Use of diamond anvil cell and method of synthesizing transition metal fluorides using a diamond anvil cell

Abstract

The application provides an application of a diamond anvil cell and a method for synthesizing transition metal fluoride by using the diamond anvil cell. The diamond anvil cell is applied to the synthesis of transition metal fluoride. Transition metal material is selected as initial raw material of the reaction, and xenon difluoride and liquid argon or liquid nitrogen are sealed into a sample cavity of the diamond anvil cell. The diamond anvil cell is heated at 60 DEG C until the xenon difluoride crystal disappears. Through the regulation of temperature and pressure, transition metal fluoride crystals are obtained. The fluorine gas sealing technology problem of the diamond anvil cell is solved. The solid xenon difluoride is used to replace the gaseous fluorination agent to synthesize the transition metal fluoride. A new idea for synthesizing fluoride by using the diamond anvil cell is provided. The application has the advantages of simple operation, high synthesis conversion rate, high purity, safety, no pollution and high repeatability.

Description

Technical Field

[0001] This invention relates to the application of diamond anvil cells, particularly to the application of diamond anvil cells in the synthesis of transition metal fluorides, and to a method for synthesizing tungsten hexafluoride crystals in diamond anvil cells. Background Technology

[0002] In practical applications, transition metal fluorides can serve as oxidants, fluorinating agents, and catalysts in batteries. Extensive research has been conducted on the synthesis and physicochemical properties of transition metal fluorides under ambient temperature and pressure, exploring the relationship between the highest oxidation state and the periodicity of elements through their synthesis. Diamond anvils are important experimental tools in high-pressure technology; however, due to technical difficulties in encapsulating the fluorine source (F2) in diamond anvils, the synthesis and research of fluorides in diamond anvils remain in the exploratory stage. Under high pressure, the chemical properties of elements undergo significant changes, making the exploration of new periodicities under high pressure even more meaningful. However, in this field, research on fluorides has largely remained at the level of theoretical calculations and experimental studies on several stable, low-oxidizing fluorides. This invention aims to explore the application of diamond anvils in fluoride synthesis.

[0003] At room temperature, XeF2 is a colorless, transparent, and volatile crystal. XeF2 only exhibits oxidizing properties in solution or in the gaseous state. The fluorination limit of XeF2 is determined by the reaction of anhydrous hydrogen fluoride solution with transition metals under normal conditions. Under high pressure, most solvents will solidify, such as acetonitrile and anhydrous hydrogen fluoride, common solvents for dissolving XeF2. Therefore, a method is needed to find a way to utilize the oxidizing properties of XeF2, replacing solvents, for its application in the synthesis of fluorides using diamond anvil cells.

[0004] Tungsten hexafluoride (WF6) is a commonly used specialty electronic gas with a crucial role in the semiconductor industry. It can be used to prepare tungsten films via chemical vapor deposition (CVD) or to produce tungsten disilicide (WSi2) for wiring materials in large-scale integrated circuits. The purity and cleanliness of tungsten hexafluoride directly affect the quality, integration density, specific technical specifications, and yield of optoelectronic and microelectronic components, fundamentally limiting the accuracy and precision of circuits and devices. In actual production, the purity of the fluorinating agent and the impurity content in the product, especially the hydrogen fluoride (HF) content, directly impact the difficulty of tungsten hexafluoride purification. Furthermore, the use of halogens during production causes severe environmental pollution. Therefore, a new synthesis method for tungsten hexafluoride is needed to overcome these problems. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides an application of a diamond anvil cell for the synthesis of transition metal fluorides.

[0006] Furthermore, the present invention provides a method for synthesizing transition metal fluorides using a diamond anvil cell, comprising the following steps:

[0007] (1) Use the transition metal powder to be synthesized as the initial material. Select a nickel sheet as the gasket and pre-press it to 0.1-0.15 mm. Drill holes in the pre-pressed area to form a sample cavity. The diameter of the holes is smaller than the diameter of the diamond anvil. Place the perforated gasket between the upper and lower anvils of the diamond anvil. The sample cavity is partially filled with transition metal powder. Space should be reserved in the sample cavity for xenon difluoride and pressure transmission medium.

[0008] (2) Under an argon atmosphere, load xenon difluoride crystals into the sample chamber; since xenon difluoride crystals are highly volatile, press the diamond anvil cell with the upper and lower presses together immediately after loading.

[0009] (3) Depending on the melting point of the synthesized material, liquid nitrogen or liquid argon can be selected as the pressure transmission medium; the diamond anvil is placed in the vacuum cryogenic liquefaction device. When the pressure transmission medium is immersed in the diamond anvil, the upper and lower presses are separated and the medium is pressed into the sample chamber to complete the encapsulation of the pressure transmission medium.

[0010] (4) Heat the diamond anvil cell loaded with xenon difluoride and liquid pressure transmission medium to 50-120°C until xenon difluoride disappears from the sample chamber and turns into gaseous state, reacting with transition metal materials to generate transition metal fluorides; adjust the temperature and apply appropriate pressure but not exceeding the freezing point of the pressure transmission medium to obtain transition metal fluoride crystals.

[0011] Preferably, the loading process in step (2) is carried out in a glove box with a water oxygen content of less than 0.01 ppm protected by argon.

[0012] Preferably, step (3) has a sealing pressure of no more than 1.2 Gpa for liquid argon and no more than 2.8 Gpa for liquid nitrogen.

[0013] Furthermore, the present invention provides a method for synthesizing tungsten hexafluoride using a diamond anvil cell, comprising the following steps:

[0014] (1) Since tungsten sheets are commonly used as spacers for diamond anvil cells, metal tungsten sheets are used as spacers and also as initial materials, pre-pressed to 0.1-0.15 mm, and holes are drilled in the pre-pressed area to form a sample cavity with a diameter smaller than that of the diamond anvil face; the perforated spacer is placed between the upper and lower anvil faces of the diamond anvil cell.

[0015] (2) Load the xenon difluoride crystal into the sample chamber. The loading process is carried out in a glove box with a water oxygen content of less than 0.01 ppm protected by argon. After loading, press the diamond anvil cell with the upper and lower presses in time to prevent xenon difluoride from volatilizing.

[0016] (3) Liquid nitrogen is sealed into the sample chamber by a vacuum cryogenic liquefaction device. The diamond anvil cell is placed in the liquefaction device. When the liquid nitrogen is immersed in the diamond anvil cell, the upper and lower presses are separated. After the liquid nitrogen enters the sample chamber, the pressure is applied to complete the loading. The sealing pressure does not exceed 2.8 GPa.

[0017] (4) A diamond anvil cell loaded with xenon difluoride and liquid argon is heated to 50-120°C until the xenon difluoride in the sample chamber disappears and turns into a gaseous state, reacting with metallic tungsten to form tungsten hexafluoride. After the device cools to room temperature, the presence of liquid tungsten hexafluoride can be observed by Raman spectroscopy. When the pressure is increased to 1.93 GPa, solid-phase tungsten hexafluoride is observed to precipitate. Recrystallization at 90°C yields bulk tungsten hexafluoride crystals. Tungsten hexafluoride solidifies and crystallizes, while other components remain liquid, achieving separation of the product from impurities.

[0018] The beneficial effects of this invention are:

[0019] This invention solves the technical challenge of fluorine encapsulation in high-pressure devices (diamond anvil cells) by using solid xenon difluoride to replace gaseous fluorinating agents to synthesize transition metal fluorides; it provides a new approach to fluoride synthesis for diamond anvil cells. This invention is simple to operate, has a high synthesis conversion rate, high purity, is safe and pollution-free, and has high reproducibility.

[0020] This invention selects xenon difluoride as the fluorinating agent. Xenon gas in the reaction product is chemically inert and does not react with other substances. As a monatomic gas, xenon has no Raman characteristic peaks, therefore it will not interfere with the Raman signal of the fluoride and will not affect the accuracy of product observation. By utilizing the difference in freezing points and controlling the pressure, tungsten hexafluoride is separated from xenon gas and liquid nitrogen, achieving the purification of tungsten hexafluoride and separating high-purity tungsten hexafluoride crystals. Attached Figure Description

[0021] Figure 1 This is a photograph of the WF6 sample chamber in an embodiment of the present invention.

[0022] Figure 2 The Raman spectrum of WF6 obtained in an embodiment of the present invention is shown. Detailed Implementation

[0023] This embodiment provides a method for synthesizing tungsten hexafluoride using a diamond anvil cell, including the following steps:

[0024] (1) Select a four-post diamond anvil cell with a diamond anvil face size of 1000 μm; use a tungsten sheet as a gasket and pre-press it to 0.15 mm; use a laser drilling device to drill holes in the pre-pressed area to form a sample cavity with a diameter of 500 μm; place the drilled gasket between the upper and lower anvil faces of the diamond anvil cell; use the ruby ​​pressure calibration method for pressure calibration.

[0025] (2) Load the xenon difluoride crystal into the sample chamber. The loading process is carried out in a glove box protected by argon with a water oxygen content of less than 0.01 ppm. The crystal size occupies about one-third of the entire sample chamber. After loading, press the diamond anvil cell with the upper and lower presses in time to prevent xenon difluoride from volatilizing.

[0026] (3) Place the diamond anvil cell into the vacuum cryogenic liquefaction device. When the liquid nitrogen is immersed in the diamond anvil cell, separate the upper and lower presses. After the liquid nitrogen enters the sample chamber, pressurize and seal the liquid nitrogen into the sample chamber to complete the loading. The sealing pressure shall not exceed 2.8 Gpa. The upper and lower presses are separated in the liquefaction device by springs. The springs are sleeved on the four columns of the four-column press.

[0027] (4) A diamond anvil cell loaded with xenon difluoride and liquid nitrogen was heated to 60°C until the xenon difluoride in the sample chamber disappeared, turning into a gaseous state and reacting with metallic tungsten to form tungsten hexafluoride. After the device cooled to room temperature, the presence of liquid tungsten hexafluoride could be observed by Raman spectroscopy. The pressure was increased to approximately 1.93 GPa, and recrystallization was performed at 90°C to obtain bulk tungsten hexafluoride crystals. The tungsten hexafluoride solidified and crystallized, while the other components remained liquid, achieving separation of the product from impurities. Figure 1 As shown, tungsten hexafluoride crystals were obtained. Figure 2 The image shows the Raman spectrum of the product, tungsten hexafluoride.

[0028] In this embodiment, the argon gas purity was 99.9%. Liquefaction was carried out in a vacuum, and no characteristic peaks of water and gases commonly found in air were observed in the Raman spectrum.

[0029] In this example, the tungsten sheet has a purity of 99.9%.

Claims

1. An application of a diamond anvil cell, characterized in that: It is used in the synthesis of transition metal fluorides.

2. A method for synthesizing transition metal fluorides using a diamond anvil cell, characterized in that: Includes the following steps: (1) The transition metal powder to be synthesized is used as the initial material, and the nickel sheet is used as the gasket. The nickel sheet is pre-pressed to 0.1-0.15 mm. Holes are drilled in the pre-pressed area to form the sample cavity. The diameter of the holes is smaller than the diameter of the diamond anvil. The perforated gasket is placed between the upper and lower anvils of the diamond anvil. The sample cavity is partially filled with transition metal powder. (2) Under an argon atmosphere, load the xenon difluoride crystal into the sample chamber; after loading, press the diamond anvil cell with the upper and lower presses in time to prevent xenon difluoride from volatilizing. (3) Place the diamond anvil cell into the vacuum cryogenic liquefaction device. When the pressure-transmitting medium liquid argon or liquid nitrogen is immersed in the diamond anvil cell, separate the upper and lower presses and press them together after the medium enters the sample chamber to complete the encapsulation of the liquid pressure-transmitting medium. (4) Heat the diamond anvil loaded with xenon difluoride and liquid argon to 50-120°C until xenon difluoride disappears from the sample chamber and turns into gaseous state, reacting with transition metal materials to form transition metal fluorides; adjust the temperature and apply appropriate pressure but not exceeding the freezing point of the pressure transmission medium to obtain transition metal fluoride crystals.

3. The method for synthesizing transition metal fluorides using a diamond anvil cell according to claim 2, characterized in that: Step (2) The loading process is carried out in a glove box protected by argon gas with a water oxygen content of less than 0.01 ppm.

4. The method for synthesizing transition metal fluorides using a diamond anvil cell according to claim 2, characterized in that: Step (3) The sealing pressure is lower than the freezing point of the pressure transmission medium. The pressure transmission medium is liquid nitrogen with a pressure lower than 2.8 GPa; the pressure transmission medium is liquid argon with a pressure lower than 1.2 GPa.

5. A method for synthesizing tungsten hexafluoride using a diamond anvil cell, characterized in that: Includes the following steps: (1) Use a tungsten sheet as a gasket and pre-press it to 0.1-0.15 mm. Drill holes in the pre-pressed area to form a sample cavity. The diameter of the holes is smaller than the diameter of the diamond anvil. Place the perforated gasket between the upper and lower anvils of the diamond anvil. (2) Load the xenon difluoride crystal into the sample chamber; after loading, press the diamond anvil cell with the upper and lower presses in time to prevent xenon difluoride from volatilizing; (3) Place the diamond anvil cell into the vacuum cryogenic liquefaction device. When the liquid nitrogen is immersed in the diamond anvil cell, separate the upper and lower presses and press them together after the liquid nitrogen enters the sample chamber to seal the liquid nitrogen into the sample chamber as a pressure transmission medium. (4) Heat the diamond anvil cell loaded with xenon difluoride and liquid nitrogen to 50-120°C until xenon difluoride disappears from the sample chamber and turns into gas, reacting with tungsten metal to form tungsten hexafluoride. After the device cools to room temperature, the presence of liquid tungsten hexafluoride can be observed by Raman spectroscopy. Apply appropriate pressure but not exceeding the solidification pressure point of liquid nitrogen, 2.8 GPa, and the tungsten hexafluoride solidifies and crystallizes, and the tungsten hexafluoride crystals are separated.

6. The method for synthesizing tungsten hexafluoride using a diamond anvil cell according to claim 5, characterized in that: Step (2) The loading process is carried out in a glove box protected by argon gas with a water oxygen content of less than 0.01 ppm.

7. The method for synthesizing transition metal fluorides using a diamond anvil cell according to claim 5, characterized in that: Step (3) The encapsulation pressure shall not exceed 2.8 GPa.

8. The method for synthesizing transition metal fluorides using a diamond anvil cell according to claim 5, characterized in that: Step (4) involves applying a pressure of 1.93 GPa and then heating at 90 °C to recrystallize large tungsten hexafluoride crystals.

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