CN113387901B - Limited high-density anhydrous alkali metal polymeric nitrogen Cm-NaN 5 High pressure process of (2) - Google Patents

Abstract

The invention relates to the technical field of preparation of high energy density materials, and provides a high-pressure preparation method of confined high-density anhydrous alkali metal polymerized nitrogen Cm-NaN ₅ . The invention uses sodium azide confined in boron nitride nanotubes as a starting material, and undergoes high-pressure treatment to obtain confined high-density anhydrous alkali metal polynitrogen Cm-NaN ₅ that exists stably under high pressure. The method provided by the invention has simple steps and is easy to operate. For the first time, the high-pressure preparation of confined high-density anhydrous alkali metal polymeric nitrogen Cm-NaN ₅ is realized, and an effective technical approach is provided for the experimental preparation of new anhydrous alkali metal polymeric nitrogen.

Description

A high-pressure preparation method of confined high-density anhydrous alkali metal polymeric nitrogen Cm-NaN5

This application is a divisional application with an application date of January 17, 2020, an application number of 202010053376.4, and an invention title of "A high-temperature, high-pressure preparation and atmospheric pressure interception method for confined high-density anhydrous alkali metal polymeric nitrogen NaN ₅ " , the applicant is Jilin University.

technical field

The invention relates to the technical field of preparation of high energy density materials, in particular to a high-pressure preparation method of confined high-density anhydrous alkali metal polymerized nitrogen Cm-NaN ₅ .

Background technique

Polynitrogen is a typical high energy density material (HEDM), in which the nitrogen atoms are connected by NN bonds or N=N bonds, due to the NN bond energy (160KJ/mol)/N=N bond energy (418KJ/mol) It is far lower than the N≡N bond energy (954KJ/mol) in nitrogen, and it will release huge energy when it depolymerizes and returns to _N2 molecules. Pentazole compounds are a typical class of polymeric nitrogen materials. The nitrogen atoms in the nitrogen pentacyclic ring (N ₅ ^- ) are on the same plane, and the nitrogen-nitrogen bond length is between the nitrogen-nitrogen single bond (NN) and the double bond (N =N).

In recent years, people have obtained many pentazolium salts that can exist stably under environmental conditions by using chemical synthesis methods, including sodium-based pentazolium salts [Na ₈ (N ₅ ) ₈ (H ₂ O) ₃ ] _n and [Na(N ₅ )(H ₂ O)]·2H ₂ O. In the two sodium-based pentazole skeleton structures, sodium ions, bound water and free water play an important role in stabilizing the nitrogen pentacyclic ring (N ₅ ^- ). It is worth noting that both of these two sodium-based pentazole skeleton structures contain a large amount of water molecules, and the sodium-based pentazole structure cannot be separated from water molecules to exist stably under environmental conditions, and the two sodium-based pentazole skeleton structures The cage-like structure also leads to a great reduction in the density of the sodium-based pentazole structure.

So far, the sodium-based pentazole structure containing only metal sodium ion coordination has not been reported, and the higher-density anhydrous alkali metal polynitrogen structure NaN ₅ has not yet been reported.

Contents of the invention

In view of this, the present invention provides a high-temperature, high-pressure preparation and normal-pressure interception method of confined high-density anhydrous alkali metal polynitrogen NaN ₅ . The present invention obtains stable confined high-density anhydrous alkali metal polymer nitrogen Cm-NaN ₅ and Pmn2 ₁ -NaN ₅ under high pressure for the first time, and realizes stable confined high-density anhydrous alkali metal polymerization under normal pressure Nitrogen P2/c-NaN ₅ .

In order to achieve the above-mentioned purpose of the invention, the present invention provides the following technical solutions:

A high-pressure preparation method of confined high-density anhydrous alkali metal polynitrogen Cm-NaN ₅ , comprising the following steps:

Sodium azide confined in boron nitride nanotubes is encapsulated in a diamond-anvil high-pressure cavity, and then pressurized to above 35GPa to obtain a confined high-density anhydrous alkali metal polynitrogen Cm-NaN that exists stably under high pressure ₅ .

A high-temperature and high-pressure preparation method of confined high-density anhydrous alkali metal polynitrogen Pmn2 ₁ -NaN ₅ , comprising the following steps:

Sodium azide confined in boron nitride nanotubes is encapsulated in a diamond-anvil high-pressure cavity, pressurized to above 50GPa, and then subjected to 2000-2300K laser heating treatment to obtain confinement high-density nanotubes that exist stably under high pressure. Aqueous alkali metal polynitrogen Pmn2 ₁ -NaN ₅ .

A method for trapping P2/c- _NaN at atmospheric pressure with confined high-density anhydrous alkali metal polynitrogen, comprising the following steps:

Sodium azide confined in boron nitride nanotubes is packaged in a diamond-anvil high-pressure cavity, pressurized to above 50GPa, then subjected to 2000-2300K laser heat treatment, and then released to normal pressure to obtain Confined high-density anhydrous alkali metal polynitrogen P2/c-NaN ₅ that exists stably under the hood.

Preferably, the pressurized pressure transmission medium is liquid argon or liquid neon.

Preferably, the preparation method of the diamond-to-anvil high-pressure chamber is as follows: using rhenium foil as a gasket material, using diamond to anvil to pre-press the rhenium foil to form an indentation; A hole is formed in the center as a high-pressure chamber.

Preferably, the thickness of the pre-pressed rhenium foil is 40-60 μm.

The present invention provides confined high-density anhydrous alkali metal polynitrogen Cm-NaN ₅ obtained by the method described in the scheme above.

The present invention provides confined high-density anhydrous alkali metal polynitrogen Pmn2 ₁ -NaN ₅ obtained by the method described in the scheme above.

The present invention provides confined high-density anhydrous alkali metal polynitrogen P2/c-NaN ₅ obtained by the method described in the scheme above.

The invention provides a high-pressure preparation method of confined high-density anhydrous alkali metal polynitrogen Cm-NaN ₅ , which comprises the following steps: encapsulating azide confined in boron nitride nanotubes in a diamond-anvil high-pressure chamber Sodium chloride, and then pressurized to above 35GPa to obtain confined high-density anhydrous alkali metal polynitrogen Cm-NaN ₅ that exists stably under high pressure. The present invention utilizes high-pressure conditions to make NaN ₃ undergo a structural phase transition, wherein the azide N ₃ ^- dissociates and polymerizes to form an N ₅ ^-ring , thereby obtaining confined high-density anhydrous alkali metal polynitrogen that can exist stably under high pressure Cm—NaN ₅ .

The invention provides a high-temperature and high-pressure preparation method of confined high-density anhydrous alkali metal polynitrogen Pmn2 ₁ -NaN ₅ , comprising the following steps: encapsulating boron nitride nanotubes confined in a diamond-anvil high-pressure cavity Sodium azide is pressurized to above 50GPa, and then subjected to 2000-2300K laser heat treatment to obtain confined high-density anhydrous alkali metal polynitrogen Pmn2 ₁ -NaN ₅ that exists stably under high pressure. The invention uses high temperature to promote the complete transformation of NaN ₃ over a higher potential barrier to NaN ₅ structure, and makes the crystallinity of the NaN 5 structure better.

The present invention also provides a method for trapping confined high-density anhydrous alkali metal polynitrogen P2/c-NaN ₅ at atmospheric pressure, comprising the following steps: encapsulating confined boron nitride nanotubes in a high-pressure chamber with a diamond counter-anvil Sodium azide in the solution is pressurized to above 50GPa, then 2000-2300K laser heat treatment is performed, and then the pressure is released to obtain confined high-density anhydrous alkali metal polynitrogen P2/c-NaN that exists stably at normal temperature and pressure. ₅ . The invention uses high temperature to promote the complete transformation of NaN ₃ to NaN ₅ structure, and makes the NaN 5 structure better crystallinity, and at the same time realizes the atmospheric pressure interception of NaN ₅ under the confinement effect of the boron nitride tube.

In addition, the high-temperature and high-pressure preparation method and atmospheric pressure interception method provided by the present invention do not require harsh experimental conditions, and the method is simple and easy to operate.

Description of drawings

Figure 1 is the high-pressure in-situ Raman spectrum of Cm-NaN ₅ @BNNTs prepared in Example 1 under a pressure of 35GPa;

Fig. 2 is the high-pressure in-situ synchrotron radiation angular dispersion XRD spectrum of Cm-NaN ₅ @BNNTs prepared in Example 1 at 35GPa;

Figure 3 is the 3D crystal structure diagram of Cm-NaN ₅ , Pmn2 ₁ -NaN ₅ and P2/c-NaN ₅ , where (a) is the 3D crystal structure diagram of Cm-NaN ₅ , and (b) is Pmn2 ₁ -NaN ₅ The 3D crystal structure diagram of , (c) is the 3D crystal structure diagram of P2/c-NaN ₅ ;

Figure 4 is the high-pressure in-situ Raman spectrum of Cm-NaN ₅ @BNNTs prepared in Example 2 under a pressure of 43GPa;

Fig. 5 is the high-pressure in-situ synchrotron radiation angular dispersion XRD spectrum of Cm-NaN ₅ @BNNTs prepared in Example 2 at 43GPa;

Figure 6 is the high-pressure in-situ Raman spectrum of Cm-NaN ₅ @BNNTs prepared in Example 3 under a pressure of 115GPa;

Fig. 7 is the high pressure in situ synchrotron radiation angular dispersion XRD spectrum of Cm-NaN ₅ @BNNTs prepared in Example 3 at 115GPa;

Figure 8 is the high-pressure in-situ Raman spectrum of Pmn2 ₁ -NaN ₅ @BNNTs prepared in Example 4 under a pressure of 50GPa;

Fig. 9 is the high pressure in situ synchrotron radiation angular dispersion XRD spectrum of Pmn2 ₁ -NaN ₅ @BNNTs prepared in Example 4 under 50GPa;

Figure 10 is the Raman spectrum of P2/c-NaN ₅ @BNNTs prepared in Example 5 under normal temperature and pressure conditions;

Fig. 11 is the synchrotron radiation XRD spectrum of P2/c-NaN ₅ @BNNTs prepared in Example 5 under normal temperature and pressure conditions.

Detailed ways

The invention provides a high-pressure preparation method of confined high-density anhydrous alkali metal polynitrogen Cm-NaN ₅ , comprising the following steps:

Sodium azide confined in boron nitride nanotubes is encapsulated in a diamond-anvil high-pressure cavity, and then pressurized to above 35GPa to obtain a confined high-density anhydrous alkali metal polynitrogen Cm-NaN that exists stably under high pressure ₅ .

In the present invention, the method for preparing the diamond-to-anvil high-pressure cavity is preferably: use rhenium foil as the gasket material, use diamond to anvil to pre-press the rhenium foil, and use a laser drilling machine to form a Holes, as high-pressure chambers. In the present invention, the thickness of the pre-pressed rhenium foil is preferably 40-60 μm; the diameter of the hole is preferably 1/3 of the diameter of the anvil surface of the diamond opposite to the anvil. In a specific embodiment of the present invention, when the diamond When the diameter of the anvil surface is 200 μm, the diameter of the hole is preferably 60-70 μm; the pressurized pressure transmission medium is preferably liquid argon or liquid neon, more preferably liquid argon, in the specific embodiment of the present invention Among them, it is preferable to use ruby microspheres below 10 μm as the pressure marking material to calibrate the pressure in the high pressure chamber.

In the present invention, the sodium azide confined in boron nitride nanotubes is specifically a NaN ₃ @BNNTs confined nanocomposite material, by confining sodium azide in boron nitride nanotubes Obtained; the present invention has no special requirements for the sodium azide confined in boron nitride nanotubes, and can be prepared by methods well known to those skilled in the art or purchased for use.

In the present invention, sodium azide confined in boron nitride nanotubes will be packaged in the high-pressure cavity of the diamond counter-anvil, and then pressurized to above 35GPa, specifically 35GPa, 43GPa or 115GPa. Under the action of pressure, NaN ₃ A structural phase transition occurs, wherein the azide N ₃ ^- dissociates and polymerizes to form an N ₅ ^-ring , thereby obtaining NaN ₅ , which is prepared under high pressure in the present invention. The high-density anhydrous alkali metal polynitrogen NaN ₅ in boron nitride nanotubes, whose space group is Cm, is denoted as Cm-NaN ₅ @BNNTs (where BNNTs represents boron nitride nanotubes).

The present invention also provides a high-temperature and high-pressure preparation method of confined high-density anhydrous alkali metal polynitrogen Pmn2 ₁ -NaN ₅ , comprising the following steps:

Sodium azide confined in boron nitride nanotubes is encapsulated in a diamond-anvil high-pressure cavity, pressurized to above 50GPa, and then subjected to 2000-2300K laser heating treatment to obtain a stable high-density confinement under high pressure Anhydrous alkali metal polynitrogen Pmn2 ₁ -NaN ₅ .

In the present invention, the preparation method of the diamond-to-anvil high-pressure chamber and the pressurized medium are consistent with the above-mentioned scheme, and will not be repeated here; the sodium azide and the sodium azide confined in the boron nitride nanotube The above solutions are consistent and will not be repeated here.

After the packaging is completed, the present invention pressurizes to above 50GPa, specifically 50GPa or 60GPa, and then performs 2000-2300K laser heat treatment, preferably 2100-2200K laser heat treatment. The present invention preferably uses a fiber laser with a wavelength of 1064nm for laser heating treatment. The present invention has no special requirements on the specific conditions of the laser heating treatment, as long as the required temperature can be reached. In the present invention, laser is used for heating treatment, high temperature can promote the complete transformation of NaN ₃ over a higher potential barrier to NaN ₅ structure, and make the crystallinity of NaN 5 structure better; the present invention obtains through pressure and laser heating treatment Specifically, it is a high-density anhydrous alkali metal polynitrogen NaN ₅ that exists stably under high pressure and is confined in boron nitride nanotubes. Its space group is Pmn2 ₁ , which is denoted as Pmn2 ₁ -NaN ₅ @BNNTs( where BNNTs represent boron nitride nanotubes).

The present invention also provides a method for trapping high-density anhydrous alkali metal polynitrogen P2/c- _NaN5 at atmospheric pressure, which includes the following steps:

Sodium azide confined in boron nitride nanotubes is packaged in a diamond-anvil high-pressure cavity, pressurized to above 50GPa, then subjected to 2000-2300K laser heat treatment, and then released to normal pressure to obtain Confined high-density anhydrous alkali metal polynitrogen P2/c-NaN ₅ that exists stably under the hood.

In the present invention, the preparation method of the diamond-to-anvil high-pressure chamber and the pressurized medium are consistent with the above-mentioned scheme, and will not be repeated here; the sodium azide and the sodium azide confined in the boron nitride nanotube The above solutions are consistent and will not be repeated here.

After the packaging is completed, the present invention pressurizes to more than 50GPa, specifically 50GPa, 53GPa or 58GPa, and then performs 2000-2300K laser heat treatment, preferably 2100-2200K laser heat treatment, and then performs pressure relief. The present invention preferably uses a fiber laser with a wavelength of 1064nm for laser heating treatment. The present invention has no special requirements on the specific conditions of the laser heating treatment, as long as the required temperature can be reached. In the present invention, laser is used for heating treatment. High temperature can promote the complete transformation of NaN ₃ over a higher potential barrier to NaN ₅ structure, and make the crystallinity of NaN 5 structure better. At the same time, under the confinement effect of boron nitride tube, Realize the interception of NaN ₅ at normal pressure; what the present invention obtains under normal pressure is specifically a high-density anhydrous alkali metal polynitrogen NaN ₅ that exists stably at normal temperature and pressure and is confined in boron nitride nanotubes , whose space group is P2/c, denoted as P2/c-NaN ₅ @BNNTs (wherein BNNTs represent boron nitride nanotubes).

The present invention also provides confined high-density anhydrous alkali metal polynitrogen Cm-NaN ₅ , Pmn2 ₁ -NaN ₅ and P2/c-NaN ₅ obtained by the method described in the scheme above. The present invention obtains the confined high-density anhydrous alkali metal polynitrogen Cm-NaN ₅ and Pmn2 ₁ -NaN ₅ stably existing under high pressure for the first time; Domain high-density anhydrous alkali metal polynitrogen P2/c-NaN ₅ ; Cm-NaN ₅ , Pmn2 ₁ -NaN ₅ and P2/c-NaN ₅ provided by the present invention are sodium-based pentazoles coordinated only by metal sodium ions Structural compound, the sodium-based pentazole skeleton structure does not contain water molecules, and has a relatively high energy density. In the present invention, based on the calculation of the decomposition of NaN ₅ structure into NaN ₃ and N ₂ under the corresponding pressure, Cm-NaN ₅ under 35GPa The theoretical energy density of Pmn2 ₁ -NaN ₅ at 50GPa is 114.7kJ/mol, and that of P2/c-NaN ₅ at 0GPa is 81.5kJ/mol.

The technical solutions in the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention.

Example 1

Select a diamond with an anvil surface of 200 microns to generate high pressure on the anvil, and a metal rhenium foil with a purity of 99.97% as the gasket material, use the diamond to pre-press the anvil on the gasket material to form an indentation, and use laser drilling The machine forms a circular hole with a diameter of 70 microns in the center of the indentation as a sample cavity for encapsulating NaN ₃ @BNNTs confinement nanocomposites; encapsulating liquid argon as a pressure transmission medium, and then filling ruby microspheres below 10 μm as a pressure medium. The standard substance is used to calibrate the pressure in the sample chamber. Rotate the diamond against the anvil to pressurize the nut, and carry out pressure loading under normal temperature conditions. When the pressure is increased to 35GPa, the confined high-density anhydrous alkali metal polynitrogen Cm-NaN ₅ can be obtained, which is denoted as Cm-NaN ₅ @BNNTs.

Figure 1 and Figure 2 are the high-pressure in-situ Raman spectrum of Cm-NaN ₅ @BNNTs at a pressure of 35GPa (the black arrow in the figure represents the characteristic vibration of the N ₅ ^-ring ) and the high-pressure in-situ synchrotron radiation angular dispersion XRD spectrum, respectively (* marked as the diffraction peak of Cm-NaN ₅ phase in the figure), (a) in Figure 3 is the 3D crystal structure diagram of Cm-NaN ₅ . In the high-pressure in-situ Raman spectrum, the three characteristic peaks at 200-400cm ^-1 are the lattice vibration modes of NaN ₃ high-pressure phase γ-NaN ₃ (space group I4/mcm), and the characteristic peaks at 650cm ^-1 are The bending vibration mode of N ₃ ^- in γ-NaN ₃ , the characteristic peak at 1490cm ^-1 is the symmetrical stretching vibration mode of N ₃ ^- in γ-NaN ₃ . The black arrows in the figure indicate three new broad peaks, which are in good agreement with the theoretically calculated Raman peak position of the Cm-NaN ₅ structure in the theoretical prediction. The Raman vibration peak at ~280cm ^-1 is N ₅ ^- For the lattice vibration of the ring, the Raman vibration peak at 800cm ^-1 is the N ₅ ^-ring bending vibration, and the Raman vibration peak at ~1100cm ^-1 is attributed to the N ₅ ^-ring asymmetric breathing and angular deformation vibration. In the high-pressure in-situ synchrotron radiation angular dispersion XRD spectrum, the new diffraction peak at 35GPa is in good agreement with the theoretical prediction spectrum of the Cm-NaN ₅ structure. In addition, during the phase transition from the I4/mcm-NaN ₃ structure to the Cm-NaN ₅ structure, the formation of the Cmmm-NaN ₂ structure was accompanied.

Example 2

The press, sample chamber and pressure transmission medium are the same as those in Embodiment 1. A proper amount of confinement nanocomposite NaN ₃ @BNNTs is filled into the sample cavity, ruby microspheres are added as a pressure mark (to detect the pressure in the pressure cavity), and liquid argon is sealed in as a pressure transmission medium for pressurization. When the pressure is increased to 43GPa, confined high-density anhydrous alkali metal polynitrogen Cm-NaN ₅ @BNNTs can be obtained. Figure 4 and Figure 5 are the high-pressure in-situ Raman spectrum of the sample under a pressure of 43GPa (the black arrow in the figure represents the characteristic vibration of the N ₅ ^-ring .) and the high-pressure in-situ synchrotron radiation angular dispersion XRD spectrum (in the figure * Marked as Cm-NaN ₅ phase diffraction peak), according to Figure 4 and Figure 5, it can be known that NaN ₅ was successfully obtained under high pressure in this embodiment.

Example 3

The press, sample chamber and pressure transmission medium are the same as those in Embodiment 1. A proper amount of confinement nanocomposite NaN ₃ @BNNTs is filled into the sample cavity, ruby microspheres are added as a pressure mark (to detect the pressure in the pressure cavity), and liquid argon is sealed in as a pressure transmission medium for pressurization. When the pressure is increased to 115GPa, the confined high-density anhydrous alkali metal polynitrogen NaN ₅ can be obtained, which is denoted as Cm-NaN ₅ @BNNTs.

The samples in the sample chamber were characterized by high-pressure in-situ Raman spectroscopy and high-pressure in-situ synchrotron radiation angular dispersion XRD, and the results are shown in Figures 6 and 7. Under the condition of 115GPa, the Raman spectrum shows the characteristic Raman vibration of NaN ₅ : the Raman vibration peak at 300-500cm ^-1 is attributed to the lattice vibration of the N ₅ ^-ring , and the Raman vibration peak at 830cm ^-1 It is attributed to the bending vibration of the N ₅ ^-ring , and the Raman vibration peak at 1160cm ^-1 is attributed to the asymmetric breathing and angular deformation vibration of the N ₅ ^-ring . The characteristic peaks of N ₃ ^-bending vibration in the range of 400-750cm ^-1 and the characteristic peaks of N ₃ -symmetric stretching vibration in the range of 1560cm ^-1 completely disappeared, marking the ^complete transformation of γ-NaN ₃ to NaN ₅ . The high-pressure in situ synchrotron radiation XRD pattern is consistent with the results of Cm-NaN ₅ .

Example 4

The press, sample chamber and pressure transmission medium are the same as those in Embodiment 1. A proper amount of confinement nanocomposite NaN ₃ @BNNTs is filled into the sample cavity, ruby microspheres are added as a pressure mark (to detect the pressure in the pressure cavity), and liquid argon is sealed in as a pressure transmission medium for pressurization. When the pressure was increased to 50GPa, the sample in the sample cavity was heated to 2000K by high-pressure in-situ laser, and the confined high-density anhydrous alkali metal polynitrogen Pmn2 ₁ -NaN ₅ @BNNTs that existed stably under high pressure was obtained.

Figure 8 and Figure 9 are the Raman spectrum and synchrotron radiation angular dispersion XRD spectrum of the sample under the condition of 50GPa respectively, and (b) in Figure 3 is the 3D crystal structure diagram of Pmn2 ₁ -NaN ₅ . N ₅ ^{-characteristic} vibrations appear in the Raman spectrum after laser heating: the two Raman broadband at 150-540cm ^-1 belong to the lattice vibration of N ₅ ^-ring , and the Raman vibration peak at 800cm ^-1 belongs to The bending vibration of the N ₅ ^-ring , the Raman vibration peaks at 1036 and 1170 cm ^-1 are attributed to the asymmetric breathing and angular deformation vibration of the N ₅ ^-ring . This is in good agreement with the theoretically calculated Raman peak position of the Pmn2 ₁ -NaN ₅ structure in the theoretical prediction. The high-pressure in situ synchrotron radiation angular dispersion XRD spectrum is consistent with the theoretically calculated spectrum of the Pmn2 ₁ -NaN ₅ structure.

Example 5

The press, sample chamber and pressure transmission medium are the same as those in Embodiment 1. A proper amount of confinement nanocomposite NaN ₃ @BNNTs is filled into the sample cavity, ruby microspheres are added as a pressure mark (to detect the pressure in the pressure cavity), and liquid argon is sealed in as a pressure transmission medium for pressurization. When the pressure is increased to 50GPa, the sample in the sample chamber is heated to 2000K by high-pressure in-situ laser, and then the sample is depressurized to normal pressure to obtain the confined high-density anhydrous alkali metal polynitrogen P2/ c-NaN ₅ @BNNTs.

Figure 10 and Figure 11 are the Raman spectrum and synchrotron radiation angular dispersion XRD spectrum of the sample under normal temperature and pressure conditions respectively, and (c) in Figure 3 is the 3D crystal structure diagram of P2/c-NaN ₅ . N ₅ ^{-characteristic} vibration peaks appear in the normal temperature and pressure Raman spectrum, located at 119cm ^-1 , 831cm ^-1 , 998cm ^-1 , 1115cm ^-1 and 1180cm ^-1 , which is consistent with the theoretical prediction of the P2/c-NaN ₅ structure The calculated Raman peak positions are in good agreement. The normal temperature and pressure synchrotron radiation angular dispersion XRD spectrum is consistent with the theoretical calculation spectrum of the P2/c-NaN ₅ structure.

The above is only a preferred embodiment of the present invention, it should be pointed out that for those skilled in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, and these improvements and modifications are also It should be regarded as the protection scope of the present invention.

Claims (3)

1. Limited high-density anhydrous alkali metal polymeric nitrogen Cm-NaN ₅ Is characterized by comprising the following steps:

packaging sodium azide with a confinement in a boron nitride nanotube in a diamond anvil cell high-pressure cavity, and then pressurizing to above 35GPa to obtain a confinement high-density anhydrous alkali metal polymeric nitrogen Cm-NaN stably existing under high pressure ₅ The method comprises the steps of carrying out a first treatment on the surface of the The pressurized pressure transmission medium is liquid argon or liquid neon.

2. The method of claim 1, wherein the diamond anvil cell is prepared by: using rhenium foil as a sealing gasket material, and prepressing the rhenium foil by utilizing a diamond anvil cell to form an indentation; and forming a hole in the center of the indentation by using a laser puncher to serve as a high-pressure cavity.

3. The method of claim 2, wherein the pre-pressed rhenium foil has a thickness of 40-60 μm.

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