Device and method for growing crystals in solution by utilizing reversible shear flow

Abstract

The invention discloses a device and a method for growing a crystal in a solution by using reversible shear flow, and relates to the technical field of artificial crystal growth, the device comprises a growth solution pool, solution pipes arranged on two sides of the growth solution pool, a pump arranged at the joint of the growth solution pool and the solution pipes, and a saddle mechanism capable of moving up and down, the shear flow channel is arranged above the supporting table mechanism, two ends of the shear flow channel are communicated with the solution pipe, and the isolation hood is arranged on the peripheral side surface of the supporting table mechanism. According to the invention, 'reversible shear flow 'in the whole crystal face forming theory can be realized, the device is suitable for crystals with different calibers from several centimeters to dozens of centimeters, and meanwhile, as the crystals are fixed on the crystal support table and do not move in a solution, the problem of crystal cracking caused by mechanical movement can be reduced to the greatest extent.

Description

Technical Field

[0001] The invention relates to the technical field of artificial crystal growth, and in particular to a device and method for growing crystals in a solution using a reversible shear flow. Background Art

[0002] Solution crystal growth is an important method for preparing crystal materials, and it is also the only method for growing large-diameter nonlinear optical crystals. In the process of solution crystal growth, convection material transport is an important part of crystal growth, which directly affects the growth rate and quality of the crystal. On the one hand, convection can significantly improve the material transport at the crystal / liquid interface, which can increase the growth rate of the crystal by an order of magnitude. [1] On the other hand, convection can induce defects in the inclusions. [2] , which reduces the performance or service life of the crystal [3] . In the actual crystal growth process, one of the necessary measures to achieve rapid crystal growth is to generate forced convection through relative movement of crystals to strengthen the mass transfer process at the growth interface. The rotating crystal method, that is, making the crystal rotate, stop, and reverse during the growth process, is the most widely used crystal movement method. However, in this method, there are stagnation areas facing the liquid flow and convection vortex cells facing the liquid flow on the crystal surface where inclusions are easily formed. The existence of these areas will significantly reduce the growth quality of the crystal. Designing a crystal growth method that can fully utilize the enhanced mass transfer effect of convection and avoid the adverse effects of convection is the key to quickly growing high-quality crystals.

[0003] The growth of solution crystals is a process in which adjacent steps spread on the crystal surface to form layers of crystal surfaces. A large number of studies have shown that the effect of convection on the quality of crystal growth is actually the effect of convective material transport on the morphological stability of the crystal surface. The instability of the crystal surface morphology will induce the formation of liquid inclusions and ultimately lead to a decrease in crystal quality. [4] Theoretical analysis shows that [5] "Reversible shear flow" (flow parallel to the crystal plane and the fluid can immediately turn 180 degrees) can keep the crystal plane morphology stable. If this theory is combined with the actual crystal growth, and "reversible shear flow" is created in the ideal state during the growth process, theoretically, it is possible to grow crystals with extremely high quality while ensuring the crystal growth rate.

[0004] The present invention starts with regulating the convective mass transfer process of crystal growth, and through a specially designed solution supply method, approximately forms the theoretical "reversible shear flow" at the crystal / liquid interface to achieve the growth of high-quality crystals.

[0005] The patent application with publication number CN103060888A provides a method for growing crystals in a solution in which the crystals perform three-dimensional motion, and proposes a method for growing crystals in which the crystals perform special motion. This method can improve the uniformity of solute distribution on the crystal surface, which is beneficial to the improvement of crystal quality to a certain extent, but cannot form "reversible shear flow". Since it uses a crystal lifting rod for fixation, it is not suitable for the growth of large-diameter crystals.

[0006] The patent application with publication number CN113604882A provides a KDP crystal solution alternating flow growth method, which proposes to form an alternating flow near the crystal surface by jet flow, so as to be used for the rapid and high-quality growth of KDP crystals. This method can partially achieve alternating flow in the area near the nozzle, but cannot achieve full coverage of the entire crystal surface; at the same time, dozens or hundreds of small-aperture nozzles need to be arranged during the application process, which may cause problems such as uneven nozzle flow and nozzle clogging.

[0007] Based on previous research, the present invention proposes to use a narrow slit to form a high-speed shear flow on the crystal plane, and at the same time, by periodically changing the flow direction, ultimately achieve the "reversible shear flow" that is most conducive to crystal growth in the crystal plane formation theory, thereby achieving 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 the present invention is to overcome the deficiencies of the prior art and to provide a device and method for growing crystals in a solution using reversible shear flow, which can realize the "reversible shear flow" in the entire crystal face formation theory during the crystal growth process.

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

[0015] A device for growing crystals in a solution using reversible shear flow comprises a growth solution pool, solution tubes arranged on both sides of the growth solution pool, a pump arranged at the connection between the growth solution pool and the solution tube, a support platform mechanism that can move up and down, a shear flow channel arranged above the support platform mechanism and connected to the solution tube at both ends, and an isolation cover arranged on the sides of the support platform mechanism.

[0016] Furthermore, the solution tube and the shear flow channel are both 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 reserved gap of 1-3 cm is left between the support mechanism and the isolation cover.

[0019] Furthermore, the support platform mechanism is arranged above the growth solution pool, and its lower end is located in the growth solution pool.

[0020] Furthermore, the portion of the support mechanism located in the growth solution pool is sealed and isolated with polytetrafluoroethylene material.

[0021] The method for growing crystals in a solution using the above-mentioned device comprises:

[0022] S1: preparing a saturated solution required for crystal growth in a growth solution pool, and keeping the saturation of the solution constant by slowly cooling it during the crystal growth process;

[0023] S2: Turn on the pump on one side of the growth solution pool, and the saturated solution is transported to the shear flow channel through the solution tube and flows over the surface of the crystal slice. After working for 3 minutes, it stops working for 10 seconds, and then the saturated solution flow direction is changed to work for 3 minutes, and then it stops working for 10 seconds. This alternating operation is repeated continuously.

[0024] S3: During the growth of the crystal, the support 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) The device and method provided by the present invention are used to grow crystals, which can remove the "reversible shear flow" in the entire crystal surface formation theory.

[0027] (2) The present invention 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 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 the operation of using the device provided by the present invention to grow crystals is simple. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0031] Among them, the names corresponding to the figure marks 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 DESCRIPTION

[0032] The present invention is further described below in conjunction with the accompanying drawings and embodiments. The embodiments of the present invention include but are not limited to the following embodiments.

[0033] Example 1

[0034] The present embodiment provides a device for growing crystals in a solution using a reversible shear flow, including a growth solution pool 4 for preparing a saturated solution required for crystal growth, a solution tube 3 connected to the inside of the growth solution pool 4 for conveying a saturated solution, the solution tube 3 is rectangular, and two are provided, respectively provided on both sides of the growth solution pool 4; in addition, a support mechanism 5 is provided for placing a crystal slice 1 and enabling the crystal slice 1 to move up and down, the support mechanism 5 includes a crystal support 8 for placing the crystal slice 1 and a motor 9 connected to the crystal support 8 at the output end, the motor 9 is a lifting motor, and enables the crystal support 8 to move up and down. Above the support mechanism 5 is a shear flow channel 2, the two ends of the shear flow channel 2 are respectively connected to the solution tube 3, and the height of the shear flow channel 2 is 1 cm. An isolation cover 6 is provided on the sides of the support mechanism 5, the isolation cover 6 is made of glass, and a reserved gap 7 of 1 cm is left between the support mechanism 5. In this embodiment, the support mechanism 5 is arranged above the growth solution pool 4, and a part of its lower end is located in the growth solution pool 4. During the crystal growth process on the crystal slice 1, part of the growth solution can flow back into the growth solution pool 4 through the reserved gap 7. In order to ensure the normal operation of the lifting motor and the growth solution is not contaminated, the part of the lower end of the support mechanism 5 that contacts the growth solution is sealed and isolated with polytetrafluoroethylene material.

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

[0036] The method for growing crystals using the above device is as follows:

[0037] (1) preparing a saturated solution required for crystal growth in a growth solution pool, and maintaining a constant saturation of the solution by slowly cooling the solution during the crystal growth process;

[0038] (2) Turn on the peristaltic pump. Driven by the pump, the saturated solution required for crystal growth is transported to the shear flow channel through the solution tube, and then flows over the surface of the crystal slice; during the operation, the flow direction of flow mode 1 is first operated for 3 minutes, then stopped for 10 seconds, and then operated for 3 minutes according to the flow direction of flow mode 2, and this alternating operation is repeated continuously;

[0039] (3) During the growth of the crystal, the support mechanism moves slowly 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.

[0040] Example 2

[0041] The present embodiment provides a device for growing crystals in a solution using reversible shear flow. Based on Embodiment 1, the height of the shear flow channel 2 is 3 cm, and the width of the reserved gap 7 between the isolation cover 6 and the support mechanism 5 is 3 cm. During the growth of the crystal, the peristaltic pump is turned on, and it first works for 5 minutes according to the flow direction of flow mode 1, then stops working for 30 seconds, and then works for 5 minutes according to the flow direction of flow mode 2, and the operation is repeated alternately and continuously.

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

[0043] The above embodiment is only one of the preferred implementation modes of the present invention and should not be used to limit the protection scope of the present invention. Any changes or modifications that are made to the main design concept and spirit of the present invention and have no substantive significance, and the technical problems they solve are still consistent with the present invention, should be included in the protection scope of the present invention.

Claims

1. A device for growing crystals in a solution using reversible shear flow, comprising a growth solution pool (4), characterized in that: The invention also comprises solution pipes (3) arranged on both sides of a growth solution pool (4), a pump arranged at the connection between the growth solution pool (4) and the solution pipe (3), a support platform mechanism (5) capable of moving up and down, a shear flow channel (2) arranged above the support platform mechanism (5) and connected to the solution pipe (3) at both ends, and an isolation cover (6) arranged on the sides of the support platform mechanism (5).

2. The device for growing crystals in a solution using reversible shear flow according to claim 1, characterized in that: The solution tube (3) and the shear flow channel (2) are both rectangular, and the height of the shear flow channel (2) is 1-3 cm.

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

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

5. The device for growing crystals in a solution using reversible shear flow according to claim 4, characterized in that: The support platform mechanism (5) is arranged above the growth solution pool (4), and the lower end thereof is located in the growth solution pool (4).

6. The device for growing crystals in a solution using reversible shear flow according to claim 5, characterized in that: The part of the support mechanism (5) located in the growth solution pool (4) is sealed and isolated with polytetrafluoroethylene material.

7. A method for growing crystals in a solution using the device according to any one of claims 1 to 6, characterized in that: include: S1: preparing a saturated solution required for crystal growth in a growth solution pool, and keeping the saturation of the solution constant by slowly cooling it during the crystal growth process; S2: Turn on the pump on one side of the growth solution pool, and the saturated solution is transported to the shear flow channel through the solution tube and flows over the surface of the crystal slice. After working for 3 minutes, it stops working for 10 seconds, and then the saturated solution flow direction is changed to work for 3 minutes, and then it stops working for 10 seconds. This alternating operation is repeated continuously. S3: During the growth of the crystal, the support 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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