US4038201A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Polycrystalline bodies and means for producing them
Assignee: Optovac Inc
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Filing: 1972-03-24
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Granted: 1977-07-26
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Expires: 1992-03-24
Abstract
Abstract Polycrystalline optical materials formed from halides of alkali and alkaline-earth metals and of other metals, and mixtures thereof, some of which contain selected additives to act as nucleators and grain-growth regulators, and also apparatus and method of producing these materials from a liquid melt are disclosed. The polycrystalline products have optical transmissions approaching those of single-crystal materials, but exhibit significantly higher resistance to thermal and mechanical shock.The disclosed method and apparatus allows formation of unshattered polycrystalline ingots of any desired size by uniform nucleation from a homogeneous melt, and involves the controlled uniform removal of heat from the solidifying mass alone or in combination with a continuous addition-solidification process, which results in the formation of a substantially clear polycrystalline body or ingot, free of voids, and composed of randomly oriented single crystal having grain growths in a range of from about 0.01 to 10 mm. cross dimension.
Inventors
- 👤 Walter A. Hargreaves
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 06:52
CPC Classifications
H; H05; H05B; H05B3/00; H05B3/62; C; C30; C30B; C30B11/00; C30B29/00; C30B29/10; C30B29/12; F; F27; F27D; F27D11/00; F27D11/02
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
271 words
A method for producing a polycrystalline material of high optical quality having a grain growth size in the range of about 0.10 to about 10.0 millimeters from a batch of crystalizable metal halide material which comprises heating said batch sufficiently to convert said batch to a homogeneous noncrystallized molten mass thereafter cooling the mass to a temperature which is within the polynucleation temperature range of the mass, the polynucleation temperature range of a substance being defined as the temperature range below the melting point of the substance at which a rapid uniform removal of heat results in the formation of numerous nucleation or independent crystallization centers which form without substantial growth at the expense of other crystals, by removing heat in predetermined directions of outflow therefrom, at a removal rate which is substantially equal in each direction of outflow thereby to initiate freezing of said mass as a plurality of individual crystals each of which cohere with others of said crystals in random crystal orientation, and induce substantially uniform contraction of the frozen material in directions in correspondence to the directions of heat outflow, the heat removal being effected at a controlled rate to maintain sufficient of said batch of material molten to flow into any voids produced in the frozen portion by contraction of the same, and through said frozen portion at a rate which is at least substantially equal to the rate of liberation of latent heat of fusion and specific heat from the remaining molten material as the latter freezes, and continuing heat removal at said rate until said mass is completely frozen into a solid polycrystalline material.
Claim 2
Independent Claim
271 words
A method for producing a polycrystalline material of high optical quality having a grain growth size in the range of about 0.10 to about 10.0 millimeters from a batch of crystalizable metal halide material which comprises heating said batch sufficiently to convert said batch to a homogeneous noncrystallized molten mass thereafter cooling the mass to a temperature which is within the polynucleation temperature range of the mass, the polynucleation temperature range of a substance being defined as the temperature range below the melting point of the substance at which a rapid uniform removal of heat results in the formation of numerous nucleation or independent crystallization centers which form without substantial growth at the expense of other crystals, by removing heat in predetermined directions of outflow therefrom, at a removal rate which is substantially equal in each direction of outflow thereby to initiate freezing of said mass as a plurality of individual crystals each of which cohere with others of said crystals in random crystal orientation, and induce substantially uniform contraction of the frozen material in directions in correspondence to the directions of heat outflow, the heat removal being effected at a controlled rate to maintain sufficient of said batch of material molten to flow into any voids produced in the frozen portion by contraction of the same, and through said frozen portion at a rate which is at least substantially equal to the rate of liberation of latent heat of fusion and specific heat from the remaining molten material as the latter freezes, and continuing heat removal at said rate until said mass is completely frozen into a solid polycrystalline material.
Claim 3
Dependent Claim
120 words
The method of claim 1 wherein the batch of crystallizable material is melted in a first zone heated to a temperature sufficient to melt the batch to molten state, the molten batch thereafter being transferred at a predetermined rate in a constricted course through an orifice to a second zone maintained at substantially the polynucleation temperature of said material, the removal of heat from said mass being effected when it is in said second zone, the transfer of material from said first to second zones being at such predetermined rate to provide that said material when received in said second zone is sufficiently molten to flow into any voids produced in any frozen material already present in said second zone.
Claim 4
Dependent Claim
32 words
The method of claim 2 further comprising establishing a thermal barrier around the material in said second zone to confine removal of heat from said material to a substantially uni-direction flow therefrom.
Claim 5
Dependent Claim
20 words
The method of claim 1 wherein the heating and cooling of said crystallizable material is effected in a vacuum environment.
Claim 6
Dependent Claim
21 words
The method of claim 1 wherein the heating and cooling of said crystallizable material is effected in an inert gas environment.
Claim 7
Dependent Claim
25 words
The method of claim 1 wherein the crystallizable material comprises a metal of group IIA and a halide of group VIIA of the periodic table.
Claim 8
Dependent Claim
23 words
The method of claim 6 further comprising mixing a nucleation additive material with said batch of crystallizable material prior to melting of same.
Claim 9
Dependent Claim
12 words
The method of claim 7 wherein the crystallizable material comprises barium fluoride.
Claim 10
Dependent Claim
12 words
The method of claim 8 wherein the additive material is lanthanum fluoride.
Claim 11
Dependent Claim
39 words
The method of claim 7 wherein heat removal is effected at a rate such as to produce freezing of the material in individual crystals having grain growths in a range of about 0.01 to about 10 mm. cross dimension.
Claim 12
Dependent Claim
19 words
The method of claim 7 wherein the additive material comprises 0.1 to 50 percent by weight of the batch.
Claim 13
Dependent Claim
33 words
The method of claim 1 further comprising annealing said solid polycrystalline material by subjecting same to a controlled heating of predetermined magnitude for a predetermined period of time to relieve residual stresses therein.
Claim 14
Dependent Claim
14 words
The method of claim 12 wherein the annealing is effected in a vacuum environment.
Claim 15
Independent Claim
264 words
A method for producing a polycrystalline material of high optical quality having a grain growth size in the range of about 0.01 to about 10.0 millimeters from a batch of crystalline metal halide material which comprises heating said batch in a first zone sufficiently to convert said batch to a homogeneous noncrystallized molten mass, thereafter transferring said molten material at a predetermined rate and subjecting said mass in said second zone to cooling at substantially the polynucleation temperature thereof, the polynucleation temperature range of a substance being defined as the temperature range below the melting point of the substance at which a rapid uniform removal of heat results in the formation of numerous nucleation or independent crystallization centers which form without substantial growth at the expense of other crystals, by removing heat in a substantially unidirectional flow therefrom, thereby to initiate freezing of said mass as a plurality of individual crystals each of which cohere with other of said crystals in random crystal orientation, and induce contraction of the frozen material substantially in the direction of heat outflow only, and at a substantially uniform heat removal rate from the mass to maintain sufficient of said material molten to flow into any voids produced in the frozen portion by contraction of the same and through the frozen portion thereof which is at least substantially equal to the rate of liberation of latent heat of fusion and specific heat from the remaining molten material as the latter freezes, and continuing heat removal at said rate until said mass is completely frozen into a solid polycrystalline material.
Claim 16
Independent Claim
264 words
A method for producing a polycrystalline material of high optical quality having a grain growth size in the range of about 0.01 to about 10.0 millimeters from a batch of crystalline metal halide material which comprises heating said batch in a first zone sufficiently to convert said batch to a homogeneous noncrystallized molten mass, thereafter transferring said molten material at a predetermined rate and subjecting said mass in said second zone to cooling at substantially the polynucleation temperature thereof, the polynucleation temperature range of a substance being defined as the temperature range below the melting point of the substance at which a rapid uniform removal of heat results in the formation of numerous nucleation or independent crystallization centers which form without substantial growth at the expense of other crystals, by removing heat in a substantially unidirectional flow therefrom, thereby to initiate freezing of said mass as a plurality of individual crystals each of which cohere with other of said crystals in random crystal orientation, and induce contraction of the frozen material substantially in the direction of heat outflow only, and at a substantially uniform heat removal rate from the mass to maintain sufficient of said material molten to flow into any voids produced in the frozen portion by contraction of the same and through the frozen portion thereof which is at least substantially equal to the rate of liberation of latent heat of fusion and specific heat from the remaining molten material as the latter freezes, and continuing heat removal at said rate until said mass is completely frozen into a solid polycrystalline material.
Claim 17
Dependent Claim
149 words
A polycrystalline material consisting essentially of polynucleated barium fluoride with lanthanum fluoride as the nucleating agent present therein in localized concentrations wherein said material has optical transmission characteristics similar to single crystal barium fluoride in the range of about 0.5 to about 15 UM, and is characterized by a solid mass of plurality of individual crystals each of which is cohered with others in a random orientation with the crystal grain growth size of said crystals on the average being in the range of about 0.10 to about 10 mm. and further characterized by (a) the absence from the mass of dentritic voids and like spaces, (b) the absence of impurities in the crystal grain boundaries such that there is no appreciable light scattering and absorption by the polycrystalline material and (c) no appreciable variation in the crystalline material of optical transmission over the regions of the optical spectrum.
Claim 18
Dependent Claim
149 words
A polycrystalline material consisting essentially of polynucleated barium fluoride with lanthanum fluoride as the nucleating agent present therein in localized concentrations wherein said material has optical transmission characteristics similar to single crystal barium fluoride in the range of about 0.5 to about 15 UM, and is characterized by a solid mass of plurality of individual crystals each of which is cohered with others in a random orientation with the crystal grain growth size of said crystals on the average being in the range of about 0.10 to about 10 mm. and further characterized by (a) the absence from the mass of dentritic voids and like spaces, (b) the absence of impurities in the crystal grain boundaries such that there is no appreciable light scattering and absorption by the polycrystalline material and (c) no appreciable variation in the crystalline material of optical transmission over the regions of the optical spectrum.
Claim 19
Dependent Claim
20 words
the polycrystalline material of claim 15 wherein said material includes from about 0.1 to about 50 percent of lanthanum fluoride.
Claim 20
Dependent Claim
37 words
The polycrystalline material of claim 15 wherein said material has an optical transmission curve showing transmission from about 0.500 to about 15 UM (micrometers) and polycrystalline grain growths of about 0.01 to about 2.00 millimeters in size.
References Cited (Backward Citations)
US3453215A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1980-07-25 | 1981-01-24 | 1981-07-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-07-25 | 1985-01-24 | 1985-07-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-07-25 | 1989-01-24 | 1989-07-26 | $7700.00 | Window Closed / Lapsed |