Dear Colleagues!
While conducting home experiments on the electrolytic deposition of copper in a micro-gap (2-3 mm), under a microscope (x40) I observed interesting effects of short-circuiting by metal dendrites of the anode and cathode - similarly, which leads to fires in lithium-ion batteries where Li dendrites deposited.
Electrolyte: CH3COOH (9%), can be with CuSO4 (~0.1M) or without copper salt. If a copper anode is used, copper dendrites will grow due to copper dissolution at the anode and reduction at the cathode.
(You can see video of quiet copper dendrites growth from this link:
https://disk.yandex.ru/i/wRkEf1wb_iT9HQ
)
1. At low current (1-10 mA) - after the formation of a short circuit, a strong uniform noise is observed in the loudspeaker of an audio amplifier connected in parallel to the electrochemical cell. In the visual absence of any processes, even the release of gases microbubbles. Could quantum effects be involved if electrodeposition results to a nanometer-sized gaps?
It is interesting that a ohmmeter does not show a decrease in resistance to zero; it is 100-200 Ohms and also fluctuates continuously. The contact is unstable, and perhaps something interesting is happening also inside the dendrites along the boundaries of the crystals?
2. With a strong current, for example, when short-circuited cell connected to a DC voltage source of 200 Volts capable of delivering tens of watts, very nice electric arcs appear that quickly run along the surface of the dendritic/electrodeposited metal under water. It seems that there is a competition between the destruction of dendrites by the arc discharge (in this case, the appearance of a red-yellow or black powder, i.e. Cu2O/CuOH/CuO or may be even copper nanoparticles) is observed - and dendrities immediate formation again by fast electrolysis under this voltage.
You can see nice electric arcs video here:
a) https://disk.yandex.ru/i/iDztUygr18uNlQ
and more brutal arc discharges video in more dense electrodeposited copper mass (dendrities was tightly compressed during the formation, using a high concentration of CuSO4 instead of simple electromigration from Cu anode):
b) https://disk.yandex.ru/i/QMWkTnYzbnsFvQ
(since 35 sec of video)
c) And yet very nice "electrodeposited copper electric arcs":
https://disk.yandex.ru/i/HxXhuoPipyeG7A
All were recorded under microscope :)
Are there any patterns that govern electric arcs in a mass of dendritic or spongy metal, or is this a purely random process?
What should be the starting point for computer simulation of such processes?
What practical application could there be, for example, to the topic of short circuits in lithium-ion batteries by similar dendrites?
PS. The noise oscillograms video from 1. point) [low-current, no sparks, no gas evolution, visually full dendrite short-circuit of my electrochemical cell]
https://disk.yandex.ru/i/wQps4Jer0TRdTg
Topping up: look for gloss-creating additives in electroplating baths. I got into the gloss many years ago.
Alpha Phenol was added to the baths (they will be more effective today). This guaranteed a flat surface without protrusions - shiny. This could be a way to stop the dendrites. I wish you success in your research.
Thanks for the idea on how to get rid of dendrites. But for now, this was a home-based fun experiment precisely with the purpose of observing dendrites growth, their behavior under different conditions, and their interaction with hydrogen bubbles. (For example, when a nearby bubble collapses, the structure of the dendrite is greatly disrupted, and in a microscope it looks interesting; and the tip of a growing dendrite moves small objects such as insoluble particles, and it looks very cool, a “microactuator” that can be turned on by applying current, move something by microns and turn it off, then turn it on again - although only one way).
And quite unexpectedly, a strong chaotic noise was discovered (up to 1 volt at a current of 1-3 mA) in a cell short-circuited by dendrites, which intrigued me most of all. At this low current, there are visually no hydrogen bubbles or any transformations in the dendrites themselves - something possibly happens only in the nano-region of the dendrite-anode contact. For example, cyclic formation and destruction of nanocontacts. The Fourier transform of this noise gives a typical set of frequencies from 5 Hz to 1-5 KHz, in the high frequency region the intensity drops sharply (probably this is 1/f noise).
I suspect that there can be formed something like quantum point contacts (https://en.wikipedia.org/wiki/Quantum_point_contact).
Will do))
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