An apparatus and method for growing crystals in solution using a reversible shear flow

Abstract

The application discloses a device and method for growing crystals in solution by using reversible shear flow, relates to the technical field of artificial crystal growth, and comprises a growth solution pool, solution pipes arranged on the two sides of the growth solution pool, a pump arranged at the connecting position of the growth solution pool and the solution pipes, a movable supporting table mechanism, shear flow channels arranged above the supporting table mechanism and connected with the solution pipes at both ends, and isolation covers arranged on the four side surfaces of the supporting table mechanism. The application can realize the "reversible shear flow" in the whole crystal surface formation theory, is suitable for crystals with different diameters ranging from several centimeters to tens of centimeters, and can minimize the crystal cracking problem caused by mechanical movement, since the crystals are fixed on the crystal supporting table and do not move in the solution.

Description

Technical Field

[0001] This invention relates to the field of artificial crystal growth technology, specifically to an apparatus and method for growing crystals in solution using reversible shear flow. Background Technology

[0002] Solution crystal growth is an important method for preparing crystalline materials and is currently the only method for growing large-aperture nonlinear optical crystals. During solution crystal growth, convective mass transport is a crucial step, directly affecting the growth rate and quality of the crystal. Convection can significantly improve mass transport at the crystal / liquid interface, resulting in an order-of-magnitude increase in the crystal growth rate. [1] On the other hand, convection can induce defects in the contents. [2] This causes a decrease in the performance or lifespan of the crystal. [3] In actual crystal growth, forced convection generated by relative movement of the crystal to enhance mass transfer at the growth interface is one of the necessary measures to achieve rapid crystal growth. The rotating crystal method, which involves rotating the crystal forward, stopping, and reversing its direction during growth, is the most widely used crystal movement method. However, this method results in stagnant regions facing the liquid flow and convection vortex regions facing away from the liquid flow on the crystal surface, which can significantly reduce the quality of the grown crystal. Designing a crystal growth method that can fully utilize the enhanced mass transfer effect of convection while avoiding its adverse effects is key to rapidly growing high-quality crystals.

[0003] Solution crystal growth is a process in which adjacent steps spread across crystal faces, forming layer upon layer of crystal faces. Numerous studies have shown that the impact of convection on crystal growth quality essentially stems from the influence of convective mass transport on the morphological stability of crystal faces. Morphological instability of crystal faces induces the formation of liquid inclusions, ultimately leading to a decrease in crystal quality. [4] Theoretical analysis shows that [5] "Reversible shear flow" (parallel to the crystal plane and capable of immediate 180-degree reversal) can maintain the stability of the crystal plane morphology. If this theory is combined with the actual crystal growth process to create an ideal "reversible shear flow" during growth, theoretically, it is possible to grow crystals of extremely high quality while ensuring the crystal growth rate.

[0004] This invention starts by regulating the convective mass transfer process during crystal growth. Through a specially designed solution supply method, a theoretically "reversible shear flow" is formed at the crystal / liquid interface to achieve the growth of high-quality crystals.

[0005] Patent application CN103060888A discloses a method for growing crystals in a solution with three-dimensional crystal movement. It proposes a crystal growth method with special crystal movement, which can improve the uniformity of solute distribution on the crystal surface and is beneficial to the improvement of crystal quality to a certain extent. However, it cannot form a "reversible shear flow". Due to the use of a crystal rod for fixation, it is not suitable for the growth of large-diameter crystals.

[0006] Patent application CN113604882A discloses a method for growing KDP-type crystals using alternating flow solutions. It proposes forming alternating flows near the crystal surface through jetting to facilitate rapid, high-quality growth of KDP crystals. While this method can partially achieve alternating flow in the region near the nozzles, it cannot achieve full coverage across the entire crystal surface. Furthermore, it requires the arrangement of dozens or even hundreds of small-diameter nozzles during application, leading to problems such as uneven nozzle flow and nozzle clogging.

[0007] Based on previous research, this invention proposes to utilize narrow slits to form high-speed shear flow on the crystal plane, and at the same time, by periodically changing the flow direction, to finally achieve the "reversible shear flow" that is most conducive to crystal growth in the crystal plane formation theory, thereby realizing the rapid growth of high-quality crystals.

[0008] [1].Wilcox W R.Influence of convection on the growth of crystals fromsolution[J].Journal of Crystal Growth,1983,65(1-3):133-142.

[0009] [2].Vekilov PG, Alexander J ID, Rosenberger F.Nonlinear response oflayer growth dynamics in the mixed kinetics-bulk-transport regime[J].PhysicalReview E,1996,54(6):6650.

[0010] [3].Woods BW,Runkel MJ,Yan M,et al.Investigations of laser damage in KDP using light-scattering techniques[C] / / Laser-Induced Damage in OpticalMaterials:1996.International Society for Optics and Photonics,1997,2966:20-31.

[0011] [4].Van Enckevort WJP,Janssen-van Rosmalen R,Klapper H,et al.Growthphenomena of KDP crystals in relation to the internal structure[J].Journal ofCrystal Growth,1982,60(1):67-78..

[0012] [5].Schulze TP,Davis S H.Shear stabilization of morphologicalinstability during directional solidification[J].Journal of crystal growth,1995,149(3-4):253-265. Summary of the Invention

[0013] The purpose of this invention is to overcome the shortcomings of the prior art and provide an apparatus and method for growing crystals in solution using reversible shear flow, which can realize the "reversible shear flow" in the theory of crystal face formation during the crystal growth process.

[0014] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0015] An apparatus for growing crystals in solution using reversible shear flow includes a growth solution pool, solution pipes disposed on both sides of the growth solution pool, a pump disposed at the connection between the growth solution pool and the solution pipes, a support mechanism that can move up and down, a shear flow channel disposed above the support mechanism and connected to the solution pipes at both ends, and an isolation cover disposed on the four sides of the support mechanism.

[0016] Furthermore, both the solution tube and the shear flow channel are rectangular, and the height of the shear flow channel is 1-3 cm.

[0017] Furthermore, the support mechanism includes a crystal support and a motor whose output end is connected to the crystal support.

[0018] Furthermore, a 1-3cm gap is left between the support mechanism and the isolation cover.

[0019] Furthermore, the support platform is positioned above the growth solution tank, with its lower end located within the growth solution tank.

[0020] Furthermore, the portion of the support structure located within the growth solution pool is sealed and isolated using polytetrafluoroethylene (PTFE) material.

[0021] A method for growing crystals in solution using the apparatus described above includes:

[0022] S1: Prepare a saturated solution for crystal growth in the growth solution tank, and keep the saturation of the solution constant by slowly cooling during the crystal growth process;

[0023] S2: Turn on the pump on one side of the growth solution pool. The saturated solution is delivered to the shear flow channel through the solution tube and flows over the surface of the crystal slice. After working for 3 minutes, stop working for 10 seconds. Then change the direction of the saturated solution flow and work for 3 minutes. Then stop working for 10 seconds. Repeat this alternating and continuous operation.

[0024] S3: During the crystal growth process, the stage mechanism moves downward under the action of the motor, so that the crystal surface is always at the same horizontal position as the lower surface of the shear flow channel.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] (1) Crystal growth using the apparatus and method provided by the present invention can be transferred to the "reversible shear flow" in the theory of the formation of the entire crystal plane.

[0027] (2) This invention is applicable to crystals with different diameters ranging from a few centimeters to tens of centimeters. Since the crystal is fixed on the support and does not move in the solution, the problem of crystal cracking caused by mechanical movement can be minimized.

[0028] (3) The crystal growth device provided by the present invention has a simple structure and is easy to operate when crystal growth is performed using the device provided by the present invention. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the device provided by the present invention;

[0030] Figure 2 This is a schematic diagram of the support mechanism in the device provided by the present invention.

[0031] The corresponding names of the attached figures are: 1-crystal slice, 2-shear flow channel, 3-solution tube, 4-growth solution pool, 5-support mechanism, 6-isolation cover, 7-reserved gap, 8-support mechanism, 9-motor. Detailed Implementation

[0032] The present invention will be further described below with reference to the accompanying drawings and embodiments. The embodiments of the present invention include, but are not limited to, the following embodiments.

[0033] Example 1

[0034] This embodiment provides an apparatus for growing crystals in solution using reversible shear flow. It includes a growth solution tank 4 for preparing the saturated solution required for crystal growth, and two rectangular solution pipes 3 connected to the inside of the growth solution tank 4, one on each side of the growth solution tank 4. A support mechanism 5 is also provided for placing crystal slices 1 and enabling vertical movement of the crystal slices 1. The support mechanism 5 includes a crystal support 8 for placing the crystal slices 1 and a motor 9 connected to the crystal support 8 at its output end. This motor 9 is a lifting motor, enabling vertical movement of the crystal support 8. A shear flow channel 2 is located above the support mechanism 5, with both ends connected to the solution pipes 3, and the height of the shear flow channel 2 is 1 cm. Isolation covers 6, made of glass, are provided on the four sides of the support mechanism 5, with a 1 cm clearance 7 between the isolation covers 6 and the support mechanism 5. In this embodiment, the support platform 5 is positioned above the growth solution pool 4, with a portion of its lower end located within the growth solution pool 4. During the crystal growth process on the crystal slice 1, some of the growth solution can flow back into the growth solution pool 4 through the reserved gap 7. To ensure the normal operation of the lifting motor and prevent contamination of the growth solution, the portion of the support platform 5 that contacts the growth solution is sealed and isolated using polytetrafluoroethylene material.

[0035] In addition, in order to enable the growth solution in the growth solution tank 4 to flow to the shear flow channel 2 through the solution pipe 3, a pump is also provided at the connection between the growth solution tank 4 and the solution pipe 3. Preferably, the pump is a peristaltic pump.

[0036] The method for growing crystals using the above-mentioned apparatus is as follows:

[0037] (1) Prepare a saturated solution for crystal growth in the growth solution tank, and keep the saturation of the solution constant by slowly cooling during the crystal growth process;

[0038] (2) Turn on the peristaltic pump. Driven by the pump, the saturated solution required for crystal growth is delivered to the shear flow channel through the solution tube and then flows over the surface of the crystal slice. During operation, work in the direction of flow mode 1 for 3 minutes, then stop working for 10 seconds, and then work in the direction of flow mode 2 for 3 minutes. This process is repeated continuously.

[0039] (3) During the crystal growth process, the support mechanism moves slowly downward under the action of the motor, so that the crystal surface is always at the same level as the lower surface of the shear flow channel.

[0040] Example 2

[0041] This embodiment provides an apparatus for growing crystals in solution using reversible shear flow. Based on embodiment 1, the height of the shear flow channel 2 is 3cm, and the width of the reserved gap 7 between the isolation cover 6 and the support mechanism 5 is 3cm. During the crystal growth process, the peristaltic pump is turned on and operates for 5 minutes according to the flow direction of flow mode 1. Then, it stops working for 30 seconds and operates for 5 minutes according to the flow direction of flow mode 2. This process is repeated continuously.

[0042] This invention enables the realization of "reversible shear flow" in the theory of crystal formation, and is applicable to crystals with different diameters ranging from a few centimeters to tens of centimeters. At the same time, since the crystal is fixed on the crystal support and does not move in the solution, the crystal cracking problem caused by mechanical movement can be minimized.

[0043] The above embodiments are merely one of the preferred embodiments of the present invention and should not be used to limit the scope of protection of the present invention. Any modifications or refinements made to the main design concept and spirit of the present invention that are not of substantial significance, but solve the same technical problem as the present invention, should be included within the scope of protection of the present invention.

Claims

1. An apparatus for growing crystals in solution using reversible shear flow, comprising a growth solution tank (4), characterized in that, It also includes solution pipes (3) set on both sides of the growth solution pool (4), a pump set at the connection between the growth solution pool (4) and the solution pipes (3), a support platform mechanism (5) that can move up and down, a shear flow channel (2) set above the support platform mechanism (5) and connected to the solution pipes (3) at both ends, and an isolation cover (6) set on the four sides of the support platform mechanism (5); the height of the shear flow channel (2) is 1-3cm.

2. The apparatus for growing crystals in solution using reversible shear flow according to claim 1, characterized in that, Both the solution tube (3) and the shear flow channel (2) are rectangular.

3. The apparatus for growing crystals in solution using reversible shear flow according to claim 1, characterized in that, The support mechanism (5) includes a crystal support (8) and a motor (9) whose output end is connected to the crystal support (8).

4. An apparatus for growing crystals in solution using reversible shear flow according to claim 2 or 3, characterized in that, A 1-3cm gap (7) is left between the support platform (5) and the isolation cover (6).

5. The apparatus for growing crystals in solution using reversible shear flow according to claim 4, characterized in that, The support platform (5) is positioned above the growth solution pool (4), and its lower end is located in the growth solution pool (4).

6. The apparatus for growing crystals in solution using reversible shear flow according to claim 5, characterized in that, The portion of the support structure (5) located within the growth solution pool (4) is sealed and isolated using polytetrafluoroethylene material.

7. A method for growing crystals in solution using the apparatus according to any one of claims 1 to 6, characterized in that, include: S1: Prepare a saturated solution for crystal growth in the growth solution tank, and keep the saturation of the solution constant by slowly cooling during the crystal growth process; S2: Turn on the pump on one side of the growth solution pool. The saturated solution is delivered to the shear flow channel through the solution tube and flows over the surface of the crystal slice. After working for 3 minutes, stop working for 10 seconds. Then change the direction of the saturated solution flow and work for 3 minutes. Then stop working for 10 seconds. Repeat this alternating and continuous operation. S3: During the crystal growth process, the stage mechanism moves downward under the action of the motor, so that the crystal surface is always at the same horizontal position as the lower surface of the shear flow channel.

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