Microwave tube Furnace

[peskar]

I have been asked to explore microwave sintering of both ceramics and metals. Some of these meterials will be done in an a different atmospheres. I was reading that one group had taken a standard microwave and punched holes in each end and inserted a ceramic tube. They then sealed around the tube with tinfoil and sealed the ends with metal caps.

To me this does not seem safe since the ceramic tube will be unshielded for a few inches outside the microwave oven. My thought was to encase the tube with a stainless steel tube and stainless end caps. Any thoughts?

Thanks

 

[Higgler]

You can't just put them into a microwave oven?
The RF power from the Microwave oven usually comes from the short side, down low. You can add a commercial waveguide (with care) to this area to concentrate the fields inside a waveguide, then let the waveguide exit inside the oven.

What physical size do you need to heat?
If your parts are less than 2"x4"x8" size, the waveguide will work.

kch

 

[peskar]

No these parts need to be done in some kind of atmosphere other than air. Ie H2, N2, Vacuum....

the parts will be fairly small, on the order of 2"X 2" or so

 

[Higgler]

I'd picture a microwave oven, door removed, safety locks cheated. Swept right angle waveguide piece attached to the power source (need to drill some holes, add a plate with tapped holes inside the oven), then a separate piece of waveguide (length? 12", 24") with at least one pressure window between the right angle and the straight section. Plus a metal shorted cap at the end with pressure gasket.

If your parts don't have much loss, you'd need to protect the magnetron in the oven by loading the waveguide with some lossy material that can handle the high power.

I checked hardware from Continental Microwave for hardware.

http://www.contmicro.com/pdf/produc...nts/CMT-Waveguide-Handbook-Part-1.pdf#page=26

They make pressure window's down to your frequency range (30 psi rated), but don't make pressure injection hardware below 3.95 Ghz, although I'm sure other companies do. How much pressure is needed?

How much rf power do you have to hit your parts with? Full 1 kw? Oven's do have duty cycle controls. Are your pieces very lossy? I'm curious how serious the project is, i.e. just a try to make something for less than $1k and one month effort, or a serious effort making many of these systems for some high volume manufacturing?

kch