by
Thermcraft |
FAQs
FAQs
| Sizes | Photos
| Elements
Why use
a transparent furnace?
Developed
originally for viewing crystals, transparent furnaces are now
used by those who want to take advantage of their unique properties.
| Visibility |
Accurate
viewing of melting samples, thermocouple placement and process
procedures. |
| Low
mass |
Heats
up quickly, and possesses a compact design. |
| Clean |
No
contaminating fiber insulating material. |
| Accurate |
At
least +/- 2 over 70% of the length of the furnace in a 60
mm diameter furnace. |
All furnaces
are individually profiled prior to shipment. 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. Assorted specialty furnaces
have been made that capitalize on the low mass and cleanliness
of the design.
What about
the gold mirror as insulation? How thick is the gold film?
From our estimate
of the amount of gold deposited, the average thickness is about
800 angstroms. This thickness, viewed on a molecular level, 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 will allow more radiation to escape
and produce clearer view into the furnace, while heavier coatings
produce a more efficient but opaque furnace.
What is
the temperature of the outside of the gold mirror at various inside
temperatures?
| Inside
temperature |
Gold
mirror outside temperature |
| 300 C |
54 C |
| 419 C |
119 C |
| 630 C |
173 C |
| 814 C |
215 C |
| 1012
C |
287 C |
At how
high a temperature will the gold mirror continue to operate?
We advise
1100 C as the maximum temperature. They work at higher temperatures,
but the lifetime of the gold film is reduced.
As gold
melts at 1063 C, how can the mirror survive at 1100 C?
The surface
temperature of the gold film may see 1100 C 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,
lowering the temperature to the back side of the gold film. Do
not put anything around the gold mirror to interfere with the
cooling effect or the 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
customers insert a quartz tube through the furnace. Gas tight
fittings can be put on the tube and a vacuum or positive pressure
can be created inside the muffle. Warning! Whatever is used for
a muffle should be designed for the intended operation.
Other Matters:
What is
the biggest furnace and the smallest furnace and mirror you have
made?
| The
Longest |
IBM Tokyo,
Japan |
57 mm
x 26 feet |
| Largest
Diameter |
Aichi
Steel, Japan |
200 mm
x 500 mm |
| Smallest |
NASA,
Cleveland |
23 mm
x 50 mm |
| Mirrors: |
|
|
| |
Largest
Diameter |
300 mm
O.D. |
| |
Smallest
Diameter |
25 mm |
| |
Longest,
single section |
1500
mm |
| 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
supplies power to the elements that promotes a long life and no
fluctuations 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
