Hello everyone
I would design a heated substrate holder using a tungsten filaments (as resistance), and a Duralumin piece (usinated). So my first question concerns the Duralumin: what temperature should not be reached to avoid deformation of the designed substrate substrate?
In fact, I use plaster to encapsulate the tungsten filament and avoid short-circuiting with Duralumin, but I was told the plaster emits gas in continue, which is not advisable for use in a vacuum chamber. Can you give me a special resin brand to replace the plaster and avoid degassing.
Here's attached a file of the described device.
Thank you
Why do you need the plaster to encapsulate the filaments? Just suspend the filaments robustly below the plate with short, mechanically stable ceramic posts. In a vacuum, the primary mode of heat transfer from the suspended filaments to the plate will be radiation. This can often be sufficient.
As for setting the Duralumin temperature range ... Have you reviewed specifications on the material itself. Why not consider copper as a better choice for the base substrate because it has a higher thermal conductivity?
Hi Pr. As you have seen the device in the pctures, i really need it to be like that encapsulated. The problem is with a material (ceramic) of substitution for plaster. I need the information about a mark, or homemade, or recuperation materials i can use. For the use of duralumin, this is not a choice, but a necessity because that's all what we have. Industrially me substrate holders are about 5000 euros. Thank you.
I can appreciate that you are spending your time to make your own heater as a way to try to save money. I suggest therefore to spend your time differently at this point. Do a search on line for "sample heaters for vacuum systems". Review the various designs that are posted from various companies. When you can afford to buy one that meets your needs, do so. When you need to design your own heater from stuff you have sitting around in various labs, take hints from the designs that are shown at the companies. Try to find parts that are comparable.
As a start, here is a link to a company that produces heaters.
http://mhi-inc.com
Immediately that I see their designs, I might for example go around to find an old electric stove, take out the heating element from it, and try to fit it in to my heater. I would also learn that radiative heating is the primary way that heat is transported from the heating element to the plate when the heater is in a vacuum. So, I would not worry about having the heating element in some type of physical contact with the plate that is to be heated.
My final thoughts on your current design are that it is overly massive, especially the top plate, and that it uses unnecessary parts or materials, for example the plaster insulation.
I see in your photo that there are some ceramic beads covering the wires that are not covered by plaster. What about ceramic tubes? I have seen (and used) heaters that used very thin ceramic rods to electrically insulate the heating wire, yet they provided very good heating. Maybe a combination of ceramic tubes, cut to different lengths to accommodate your sample holder, and including ceramic beads to cover the wire in between bends?
Here is an example: http://www.ortechceramics.com/product-category/ceramic-tubes-rods. I am not recommending that or any particular company as a source. Such ceramics are sold in many different places across the world; I don't know who your closest source would be, but I am sure there is a source much closer to you than that one in California.
http://www.ortechceramics.com/product-category/ceramic-tubes-rods/
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