CA2163663A1 - Filtering flow guide for hydrothermal crystal growth - Google Patents
Filtering flow guide for hydrothermal crystal growthInfo
- Publication number
- CA2163663A1 CA2163663A1 CA002163663A CA2163663A CA2163663A1 CA 2163663 A1 CA2163663 A1 CA 2163663A1 CA 002163663 A CA002163663 A CA 002163663A CA 2163663 A CA2163663 A CA 2163663A CA 2163663 A1 CA2163663 A1 CA 2163663A1
- Authority
- CA
- Canada
- Prior art keywords
- opening
- inlet conduit
- flow guide
- crystal
- reaction vessel
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B7/00—Single-crystal growth from solutions using solvents which are liquid at normal temperature, e.g. aqueous solutions
-
- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
- C30B29/10—Inorganic compounds or compositions
- C30B29/16—Oxides
- C30B29/18—Quartz
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T117/00—Single-crystal, oriented-crystal, and epitaxy growth processes; non-coating apparatus therefor
- Y10T117/10—Apparatus
- Y10T117/1024—Apparatus for crystallization from liquid or supercritical state
- Y10T117/1096—Apparatus for crystallization from liquid or supercritical state including pressurized crystallization means [e.g., hydrothermal]
Abstract
The present invention is a filtering flow guide for hydrothermal reaction vessels - such as crystal growth apparatus - which improves crystal production efficiency and crystal quality without significantly slowing down flow velocities or crystal growth times. One embodiment of the flow guide fits inside a conventional hydrothermal autoclave for crystal growth, and includes at least one central inlet conduit by which crystal nutrient solution flows from the autoclave's dissolving zone into its growth chamber. A plurality of funnels encircle the inlet conduit, the funnels contaguous with each other along their lateral edges and with the inlet conduit's intake opening at the funnels' innermost edges. Each funnel may be substantially shaped as a hollow, inverted triangular pyramid with a nadir instead of an apex, the nadir opening into a filter-containing outlet. The inlet conduit, plurality of funnels and outlet tubes guide the flow of crystal nutrient solution optimally through the autoclave's dissolving and growth chambers, producing an even flow rate and pattern, and reducing wasteful crystal deposition. The inlet conduit, the funnels, or both elements, may further include optional filters positioned to enhance convective solution flow with minimal flow impedance. The flow guide thereby also filters out contaminants, producing high-purity, high-perfection crystals.
Description
~O 94128204 2 1 6 3 6 6 3 PCT/US94/05775 Filtering Flow Guide for Hydrothermal Crystal Grov~th Background of the Invention The present invention relates generally to hydrothermal apparatus and methods 5 for growing single crystals, and particularly, to guiding flow and filtering solution within hydlolh~....~l growth processes.
There exists a great ~lem~n-l for single crystals, such as cY-quartz, of high purity and crystalline perfection for frequency control applications in the radio, television, teleco.~ nirations~ and electronics industries. Hydrothermal 10 techniques have been used to grow high-perfection single crystals for these and other applications.
To s~rnm~rize the conventional process, a near-insoluble crystal nutrient or starting material is immersed in an aqueous solvent within a closed-volume, steel autoclave. The contents are super-heated, thereby exp~nrling the solvent to fill the 15 entire autoclave, ~l~S~uliGillg the cGIllen~, and inducing dissolution of the crystal nutrient in a first zone of the autoclave. A lenlpelalule gradient is applied toencourage convective flow of the nutrient-laden solution from the first zone to a second zone having a dirrel~n~ lelllpcldlule. The solution reaches its satuMtionpoint and the crystal nutrient precipi~les out in the second zone. Racks of seed20 crystals are usually provided in the second zone as nl-cle~tion points in order to minimi7l~ random self-nucleation of the ~ul~ie~l~. The reader is directed to theprior art on hydrothermal crystal appa~alus and methods for greater details thandisclosed in the following paragraphs. See, e.g., Sullivan, U.S. Patent 2,994,593 (Aug. 1, 1961); Kolb, U.S. Patent 3,271,114 (June 15, 1964); V.A. Kuznetsov 25 and A.N. Lobachev, "Hydrothermal Method for the Growth of Crystals", Soviet Physics--Crystallography, vol. 17, no. 4 (Jan.-Feb., 1973); R.A. T~ e, "HydrothPrm~l Synthesis of Crystals", Special Report, C&EN, Sept. 28, 1987, pp. 30-42.
Several factors affect the quality of hydroth~nn~lly grown crystals and the 30 ef~lciency of crystal production. They include~ ,ilies present in the starting materials or introduced into the solution by corrosion of the autoclave vessel and baffle; the quality of the seed crystals used for nll~le~tion; flow patterns of the dissolved nutrient within standard autoclave set-ups; baffle designs; and telllpel~-ture and pressure fluctuations affecting ullirollllity of growth rates. See, e.g., Balascio et al., "Factors Affecting the Quality and Perfection of HydrothermallyGrown Quartz", Proc. 34th Annual Symposium on Frequency Control, 65-71 (1980); Klipov et al., "Influence of Convective Flows on the Growth of SyntheticQuartz Crystalsn, Proc. 45th Ann. Symp. Freq. Control, 29-36 (1991); Johnson et al., "Experimental D~lellllhlalion of the Relationship among Baffle, TemperatureDirrelcnce and Power for the Hydrothermal Growth of Quart_", 43rd Ann. Symp.
Freq. Control, 447-458 (1989).
Various efforts have been directed at controlling these factors. For example, inert or noble metal linings have been proposed for reaction vessel walls, baffles, seed racks and seed clips. Such linings better with~t~n.l the solvent's corrosive effects and minimi7e formation of iron and other metal silicates, thereby reducing inclusions within the final crystals. Etched, dislocation-free seed may also be used on which to grow low-dislocation crystals for high-frequency applications. See, e.g., Barns et al., "Dislocation-free and low-dislocation quartz p,el)aled by hydrothermal cryst~lli7~tion", J. Crystal Growth 43, 676-686 (1978); Croxall et al., "Growth and Charac~e"~alion of High Purity Quartz", Proc. 36th Ann. Symp.
Freq. Control, 62-65 (1982); Armington et al., "The Growth of High Purity, Low Dislocation Quartzn, Proc. 38th Annual Symp. Freq. Control, 3-7 (1984).
Greater amounts of aqueous solution may be used in low-plessure hydrotht-rm~l crystal growth processes to produce high-quality crystals of silicon-free materials.
See, e.g., Caporaso et al., U.s. Patent 4,579,622 (Apr. 1, 1986).
Persons skilled in the art of hydrothermal crystal growth have also recognized that dissolved llullielll and solvent flow back and forth randomly, even turbulently, between dissolving and growth zones of an autoclave. This problem is inherent with the use of conventional baffles-flat perforated disks-which tend to promoterandom mixing rather than convection See, e.g., ~nn~m~l~i et al., "Effect of Convective Baffle & T ithil-m Nitrite and Lithium Nitrite Dopants on Hydrothermal Growth Rate of Quartz Single Crystalsn, 21 Indian J. Tech. 425-430 (Oct. 1983).
Random flow promotes ~aslerul nucleation of dissolved nutrient on autoclave walls and components, and the solvent's corrosion of these co",po"e,ll~ which are typically made of steel. As well, signifirant amounts of illl~uli~ies--including o 94128204 2 1 6 3 6 6 3 PCT/US94/0577~
iron or al~lminl~rn silicates and gas bubbles--acc~ te to form inclusions in thecrystals grown. Furthermore, crystal formation is non-uniform throughout the autoclave's growth zone, according to the influence of concentrative and convective flows. Klipov et al., Proc. 45th Ann. Symp. Freq. Control, 29-36 (1991).
~ nn~m~l~i et al. ~ cllcsed the desirability of a better mt~çh~ni~m of fluid flow within hydrothermal systems: i.e., convective fluid flow is ~l-,rell~d over random mixing of cooler and hotter fluids within a hydrothermal system. They discuss the merits of a "convection baffle" of their design in promoting convective flow, 10 but disclose no specific details of their baffle design. They experimented with adding syphons and e~lel1ding tubes to their baffle to --i--i---i7~' mixing at the fluid exchange boundary, but soon abandoned these fi~ s as significantly impeding flow rate. Ann~m~l~i, 21 Indian J. Tech. at 426, col. 2.
In U.S. Invention Reg. No. H580 (Feb. 7, 1989), "Method and Apparatus for 15 Growing High Perfection Quartz", Vig imposed "forced convection" on a hydro-thermal system to reduce crystal hllp~,~re~;lions and inclusions. A se~al~ filter vessel and pump are attached to a crystal growth autoclave to circulate solutionthrough the autoclave in one direction--from dissolving zone to growth zone to filter vessel back to dissolving zone--in a continuously recircul~ting pathway.
20 However, use of a second autoclave as a filter vessel complicates and lengthens the hydrothermal process, and adds significantly to the cost of hydrothermal crystal growth. The filter vessel increases the volume of the system, thereby making it more difficult to m~int~in constant pl~S~Ulc and to control zone ~elll~ res. Furthermore, forced convection tends to carry co.-l;....i.unt particles 25 along with the crystal nutrient solution, increasing the risk of crystal inclusions.
Vig's device provides a filter to remove co..~ nt particles from nutrient-depleted solution, but only after the dissolved lluLliclll and cont~min~nt~ havealready passed through the growth c~l~mher.
Therefore, an unfulfilled need remains for a simple, cost-effective way to 30 improve flow p~U~ s in conventional hydrolllellllal crystal growth apparatus,thereby improving crystal quality and the efficiency of crystal production such that wasteful crystal deposition is minimi7~d. There also remains a need for reducing 2 1 6 3 6 6 3 PCT/US94/0577~, the level of illlyùlities present in the llu~ ,nt-laden solution during crystal growth, which reduces the inclusion density and increases the degree of crystal perfection.
Summary of the Invention The present invention provides an inexpensive and simple means for improving flow of and filtering solution within processes such as hydrothermal crystal growth, thereby improving crystal quality and efficiency of crystal production.
Specifically, this invention can both filter and guide a flow of crystal nutrient-laden and -depleted solution optimally through a hydrothermal reaction vessel's dissolving and growth zones, thereby reducing crystal inclusions and flaws and avoiding wissLer~ll crystal deposition on the vessel walls. The filtering flow guide of this invention thereby produces high-purity, high-yelre~tion crystals and m~ximi7es efficiency of crystal production. Furthermore, the invention is easilyadapted to replace a conventional, prior art baffle, and to fit inside known hydrothermal autoclaves.
In one emobo~im~nt, the flow guide has a central inlet conduit and a plurality of tapering funnels sealably abutting each other and radially surrounding the inlet conduit. The flow guide's configuration allows convective flow of solution through the inlet conduit in one direction, and through the funnels in the otherdirection. The flow guide may be vertically positioned in a ~ndard hydrothermal reaction vessel or autoclave, with the funnels serving to separate the autoclave's dissolving and growth zones. Nutrient-laden solution flows through the central inlet conduit from the dissolving zone to the growth zone. Nutrient-depleted solution flows from the growth zone to the dissolving zone through each funnel.
In another emborlim~nt, a filter-cont~inin~ flow guide is provided wherein filters are disposed within the inlet and outlet conduits so as to trap or adsorb il-lyulilies from the crystal solution, while preserving continuous convective solution flow within a hydrotherrnal reaction vessel.
-Brief Des..ilJtion of the D~wi~
In the drawing:
Fig. 1 is a schematic representation of an hydrothermal crystal growth apparatus;
Fig. 2 is a cut-away, pel~ec~ e view of a filter-cont~ining flow guide of this invention placed within a conventional, cylindrical hydrothermal autoclave (not drawn to scale), with arrows inr1ic~ting a desired convectional flow pattern for the dissolved crystal;
Fig. 3 is a perspective view of the filter-cont~ining flow guide alone;
Fig. 4 is a cut-away perspective view of the filter-cont~ining flow guide;
Fig. 5 illustrates alternative embodiments of the flow guide, with Figs. 5(a) and (b) being pe~ye~ e views and Fig. 5(c) a top view of a flow guide having one central inlet conduit ~ulloullded by a plurality of funnels supported in a sealing collar;
Fig. 6 show (a) top and (b) side views of a flow guide having two inlet conduits ~ulloullded by a plurality of funnels supported in a sealing collar, and (c) top and (d) side views of the same further including filters; and Fig. 7(a) and (b) are longitll~lin~l, sectional views of two possible filter arrangements for a flow guide, drawn in SC~nl:~tic form and not to scale.
Desc~ ion of the Preferred F.mho,li.~
The filtering flow guide of this invention is designPd to prevent random or turbulent flow patterns of both crystal-laden and crystal-depleted solution between the dissolving and growth chambers of an hydrothermal reaction vessel and along the vessel's interior surfaces, and to filter out CO.~ .lc in the solution.
Fig. 1 shows a schematic of a conventional hydrothermal crystal growth apparatus, colll~lisillg a vertical autoclave or reaction vessel 12 contained within a furnace 10. The reaction vessel has two chambers or zones m~int~in~d at different le1~e1~lU~S by ~ull~ ding heater bands: a "dissolving zone" 13 and a "growth 30 zone" 14. The solubility of most crystals and their minerals increases with te~ )el~lule, so conventionally, the dissolving zone 13 is located at the bottom of the autoclave and is at a higher tell~el~lul~ than the growth zone 14 located at the WO 94/28204 2 1 6 3 6 6 3 PcTlus94los77s top of the autoclave. A prior art baffle 17--typically a perforated disk--is shown in Fig. 1 to separate the dissolving and growth chambers 13 and 14, for m~int~ining the tell~pel~u~ dir~ ial between those zones while permitting flow of solution between the dissolving and growth chambers. The reaction vessel 12 5 has an opening at the top of the growth zone 14, which is sealed shut by a sealing closure 15 after the reaction vessel 12 is filled with the apyropliate starting materials for the hydrothermal crystal growth process.
In the dissolving zone 13, a crystal lluLIielll 16 such as crushed quartz, is immersed in an aqueous solvent, such as a strongly basic solution of sodium 10 hydroxide or sodium carbonate. The solvent's starting volume is usually at least one-third of the reaction vessel 12, and may be varied according to the desired y~s~ule upon super-heating. The solvent is heated to suy~cliLical conditions, allowing it to expand to fill the vessel 12 and to dissolve the crystal l~uLIient supply 16. Hydrothermal conditions may be varied according to the desired 15 hydrothermal reaction or crystal product. For in.ct~nre, typical conditions for growing electronic grade quartz require reaction yles~ures of about 1000-2000 atm, and l~lllpeldtures of 325450C in the dissolving zone and 300400C in the growth zone (i.e., the latter is 25-100C cooler than the dissolving zone).
The crystal nutrient-laden solution flows upwardly from the hotter dissolving 20 zone 13 into the cooler growth zone 14, by natural or "buoyant" convection. The nutrient-laden solution becomes super-saturated in the cooler growth zone and excess crystal solute precipitates out of solution. Typically, racks of seed crystal 18, like c~-quartz, are provided as nl-cle~tion points, resulting in more orderly growth of single crystals. The cooled, nutrient-depleted solution then sinks back 25 down to the dissolving zone 13, where it reheats, dissolves more of the nutrient supply 16 and flows upward again. The hydrothermal cycle repeats itself until the nutrient supply 16 is exh~ te(l. The hydrothermal crystal growth process typically takes days to months to grow crystals suitable for commercial use.
In a few in~t~nreS in which a crystal's solubility decreases as lell~ye~lule 30 increases beyond a certain range, the positions of the dissolving and growth zones may be reversed. A cooler dissolving chamber which supports a nutrient supply would be located on top of a warmer growth chamber. The crystal nutrient-laden ~O 94l28204 2 1 6 3 6 6 3 PCT/US94/05775 -solution would flow convectively from the upper chamber down into the lower growth chamber where the llullitl,L would crystallize.
Fig. 2 shows a filter-cont~ining flow guide 20 of this invention, specifically adapted to fit inside a cylindrical hydrothermal autoclave or reaction vessel 12 in 5 which the crystal growth zone 14 lies atop a bottom dissolving zone 13. The flow guide 20 may be made of tempered steel or other suitable material for with-st~n-ling the lel~pelaLu~es, plCSsul~s, and corrosive conditions of the hydrothermal process. Inert or noble metals or nickel-based super-alloys may be used to make or to coat the flow guide 20 for even fewer crystal flaws.
Referring generally to Figs. 2-5, the flow guide 20 has at least one central inlet conduit 22 having a first opel~ing 23 and a second opening 26, the conduit's first opening 23 being within or proximate to the dissolving chamber when the flow guide is placed within a hydrothermal autoclave. The inlet conduit 22 may be fitted with an optional filter 27 colll~lising trapping material such as wire mesh or 15 steel wool, or suitable adsorbing material. Referring to the embodiments of Figs. 2 and 7(a), arrows 24 in~lir~te that crystal nutrient-laden solution flowsupward from the autoclave's dissolving zone 13, through the first opening 23, along the inlet conduit 22, out through the second opening 26 and filter 27, andinto the growth chamber 14. The filter 27 serves to trap trace illl~u~iLies such as 20 iron and al-lmin-lm silicates before the crystal nutrient-laden solution enters the growth chamber 14 where crystal growth occurs. Filtering out illll~uLiLies from the nutrient-laden solution reduces the amount of inclusions and dislocations in thefinal crystal product.
A plurality of outlet conduits--shown as outlet funnels 30 in Figs. 2-5--25 sealably abut each other and the inlet conduit 22 so as to ~ulloulld the inlet conduit radially. Optirnally, the outlet funnels 30 are fused together in a ring configura-tion similar to segments in half an orange, while each funnel connects to the inlet conduit 22 at or near the latter's first, inlet o~el"ng 23. Each funnel 30 preferably tapers from a first opening 39 to a second opening 40 having a smaller cross-30 sectional area than the funnel's first opening. In a most p,ef~lled embodiment, each funnel 30 is shaped subst~nti~lly like a hollow, inverted triangular pyramid whose apex is inverted to become the second opening 40 at a nadir of the funnel WO 94t28204 2 1 6 3 6 6 3 PCTIUS94/05775 30. That is, the outlet funnel 30 has two subst~nti~lly triangular lateral walls 32 with straight upper edges 31; a curved, subst~nti~lly triangular outer wall 34 with an oulw~rdly convex upper edge 33; and an inner wall 36 with a concave or inwardly curved upper edge 35 adjoining the inlet conduit 22. Each funnel 30 5 contiguously adjoins at least one adjacent funnel along the funnels' straight lateral upper edges 31, and adjoins the inlet conduit 22 at the funnel's innermost edge 35.
The funnels' outermost edges 33 together form a circle whose outer diameter is substantially equal to the reaction vessel's inner ~ llrl~ 1, thereby allowing the flow guide 20 to fit snugly within the reaction vessel 12.
Agains with ~ nce to Figs. 2-4, the funnel's second opening 40 may further open contiguously into an optional outlet tube 42 having a distal opening 44. The outlet tube 42 may further include an optional filter 46 proximate to the distalopening 44, to remove cont~min~nt particles from the llulliellt-depleted solution, including alllmin~m silicates, iron silir~tes, and other by-products of solvent 15 interactions with the vessel 12 or the flow guide 20.
For non-impeded flow, the cross-sectional area of the inlet conduit 22 preferably equals the sum of the cross-sectional areas of each funnel's narrowest point (e.g., the funnel's second opening 40) or, if present, of the outlet tubes 42.
The funnel walls are preferably angled steeply, nearly vertically. This arrange-20 ment permits a steady, non-random, non-mixing flow in the plefelled order:
(i) flow of crystal nutrient-laden solution through the inlet conduit 22 to the growth chamber 14; and (ii) flow of l~u~ielll-depleted solution through the funnels 30 and the outlet tubes 42, back into the dissolving zone 13. A most l)lefell~,dembo~lim~nt7 for use in standard hydrothermal autoclaves, has eight funnels 30 25 ~ulluunding the inlet conduit 22. An eight-funnel arrangement allows the funnel walls 32, 34, and 36 to be steeper than is possible with only four funnels covering the same autoclave volume. Making the funnel walls as steeply angled for just four funnels as for eight, results in funnels tending to be too bulky and intrusive for a standard, commercially available l.~/dro~.~,llllal autoclave, thereby tending to 30 impede flow excessively and to decrease crystal productivity.
Also shown in Fig. 2, a filtering means 50--such as wire mesh, steel wool, other filtering material, or çh~mir~l adsorbants--may be packed between the o 94/28204 2 1 6 3 6 6 3 PCT/US94/05775 funnels' outermost edges 33 and the vessel 12 to seal any space between the two, further reducing any random flow of solution between the dissolving and growth zones along the vessel walls and filtering out co~ ll;n~ from the solution.
In the most prerel,ed embodiment of Fig. 2, the heated l~uLlien~-rich solution flows tup through at least one central inlet conduit 22 through a central region of the growth zone 14--as inrlir~t~P~ by arrows 24--where it deposits the nutrientsonto racks of seed crystals 18. The cooled, nutrient-depleted solvent then flowsalong a peripheral region of the vessel 12 in the growth zone 14 to the dissolving zone 13 through the funnels 30 and outlets 42--as intlic~te~l by arrows 28. Uponthe filtered solvent's return to the dissolving chamber 13, it can reheat and further dissolve rern~ining crystal llullielll supply 16.
Various configurations for the flow guide 20 are possible. Although not illustrated, one embodiment of the flow guide may have subst~ntiAlly reverse configurations from those shown in Figs. 2-6, or be fitted upside-down in those hydrothermal a~pdld~uses having a growth zone at the bottom of the autoclave, with the crystal nutrient supply--e.g., a basket of lascas--suspended in an upper dissolving zone. The flow guide may also be adapted for horizontal use--e.g., ina hy~lroLl~llnal reaction vessel having the dissolving and growth zones side by side rather than atop each other and ol)eld~ g through forced convection.
AlLelnaLi~ely, as shown in Figs. 5(a)-(c), each outlet funnel 30 may have a subst~nti~lly conical shape with subst~nti~lly elliptical (e.g., circular) cross-sections as well as elliptical first and second opellings 39 and 40. It is plcfcll~d but not essential that the funnels 30 are contiguous with each other and with the inlet conduit 22. A plurality of the funnels 30, while m~int~ining their radial configuration around the inlet conduit 22, may be slightly spaced apart from each other and the inlet conduit, but a sealant or col-nP~;"g structure must then be disposed between the funnels and inlet conduit for support and to prevent randomflow. For in~t~nre, a plurality of the funnels 30 may fit contiguously within a circular collar 60 which, in turn, sealably surrounds the inlet conduit 22.
Fig. 5(a) shows the most pler~,lr~d longitudin~l relationship of the inlet conduit 22 to the outlet funnels 30, in which the inlet conduit's first opening 23 is proximate with each funnel's first opel~illg 39, such that both openings occur at the boundary Wo 94t28204 2 1 6 3 6 6 3 PCTtUSg4/05775 between the dissolving and growth zones when the flow guide 20 is placed within a hydrothermal reaction vessel. Alternatively, as in Fig. 5(b), the first opening 23 of the inlet conduit 22 may be positioned closer to the second openings 40 ofthe funnels 30, with the inlet conduit's first opening 23 protruding into the 5 dissolving zone of a hydrothermal reaction vessel in which the flow guide 20 is placed. However, the inlet conduit's and the funnels' first openings 23 and 40 are pl~efcllcd to coincide within the same cross-sectional plane (to be sitn~t~ at the boundary between the dissolving and growth zones), to minimi7P any dead-space occurring belweell the inlet conduit 22 and the funnels 30 which could trap fluid or 10 other material, or cause turbulence in solution flow from the dissolving to the growth zone.
Allc~ ively, Fig. 6(a)-(d) illustrates embo~lim~nt~ of the flow guide 20 providing more than one inlet conduit 22. Here, two inlet conduits 22 are centrally located within a radially ~ulloul~ding collar 60 supporting a plurality of 15 conical funnels 30. The cross-sectional area of each inlet conduit 22 should still exceed the individual cross-sectional area of each funnel's second opening 40; but the sum of the total inlet cross-sectional areas preferably remains subst~nti~lly equal to the sum of the total outlet cross-sectional areas.
Fig. 7(a)-(b) focuses on the filtering aspect of the invention, providing 20 longit~in~l, schematic views of simple embo(1im~nt~ of filter arrangements for a flow guide 20. An efficient filtering effect can be achieved even with outlet funnels 30 which are subst~nti~lly cylindrical tubes rather than tapering funnels, as long as the cross-sectional area of the inlet conduit 22 substantially equals the sum of the cross-sectional areas of the outlet funnels 30. Furthermore, various 25 arrangclllcll~s of filter-cont~ining inlet and outlet conduits are possible to provide a filtering flow guide. Cylindrical outlet conduits 30 may radially and sealably abut at least one cylindrical inlet conduit 22 and each other, as for the embodiments of Figs. 2-4, and Fig. 6(a). Al~cllla~ivcly, the relative positions of the outlet and inlet conduits could be lcvcl~ed as in Fig. 6(b). Even a side-by-side arrangement 30 is possible, wherein a single inlet conduit and a single outlet conduit each have, e.g., a semicircular cross-section, and sealably abutting each other so as to fit snugly within a cylindrical hydlotl,cllllal reaction vessel.
The hn~ll~nl factor--especially for a non-tapering flow guide em~d~ment a in Fig. 7--is to have the inlet conduit filter 27 spaced apart from the outlet funnel filters 46 along the flow guide's longih)~lin-q-l axis, to mqintqin directed convective flow while achieving effective filtration. Most preferably, the filter 27 may bedisposed proximate to the inlet conduit's second opel~g 26, at a lon~it~ inql tqnl~e from the filters 46 disposed near the second o~nings 40 of the funnels 30, as shown in Fig. 7(a). When this filter arrangement is placed within a hydlo~ reaction vessel 12, the filter 27 would be sih~qt~d proximate with the growth zone 14 while the filter 46 would be proximate with the dissolving zone 13. Due to the dirÇ~"elllial flow ~c~ e re~lltin~ from the spaced-apart a~ ge~ ,.ll of the filters 27 and 46 in a non-la~.ing flow guide 20, crystal llullie.ll-laden solution would tend to flow through the vessel's center from the dissolving to the growth zone, while crystal-depleted solution would tend to flow along the vessel's peli~ from the growth to the dissolvhg zone.
Refelling to Fig. 7(b), it is also possible to reverse t~,e relative positions of the inlet and outlet conduit filters in the non-lapelillg flow guide 20, so as to promote an opposi~ flow direction. A plurality of p~ l inlet cori.lui~ 22' sealably and radially abut at least one central outlet conduit 30'having a first o~ning 39' and a second o~nillg 40'. A filter 46' is posilioll~d within the central outlet tube 30' plo~ e to the second opening 40'. A filter 27' is posiliol~ within each peliphelal inlet tube 22' having a first o~nil~g 23' and a second opening 26', the filter 27' proximate to the second o~ning 2C'. By placing a flow guide having this filter a~ in a l~dr~elll.al reaction vessel 12, one can promote coll~ , flow of solution from the dissolving zone 13 to the growth zone 14 through the ~~ }~lal inlet tube 22' along the vessel's ~liphel~ (arrows 24') and then past the crystal seed racks 18. Solution would flow from the growth zone 14 back to the dissolving zone 13 through the centrally located outlet conduit 30' in the vessel's center (arrows 28').
Of course, both filt~q,tion and coll~ i./e flow effects are mq~i..li,~cl in the 30 most p.efell~d embodiment of the present filter-con~ g flow guide 20, shown in Figs. 24. In ~ , the entire configuration of the pr~f~ .d flow guide's inlet conduit 22, funnels 30, and outlet tubes 42--both with and without the help AMENDED SltEEr 21 63663 PCTi'j~ 94/05775 IPEA/U~ 2 ~ SEP ~^n5 of the filters 27 and 4fi helps to guide the convection ~;urle~ from the dissolving zone 13 into the growth zone 14 upward (arrows 24) through the center of the reaction vessel's interior, then back down (arrows 28) along the pe.il)hel~ of the vessel's interior to the dissolving ch~mber 13. The flow guide promotes well-S defined, recirc~ tin~ flow pall~,lllS within the growth and dissolving zones. Thisflow pattern results in more even crystal growth and a more ul~irollll growth rate throughout the reaction vessel. Improved crystal quality is obtained with filters by reducing the inclusion or im~ y density.
The flow guide of the present invention has been tested in conventional 10 hydloLlle.~l growth of clecLlvl~ic-grade quartz crystals at high ~les~ules and lelll~laLul~s, ~u~ lly as ~ u3secl previously. The present invention greatly improves the quality of crystals grown in conventional l~dfoLll~.lllal autoclaves.
Table 1 COI~)~S the inclusion ~ nc~ s of ele.,Llonic-grade a-quartz grown with and without the filter-co.~ ;ng flow guide 20.
D A~er~ge ~ ' Den~ Worst~ e 1 ' Density(no. of ' 'cm3) (no. of ' 'cm3) >100 micron,without flow guide ` 0.1 0.9 with flow guide 0.001 0.01 70-100 micron, without flow guide0.8 2.5 with flow guide 0.01 0.2 2530-70 micron, without flow guide 1.5 3.6 with flow guide 0.3 0.6 Analysis by sc~l~n;n~ electron Illicr~scope (SEM) showed that a-quartz grown with this il~ ion had sigl~;r~r~ y leluced ~mollnt~ of inrll.~ ons e.g., acmite (NaFe(SiO3)2) and e~ h.).;le (Li2Na4Fe2Sil2030)--as cOlll~al~l to crystals 35 grown without the present filtering flow guide. For example, the average density tr~--~T
O 94/28204 PCT/US94/0577~
of inclusions larger than 100 microns was 100 times less in crystals grown with the present filtering flow guide, than in crystals grown with conventional baffles.
At the same time, use of the present filtering flow guide 20 m~int~in~ substantially the same crystal growth rate and flow velocities as hydrothermal crystal growth 5 methods using standard perforated disk baffles. However, the flow guide 20 minimi71oS useless and wasteful cryst~lli7~tion along the reaction vessel walls, since the flow patterns promoted by the flow guide cause the llullielll-depleted solution to return along the vessel walls, which can dissolve any crystal deposits on thewalls. Moreover, the flow guide has been observed to reduce corrosion of the 10 reaction vessel, as compared to conventional baffles. Analysis of residues--on and within the flow guide, and on the autoclave's bottom--show that small, unavoidable amounts of illll~ufilies (e.g., acmite, em~lel~site) do occur, but are largely collected on the flow guide and its filters. Finally, this invention further improves over the prior art in that it is easily adapted to fit into standard crystal 15 growth appalalus and elimin~tPs the need for any other baffle, filter, or pump.
Further embodiments of the invention will be a~,al~ to those skilled in the art from a consideration of this specification or the practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with the true scope and spirit of the invention being intlic~t 20 by the following claims.
What is claimed is the following:
There exists a great ~lem~n-l for single crystals, such as cY-quartz, of high purity and crystalline perfection for frequency control applications in the radio, television, teleco.~ nirations~ and electronics industries. Hydrothermal 10 techniques have been used to grow high-perfection single crystals for these and other applications.
To s~rnm~rize the conventional process, a near-insoluble crystal nutrient or starting material is immersed in an aqueous solvent within a closed-volume, steel autoclave. The contents are super-heated, thereby exp~nrling the solvent to fill the 15 entire autoclave, ~l~S~uliGillg the cGIllen~, and inducing dissolution of the crystal nutrient in a first zone of the autoclave. A lenlpelalule gradient is applied toencourage convective flow of the nutrient-laden solution from the first zone to a second zone having a dirrel~n~ lelllpcldlule. The solution reaches its satuMtionpoint and the crystal nutrient precipi~les out in the second zone. Racks of seed20 crystals are usually provided in the second zone as nl-cle~tion points in order to minimi7l~ random self-nucleation of the ~ul~ie~l~. The reader is directed to theprior art on hydrothermal crystal appa~alus and methods for greater details thandisclosed in the following paragraphs. See, e.g., Sullivan, U.S. Patent 2,994,593 (Aug. 1, 1961); Kolb, U.S. Patent 3,271,114 (June 15, 1964); V.A. Kuznetsov 25 and A.N. Lobachev, "Hydrothermal Method for the Growth of Crystals", Soviet Physics--Crystallography, vol. 17, no. 4 (Jan.-Feb., 1973); R.A. T~ e, "HydrothPrm~l Synthesis of Crystals", Special Report, C&EN, Sept. 28, 1987, pp. 30-42.
Several factors affect the quality of hydroth~nn~lly grown crystals and the 30 ef~lciency of crystal production. They include~ ,ilies present in the starting materials or introduced into the solution by corrosion of the autoclave vessel and baffle; the quality of the seed crystals used for nll~le~tion; flow patterns of the dissolved nutrient within standard autoclave set-ups; baffle designs; and telllpel~-ture and pressure fluctuations affecting ullirollllity of growth rates. See, e.g., Balascio et al., "Factors Affecting the Quality and Perfection of HydrothermallyGrown Quartz", Proc. 34th Annual Symposium on Frequency Control, 65-71 (1980); Klipov et al., "Influence of Convective Flows on the Growth of SyntheticQuartz Crystalsn, Proc. 45th Ann. Symp. Freq. Control, 29-36 (1991); Johnson et al., "Experimental D~lellllhlalion of the Relationship among Baffle, TemperatureDirrelcnce and Power for the Hydrothermal Growth of Quart_", 43rd Ann. Symp.
Freq. Control, 447-458 (1989).
Various efforts have been directed at controlling these factors. For example, inert or noble metal linings have been proposed for reaction vessel walls, baffles, seed racks and seed clips. Such linings better with~t~n.l the solvent's corrosive effects and minimi7e formation of iron and other metal silicates, thereby reducing inclusions within the final crystals. Etched, dislocation-free seed may also be used on which to grow low-dislocation crystals for high-frequency applications. See, e.g., Barns et al., "Dislocation-free and low-dislocation quartz p,el)aled by hydrothermal cryst~lli7~tion", J. Crystal Growth 43, 676-686 (1978); Croxall et al., "Growth and Charac~e"~alion of High Purity Quartz", Proc. 36th Ann. Symp.
Freq. Control, 62-65 (1982); Armington et al., "The Growth of High Purity, Low Dislocation Quartzn, Proc. 38th Annual Symp. Freq. Control, 3-7 (1984).
Greater amounts of aqueous solution may be used in low-plessure hydrotht-rm~l crystal growth processes to produce high-quality crystals of silicon-free materials.
See, e.g., Caporaso et al., U.s. Patent 4,579,622 (Apr. 1, 1986).
Persons skilled in the art of hydrothermal crystal growth have also recognized that dissolved llullielll and solvent flow back and forth randomly, even turbulently, between dissolving and growth zones of an autoclave. This problem is inherent with the use of conventional baffles-flat perforated disks-which tend to promoterandom mixing rather than convection See, e.g., ~nn~m~l~i et al., "Effect of Convective Baffle & T ithil-m Nitrite and Lithium Nitrite Dopants on Hydrothermal Growth Rate of Quartz Single Crystalsn, 21 Indian J. Tech. 425-430 (Oct. 1983).
Random flow promotes ~aslerul nucleation of dissolved nutrient on autoclave walls and components, and the solvent's corrosion of these co",po"e,ll~ which are typically made of steel. As well, signifirant amounts of illl~uli~ies--including o 94128204 2 1 6 3 6 6 3 PCT/US94/0577~
iron or al~lminl~rn silicates and gas bubbles--acc~ te to form inclusions in thecrystals grown. Furthermore, crystal formation is non-uniform throughout the autoclave's growth zone, according to the influence of concentrative and convective flows. Klipov et al., Proc. 45th Ann. Symp. Freq. Control, 29-36 (1991).
~ nn~m~l~i et al. ~ cllcsed the desirability of a better mt~çh~ni~m of fluid flow within hydrothermal systems: i.e., convective fluid flow is ~l-,rell~d over random mixing of cooler and hotter fluids within a hydrothermal system. They discuss the merits of a "convection baffle" of their design in promoting convective flow, 10 but disclose no specific details of their baffle design. They experimented with adding syphons and e~lel1ding tubes to their baffle to --i--i---i7~' mixing at the fluid exchange boundary, but soon abandoned these fi~ s as significantly impeding flow rate. Ann~m~l~i, 21 Indian J. Tech. at 426, col. 2.
In U.S. Invention Reg. No. H580 (Feb. 7, 1989), "Method and Apparatus for 15 Growing High Perfection Quartz", Vig imposed "forced convection" on a hydro-thermal system to reduce crystal hllp~,~re~;lions and inclusions. A se~al~ filter vessel and pump are attached to a crystal growth autoclave to circulate solutionthrough the autoclave in one direction--from dissolving zone to growth zone to filter vessel back to dissolving zone--in a continuously recircul~ting pathway.
20 However, use of a second autoclave as a filter vessel complicates and lengthens the hydrothermal process, and adds significantly to the cost of hydrothermal crystal growth. The filter vessel increases the volume of the system, thereby making it more difficult to m~int~in constant pl~S~Ulc and to control zone ~elll~ res. Furthermore, forced convection tends to carry co.-l;....i.unt particles 25 along with the crystal nutrient solution, increasing the risk of crystal inclusions.
Vig's device provides a filter to remove co..~ nt particles from nutrient-depleted solution, but only after the dissolved lluLliclll and cont~min~nt~ havealready passed through the growth c~l~mher.
Therefore, an unfulfilled need remains for a simple, cost-effective way to 30 improve flow p~U~ s in conventional hydrolllellllal crystal growth apparatus,thereby improving crystal quality and the efficiency of crystal production such that wasteful crystal deposition is minimi7~d. There also remains a need for reducing 2 1 6 3 6 6 3 PCT/US94/0577~, the level of illlyùlities present in the llu~ ,nt-laden solution during crystal growth, which reduces the inclusion density and increases the degree of crystal perfection.
Summary of the Invention The present invention provides an inexpensive and simple means for improving flow of and filtering solution within processes such as hydrothermal crystal growth, thereby improving crystal quality and efficiency of crystal production.
Specifically, this invention can both filter and guide a flow of crystal nutrient-laden and -depleted solution optimally through a hydrothermal reaction vessel's dissolving and growth zones, thereby reducing crystal inclusions and flaws and avoiding wissLer~ll crystal deposition on the vessel walls. The filtering flow guide of this invention thereby produces high-purity, high-yelre~tion crystals and m~ximi7es efficiency of crystal production. Furthermore, the invention is easilyadapted to replace a conventional, prior art baffle, and to fit inside known hydrothermal autoclaves.
In one emobo~im~nt, the flow guide has a central inlet conduit and a plurality of tapering funnels sealably abutting each other and radially surrounding the inlet conduit. The flow guide's configuration allows convective flow of solution through the inlet conduit in one direction, and through the funnels in the otherdirection. The flow guide may be vertically positioned in a ~ndard hydrothermal reaction vessel or autoclave, with the funnels serving to separate the autoclave's dissolving and growth zones. Nutrient-laden solution flows through the central inlet conduit from the dissolving zone to the growth zone. Nutrient-depleted solution flows from the growth zone to the dissolving zone through each funnel.
In another emborlim~nt, a filter-cont~inin~ flow guide is provided wherein filters are disposed within the inlet and outlet conduits so as to trap or adsorb il-lyulilies from the crystal solution, while preserving continuous convective solution flow within a hydrotherrnal reaction vessel.
-Brief Des..ilJtion of the D~wi~
In the drawing:
Fig. 1 is a schematic representation of an hydrothermal crystal growth apparatus;
Fig. 2 is a cut-away, pel~ec~ e view of a filter-cont~ining flow guide of this invention placed within a conventional, cylindrical hydrothermal autoclave (not drawn to scale), with arrows inr1ic~ting a desired convectional flow pattern for the dissolved crystal;
Fig. 3 is a perspective view of the filter-cont~ining flow guide alone;
Fig. 4 is a cut-away perspective view of the filter-cont~ining flow guide;
Fig. 5 illustrates alternative embodiments of the flow guide, with Figs. 5(a) and (b) being pe~ye~ e views and Fig. 5(c) a top view of a flow guide having one central inlet conduit ~ulloullded by a plurality of funnels supported in a sealing collar;
Fig. 6 show (a) top and (b) side views of a flow guide having two inlet conduits ~ulloullded by a plurality of funnels supported in a sealing collar, and (c) top and (d) side views of the same further including filters; and Fig. 7(a) and (b) are longitll~lin~l, sectional views of two possible filter arrangements for a flow guide, drawn in SC~nl:~tic form and not to scale.
Desc~ ion of the Preferred F.mho,li.~
The filtering flow guide of this invention is designPd to prevent random or turbulent flow patterns of both crystal-laden and crystal-depleted solution between the dissolving and growth chambers of an hydrothermal reaction vessel and along the vessel's interior surfaces, and to filter out CO.~ .lc in the solution.
Fig. 1 shows a schematic of a conventional hydrothermal crystal growth apparatus, colll~lisillg a vertical autoclave or reaction vessel 12 contained within a furnace 10. The reaction vessel has two chambers or zones m~int~in~d at different le1~e1~lU~S by ~ull~ ding heater bands: a "dissolving zone" 13 and a "growth 30 zone" 14. The solubility of most crystals and their minerals increases with te~ )el~lule, so conventionally, the dissolving zone 13 is located at the bottom of the autoclave and is at a higher tell~el~lul~ than the growth zone 14 located at the WO 94/28204 2 1 6 3 6 6 3 PcTlus94los77s top of the autoclave. A prior art baffle 17--typically a perforated disk--is shown in Fig. 1 to separate the dissolving and growth chambers 13 and 14, for m~int~ining the tell~pel~u~ dir~ ial between those zones while permitting flow of solution between the dissolving and growth chambers. The reaction vessel 12 5 has an opening at the top of the growth zone 14, which is sealed shut by a sealing closure 15 after the reaction vessel 12 is filled with the apyropliate starting materials for the hydrothermal crystal growth process.
In the dissolving zone 13, a crystal lluLIielll 16 such as crushed quartz, is immersed in an aqueous solvent, such as a strongly basic solution of sodium 10 hydroxide or sodium carbonate. The solvent's starting volume is usually at least one-third of the reaction vessel 12, and may be varied according to the desired y~s~ule upon super-heating. The solvent is heated to suy~cliLical conditions, allowing it to expand to fill the vessel 12 and to dissolve the crystal l~uLIient supply 16. Hydrothermal conditions may be varied according to the desired 15 hydrothermal reaction or crystal product. For in.ct~nre, typical conditions for growing electronic grade quartz require reaction yles~ures of about 1000-2000 atm, and l~lllpeldtures of 325450C in the dissolving zone and 300400C in the growth zone (i.e., the latter is 25-100C cooler than the dissolving zone).
The crystal nutrient-laden solution flows upwardly from the hotter dissolving 20 zone 13 into the cooler growth zone 14, by natural or "buoyant" convection. The nutrient-laden solution becomes super-saturated in the cooler growth zone and excess crystal solute precipitates out of solution. Typically, racks of seed crystal 18, like c~-quartz, are provided as nl-cle~tion points, resulting in more orderly growth of single crystals. The cooled, nutrient-depleted solution then sinks back 25 down to the dissolving zone 13, where it reheats, dissolves more of the nutrient supply 16 and flows upward again. The hydrothermal cycle repeats itself until the nutrient supply 16 is exh~ te(l. The hydrothermal crystal growth process typically takes days to months to grow crystals suitable for commercial use.
In a few in~t~nreS in which a crystal's solubility decreases as lell~ye~lule 30 increases beyond a certain range, the positions of the dissolving and growth zones may be reversed. A cooler dissolving chamber which supports a nutrient supply would be located on top of a warmer growth chamber. The crystal nutrient-laden ~O 94l28204 2 1 6 3 6 6 3 PCT/US94/05775 -solution would flow convectively from the upper chamber down into the lower growth chamber where the llullitl,L would crystallize.
Fig. 2 shows a filter-cont~ining flow guide 20 of this invention, specifically adapted to fit inside a cylindrical hydrothermal autoclave or reaction vessel 12 in 5 which the crystal growth zone 14 lies atop a bottom dissolving zone 13. The flow guide 20 may be made of tempered steel or other suitable material for with-st~n-ling the lel~pelaLu~es, plCSsul~s, and corrosive conditions of the hydrothermal process. Inert or noble metals or nickel-based super-alloys may be used to make or to coat the flow guide 20 for even fewer crystal flaws.
Referring generally to Figs. 2-5, the flow guide 20 has at least one central inlet conduit 22 having a first opel~ing 23 and a second opening 26, the conduit's first opening 23 being within or proximate to the dissolving chamber when the flow guide is placed within a hydrothermal autoclave. The inlet conduit 22 may be fitted with an optional filter 27 colll~lising trapping material such as wire mesh or 15 steel wool, or suitable adsorbing material. Referring to the embodiments of Figs. 2 and 7(a), arrows 24 in~lir~te that crystal nutrient-laden solution flowsupward from the autoclave's dissolving zone 13, through the first opening 23, along the inlet conduit 22, out through the second opening 26 and filter 27, andinto the growth chamber 14. The filter 27 serves to trap trace illl~u~iLies such as 20 iron and al-lmin-lm silicates before the crystal nutrient-laden solution enters the growth chamber 14 where crystal growth occurs. Filtering out illll~uLiLies from the nutrient-laden solution reduces the amount of inclusions and dislocations in thefinal crystal product.
A plurality of outlet conduits--shown as outlet funnels 30 in Figs. 2-5--25 sealably abut each other and the inlet conduit 22 so as to ~ulloulld the inlet conduit radially. Optirnally, the outlet funnels 30 are fused together in a ring configura-tion similar to segments in half an orange, while each funnel connects to the inlet conduit 22 at or near the latter's first, inlet o~el"ng 23. Each funnel 30 preferably tapers from a first opening 39 to a second opening 40 having a smaller cross-30 sectional area than the funnel's first opening. In a most p,ef~lled embodiment, each funnel 30 is shaped subst~nti~lly like a hollow, inverted triangular pyramid whose apex is inverted to become the second opening 40 at a nadir of the funnel WO 94t28204 2 1 6 3 6 6 3 PCTIUS94/05775 30. That is, the outlet funnel 30 has two subst~nti~lly triangular lateral walls 32 with straight upper edges 31; a curved, subst~nti~lly triangular outer wall 34 with an oulw~rdly convex upper edge 33; and an inner wall 36 with a concave or inwardly curved upper edge 35 adjoining the inlet conduit 22. Each funnel 30 5 contiguously adjoins at least one adjacent funnel along the funnels' straight lateral upper edges 31, and adjoins the inlet conduit 22 at the funnel's innermost edge 35.
The funnels' outermost edges 33 together form a circle whose outer diameter is substantially equal to the reaction vessel's inner ~ llrl~ 1, thereby allowing the flow guide 20 to fit snugly within the reaction vessel 12.
Agains with ~ nce to Figs. 2-4, the funnel's second opening 40 may further open contiguously into an optional outlet tube 42 having a distal opening 44. The outlet tube 42 may further include an optional filter 46 proximate to the distalopening 44, to remove cont~min~nt particles from the llulliellt-depleted solution, including alllmin~m silicates, iron silir~tes, and other by-products of solvent 15 interactions with the vessel 12 or the flow guide 20.
For non-impeded flow, the cross-sectional area of the inlet conduit 22 preferably equals the sum of the cross-sectional areas of each funnel's narrowest point (e.g., the funnel's second opening 40) or, if present, of the outlet tubes 42.
The funnel walls are preferably angled steeply, nearly vertically. This arrange-20 ment permits a steady, non-random, non-mixing flow in the plefelled order:
(i) flow of crystal nutrient-laden solution through the inlet conduit 22 to the growth chamber 14; and (ii) flow of l~u~ielll-depleted solution through the funnels 30 and the outlet tubes 42, back into the dissolving zone 13. A most l)lefell~,dembo~lim~nt7 for use in standard hydrothermal autoclaves, has eight funnels 30 25 ~ulluunding the inlet conduit 22. An eight-funnel arrangement allows the funnel walls 32, 34, and 36 to be steeper than is possible with only four funnels covering the same autoclave volume. Making the funnel walls as steeply angled for just four funnels as for eight, results in funnels tending to be too bulky and intrusive for a standard, commercially available l.~/dro~.~,llllal autoclave, thereby tending to 30 impede flow excessively and to decrease crystal productivity.
Also shown in Fig. 2, a filtering means 50--such as wire mesh, steel wool, other filtering material, or çh~mir~l adsorbants--may be packed between the o 94/28204 2 1 6 3 6 6 3 PCT/US94/05775 funnels' outermost edges 33 and the vessel 12 to seal any space between the two, further reducing any random flow of solution between the dissolving and growth zones along the vessel walls and filtering out co~ ll;n~ from the solution.
In the most prerel,ed embodiment of Fig. 2, the heated l~uLlien~-rich solution flows tup through at least one central inlet conduit 22 through a central region of the growth zone 14--as inrlir~t~P~ by arrows 24--where it deposits the nutrientsonto racks of seed crystals 18. The cooled, nutrient-depleted solvent then flowsalong a peripheral region of the vessel 12 in the growth zone 14 to the dissolving zone 13 through the funnels 30 and outlets 42--as intlic~te~l by arrows 28. Uponthe filtered solvent's return to the dissolving chamber 13, it can reheat and further dissolve rern~ining crystal llullielll supply 16.
Various configurations for the flow guide 20 are possible. Although not illustrated, one embodiment of the flow guide may have subst~ntiAlly reverse configurations from those shown in Figs. 2-6, or be fitted upside-down in those hydrothermal a~pdld~uses having a growth zone at the bottom of the autoclave, with the crystal nutrient supply--e.g., a basket of lascas--suspended in an upper dissolving zone. The flow guide may also be adapted for horizontal use--e.g., ina hy~lroLl~llnal reaction vessel having the dissolving and growth zones side by side rather than atop each other and ol)eld~ g through forced convection.
AlLelnaLi~ely, as shown in Figs. 5(a)-(c), each outlet funnel 30 may have a subst~nti~lly conical shape with subst~nti~lly elliptical (e.g., circular) cross-sections as well as elliptical first and second opellings 39 and 40. It is plcfcll~d but not essential that the funnels 30 are contiguous with each other and with the inlet conduit 22. A plurality of the funnels 30, while m~int~ining their radial configuration around the inlet conduit 22, may be slightly spaced apart from each other and the inlet conduit, but a sealant or col-nP~;"g structure must then be disposed between the funnels and inlet conduit for support and to prevent randomflow. For in~t~nre, a plurality of the funnels 30 may fit contiguously within a circular collar 60 which, in turn, sealably surrounds the inlet conduit 22.
Fig. 5(a) shows the most pler~,lr~d longitudin~l relationship of the inlet conduit 22 to the outlet funnels 30, in which the inlet conduit's first opening 23 is proximate with each funnel's first opel~illg 39, such that both openings occur at the boundary Wo 94t28204 2 1 6 3 6 6 3 PCTtUSg4/05775 between the dissolving and growth zones when the flow guide 20 is placed within a hydrothermal reaction vessel. Alternatively, as in Fig. 5(b), the first opening 23 of the inlet conduit 22 may be positioned closer to the second openings 40 ofthe funnels 30, with the inlet conduit's first opening 23 protruding into the 5 dissolving zone of a hydrothermal reaction vessel in which the flow guide 20 is placed. However, the inlet conduit's and the funnels' first openings 23 and 40 are pl~efcllcd to coincide within the same cross-sectional plane (to be sitn~t~ at the boundary between the dissolving and growth zones), to minimi7P any dead-space occurring belweell the inlet conduit 22 and the funnels 30 which could trap fluid or 10 other material, or cause turbulence in solution flow from the dissolving to the growth zone.
Allc~ ively, Fig. 6(a)-(d) illustrates embo~lim~nt~ of the flow guide 20 providing more than one inlet conduit 22. Here, two inlet conduits 22 are centrally located within a radially ~ulloul~ding collar 60 supporting a plurality of 15 conical funnels 30. The cross-sectional area of each inlet conduit 22 should still exceed the individual cross-sectional area of each funnel's second opening 40; but the sum of the total inlet cross-sectional areas preferably remains subst~nti~lly equal to the sum of the total outlet cross-sectional areas.
Fig. 7(a)-(b) focuses on the filtering aspect of the invention, providing 20 longit~in~l, schematic views of simple embo(1im~nt~ of filter arrangements for a flow guide 20. An efficient filtering effect can be achieved even with outlet funnels 30 which are subst~nti~lly cylindrical tubes rather than tapering funnels, as long as the cross-sectional area of the inlet conduit 22 substantially equals the sum of the cross-sectional areas of the outlet funnels 30. Furthermore, various 25 arrangclllcll~s of filter-cont~ining inlet and outlet conduits are possible to provide a filtering flow guide. Cylindrical outlet conduits 30 may radially and sealably abut at least one cylindrical inlet conduit 22 and each other, as for the embodiments of Figs. 2-4, and Fig. 6(a). Al~cllla~ivcly, the relative positions of the outlet and inlet conduits could be lcvcl~ed as in Fig. 6(b). Even a side-by-side arrangement 30 is possible, wherein a single inlet conduit and a single outlet conduit each have, e.g., a semicircular cross-section, and sealably abutting each other so as to fit snugly within a cylindrical hydlotl,cllllal reaction vessel.
The hn~ll~nl factor--especially for a non-tapering flow guide em~d~ment a in Fig. 7--is to have the inlet conduit filter 27 spaced apart from the outlet funnel filters 46 along the flow guide's longih)~lin-q-l axis, to mqintqin directed convective flow while achieving effective filtration. Most preferably, the filter 27 may bedisposed proximate to the inlet conduit's second opel~g 26, at a lon~it~ inql tqnl~e from the filters 46 disposed near the second o~nings 40 of the funnels 30, as shown in Fig. 7(a). When this filter arrangement is placed within a hydlo~ reaction vessel 12, the filter 27 would be sih~qt~d proximate with the growth zone 14 while the filter 46 would be proximate with the dissolving zone 13. Due to the dirÇ~"elllial flow ~c~ e re~lltin~ from the spaced-apart a~ ge~ ,.ll of the filters 27 and 46 in a non-la~.ing flow guide 20, crystal llullie.ll-laden solution would tend to flow through the vessel's center from the dissolving to the growth zone, while crystal-depleted solution would tend to flow along the vessel's peli~ from the growth to the dissolvhg zone.
Refelling to Fig. 7(b), it is also possible to reverse t~,e relative positions of the inlet and outlet conduit filters in the non-lapelillg flow guide 20, so as to promote an opposi~ flow direction. A plurality of p~ l inlet cori.lui~ 22' sealably and radially abut at least one central outlet conduit 30'having a first o~ning 39' and a second o~nillg 40'. A filter 46' is posilioll~d within the central outlet tube 30' plo~ e to the second opening 40'. A filter 27' is posiliol~ within each peliphelal inlet tube 22' having a first o~nil~g 23' and a second opening 26', the filter 27' proximate to the second o~ning 2C'. By placing a flow guide having this filter a~ in a l~dr~elll.al reaction vessel 12, one can promote coll~ , flow of solution from the dissolving zone 13 to the growth zone 14 through the ~~ }~lal inlet tube 22' along the vessel's ~liphel~ (arrows 24') and then past the crystal seed racks 18. Solution would flow from the growth zone 14 back to the dissolving zone 13 through the centrally located outlet conduit 30' in the vessel's center (arrows 28').
Of course, both filt~q,tion and coll~ i./e flow effects are mq~i..li,~cl in the 30 most p.efell~d embodiment of the present filter-con~ g flow guide 20, shown in Figs. 24. In ~ , the entire configuration of the pr~f~ .d flow guide's inlet conduit 22, funnels 30, and outlet tubes 42--both with and without the help AMENDED SltEEr 21 63663 PCTi'j~ 94/05775 IPEA/U~ 2 ~ SEP ~^n5 of the filters 27 and 4fi helps to guide the convection ~;urle~ from the dissolving zone 13 into the growth zone 14 upward (arrows 24) through the center of the reaction vessel's interior, then back down (arrows 28) along the pe.il)hel~ of the vessel's interior to the dissolving ch~mber 13. The flow guide promotes well-S defined, recirc~ tin~ flow pall~,lllS within the growth and dissolving zones. Thisflow pattern results in more even crystal growth and a more ul~irollll growth rate throughout the reaction vessel. Improved crystal quality is obtained with filters by reducing the inclusion or im~ y density.
The flow guide of the present invention has been tested in conventional 10 hydloLlle.~l growth of clecLlvl~ic-grade quartz crystals at high ~les~ules and lelll~laLul~s, ~u~ lly as ~ u3secl previously. The present invention greatly improves the quality of crystals grown in conventional l~dfoLll~.lllal autoclaves.
Table 1 COI~)~S the inclusion ~ nc~ s of ele.,Llonic-grade a-quartz grown with and without the filter-co.~ ;ng flow guide 20.
D A~er~ge ~ ' Den~ Worst~ e 1 ' Density(no. of ' 'cm3) (no. of ' 'cm3) >100 micron,without flow guide ` 0.1 0.9 with flow guide 0.001 0.01 70-100 micron, without flow guide0.8 2.5 with flow guide 0.01 0.2 2530-70 micron, without flow guide 1.5 3.6 with flow guide 0.3 0.6 Analysis by sc~l~n;n~ electron Illicr~scope (SEM) showed that a-quartz grown with this il~ ion had sigl~;r~r~ y leluced ~mollnt~ of inrll.~ ons e.g., acmite (NaFe(SiO3)2) and e~ h.).;le (Li2Na4Fe2Sil2030)--as cOlll~al~l to crystals 35 grown without the present filtering flow guide. For example, the average density tr~--~T
O 94/28204 PCT/US94/0577~
of inclusions larger than 100 microns was 100 times less in crystals grown with the present filtering flow guide, than in crystals grown with conventional baffles.
At the same time, use of the present filtering flow guide 20 m~int~in~ substantially the same crystal growth rate and flow velocities as hydrothermal crystal growth 5 methods using standard perforated disk baffles. However, the flow guide 20 minimi71oS useless and wasteful cryst~lli7~tion along the reaction vessel walls, since the flow patterns promoted by the flow guide cause the llullielll-depleted solution to return along the vessel walls, which can dissolve any crystal deposits on thewalls. Moreover, the flow guide has been observed to reduce corrosion of the 10 reaction vessel, as compared to conventional baffles. Analysis of residues--on and within the flow guide, and on the autoclave's bottom--show that small, unavoidable amounts of illll~ufilies (e.g., acmite, em~lel~site) do occur, but are largely collected on the flow guide and its filters. Finally, this invention further improves over the prior art in that it is easily adapted to fit into standard crystal 15 growth appalalus and elimin~tPs the need for any other baffle, filter, or pump.
Further embodiments of the invention will be a~,al~ to those skilled in the art from a consideration of this specification or the practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with the true scope and spirit of the invention being intlic~t 20 by the following claims.
What is claimed is the following:
Claims (50)
1. A flow guide, comprising:
(a) at least one inlet conduit having a first opening and a second opening;
and (b) a plurality of funnels surrounding the at least one inlet conduit radially, each funnel tapering from a first opening to a second opening, a cross-sectionalarea of the funnel's first opening being greater than a cross-sectional area of the second opening, and each funnel sealably abutting at least one adjacent funnel and the at least one inlet conduit.
(a) at least one inlet conduit having a first opening and a second opening;
and (b) a plurality of funnels surrounding the at least one inlet conduit radially, each funnel tapering from a first opening to a second opening, a cross-sectionalarea of the funnel's first opening being greater than a cross-sectional area of the second opening, and each funnel sealably abutting at least one adjacent funnel and the at least one inlet conduit.
2. The flow guide of claim 1 wherein a narrowest cross-sectional area of the at least one inlet conduit substantially equals a sum total of each funnel's narrowest cross-sectional area.
3. A flow guide adapted for use in a hydrothermal crystal growth reaction vessel, comprising:
(a) at least one inlet conduit having a first opening and a second opening, the inlet conduit positioned centrally within a hydrothermal reaction vessel;
(b) a plurality of funnels surrounding the at least one inlet conduit radially, each funnel having a first opening and a second opening, a cross-sectional area of the funnel's first opening being greater than a cross-sectional area of the second opening, and each funnel sealably abutting at least one adjacent funnel and the at least one inlet conduit;
wherein the plurality of funnels separates a dissolving zone from a growth zone of the hydrothermal reaction vessel;
whereby a plurality differential between the dissolving zone and the growth zone induces flow of a crystal nutrient-laden solution from the dissolving zone through the inlet conduit into the growth zone, and crystal nutrient-depleted solution flows from the growth zone through each of the funnels and into the dissolving zone.
(a) at least one inlet conduit having a first opening and a second opening, the inlet conduit positioned centrally within a hydrothermal reaction vessel;
(b) a plurality of funnels surrounding the at least one inlet conduit radially, each funnel having a first opening and a second opening, a cross-sectional area of the funnel's first opening being greater than a cross-sectional area of the second opening, and each funnel sealably abutting at least one adjacent funnel and the at least one inlet conduit;
wherein the plurality of funnels separates a dissolving zone from a growth zone of the hydrothermal reaction vessel;
whereby a plurality differential between the dissolving zone and the growth zone induces flow of a crystal nutrient-laden solution from the dissolving zone through the inlet conduit into the growth zone, and crystal nutrient-depleted solution flows from the growth zone through each of the funnels and into the dissolving zone.
4. The flow guide of claim 3, wherein a narrowest cross-sectional area of the at least one inlet conduit substantially equals a sum total of each funnel'snarrowest cross-sectional area.
5. The flow guide of claim 1, 2, 3 or 4, wherein the plurality of funnels are supported within a collar, each funnel's first opening contiguous with the collar, and the collar sealably abutting and radially surrounding the at least one inletconduit.
6. The flow guide of claim 1, 2, 3 or 4, further comprising:
(c) a filter disposed within the inlet conduit, whereby impurities are trapped from solution flowing through the inlet conduit; and (d) a filter disposed within each funnel, whereby impurities are trapped from solution flowing through each funnel.
(c) a filter disposed within the inlet conduit, whereby impurities are trapped from solution flowing through the inlet conduit; and (d) a filter disposed within each funnel, whereby impurities are trapped from solution flowing through each funnel.
7. The flow guide of claim 6, wherein the plurality of funnels are supported within a collar, each funnel's first opening contiguous with the collar, and thecollar sealably abutting and radially surrounding the at least one inlet conduit.
8. The flow guide of claim 1, 2, 3 or 4, further including, at each funnel, an outlet tube having a first opening and a second opening, the first opening of the outlet tube contiguous with the second opening of the funnel.
9. The flow guide of claim 8, further comprising:
(c) a filter disposed within the at least one inlet conduit, whereby impurities are trapped from solution flowing through the inlet conduit; and (d) a filter disposed within the outlet tube, whereby impurities are trapped from solution flowing through the outlet tube.
(c) a filter disposed within the at least one inlet conduit, whereby impurities are trapped from solution flowing through the inlet conduit; and (d) a filter disposed within the outlet tube, whereby impurities are trapped from solution flowing through the outlet tube.
10. The flow guide of claim 9, wherein a narrowest cross-sectional area of the inlet conduit substantially equals a sum total of each outlet tube's narrowest cross-sectional area.
11. The flow guide of claim 1, 2, 3, or 4, wherein the inlet opening of the at least one inlet conduit is proximate to each funnel's first opening.
12. The flow guide of claim 1, 2, 3, or 4, wherein the first opening of the inlet conduit is proximate to each funnel's second opening along a longitudinal axis of the flow guide.
13. The flow guide of claim 8, wherein the first opening of the inlet conduit is proximate to each outlet tube's second opening along a longitudinal axis of the flow guide.
14. The flow guide of claim 1, 2, 3, or 4, wherein the inlet conduit has a substantially elliptical cross-section and walls angled at less than twenty degrees from a longitudinal axis of the inlet conduit.
15. The flow guide of claim 8, wherein the inlet conduit has a substantially elliptical cross-section and walls angled at less than twenty degrees from a longitudinal axis of the inlet conduit.
16. The flow guide of claim 1, 2, 3, or 4, wherein each funnel is substantially configured as a hollow, inverted pyramid, the funnel's second opening located at a nadir of the inverted pyramid.
17. The flow guide of claim 8, wherein each funnel is substantially configured as a hollow, inverted pyramid, the funnel's second opening located at a nadir of the inverted pyramid.
18. The flow guide of claim 1, 2, 3, or 4, wherein each funnel comprises:
(a) a curved innermost wall having a curved upper edge which abuts and is contiguous with the inlet conduit;
(b) two substantially triangular lateral walls, each lateral wall substantially contiguous with the lateral wall of an adjacent funnel; and (c) a substantially triangular, curved outermost wall having a curved upper edge;
wherein the innermost and outermost walls are substantially parallel to each other and intersect the two lateral walls.
(a) a curved innermost wall having a curved upper edge which abuts and is contiguous with the inlet conduit;
(b) two substantially triangular lateral walls, each lateral wall substantially contiguous with the lateral wall of an adjacent funnel; and (c) a substantially triangular, curved outermost wall having a curved upper edge;
wherein the innermost and outermost walls are substantially parallel to each other and intersect the two lateral walls.
19. The flow guide of claim 18, further including:
(i) at each funnel, an outlet tube having a first opening and a second opening, the first opening of the outlet tube contiguous with the second opening of each funnel;
(ii) a filter disposed within the at least one inlet conduit, whereby impuritiesare trapped from solution flowing through the inlet conduit; and (iii) a filter disposed within each outlet tube, whereby impurities are trapped from solution flowing through the outlet tube.
(i) at each funnel, an outlet tube having a first opening and a second opening, the first opening of the outlet tube contiguous with the second opening of each funnel;
(ii) a filter disposed within the at least one inlet conduit, whereby impuritiesare trapped from solution flowing through the inlet conduit; and (iii) a filter disposed within each outlet tube, whereby impurities are trapped from solution flowing through the outlet tube.
20. A filtering flow guide, comprising:
(a) at least one inlet conduit having a first opening and a second opening, a filter disposed within the at least one inlet conduit; and (b) at least one outlet conduit having a first opening and a second opening, a filter disposed within the at least one outlet conduit, the at least one outlet conduit sealably abutting the inlet conduit;
wherein the inlet conduit filter is spaced apart from the outlet conduit filter along a longitudinal axis of the flow guide.
(a) at least one inlet conduit having a first opening and a second opening, a filter disposed within the at least one inlet conduit; and (b) at least one outlet conduit having a first opening and a second opening, a filter disposed within the at least one outlet conduit, the at least one outlet conduit sealably abutting the inlet conduit;
wherein the inlet conduit filter is spaced apart from the outlet conduit filter along a longitudinal axis of the flow guide.
21. The flow guide of claim 20, wherein the inlet conduit filter is disposed proximate to the second opening of the at least one inlet conduit, and the outlet conduit filter is disposed proximate to the second opening of the at least one outlet conduit.
22. The flow guide of claim 20, including a plurality of outlet conduits radially surrounding the at least one inlet conduit, it each outlet conduit sealably abutting at least one adjacent outlet conduit and the at least one inlet conduit.
23. The flow guide of claim 20, including a plurality of inlet conduits radiallysurrounding the at least one outlet conduit, each inlet conduit sealably abutting at least one adjacent inlet conduit and the at least one outlet conduit.
24. The flow guide of claim 20, 21, 22, or 23, wherein a total, narrowest cross-sectional area of the at least one inlet conduit substantially equals a total, narrowest cross-sectional area of the at least one outlet conduit.
25. A method for improving a hydrothermal crystal growth reaction, comprising the steps of:
(a) providing at least on inlet conduit having a first opening and a second opening within a hydrothermal reaction vessel for guiding solution flow from a dissolving zone to a growth zone of the reaction vessel through a central interior of the reaction vessel; and (b) providing a plurality of funnels within the hydrothermal reaction vessel for guiding solution flow from the growth zone to the dissolving zone through a peripheral interior of the reaction vessel, each funnel tapering from a first opening to a second opening, a cross-sectional area of the funnel's first opening being greater than the second opening's cross-sectional area, and each funnel sealablyabutting at least one adjacent funnel and the inlet conduit so as to surround the inlet conduit radially..
(a) providing at least on inlet conduit having a first opening and a second opening within a hydrothermal reaction vessel for guiding solution flow from a dissolving zone to a growth zone of the reaction vessel through a central interior of the reaction vessel; and (b) providing a plurality of funnels within the hydrothermal reaction vessel for guiding solution flow from the growth zone to the dissolving zone through a peripheral interior of the reaction vessel, each funnel tapering from a first opening to a second opening, a cross-sectional area of the funnel's first opening being greater than the second opening's cross-sectional area, and each funnel sealablyabutting at least one adjacent funnel and the inlet conduit so as to surround the inlet conduit radially..
26. The method of claim 25, further comprising the step of:
(c) providing a solution-filtering means within the hydrothermal reaction vessel at a boundary between the dissolving and growth zones of the reaction vessel.
(c) providing a solution-filtering means within the hydrothermal reaction vessel at a boundary between the dissolving and growth zones of the reaction vessel.
27. Cancelled.
28. A hydrothermal crystal growth apparatus, comprising:
a hydrothermal reaction vessel comprising: a dissolving zone adapted to hold a crystal nutrient supply and a starting volume of crystal-dissolving solution; a growth zone contiguous with the dissolving zone, the growth zone adapted to support at least one starting seed crystal and a final crystal growth product; asealable opening at one end of the hydrothermal reaction vessel; and a sealing closure adapted to fit the sealable opening;
controllable heaters surrounding the hydrothermal reaction vessel, for heating and maintaining the dissolving and growth zones at adjustably different temperatures; and a flow guide of claim 1, 2, 3, 4, 20, or 21, fitting within the hydrothermal reaction vessel at an interface between the dissolving zone and growth zone, so that a perimeter of the flow guide sealably abuts an interior surface of the reaction vessel.
a hydrothermal reaction vessel comprising: a dissolving zone adapted to hold a crystal nutrient supply and a starting volume of crystal-dissolving solution; a growth zone contiguous with the dissolving zone, the growth zone adapted to support at least one starting seed crystal and a final crystal growth product; asealable opening at one end of the hydrothermal reaction vessel; and a sealing closure adapted to fit the sealable opening;
controllable heaters surrounding the hydrothermal reaction vessel, for heating and maintaining the dissolving and growth zones at adjustably different temperatures; and a flow guide of claim 1, 2, 3, 4, 20, or 21, fitting within the hydrothermal reaction vessel at an interface between the dissolving zone and growth zone, so that a perimeter of the flow guide sealably abuts an interior surface of the reaction vessel.
29. An hydrothermal crystal growth apparatus, comprising:
a hydrothermal reaction vessel including: a dissolving zone adapted to hold a crystal nutrient n supply and a starting volume of crystal-dissolving solution; a growth zone contiguously connected to the dissolving zone, the growth zone adapted to support at least one starting seed crystal and a final crystal growthproduct; a sealable opening at one end of the hydrothermal reaction vessel; and a sealing closure adapted to fit the sealable opening;
controllable heaters surrounding the hydrothermal reaction vessel, for heating and maintaining the dissolving and growth zones at adjustably different temperatures; and a flow guide of claim 8, fitting within the hydrothermal reaction vessel at an interface between the dissolving zone and the growth zone, so that a perimeter of the flow guide sealably abuts an interior surface of the reaction vessel.
a hydrothermal reaction vessel including: a dissolving zone adapted to hold a crystal nutrient n supply and a starting volume of crystal-dissolving solution; a growth zone contiguously connected to the dissolving zone, the growth zone adapted to support at least one starting seed crystal and a final crystal growthproduct; a sealable opening at one end of the hydrothermal reaction vessel; and a sealing closure adapted to fit the sealable opening;
controllable heaters surrounding the hydrothermal reaction vessel, for heating and maintaining the dissolving and growth zones at adjustably different temperatures; and a flow guide of claim 8, fitting within the hydrothermal reaction vessel at an interface between the dissolving zone and the growth zone, so that a perimeter of the flow guide sealably abuts an interior surface of the reaction vessel.
30. An improved hydrothermal crystal growth apparatus, comprising:
a hydrothermal reaction vessel including: a dissolving zone adapted to hold a crystal nutrient supply and a starting volume of crystal-dissolving solution; a growth zone contiguously connected to the dissolving zone, the growth zone adapted to support at least one starting seed crystal and a final crystal growth product; a sealable opening at one end of the hydrothermal reaction vessel; and a sealing closure adapted to fit the sealable opening;
controllable heaters surrounding the hydrothermal reaction vessel, for heating and maintaining the dissolving and growth zones at adjustably different temperatures; and a flow guide of claim 9, fitting within the hydrothermal reaction vessel at an interface between the dissolving zone and the growth zone, so that a perimeter of the flow guide sealably abuts an interior surface of the reaction vessel.
a hydrothermal reaction vessel including: a dissolving zone adapted to hold a crystal nutrient supply and a starting volume of crystal-dissolving solution; a growth zone contiguously connected to the dissolving zone, the growth zone adapted to support at least one starting seed crystal and a final crystal growth product; a sealable opening at one end of the hydrothermal reaction vessel; and a sealing closure adapted to fit the sealable opening;
controllable heaters surrounding the hydrothermal reaction vessel, for heating and maintaining the dissolving and growth zones at adjustably different temperatures; and a flow guide of claim 9, fitting within the hydrothermal reaction vessel at an interface between the dissolving zone and the growth zone, so that a perimeter of the flow guide sealably abuts an interior surface of the reaction vessel.
31. The hydrothermal crystal growth apparatus of claim 28, further comprising a sealing means adapted to fit between the flow guide and the interior surface of the reaction vessel.
32. The hydrothermal crystal growth apparatus of claim 31, wherein the sealing means is wire mesh.
33. The hydrothermal crystal growth apparatus of claim 31, wherein the sealing means is steel wool.
34. The hydrothermal crystal growth apparatus of claim 30, further comprising a sealing means adapted to fit between the flow guide and the interior surface of the reaction vessel.
35. The hydrothermal crystal growth apparatus of claim 34, wherein the sealing means is wire mesh.
36. The hydrothermal crystal growth apparatus of claim 34, wherein the sealing means is steel wool.
37. The flow guide of claim 20, wherein the inlet conduit filter is disposed proximate to the second opening of the at least one inlet conduit, and the outlet conduit filter is disposed proximate to the second opening of the least one outlet conduit.
38. The flow guide of claim 20 or 37, wherein a cross-sectional area of the inlet conduit substantially equals the sum of cross-sectional areas of the outlet conduits.
39. The flow guide of claim 20 or 37, wherein a cross-sectional area of the outlet conduit substantially equals the sum of cross-sectional areas of the inlet conduits.
40. A flow guide, comprising:
(a) at least one substantially cylindrical inlet conduit having a first opening and a second opening; and (b) a plurality of substantially cylindrical outlet conduits surrounding the at least one inlet conduit radially, each outlet conduit having a first opening and a second opening, and each outlet conduit sealably abutting at least one adjacent outlet conduit and the at least one inlet conduit.
(a) at least one substantially cylindrical inlet conduit having a first opening and a second opening; and (b) a plurality of substantially cylindrical outlet conduits surrounding the at least one inlet conduit radially, each outlet conduit having a first opening and a second opening, and each outlet conduit sealably abutting at least one adjacent outlet conduit and the at least one inlet conduit.
41. The flow guide of claim 40, wherein a cross-sectional area of the at least one inlet conduit substantially equals a sum total of cross-sectional areas of the outlet conduits.
42. A flow guide adapted for use in a hydrothermal crystal growth reaction vessel having dissolving and growth zones, the flow guide comprising:
(a) at least one substantially cylindrical inlet conduit having a first opening and a second opening, a filter disposed within the at least one inlet conduit; and (b) a plurality of substantially cylindrical outlet conduits surrounding the at least one inlet conduit radially, each outlet conduit having a first opening and a second opening, a filter disposed within each of the outlet conduits, and each outlet conduit sealably abutting at least one adjacent outlet conduit and the at least one inlet conduit;
wherein the inlet conduit filter is spaced apart from the outlet conduit filtersalong a longitudinal axis of the flow guide;
whereby crystal nutrient-laden solution flows from the dissolving zone into the growth zone, and crystal nutrient-depleted solution flows from the growth zone into the dissolving zone.
(a) at least one substantially cylindrical inlet conduit having a first opening and a second opening, a filter disposed within the at least one inlet conduit; and (b) a plurality of substantially cylindrical outlet conduits surrounding the at least one inlet conduit radially, each outlet conduit having a first opening and a second opening, a filter disposed within each of the outlet conduits, and each outlet conduit sealably abutting at least one adjacent outlet conduit and the at least one inlet conduit;
wherein the inlet conduit filter is spaced apart from the outlet conduit filtersalong a longitudinal axis of the flow guide;
whereby crystal nutrient-laden solution flows from the dissolving zone into the growth zone, and crystal nutrient-depleted solution flows from the growth zone into the dissolving zone.
43. The flow guide of claim 42, wherein the inlet conduit filter is disposed proximate to the second opening of the at least one inlet conduit, and the outlet conduit filters are disposed proximate to each of the second openings of the outlet conduits.
44. The flow guide of claim 42 or 43, wherein a cross-sectional area of the inlet conduit substantially equals the sum of cross-sectional areas of the outlet conduits.
45. A hydrothermal crystal growth apparatus, comprising:
a hydrothermal reaction vessel comprising: a dissolving zone adapted to hold a crystal nutrient supply and a starting volume of crystal-dissolving solution; a growth zone contiguous with the dissolving zone, the growth zone adapted to support at least one starting seed crystal and a final crystal growth product; asealable opening at one end of the hydrothermal reaction vessel; and a sealing closure adapted to fit the sealable opening;
controllable heaters surrounding the hydrothermal reaction vessel, for heating and maintaining the dissolving and growth zones at adjustably different temperatures; and a flow guide fitting within the hydrothermal reaction vessel at an interface between the dissolving zone and growth zone, so that a perimeter of the flow guide sealably abuts an interior surface of the reaction vessel, the flow guide comprising:
(a) at least one inlet conduit having a first opening and a second opening, a filter disposed within the at least one inlet conduit; and -21/a-(b) at least one outlet conduit having a first opening and a second opening, a filter disposed within the at least one outlet conduit, the at least one outlet conduit sealably abutting the inlet conduit;
wherein the inlet conduit filter is spaced apart from the outlet conduit filter along a longitudinal axis of the flow guide; and whereby crystal nutrient-laden solution flows from the dissolving zone into the growth zone, and crystal nutrient-depleted solution flows from the growth zone and into the dissolving zone.
a hydrothermal reaction vessel comprising: a dissolving zone adapted to hold a crystal nutrient supply and a starting volume of crystal-dissolving solution; a growth zone contiguous with the dissolving zone, the growth zone adapted to support at least one starting seed crystal and a final crystal growth product; asealable opening at one end of the hydrothermal reaction vessel; and a sealing closure adapted to fit the sealable opening;
controllable heaters surrounding the hydrothermal reaction vessel, for heating and maintaining the dissolving and growth zones at adjustably different temperatures; and a flow guide fitting within the hydrothermal reaction vessel at an interface between the dissolving zone and growth zone, so that a perimeter of the flow guide sealably abuts an interior surface of the reaction vessel, the flow guide comprising:
(a) at least one inlet conduit having a first opening and a second opening, a filter disposed within the at least one inlet conduit; and -21/a-(b) at least one outlet conduit having a first opening and a second opening, a filter disposed within the at least one outlet conduit, the at least one outlet conduit sealably abutting the inlet conduit;
wherein the inlet conduit filter is spaced apart from the outlet conduit filter along a longitudinal axis of the flow guide; and whereby crystal nutrient-laden solution flows from the dissolving zone into the growth zone, and crystal nutrient-depleted solution flows from the growth zone and into the dissolving zone.
46. The apparatus of claim 45, wherein the inlet conduit filter is disposed proximate to the second opening of the at least one inlet conduit, and the outlet conduit filter is disposed proximate to the second opening of the least one outlet conduit.
47. The apparatus of claim 45 or 46, wherein the at least one inlet conduit is positioned centrally within the flow guide and wherein the at least one outlet conduit is positioned adjacent to a peripheral surface of the hydrothermal crystal growth reaction vessel.
48. The apparatus of claim 47, wherein a cross-sectional area of the inlet conduit substantially equals the sum of cross-sectional areas of the outlet conduits.
49. The apparatus of claim 45 or 46, wherein the at least one inlet conduit is positioned adjacent to a peripheral surface of the hydrothermal crystal growth reaction vessel and wherein the at least one outlet conduit is positioned centrally within the flow guide.
50. The apparatus of claim 49, wherein a cross-sectional area of the outlet conduit substantially equals the sum of cross-sectional areas of the inlet conduits.
-21/b-
-21/b-
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US08/069,040 US5456204A (en) | 1993-05-28 | 1993-05-28 | Filtering flow guide for hydrothermal crystal growth |
| US08/069,040 | 1993-05-28 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2163663A1 true CA2163663A1 (en) | 1994-12-08 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002163663A Abandoned CA2163663A1 (en) | 1993-05-28 | 1994-05-23 | Filtering flow guide for hydrothermal crystal growth |
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| US (1) | US5456204A (en) |
| EP (1) | EP0731855A1 (en) |
| JP (1) | JPH09508093A (en) |
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| WO (1) | WO1994028204A1 (en) |
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| US4579622A (en) * | 1983-10-17 | 1986-04-01 | At&T Bell Laboratories | Hydrothermal crystal growth processes |
| US4654111A (en) * | 1985-12-02 | 1987-03-31 | At&T Laboratories | Hydrothermal growth of potassium titanyl phosphate |
| USH580H (en) * | 1987-07-16 | 1989-02-07 | The United States Of America As Represented By The Secretary Of The Army | Method and apparatus for growing high perfection quartz |
| JP2961560B2 (en) * | 1990-09-25 | 1999-10-12 | 東洋通信機株式会社 | In-cylinder convection controller for hydrothermal growth of crystal |
-
1993
- 1993-05-28 US US08/069,040 patent/US5456204A/en not_active Expired - Fee Related
-
1994
- 1994-05-23 CA CA002163663A patent/CA2163663A1/en not_active Abandoned
- 1994-05-23 WO PCT/US1994/005775 patent/WO1994028204A1/en not_active Application Discontinuation
- 1994-05-23 JP JP7500868A patent/JPH09508093A/en active Pending
- 1994-05-23 EP EP94918657A patent/EP0731855A1/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| JPH09508093A (en) | 1997-08-19 |
| EP0731855A1 (en) | 1996-09-18 |
| US5456204A (en) | 1995-10-10 |
| WO1994028204A1 (en) | 1994-12-08 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Discontinued |