A method and apparatus for producing high purity zinc arsenide by multiphase reduction-melt alloying

Abstract

The application provides a preparation method and device of high-purity zinc arsenide by multiphase reduction-melt alloying, and belongs to the technical field of inorganic compound synthesis. The method uses arsenic trichloride as an arsenic source, volatilizes the arsenic trichloride by precise temperature control, and transports AsCl3 vapor to a reactor containing high-purity liquid zinc by using high-purity inert gas as a carrier gas; at a set reaction temperature, the liquid zinc reduces the AsCl3 gas phase to generate elemental arsenic, and the elemental arsenic immediately reacts with zinc to generate zinc arsenide Zn3As2 in situ; the by-product zinc chloride ZnCl2 escapes in a gaseous form and is collected by a condensation system, and the zinc arsenide is suspended on the surface of the zinc melt due to the lower density than the liquid zinc, so that continuous or batch separation and collection can be realized. The application has the advantages of simple process, high reaction efficiency and high product purity, avoids problems such as uneven components and introduction of impurities in the traditional solid-phase reaction method, and is suitable for large-scale production of semiconductor-grade zinc arsenide materials.

Description

Technical Field

[0001] This invention relates to the field of inorganic compound synthesis technology, and in particular to a method and apparatus for preparing high-purity zinc arsenide by multiphase reduction-melt alloying. Background Technology

[0002] Zinc arsenide (Zn3As2), as a group II-V compound semiconductor material, has shown significant application potential in fields such as infrared detection, high-speed electronic devices, and high-efficiency thermoelectric conversion modules due to its unique band structure, high carrier mobility, and remarkable thermoelectric properties. However, its industrial application has long been constrained by bottlenecks in its fabrication technology.

[0003] Currently, the synthesis of high-purity zinc arsenide mainly relies on the direct elemental synthesis method. This method typically involves placing high-purity zinc powder and arsenic powder in a stoichiometric ratio under vacuum and high-temperature heat treatment to form Zn3As2 through a solid-state diffusion reaction. Although the principle of this method is simple, it has a series of problems: elemental arsenic, especially in its powder form, is extremely toxic (highly toxic and carcinogenic). During weighing, mixing, loading, and subsequent sealing operations, toxic dust and aerosols are easily generated, posing a serious threat to operators and requiring extremely high levels of environmental protection in the production environment, significantly increasing the cost and complexity of production facilities; the solid-state reaction depends on the interdiffusion of atoms between solid particles, and the kinetic process is slow and incomplete. Even after prolonged high-temperature treatment, unreacted arsenic or zinc inclusions and regions where the composition deviates from the stoichiometric ratio are often present in the product, leading to inhomogeneous and unstable material properties; to obtain a homogeneous product, multiple intermediate grinding and re-sintering processes are often required, making the process lengthy. Summary of the Invention

[0004] Technical problems to be solved

[0005] To address the shortcomings of existing technologies, a safe, rapid, and high-purity zinc arsenide synthesis method and supporting equipment are provided. This method enables in-situ reduction and alloying of arsenic and automatic separation of by-products, solving problems such as high toxicity risk, low reaction efficiency, uneven products, and lengthy processes in existing direct elemental methods, and meeting the needs of large-scale production of semiconductor-grade zinc arsenide.

[0006] Technical solution

[0007] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing high-purity zinc arsenide through multiphase reduction-melt alloying, comprising the following steps:

[0008] S1 places liquid arsenic trichloride (AsCl3) in a constant temperature volatilization device and heats it at 80-130℃ to volatilize it into AsCl3 vapor. High-purity inert gas is used as the carrier gas to carry and transport the AsCl3 vapor to the reaction zone at a flow rate of 50-200 mL / min.

[0009] In step S2, high-purity zinc granules are placed in a sealed reactor and heated to 650-850℃ under an inert atmosphere to melt them and form a liquid zinc pool. The AsCl3 vapor supplied in step S1 is introduced into the bottom of the liquid zinc pool through a corrosion-resistant conduit and a gas distribution device. The AsCl3 reacts with the liquid zinc to produce elemental arsenic, which immediately alloys with the molten zinc to form zinc arsenide (Zn3As2). The reduction reaction equation is as follows:

[0010] 2AsCl3 (g)+3Zn(l)=2As(g)+ 3ZnCl2 (g),

[0011] The alloying reaction equation is:

[0012] 3Zn(l) + 2As(g)→ Zn3As2(s);

[0013] The byproduct zinc chloride ZnCl2 generated by the S3 reaction volatilizes above 650℃ and escapes from the molten pool in the form of bubbles. The generated zinc arsenide Zn3As2, because its density is lower than that of liquid zinc, is suspended on the surface of the zinc melt in a solid or semi-molten state.

[0014] The gaseous ZnCl2, unreacted carrier gas, and AsCl3 that escape from S4 enter the condensation system. ZnCl2 condenses into a solid at the cold end below 200℃ and is collected. After the reaction is completed, heating and gas supply are stopped. After the system cools down, high-purity zinc arsenide products are collected from the surface of the zinc melt. The liquid zinc can be reused.

[0015] Preferably, the high-purity inert gas is high-purity argon or high-purity nitrogen with a purity of not less than 99.999%, to avoid introducing impurities and to ensure the inertness of the carrier gas, preventing side reactions with the reaction system.

[0016] Preferably, the purity of the high-purity zinc granules is not less than 99.999%, and zinc powder or zinc ingots can be used to ensure product purity.

[0017] Preferably, in step S2, the heating rate of the closed reactor is 5°C / min, and the temperature is maintained for at least 2 hours after melting to ensure that the zinc is completely melted to form a uniform molten pool, providing a stable reaction environment for subsequent reactions.

[0018] Preferably, the gas distribution device in step S2 is a quartz sand core, which is used to uniformly disperse AsCl3 vapor at the bottom of the liquid zinc molten pool and improve the uniformity of the reaction.

[0019] Preferably, in step S2, the condensation system forms a stepped temperature range from the inlet to the outlet, which facilitates the separation and collection of ZnCl2 and unreacted AsCl3; the exhaust gas is treated with an oxidizing cleaning solution in a scrubbing tower before being discharged, thus avoiding environmental pollution from toxic gases.

[0020] A high-purity zinc arsenide preparation apparatus includes a raw material storage tank, a constant temperature volatilization device, an inlet pipe, a mass flow meter, a closed reactor, a reaction gas pipeline, a condensation and collection device, a washing tower, and related valves and thermal insulation materials.

[0021] The raw material storage tank is used to store liquid arsenic trichloride (AsCl3) and is connected to a constant temperature volatilization device through a raw material isolation valve. The constant temperature volatilization device is used to heat the liquid AsCl3 to volatilize it. The air inlet pipe is connected to the constant temperature volatilization device and is used to introduce high-purity inert gas. A mass flow meter is installed on the air inlet pipe to control the carrier gas flow rate.

[0022] The sealed reactor is equipped with a gas distribution device. One end of the reaction gas pipeline is connected to a constant temperature volatilization device, and the other end passes through the sealed reactor and is connected to the gas distribution device to introduce AsCl3 vapor into the bottom of the liquid zinc molten pool. The sealed reactor is equipped with a heating device and heat insulation material to control the reaction temperature and keep it warm.

[0023] The condensation and collection device is connected to the closed reactor and is used to condense and collect gaseous ZnCl2 and unreacted AsCl3. The bottom of the condensation and collection device is equipped with a collection chamber, and a collection chamber gate valve is provided between the collection chamber and the condensation and collection device. The scrubbing tower is connected to the condensation and collection device through a tail gas pipe. The scrubbing tower is filled with an oxidation cleaning liquid for the harmless treatment of the tail gas.

[0024] Preferably, the sealed reactor, reaction gas pipeline and gas distribution device are all made of corrosion-resistant materials to avoid corrosion by AsCl3 or ZnCl2 and extend the service life of the device.

[0025] Preferably, the condensation collection device is equipped with a cooling water circulation system to maintain the cold end temperature below 200°C, stably maintain the cold end temperature, and ensure efficient condensation and collection of by-products.

[0026] Beneficial effects

[0027] This invention provides a method for determining the germanium content in zinc arsenide. It has the following beneficial effects:

[0028] 1. High safety: It avoids the direct use of highly toxic arsenic powder, and fixes the arsenic element in AsCl3 liquid, making operation and transportation safer and more controllable, and greatly reducing the health risks to operators and the protection costs of the production environment;

[0029] 2. High efficiency and uniform products: The reaction takes place in a liquid medium, and the mass and heat transfer efficiency is much higher than that of solid-state reaction. The reduction and alloying reactions are completed instantly, which effectively avoids the problem of slow atomic diffusion in solid-state reaction. The products have uniform composition and stable performance.

[0030] 3. Self-separation and purification: By utilizing the volatility of ZnCl2 and the density difference between Zn3As2 and Zn, the automatic and efficient physical separation of the byproduct ZnCl2 and the main product Zn3As2 is achieved without additional separation and purification steps, simplifying the post-processing process and reducing production costs.

[0031] 4. High product purity: The gas phase reaction reduces the contact contamination between the product and the container wall, and the volatilized ZnCl2 can carry away some impurities in the reaction system, playing a self-purification role. The purity of the obtained product meets the semiconductor grade requirements.

[0032] 5. Continuous production potential: By controlling the feed rate of AsCl3 and the temperature of the zinc molten pool, it is theoretically possible to achieve continuous production and skimming of zinc arsenide. Liquid zinc can be reused, making it suitable for large-scale industrial production. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the zinc arsenide synthesis process of the present invention;

[0034] Figure 2 This invention relates to a device for preparing high-purity zinc arsenide through multiphase reduction-melt alloying.

[0035] Figure 3 The XRD results are for zinc arsenide (Zn3As2) obtained in this invention.

[0036] Explanation of the labels in the diagram: 1-Raw material storage tank, 2-Inlet pipe, 3-Gas valve, 4-Gas valve, 5-Constant temperature evaporation device, 6-Liquid AsCl3, 7-Raw material storage tank, 8-Raw material isolation valve, 9-Reaction gas pipeline, 10-Heat insulation material, 11-Gas valve, 12-Closed reactor, 13-Liquid zinc, 14-Gas valve, 15-Condensation and collection device, 16-Tail gas pipe, 17-Collection bin gate valve, 18-Collection bin, 19-Scrubbing tower, 20-Oxidation cleaning solution. Detailed Implementation

[0037] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] Example 1:

[0039] like Figures 1 to 3 As shown, the experimental procedure is as follows: Figure 1 As shown, using Figure 2 The experimental setup shown is followed by the specific steps:

[0040] 1. Atmosphere replacement: Add 500g of high-purity zinc powder (99.999%) to the closed reactor, open gas valves 3, 4, 11, and 14, and purge high-purity argon gas (99.999%) to a slightly positive pressure of 105kPa. Repeat this process three times to completely remove oxygen and moisture from the equipment. After the replacement is completed, close the above gas valves.

[0041] 2. Heating and melting: Start the heating program of the constant temperature volatilization device and the sealed reactor. The heating rate is 5℃ / min. Keep the temperature of the constant temperature volatilization device constant at 100℃ and the temperature of the sealed reactor at 650℃. Keep it at this temperature for 2 hours to ensure that the zinc powder is completely melted into a liquid zinc pool.

[0042] 3. Reaction Procedure: Open the raw material isolation valve and slowly introduce liquid AsCl3 from the raw material storage tank into the constant temperature volatilization device. Simultaneously, open gas valves 3, 4, 11, and 14 to introduce argon carrier gas into the constant temperature volatilization device through the inlet pipe. The carrier gas flow rate is controlled at 100 mL / min by a mass flow meter. The liquid AsCl3 is carried by argon gas bubbling to form vapor, which enters the closed reactor through the reaction gas pipeline. The temperature of the carrier gas is maintained by heat insulation material to prevent AsCl3 vapor from condensing. After the gaseous AsCl3 is introduced into the liquid zinc molten pool, a rapid reduction-alloying reaction occurs. Continuous tiny bubbles (ZnCl2 vapor) can be observed escaping from the surface of the molten pool.

[0043] 4. Byproduct and tail gas treatment: Gas carrying ZnCl2 volatiles enters the condensation and collection device. Under the action of cooling water, a stepped temperature range is formed in the condensation and collection device from the inlet to the tail end. ZnCl2 condenses into a solid at the cold end, and unreacted AsCl3 condenses into a liquid. Both are controlled by the gate valve of the collection chamber and taken out from the collection chamber. The tail gas after removing the volatile precipitate enters the scrubbing tower through the tail gas pipe and is treated with oxidizing cleaning liquid to be harmless.

[0044] 5. Product Collection: After approximately 4 hours of aeration reaction, a layer of grayish-black solid product (Zn3As2) gradually accumulates on the surface of the molten pool. Heating and carrier gas supply are stopped. The heating device is shut off, and the reactor is allowed to cool naturally to room temperature under an argon atmosphere. The reactor is opened, and the flaky zinc arsenide product suspended on the surface of the zinc ingot is removed and weighed, yielding approximately 85g of product. X-ray diffraction (XRD) analysis is performed (e.g., ...). Figure 3 As shown in the figure, the main phase of the product is Zn3As2, which has high purity and meets the requirements of semiconductor grade.

[0045] Example 2

[0046] The difference between this embodiment and Embodiment 1 lies in the adjustment of the reaction conditions, as detailed below:

[0047] The reaction apparatus and atmosphere replacement steps are the same as in Example 1. 450g of high-purity zinc ingot (99.999%) is added to the reactor. The temperature of the sealed reactor is set and stabilized at 700℃. The water bath temperature of the constant temperature volatilization device (AsCl3 evaporation flask) is 85℃. High-purity argon gas is introduced as the carrier gas, and the flow rate is controlled at 180 mL / min.

[0048] The higher carrier gas flow rate and reaction temperature significantly increased the reaction throughput per unit time. After the reaction lasted for 3 hours, the reaction in the molten pool was intense, with a large number of ZnCl2 bubbles escaping. The zinc arsenide formed on the surface of the molten pool was a porous, loose, blocky substance. After the reaction was completed, about 205g of product was collected, which is a high yield, but the product morphology was not as dense as in Example 1.

[0049] Example 3

[0050] This embodiment aims to verify the feasibility of low-cost carrier gas and the reusability of zinc melt, as detailed below:

[0051] The reaction apparatus and atmosphere replacement steps were the same as in Example 1, but high-purity nitrogen (99.999%) was used for both the protective gas and the carrier gas. The zinc source was the remaining zinc ingot (about 395g) collected after the reaction of zinc arsenide in Example 1. It did not need to be purified and was directly used as the zinc source for this round of reaction. Except that the temperature of the closed reactor was set to 700°C, the other reaction conditions were the same as in Example 1.

[0052] Experimental results show that the zinc melt can undergo a normal reduction-alloying reaction, and new zinc arsenide products are successfully generated on the surface of the melt. About 80g of products were collected, and the yield was comparable to that of the first use of new zinc granules. This proves that high-purity nitrogen can be used as a carrier gas to replace argon, and the zinc melt can be reused, effectively reducing production costs.

[0053] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing high-purity zinc arsenide through multiphase reduction-melt alloying, characterized in that, Includes the following steps: S1. Liquid arsenic trichloride (AsCl3) is placed in a constant temperature volatilization device and heated at 80-130℃ to volatilize and generate AsCl3 vapor. High-purity inert gas is used as the carrier gas, and the AsCl3 vapor is carried and transported to the reaction zone at a flow rate of 50-200 mL / min. S2. High-purity zinc granules are placed in a closed reactor and heated to 650-850℃ under an inert atmosphere to melt them and form a liquid zinc pool. The AsCl3 vapor supplied in step S1 is introduced into the bottom of the liquid zinc pool through a corrosion-resistant conduit and a gas distribution device. AsCl3 reacts with the liquid zinc to produce elemental arsenic. The elemental arsenic immediately reacts with the zinc melt to form zinc arsenide Zn3As2. The reduction reaction equation is: 2AsCl3 (g) + 3Zn(l) = 2As(g) + 3ZnCl2 (g). The alloying reaction equation is: 3Zn(l) + 2As(g) → Zn3As2 (s). S3. The byproduct of the reaction, zinc chloride (ZnCl2), volatilizes above 650°C and escapes from the molten pool in the form of bubbles. The generated zinc arsenide (Zn3As2) is less dense than liquid zinc and is suspended on the surface of the zinc melt in a solid or semi-molten state. S4. The escaped gaseous ZnCl2, unreacted carrier gas, and AsCl3 enter the condensation system. ZnCl2 condenses into a solid at the cold end below 200℃ and is collected. After the reaction is completed, heating and gas supply are stopped. After the system cools down, high-purity zinc arsenide products are collected from the surface of the zinc melt. Liquid zinc can be reused.

2. The preparation method according to claim 1, characterized in that, The high-purity inert gas is high-purity argon or high-purity nitrogen, with a purity of not less than 99.999%.

3. The preparation method according to claim 1, characterized in that, The purity of the high-purity zinc granules is not less than 99.999%, and the high-purity zinc granules are zinc powder or zinc ingots.

4. The preparation method according to claim 1, characterized in that, In step S2, the heating rate of the closed reactor is 5°C / min, and the temperature is maintained for at least 2 hours after melting.

5. The preparation method according to claim 1, characterized in that, The air distribution device in step S2 is a quartz sand core.

6. The preparation method according to claim 1, characterized in that, In step S2, the condensation system forms a stepped temperature range from the inlet to the outlet, which facilitates the separation and collection of ZnCl2 and unreacted AsCl3; the tail gas is discharged after being treated with an oxidizing cleaning solution in a scrubbing tower to render it harmless.

7. An apparatus for preparing high-purity zinc arsenide using the preparation method according to any one of claims 1-6, characterized in that, This includes raw material storage tanks, constant temperature evaporation devices, gas inlet pipes, mass flow meters, closed reactors, reaction gas pipelines, condensation and collection devices, scrubbing towers, and related valves and thermal insulation materials; The raw material storage tank is used to store liquid arsenic trichloride (AsCl3) and is connected to a constant temperature volatilization device through a raw material isolation valve. The constant temperature volatilization device is used to heat the liquid AsCl3 to volatilize it. The air inlet pipe is connected to the constant temperature volatilization device and is used to introduce high-purity inert gas. A mass flow meter is installed on the air inlet pipe to control the carrier gas flow rate. The sealed reactor is equipped with a gas distribution device. One end of the reaction gas pipeline is connected to a constant temperature volatilization device, and the other end passes through the sealed reactor and is connected to the gas distribution device to introduce AsCl3 vapor into the bottom of the liquid zinc molten pool. The sealed reactor is equipped with a heating device and heat insulation material on the outside. The condensation and collection device is connected to the closed reactor and is used to condense and collect gaseous ZnCl2 and unreacted AsCl3. The bottom of the condensation and collection device is equipped with a collection chamber, and a collection chamber gate valve is provided between the collection chamber and the condensation and collection device. The washing tower is connected to the condensation and collection device through a tail gas pipe, and the washing tower is filled with an oxidation cleaning solution.

8. The preparation apparatus according to claim 7, characterized in that, The sealed reactor, reaction gas pipeline, and gas distribution device are all made of corrosion-resistant materials.

9. The preparation apparatus according to claim 7, characterized in that, The condensation collection device is equipped with a cooling water circulation system to maintain the cold end temperature below 200°C.

Images