Preparation method of high-temperature and high-pressure reaction kettle precious metal lining for gallium nitride crystal growth

Abstract

This invention discloses a method for preparing a noble metal liner for a high-temperature, high-pressure reactor used for gallium nitride (GaN) crystal growth. Through raw material chemical purification, precise powder mixing, hot pressing, vacuum melting, forging and strengthening, precision machining, spin forming, and sealing welding, the integrated assembly of a platinum cylinder and a platinum-iridium alloy sealing seat is achieved. The noble metal liner prepared by this invention possesses excellent high-temperature and high-pressure resistance and superior tolerance to corrosive atmospheres. It can stably adapt to the extreme conditions of GaN crystal growth, and its service life is significantly extended compared to traditional liners. It provides a reliable guarantee for the stable growth of large-size, low-defect GaN crystals, effectively improving crystal preparation quality and mass production efficiency. It is suitable for high-end electronic information industries such as GaN semiconductor material preparation.

Description

Technical Field

[0001] This invention relates to the field of reactor liner preparation technology, specifically to a method for preparing a noble metal liner for a high-temperature and high-pressure reactor used for gallium nitride crystal growth. Background Technology

[0002] With the rapid development of the semiconductor industry, the market demand and R&D needs for large-size, high-performance semiconductor materials are becoming increasingly urgent. Among them, wide-bandgap and ultra-wide-bandgap semiconductor materials (such as gallium nitride and diamond) have broad application prospects in the field of advanced semiconductor devices due to their excellent electrical, optical and thermal properties, and have become one of the core directions of semiconductor industry development.

[0003] However, the crystal growth process for such wide and ultra-wide bandgap semiconductor materials requires extremely stringent conditions, necessitating operation under combined extreme conditions such as high temperature, high pressure, and highly corrosive atmospheres. This places extremely high demands on the structural design and material properties of crystal growth equipment. Among these, the equipment liner, as a core component directly in contact with the crystal growth environment, directly determines the crystal growth effect and the equipment's operational stability. Conventional crystal growth equipment, limited by its structural design and the choice of liner materials, suffers from significant deficiencies in key performance aspects such as temperature resistance, structural strength, cleanliness of the growth environment, and long-term operational stability. Consequently, the entire equipment struggles to meet the demands of large-scale production and high-end R&D for these advanced semiconductor materials, becoming a major bottleneck restricting the development of advanced semiconductor material technology.

[0004] Specifically, the growth process of high-quality, large-size semiconductor single crystals typically has the following significant characteristics, which further intensifies the performance requirements of the equipment lining: 1. The growth process of high-quality, large-size semiconductor single crystals requires long-term continuous operation in a complex extreme environment of high temperature above 600℃, high pressure above 100MPa and strong corrosive atmosphere. This requires the equipment lining material to have excellent high temperature resistance, high pressure resistance and strong corrosion resistance to ensure the structural integrity of the lining during long-term service, thereby ensuring the stability of the crystal growth environment. 2. The growth of high-quality, large-size semiconductor crystals requires extremely high cleanliness inside the growth chamber. As a direct component of the growth chamber, the surface condition and material stability of the liner are crucial. If the liner has excessive trace impurities or structural defects (such as pores or cracks), it may affect the crystal growth system and crystallization quality, leading to a significant decrease in crystal yield or even failure to obtain qualified semiconductor single crystals. 3. The growth cycle of high-quality, large-size semiconductor single crystals is usually long, often requiring tens of hours of continuous operation. This requires the equipment lining material to have excellent high-temperature strength, oxidation and corrosion resistance, and long-term structural stability, so as to avoid problems such as aging, embrittlement, deformation, and failure during long-term service, ensure the continuity and stability of the crystal growth process, and guarantee production efficiency and product consistency.

[0005] In summary, existing crystal growth equipment liners can no longer meet the stringent process requirements for growing wide and ultra-wide bandgap semiconductor materials. Therefore, developing a crystal growth equipment liner that can withstand extreme environments of high temperature, high pressure, and strong corrosion, while possessing high cleanliness and high stability, has become an urgent technical problem to be solved in the field of semiconductor material preparation. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing technologies by providing a method for preparing a noble metal liner for a high-temperature, high-pressure reactor used for gallium nitride (GaN) crystal growth. Through optimized raw material selection and synergistic coordination of multiple core processes, a noble metal liner with excellent high-temperature and high-pressure resistance, superior corrosion resistance, and excellent sealing performance is prepared. Furthermore, a composite structure design of "high-strength alloy steel reactor body + high-purity platinum liner + platinum-iridium alloy sealing seat" is adopted, balancing the overall mechanical strength and economy of the equipment. This provides an extremely high-purity and highly stable internal environment for GaN crystal growth, extending the liner's service life, improving the quality and mass production efficiency of GaN crystal preparation, promoting the development of advanced semiconductor material preparation technology, and meeting the needs of the high-end electronic information industry for GaN semiconductor material preparation.

[0007] The objective of this invention is achieved through the following approach: A method for preparing a noble metal liner for a high-temperature, high-pressure reactor used for gallium nitride crystal growth includes the following steps: 1) Dissolve platinum raw material with a purity of 99.95% in aqua regia, and add hydrochloric acid and sodium chloride solid in sequence to obtain sodium chloroplatinate solution; add sodium hydroxide solution to sodium chloroplatinate solution, heat to boiling, and then add cerium chloride solution and sodium hypochlorite solution in sequence, controlling the pH value of the system to 9-10, filter to obtain clear filtrate; add saturated ammonium chloride solution to clear filtrate to obtain ammonium hexachloroplatinate precipitate; calcine the ammonium hexachloroplatinate precipitate to obtain 5N grade high-purity platinum powder with a purity ≥99.995%.

[0008] In step 1) of this invention, a combined process of dissolving in aqua regia, precipitating with ammonium hexachloroplatinate, and calcining reduction can efficiently remove trace metallic and non-metallic impurities from platinum raw materials. Compared to conventional purification methods, this invention can significantly improve the purity of platinum powder, ultimately obtaining 5N-grade high-purity platinum powder with a purity ≥99.995%, which can meet the extremely high purity requirements of the precious metal lining in the high-temperature and high-pressure reactor for gallium nitride crystal growth.

[0009] In the precipitation stage of ammonium hexachloroplatinate, using a saturated ammonium chloride solution significantly increases the concentration of ammonium ions in the system. This allows chloroplatinate ions in the solution to fully combine with ammonium ions, forming a highly insoluble ammonium hexachloroplatinate double salt that precipitates rapidly. In other words, using a saturated ammonium chloride solution enables platinum ions to be separated quickly and completely as a precipitate, reducing the adsorption and encapsulation of impurity ions during precipitation and ensuring the purity of the precipitate. Simultaneously, using a saturated ammonium chloride solution reduces solubility loss in the precipitate, increases platinum recovery, and avoids incomplete precipitation and decreased product yield due to insufficient solution supersaturation.

[0010] If an unsaturated ammonium chloride solution is used, the low concentration of ammonium ions in the system will result in insufficient driving force for ammonium hexachloroplatinate precipitation, a slow precipitation rate, and the tendency for impurity ions to co-precipitate or adsorb onto the surface along with the platinum precipitate. This makes them difficult to remove effectively through subsequent filtration, directly leading to a decrease in the purity of the final platinum powder, failing to meet the high-purity requirements of 5N grade. Furthermore, an excessively slow precipitation rate will directly extend the process cycle, thereby reducing production efficiency. Moreover, due to the relatively high solubility of ammonium hexachloroplatinate precipitate, platinum may not precipitate completely, resulting in a decreased effective platinum recovery rate and affecting raw material utilization.

[0011] 2) Use the high-purity platinum powder obtained in step 1) to prepare the sealing seat and platinum cylinder respectively.

[0012] 2-1) Weigh 70-80 wt% of the high-purity platinum powder obtained in step 1) and 20-30 wt% of the high-purity iridium powder with a purity ≥ 99.99% by weight to obtain a platinum-iridium mixed raw material; after homogenization and heat treatment, a platinum-iridium alloy powder is obtained.

[0013] 2-2) The platinum-iridium alloy powder obtained in step 2-1) is hot-pressed to obtain a platinum-iridium alloy ingot; the platinum-iridium alloy ingot is then subjected to homogenization treatment and heat preservation treatment, and then hot forging to obtain a platinum-iridium alloy forging blank.

[0014] 2-3) The platinum-iridium alloy forging blank obtained in step 2-2) is precision CNC machined to obtain the sealing seat.

[0015] In steps 2-3) of this invention, the platinum-iridium alloy forging blank is formed using precision CNC machining, which allows for precise control of the key structural dimensions and surface accuracy of the sealing seat. Compared to conventional machining methods, the sealing seat prepared by precision CNC machining in this invention has higher dimensional consistency and surface finish, enabling a tight fit with the corresponding assembly parts of the reactor, thereby achieving a good conical sealing effect to meet the stringent sealing performance requirements of the high-temperature and high-pressure reactor used for gallium nitride crystal growth.

[0016] During the precision CNC machining stage, it is crucial to accurately control the taper, end-face parallelism, and surface roughness of the sealing seat's conical surface. This ensures a perfect fit between the sealing seat and the reactor assembly surface, preventing excessive taper deviations that could lead to excessive gaps or excessive surface roughness that could result in a poor seal. Simultaneously, it guarantees the structural integrity of the sealing seat, preventing defects such as chipping and scratches during machining, thus laying the foundation for achieving a proper conical surface seal. Furthermore, the high-precision control of CNC machining effectively ensures dimensional uniformity of sealing seats produced in batches, improving product qualification rates and reducing assembly difficulty.

[0017] If the taper control deviation exceeds the allowable range during precision CNC machining, the sealing seat and the reactor assembly surface will not fit tightly, resulting in gaps. This can lead to high-temperature and high-pressure gas leakage, failing to achieve a good conical surface seal and affecting the stability of the gallium nitride crystal growth environment. If the surface roughness exceeds the standard, the friction between the sealing surfaces will increase, and residual media will easily remain. This will not only reduce sealing reliability but also accelerate the wear of the sealing seat, shortening its service life. Furthermore, if defects such as chipping or scratches occur during machining, the sealing surface will experience uneven stress, making it highly susceptible to breakage under high pressure, further increasing the risk of seal failure and even posing safety hazards.

[0018] 2-4) The high-purity platinum powder obtained in step 1) is vacuum melted and directionally solidified to obtain platinum ingots; the platinum ingots are hot-forged after the first heat preservation treatment to obtain platinum forging billets; the platinum forging billets are cold-rolled after the second heat preservation treatment to obtain platinum slabs.

[0019] 2-5) The platinum blank obtained in step 2-4) is integrally formed by multi-pass, multi-stage, high-pressure spinning. The spinning wheel speed is 100-300 r / min and the feed speed is 5-20 mm / min to obtain the platinum cylinder.

[0020] In steps 2-5 of this invention, the platinum slab material can form a uniform and continuous fibrous structure through a multi-pass CNC high-pressure spinning process. Compared with ordinary forming methods, the platinum cylinder prepared by CNC high-pressure spinning has better comprehensive performance and can meet the stringent requirements of subsequent practical applications for the mechanical properties, dimensional accuracy and surface quality of the platinum cylinder.

[0021] During the overall forming stage, controlling the spinning wheel speed within the range of 100–300 r / min and the feed speed within the range of 5–20 mm / min ensures sufficient extrusion cycles in each circumferential rotation of the platinum slab. This allows the thin metal layer to gradually slide and extend smoothly, preventing insufficient extrusion leading to loose material adhesion to the mold, and avoiding excessive extrusion causing material tearing. Simultaneously, within the aforementioned parameter range, less heat is generated during the downward spinning process, effectively preventing material surface depletion and thermal cracking. This ensures the platinum cylinder workpiece is free of scratches and ripples, guaranteeing forming quality.

[0022] If the spinning wheel speed is below 100 r / min or the feed rate is below 5 mm / min, the plastic flow of the metal will be discontinuous, and the platinum slab material will not have enough time to slide and adhere to the mold, resulting in local bulges and obvious stepped patterns in the platinum cylinder. At the same time, the material will exhibit work-hardening accumulation, which is prone to defects such as wrinkling and wavy edges. It will also lead to excessive thinning of the platinum cylinder wall, resulting in problems such as necking and pitting, affecting the dimensional accuracy and structural integrity of the product. If the spinning wheel speed is above 300 r / min, the spinning wheel speed is too fast, which will cause intense friction and excessive heat generation between the spinning wheel and the platinum slab. The shear rate is too fast, which will prevent the stress during the metal rheological process from being released in time, resulting in the grains being torn apart by high-speed shearing, and the mechanical properties of the platinum cylinder will be significantly deteriorated. If the feed rate is above 20 mm / min, the feed rate is too fast, which will prevent the platinum slab material from stretching smoothly, which will easily lead to material tearing and uneven platinum cylinder wall thickness, seriously affecting the product forming quality and reliability.

[0023] 3) The sealing seat and platinum cylinder obtained in step 2) are assembled by laser automatic welding to obtain the noble metal liner of the high temperature and high pressure reactor for gallium nitride crystal growth.

[0024] Preferably, in step 1), the aqua regia is prepared by mixing concentrated hydrochloric acid and concentrated nitric acid in a volume ratio of 1:1; the hydrochloric acid is a dilute hydrochloric acid prepared by mixing concentrated hydrochloric acid and deionized water in a volume ratio of 1:1; the mass fraction of the sodium chloride solid is 1%; the mass fraction of the sodium hydroxide solution is 10%; the mass fraction of the cerium chloride solution is 10%; the mass fraction of the sodium hypochlorite solution is 20%; and the calcination method is as follows: the calcination temperature is 700-900℃, and the calcination time is 6-8h.

[0025] In step 1) of this invention, by strictly controlling the preparation ratio of the above reagents and the calcination process parameters, it is possible to ensure that the platinum raw material is fully dissolved, impurities are effectively removed, and platinum elements are efficiently precipitated and reduced, significantly improving the purity and yield of high-purity platinum powder. This ensures that the final 5N-grade high-purity platinum powder meets the stringent requirements for raw material purity in the subsequent preparation of platinum-iridium alloys. The specific analysis is as follows: ① Controlling the mass fraction of sodium hydroxide solution to 10% can effectively adjust the pH value of the system to the range required for subsequent reactions, while ensuring that excess acid can be neutralized, creating suitable conditions for the reaction of cerium chloride and sodium hypochlorite.

[0026] ② Controlling the mass fraction of cerium chloride solution to 10% and sodium hypochlorite solution to 20% ensures that impurity ions are fully oxidized and removed, avoiding the impact of impurity residue on the purity of platinum powder.

[0027] ③ Controlling the calcination temperature at 700-900℃ and the calcination time at 6-8h can ensure that the ammonium hexachloroplatinate precipitate is fully decomposed and reduced to obtain high-purity platinum powder. At the same time, it avoids precipitate residue due to insufficient calcination or oxidation and coarse grains of platinum powder due to excessive calcination, which would affect the subsequent molding performance of platinum powder.

[0028] In other words, the preparation ratios, dosages, and process parameters of the aforementioned reagents are crucial for achieving the preparation of 5N-grade high-purity platinum powder. Furthermore, these parameters are interdependent and mutually restrictive, and none can be omitted. Whether it's controlling the mass fractions of sodium hydroxide solution, cerium chloride solution, and sodium hypochlorite solution, or adjusting the calcination temperature and time, all must strictly adhere to the aforementioned values ​​and ranges. Any deviation in the dosage of any reagent, incorrect ratio, or improper operating sequence, even a slight deviation in parameters, will disrupt the stability of the entire purification system, leading to insufficient dissolution of platinum raw materials, incomplete removal of impurities, and incomplete precipitation and reduction of platinum elements. Ultimately, it will be impossible to obtain 5N-grade high-purity platinum powder with a purity ≥99.995%. For example: (1) If the mass fractions of sodium hydroxide solution, cerium chloride solution and sodium hypochlorite solution deviate from the specified range, it will lead to incomplete removal of impurities and loss of control over the pH value of the system, which will result in a decrease in the final purity of platinum powder.

[0029] (2) If the calcination temperature is below 700℃ or the calcination time is less than 6h, the ammonium hexachloroplatinate precipitation decomposition will be insufficient, leaving impurities and causing the platinum powder purity to be substandard; if the calcination temperature is above 900℃ or the calcination time is longer than 8h, the platinum powder will be oxidized and agglomerated, affecting the subsequent preparation quality of platinum-iridium alloy.

[0030] Preferably, in step 2-1), the homogenization mixing method is: mixing powder using a three-dimensional powder mixer or a V-type powder mixer, with a mixing time of 5-10 hours; the heat treatment method is: under a hydrogen atmosphere, the treatment temperature is 800-1000℃, and the treatment time is 3-5 hours.

[0031] In step 2-1) of this invention, high-purity platinum powder and high-purity iridium powder are mixed using a three-dimensional powder mixer or a V-type powder mixer, which has higher mixing efficiency and more uniform mixing effect. The mixing time is controlled at 5-10 hours, achieving deep fusion of the two powders while avoiding excessive agglomeration during the mixing process. This ensures that the high-purity platinum and iridium powders are fully mixed and evenly distributed. Simultaneously, during the heat treatment stage, hydrogen, as a reducing medium, efficiently removes the oxide layer on the surface of the platinum-iridium mixed powder, fully reducing the oxidized metal ions to elemental metals. It also removes moisture from the powder, keeping it dry and effectively improving its plasticity and flowability, thus enhancing its molding performance.

[0032] Preferably, in step 2-2), the hot pressing method is as follows: the vacuum degree is 1×10 -3 ~9×10 -3 The molding temperature is 1500~1700℃, and the molding pressure is 15~25MPa.

[0033] Preferably, in step 2-2), the homogenization process is performed with a vacuum degree of 1×10⁻⁶. -3 ~9×10 -3 Pa, the treatment temperature is 1400~1600℃, and the holding time is 4~8h.

[0034] In step 2-2) of this invention, the vacuum degree is controlled to 1×10 -3 ~9×10 -3 Pa effectively isolates the platinum-iridium alloy from air, preventing oxidation during high-temperature processing and protecting the purity and performance of the forging billet from the introduction of oxide impurities. Simultaneously, by controlling the homogenization treatment temperature to 1400–1600℃ and the holding time to 4–8 hours, the elements within the platinum-iridium alloy diffuse fully, effectively eliminating residual component segregation after hot pressing and forging. This results in a more uniform component distribution, refines coarse grains, eliminates internal stress and microcracks, and improves the plasticity, strength, and toughness of the forging billet, ensuring it is less prone to cracking and deformation during subsequent processing.

[0035] Preferably, in step 2-2), the heat preservation treatment is performed at a temperature of 1200-1400℃ for 30-40 minutes.

[0036] Preferably, in steps 2-4), the vacuum melting method is as follows: the vacuum degree is 1×10⁻⁶. -3 ~9×10 -3 Pa, refining temperature is 1850~2100℃, refining 2~3 times, and the refining time for each time is 3~5min.

[0037] Preferably, in steps 2-4), the directional solidification method includes: after refining, filling with argon gas of 99.999% purity to maintain the pressure inside the furnace at 90-95 kPa.

[0038] In steps 2-4) of this invention, after refining, by introducing high-purity argon gas with a purity of 99.999% into the furnace, the internal gas during the solidification process of the platinum liquid can be discharged, effectively reducing defects such as pores, cracks, and inclusions inside the platinum ingot, further improving the purity and density of the platinum ingot, and enhancing its mechanical properties and corrosion resistance.

[0039] Preferably, in steps 2-4), the first heat preservation treatment is performed at a temperature of 1000-1200℃ for 30-40 minutes; the second heat preservation treatment is performed at a temperature of 1000-1200℃ for 20-30 minutes.

[0040] Preferably, in step 3), the automatic laser welding includes pulsed laser welding and continuous laser welding, and the welding process is carried out under argon protection.

[0041] In step 3) of this invention, by using laser automatic welding combined with argon gas protection, the uniformity and reliability of the weld can be significantly improved. The specific analysis is as follows: the heat-affected zone of laser automatic welding is small and the welding deformation is controllable, which can effectively avoid problems such as oxidation, burning and deformation of platinum-iridium alloy sealing seat and platinum cylinder during the welding process, thereby ensuring the strength of the welded joint and the overall structural stability, and meeting the sealing performance and service life requirements of high temperature and high pressure reactor under harsh working conditions.

[0042] Specifically, pulsed laser welding or continuous laser welding is selected during the welding stage, and welding is carried out under an argon protective atmosphere: argon can effectively isolate air, prevent oxidation of the weld and base material at high temperatures, and avoid defects such as porosity and cracks in the weld; at the same time, the pulsed / continuous laser mode can adapt to the welding requirements of different wall thicknesses and different structural parts, achieve precise energy input, make the weld penetration uniform and the shape beautiful, ensure that the sealing seat and the platinum cylinder are tightly bonded and the transition is smooth, and greatly improve the uniformity and reliability of the weld.

[0043] The beneficial effects of this invention are as follows: 1. The cylinder body in this invention is made of high-purity platinum, which possesses excellent high-temperature oxidation resistance, corrosion resistance, and high-temperature plasticity. It maintains structural integrity and a clean, uncontaminated internal cavity under high-temperature, high-pressure, and highly corrosive conditions, preventing the introduction of impurities that could affect crystal growth quality. Simultaneously, the sealing seat is made of a platinum-iridium alloy, which, while possessing the excellent corrosion resistance of platinum, significantly enhances the high-temperature strength and hardness of the sealing seat through iridium solid solution strengthening. This ensures the dimensional stability and sealing reliability of the sealing surface during long-term service, preventing deformation, wear, or failure.

[0044] 2. This invention employs a composite structure of "high-strength alloy steel vessel body + high-purity platinum liner + platinum-iridium alloy sealing seat". The outer alloy steel vessel body provides sufficient structural support, ensuring the overall mechanical strength, structural rigidity, and operational safety of the reactor, meeting the pressure-bearing requirements under high temperature and high pressure. The inner high-purity platinum cylinder and platinum-iridium alloy sealing seat constitute a precious metal liner, responsible for functions such as high-temperature oxidation resistance, strong media corrosion resistance, and a high-cleanliness inner cavity. Wherein: The platinum cylinder possesses excellent high-temperature plasticity and chemical stability, which can maintain structural integrity and internal cavity cleanliness for a long time. The platinum-iridium alloy sealing seat, on the basis of corrosion resistance, significantly improves high-temperature strength and hardness, effectively ensuring the dimensional stability and sealing reliability of the sealing surface.

[0045] By adopting the above-mentioned composite structure design, this invention can avoid the high cost of using precious metal materials for the whole process, and overcome the technical problem that a single structural material cannot simultaneously achieve structural support, corrosion resistance and protection and ultra-high purity of the inner cavity. While ensuring service performance under extreme working conditions, it significantly improves the economy and practicality of the overall material, and achieves a synergistic balance between structural strength, corrosion resistance, inner cavity purity and manufacturing cost.

[0046] 3. The noble metal liner prepared by the present invention can provide a growth cavity with ultra-high purity, low pollution and high stability, which can effectively avoid the release of metal ions, oxidation peeling or corrosion products contaminating the crystal. It is particularly suitable for the long-term and stable growth of high-quality, large-size gallium nitride and other semiconductor crystals, which is beneficial to improving the crystal yield and overall performance.

[0047] 4. This invention, from the preparation of 5N grade high-purity platinum powder and precise proportioning of platinum-iridium alloy, to homogenous powder mixing, hot pressing, homogenization treatment, precision CNC machining, directional solidification, multi-pass high-intensity spinning, and argon-protected laser welding, effectively eliminates problems such as component segregation, internal defects, oxidation, and deformation through refined process control throughout the entire process. This ensures that the platinum cylinder and sealing seat have high dimensional accuracy, dense structure, uniform performance, excellent weld formation, and reliable sealing.

[0048] 5. The precious metal liner prepared by this invention has excellent high-temperature oxidation resistance, high-pressure structural stability, and strong medium corrosion resistance. It is not prone to oxidation aging, structural embrittlement, structural deformation, or performance failure under long-term extreme working conditions. At the same time, the uniform and dense weld formed by argon-protected laser welding ensures a firm and reliable sealing structure. It can operate continuously and stably for a long time in high-temperature, high-pressure, and highly corrosive environments without leakage, cracking, or sealing failure. This significantly reduces the frequency of equipment maintenance and the cost of liner replacement, and effectively improves the continuity and stability of crystal growth production. Attached Figure Description

[0049] Figure 1 This is a flowchart illustrating the preparation method of the noble metal liner for the high-temperature and high-pressure reactor of the present invention. Figure 2 Cross-sectional views of the noble metal lining structure of the high-temperature and high-pressure reactor prepared in Examples 1-3; Figure 3 The images show the actual precious metal linings of the high-temperature and high-pressure reactors prepared in Examples 1-3. Detailed Implementation

[0050] like Figure 1 As shown, a method for preparing a noble metal liner for a high-temperature, high-pressure reactor used for gallium nitride crystal growth includes the following steps: 1) Preparation of high-purity platinum powder 1.1) Dissolve platinum raw material with a purity of 99.95% in aqua regia (the aqua regia is prepared by mixing deionized water, concentrated hydrochloric acid and concentrated nitric acid in a volume ratio of 1:4:1) to obtain chloroplatinic acid solution; 1.2) Hydrochloric acid (dilute hydrochloric acid prepared by mixing concentrated hydrochloric acid and deionized water in a volume ratio of 1:1) and 1% sodium chloride solid were added sequentially to the chloroplatinic acid solution to obtain a sodium chloroplatinate solution. 1.3) Add 10% sodium hydroxide solution to sodium chloroplatinate solution, heat to boiling, then add 10% cerium chloride solution and 20% sodium hypochlorite solution in sequence, control the pH of the system to 9-10, precipitate some impurities and filter to obtain clear filtrate. 1.4) Add saturated ammonium chloride solution to the clarified filtrate to obtain ammonium hexachloroplatinate precipitate; 1.5) The ammonium hexachloroplatinate (IV) precipitate was calcined at 700-900℃ for 6-8 hours to obtain 5N grade high-purity platinum powder with a purity ≥99.995%.

[0051] 2) Preparation of sealing seat 2.1) Weigh 70-80 wt% of the high-purity platinum powder obtained in step 1.5) and 20-30 wt% of the high-purity iridium powder with a purity ≥99.99% to prepare the mixture and obtain the platinum-iridium mixed raw material. 2.2) Use a three-dimensional powder mixer or a V-type powder mixer to mix the platinum-iridium mixed raw materials obtained in step 2.1) for 5 to 10 hours to obtain platinum-iridium mixed powder; 2.3) The platinum-iridium mixed powder obtained in step 2.2) is subjected to heat treatment: under a hydrogen atmosphere, the treatment temperature is 800-1000℃ and the treatment time is 3-5h to obtain platinum-iridium alloy powder; 2.4) The platinum-iridium alloy powder obtained in step 2.3) is placed in a graphite hot pressing mold and heated under a vacuum of 1×10⁻⁶. -3 ~9×10 -3 Platinum-iridium alloy ingots were obtained by hot pressing under the conditions of Pa, molding temperature of 1500-1700℃ and molding pressure of 15-25MPa. 2.5) The platinum-iridium alloy ingot obtained in step 2.4) is subjected to a vacuum of 1×10⁻⁶. -3 ~9×10 -3 Homogenization is performed by holding the material at 1400–1600℃ for 4–8 hours, followed by hot forging at 1200–1400℃ for 30–40 minutes to obtain a platinum-iridium alloy forging billet. 2.6) The platinum-iridium alloy forging blank obtained in step 2.5) is precision CNC machined to obtain the sealing seat.

[0052] 3) Preparation of platinum cylinder 3.1) Place the high-purity platinum powder obtained in step 1.5) into a high-purity zirconia crucible, and then place it in a vacuum furnace. Evacuate the furnace to a vacuum level of 1×10⁻⁶. -3 ~9×10 -3 The temperature is raised to 1850–2100℃ for vacuum refining, which is carried out 2–3 times, with each refining time lasting 3–5 minutes. After each refining, the furnace is stopped until the liquid surface solidifies before starting the next refining. After refining, high-purity argon gas with a purity of 99.999% is introduced into the vacuum furnace until the pressure inside the vacuum furnace reaches 90–95 kPa. Then, the ingot is cooled and shaped using a directional solidification process to obtain a platinum ingot. 3.2) Place the platinum ingot obtained in step 3.1) into a heating furnace, hold it at 1000-1200℃ for 30-40 minutes, and then quickly transfer it to a forging press for hot forging to obtain a platinum forging billet; 3.3) The platinum forging billet obtained in step 3.2) is placed in a heating furnace and held at 1000-1200℃ for 20-30 minutes. Then it is quickly transferred to a cold rolling mill for cold rolling to obtain a platinum slab. 3.4) The platinum blank obtained in step 3.3) is integrally formed by multi-pass, multi-stage, high-pressure spinning. The spinning wheel speed is 100-300 r / min and the feed speed is 5-20 mm / min to obtain the platinum cylinder.

[0053] 4) Preparation of precious metal lining Under argon protection, the sealing seat obtained in step 2.6) and the platinum cylinder obtained in step 3.4) are assembled using pulsed laser welding or continuous laser welding in an automated laser welding process to obtain the noble metal liner of the high-temperature and high-pressure reactor for gallium nitride crystal growth.

[0054] The following is an example of the preparation method of the noble metal liner of the high-temperature and high-pressure reactor for gallium nitride crystal growth: Example 1

[0055] A method for preparing a noble metal liner for a high-temperature, high-pressure reactor used for gallium nitride crystal growth includes the following steps: 1) Dissolve 2000g of platinum raw material with a purity of 99.95% in 2L of aqua regia. After dissolution, add dilute hydrochloric acid (prepared by mixing concentrated hydrochloric acid and deionized water in a volume ratio of 1:1) to remove nitrate until no yellow fumes are produced. Then, slowly add 1200g of sodium chloride solid with a mass fraction of 1% to obtain sodium chloroplatinate solution.

[0056] Add 10% sodium hydroxide solution to sodium chloroplatinate solution and adjust the pH to about 1.5. Stop adding sodium hydroxide solution and heat to boiling. Then add 120 ml of 10% cerium chloride solution. Add 20% sodium hypochlorite solution and control the pH of the system to 9-10. Stop adding sodium hypochlorite solution.

[0057] After some impurities were precipitated, the mixture was filtered to obtain a clear filtrate. 15 L of saturated ammonium chloride solution was added to the clear filtrate to obtain ammonium hexachloroplatinate precipitate. The ammonium hexachloroplatinate precipitate was calcined at 800℃ for 6 h to obtain 5N grade high-purity platinum powder with a purity ≥99.995%.

[0058] 2) Weigh 80wt% of the high-purity platinum powder obtained in step 1) and 20wt% of the high-purity iridium powder with a purity ≥99.99% by weight to obtain a platinum-iridium mixed raw material; and mix the platinum-iridium mixed raw material in a three-dimensional powder mixer for 5 hours using a homogenization method to obtain platinum-iridium mixed powder; place the platinum-iridium mixed powder in a hydrogen atmosphere and keep it at a temperature of 800℃ for 3 hours to obtain platinum-iridium alloy powder.

[0059] 3) Plating platinum-iridium alloy powder was placed in a graphite hot press mold and subjected to a vacuum of 1×10⁻⁶. -3~9×10 -3 Platinum-iridium alloy ingots were obtained by hot pressing under the conditions of Pa, molding temperature of 1700℃ and molding pressure of 15MPa.

[0060] 4) The platinum-iridium alloy ingot obtained in step 3) is placed under a vacuum of 1×10⁻⁶. -3 ~9×10 -3 Homogenization was performed by holding the material at 1400℃ for 8 hours, followed by hot forging at 1200℃ for 30 minutes to obtain a platinum-iridium alloy forging billet.

[0061] 5) The platinum-iridium alloy forging blank obtained in step 4) is precision CNC machined to obtain the sealing seat.

[0062] 6) Place the high-purity platinum powder obtained in step 1) into a high-purity zirconium oxide crucible, and then place it in a vacuum furnace. Evacuate the furnace to a vacuum level of 1×10⁻⁶. -3 ~9×10 -3 The temperature is raised to 1850℃ for vacuum refining, which is carried out 2 to 3 times, with each refining time being 3 to 5 minutes. After each refining, the furnace is stopped until the liquid surface solidifies before starting the next refining. After refining, high-purity argon gas with a purity of 99.999% is introduced into the vacuum furnace until the pressure inside the vacuum furnace reaches 90 to 95 kPa. Then, the ingot is cooled and shaped using a directional solidification process to obtain a platinum ingot.

[0063] 7) Place the platinum ingot obtained in step 6) into a heating furnace, hold it at 1000℃ for 30 minutes, cool it and then transfer it to a forging press for hot forging to obtain a platinum forging billet.

[0064] 8) Place the platinum forging billet obtained in step 7) into a heating furnace, hold it at 1000℃ for 20 minutes, and then quickly transfer it to a cold rolling mill for cold rolling to obtain a platinum slab.

[0065] 9) The platinum blank obtained in step 8) is integrally formed by multi-pass, multi-stage, high-pressure spinning. The spinning wheel speed is 300 r / min and the feed speed is 16 mm / min to obtain the platinum cylinder.

[0066] 10) Under argon protection, the sealing seat obtained in step 5) and the platinum cylinder obtained in step 9) are assembled using laser automatic welding to obtain the noble metal liner of the high-temperature and high-pressure reactor for gallium nitride crystal growth (e.g., ...). Figure 2 , Figure 3 (As shown). Example 2

[0067] A method for preparing a noble metal liner for a high-temperature, high-pressure reactor used for gallium nitride crystal growth includes the following steps: 1) Dissolve 2000g of platinum raw material with a purity of 99.95% in 2L of aqua regia. After dissolution, add dilute hydrochloric acid (prepared by mixing concentrated hydrochloric acid and deionized water in a volume ratio of 1:1) to remove nitrate until no yellow fumes are produced. Then, slowly add 1200g of sodium chloride solid with a mass fraction of 1% to obtain sodium chloroplatinate solution.

[0068] Add 10% sodium hydroxide solution to sodium chloroplatinate solution and adjust the pH to about 1.5. Stop adding sodium hydroxide solution and heat to boiling. Then add 120 ml of 10% cerium chloride solution. Add 20% sodium hypochlorite solution and control the pH of the system to 9-10. Stop adding sodium hypochlorite solution.

[0069] After some impurities were precipitated, the mixture was filtered to obtain a clear filtrate. 15 L of saturated ammonium chloride solution was added to the clear filtrate to obtain ammonium hexachloroplatinate precipitate. The ammonium hexachloroplatinate precipitate was calcined at 800℃ for 6 h to obtain 5N grade high-purity platinum powder with a purity ≥99.995%.

[0070] 2) Weigh 75wt% of the high-purity platinum powder obtained in step 1) and 25wt% of the high-purity iridium powder with a purity ≥99.99% to obtain a platinum-iridium mixed raw material; and mix the platinum-iridium mixed raw material in a three-dimensional powder mixer for 8 hours using a homogenization method to obtain platinum-iridium mixed powder; place the platinum-iridium mixed powder in a hydrogen atmosphere and keep it at a temperature of 900℃ for 4 hours to obtain platinum-iridium alloy powder.

[0071] 3) Plating platinum-iridium alloy powder was placed in a graphite hot press mold and subjected to a vacuum of 1×10⁻⁶. -3 ~9×10 -3 Platinum-iridium alloy ingots were obtained by hot pressing under the conditions of Pa, molding temperature of 1600℃ and molding pressure of 20MPa.

[0072] 4) The platinum-iridium alloy ingot obtained in step 3) is placed under a vacuum of 1×10⁻⁶. -3 ~9×10 -3 Homogenization was performed by holding the platinum-iridium alloy billet at 1500℃ for 6 hours, followed by hot forging at 1300℃ for 30 minutes.

[0073] 5) The platinum-iridium alloy forging blank obtained in step 4) is precision CNC machined to obtain the sealing seat.

[0074] 6) Place the high-purity platinum powder obtained in step 1) into a high-purity zirconium oxide crucible, and then place it in a vacuum furnace. Evacuate the furnace to a vacuum level of 1×10⁻⁶. -3 ~9×10 -3The temperature is raised to 1900℃ for vacuum refining, which is carried out 2 to 3 times, with each refining time lasting 3 to 5 minutes. After each refining, the furnace is stopped until the liquid surface solidifies before starting the next refining. After refining, high-purity argon gas with a purity of 99.999% is introduced into the vacuum furnace until the pressure inside the vacuum furnace reaches 90 to 95 kPa. Then, the ingot is cooled and shaped using a directional solidification process to obtain platinum ingots.

[0075] 7) Place the platinum ingot obtained in step 6) into a heating furnace, hold it at 1100℃ for 30 minutes, cool it and then transfer it to a forging press for hot forging to obtain a platinum forging billet.

[0076] 8) Place the platinum forging billet obtained in step 7) into a heating furnace, hold it at 1100℃ for 20 minutes, and then quickly transfer it to a cold rolling mill for cold rolling to obtain a platinum slab.

[0077] 9) The platinum blank obtained in step 8) is integrally formed by multi-pass, multi-stage, high-pressure spinning. The spinning wheel speed is 200 r / min and the feed speed is 12 mm / min to obtain the platinum cylinder.

[0078] 10) Under argon protection, the sealing seat obtained in step 5) and the platinum cylinder obtained in step 9) are assembled using laser automatic welding to obtain the noble metal liner of the high-temperature and high-pressure reactor for gallium nitride crystal growth (e.g., ...). Figure 2 , Figure 3 (As shown). Example 3

[0079] A method for preparing a noble metal liner for a high-temperature, high-pressure reactor used for gallium nitride crystal growth includes the following steps: 1) Dissolve 2000g of platinum raw material with a purity of 99.95% in 2L of aqua regia. After dissolution, add dilute hydrochloric acid (prepared by mixing concentrated hydrochloric acid and deionized water in a volume ratio of 1:1) to remove nitrate until no yellow fumes are produced. Then, slowly add 1200g of sodium chloride solid with a mass fraction of 1% to obtain sodium chloroplatinate solution.

[0080] Add 10% sodium hydroxide solution to sodium chloroplatinate solution and adjust the pH to about 1.5. Stop adding sodium hydroxide solution and heat to boiling. Then add 120 ml of 10% cerium chloride solution. Add 20% sodium hypochlorite solution and control the pH of the system to 9-10. Stop adding sodium hypochlorite solution.

[0081] After some impurities were precipitated, the mixture was filtered to obtain a clear filtrate. 15 L of saturated ammonium chloride solution was added to the clear filtrate to obtain ammonium hexachloroplatinate precipitate. The ammonium hexachloroplatinate precipitate was calcined at 800℃ for 6 h to obtain 5N grade high-purity platinum powder with a purity ≥99.995%.

[0082] 2) Weigh 70wt% of the high-purity platinum powder obtained in step 1) and 30wt% of the high-purity iridium powder with a purity ≥99.99% by weight to obtain a platinum-iridium mixed raw material; and mix the platinum-iridium mixed raw material in a three-dimensional powder mixer for 10 hours using a homogenization powder mixing method to obtain platinum-iridium mixed powder; place the platinum-iridium mixed powder in a hydrogen atmosphere and keep it at a temperature of 1000℃ for 5 hours to obtain platinum-iridium alloy powder.

[0083] 3) Plating platinum-iridium alloy powder was placed in a graphite hot press mold and subjected to a vacuum of 1×10⁻⁶. -3 ~9×10 -3 Platinum-iridium alloy ingots were obtained by hot pressing under the conditions of Pa, molding temperature of 1500℃ and molding pressure of 25MPa.

[0084] 4) The platinum-iridium alloy ingot obtained in step 3) is placed under a vacuum of 1×10⁻⁶. -3 ~9×10 -3 Homogenization was performed by holding the platinum-iridium alloy billet at 1600℃ for 4 hours, followed by hot forging at 1400℃ for 30 minutes.

[0085] 5) The platinum-iridium alloy forging blank obtained in step 4) is precision CNC machined to obtain the sealing seat.

[0086] 6) Place the high-purity platinum powder obtained in step 1) into a high-purity zirconium oxide crucible, and then place it in a vacuum furnace. Evacuate the furnace to a vacuum level of 1×10⁻⁶. -3 ~9×10 -3 The temperature is raised to 1950℃ for vacuum refining, which is carried out 2 to 3 times, with each refining time lasting 3 to 5 minutes. After each refining, the furnace is stopped until the liquid surface solidifies before starting the next refining. After refining, high-purity argon gas with a purity of 99.999% is introduced into the vacuum furnace until the pressure inside the vacuum furnace reaches 90 to 95 kPa. Then, the ingot is cooled and shaped using a directional solidification process to obtain a platinum ingot.

[0087] 7) Place the platinum ingot obtained in step 6) into a heating furnace, hold it at 1200℃ for 30 minutes, cool it and then transfer it to a forging press for hot forging to obtain a platinum forging billet.

[0088] 8) Place the platinum forging billet obtained in step 7) into a heating furnace, hold it at 1200℃ for 20 minutes, and then quickly transfer it to a cold rolling mill for cold rolling to obtain a platinum slab.

[0089] 9) The platinum blank obtained in step 8) is integrally formed by multi-pass, multi-stage, high-pressure spinning. The spinning wheel speed is 100 r / min and the feed speed is 8 mm / min to obtain the platinum cylinder.

[0090] 10) Under argon protection, the sealing seat obtained in step 5) and the platinum cylinder obtained in step 9) are assembled using laser automatic welding to obtain the noble metal liner of the high-temperature and high-pressure reactor for gallium nitride crystal growth (e.g., ...). Figure 2 , Figure 3 (As shown).

[0091] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications made to the present invention by those skilled in the art without departing from the spirit of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for preparing a noble metal liner for a high-temperature, high-pressure reactor used for gallium nitride crystal growth, characterized in that, Includes the following steps: 1) Dissolve platinum raw material with a purity of 99.95% in aqua regia, and add hydrochloric acid and sodium chloride solid in sequence to obtain sodium chloroplatinate solution; add sodium hydroxide solution to sodium chloroplatinate solution, heat to boiling, and then add cerium chloride solution and sodium hypochlorite solution in sequence, controlling the pH of the system to 9-10, filter to obtain clear filtrate; add saturated ammonium chloride solution to clear filtrate to obtain ammonium hexachloroplatinate precipitate; calcine the ammonium hexachloroplatinate precipitate to obtain 5N grade high-purity platinum powder with a purity ≥99.995%; 2) The high-purity platinum powder obtained in step 1) is used to prepare the sealing seat and the platinum cylinder, respectively; 2-1) Weigh 70-80 wt% of the high-purity platinum powder obtained in step 1) and 20-30 wt% of the high-purity iridium powder with a purity ≥99.99% by weight to obtain a platinum-iridium mixed raw material; after homogenization and heat treatment, platinum-iridium alloy powder is obtained. 2-2) The platinum-iridium alloy powder obtained in step 2-1) is hot-pressed to obtain a platinum-iridium alloy ingot; the platinum-iridium alloy ingot is then subjected to homogenization treatment and heat preservation treatment in sequence, and then hot-forged to obtain a platinum-iridium alloy forging blank. 2-3) The platinum-iridium alloy forging blank obtained in step 2-2) is precision CNC machined to obtain the sealing seat; 2-4) The high-purity platinum powder obtained in step 1) is vacuum melted and directionally solidified to obtain platinum ingots; the platinum ingots are hot-forged after a first heat treatment to obtain platinum forging billets; the platinum forging billets are cold-rolled after a second heat treatment to obtain platinum slab billets. 2-5) The platinum blank obtained in step 2-4) is integrally formed by multi-pass, multi-stage, controlled high-pressure spinning. The spinning wheel speed is 100-300 r / min and the feed speed is 5-20 mm / min to obtain the platinum cylinder. 3) The sealing seat and platinum cylinder obtained in step 2) are assembled by laser automatic welding to obtain the noble metal liner of the high temperature and high pressure reactor for gallium nitride crystal growth.

2. The method for preparing the noble metal liner of the reactor according to claim 1, characterized in that, In step 1), the hydrochloric acid is a dilute hydrochloric acid prepared by mixing concentrated hydrochloric acid and deionized water in a volume ratio of 1:1; the mass fraction of the sodium chloride solid is 1%; the mass fraction of the sodium hydroxide solution is 10%; the mass fraction of the cerium chloride solution is 10%; the mass fraction of the sodium hypochlorite solution is 20%; and the calcination method is as follows: the calcination temperature is 700-900℃, and the calcination time is 6-8h.

3. The method for preparing the noble metal liner of the reaction vessel according to claim 1, characterized in that, In step 2-1), the homogenization mixing method is as follows: the powder is mixed using a three-dimensional powder mixer or a V-type powder mixer, and the mixing time is 5 to 10 hours; the heat treatment method is as follows: under a hydrogen atmosphere, the treatment temperature is 800 to 1000℃, and the treatment time is 3 to 5 hours.

4. The method for preparing the noble metal liner of the reaction vessel according to claim 1, characterized in that, In Step 2-2), the hot press forming is performed at a vacuum degree of 1 x 10 -3 ~ 9 x 10 -3 Pa, a forming temperature of 1500 ~ 1700 °C, and a forming pressure of 15 ~ 25 MPa.

5. The method for preparing the noble metal liner of the reaction vessel according to claim 1, characterized in that, In Step 2-2), the homogenization treatment is performed at a vacuum of 1 x 10 -3 ~ 9 x 10 -3 Pa, a treatment temperature of 1400 ~ 1600 °C, and a holding time of 4 ~ 8 h.

6. The method for preparing the noble metal liner of the reaction vessel according to claim 1, characterized in that, In step 2-2), the heat preservation treatment is performed as follows: the heat preservation temperature is 1200-1400℃ and the heat preservation time is 30-40min.

7. The method for preparing the noble metal liner of the reaction vessel according to claim 1, characterized in that, In steps 2-4), the vacuum melting method is as follows: the vacuum degree is 1×10⁻⁶. -3 ~9×10 -3 Pa, refining temperature is 1850~2100℃, refining 2~3 times, and the refining time for each time is 3~5min.

8. The method for preparing the noble metal liner of the reaction vessel according to claim 1, characterized in that, In steps 2-4), the directional solidification method includes: after refining, argon gas with a purity of 99.999% is introduced to maintain the pressure inside the furnace at 90-95 kPa.

9. The method for preparing the noble metal liner of the reaction vessel according to claim 1, characterized in that, In steps 2-4), the first heat preservation treatment is performed at a temperature of 1000-1200℃ for 30-40 minutes; the second heat preservation treatment is performed at a temperature of 1000-1200℃ for 20-30 minutes.

10. In the method for preparing the noble metal liner of the reactor according to claim 1, in step 3), the automatic laser welding process is carried out under argon protection.

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