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PREFERENTIALLY HEATED CRUCIBLE

IP.com Disclosure Number: IPCOM000022820D
Original Publication Date: 1976-Feb-29
Included in the Prior Art Database: 2004-Mar-26
Document File: 2 page(s) / 243K

Publishing Venue

Xerox Disclosure Journal

Abstract

A method is disclosed for providing preferential heating to a crucible, e.g.~ a tube crucible, without the need for radiation shields, In the past1 tube crucibles were usually heated by passing a high current through the structure, thereby heating the metal which in turn melts the material causing it to evaporate. The present method is a process whereby the crucible is constructed in such a way that the areas not in contact with the evaporant can be heated to a different temperature than the areas which are in contact with the evaporant. The principles of heat radiation are used. It may be desirable to have the areas in contact with the evaporant material operate at a cooler temperature than the areas of the crucible not in contact with the evaporant. Therefore, the latter areas should be treated to provide a highly reflective surface (bright or

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XEROX DISCLOSURE JOURNAL

PREFERENTIALLY HEATED Proposed Classification CRUCIBLE U.S. Cl. 219/420
F. Erhart mt. CL F27b 14/00

A method is disclosed for providing preferential heating to a crucible, e.g.~ a tube crucible, without the need for
radiation shields, In the past

                          1 tube crucibles were
usually heated by passing a high current through the
structure, thereby heating the metal which in turn melts
the material causing it to evaporate. The present method
is a process whereby the crucible is constructed in such a way that the areas not in contact with the evaporant can
be heated to a different temperature than the areas which
are in contact with the evaporant. The principles of heat
radiation are used. It may be desirable to have the areas
in contact with the evaporant material operate at a cooler
temperature than the areas of the crucible not in contact
with the evaporant. Therefore, the latter areas should be
treated to provide a highly reflective surface (bright or

reflective) and the former areas treated to provide a high
emissive surface (black) . Therefore, with the same current density
1 the reflective areas will be relatively hotter than the black areas. Therefore, the inside area of the
tube crucible can be treated in a similar way. For
efficient heat transfer to the evaporant, the inside area
should be dark. The preferred apparatus is a tube cruci~
ble having an upper portion having a bright surface and a
lower portion having a dark surface. The temperature of
the upper ha...