Preparation method of metal beryllium based on composite reducing agent

Abstract

The invention relates to a preparation method of metal beryllium based on a composite reducing agent. The preparation method comprises the following steps: 1) preparing an aluminum oxide coated magnesium composite reducing agent by adopting an in-situ chemical precipitation method; the preparation method comprises the following steps of (1) preparing a composite reducing agent, (2) mixing: mixing the composite reducing agent obtained in the step (1) with beryllium fluoride powder, (3) carrying out temperature programming reduction: carrying out two-stage temperature programming reduction in an inert atmosphere to obtain crude beryllium, (4) carrying out high-temperature vacuum refining, and (5) carrying out densification treatment.The preparation method can synchronously realize a metal beryllium product with the direct recovery rate gt of the beryllium and the purity gt of 82% and the purity gt of 99% on the premise of ensuring safety (no splashing).

Description

Technical Field

[0001] This invention belongs to the field of non-ferrous metal metallurgy technology, specifically relating to a method for preparing beryllium metal by magnesium thermal reduction, and particularly to a method for achieving controllable and efficient reduction by using a composite reducing agent. Background Technology

[0002] Beryllium metal plays an irreplaceable role in aerospace, nuclear energy, and high-end instrumentation due to its low density, high modulus, excellent nuclear properties, and thermal stability. Currently, industrial production of beryllium metal primarily employs the magnesothermic reduction method, which involves reducing beryllium fluoride with metallic magnesium. The basic reaction is: BeF₂ + Mg → Be + MgF₂. However, the traditional high-temperature reduction process involving direct mixing of magnesium and beryllium fluoride has the following drawbacks: 1) When molten beryllium fluoride comes into contact with solid or liquid magnesium, the reaction is instantaneous, accompanied by intense exothermic reactions, boiling, and a large amount of magnesium vapor splashing. This not only causes severe thermal and physical shock to production equipment, reducing its lifespan, but also poses a significant safety hazard. 2) The intense splashing and uncontrolled volatilization of magnesium vapor result in a large amount of metallic magnesium being lost without effective reduction; the direct beryllium recovery rate is typically only 60%–70%, leading to raw material waste and increased production costs. 3) Vigorous reaction stirring easily corrodes the crucible material, allowing impurities (such as Fe, Si, and Al) to enter the molten metal. Meanwhile, splashing may cause unreacted beryllium fluoride or slag to be trapped within the metallic beryllium, affecting the purity and homogeneity of the final product. 4) The reaction process is violent and rapid, making it difficult to precisely control using conventional methods, which is detrimental to the standardization of the production process and the stability of product batches.

[0003] To address the aforementioned issues, existing technologies (such as CN113059154B) use magnesium granules instead of magnesium ingots to increase the contact area or optimize the heating curve. However, these improvements often only treat the symptoms, failing to fundamentally change the nature of the vigorous reaction and magnesium volatilization. Therefore, there is an urgent need for a technology that innovates the reaction mechanism to achieve stable, efficient, and high-purity preparation of beryllium metal. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing magnesothermic reduction methods, such as violent reactions, low magnesium utilization, easy product contamination, and uncontrollable processes, and to provide a novel method for preparing metallic beryllium. This method, through the design and application of a composite reducing agent and combined with optimized process procedures, aims to achieve a mild and controllable reduction process, efficient utilization of the reducing agent, improved product purity, and a substantial increase in production safety.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for preparing metallic beryllium based on a composite reducing agent includes the following steps:

[0007] 1) Preparation of alumina-coated magnesium composite reducing agent: An alumina coating layer is deposited on the surface of magnesium powder in situ using an in-situ chemical precipitation method. This coating layer can increase the mass transfer resistance in the early stage of the reduction reaction, provide physical isolation, and alleviate the violent reaction of magnesium.

[0008] Step 1) The preparation method of the alumina-coated magnesium composite reducing agent specifically includes:

[0009] a. Disperse magnesium powder in ethanol, and under the protection of an inert atmosphere at 50~70℃, slowly add an ethanol solution of aluminum chloride and an ethanol solution of ammonia water, so that aluminum hydroxide is precipitated in situ on the surface of magnesium powder.

[0010] b. After precipitation, the precursor powder is obtained by washing and vacuum drying;

[0011] c. The precursor powder is heated to 400-500℃ in a dry, inert atmosphere at a rate of 2-5℃ / min and held for 1-2 hours to convert aluminum hydroxide into aluminum oxide, thus obtaining an aluminum oxide-coated magnesium composite reducing agent.

[0012] Further, in step a, magnesium powder is dispersed in anhydrous ethanol at a solid-liquid ratio (mass / volume) of 1 g: (10~20) mL.

[0013] Furthermore, in step a, the magnesium powder has a particle size of <150μm and a purity of ≥99.5%.

[0014] Further, in step a, the concentration of the aluminum chloride ethanol solution is 0.05~0.20 mol / L.

[0015] Furthermore, in step a, the ratio of aluminum chloride to magnesium powder is calculated according to the molar ratio of aluminum to magnesium (0.05~0.15):1.

[0016] Further, in step a, the dropping rate is 0.5~3.0 mL / min.

[0017] Furthermore, in step a, the Al content in aluminum chloride is controlled. 3+ The molar ratio with ammonia (calculated as NH3) is approximately 1:(3~4) to ensure sufficient precipitation of aluminum hydroxide.

[0018] Furthermore, in step a, after the addition is complete, continue aging for 1-2 hours.

[0019] Furthermore, in step a, the inert atmosphere is nitrogen or argon.

[0020] Furthermore, in step b, the vacuum drying temperature is 60~80℃.

[0021] Optionally, before step a, the magnesium powder may be pretreated by ultrasonically cleaning it in an anhydrous ethanol solution of 0.05-0.20 mol / L acetic acid for 2-5 minutes, washing it with anhydrous ethanol and vacuum drying it to remove the surface oxide layer and restore its activity.

[0022] While other methods, such as atomic layer deposition, can also prepare coating structures, their high cost makes them unsuitable for large-scale metallurgical applications. The chemical precipitation method provided in this invention achieves an optimized balance between cost and performance while maintaining functionality.

[0023] 2) Mixing: In an inert atmosphere, the composite reducing agent from step 1) is mixed with beryllium fluoride powder, and then the mixture is loaded into the reactor;

[0024] Furthermore, the purity of the beryllium fluoride powder is ≥99.5%, preferably ≥99.8%.

[0025] Furthermore, the molar ratio of magnesium in the composite reducing agent to beryllium in beryllium fluoride is (1.1~1.4):1.

[0026] Furthermore, the inert atmosphere is nitrogen or argon.

[0027] Furthermore, the content of active magnesium in the composite reducing agent can be determined by acid hydrolysis.

[0028] Furthermore, the mass fraction of active magnesium in the composite reducing agent is >93%.

[0029] 3) Programmed temperature reduction: Under an inert atmosphere, the mixture is reduced in two stages to obtain crude beryllium.

[0030] The two-stage temperature rise process includes:

[0031] 3.1 Low-temperature reduction stage: First, raise the temperature to 650~800℃ at a rate of 5~10℃ / min and hold for 20~40 minutes;

[0032] 3.2 High-temperature reduction stage: Then, raise the temperature to 1250~1350℃ at a rate of 15~25℃ / min and hold for 60~120 minutes.

[0033] Furthermore, the pressure conditions for the low-temperature reduction stage are 0.02~0.05 MPa; the pressure for the high-temperature reduction stage can be atmospheric pressure or 0.05~0.10 MPa.

[0034] Furthermore, in the low-temperature reduction stage (650–800℃), the alumina layer coating the magnesium powder surface remains solid, acting as a physical barrier to prevent direct contact between the internal active magnesium and the external molten beryllium fluoride, thus avoiding a violent, instantaneous reaction at its source. This stage employs a slow heating rate, combined with a slightly positive pressure inert atmosphere, to stabilize the system and inhibit premature volatilization of components, providing a foundation for a smooth transition in subsequent reactions. In the high-temperature reduction stage (1250–1350℃), the alumina layer is gradually broken down and loosened, allowing the internal magnesium to diffuse and undergo an interfacial reduction reaction with the beryllium fluoride. This transforms the violent direct reaction into a mild and controllable diffusion reaction process, and the rapid heating helps to overcome the intermediate unstable temperature zone, guiding the reaction to proceed in a controlled diffusion mode. Finally, the magnesium fluoride slag and alumina slag are cooled and separated to obtain crude beryllium.

[0035] 4) High-temperature vacuum refining: at a vacuum degree ≤ 1.0 × 10 -2 Hold at 1300~1400℃ for 30~120 minutes, then cast into ingots; preferably, the rough product is prepared at 1300~1350℃ with a vacuum degree ≤5.0×10⁻⁶. -3 Hold at Pa for 40-60 minutes, then cast into ingots.

[0036] 5) Densification treatment: Densified metallic beryllium material is obtained by hot isostatic pressing or hot pressing process.

[0037] Furthermore, step 5) includes a crushing step before densification.

[0038] Furthermore, the crushing process involves first crushing the beryllium ingots using a hydraulic press, and then using airflow pulverization to obtain angular beryllium powder.

[0039] Furthermore, the initial crushing pressure is 50~200 MPa, crushing the material into fragments with a particle size of less than 10 mm. The air jet milling uses a high-pressure inert gas (such as argon or nitrogen, pressure 0.7~1.2 MPa) as the medium to pulverize the coarse fragments into fine powder in an air jet mill.

[0040] Furthermore, the hot isostatic pressing is performed at a temperature of 950~1050℃ and a pressure of 100~150 MPa for 1~3 hours.

[0041] Furthermore, the hot pressing temperature is 1000~1100℃, the pressure is 20~50 MPa, and the pressure is maintained for 1~2 hours.

[0042] The beneficial effects of this invention are:

[0043] 1. This invention develops an alumina-coated magnesium composite reducing agent. By utilizing the physical barrier of the alumina layer, it reacts with magnesium reducing agent and beryllium fluoride target raw material. Through a staged heating process, the violent solid-liquid reaction is transformed into a mild diffusion reaction, providing a new solution for the safe and efficient smelting of metallic beryllium.

[0044] 2. This invention employs a specific composite reducing agent to develop a segmented reduction reaction process. First, in the low-temperature reduction stage (650-800℃), the alumina coating on the magnesium powder surface acts as a stable solid physical barrier, effectively preventing direct contact between the internal active magnesium and the external molten beryllium fluoride, thus preventing a violent, instantaneous reaction. Subsequently, in the high-temperature reduction stage (1250-1350℃), the alumina layer is controllably removed, and magnesium gradually undergoes a reduction reaction with beryllium fluoride through diffusion, transforming the violent direct reaction into a mild and controllable process. This ensures the entire reduction reaction proceeds smoothly, eliminating the risks of splashing and boiling over, and achieving a safe and controllable production process.

[0045] 3. The entire reaction process of this invention is mild and controllable, and the unnecessary loss of active magnesium metal caused by violent boiling and splashing is greatly reduced. The direct recovery rate of beryllium can be stably increased from 60-70% to over 80%, reducing material consumption.

[0046] 4. The alumina barrier layer introduced in this invention can enter the slag phase at high temperatures and be removed through subsequent slag separation and vacuum refining without introducing additional impurities. The entire process avoids traditional chemical purification methods, shortens the process flow, reduces waste, and ultimately yields a beryllium product with a high beryllium content. Attached Figure Description

[0047] Figure 1 Photograph of the beryllium rod, the final product of this invention. Detailed Implementation

[0048] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0049] Preparation and characterization of composite reducing agent in Example 1

[0050] Raw material pretreatment: Take spherical magnesium powder (particle size 100 μm), ultrasonically clean it with 0.15 mol / L acetic acid in anhydrous ethanol solution for 3 minutes, then wash it with anhydrous ethanol and vacuum dry it at 70℃ for 4 hours to obtain 20g of activated magnesium powder.

[0051] In-situ precipitation coating:

[0052] a. Weigh 13.9 g of AlCl3·6H2O and dissolve it in anhydrous ethanol to obtain an AlCl3 ethanol solution with a concentration of 0.15 mol / L (solution A). Measure 13.4 mL of concentrated ammonia (25%) and dilute it to 380 mL with anhydrous ethanol, then mix thoroughly (solution B).

[0053] Add activated magnesium powder and 300 mL of anhydrous ethanol to a 2 L three-necked flask (solid-liquid ratio 1 g:15 mL), and stir at 60 °C under nitrogen protection. Simultaneously add 384 mL of solution A and 380 mL of solution B at a rate of 1.5 mL / min (controlling the aluminum-magnesium molar ratio to approximately 0.07:1; ammonia water is calculated as NH3 and added to Al). 3+ (Molar ratio approximately 3.2:1), after the addition is complete, continue stirring for 2 hours.

[0054] b. The reaction products are separated by centrifugation and washed with ethanol (until no Cl- is detected). - (Detected), the obtained solid was vacuum dried at 75°C for 18 hours to obtain the precursor.

[0055] c. The precursor powder is placed in a muffle furnace and heated to 450°C at a rate of 3°C / min under a dry, inert atmosphere, and held for 2 hours. After cooling, an alumina-coated magnesium composite reducing agent is obtained.

[0056] Verification of the composite reducing agent:

[0057] Take three identical beakers and add 30 mL of 1.0 mol / L dilute hydrochloric acid to each beaker.

[0058] Experimental group: 1.0g of alumina-coated magnesium composite reducing agent was added to the first beaker. In the initial 20-40 seconds, almost no obvious bubbles were visible, or only a very small number of sparse bubbles slowly emerged. Afterward, bubble formation gradually became more obvious and continuous, the entire reaction process was gradual, and the total reaction time lasted 3-5 minutes.

[0059] The total amount of hydrogen produced by the acidolysis reaction indicates that the mass fraction of active magnesium in the composite reducing agent is 94.0%.

[0060] Control group 1: 1.0g of activated magnesium powder was added to the second beaker for acid hydrolysis experiment. Immediately upon addition of the magnesium powder, a large number of vigorous and continuous bubbles were generated, indicating a violent reaction that ended within 1 minute, with the number of bubbles rapidly decreasing.

[0061] Control group 2: 0.94g of activated magnesium powder and 0.06g of alumina powder were added to the third beaker for acid hydrolysis experiment. Continuous and vigorous bubble generation was observed from the start of the reaction. Although slightly weaker than the control group 1 with pure magnesium powder, it was still significantly faster than the experimental group. The total reaction time was approximately 2 minutes, indicating that simple physical mixing cannot fully achieve an effective sustained-release effect.

[0062] The acidolysis experiments described above demonstrate that the alumina-coated magnesium composite reducing agent prepared in this invention exhibits significant slow-release characteristics, with a complete reaction time approximately 3 to 5 times that of ordinary activated magnesium powder, effectively avoiding instantaneous and violent exothermic reactions and gas bursts. This characteristic can be transferred to high-temperature magnesothermic reduction systems, suppressing premature volatilization and violent splashing of magnesium during beryllium fluoride reduction, thereby improving the direct yield of beryllium, product purity, and process safety. This provides a key material basis for achieving controllable, stable, and efficient preparation of metallic beryllium.

[0063] Synthesis example 2

[0064] Raw material pretreatment: Weigh spherical magnesium powder (particle size 100μm), ultrasonically clean it with 0.10 mol / L acetic acid in anhydrous ethanol solution for 4 minutes, wash it three times with anhydrous ethanol, and vacuum dry it at 75℃ for 5 hours to obtain 15g of activated magnesium powder.

[0065] In-situ precipitation coating:

[0066] a. Weigh 17.9 g of AlCl3·6H2O and dissolve it in 370 mL of anhydrous ethanol to obtain an AlCl3 ethanol solution with a concentration of 0.2 mol / L (solution A). Measure 15.8 mL of concentrated ammonia (25%), dilute it to 370 mL with anhydrous ethanol, mix well, and use it as the precipitant solution (solution B).

[0067] b. Add activated magnesium powder and 270 mL of anhydrous ethanol (solid-liquid ratio 1:18) to a 2 L three-necked flask and stir at 65 °C under nitrogen protection. Simultaneously add 370 mL of solution A and 370 mL of solution B dropwise at a rate of 2 mL / min. Control the aluminum-magnesium molar ratio to be approximately 0.12:1, and the ammonia (calculated as NH3) to Al³⁺ molar ratio to be approximately 3.2:1. After the addition is complete, continue stirring for 2 hours.

[0068] c. The reaction products were separated by centrifugation and washed with ethanol until no Cl- was detected. - The obtained solid was vacuum dried at 80℃ for 20 hours to obtain precursor powder. The precursor powder was placed in a muffle furnace and heated to 450℃ at 3℃ / min in a dry inert atmosphere and held for 2 hours. After cooling, an alumina-coated magnesium composite reducing agent was obtained.

[0069] Acid hydrolysis experiment: 1.0 g of the composite reducing agent was added to 30 mL of 1.0 mol / L dilute hydrochloric acid. A significant reaction lag was observed; no obvious bubbles were observed within the first 30 seconds, and the complete reaction time was approximately 5 minutes. Based on the total amount of hydrogen, the active magnesium mass fraction was calculated to be 94.5%.

[0070] Example 1

[0071] (1) Preparation of composite reducing agent: The composite reducing agent was prepared by the method of Synthesis Example 1.

[0072] (2) Mixing: 155.0g of magnesium composite reducing agent coated with alumina, including about 145.7g of active magnesium (about 5.99mol) and 244.2g of beryllium fluoride (purity ≥99.9%, about 5.2mol), are mixed evenly in an argon glove box.

[0073] (3) Programmable temperature reduction: The mixture is loaded into a vacuum induction furnace, evacuated to 10 Pa, and then filled with high-purity argon gas to a pressure of 0.03 MPa.

[0074] The first stage of low-temperature reduction: the temperature is increased to 750℃ at a rate of 8℃ / min and held for 30 minutes; the low-temperature reduction process is stable, and the pressure inside the furnace is maintained at 0.03~0.04 MPa; the process is stable, with no splashing or pressure fluctuations.

[0075] The second stage involved high-temperature reduction: the temperature was increased to 1300℃ at a rate of 20℃ / min and held for 90 minutes, with the pressure adjusted to 0.08 MPa. The reaction proceeded smoothly without any splashing. After the process, cooling yielded approximately 40.5 g of crude beryllium product. Chemical analysis revealed a beryllium content of 97.2% and trace impurities. The actual yield of pure beryllium was approximately 39.4 g, the theoretical beryllium yield was 46.9 g, and the calculated direct beryllium recovery rate was 83.9%.

[0076] (4) High-temperature vacuum refining: crude product at 1350℃, vacuum degree ≤5×10 -3 The solution is kept at a temperature of 60 Pa for 60 minutes, and then cast into ingots.

[0077] (5) Densification treatment: First, use a hydraulic press to crush the beryllium ingot to a particle size of less than 5 mm under a pressure of about 100 MPa; then use an air jet mill with high-purity argon gas of 0.9 MPa as the medium to crush the fragments into angular beryllium powder with an average particle size of about 40~50 μm.

[0078] Hot isostatic pressing (HIP) densification: Beryllium powder is packed into a soft steel sleeve, vacuum-sealed, and then placed in a hot isostatic pressing (HIP) apparatus. The pressure is maintained at 1010℃ and 135 MPa for 2 hours. After cooling, the sleeve is removed to obtain high-density beryllium rods. The final product, beryllium rods, is shown below. Figure 1As shown in the image. Testing revealed a beryllium content of 99.5%.

[0079] Example 2

[0080] (1) Preparation of composite reducing agent: The composite reducing agent was prepared by the method of Synthesis Example 1.

[0081] (2) Mixing: Weigh 155.0g of composite reducing agent powder (approximately 145.7g of active magnesium, 5.99 mol) and 244.2g of beryllium fluoride (approximately 5.2 mol) and mix them evenly in an argon glove box.

[0082] (3) Programmable temperature reduction: The mixture is loaded into a vacuum induction furnace, evacuated and then filled with argon gas to 0.04 MPa.

[0083] The first stage of low-temperature reduction involved heating to 650°C at a rate of 5°C / min and holding at that temperature for 40 minutes, while maintaining the pressure at 0.04~0.05 MPa. The process was relatively stable and gentle, and no splashing was observed.

[0084] The second stage involved high-temperature reduction: the temperature was increased to 1250℃ at a rate of 15℃ / min and held for 120 minutes at a pressure of 0.05MPa. The reaction proceeded smoothly without any splashing. After cooling, 39.8g of crude beryllium was obtained. Chemical analysis of the sample revealed a beryllium content of 96.8% in the product, resulting in a direct beryllium recovery rate of 82.1%.

[0085] (4) High-temperature vacuum refining: The process is the same as in Example 1.

[0086] (5) Densification treatment: First, use a hydraulic press to crush the beryllium ingot to a particle size of less than 5 mm under a pressure of about 100 MPa; then use an air jet mill with high-purity argon gas of 0.9 MPa as the medium to crush the fragments into angular beryllium powder with an average particle size of about 40~50 μm.

[0087] Hot pressing densification: Beryllium powder is packed into a stainless steel sleeve, vacuum sealed, and then placed in a hot press furnace and held at 1050℃ and 50MPa for 2 hours. After cooling, the sleeve is removed, and finally a metallic beryllium rod with a beryllium content of 99.3% is produced.

[0088] Example 3

[0089] (1) Preparation of composite reducing agent: The composite reducing agent was prepared by the method of Synthesis Example 1.

[0090] (2) Mixing: Mix 155.0g of composite reducing agent powder (containing about 145.7g of active magnesium, about 5.99 mol) and 244.2g of beryllium fluoride (about 5.20 mol) evenly in an argon glove box.

[0091] (3) Programmable temperature reduction: The mixture is loaded into a vacuum induction furnace, evacuated and then filled with argon gas to 0.02 MPa.

[0092] First stage low-temperature reduction: heat up to 800℃ at a relatively fast rate of 10℃ / min, hold for 20 minutes, and apply pressure of 0.02~0.03 MPa.

[0093] The second stage involved high-temperature reduction: the temperature was increased to 1350℃ at a rate of 25℃ / min and held for 60 minutes at atmospheric pressure (0.1 MPa). The entire reaction process was stable, with no splashing observed. After cooling, 41.2 g of crude beryllium product was obtained. A sample was taken for chemical analysis, and the beryllium content in the product was found to be 97.3%, with a calculated direct beryllium recovery rate of approximately 85.4%.

[0094] (4)-(5) The processing procedure is the same as in Example 1, and finally a metal beryllium rod with a beryllium content of 99.4% is produced.

[0095] Example 4

[0096] (1) Preparation of composite reducing agent: The same process as in synthesis example 2 was used (Al:Mg molar ratio 0.12:1).

[0097] (2) Mixing: Weigh 165.0g of the composite reducing agent powder (containing about 156.0g of active magnesium, about 6.42 mol) and 273.0g of beryllium fluoride (about 5.81 mol) and mix them evenly in an argon glove box.

[0098] (3) Programmable temperature reduction: The mixture is loaded into a vacuum induction furnace, evacuated to 10 Pa, and then filled with high-purity argon gas to a pressure of 0.025 MPa.

[0099] First stage: Low-temperature reduction. The temperature was increased to 720℃ at a rate of 6℃ / min and held for 35 minutes. The pressure inside the furnace was stabilized at 0.025~0.035 MPa. The process was smooth, without splashing or drastic pressure fluctuations.

[0100] The second stage involved high-temperature reduction: the temperature was increased to 1320℃ at a rate of 18℃ / min and held for 80 minutes. The furnace pressure was adjusted to 0.065 MPa. The entire reaction process was stable and controllable, with no observed splashing or large amounts of smoke or dust. After the reaction was completed and cooled, 45.4 g of crude beryllium product was obtained. Sampling analysis showed that the beryllium content in the product was 97.0%, and the calculated direct beryllium recovery rate was 84.1%.

[0101] (4)-(5) The processing procedure is the same as in Example 1, and finally a metal beryllium rod with a beryllium content of 99.3% is produced.

[0102] Comparative Example 1: Magnesium powder + two-stage heating

[0103] (1) Mixing: In an argon glove box, weigh the following materials and mix them evenly to make them consistent with those in Example 1: 145.7 g (about 5.99 mol) of active magnesium powder and 244.2 g (about 5.20 mol) of beryllium fluoride obtained by the pretreatment method in Synthesis Example 1.

[0104] (2) Two-stage heating reduction: Same as in Example 1.

[0105] During the heating process, when the furnace temperature reached approximately 680℃, the pressure surged dramatically, exceeding 0.15 MPa within 10 seconds, triggering a brief activation of the safety pressure relief device. Simultaneously, noticeable material splashing and impact sounds, along with slight vibrations, accompanied the pressure peak. The pressure then rapidly decreased. The furnace remained calm during the holding phase. The entire reaction was completed rapidly in the early stages of heating. After cooling, the total mass of beryllium product after stripping was 34.1 g. Sampling analysis revealed a beryllium content of 95.8%, with a high impurity content. The calculated direct beryllium recovery rate was 69.7%.

[0106] (3) High-temperature vacuum refining - (4) Densification treatment steps: Same as the corresponding treatment steps in Example 1. After testing, a metallic beryllium rod with a beryllium content of 98.5% was finally obtained.

[0107] Comparative Example 2: Composite reducing agent + single-stage heating

[0108] (1) Mixing: Use the same materials and proportions as in Example 1.

[0109] (2) Single-stage heating and reduction: The mixture is loaded into a vacuum induction furnace, evacuated to 10 Pa, and then filled with high-purity argon gas to a pressure of 0.03 MPa. The temperature is directly increased to 1300℃ at a programmed rate of 20℃ / min, and then held for 90 minutes.

[0110] The heating rate was relatively fast, and the reaction was relatively stable in the initial stage. However, when the temperature reached approximately 750-800°C, the pressure inside the furnace fluctuated significantly several times, accompanied by intermittent slight noises, presumably due to a small-scale reaction caused by the concentrated release of magnesium resulting from localized rupture of the coating layer. The severe splashing seen in Comparative Example 1 did not occur, but the process stability was significantly worse than in Example 1. After the reaction ended and cooling was performed, approximately 38.3 g of crude beryllium was obtained. Sampling analysis revealed that the beryllium content in the product was 96.4%, and the calculated direct beryllium recovery rate was 78.7%.

[0111] (3) High-temperature vacuum refining and (4) densification treatment steps: the same as the corresponding treatment steps in Example 1. The final product was found to have a beryllium content of 99.1%.

[0112] Comparative Example 3: Simple mixture of Mg and alumina, two-stage

[0113] (1) Mixing: In an argon glove box, 145.7 g of active magnesium powder (approximately 5.99 mol) obtained by the pretreatment method in Synthesis Example 1 was mixed with an equal amount of nano-alumina powder (approximately 50 nm in particle size) according to the theoretical content of alumina in the composite reducing agent (approximately 9.3 g). The active magnesium powder, alumina powder and 244.2 g of beryllium fluoride (approximately 5.20 mol) were physically mixed evenly.

[0114] (2) Two-stage heating reduction: The heating procedure is the same as in Example 1.

[0115] Stage 1: After heating to approximately 650℃, the pressure inside the furnace began to rise continuously and rapidly, exceeding 0.1 MPa within minutes, accompanied by intermittent popping sounds and significant splashing, making pressure control difficult. After cooling, approximately 35.6 g of crude beryllium product was obtained. Sample analysis showed a beryllium content of 95.6% and a direct beryllium recovery rate of 72.6%.

[0116] (3) High-temperature vacuum refining and (4) densification treatment steps: the same as the corresponding treatment steps in Example 1. The final product was found to have a beryllium content of 98.7%.

[0117] Comparative Example 4: Magnesium powder + single-stage

[0118] (1) Mixing: In an argon glove box, 145.7 g (about 5.99 mol) of active magnesium powder obtained by the pretreatment method of Synthesis Example 1 was mixed evenly with 244.2 g (about 5.20 mol) of beryllium fluoride.

[0119] (2) Single-stage heating and reduction: The mixture is loaded into the furnace and argon is introduced to 0.03 MPa; the temperature is directly increased to 1300℃ at a rate of 20℃ / min and held for 90 minutes.

[0120] In the initial stage of heating, the reaction started violently, with the pressure instantly soaring to over 0.2 MPa, and the safety valve continuously depressurized. Severe splashing and violent vibration occurred inside the furnace. The high-temperature stage of the reaction was essentially complete. After cooling, the obtained beryllium product was loose and contained severe inclusions, with 32.1 g of crude beryllium product. Analysis showed that the beryllium content was 95.9%, and the direct beryllium recovery rate was 65.6%.

[0121] (3) High-temperature vacuum refining and (4) densification treatment steps: the same as the corresponding treatment steps in Example 1. The beryllium content of the final product was tested to be 98.8%.

[0122] The results of each embodiment and comparative example are shown in Table 1.

[0123] Table 1

[0124]

[0125] Note: Direct beryllium recovery rate = (crude beryllium mass × beryllium content) / theoretical beryllium mass × 100%, where theoretical beryllium mass is calculated based on the complete reduction of beryllium in beryllium fluoride.

[0126] Table 1 shows the advantages of the synergistic process of "alumina-coated magnesium composite reducing agent" and "two-stage programmed temperature rise" in this invention: Examples 1-4 used a composite reducing agent, and all reactions were "stable and without splashing," achieving intrinsic safety. In contrast, Comparative Example 1, using ordinary magnesium powder, experienced violent splashing and pressure impact at 680℃, proving that the alumina coating layer, as a physical barrier, prevents magnesium from instantaneously contacting molten beryllium fluoride directly at the source, which is the core of ensuring safety.

[0127] Furthermore, Examples 1-4 all employed a two-stage reduction design involving low-temperature and high-temperature processes, ensuring complete controllability of the reaction. In Comparative Example 2, a single-stage rapid heating method resulted in the rapid destruction of the alumina barrier layer, and pressure fluctuations and abnormal noises occurred in the 750-800°C range. This demonstrates the crucial role of the two-stage procedure in controlling the initiation of the coating layer reaction and achieving a smooth transition.

[0128] Meanwhile, Examples 1-4, which employed an alumina-coated magnesium composite reducing agent in conjunction with a two-stage programmed temperature rise, achieved a beryllium direct recovery rate exceeding 82%, a crude product purity of 96.8%-97.3%, and a final product beryllium content exceeding 99.3%, while ensuring reaction stability. Their overall performance was significantly superior to the comparative examples. This indicates that the in-situ formed alumina coating layer and the stepwise temperature control strategy effectively synergistically achieved precise control of the intense magnesium thermal reduction reaction. In contrast, the single-stage process using the composite reducing agent (Comparative Example 2, direct recovery rate 78.7%), the two-stage process using ordinary magnesium powder (Comparative Example 1, direct recovery rate 69.7%), the simple physical mixing of alumina and magnesium powder (Comparative Example 3, direct recovery rate 72.6%), and the single-stage process using ordinary magnesium powder (Comparative Example 4, direct recovery rate 65.6%) were far less effective than Examples 1-4. This further confirms that the dense and uniform coating structure formed in situ and the two-stage programmed temperature rise are crucial for achieving effective physical isolation and slow reaction release.

[0129] In summary, this invention, through the organic combination of "alumina-coated magnesium composite reducing agent" and "two-stage programmed temperature reduction," and by controlling the timing of low-temperature isolation and stability combined with high-temperature rapid transition, avoids chain-like runaway reactions caused by local defects in the coating layer. It successfully overcomes the long-standing technical challenges of violent reactions, low direct yield, and poor safety in beryllium production via the magnesian thermal reduction method, and provides a safe, efficient, and high-quality new route for the preparation of metallic beryllium.

[0130] The above-described embodiments are merely specific implementations of the present invention, used to illustrate the technical solutions of the present invention, and are not intended to limit it. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments within the scope of the technology disclosed in the present invention, or make equivalent substitutions for some of the technical features; and these modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of protection of the claims.

Claims

1. A method for preparing metallic beryllium based on a composite reducing agent, characterized in that, Includes the following steps: 1) Preparation of alumina-coated magnesium composite reducing agent: An alumina coating layer is deposited in situ on the surface of magnesium powder using an in-situ chemical precipitation method; 2) Mixing: Mix the composite reducing agent from step 1) with beryllium fluoride powder; 3) Programmed temperature reduction: Under an inert atmosphere, a two-stage programmed temperature reduction was used to obtain crude beryllium; 4) High-temperature vacuum refining: at a vacuum degree ≤ 1.0 × 10 -2 Hold at 1300~1400℃ for 30~120 minutes, then cast into ingots; 5) Densification treatment: Densified metallic beryllium material is obtained by hot isostatic pressing or hot pressing process.

2. The method according to claim 1, characterized in that, Step 1) includes the following steps: a. Disperse magnesium powder in ethanol, and under the protection of 50~70℃ and an inert atmosphere, simultaneously add an ethanol solution of aluminum chloride and an ethanol solution of ammonia water to cause aluminum hydroxide to precipitate in situ on the surface of magnesium powder. b. After precipitation, the precursor powder is obtained by washing and vacuum drying; c. The precursor powder is heated to 400-500℃ in a dry inert atmosphere at a rate of 2-5℃ / min and held for 1-2 hours to obtain an alumina-coated magnesium composite reducing agent.

3. The method according to claim 2, characterized in that, In step a, magnesium powder is dispersed in anhydrous ethanol at a solid-liquid ratio of 1 g: (10~20) mL; the ratio of aluminum chloride to magnesium powder is based on the molar ratio of aluminum to magnesium of (0.05~0.15):

1.

4. The method according to claim 2, characterized in that, In step a, the concentration of the aluminum chloride ethanol solution is 0.05~0.20 mol / L; the dropping rate is 0.5~3.0 mL / min.

5. The method according to claim 1, characterized in that, Step 2) The molar ratio of magnesium in the composite reducing agent to beryllium in beryllium fluoride is (1.1~1.4):

1.

6. The method according to claim 1, characterized in that, The two-stage temperature ramp-up described in step 3) includes: 3.1 Low-temperature reduction stage: First, raise the temperature to 650~800℃ at a rate of 5~10℃ / min and hold for 20~40 minutes; 3.2 High-temperature reduction stage: Heat to 1250~1350℃ at a rate of 15~25℃ / min and hold for 60~120 minutes.

7. The method according to claim 6, characterized in that, The pressure conditions for the low-temperature reduction stage are 0.02~0.05 MPa; the pressure for the high-temperature reduction stage is atmospheric pressure or 0.05~0.10 MPa.

8. The method according to claim 1, characterized in that, It also includes step 5), where the temperature of the hot isostatic pressing is 950~1050℃, the pressure is 100~150MPa, and the pressure is held for 1~3 hours; and the temperature of the hot pressing is 1000~1100℃, the pressure is 20~50MPa, and the pressure is held for 1~2 hours.

9. The method according to claim 8, characterized in that, Step 5 also includes a crushing step.

10. The method according to claim 9, characterized in that, The crushing process first involves pre-crushing the beryllium ingot, and then using airflow pulverization to obtain angular beryllium powder.

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