mysteriusbhoice
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Need some help on how to calculate the surface area of expanded mesh.
I am working on a coating process with a friend for PbO2 on titanium without MMO and so far the tests on the strips are succesful.
These electrodes use a relatively cheap conductive undercoat using my technique which allows to plate any metal directly onto Ti without nickel by
simply adding HF 3% by wt in the plating bath which sounds cursed but it works.
The conundrum now is that some titanium meshes are the diamond expanded mesh type and the PbO2 coating process the 1st layer has a very narrow current
density for plating. Too much and it will produce a porous rough mass which is undesirable. I have found the perfect operating current density on
plate electrodes for all the plating baths and times but I need to know a good way to get a near exact total surface area of an expanded mesh
electrode.
The issues are they come in different sizes and the sellers sometimes dont give any info on the surface area of the mesh. I wonder if theres a formula
to get the true surface area of the metal part of the mesh.
Video of electrode plating process and short test below.
https://youtu.be/5WlzECMoqQk
[Edited on 20-7-2021 by mysteriusbhoice]
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Twospoons
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Might be best to measure a sample.
Starting with flat plate as a reference, and a piece of mesh to test:
weigh them dry, then dunk both into a detergent solution. Remove, shake off the drips and weigh them wet. Assuming the liquid film thickness will
be similar on both pieces then the weight of the liquid film should be proportional to the surface area, so you should be able to get a close estimate
of the mesh area using the flat sheet as a reference. Does that make sense?
Or you could anodise both test pieces and compare capacitance with a liquid electrolyte as the counter electrode. But you'd need the anodising to be
identical.
Helicopter: "helico" -> spiral, "pter" -> with wings
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Johnny Cappone
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Unfortunately I can't provide a reference, but a few years ago, at a pyrotechnics forum in which I participated, calculations were made and it was
concluded that the total area of the "diamond-shaped" titanium meshes was simply... the area total, as if the part were a solid sheet.
The area of the recesses would compensate for the empty spaces. Or maybe I saw it right here on SM and I'm going crazy. So many data, so many
threads, my mind is no longer the same.
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WGTR
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Well, if we assume that the mesh is simply flat sheet that is expanded, I would start by obtaining an accurate thickness measurement and weight of a
given sample. Using these values I would then back-calculate the area of an un-expanded sheet of the same material and thickness. Then I would count
the number of openings in the sample and add the area from the edges for each opening. That should get you close, I think. Beyond that, plan on
running several tests at different current densities to obtain an adjustment factor for your particular type of expanded material.
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mysteriusbhoice
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Quote: Originally posted by Johnny Cappone  | Unfortunately I can't provide a reference, but a few years ago, at a pyrotechnics forum in which I participated, calculations were made and it was
concluded that the total area of the "diamond-shaped" titanium meshes was simply... the area total, as if the part were a solid sheet.
The area of the recesses would compensate for the empty spaces. Or maybe I saw it right here on SM and I'm going crazy. So many data, so many
threads, my mind is no longer the same. |
That is only true for forward expanded mesh but not flat expanded mesh where its then flattened and in that case this is no longer true.
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rockyit98
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using capacitive testing. can get pretty accurate.
"A mind is a terrible thing to lose"-Meisner
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mysteriusbhoice
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I have come up with my own formula since posting this
defining measurements:
1. measure width and length of each diamond hole. (l, w)
2. count how many holes are in each row and how many rows of holes are there ( be aware if its staggered) (nlh, nwh)
3. measure length and width of assumed plate electrode. (L, W)
4. thickness of mesh t,
Calculations:
1. perimeter of each hole p = 2x(l+w)
2. number of holes n = nlh x nwh
3. Surface area of inner sides of hole SAi = pxnxt
4. Surface area of flat plate SAp = 2x(LxW)
5. substractive area of spacing of holes SAs = [2x(lxw)]xn
6. Real surface area SA = SAp - SAs + Sai
The calculator works for FLAT diamond mesh only not forward as that has greater surface area as a flat plate of the same dimensions.
Attachment: Mesh calculator.xlsx (12kB)
This file has been downloaded 386 times
[Edited on 22-7-2021 by mysteriusbhoice]
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Texium
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Thread Moved
29-11-2023 at 20:55 |
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