Sodium Silicate dielectric? Vacuum Feedthrough

In summary: Cant seem to find a kv/mm for waterglass/sodium silicateIn summary, waterglass/sodium silicate is being considered as an electrical insulator for vacuum feedthroughs due to its expanding properties when heat cured, low outgassing, and adhesive properties. It has similar dielectric strength and resistivity as plate glass and is suitable for UHV feedthroughs. It can also be used for knife edge flanges and sight glasses with added lead powder for radiation shielding. Curing temperature and time are recommended to be slowly heated to 200 F for 40 minutes. It is suggested to use a knife edge on the other side of the copper for a UHV seal and teflon as an insulator. It
  • #1
Cant seem to find a kv/mm for waterglass/sodium silicate. I was thinking of using it as an electrical insulator for vacuum feedthroughs, expecting an easy seal as I hear it expands when heat cured, therefore pushing against the chamber wall and the wires to prevent leaks and also seal by its adhesive properties. I think of using spark plugs but 50kv is too much for them.
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  • #2
After some in depth research I found through search of a sodium silicate based product (stixso rr from pqcorp) that it has about the same dielectric strength and specific resistivity in ohm centimeters as plate glass, a brochure stated.

the reason this is important for feedthroughs is that stixso rr, which is basically entirely sodium silicate and water, after full dehydrated curing, is incredibly low outgassing, as NASA's outgassing database states. It is suitable for UHV feedthroughs where other adhesives, sealants, and epoxies are not. It expands as it cures so even if it is not truly adhesive to the chamber and the feedthrough, it will be pressing against them by its expansion, when I think of this it reminds me of how knife edge flanges seal just from pressing and biting into the gasket material.

i wonder if knife edge flanges that are damaged could be used as molds for sodium silicate forms, if easily separated the could maybe make a perfect fit into knicks and dents on the knife edge seal, upon separating them one would place aluminum foil in between and put them back together for a possible seal. I've read a patent where aluminum foil (i think household foil rather than special purpose) was proven as a low cost gasket material.

i would also think sodium silicate water glass could be used for sight glasses, especially smaller kinds just big enough for laser entry, or larger ones that could have had lead powder added safely to their mix before they were cured, for the purpose of radiation shielding.

curing temp and time can be found not too difficultly but IIRC they say heat them slowly up to 200 F and hold that temp, i think about 40 minutes in it should be dehydrated/fully cured
  • #3
To make it like a conflat seal you would need to have the end piece molded to something like a knife edge, regular conflats are more like a triangle edge but still sharp at the tip. I think that shape is there for strength. You would have to have some kind of knife edge on the other side of the copper for a UHV seal though. That could be SS though, wouldn't have to be waterglass since the copper or aluminum is already conducting so it would have to have a fair amount of disc space cut out to keep 50KV from arcing there. I would assume you would use something like teflon as an insulator just before the waterglass starts. Is this for some kind of electric field acceleration ring or something like that? In ion implanters we use that rather low voltage for ion extraction from the source and then 4 to 10 times that for the acceleration rings.
  • #4
Oh no just trying to see if I can add a focused ion beam to the SEM I am about to finish. I realize its best to get alumina ceramic for these and use the waterglass as the inexpensive UHV adhesive and sealant. That's interesting to hear about your ion implanter

Related to Sodium Silicate dielectric? Vacuum Feedthrough

1. What is sodium silicate dielectric?

Sodium silicate dielectric is a type of insulating material used in electrical systems. It is made up of a combination of sodium silicate and a filler material, such as glass fibers or mica. It is commonly used in vacuum feedthroughs to provide electrical insulation in high voltage applications.

2. How does sodium silicate dielectric work?

Sodium silicate dielectric works by creating a barrier between two conductive materials. When applied between two electrical components, it prevents the flow of electricity between them, acting as an insulator. It also has a high dielectric strength, meaning it can withstand high voltage without breaking down.

3. What are the advantages of using sodium silicate dielectric?

One advantage of using sodium silicate dielectric is its high dielectric strength, which allows it to be used in high voltage applications. It is also non-toxic and non-flammable, making it a safe option for use in electrical systems. Additionally, it is relatively inexpensive and easy to apply, making it a cost-effective choice.

4. Are there any limitations to using sodium silicate dielectric?

One limitation of sodium silicate dielectric is that it can be affected by moisture. If exposed to high levels of moisture, it can lose its insulating properties and become conductive. It is also not suitable for use in high-temperature environments, as it can break down at high temperatures.

5. How is sodium silicate dielectric applied in vacuum feedthroughs?

Sodium silicate dielectric is typically applied in vacuum feedthroughs through a process called potting. This involves pouring the liquid sodium silicate mixture into the feedthrough, allowing it to harden and create a solid insulating barrier. It is important to ensure that the feedthrough is completely sealed to prevent any moisture from affecting the dielectric.

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