lowest sintering temperature electrical ceramic

[coppercone2]

I tried to research this a little but mostly stuff about high pressure sintering comes up.


Are there any low temp powders that can be sintered like Alumina but at a temp of <900 degrees C?


Say you wanted to build your own slightly lower durability or whatever ceramic hardware out of a engineering quality material. Is it possible?

[twospoons]

try a glass frit. Some will sinter as low as 500C

[coppercone2]

is that gonna make anything close to like a alumina part?

Say for like HV standoff or something. I imagine you have to glaze it with something too, so it does not absorb crap



I know you can use machinable ceramic but it would be cool if you can make... prototypes... with glass. That would be way fucking cleaner then machining ceramic lol


can you cut alumina with glass to activate it at a lower temp to get some franken material? Maybe if the two have slightly different grits you can get some kind of reliable structure going like cement with gravel?


or some other weird stuff like DIY low temp cermet?


I know you can fuse silver with a bit of glass. Good stuff requires some platinum or palladium or something to be added. What happens if you mix glass and carbon powder?

[twospoons]

What's the application? That would help a lot with suggesting suitable materials. Do you need a vitrified body or is some porosity OK?
As for mixing alumina with other stuff - thats precisely how glazes are formulated. Usually some mix of alumina and silica, with a flux based on sodium or potassium oxides and other components in order to achieve the desired properties such as fusing and melting temperatures, viscosity, thermal expansion coefficient, etc.

Another option would be earthenware clays, which can be fired as low as 900C.

[coppercone2]

not sure, just like hardware. Bracket, standoff, bushing

[Doctorandus_P]

The magic word is "LTCC" (Low-temperature Cofired Ceramics)

https://en.wikipedia.org/wiki/Co-fired_ceramic

I've seen some references for temperatures as "low" as 850c, but with that magic word you can find it for yourself.

[coppercone2]

I think I can make a sintering mold by burning out 3d printed material in a open mold.

Do you know if pressure is required? I have glass powder I can get out of glaze I bought (that I extract glass powder from to mix with silver powder to make PCB stencil silver ceramic material). I could extract alot more and pour it into a mold and try to sinter that. But if I need to press this mold I am expecting serious manufacturing trouble for anything but the most simple structure

[LaserSteve]

 Cotronics makes castable ceramics. Start there.

It took a year of University level R&D to make a low firing frit that did not use dangerous amounts of  nanopowder lead oxide. [ The stuff floats in air currents.]

Boron based three part glasses melt at 890'c in theory. In reality they are very, very, very, brittle. When you add even one percent of another oxide to make them useful the melt point goes through the roof.  Yes, you can make a three part glass with. hardware store and drug store materials. Is it workable, no. Does it pour well, no. Does it stick to the crucible ; oh yes.

  Making one that did not use Antimoney and Arsinic compounds that vaporize to encourage melting is difficult.  I ain't talking.

Solderable low temp inks are proprietary. The artistic firable gold, silver; and copper inks for kiln firing contain bismuth as a catalyst  and will dissolve before they solder.


Good adhesion of conductive inks in "cheap" processes usually requires a layer of nickle under the metalization for adhesion.


Home made "dental cements" that are water based are a thing of the past. Work great until you need to fuse them.

By the time the R&D was done, my supervisor agreed to have a second US Citizen Permanent Staff member added to the team so we could order sample quantities of LTCC materials, which are  highly restricted in the US due to treaty.  The two US Citizens would have had to keep the material in a safe and log what they dole out to the non-citizen students and professors.






 

[coppercone2]

yeah i dont want heavy metal powders in my shop

it sounds alot easier to throw stuff out and make room for a high temperature oven instead of trying to make the low temp one work if I really wanted ceramic parts, then i can do good old porcelain, which is well documented

[twospoons]

Yep, if you are going to have a kiln / furnace in your workshop, might as well make it a capable one. If you are planning on firing any type of clay (including porcelain) you will need a good programmable
 ramp/soak controller. The firing schedule for clays needs controlled ramp rates, and several soak stages. This allows water and organics to be burned out at various points along the profile. A decent mini kiln is on my wish list.

The only time I've put cold clay bodies into an 1100C kiln was at a Raku firing day held by the pottery group I was part of. The resulting fired object tends to be weak and porous, and the initial green body is made with a lot of prefired clay (grog) to help withstand the thermal shock. Fun times.

[coppercone2]

there is difference between the kilns. The nichrome one can stand up to more abuse, the high temperature one has aluminum, so it can react with stuff and its fragile.

I don't think there is a one size fits all solution here, theoretically speaking.. but both are very sensitive to over heating

for structural stuff, it seems that higher temperature is the most important factor.

[coppercone2]

I made up the 97% silver 3% glass mixture and finished working on the muffle furnace. It still needs a better thermocouple but maybe I can try to make a ceramic silver trace soon on a ceramic razor blade

I am hoping that diamond laps will solve the smear problem applied science man was having with his sintered silver PCB . The only problem is I don't have any silk screen or any stencils. Hopefully I can make brass sheet stencils by etching to make a RF PCB

[coppercone2]

Hmm I gave it a shot. It got to 740C for maybe 10 minutes and turned white, but the adhesion to the ceramic razor blade was poor. However, gentle scraping did reveal a really nice looking silver material that soldered really well.

I think I might try more heat next time. The results were better then the silicon dioxide attempts, that had worse adhesion then the glass.

Not sure if its temperature, time or substrate that might be a problem.

[coppercone2]

and does anyone on the off chance know what palladium + silver does vs just silver for inks?

I found some crap about oxide states or something but practically I have no idea. Does it increase success?

[coppercone2]

it works. I took it up to 850C this time.

It works good, the trace is damn solid. I soldered a 20 gauge wire to it and its pretty strong. The trick is gonna be to lay the paste, I got a few holes, but I did a mega half assed job on that with some tape. I think if you mix up a few grams of this mixture instead of trying to deal with 1/4 gram it might actually work nice.


Still would like to know what palladium additions do to this mixture, but I am impressed.