mini furnace for oxide-fiber tension test

How long a furnace, 1 cm, 10 cm or 100 cm?
This is perhaps important in the design.
Do you have any needs for rapid heating or cooling? This too is important to the design. Really rapid heating requirements would tend to influence the thermal mass of the furnace.
So, unbutton that lip and talk some more about this mysterious furnace.
At this stage, if you were a prospective consulting customer, I might otherwise determine that someone else would be far better suited to your needs than myself.
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I am assigned to design a very small furnace (5 - 6 cm, diameter
doesn't matter, temperature 1000 Celcius). I am looking for suitable
heating methods. Please share if you have any idea.
ps. somebody told me to try 'halogen lamp heater' but there is not
much information about it in the internet. So idea about this 'halogen
lamp heater' will help me much too.
Thanks in advance
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You did not specify whether you wanted a box or tube type furance which significant changes your design parameter. However, you should be able to buy commercial nichrome or kanthal embedded heating elements for this purpose or just buy the wire and make your own (Zircar would be a good place to start). You can even buy ceramic potting compound to embed the elements. One method I have used for making my own small custom furnaces is gas furnace hot surface ignitors made out of silicon carbide, available at most appliance shops for $20 or so. They are quite cheap and the width of the units ranges from 1 - 2 cm or more. They can even be run off a variac if you want quick and dirty heating then you can just monitor temp with an external thermocouple. I have reached temps of 1400C with these units. Quartz or halogen lamps can be effective but the geometry of the sample can cause issues and you either need reflectors to direct the heat or some sort of susceptor since most oxide are not effective in this area. Silicon carbide should work as a susceptor for your application.
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You have a difficult problem in getting meaningful results.
There will be gigantic thermal gradients along the length of the fiber from the grips to the middle of the hot zone and then down to the grips again.
Maybe you can attribute the maximum temperature of this with the fracture event or approximately so.... So you have in effect some temperature uncertainty because of the large gradient.
If anyone asks you the gauge length of the test specimen you have a problem......
IF you are asked to try to make some claims as to the fracture strain, you have a problem.
I would begin to devise a tiny furnace, tiny in ID so that the aspect ratio of the hot zone is as large as possible so as to try to get a reasonable uniform hot zone.
I might heat it directly with current flow. In this case, the heating element could be disposable and there would be standard heating elements fabricated (or bought) for these single use short term thermal heatings. So, in effect, you would be assembling a disposable furnace during the mounting of the specimen using water cooled grips, perhaps, or grips that can take quite a few heating cycles before needing replacement.
Now, I stop.
It is your project and part of the project and your education is to wrestle with these things to work them out.
There are, of course, many more clever things that other high temperature researchers have developed, used and evaluated.
So.....LIBRARY time.
A day is the library is often worth a week playing around in the lab.
An evening sucking ideas out of newsgroups can be even better than a day in the library...... unless the suckee avoids getting too involved.
hua wrote:
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Well the furnace is for high temperature tension test of less than 8 cm long oxide fibres. So far I am expecting to design a furnace which is less than 5 cm long because I am expecting only to heat the sample (not the whole or parts of the testing apparatus) up to 1000 C. Rapid heating or cooling is not that necessary in this experiment.
(Waiting for help)
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