Adhesive or any other method for joining Copper to Ceramic

Copper rivets?

So many materials so little time.

What is the application? Is it vertical? Is there constant pressure ? What is the pressure level on the joint? What is the lenght limitation on the connection?

Can you create a compression seal on the ceramic? Is it exposed or buried after completion?

dadw5boys,

Copper tube interspaced with ceramic tube (to isolate electrically) with a copper bush overlapped on the outer diameters, one part TIG welded to Cu pipe but the other which goes on ceramic has to provide a joint which will see a vaccum of 10^-4 bar and a pressure of 10⁸ bar and temperatures already mentioned. Lenght of overlap on each side is 9mm. Compression seal on ceramic not feasible as it may break it. Joint is exposed to atmosphere.

D'UH ...........Why didn't you say TUBE at trick one???

Gimme a break....

Rivets NBG then!

pressure of 10⁸ bar

....exceeds the yield stress of both copper and ceramic!

According to my very rough calculation, that's about 14,500 million Psi!

WHAT!

I've never heard of a pressure vessel built to take that sort of pressure, so either there's a case of fat finger syndrome here, or some things afoot! What gives?

This is obviously a fitting for use in a black hole!

or some things afoot!

Can we do all the Holmes/Watson gags....can we can we can we?

'Look Holmes...an impression of a shoe!''

This is no time for your impressions Watson!'

Sorry!!!!! It is 8 bar folks!!!!!!

Those flanges are good you mentioned but I happen to find some flanges here that seemed to be better quality because they are US created. Many manufacturers import their flanges and wear down quicker. Something I learned from experience.

This might be a little off the wall as I don't truly understand the joint design, however, if the ceramic is porous enough, you could consider plasma spraying the ceramic joint area with copper then silver brazing the tubing to it. Just a thought.

One method is to metalize the ceramic using one of a number of processes. Then you can join to copper using solder, silver solder, or any of a number of available materials.

You are right on the button, we have sprayed glass with copper and put two sheets of glass togerther by soldering the copper sprayed material for windows. This is a very simple process, you can either roughen the ceramic for the spray to grip or pre heat to about 200 F and then spray and use ordinary tin base solder material for joining the two

How can spray cooper?

Where to find a machine for this process.

I personally would finely abrade both surfaces, clean intimately and use a top grade fluid epoxy......

Then pressure test after fully curing! BUT STAND WELL BACK!!!!

Can the ceramic be made with an anular groove? The copper could be formed down into the groove to provide a mechanical join.

I personally favour glue made from fish skins...but only 'cos I'm a cat and love fish skin.. mmmmmmmmmmm

Silver Brazing is your only way.

And not epoxy adhesive?

Hi to all,

this joining is done by the companies that fabricate vacuum feedtrough parts:

alumina ceramic metallised by Mo-Mn burnt in under protective gas.

Mo-Mn - metallisation is solderable or brazable to any othe metallic material.

Expansion mismatch has to be calculated and elastic or plastic deformation allowed.

The other possibility is brazing with active brazing material (like silver-copper-?- and some titanium added for reactivity.

This requires a good vacuum or a very pure argon atmosphere.

We use this for brazing of diamonds to carbide tools and ruby or sapphire to carbide or other material, also siliconnitride all these also to ordinary steels and stainless.

RHABE

I think that you will find that the Mo/Mn metallising is used because it wets to the ceramic well but it does not braze or solder readily. The Mo/Mn is usually nickel plated & it is the nickel that wets to the metal part during brazing/ soldering.

Just a quick question my curiosity being what it is.

Which has the greater expansion rate Copper or Ceramic.

Reason being for the Q is which would go on the outside the one that expands slower or the faster one.

Which leads me to Q#3( I know i said a quick One)

If the copper expands faster and its supposed to be put inside the ceramic then how long could it possibly last before cracking the ceramic and failing of the converse of that separating from the outer and breaking the seal?

Ok I'm done

In a nutshell, the copper will expand at a greater rate for a given temperature rise than the ceramic material. Therefore the copper should go on the outside. If the ceramic is metalized using a high temperature process such as plasma spraying, the spray coating should shrink on cooling. Now the sprayed on copper is like a very tight band on a ceramic core. This should solve, to a great degree, the possible problem of the copper loosening its grip on the ceramic at elevated operating temperatures. It's just a calculated guess at this point and needs to be tested. It seems to me, to be the obvious choice at this point. At 200C (392F) heat cycling an epoxy may cause early failure of this joint. But 200C is not enough heat to repeatedly anneal the copper and cause loosening. It would certainly help the situation if the ceramic surface were roughened to provide a better mechanical grip for the metalizing process. In applying this copper spray and the subsequent brazing of the copper tube over it, I would not be in favor of furnace brazing as I would want to keep the ceramic core cooler than the copper in order to get a tighter joint.

We build ceramic/copper brazed assemblies every day & the finished assembly has to be able to hold a vacuum of 10-9 torr. Obviously this is easier than trying to contain pressure because the material is being held in compression. We have to calculate the amount of relative expansion of the copper & ceramic components at the brazing temperature (~810°C) and size the components to suit thus the copper parts start out slightly smaller than the ceramics. The ceramic, being stronger in compression tends to dominate once the assembly is cooled leaving the copper part in tension.

Bear in mind that the joint condition at the brazing temperature must be considered. If you have a concentric joint with the parts fitting at room temperature there could be a large gap at the brazing temperature which must be completely filled with brazing material.

A flat end to end joint is much easier to manage & the result is surprisingly strong.

The ceramic metallising is generally done by screen printing on flat surfaces & by hand painting on curved surfaces and then fired to bond the Mo/Mn layer to the ceramic. The metallising is then nickel plated to provide the brazing surface.

Do the metal parts have to be copper? There are specific nickel alloy steels with trade names such as Kovar and Telcoseal that have been designed to match the expansion rate of alumina ceramic and which have good brazing properties.