FAQs
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by Thermcraft
Why use a transparent furnace?
Developed originally for observing crystal growth, transparent furnaces are now used by those who want to take advantage of their unique properties.
| Visibility | Unobstructed viewing of samples, thermocouple placement and process procedures. |
| Low mass | Heats up quickly, and possesses a compact design. |
| Cleanliness | No contamination from fiber insulating material. |
| Uniformity | At least +/- 2°C over 60% of the length of the heated chamber. |
How are these furnaces used?
Originally developed for growing crystals, transparent furnaces are used for Liquid Phase Epitaxy (LPE), Chemical Vapor Deposition (CVD), and ampule growth. They are also used for annealing of wafers, gold wires and superconducting wires. The TransTemp tube furnace can be used for almost any application where a convention tube furnace would be used.
What about the gold mirror as insulation? How thick is the gold film?
The average thickness of the gold film is approximately 80 nm. Viewed on a molecular level, the gold mirror would look like a series of gold islands with open spaces between islands. The heavier the film, the less space between the gold islands. The visibility into the furnace is affected by the thickness of the coating. Lighter coatings allow for better visibility into the furnace, while heavier coatings produce a more efficient but opaque furnace.
What is the external temperature of the furnace during operation?
| Internal temperature | External temperature |
| 300°C | 54°C |
| 419°C | 119°C |
| 630°C | 173°C |
| 814°C | 215°C |
| 1000°C | 287°C |
What is the maximum operating temperature of the TransTemp transparent tube furnace?
The recommended maximum operating temperature is 1000°C. The TransTemp will operate at higher temperatures, but the lifespan of the gold film will be greatly reduced.
The melting point of gold is 1064°C, how can the gold mirror survive?
The innermost surface of the gold film may reach the operating temperature, but most of the energy is reflected, not transferred into the film. The relatively cool air surrounding the outside of the gold tube cools the glass, which keeps the gold film below its melting point. Always keep the outside of the furnace unobstructed so that natural cooling effect can take place or the gold mirror will crack!
Can you operate the entire furnace in a vacuum?
Yes... but the outside temperature of the gold mirror must stay below 600°C.
Can the furnace be operated as a vacuum furnace?
Many of our TransTemp owners insert a quartz tube through the furnace. Process tube end seals can be used on the tube and a vacuum or positive pressure can be created inside the tube. Please ensure that the process tube is designed for the intended operation.
What is the largest furnace and the smallest furnace and mirror you have made?
| Furnaces: | ||
| Longest | IBM Tokyo, Japan | 57mm OD x 7926mm |
| Largest Diameter | Aichi Steel, Japan | 200mm OD x 500mm |
| Smallest | NASA, Cleveland | 23mm OD x 50mm |
| Mirrors: | Longest single section | 1500mm |
| Largest Diameter | 300mm OD | |
| Smallest Diameter | 25mm OD | |
| All furnaces are of the same design. Only the dimensions change. | ||
What kind of a control and power supply do you recommend?
We recommend a controller that produces a 4-20 ma signal to a phase angle power supply. This combination produces the most accurate temperature profile in our transparent furnaces. A phase angle controller supplying power to the element yields the longest life and the least variation in temperature.
Who are some of your current and past customers?
Partial list of our U.S. customers:
- Minnesota Mining and Manufacturing
- Naval Electronics Laboratory Center, South Dakota
- Naval Research Center, Washington
- Bell Telephone
- North American Rockwell
- Esso Research
- Eastman Kodak
- United States Bureau of Standards
- U.S. Air Force, Hanscom Field
- U.S.A.F. - Wright Patterson Air Force Base
- EG & G, Inc.
- Gillette
- Grumman
- Rockwell International
- Marshall Space Flight Center
- Landseas Corporation
- Philip Morris
- Hewlett Packard
- Xerox
- University of California - Berkeley
- University of California - Los Angeles
- Carnegie-Mellon University
- University of Utah
- University of Southern California at Los Angeles
- Purdue University
- Massachusetts Institute of Technology
- Polytechnic Institute at Brooklyn
- University of Washington
- Colorado State University
- Harvard University
- University of Wisconsin
Partial list of our International customers:
- Australia
University of S. Wales
University of Wollongong - Canada
Bell Northern
University of Toronto - England
Feranti, Ltd.
University of Reading - France
French Atomic Energy Commission (C.E.A.)
Universite de Strasbourg - Germany
Preussag Aktiengesellschaft
Berliner Handels-Kontor Heinz Lindenberg - India
Indian Institute - Madras - Iran
Arya-Mehr University of Technology - Israel
Semi Conductor Devices
Rotem Industries
Isreal Atomic Energy - Japan
Dinichi Trading Company
Ishikawa Trading Company - Netherlands
Kawecki-Billiton - New Zealand
Department of Science and Industrial Research - Norway
Elkem Carbon
Teck Industries
Trondheim Industries
Norsk Hydro - Switzerland
Interac
Scole Polytechnique Federal de Lausanne - Venezuela
Instituto Venezolano de Investigaciones Cientificas
 | « Click for the TransTemp Brochure Feel free to contact us with any questions regarding Thermcraft products. (336) 784-4800 |
© 2012 Thermcraft, Inc.