Adhesive bonding and miscellaneous chemical manufacture – Delaminating processes adapted for specified product – Delaminating in preparation for post processing recycling step
Patent
1981-02-11
1984-08-28
Bernstein, Hiram H.
Adhesive bonding and miscellaneous chemical manufacture
Delaminating processes adapted for specified product
Delaminating in preparation for post processing recycling step
156DIG67, 156DIG82, C30B 2306
Patent
active
044682786
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention concerns a process for the growth of a mono-crystal in a closed tubular chamber and the mono-crystals, obtained by that process.
BACKGROUND OF THE INVENTION
French Pat. No. 2,276,872 proposed to prepare mono-crystals of HgI.sub.2 in an ampoule, maintained under vacuum, produed with the aid of a vacuum pump. The known system comprises three zones: a sublimation zone, containing a charge of polycrystalline HgI.sub.2, taken to a temperature sufficiently high for the latter to sublime in the vapor state; an intermediate transfer zone, taken to an essentially constant temperature, higher than that of the sublimation zone; and a zone for the growth of the mono-crystal of HgI.sub.2, taken to a temperature lower than, or equal to, that of the sublimation zone. The transfer zone is brought continuously closer to the charge, in proportion to the growth of the mono-crystal. This process is complicated in operation, because it requires the use of a vacuum pump and of a mobile oven, having several windings. Besides, it is difficult to control the different parameters governing the seeding and the growth, so as to obtain mono-crystals without redhibitory structural defects.
Other processes, still more complicated, have been described in French Pat. No. 2,315,994 and U.S. Pat. No. 4,094,268.
There exists, therefore, a need for a process for the production of mono-crystals of good quality and of high purity in a closed chamber, which should be relatively easy to operate, does not require complicated and burdensome equipment and allows for good control of the parameters.
The object of the invention is to provide such a process.
SUMMARY OF THE INVENTION
The invention concerns a process for the growth of at least one mono-crystal, characterized in that:
(A) a source of the compound which is to form the mono-crystal is placed at one end of the ends of a chamber having a generally cylindrical shape. The compound source is selected from a group of compounds that are vaporizable or sublimable or reactive. The vaporizable or sublimable compounds are with or without dissociation, in the vapor state. The reactive compounds are capable of a reversible reaction with a reactive gas so as to yield a gaseous compound.
(B) When the compound source is formed by a vaporizable or sublimable compound, a vacuum is established in the chamber. On the other hand, when the compound source is formed by a reactive compound, the chamber is hermetically closed and filled with a reactive gas.
(C) In either case set forth in (B), the tubular chamber is heated to create in the latter a source zone and a deposit and sink zone in the chamber with the two zones having different uniform temperatures. The source zone includes the compound source and is heated to a temperature T.sub.s, at which vaporization or sublimation or reaction of the compound occurs. The deposit and sink zone includes the end of the chamber opposite to the source zone and is heated to a temperature T.sub.p which is lower than T.sub.s with an exothermic process and is higher than T.sub.s with an endothermic process. With the respective temperature relationship in the two zones, the vapor condenses or compound is dissociated, yielding the desired solid compound with deposition of material in a localized sink. The desired solid compound is previously formed from said material or from at least one of the two components of the latter and situated at that end or in the vicinity of the latter. The two zones, having different uniform temperatures, are connected by a transition zone, having a temperature gradient.
(D) The temperature difference .DELTA.T between the source zone and the sink and deposit zone is regulated to a value effective to cause nucleation of at least one discrete seed to take plae in the deposit zone of the chamber, at a point situated upstream of the sink, and
(E) Then, as soon as a seed or seeds appear(s), the value of the temperature difference .DELTA.T is modified to prevent nucleation of other seeds and to obtain a suitable r
REFERENCES:
patent: 3519492 (1970-07-01), Huml et al.
patent: 4282057 (1981-08-01), Faile
patent: 4299649 (1981-11-01), Gentile et al.
Beinglass et al., J. of Crystal Growth 42, 12/77, pp. 166-170.
Philips Technical Review, Scholz, vol. 28, 1967, No. 10, p. 316.
Schieber et al., J. of Crystal Growth 24/25, 1974, pp. 205-211.
Cadoret Robert M. M. H.
Omaly Jean E. M.
Robert Marc A.
Bernstein Hiram H.
Centre National d'Etudes Spatiales
Markva Neil F.
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