CN113336610A

CN113336610A - Novel crystal form NTO elementary substance explosive and preparation method thereof

Info

Publication number: CN113336610A
Application number: CN202110561085.0A
Authority: CN
Inventors: 束庆海; 王子锋; 王俊峰; 王满曼; 金韶华; 尚凤琴; 阮健; 郁锐; 杜君宜; 束红年
Original assignee: Beijing Institute of Technology BIT
Current assignee: Beijing Institute of Technology BIT
Priority date: 2021-05-20
Filing date: 2021-05-20
Publication date: 2021-09-03
Anticipated expiration: 2041-05-20
Also published as: CN113336610B

Abstract

The invention relates to a new crystal type NTO elemental explosive and a preparation method thereof, belonging to the field of energetic materials. In the invention, NTO is used as a raw material, and the NTO elemental explosive of γ crystal form is prepared by adopting a heating and cooling method. The method comprises the following steps: at room temperature, adding NTO and a crystal form control agent into a solvent, heating up to dissolve them completely, slowly cooling down to separate out white crystals, and filtering, washing and drying to obtain γ-NTO crystals. The morphology of the γ-NTO crystal prepared by the invention is closer to a spherical shape, which is more conducive to the preparation of mixed explosives and the embodiment of safety. The thermal stability of γ-NTO is higher than that of α-NTO, and its mechanical sensitivity and acidity are smaller than those of α-NTO. The preparation process of the invention is simple, the experimental conditions are mild, and the production cost is low. The new crystal type NTO elemental explosive, as a high-energy low-sensitivity explosive, has a good application prospect.

Description

Novel crystal form NTO elementary substance explosive and preparation method thereof

Technical Field

The invention relates to a new crystal form NTO elementary substance explosive and a preparation method thereof, in particular to a new crystal form NTO elementary substance explosive and a preparation method thereof, belonging to the field of energetic materials.

Background

At present, the development mode of weaponry and war mode gradually develops towards refinement and unmanned direction, and the requirement for using insensitive ammunition is strengthened from the aspect of improving the safety of a weapon platform. Whether ammunition is insensitive depends on whether the explosive in the fighting part is insensitive. Therefore, it is important to develop insensitive ammunition to research and apply insensitive explosives with excellent safety performance. 3-nitro-1, 2, 4-triazole-5-ketone (NTO) is used as a high-energy low-sensitivity energetic material, the detonation velocity is 8550m/s, the detonation pressure is about 34.9GPa, and the energy level is equivalent to RDX; characteristic drop height h of impact sensitivity₅₀The weight is 280cm (2.5kg drop weight), and the safety performance is far superior to RDX and HMX; in addition, the heat sensitivity and the shock wave sensitivity are both at a lower level and are equivalent to TATB commonly known as wood explosives; meanwhile, NTO also has the characteristics of simple synthesis process and low manufacturing cost. Combining the above advantages, NTO is gradually receiving the general attention of scholars at home and abroad. At present, NTO is used in an insensitive ammunition formula of multi-country army, and has a good application prospect.

Polymorphism is a common phenomenon existing in crystalline explosives, and the same explosives in different crystal forms have different crystal structures and unit cell stacking structures. The crystal structure and the unit cell stacking structure of the explosive have a decisive influence on the appearance, physical characteristics, energy level and safety performance of explosive crystals. Therefore, the development of the research on the crystal structure of the explosive, particularly the research on the polymorphism of the explosive, has very important practical significance for improving the performance of the explosive.

The research finds that NTO only exists in 2 crystal forms, namely alpha crystal form (alpha-NTO) and beta crystal form (beta-NTO). The beta-NTO density is lower (1.867 g/cm)³298K) and difficult to stabilize over a long period of time, so that α -NTO is currently used in research and application of NTO. alpha-NTO has a high density (1.906 g/cm)³293K), but the crystal is in a long rod shape and easily forms twin crystal, so that the crystal defects are more, and the mixing preparation and the use of the explosive are not facilitated. Meanwhile, when the α -NTO exists in a water environment (electrolyte environment), the α -NTO shows strong acidity (pKa of 3.76), so that the α -NTO causes acidic corrosion to weapons during storage, transportation or use, the life and the use effect of the weapons are seriously affected, and the wide application of the NTO is restricted.

Disclosure of Invention

The invention aims to relieve the corrosion problem of NTO acidity to weaponry and improve the application value of NTO and mixed explosives thereof in overload-resistant ammunition; providing a new crystal form NTO elementary substance explosive and a preparation method thereof; the method prepares a new crystal form NTO elementary substance explosive which is called gamma-NTO;

the invention is realized by the following technical scheme:

a new crystal form NTO single-substance explosive (gamma-NTO) with molecular formula of C₂H₂N₄O₃Belongs to monoclinic system, Pc space group, and has a density of 1.907g/cm³(293K) The crystal structure and unit cell structure are shown in fig. 1. Unit cell parameters of the γ -NTO:

α＝90°，β＝98.420(3)°，γ＝90°；

Z＝8。

a preparation method of gamma-NTO elementary explosive comprises the following steps:

step one, preparing an NTO supersaturated solution, and adding a proper amount of a crystal form control agent; the molar ratio of the NTO to the crystal form control agent is 1: 0.1-1: 0.8;

step two, preparation of gamma-NTO crystal

And (3) heating and stirring the mixed solution prepared in the step one to completely dissolve the NTO and the crystal form control agent, slowly cooling, wherein the NTO is separated out in the cooling process and is a white crystal, and the crystal form control agent has high solubility in the solvent and is remained in the solvent in the cooling process. Filtering, washing and drying to obtain colorless and transparent gamma-NTO crystals.

The solvent of the solution is anhydrous methanol.

The crystal form control agent is one of 5-amino-1, 2, 4-triazole-3-ketone (ATO) or 4, 4' -azo-1, 2, 4-triazolone (ZTO).

In the step II, the molar ratio of NTO to the crystal form control agent is 1: 0.1-1: 0.8, and the heating temperature is 60 ℃; and step two, the cooling rate is 1-5 ℃/min, and the temperature is reduced to 20 ℃.

Advantageous effects

1. The crystal density of the gamma-NTO prepared by the invention at 293K is 1.907g/cm³Comparison of alpha-NTO (1.906 g/cm)³) The density of (A) is improved;

2. the gamma-NTO prepared by the invention is a blocky crystal which is closer to a sphere than a rodlike crystal of alpha-NTO, does not generate a polycrystalline phenomenon, has smaller mechanical sensitivity and higher thermal stability, and is more beneficial to the embodiment of the safety of NTO in practical application.

3. The acidity coefficient pKa of the gamma-NTO prepared by the invention is 4.95, which is higher than that of alpha-NTO (pKa is 3.76), thus effectively improving the acidity problem caused by H dissociation in the alpha-NTO.

4. The preparation method has the advantages of simple preparation process, simple and convenient operation, easy manufacture, mild experimental conditions and low production cost.

Drawings

FIG. 1 is a crystal structure diagram and a unit cell structure diagram of γ -NTO;

FIG. 2 shows the infrared absorption spectra of γ -NTO and α -NTO crystals, where a is the wavelength range 400-4000cm^-1Is infrared ray ofAbsorption spectra, b and c are wavelength ranges of 1660-1740cm^-1，650-700cm^-1(ii) infrared absorption spectrum of (d);

FIG. 3 is a thermogram of γ -NTO and α -NTO;

FIG. 4 is a product entity diagram of α -NTO crystals reported in the prior art;

FIG. 5 is a product physical diagram of the gamma-NTO crystal obtained in the patent.

Detailed Description

In order to make the experimental technical scheme of the invention clearer, the invention is further described in detail by combining the attached drawings and examples.

Example 1

Adding 50mL of anhydrous methanol into a three-neck flask, then adding 0.56g of NTO and 0.04g of ATO, connecting the flask with a condensation reflux device, heating to 60 ℃ under the condition of continuous stirring to completely dissolve the NTO and the ATO, slowly cooling at 5 ℃/min after keeping the temperature for 1 hour, gradually separating out white crystals at the bottom of the flask, and filtering, washing and drying after cooling to 20 ℃ to obtain the gamma-NTO crystals.

The structure of gamma-NTO was confirmed by single crystal X-ray diffractometer, and the crystal structure and unit cell structure are shown in FIG. 1. The molecular formula of gamma-NTO is C₂H₂N₄O₃Belongs to monoclinic system, Pc space group, and has a density of 1.907g/cm³(293K) In that respect The unit cell parameters are as follows:

α＝90°，β＝98.420(3)°，γ＝90°；

and Z is 8. The single crystal structure data is as follows:

example 2

Adding 100mL of anhydrous methanol into a three-neck flask, then adding 1.12g of NTO and 0.15g of ATO, connecting the flask with a condensation reflux device, heating to 60 ℃ under the condition of continuous stirring to completely dissolve the NTO and the ATO, keeping the temperature for 2 hours, then slowly cooling at 2 ℃/min, gradually separating out white crystals at the bottom of the flask, cooling to 20 ℃, filtering, washing and drying to obtain the gamma-NTO crystals. The thermal decomposition temperature of the gamma-NTO explosive is 277.59 ℃, which is higher than that of alpha-NTO (275.31 ℃), and the formation of the gamma-NTO improves the thermal stability of the NTO. The characteristic drop height value of the impact sensitivity of the gamma-NTO explosive is 300cm (2.5kg drop weight), and is improved compared with that of alpha-NTO (280cm), which shows that the impact sensitivity of the NTO is reduced and the safety of the NTO is improved due to the formation of the gamma-NTO.

Example 3

Adding 50mL of anhydrous methanol into a three-neck flask, then adding 0.56g of NTO and 0.32g of ATO, connecting the flask with a condensation reflux device, heating to 60 ℃ under the condition of continuous stirring to completely dissolve the NTO and the ATO, slowly cooling at 1 ℃/min after keeping the temperature for 0.5 hour, gradually separating out white crystals from the bottom of the flask, and filtering, washing and drying after cooling to 20 ℃ to obtain the gamma-NTO crystals. The acidic dissociation constant pKa value of the gamma-NTO explosive was found to be 4.95, higher than that of alpha-NTO (pKa 3.76), probably because in the gamma-NTO unit cell structure, the H at position 4 of the NTO triazole ring forms a strong hydrogen bond, making the dissociation of hydrogen difficult and thus reducing the acidity of the NTO.

Example 4

Adding 50mL of anhydrous methanol into a three-neck flask, then adding 0.56g of NTO and 0.52g of ZTO, connecting the flask with a condensation reflux device, heating to 60 ℃ under the condition of continuous stirring to completely dissolve the NTO and the ZTO, keeping the temperature for 1 hour, slowly cooling at 5 ℃/min, gradually separating out white crystals from the bottom of the flask, cooling to 20 ℃, filtering, washing and drying to obtain the gamma-NTO crystals. The crystal morphology of the gamma-NTO explosive is blocky, twin crystals are not easy to form, and the gamma-NTO explosive is more suitable for preparing mixed explosives than long rod-shaped alpha-NTO explosive which is easy to form twin crystals, and can improve the mechanical property and safety performance of the mixed explosives.

Example 5

Adding 250mL of anhydrous methanol into a three-neck flask, then adding 2.80g of NTO and 1.90g of ZTO, connecting the flask with a condensation reflux device, heating to 60 ℃ under the condition of continuous stirring to completely dissolve the NTO and the ZTO, keeping the temperature for 2 hours, then slowly cooling at 1 ℃/min, gradually separating out white crystals at the bottom of the flask, cooling to 20 ℃, filtering, washing and drying to obtain the gamma-NTO crystals. The acid dissociation constant pKa value of the gamma-NTO explosive was found to be 4.95. The gamma-NTO explosive is directly placed on 45^#After 30 days on the steel, no corrosion of the steel sheet was observed. Therefore, when the gamma-NTO explosive is used in the warhead, an anticorrosive layer does not need to be added in the inner layer of the shell of the warhead, the manufacturing time of the warhead is saved, and the manufacturing process and the cost of the warhead are saved. The use of the gamma-NTO explosive improves the use safety of the explosive from the source.

Example 6

Adding 250mL of anhydrous methanol into a three-neck flask, then adding 2.80g of NTO and 2.10g of ZTO, connecting the flask with a condensation reflux device, heating to 60 ℃ under the condition of continuous stirring to completely dissolve the NTO and the ZTO, slowly cooling at the speed of 2 ℃/min after keeping the temperature for 0.5 hour, gradually precipitating white crystals at the bottom of the flask, and filtering, washing and drying after cooling to 20 ℃ to obtain the gamma-NTO crystals. The detonation velocity of this gamma-NTO explosive was found to be 8565m/s, at essentially the same level as alpha-NTO (8550 m/s). The gamma-NTO explosive is expected to be applied to mixed explosives in three loading forms of pressing, casting and pouring, and can be applied to battle parts such as armor breaking, explosion killing, penetration and the like.

To show that the gamma-NTO obtained in this patent is different from the other two NTO reported in unit cell structure, the detailed unit cell parameters of the three crystal forms of NTO are specifically listed in Table 1.

TABLE 1 cell parameters for NTO of different crystal forms

FIG. 2 is γ -Infrared absorption spectra of NTO and alpha-NTO elementary explosives. As can be seen from FIG. 2, γ -NTO was 1711cm in comparison to α -NTO^-1The characteristic peak of (a) shifts to the right and splits into two peaks, indicating that the chemical environment in which the carbonyl group is located in γ -NTO changes. Furthermore, 672cm^-1There was also a weak peak pattern. The other characteristic peaks are at the same positions as the peak positions of the alpha-NTO. The above results indicate that a new crystalline form is formed.

FIG. 3 is a thermogram of γ -NTO and α -NTO. As can be seen from the figure, at 262.50 ℃, the weight loss phenomenon of the gamma-NTO crystal occurs, and the peak temperature of the exothermic peak is 277.59 ℃ along with the exothermic phenomenon, namely the thermal decomposition temperature of the gamma-NTO. The thermal decomposition temperature of gamma-NTO was increased by 2.28 ℃ compared to the peak temperature of the exothermic peak of alpha-NTO (275.31 ℃).

Fig. 4 and 5 are product object diagrams of alpha-NTO and gamma-NTO, respectively. As can be seen from the figure, the structure of the gamma-NTO is regular, the crystal appearance is blocky crystal, and the crystal is more approximate to a sphere compared with the rod-shaped crystal of the alpha-NTO, thereby being beneficial to the preparation of the mixed explosive and the embodiment of the safety performance.

In addition, the impact sensitivity of the gamma-NTO explosive was tested using the characteristic falling height method. The result shows that the impact sensitivity of the gamma-NTO explosive is 300cm (2.5kg drop hammer), which shows that the mechanical sensitivity of the gamma-NTO explosive is lower than that of the alpha-NTO (280cm), the gamma-NTO explosive has better safety performance, and the application of the NTO and the mixed explosive thereof in overload resistant ammunition is promoted.

The acid dissociation constant pKa value of the gamma-NTO explosive measured by a titration method is 4.95 and is higher than that of the alpha-NTO, which shows that the acidity of the gamma-NTO explosive is weaker than that of the alpha-NTO explosive, so that the storage life is prolonged;

the above detailed description is intended to illustrate the objects, aspects and advantages of the present invention, and it should be understood that the above detailed description is only exemplary of the present invention and is not intended to limit the scope of the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims

1. a new crystal form NTO elemental explosive, is characterized in that: γ-NTO molecular formula is C ₂ H ₂ N ₄ O ₃ , belongs to monoclinic crystal system, Pc space group, and density is 1.907g/cm ³ (293K), The acidity coefficient pKa=4.95; its crystal structure and unit cell structure are shown in Figure 1.

2. prepare the method for elemental explosive as claimed in claim 1, it is characterized in that: comprise the steps:

Step 1. Preparation of NTO supersaturated solution, adding an appropriate amount of crystal form control agent; the molar ratio of NTO to crystal form control agent is 1:0.1～1:0.8;

Step 2. Preparation of γ-NTO crystals

The mixed solution prepared in step 1 is heated and stirred to completely dissolve NTO and the crystal form control agent, and the temperature is slowly lowered. NTO is precipitated during the cooling process and is a white crystal, while the crystal form control agent has a large solubility in the solvent and remains during the cooling process. in solvent. After filtration, washing and drying, colorless and transparent γ-NTO crystals were obtained.

3. the preparation method of a kind of new crystal form NTO elemental explosive as claimed in claim 2, is characterized in that: the solvent of the solution described in step 1 is anhydrous methanol; Described crystal form control agent is 5-amino-1, 2,4-triazol-3-one or 4,4'-azo-1,2,4-triazolone.

4. the preparation method of a kind of new crystal form NTO elemental explosive as claimed in claim 2, is characterized in that: the described heating temperature of step 2 is to be heated to 60 ℃; The described cooling rate of step 2 is 1-5 ℃/min , cooled to 20 ℃.

5. the application of new crystal form NTO explosive as claimed in claim 1, is characterized in that: can be applied in the mixed explosive of press-packing, melting casting and pouring three kinds of charge forms, and can be applied in breaking armor, killing explosion and invading. Thorough and other warheads, and do not need to add anti-corrosion paint to the inner layer of the warhead shell.