Method for growing metal single crystal through heterogeneous seed crystal induction and metal single crystal

Abstract

The invention discloses a method for growing a metal single crystal through heterogeneous seed crystal induction and the metal single crystal. A metal simple substance or alloy is added into a crucible to serve as a raw material, the surface of the raw material is covered with a heterogeneous single crystal wafer to serve as a seed crystal, and the density of the seed crystal is lower than that of molten liquid formed after the raw material is molten; placing the crucible in a vacuum furnace, purifying the internal atmosphere of the vacuum furnace, and heating to fully melt the raw materials to form a melt; and slowly cooling at a set cooling rate to start crystallization on the surface of the melt, and transferring seed crystals on the surface after cooling to obtain the metal single crystal. According to the method, a heterogeneous single crystal wafer is placed on the surface of molten metal, and in the slow cooling process, metal or alloy is induced to start directional crystallization from the surface of the molten metal. Compared with an existing preparation method, the method is simple in principle, novel and easy to operate.

Description

Technical Field

[0001] This invention belongs to the field of single crystal material growth technology, and specifically relates to a method for heterogeneous seed crystal-induced growth of metal single crystals and the metal single crystal itself. Background Technology

[0002] Metallic single crystals, due to their boundary-free single-phase structure, exhibit superior mechanical properties and high-temperature strength. They also possess advantages such as anisotropy. Metallic single crystals have typical applications in important fields such as aerospace and electronic devices. For example, nickel-based single-crystal superalloys have optimal creep resistance in the <001> direction; nickel-based single-crystal metals used in aero-engine blades also possess high-strength creep and fatigue resistance at high temperatures; bismuth single crystals possess unique electrical or magnetic properties and are used in sensor or quantum material research; single-crystal copper is used in high-conductivity wire coating technology in electronic devices, etc.

[0003] Currently, the fabrication process for single-crystal metals is extremely complex and costly. Therefore, it is typically only used in fields with extreme performance requirements and extremely high added value. Most methods use metallic substrates for growth, and the quality of the metallic substrate directly determines the growth quality of the two-dimensional material. Traditional methods such as the Bridgman process and zone melting require extremely high levels of equipment and process control. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a simple and easy-to-operate method for heterogeneous seed crystal-induced growth of metal single crystals, and to obtain two-stage metal single crystals by the method.

[0005] To solve the above technical problems, according to one aspect of the present invention, a method for heterogeneous seed-induced growth of metal single crystals is provided, comprising: Step 1: Add a metallic element or alloy to a crucible as raw material, and cover the surface of the raw material with a heterogeneous single crystal as a seed crystal. The density of the seed crystal is lower than the density of the melt formed after the raw material is melted. Step two: Place the crucible inside the vacuum furnace and purify the atmosphere inside the furnace; Step 3: Heat the raw materials to fully melt them and form a molten liquid; Step 4: Slowly cool down the melt at the set cooling rate to allow the surface of the melt to begin to crystallize. Step 5: After cooling, transfer the seed crystal on the surface to obtain a metal single crystal.

[0006] In a preferred embodiment, in step one, the crucible is pretreated before use, and the pretreatment procedure is to bake it in an oven at 150±5℃.

[0007] In a preferred embodiment, in step one, the seed crystal is selected from sapphire single crystal, graphite single crystal, silicon carbide single crystal, or hexagonal boron nitride single crystal (h-BN).

[0008] In a preferred embodiment, in step one, the raw materials include elemental metals or alloys in the Fe-Ni, Cu-Al, or Mg-Al systems.

[0009] In a preferred embodiment, step two, the procedure for purifying the atmosphere inside the vacuum furnace, includes: after the furnace cavity is sealed, turning on the vacuum pump to pump the pressure inside the vacuum furnace to 1×10⁻⁶. -4 Below 100 kPa, fill the furnace with high-purity argon gas to atmospheric pressure and repeat the operation 3-5 times; finally, fill the furnace cavity with high-purity argon gas at 30-50 kPa.

[0010] In a preferred embodiment, the cooling rate in step four is set to 3-5℃ / min.

[0011] In a preferred embodiment, in step five, the seed crystal is transferred by mechanical stripping.

[0012] According to another aspect of the present invention, a metal single crystal is provided that is obtained by the method for inducing growth of metal single crystals according to the above-described heterogeneous seed crystal.

[0013] According to the method provided by this invention, a heterogeneous single-crystal wafer is placed on the surface of a molten metal or alloy as a seed crystal. After melting, the melt is cooled down while maintaining a minimum surface temperature. During this slow cooling process, the seed crystal induces the molten melt to crystallize into metal single crystals from the surface. The seed crystal material is not destroyed within the molten metal, and its density is lower than that of the molten metal, ensuring that the heterogeneous seed crystal floats on the surface of the melt. Compared with existing preparation methods, this invention is simple in principle, novel in method, and easy to operate. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the vacuum furnace growth apparatus according to an embodiment of the present invention; in the figure, 1-crucible, 2-graphite heater, 3-graphite felt, 4-molten liquid, 5-heating coil, 6-heterogeneous seed wafer.

[0015] Figure 2 This is a crystal surface morphology diagram from Example 4.

[0016] Figure 3 This is an optical microscope image of the metal surface in Example 4. Detailed Implementation

[0017] The basic concept of this invention is to place a heterogeneous single crystal wafer on the surface of a molten metal and induce the metal or alloy to crystallize directionally from the surface of the molten metal during a slow cooling process.

[0018] Based on this, a typical embodiment of the present invention provides a method for heterogeneous seed crystal-induced growth of metal single crystals, comprising the following steps one to five.

[0019] Step 1: Selection and placement of raw materials and seed crystals.

[0020] A metallic element or alloy is added to a crucible as raw material, and a heterogeneous single crystal is placed on the surface of the raw material as a seed crystal. The density of the seed crystal is lower than the density of the melt formed after the raw material is melted.

[0021] In this step, the crucible needs to be pretreated before use. The pretreatment procedure is to bake it in an oven at 150±5℃. For example, the crucible is baked in an oven at 150℃ for 120 minutes, or in an oven at 155℃ for 120 minutes, or in an oven at 145℃ for 120 minutes.

[0022] The seed crystal is selected from sapphire single crystal, graphite single crystal, silicon carbide single crystal or hexagonal boron nitride single crystal (h-BN). The metal element or alloy is heated and melted in subsequent steps to form a molten liquid. The selected seed crystal has a lower density than the metal molten liquid to ensure that the heterogeneous seed crystal floats on the surface of the molten liquid.

[0023] In a preferred embodiment, the raw material includes elemental metals or alloys from the Fe-Ni, Cu-Al, or Mg-Al systems. Taking the Fe-Ni system as an example, the raw material can be elemental Fe or Ni metals, or it can be an Fe-Ni alloy.

[0024] Step two: Vacuum environment purification and gas protection.

[0025] Place the crucible inside the vacuum furnace to purify the atmosphere inside the furnace.

[0026] In a relatively specific implementation, the procedure for purifying the internal atmosphere of the vacuum furnace includes: after the furnace cavity is sealed, the vacuum pump is turned on to pump the pressure inside the vacuum furnace to 1×10⁻⁶. -4 Below 100 kPa, fill the furnace with high-purity argon gas to atmospheric pressure and repeat the operation 3-5 times; finally, fill the furnace cavity with 30-50 kPa of high-purity argon gas to prevent the evaporation of the metal flux under vacuum.

[0027] Step 3: Heat and melt.

[0028] Turn on the heating system to heat the raw materials to fully melt them into a molten liquid, and the seed crystals float on the surface of the molten liquid.

[0029] Step four: Cool down for crystallization.

[0030] The molten metal is cooled slowly at a set cooling rate, preferably 3-5°C / min. During this process, the surface temperature of the molten metal is at its lowest, and the heterogeneous seed crystals float on the surface of the molten metal without being destroyed. As the molten metal slowly cools, it begins to crystallize from the surface into single metal crystals.

[0031] Step 5: Transfer the seed crystal.

[0032] After growth is complete, the power supply is turned off, and the equipment is allowed to cool down naturally. Once it has cooled to room temperature, the crucible is removed after venting, and the heterogeneous seed crystal on the surface is transferred using mechanical peeling. The crystal is then polished to obtain a metallic single crystal.

[0033] The technical solutions claimed in this invention will be further described below through some embodiments. However, the embodiments are for explaining the implementation of the present invention and do not exceed the scope of the subject matter of the present invention. The scope of protection of the present invention is not limited by the embodiments. Unless otherwise specified, the materials and reagents used in this invention can be obtained from commercially available products in the art.

[0034] The following examples are all in Figure 1 The vacuum furnace growth apparatus shown includes a crucible 1, a graphite heater 2, a graphite felt 3, and a heating coil 5. The graphite heater 2 is located on the innermost side of the vacuum furnace wall structure, and the crucible 1 is placed inside the graphite heater 2. The graphite felt 3 is arranged around the graphite heater 2, and the heating coil 5 is also located there. Figure 1 As shown, the heterogeneous seed wafer 6 floats on the surface of the molten liquid 4 formed by the melting of a single metal or alloy. Example 1

[0035] Place the corundum crucible in a 150℃ oven and bake for 120 minutes to dry it.

[0036] Fe and Ni elements, taken in a 1:1 mass ratio, are placed in an alumina crucible. A (0001) sapphire single crystal with a density lower than that of the molten metal is placed on the upper surface of the metal as a seed crystal. The crucible is then placed in a graphite heater. The pressure inside the vacuum furnace is evacuated to 1 × 10⁻⁶ using a vacuum pump. -4 The pressure is below 10 Pa, then argon is introduced to atmospheric pressure. This process is repeated 3-5 times to purify the atmosphere inside the furnace, remove residual background gas from the furnace cavity, and then the vacuum pump is turned off.

[0037] Turn on the power and first fill the furnace cavity with 30 kPa of argon gas to prevent the metal flux from evaporating under vacuum. Then turn on the heating system to heat the crucible in the furnace until the metal is fully melted.

[0038] After the metal melts, the sapphire seed crystal floats on the surface of the molten liquid. Then, the liquid is slowly cooled at a rate of 3°C / min, allowing the molten liquid to crystallize from the surface into metal single crystals during the slow cooling process.

[0039] Turn off the power supply and allow it to cool naturally to room temperature. After releasing the gas, remove the corundum crucible, transfer the sapphire seed crystal on the surface, perform grinding and polishing, and observe the surface metal single crystal. Example 2

[0040] Place the graphite crucible in a 150℃ oven and bake for 120 minutes to dry it.

[0041] Cu and Al elements, with a Cu:Al molar ratio of 67:33, were placed in a graphite crucible. A graphite single crystal with a density lower than that of the molten metal was placed on the upper surface of the metal as a seed crystal, and the crucible was placed in a graphite heater. The pressure inside the vacuum furnace was evacuated to 1×10⁻⁶ using a vacuum pump. -4 The pressure is below 10 Pa, then argon is introduced to atmospheric pressure. This process is repeated 3-5 times to purify the atmosphere inside the furnace, remove residual background gas from the furnace cavity, and then the vacuum pump is turned off.

[0042] Turn on the power and first fill the furnace cavity with 30 kPa of argon gas to prevent the metal flux from evaporating under vacuum. Then turn on the heating system to heat the crucible in the furnace until the metal is fully melted.

[0043] After the metal melts, the graphite seed crystals float on the surface of the melt. The melt is then slowly cooled at a rate of 5°C / min, allowing the metal single crystals to crystallize from the surface during the slow cooling process.

[0044] Turn off the power supply and allow it to cool naturally to room temperature. After releasing the gas, remove the graphite crucible, transfer the graphite seed crystal on the surface, perform grinding and polishing, and observe the surface metal single crystal. Example 3

[0045] Place the graphite crucible in a 150℃ oven and bake for 120 minutes to dry it.

[0046] Mg and Al elements, taken in a Mg:Al molar ratio of 7:3, were placed in a graphite crucible. A (0001)4H silicon carbide single crystal with a density lower than that of the molten metal was placed on the upper surface of the metal as a seed crystal. The crucible was then placed in a graphite heater. The pressure inside the vacuum furnace was evacuated to 1×10⁻⁶ using a vacuum pump. -4 The pressure is below 10 Pa, then argon is introduced to atmospheric pressure. This process is repeated 3-5 times to purify the atmosphere inside the furnace, remove residual background gas from the furnace cavity, and then the vacuum pump is turned off.

[0047] Turn on the power and first fill the furnace cavity with 30 kPa of argon gas to prevent the metal flux from evaporating under vacuum. Then turn on the heating system to heat the crucible in the furnace until the metal is fully melted.

[0048] After the metal melts, silicon carbide seed crystals float on the surface of the molten liquid. The liquid is then slowly cooled at a rate of 4°C / min, allowing single metal crystals to crystallize from the surface as the molten liquid cools slowly.

[0049] Turn off the power supply and allow it to cool naturally to room temperature. After releasing the gas, remove the graphite crucible, transfer the silicon carbide seed crystal on the surface, perform grinding and polishing, and observe the surface metal single crystal. Example 4

[0050] Place the corundum crucible in a 150℃ oven and bake for 120 minutes to dry it.

[0051] Fe and Ni elements, taken in a 1:1 mass ratio, are placed in an alumina crucible. A hexagonal boron nitride single crystal (h-BN) with a density lower than that of the molten metal is placed on the upper surface of the metal as a seed crystal. The crucible is then placed in a graphite heater. The pressure inside the furnace is evacuated to 1 × 10⁻⁶ using a vacuum pump. -4 The pressure is below 10 Pa, then argon is introduced to atmospheric pressure. This process is repeated 3-5 times to purify the atmosphere inside the furnace, remove residual background gas from the furnace cavity, and then the vacuum pump is turned off.

[0052] Turn on the power and first fill the furnace chamber with 50 kPa of argon gas to prevent the metal flux from evaporating under vacuum. Then turn on the heating system to heat the crucible inside the furnace until the metal is fully melted.

[0053] After the metal melts, the h-BN seed crystal floats on the surface of the melt. Then, the temperature is slowly reduced at a rate of 4℃ / min, allowing the melt to crystallize from the surface into metal single crystals during the slow cooling process.

[0054] Turn off the power supply and allow it to cool naturally to room temperature. After venting, remove the corundum crucible, transfer the surface h-BN seed crystal, and perform grinding and polishing. Observe the surface metal single crystals (such as...). Figure 2 and Figure 3 (As shown).

[0055] The scope of protection claimed by this invention is not limited to the specific embodiments described above. For those skilled in the art, this invention can have various modifications and alterations. Any modifications, improvements, and equivalent substitutions made within the concept and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A method for inducing the growth of metal single crystals using heterogeneous seed crystals, characterized in that, include: Step 1: Add a metallic element or alloy to a crucible as raw material, and cover the surface of the raw material with a heterogeneous single crystal as a seed crystal. The density of the seed crystal is lower than the density of the melt formed after the raw material is melted. Step two: Place the crucible inside the vacuum furnace and purify the atmosphere inside the furnace; Step 3: Heat the raw materials to fully melt them and form a molten liquid; Step 4: Slowly cool down the melt at the set cooling rate to allow the surface of the melt to begin to crystallize. Step 5: After cooling, transfer the seed crystal on the surface to obtain a metal single crystal.

2. The method for inducing growth of metal single crystals using heterogeneous seed crystals according to claim 1, characterized in that: In step one, the crucible is pretreated before use. The pretreatment procedure is to bake it in an oven at 150±5℃.

3. The method for heterogeneous seed-induced growth of metal single crystals according to claim 1 or 2, characterized in that: In step one, the seed crystal is selected from sapphire single crystal, graphite single crystal, silicon carbide single crystal or hexagonal boron nitride single crystal (h-BN).

4. The method for inducing the growth of metal single crystals using heterogeneous seed crystals according to claim 3, characterized in that: In step one, the raw materials include elemental metals or alloys in the Fe-Ni, Cu-Al, or Mg-Al systems.

5. The method for heterogeneous seed-induced growth of metal single crystals according to claim 1 or 4, characterized in that, Step two, the procedure for purifying the atmosphere inside the vacuum furnace, includes: after sealing the furnace cavity, turning on the vacuum pump to evacuate the pressure inside the vacuum furnace to 1×10⁻⁶. -4 Below 30 kPa, fill the furnace with high-purity argon gas to atmospheric pressure and repeat the operation 3-5 times; finally, fill the furnace cavity with high-purity argon gas at 30-50 kPa.

6. The method for inducing the growth of metal single crystals using heterogeneous seed crystals according to claim 5, characterized in that: In step four, the cooling rate is set to 3-5℃ / min.

7. The method for inducing the growth of metal single crystals using heterogeneous seed crystals according to claim 6, characterized in that: In step five, the seed crystal is transferred using a mechanical stripping method.

8. The metal single crystal obtained by the method of heterogeneous seed crystal induced growth of metal single crystal according to any one of claims 1-7.

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