A method of synthesizing rhenium hexafluoride crystals in a diamond anvil cell

Abstract

The present application provides a method for synthesizing rhenium hexafluoride crystals in a diamond anvil cell, selecting metal rhenium as the initial raw material of the reaction, encapsulating xenon difluoride and liquid argon into the sample cavity of the diamond anvil cell; heating the diamond anvil cell at 60 DEG C until the xenon difluoride crystals disappear, and observing the characteristic vibration peaks of rhenium hexafluoride and rhenium heptafluoride by Raman spectroscopy. Continue heating at 60 DEG C to completely convert rhenium heptafluoride into rhenium hexafluoride, and the whole process is monitored by Raman spectroscopy. After complete conversion, cool to room temperature and regulate the pressure to between 0.3 Gpa and 1.2 Gpa, to obtain rhenium hexafluoride crystals with good crystallization effect. The present application is simple to operate, safe and pollution-free, and has high repeatability. By regulating the reduction reaction conditions, the existence of impurities rhenium heptafluoride is avoided, and high-purity rhenium hexafluoride is obtained.

Description

Technical Field

[0001] This invention belongs to the technical field of transition metal fluoride synthesis in diamond anvil cells, and particularly relates to a method for synthesizing rhenium hexafluoride crystals in diamond anvil cells. Background Technology

[0002] The synthesis of transition metal fluorides is generally carried out at ambient temperature and pressure. However, in the field of high-pressure science, the synthesis of fluorides in diamond anvil cells faces technical challenges due to the difficulties in encapsulating the fluorine source (F2). Therefore, research on fluorides in this field largely remains at the level of theoretical calculations and experimental studies on several stable, low-oxidizing fluorides. Under normal conditions, XeF2 can be used as an oxidant to replace F2, reacting anhydrous hydrogen fluoride solution of XeF2 with transition metals. However, under high-pressure conditions, most solvents, such as acetonitrile and anhydrous HF, will solidify. Therefore, a method is needed to replace solvents to fully utilize the oxidizing properties of XeF2 under high-pressure conditions.

[0003] Tungsten and rhenium alloys are widely used in aerospace, nuclear energy, metallurgy, electronics, and petrochemical industries. High-quality tungsten-rhenium coatings can also be prepared using tungsten hexafluoride, rhenium hexafluoride, and hydrogen as source gases via chemical vapor deposition (CVD), showing broad application prospects. With the continuous expansion of rhenium metal applications, rhenium hexafluoride is increasingly used, becoming an important source gas.

[0004] In the synthesis of rhenium hexafluoride, a large amount of byproducts such as rhenium trifluoride, rhenium tetrafluoride, rhenium pentafluoride, and rhenium heptafluoride are often generated, leading to increased processing costs and affecting further purification of rhenium hexafluoride, as impurities are difficult to remove completely. Therefore, this invention aims to explore a method for synthesizing high-purity rhenium hexafluoride under high-pressure conditions. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a method for synthesizing rhenium hexafluoride crystals in a diamond anvil cell, comprising the following steps:

[0006] (1) Use a metal rhenium 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.

[0007] (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.

[0008] (3) Place the diamond anvil cell into the vacuum cryogenic liquefaction device. When the liquid argon is immersed in the diamond anvil cell, separate the upper and lower presses and press them together after the liquid argon enters the sample chamber to seal the liquid argon into the sample chamber and complete the loading. Liquid argon is used as the pressure transmission medium.

[0009] (4) The 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, which reacts with metallic rhenium to form rhenium fluoride; the presence of rhenium hexafluoride and rhenium heptafluoride can be observed by Raman spectroscopy.

[0010] (5) Continue heating to completely convert rhenium heptafluoride into rhenium hexafluoride. The entire process is monitored by Raman spectroscopy. The conversion of rhenium heptafluoride is determined by observing its Raman characteristic peaks. After complete conversion, cool to room temperature. When the pressure is below 0.3 GPa, pressurize to 0.3 GPa to obtain rhenium hexafluoride crystals. When the pressure is above 0.3 GPa but below 1.2 GPa, cool to room temperature to obtain rhenium hexafluoride 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, the packaging pressure in step (3) does not exceed 1.2 GPa.

[0013] Preferably, in step (4), the diamond anvil cell is heated to 60°C until xenon difluoride in the sample chamber disappears and rhenium fluoride is generated; in step (5), the heating continues at 60°C to completely convert rhenium heptafluoride into rhenium hexafluoride.

[0014] The beneficial effects of this invention are:

[0015] This invention provides a method for synthesizing rhenium hexafluoride crystals in a diamond anvil cell. The method is simple, safe, pollution-free, and highly reproducible. By rationally using xenon difluoride as the fluorinating agent, this method overcomes the difficulties of encapsulating fluorine gas and other fluoride gases in a diamond anvil cell, thus synthesizing rhenium hexafluoride and rhenium heptafluoride in the diamond anvil cell. Then, by controlling the reduction reaction conditions, rhenium heptafluoride is reduced to rhenium hexafluoride, yielding high-purity rhenium hexafluoride and avoiding the presence of impurity rhenium heptafluoride. Attached Figure Description

[0016] Figure 1 Photographs of ReF6 prepared for embodiments of the present invention.

[0017] Figure 2 The Raman spectrum of ReF6 prepared in an embodiment of the present invention. Detailed Implementation

[0018] This embodiment provides a method for synthesizing rhenium hexafluoride crystals in a diamond anvil cell, including the following steps:

[0019] (1) Select a four-post diamond anvil cell with a diamond anvil face size of 500 μm; use a rhenium 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 250 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.

[0020] (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.

[0021] (3) Place the diamond anvil cell into the vacuum cryogenic liquefaction device. When the liquid argon is immersed in the diamond anvil cell, separate the upper and lower presses and pressurize the liquid argon into the sample chamber after the liquid argon enters the sample chamber to complete the loading. The sealing pressure shall not exceed 1.2 GPa.

[0022] (4) The diamond anvil cell loaded with xenon difluoride and liquid argon is heated to 60°C until the xenon difluoride in the sample chamber disappears and the xenon difluoride is converted into gaseous state and reacts with metallic rhenium to generate rhenium fluoride; the presence of rhenium hexafluoride and rhenium heptafluoride can be observed by Raman spectroscopy.

[0023] (5) Continue heating at 60℃ to completely convert rhenium heptafluoride into rhenium hexafluoride. The entire process is monitored by Raman spectroscopy, and the complete conversion of rhenium heptafluoride is determined by observing its Raman characteristic peaks. After complete conversion, cool to room temperature. If the pressure is below 0.3 GPa, pressurize to 0.3 GPa to obtain rhenium hexafluoride crystals; if the pressure is above 0.3 GPa, cool to room temperature to obtain rhenium hexafluoride crystals. Rhenium hexafluoride crystals with good crystallization effect can be obtained.

[0024] like Figure 1 As shown, rhenium hexafluoride crystals were obtained. Figure 2 The image shows the Raman spectrum of the product rhenium hexafluoride, with no Raman peaks observed for other rhenium fluorides.

Claims

1. A method for synthesizing rhenium hexafluoride crystals in a diamond anvil cell, characterized in that: Includes the following steps: (1) Use a metal rhenium 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) 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 the xenon difluoride crystal from volatilizing. (3) Place the diamond anvil cell into the vacuum cryogenic liquefaction device. When the liquid argon is immersed in the diamond anvil cell, separate the upper and lower presses and press them together after the liquid argon enters the sample chamber to seal the liquid argon into the sample chamber and complete the loading. Liquid argon is used as the pressure transmission medium. (4) The 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 rhenium fluoride is generated; the characteristic vibrational spectra of rhenium hexafluoride and rhenium heptafluoride are observed by Raman spectroscopy. (5) Continue heating to completely convert rhenium heptafluoride into rhenium hexafluoride. After complete conversion, adjust the pressure and cool to room temperature to obtain rhenium hexafluoride crystals.

2. The method for synthesizing rhenium hexafluoride crystals in a diamond anvil cell according to claim 1, 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.

3. The method for synthesizing rhenium hexafluoride crystals in a diamond anvil cell according to claim 1, characterized in that: Step (3) The encapsulation pressure shall not exceed 1.2 GPa.

4. The method for synthesizing rhenium hexafluoride crystals in a diamond anvil cell according to claim 1, characterized in that: Step (5) When the pressure is below 0.3 GPa, pressurize to 0.3 GPa to obtain rhenium hexafluoride crystals; when the pressure is above 0.3 GPa but below 1.2 GPa, rhenium hexafluoride crystals gradually precipitate during the cooling process to room temperature.

5. The method for synthesizing rhenium hexafluoride crystals in a diamond anvil cell according to claim 1, characterized in that: Step (4) Heat the diamond anvil cell to 60°C until xenon difluoride disappears from the sample chamber and rhenium fluoride is generated; Step (5) Continue heating at 60°C to completely convert rhenium heptafluoride into rhenium hexafluoride.

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