Polymeric nitrogen and high-yield synthesis method thereof

Abstract

The invention belongs to the technical field of solid energetic materials, and particularly relates to polymeric nitrogen and a high-yield synthesis method thereof. The invention discloses a low-cost and high-yield polymer nitrogen preparation method which comprises the following steps: by taking a multi-nitrogen compound as a precursor, obtaining polymer nitrogen which can be stably stored in a normal-temperature and normal-pressure environment by optimizing a heat treatment condition under a high vacuum or atmosphere protection condition; the problems that polymeric nitrogen can only be synthesized in a high-temperature and high-pressure environment and the stability is poor at normal temperature and normal pressure are solved. The synthesis method is simple in process and high in yield, and provides possibility for engineering application of polymer nitrogen in the future.

Description

Technical Field

[0001] The invention belongs to the technical field of solid energetic materials, and in particular relates to polymerized nitrogen and a high-yield synthesis method thereof. Background Art

[0002] Polymerized nitrogen is a new network structure formed by the dissociation of diatomic nitrogen molecules and bonded by nitrogen-nitrogen single bonds. According to theoretical calculations, cubic deflected polymerized nitrogen (cg-N), as the most popular polymerized nitrogen material, is a single substance composed of nitrogen atoms. One nitrogen atom is bonded to three adjacent nitrogen atoms in the form of covalent nitrogen-nitrogen single bonds, and its structure is similar to diamond. Due to the bond energy difference between nitrogen-nitrogen bonds, the bond energy of the N≡N triple bond is 954kJ / mol, while the NN single bond is 160kJ / mol. Therefore, cg-N will release a large amount of energy during the decomposition process, and is a new type of high-energy material.

[0003] Erements et al. successfully synthesized cg-N for the first time using molecular nitrogen with the help of a diamond anvil cell at a pressure of 110 GPa and a temperature above 2000 K (Eremets, M., Gavriliuk, A., Trojan, I. et al. Single-bonded cubic form of nitrogen. Nature Mater 3, 558–563, 2004). In addition, patent CN202211709768.7 discloses a method for preparing cg-N, which can be prepared in a high temperature and high pressure environment and can be stored stably for a long time at room temperature and pressure. The polymerized nitrogen prepared by the above method is mainly synthesized under high pressure. In 2017, Benchafia et al. used the confinement effect of carbon nanotubes to confine sodium azide, synthesized polymerized nitrogen at normal pressure by plasma chemical vapor deposition, and verified the cubic deflection structure of polymerized nitrogen by structural characterization, proving for the first time that cg-N can exist under room temperature and pressure conditions. In 2022, Zhuang Hai-zheng and others once again used carbon nanotubes to confine sodium azide and prepared cg-N that can exist at normal pressure by plasma chemical vapor deposition. However, the sodium azide used in the preparation of polymerized nitrogen at normal pressure is highly toxic, the preparation process is relatively cumbersome, the yield of the prepared polymerized nitrogen is low, and the stability time is short at normal pressure and room temperature. These problems have limited the application of polymerized nitrogen to a certain extent. Summary of the invention

[0004] In view of the shortcomings of the above-mentioned prior art, one of the purposes of the present invention is to provide a method for preparing a high-yield polymerized nitrogen, which mainly heat-treats a polynitrogen precursor under atmosphere and vacuum controllable annealing conditions, thereby realizing a method for synthesizing a high-yield polymerized nitrogen material. The method has a simple preparation process, an easy-to-control reaction process, a short production cycle, and low cost, thus overcoming the problems of harsh synthesis conditions and complex preparation processes of current polymerized nitrogen materials.

[0005] To achieve the above object, the present invention adopts the following technical scheme: a method for preparing high-yield polymeric nitrogen, comprising the following steps:

[0006] Step A, taking a polynitrogen compound powder, placing it in a tube furnace without pretreatment or after pretreatment, wherein the polynitrogen compound powder is one or a combination of two or more of potassium azide and sodium azide;

[0007] Step B, after sealing the tube furnace, evacuate or fill it with protective gas, heat it to 150-320° C. and keep it at that temperature for 10-240 minutes, and cool it to room temperature to obtain polymerized nitrogen.

[0008] As a further improvement of the preparation method for synthesizing high-yield polymeric nitrogen:

[0009] Preferably, the pretreatment is grinding, or recrystallization, or tableting, or grinding first and then tableting, or recrystallization first and then tableting.

[0010] Preferably, the specific process of the grinding treatment is: grinding the polynitrogen compound powder for 10 minutes to 4 hours.

[0011] Preferably, the specific process of the recrystallization is: dissolving the polynitrogen compound powder in water or an organic solvent, then heating to evaporate the solvent, and the polynitrogen compound is recrystallized and precipitated.

[0012] Preferably, the specific process of the tableting treatment is: placing the polynitrogen compound powder or the ground polynitrogen compound powder or the recrystallized polynitrogen compound powder in a tablet press mold, applying a pressure of 10MPa-15MPa to obtain a tablet, the tablet thickness is 0.1mm-2cm, and the tablet radius is 0.1mm-5cm.

[0013] Preferably, after the tubular furnace in step B is sealed, a protective gas is passed through for washing and evacuation to a vacuum, and the steps of passing the protective gas to normal pressure and evacuation to a vacuum are repeated 3 to 5 times, and finally the vacuuming or protective gas filling state is maintained.

[0014] Preferably, the vacuum degree of the evacuation in step B ranges from one standard atmospheric pressure to 5×10 -4 torr.

[0015] Preferably, the protective gas of the tubular furnace in step B is one of high-purity argon and high-purity nitrogen, or a mixed gas of high-purity argon and high-purity nitrogen.

[0016] Preferably, the heating rate in step B is 5 to 20° C. / min.

[0017] The second object of the present invention is to provide a polymeric nitrogen obtained by any one of the above-mentioned methods for preparing a high-yield polymeric nitrogen.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] It can be seen from the technical solution provided by the present invention that the present invention provides a method for preparing high-yield polymerized nitrogen, which uses a polynitrogen compound as a precursor, which is dried and ground into powder or pressed into a sheet structure, and then placed in a high-temperature tubular furnace for calcination to obtain polymerized nitrogen. The method has a simple preparation process, does not require special instruments and drugs, is easy to control the reaction process, has a short production cycle, is low in cost, and is suitable for mass production. It solves the problems of polymerized nitrogen being unable to be synthesized and unstable due to the preparation method, and is very suitable for the preparation of high-yield, high-quality polymerized nitrogen materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0021] Figure 1 is the Raman curve of the polymerized nitrogen prepared in Example 1;

[0022] Figure 2 This is the differential scanning calorimetry curve of the polymerized nitrogen prepared in Example 1. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present invention.

[0024] Example 1

[0025] This embodiment provides a method for preparing high-yield polymerized nitrogen, which specifically comprises the following steps:

[0026] Step 1: Weigh 0.1 g of polynitrogen compound powder (potassium azide) and place it in a crucible;

[0027] Step 2: Place the crucible sample in step 1 in the constant temperature zone of the tube furnace. After the flanges at both ends of the tube furnace are sealed, perform gas washing on the tube furnace at room temperature: first vacuumize to 3*10 -2 torr, then ventilate to normal pressure, repeat the process of evacuating and ventilating to normal pressure three times, and finally introduce high-purity argon (Ar≥99.999%) as protective gas;

[0028] Step 3: Heat the sample in the tube furnace from room temperature to 250°C at a rate of 10°C / min, keep the temperature for 240 minutes, and finally cool it naturally to room temperature to obtain polymerized nitrogen powder. The yield is calculated to be 1.5%.

[0029] Example 2

[0030] This embodiment provides a method for preparing high-yield polymerized nitrogen, which specifically comprises the following steps:

[0031] Step 1: Weigh 0.1 g of polynitrogen compound powder (sodium azide) and place it in a crucible;

[0032] Step 2: Place the crucible sample in step 1 in the constant temperature zone of the tube furnace. After the flanges at both ends of the tube furnace are sealed, perform gas washing on the tube furnace at room temperature: first vacuumize to 3*10 -2 torr, then ventilate to normal pressure, repeat the process of evacuating to vacuum and then ventilating to normal pressure 4 times, and finally evacuate to vacuum 3*10 -2 torr status;

[0033] Step 3: Heat treat the sample in the tube furnace and adjust the vacuum range to 7*10 -2 torr, and then heated from room temperature to 320°C at a rate of 10°C / min, and kept at that temperature for 200 min, and finally cooled naturally to room temperature, thereby obtaining polymerized nitrogen powder. The yield was calculated to be 1.5%.

[0034] Example 3

[0035] This embodiment provides a method for preparing high-yield polymerized nitrogen, which specifically comprises the following steps:

[0036] Step 1: Weigh 0.1 g of polynitrogen compound powder (potassium azide and sodium azide mixed in a ratio of 1:1) and grind it in a mortar for 240 min.

[0037] Step 2: Apply 10 MPa pressure to the ground sample to obtain a pressed sheet with a sheet thickness of 0.1 mm and a sheet radius of 0.5 cm;

[0038] Step 3: Place the sheet sample in the constant temperature zone of the tube furnace. After the flanges at both ends of the tube furnace are sealed, perform gas washing on the tube furnace at room temperature: first vacuumize to 3*10 -2 torr, then ventilate to normal pressure, repeat the process of evacuating to vacuum and then ventilating to normal pressure 3 times, and finally evacuate to vacuum 3*10 -2 torr status;

[0039] Step 4: Heat-treat the sample in the tube furnace, using high-purity argon (Ar≥99.999%) as protective gas, heating from room temperature to 150°C at a rate of 5°C / min, and keeping the temperature for 30 minutes, and finally cooling naturally to room temperature, thereby obtaining polymerized nitrogen powder. The yield is calculated to be 1%.

[0040] Example 4

[0041] This embodiment provides a method for preparing high-yield polymerized nitrogen, which specifically comprises the following steps:

[0042] Step 1: Weigh 0.1 g of polynitrogen compound powder (potassium azide) and grind it in a mortar for 10 min;

[0043] Step 2: Apply a pressure of 15 MPa to the ground sample to obtain a pressed sheet with a sheet thickness of 0.5 cm and a sheet radius of 1.5 cm;

[0044] Step 3: Place the sheet sample in the constant temperature zone of the tube furnace. After the flanges at both ends of the tube furnace are sealed, perform gas washing on the tube furnace at room temperature: first vacuumize to 3*10 -2 torr, and then ventilate to normal pressure. Repeat the process of evacuating to vacuum and then ventilating to normal pressure for 3 times. Finally, evacuate to vacuum for 3*10 -2 torr status;

[0045] Step 4: Heat treat the sample in the tube furnace and adjust the vacuum degree to 5×10 -4 torr, the temperature was raised from room temperature to 320°C at a rate of 20°C / min, and kept at that temperature for 240min, and finally cooled naturally to room temperature, thereby obtaining polymerized nitrogen powder. The yield was calculated to be 1.4%.

[0046] Example 5

[0047] This embodiment provides a method for preparing high-yield polymerized nitrogen, which specifically comprises the following steps:

[0048] Step 1: Weigh 0.1 g of polynitrogen compound powder (sodium azide) and place it in a container;

[0049] Step 2: adding water to dissolve the polynitrogen compound to obtain a polynitrogen compound solution;

[0050] Step 3: heating the solution prepared in step 2 to evaporate the solvent, so that the polynitrogen compound is precipitated, filtering the precipitated sample and drying it to obtain a dry sample;

[0051] Step 4: Place the dried sample in step 4 in the constant temperature zone of the tube furnace. After the flanges at both ends of the tube furnace are sealed, perform gas washing on the tube furnace at room temperature: first vacuumize to 3*10 -2 torr, then ventilate to normal pressure, repeat the process of evacuating to vacuum and then ventilating to normal pressure 3 times, and finally evacuate to vacuum 3*10 -2 torr status;

[0052] Step 5: Heat treat the sample in the tube furnace and adjust the vacuum degree to 5×10 -4 torr, the temperature was raised from room temperature to 250°C at a rate of 10°C / min, and kept at that temperature for 120 minutes, and finally cooled naturally to room temperature, thereby obtaining polymerized nitrogen powder. The yield was calculated to be 1%.

[0053] Example 6

[0054] This embodiment provides a method for preparing high-yield polymerized nitrogen, which specifically comprises the following steps:

[0055] Step 1: Weigh 0.1 g of polynitrogen compound powder (potassium azide and sodium azide mixed in a ratio of 1:1) and place it in a container;

[0056] Step 2: Dissolve the polynitrogen compound in step 1 using water or an organic solvent to prepare a solution from the powder sample in step 1;

[0057] Step 3: heating the solution prepared in step 2 to evaporate the solvent, so that the polynitrogen compound is precipitated, filtering the precipitated sample and drying it to obtain a dry sample;

[0058] Step 4: Place the dried sample in the constant temperature zone of the tube furnace. After the flanges at both ends of the tube furnace are sealed, perform gas washing on the tube furnace at room temperature: first vacuumize to 3*10 -2 torr, then ventilate to normal pressure, repeat the process of evacuating to vacuum and then ventilating to normal pressure 5 times, and finally evacuate to vacuum 3*10 -2 torr status;

[0059] Step 5: Heat treat the sample in the tube furnace and adjust the vacuum degree to 4×10 -2 torr, the temperature was raised from room temperature to 300°C at a rate of 15°C / min, and kept at that temperature for 180 min, and finally cooled naturally to room temperature, thereby obtaining polymerized nitrogen powder. The yield was calculated to be 1%.

[0060] Figure 1 Raman curve of polymerized nitrogen prepared in Example 1; 637 cm-1 It is the characteristic peak of cg-N, which confirms the successful synthesis of cg-N.

[0061] Figure 2 This is the differential scanning calorimetry curve of the polymerized nitrogen prepared in Example 1; it confirms that the thermal decomposition temperature of cg-N is 448°C, which shows good thermal stability.

[0062] In summary, the embodiments of the present invention not only have a simple preparation process, an easy-to-control reaction process, a short production cycle, and low cost, but also the prepared polymerized nitrogen has a high yield.

[0063] Those skilled in the art should understand that the above are only some specific embodiments of the present invention, rather than all embodiments. It should be noted that for those of ordinary skill in the art, many modifications and improvements can be made, and all modifications or improvements that do not exceed the scope of protection of the present invention should be regarded as the scope of protection of the present invention.

Claims

1. A high-yield synthesis method of polymerized nitrogen, characterized in that: The following steps are involved: Step A, taking a polynitrogen compound powder, placing it in a tube furnace without pretreatment or after pretreatment, wherein the polynitrogen compound powder is one or a combination of two or more of potassium azide and sodium azide; Step B, after sealing the tube furnace, evacuate or fill it with protective gas, heat it to 150-320° C. and keep it at that temperature for 10-240 minutes, and cool it to room temperature to obtain polymerized nitrogen.

2. The high-yield synthesis method of polymerized nitrogen according to claim 1, characterized in that: The pretreatment is grinding, or recrystallization, or tableting, or grinding first and then tableting, or recrystallization first and then tableting.

3. The high-yield synthesis method of polymerized nitrogen according to claim 2, characterized in that: The specific process of the grinding treatment is: grinding the polynitrogen compound powder for 10 minutes to 4 hours.

4. The high-yield synthesis method of polymerized nitrogen according to claim 2, characterized in that: The specific process of the recrystallization is: dissolving the polynitrogen compound powder in water or an organic solvent, then heating and evaporating the solvent, and the polynitrogen compound is recrystallized and precipitated.

5. The high-yield synthesis method of polymerized nitrogen according to claim 2, characterized in that: The specific process of the tableting treatment is: placing the polynitrogen compound powder or the ground polynitrogen compound powder or the recrystallized polynitrogen compound powder in a tablet press mold, applying a pressure of 10MPa-15MPa to obtain a tablet, the tablet thickness is 0.1mm-2cm, and the tablet radius is 0.1mm-5cm.

6. The high-yield synthesis method of polymerized nitrogen according to claim 1, characterized in that: After the tubular furnace in step B is sealed, a protective gas is passed through for washing and evacuation to vacuum, and the steps of passing the protective gas to normal pressure and evacuation to vacuum are repeated 3 to 5 times, and finally the vacuuming or protective gas filling state is maintained.

7. A high-yield synthesis method of polymerized nitrogen according to claim 1 or 6, characterized in that: The vacuum degree range of the evacuation in step B is from one standard atmosphere to 5×10 -4 torr.

8. A high-yield synthesis method of polymerized nitrogen according to claim 1 or 6, characterized in that: In step B, the protective gas of the tubular furnace is one of high-purity argon and high-purity nitrogen, or a mixed gas of high-purity argon and high-purity nitrogen.

9. The high-yield synthesis method of polymerized nitrogen according to claim 1, characterized in that: The heating rate in step B is 5-20°C / min.

10. Polymerized nitrogen obtained by the high-yield synthesis method of polymerized nitrogen according to any one of claims 1 to 9.

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