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Am looking for a substance to seel two pieces of ceramic that will have molten plastics flowing between at 300+ °C however silver solder circuit traces inside the device prevent me from going much above 600 °C without destroying them – otherwise I would be using some form of pottery glaze but the lowest melting one I have found reference to is around 1000 °C.

The ideal would be something I could bring back up to the glass point and separate the pieces for servicing.

Can any one either suggest a compound or recommend a resource that would allow me to search based on constraints like I outlined?

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  • $\begingroup$ That´s very tricky. One trick could be high-temp 2K epoxy glue. They are usually filled with iron powder, but maybe you can fill a regular 2K epoxy with something ceramic. I´ve used "JB Weld", it survives 250°C for a while. At 500°C it will surely die after a while, so you should be able to take it apart. $\endgroup$
    – Karl
    Apr 24, 2020 at 19:35
  • $\begingroup$ There are a lot of special (and somewhat expensive) cement mixtures on the market, which come with low shrinkage and defined thermal expansion ratios. Those are a one-way street of course. $\endgroup$
    – Karl
    Apr 24, 2020 at 19:38
  • $\begingroup$ Had thought about JB Weld also but that 250°C is a definite deal breaker since the device will be operating for hours on end. Am now thinking of going with sodium silicate (water glass) as an adhesive. Instead of raising the temperature to melt the seal (1000+C) it will be dissolved using an ultrasonic cleaner with plain water. $\endgroup$
    – norlesh
    Apr 25, 2020 at 3:44
  • $\begingroup$ Water glass I have also tried at the time, it´s not bad except that it has a high shrinkage. Don´t try to fill space with it, only use like a real glue, as thin as possible between a flat contact. I wouldn´t bet on getting it off via ultrasonication after it was as 300°C for a while. $\endgroup$
    – Karl
    Apr 25, 2020 at 8:19
  • $\begingroup$ But I´m curious: What are you building there? $\endgroup$
    – Karl
    Apr 25, 2020 at 8:20

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