09-10-03 14:00
No 458157
Patent EP1238715
The above patent goes into exotic details of enhancing the effectiveness of sonochemistry, but it doesn't have to be so complicated.
A 555 timer IC chip could produce the 20 or 20+KHz signal (see Forrest Mims' mini-books at Radio Shack, "555 Timer Circuits", etc.), then a suitable amplifier (plans and datasheets everywhere, op amps, jfet, mosfet) could provide the power levels. Transucers are available everywhere also.
As with other chemical equipment, the price of ready made is sky high and inflated to the nth degree.
I mean, yes, it has space-age contours and specially-formed stainless steel, however a transducer attached to the outside of a flask could easily suffice, and in fact I have seen pics of that very type of setup.
It's too bad there isn't more on espacenet and pubmed.
I frequently find, as time has progressed (see literature and patents), chemists have adopted more complicated, expensive and dangerous methods to "keep up with the Joneses", much as in other branches of science, abandoning simple cheap methods. Sonochemistry must work too well and be too simple. As I heard in a good movie recently, some people "are just too hip to be happy".
I may try it sometime in some months, as one of the precursors I'm interested is a bit pricey for my taste, but tricky to make, my way, due to steric hindrance and the general inactivity of the moiety. I've read sonochemistry can increase some chemical reaction rates a million fold, and shorten reaction times spectacularly.
I was also thinking, on the subject of ready-made vs homemade equipment, that a reaction kettle is perfect (but, sticker shock awaits those who look for them) for most things, easier to clean out than a flask, more balanced to help prevent embarrassing and dangerous breakage accidents, plenty of room for a large stirrer, multiple inlets, flat-bottomed to obviate the need for a mantle, etc. I thought of making a lid/stopper for a beaker out of rubber or a chem- and heat-resistant plastic.
(Hive Bee)
09-10-03 23:23
No 458232
I have been pondering on that subject too for some time. What would be nice is to use a small piezo transducer, coat with a layer of Teflon, to make an ultrasonic probe that could be immersed in the rxn mixture.
I've read an interesting paper somewhere about precipitating metals in ultrasonic environment, it give a very finely divided and much more reactive metal powder. Ideal for eg. making ppt. Ni/kieselguhr catalyst.
I'll try to find the paper again.
A Dream Within A Dream (http://www.poedecoder.com/Qrisse/works/
(Stranger)
09-11-03 12:41
No 458389
Anyone who has a computer and/or a CD player has a third of the equipment neccesary (signal generator).
There is a software called GoldWave which will allow one to make any waveforms and any frequency up to a certain point.
I think it goes up to 20,000 (20KHz).
Sine waves or square waves (also makeable with GWave) are probably efficacious. There are many other waveform editing softwares, but to me, GWave is king. 4000 free commands, then $40 to register. I use it to make and edit signals for mind-altering electronic devices.
Modulation with white noise might help. Nature is comprised of noisy, nonlinear systems. Chemistry is no exception.
These signals can be recorded on CD at a 44.1KHz sampling rate. Just plug the CD player into an amp with an upper freq limit of +20KHz and sufficient power, plug in a shielded transducer, and voila!
I have read that scratching the side of a glass vessel with a glass rod will cause the beginning of crystallization in a solution of a compound contained in the vessel. Perhaps this sound would help with other reactions.
It is also said that burst-firing lasers (a burst of pulses, then a moment of no pulses, repeat cycle) is more effective in cutting materials than an unchanging laser beam. It wouldn't surprise me if this held true with sonochemistry also.
(Hive Adickt)
09-11-03 13:51
No 458403
You will need much more pover than a usual speaker will generate. Red this one Post 247296 (hest: "Re: initiating Grignards with ultrasonic ...", Chemistry Discourse)
(Newbee)
09-11-03 22:30
No 458458
Yes, 150 watts is a lot, and, with piezo transducers, one has to be careful, exposure to high levels of ultrasound can harm or kill animals and people. Cell disruption and ultrasonic welding are, I suppose, somewhat different than sonochemistry. The Thomas Register contains a list of manufacturers/sellers.
I will look further into it.
(Hive Bee)
09-12-03 01:46
No 458498
The power supply transforms conventional 50/60 Hz electrical power into high-frequency electrical power at 20,000 Hz.
Power supplies are typically rated in watts of output power. It should be noted that using a power supply with a higher wattage rating does not mean that more power will automatically be transmitted to the liquid. Rather, it is the resistance to the movement of the probe (horn) that determines how much power will be delivered into the liquid. Load is determined by three factors: sample volumes, sample viscosity, probe size; and, in some cases, a pressurized environment. Under identical loading conditions, the wattage delivered by two power supplies with different power ratings will be the same (provided both have sufficient power capability).
The speed control on an automobile, can, to a certain extent, be compared to an Ultrasonic Processor. The speed control is designed to maintain the vehicle rate of travel constant. As the terrain changes, so do the power requirements. The speed control senses these requirements, and automatically adjusts the amount of power delivered by the engine, in order to compensate for these ever-changing conditions. The steeper the incline, the greater the resistance to the movement of the vehicle, and the greater the amount of power that will be delivered by the engine, to overcome that resistance.
The amplitude control allows the Ultrasonic vibrations at the probe tip to be set to any desired level. Although the degree of cavitation required to process the sample could readily be determined by visual observation, the amount of power required cannot be predetermined. Asensing network continuously monitors the output requirements, and automatically adjusts the power to maintain the amplitude at the preselected level.
Negligible power is required to keep an Ultrasonic probe resonating when operated in air. The greater the resistance to the movement of the probe due to higher viscosity, deeper immersion of the probe into the sample, larger probe diameter, or higher pressure, the greater the amount of power that will be delivered to the probe. Setting the amplitude control fully clockwise will not cause the maximum power to be delivered to the sample. The maximum power any Ultrasonic Processor is capable of delivering is only delivered when resistance to the movement of the probe is high enough to draw maximum wattage.
This phenomenon can be demonstrated as follows:
Depress a probe down against a piece of wood while observing the power monitor; as the down pressure (resistance) is increased, the amount of power delivered by the power supply will increase accordingly.
taken from:
What are ULTRASONICS and ULTRASONIC PROCESSING?
http://www.sonicsandmaterials.com/Access
A Dream Within A Dream (http://www.poedecoder.com/Qrisse/works/
(Stranger)
10-13-03 12:55
No 464386
Scratching inside a glass vessel to promote crystallization has nothing to do with the sound produced. It is believed that the scratching generates tiny particles of glass that act as nucleation centres for crystals to form.
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