Single-crystal – oriented-crystal – and epitaxy growth processes; – Processes of growth from solid or gel state – Using heat
Reexamination Certificate
1998-11-27
2001-10-09
Kunemund, Robert (Department: 1765)
Single-crystal, oriented-crystal, and epitaxy growth processes;
Processes of growth from solid or gel state
Using heat
C117S007000, C117S010000, C117S931000
Reexamination Certificate
active
06299681
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to the conversion of a polycrystalline article into a single crystal, and, more specifically, to the control thereof.
U.S. Pat. No. 5,427,051—Maxwell et al. discloses an apparatus and method for the solid-state conversion of polycrystalline alumina to single crystal sapphire. In that process, a local energy source, such as a carbon dioxide laser, heats one end of an alumina tube to a temperature approaching the melting temperature of alumina to initiate and automatically propagate solid-state single crystal conversion along the length of the tube. To prevent thermal shock, laser heat is applied in a ring around the tube by rotating the tube, and in one trial the tube is slightly translated in addition.
The configuration of an article and the application of the heat thereon affect whether or not single crystal conversion is obtained without undesirable thermal shocking.
Accordingly, there is a need for an improved conversion and control process for conversion of a polycrystalline article into a single crystal.
BRIEF SUMMARY OF THE INVENTION
A polycrystalline article is converted to a single crystal in a solid-state process. Heat is applied at a first end of the article to effect a predetermined spatial temperature profile thereat having a maximum temperature approaching a melting temperature of the article. The temperature profile is maintained to initiate conversion at the first end. The heat is moved along the article toward an opposite second end to correspondingly propagate the conversion along the article.
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U.S. Patent application Ser. No. 09/206,721, filed Dec. 7, 1998, (Docket RD-22721).
Azad Farzin Homayoun
Jones Marshall Gordon
General Electric Company
Kunemund Robert
Patnode Patrick K.
Stoner Douglas E.
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