down in some instances.

[willowchar]

Thanks for the reply's. Interesting ideas. If one wanted to produce small crystals of AP. what method would work best?

Thanks.

[SeaMonkey]

There is a process known as Ultrasonic Crystallization and Precipitation.

 

Whether it could be accomplished with something like the Harbor Freight Ultrasonic Cleaner

would have to be tested. The possibilities are certainly interesting.

Edited October 29, 2020 by SeaMonkey

[WSM]

Thanks for the reply's. Interesting ideas. If one wanted to produce small crystals of AP. what method would work best?

Thanks.

 

AP is a unique animal.

 

If memory serves, commercially it is "roller milled" with a very small amount of another substance (tricalcium phosphate is mentioned) to keep the crystals of stable and uniform particle size, which is important when working with very large quantities (such as solid rocket boosters using many thousands of kilos of AP). In the past, most AP available to pyrotechnics producers and hobbyists was surplus material from aerospace.

 

The mention of using ultrasonic crystallization and precipitation is intriguing but I don't know enough about it to speculate whether it should or can be done safely with AP (especially on an industrial scale!). It certainly sounds beyond a hobbyist level of involvement.

 

Good luck and be safe.

 

WSM