Silver azide in-situ charging method based on ink-jet printing

Abstract

The invention discloses a silver azide in-situ charging method based on ink-jet printing, and belongs to the technical field of energetic material charging. According to the ink-jet printing method, sodium azide printing ink and a silver salt solution are prepared respectively, the surface tension and viscosity of the sodium azide printing ink are adjusted through a binder and a surfactant, the surface tension and viscosity of the silver salt printing ink are adjusted through the mass ratio of ethylene glycol to water, sodium azide and silver salt are printed in sequence, and silver azide is obtained through an in-situ reaction. According to the method, the initiating explosive can be printed on the medium in situ, complete hand-free operation is achieved in the charging process, and danger in the manual silver azide charging process is avoided.

Description

Technical Field

[0001] The invention relates to an in-situ charging method of silver azide, belonging to the technical field of energetic material charging. Background Art

[0002] Heavy metal azides occupy an important position in explosives. At present, lead azide is still a commonly used explosive in engineering, but its low detonation ability and great environmental hazards make it difficult to meet the current needs of micro-initiation systems. Copper azide has strong initiation ability and can be detonated at the sub-milligram level, but it has high electrostatic sensitivity and is complicated to operate when micro-charging. With the development of micro-electromechanical system (MEMS) technology, the requirements for energetic materials are higher. Traditional explosives such as lead azide cannot meet the energy output requirements. It is even more challenging to combine energetic materials with micro-pyrotechnic devices. The emergence of in-situ reaction synthesis method solves the problem of charging high-sensitivity agents. Through the in-situ method, not only can the potential danger of the explosive charge be reduced, but also the interface reaction between the explosive and the matrix can be enhanced, making its mechanical properties better than the non-in-situ method.

[0003] At present, a variety of methods have been realized to achieve in-situ synthesis of copper azide / silver azide, such as gas-solid in-situ method, electrochemical method, electrospinning method, direct writing technology and other processes. Li Mingyu et al. used the gas-solid azide method of silver azide / copper azide through experimental research, and the product has good detonation. However, the reaction conditions of the gas-solid method are harsh, the reaction time is long, and the utilization of hydrazine is not only low, but also there is a risk of environmental pollution; Yu Chunpei et al. developed a new method for in-situ preparation of new CuN3 explosive films on copper substrates using electrochemical azide. The electrochemical method makes CA deposited on carbon nanotubes and the like to better solve the electrostatic sensitivity problem of CA, but due to insufficient porosity, byproducts such as copper oxide and cuprous azide will be produced. The use of electrospinning technology and direct writing technology is only different in the preparation method of the precursor, but the in-situ azide method has not escaped the original method, and the same problems that occur in the gas-solid method and electrochemical method exist. Therefore, it is necessary to find a better new strategy for MEMS.

[0004] At present, inkjet printing has been proven to be beneficial for the small-scale deposition of functional inks, making up for the defect of the current process that cannot be controlled in sub-millimeter space. Domestic and foreign scholars have preliminarily explored the research on micro-charging of energetic materials and micro-manufacturing of energetic devices at the high precision, complex pattern, and micro-nano level. The vigorous development of inkjet printing technology research has provided an effective way for the manufacture of MEMS pyrotechnics. However, due to the high sensitivity of the detonator, there is no report on the successful in-situ charging of the detonator using the inkjet printing method. Summary of the invention

[0005] 1. Problem to be solved

[0006] In view of the problem that direct charging cannot be adopted due to the sensitivity of silver azide, the present invention provides an in-situ charging method of silver azide based on inkjet printing. Through the formulation design of ink, highly sensitive silver azide is successfully prepared by inkjet printing, thereby realizing a safe in-situ charging method of silver azide detonator.

[0007] 2. Technical solution

[0008] In order to solve the above problems, the technical solution adopted by the present invention is as follows:

[0009] The first aspect of the present invention provides a method for in-situ charging of silver azide based on inkjet printing, comprising the following steps:

[0010] S1 ink configuration:

[0011] A sodium azide ink is prepared, wherein the sodium azide ink comprises sodium azide, water, polyvinyl pyrrolidone, sodium dodecylbenzene sulfonate and ethylene glycol, and the surface tension of the sodium azide ink is controlled to be 36.0-45.0 mN / m, and the viscosity is controlled to be 4.0-8.0 cps; the content of sodium azide in the sodium azide ink is 0.1-0.3 g / mL; in the sodium azide ink, water is a solvent, polyvinyl pyrrolidone is a binder, sodium dodecylbenzene sulfonate is a surfactant, and ethylene glycol is used to increase the viscosity;

[0012] Prepare a silver salt ink, wherein the silver salt ink contains silver salt, water and ethylene glycol, and the surface tension of the silver salt ink is controlled to be 40.0-46.0 mN / m, and the viscosity is controlled to be 9.0-12.0 cPs; the content of silver salt in the silver salt ink is 0.1-1.0 g / ml;

[0013] S2 inkjet printing: firstly, on the printing medium, a plurality of sodium azide layers are printed with sodium azide ink, and then silver salt ink is used to print silver salt on the sodium azide layer;

[0014] S3: drying the product obtained in step S2 in a vacuum oven.

[0015] As a preference in the first aspect of the present invention, the silver salt comprises silver nitrate or silver perchlorate.

[0016] As a preferred embodiment of any technical solution of the first aspect of the present invention, the mass percentage of polyvinyl pyrrolidone in the sodium azide ink is 2.0% to 6.0%; the mass percentage of sodium dodecylbenzene sulfonate is 0.1% to 0.3%; and the mass percentage of ethylene glycol is 25.0% to 35.0%.

[0017] As a preferred embodiment of any technical solution of the first aspect of the present invention, the silver salt is silver nitrate, and the mass ratio of ethylene glycol to water in the silver nitrate ink is (2.2-3):1.

[0018] As a preferred embodiment of any technical solution of the first aspect of the present invention, the silver salt is silver nitrate, and the surface tension of the sodium azide ink is controlled to be 38.0-42.0 mN / m and the viscosity is 6.0-8.0 cPs; the surface tension of the silver nitrate ink is controlled to be 40.0-45.0 mN / m and the viscosity is 9.0-10.0 cPs.

[0019] As a preferred embodiment of any technical solution of the first aspect of the present invention, the silver salt is silver nitrate, and when the printing areas are the same, the number of sodium azide printing layers and the number of silver nitrate printing layers in step S2 are controlled so that the molar number of printed sodium azide is equal to the molar number of silver nitrate.

[0020] As a preferred embodiment of any technical solution of the first aspect of the present invention, step S3 includes placing the printed device containing silver azide in a vacuum oven and drying it at 60° C. for 6 to 12 hours to ensure that the solvent is fully volatilized.

[0021] As a preferred embodiment of the first aspect of the present invention, during inkjet printing in step S2, the volume of a single ink drop is 10 pL.

[0022] As a preferred embodiment of any technical solution of the first aspect of the present invention, during inkjet printing in step S2, the printing medium is a semiconductor bridge. The printing medium is not particularly limited and may also be other planar structured explosives.

[0023] As a preferred embodiment of any technical solution of the first aspect of the present invention, Fujifilm Dimatix material printer DMP-2850 is used for inkjet printing. Fujifilm Dimatix material printer DMP-2850 is a DOD piezoelectric driven inkjet printer with the functions of adjusting the print head temperature, platen temperature, emission voltage, print height, ink drop spacing and multiple repeated printing.

[0024] Furthermore, the printing nozzle diameter of the Fujifilm Dimatix material printer DMP-2850 is 21 μm.

[0025] Further, the Fujifilm Dimatix material printer DMP-2850 has 16 nozzles. These nozzles are driven by the piezoelectric element of the Dimatix printer, which is much smaller than the inkjet printers developed by most laboratories (for example, the diameter is usually 60-90 μm). As a preferred embodiment of any technical solution of the first aspect of the present invention, the printer jet voltage is 15-16.5V, the jet frequency is 5KHZ, and the inkjet spacing is 15-20 μm.

[0026] The second aspect of the present invention provides an explosive prepared by the method of any technical solution of the first aspect of the present invention.

[0027] The third aspect of the present invention provides an energetic explosive device comprising the explosive according to the second aspect of the present invention.

[0028] 3. Beneficial effects

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) The inkjet printing method of the present invention is used to print the detonating charge in situ on the medium, and the charging process is completely hands-free, thereby avoiding the danger of manually charging silver azide. Specifically, a binder and a surfactant are used to adjust the surface tension and viscosity of the sodium azide ink, and the mass ratio of ethylene glycol and water is used to adjust the surface tension and viscosity of the silver salt ink. Sodium azide and silver salt are printed in sequence, and silver azide is obtained by in-situ reaction.

[0031] (2) In the method of the present invention, the surface tension of the sodium azide ink is controlled to be 38.0-42.0 mN / m, and the viscosity is 6.0-8.0 cPs; the surface tension of the silver nitrate ink is controlled to be 40.0-45.0 mN / m, and the viscosity is 9.0-10.0 cPs. The sodium azide ink and the silver salt ink can be stored at a low temperature of 2-6°C for one month without deterioration. The ink has good stability and is not affected by use at room temperature;

[0032] (3) The present invention adopts Fujifilm Dimatix material printer DMP-2850 inkjet printing, and the amount of each drop is controlled at the pL level. The amount of droplets can be controlled according to the size of the pattern, and then the amount of synthesized silver azide can be controlled; the shape and size of the explosive in the method of the present invention can be controlled, especially the characteristic size of the explosive can be controlled below 1 mm, and the thickness of the explosive can be adjusted according to the number of printing layers, which increases the flexibility of the explosive charging while ensuring safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 These are the waveform parameters used in Example 1 of the present invention.

[0034] Figure 2 This is the product obtained by printing (before drying) in Example 1 of the present invention (left: on a glass substrate; right: on the surface of the ignition bridge).

[0035] Figure 3 This is a SEM image of the in-situ printed silver azide in Example 1 of the present invention.

[0036] Figure 4 This is the XRD pattern of silver azide printed in situ in Example 1.

[0037] Figure 5 This is the FT-IR image of the silver azide printed in situ in Example 1.

[0038] Figure 6 This is a high-speed photograph of about 100 μg of silver azide printed in situ in Example 1.

[0039] Figure 7 This is the SEM image of silver azide generated by the silver perchlorate ink in Example 6.

[0040] Figure 8 This is the ignition current-voltage curve and power diagram in Example 6. DETAILED DESCRIPTION

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention belongs; the term "and / or" used herein includes any and all combinations of one or more of the associated listed items.

[0042] If the specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or conditions recommended by the manufacturer. If the manufacturers of the reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0043] Concentration, amount and other numerical data can be presented in range format herein.It should be understood that such range format is only used for convenience and simplicity, and should be flexibly interpreted as not only including the numerical value clearly described as range limit, but also including all single numerical values ​​or sub-ranges contained in the range, just as each numerical value and sub-range are clearly described.For example, the numerical range of about 1 to about 4.5 should be interpreted as not only including the limit value of 1 to about 4.5 clearly described, but also including single numerals (such as 2,3,4) and sub-ranges (such as 1 to 3,2 to 4, etc.).The same principle is applicable to the scope of only narrating a numerical value, such as "less than about 4.5", which should be interpreted as including all the above-mentioned values ​​and ranges.In addition, no matter how the breadth of the described range or feature is, this explanation should be applicable.

[0044] Surface tension test was performed using micro-controlled fully automatic interfacial tension meter JYW-200B (at room temperature).

[0045] Viscosity test instrument and conditions: Viscosity test using: digital viscometer NDJ-9S; at room temperature, using rotor No. 0 for measurement.

[0046] The present invention is further described below in conjunction with specific embodiments.

[0047] Example 1

[0048] Step 1: Prepare sodium azide ink: add 1g PVP (polyvinyl pyrrolidone) and 0.06g SDBS (sodium dodecylbenzene sulfonate) to 20ml of deionized water, and after mixing evenly, add 0.5ml ethylene glycol and 0.6g sodium azide to 1ml of the solution to prepare 0.2g / ml sodium azide ink; the surface tension is 40mN / m and the viscosity is 6cPs;

[0049] Step 2: Silver nitrate ink (ink): add 20 ml of ethylene glycol to 10 ml of deionized water, mix evenly by ultrasonication, then add 1 ml of solvent to 1 g of silver nitrate to prepare silver nitrate ink; the surface tension is 44 mN / m and the viscosity is 9 cPs;

[0050] Step 3: Load sodium azide ink into DMP-2850 and set the printing parameters: voltage 16.5V, frequency 5KHz, nozzle temperature 30℃, ink drop spacing 20μm, and set the piezoelectric waveform as follows: Figure 1 Voltage rise / fall within 1 μs, pulse duration ~6.4 μs, 100% printing potential.

[0051] Table 1 Printing parameters

[0052]

[0053] Step 4: Printing (printing media are medium slides and ignition bridges respectively); printing area 0.6mm×0.6 / 0.8mm, 20 layers, then replace the silver nitrate ink cartridge (note that the ink droplet collector should also be replaced at the same time) and print 11 layers to form an equimolar reaction, print on the medium slide or ignition bridge, where the product printed on the slide is used to observe the in situ reaction (such as Figure 2 ), products printed on the ignition bridge are used for testing in ignition experiments.

[0054] Step 5: Place the in-situ printed semiconductor bridge containing AgN3 in a vacuum oven and dry it at 60°C for 12 hours to obtain the finished product. Figure 3 ,From the SEM images, the small particles generated in the semiconductor bridge containing AgN3 in the ,printed product are different from the rod-shaped crystals of sodium azide, and it is believed that sodium azide has ,been converted into silver azide products.

[0055] like Figure 4 ,From the XRD results, the XRD spectrum of AgN3 in the finished ,printed product is close to the silver azide standard card, indicating that silver azide ,product is generated.

[0056] like Figure 5 , from the FT-IR results, the peak position is at 1950cm -1 The position is the azide root peak of silver azide, which also verifies the formation of silver azide.

[0057] Figure 6 This is a 4,000,000-frame high-speed photography capture of about 100 μg of reactive ink deposited directly on the semiconductor. It can be seen that after the in-situ printed semiconductor bridge is excited, a bright flame is generated and AgN3 is successfully ignited. In comparison, the in-situ printed AgN3 semiconductor bridge brings a longer flame and a higher flame height.

[0058] Example 2

[0059] In two experiments, 0.5g and 1.5g of PVP were added to 20ml of deionized water to prepare sodium azide ink. The experiment found that the change of PVP concentration had little effect on surface tension, and mainly affected viscosity. The viscosity of sodium azide ink in the two experiments was 4.23cPs and 7.10cPs respectively. The other conditions were the same as in Example 1, and the finished silver azide product was successfully printed.

[0060] Example 3

[0061] The mass ratio of solvent component ethylene glycol: deionized water is from 20:10 to 25:5, and silver nitrate ink is prepared. After adding silver nitrate, the surface tension is slightly reduced, and the viscosity is increased from 9cPs to 11cPs. When the other conditions are the same as in Example 1, printing can also be performed, and the silver azide product is successfully printed.

[0062] Example 6

[0063] An example of a successful product obtained by inkjet printing using AgClO4 as ink.

[0064] Silver nitrate was replaced with silver perchlorate, and silver azide products were also successfully printed. 1g / ml silver perchlorate ink was prepared, and the other components were the same as those of the silver nitrate ink in Example 1, and the sodium azide ink was the same as that in Example 1. The same printing method was used to successfully print the product. SEM showed Figure 7 The ignition sensitivity was tested, and the results are shown in Table 1. However, due to the strong hygroscopicity of perchloric acid, the product must be stored in a dry and sealed environment.

[0065] 1. Ignition sensitivity test

[0066] The ignition sensitivity of electric ignition products is tested according to GJB 5309.9-2004. The D-optimization test method is used. The ignition power supply voltage resolution is 0.1V, the lower limit of stimulation is 10V, the upper limit of stimulation is 20V, and the standard deviation estimate is σ guess The firing capacitance is 47 μF. The silver azide printed by the sodium azide ink and the silver perchlorate ink in this embodiment is used to obtain the 50% firing voltage of the semiconductor bridge. The experimental results are shown in Table 1.

[0067] Table 1 Product ignition sensitivity test results

[0068]

[0069] From the results, the 50% firing voltage of the in-situ printed semiconductor bridge is 12.99V, with a standard deviation of 0.3V.

[0070] 2. Current-voltage curve and power of ignition

[0071] The current-voltage curve obtained at 15V is as follows Figure 8 As shown in A, according to the power ( Figure 8 B) The energy required for the bridge is calculated to be 0.51 mJ and the integration time is 8.1 μs.

[0072] Comparative Example 1

[0073] The sodium azide ink obtained by using polyvinyl alcohol (87% alcoholysis degree) with a mass fraction of 1-3% to replace polyvinyl pyrrolidone, and the other components are the same as those in Example 1, has the problem of not spraying ink in the middle of printing, a layer of film adheres to the nozzle surface, and the nozzle is blocked. The reason may be that polyvinyl alcohol is more likely to adhere to the inkjet channel, causing nozzle damage, and it cannot be restored after soaking in warm water / ethanol aqueous solution. Therefore, it is concluded that although polyvinyl alcohol has good film-forming properties as a binder, and a small amount can cause a large change in surface tension and viscosity, for the inkjet printing of the present invention, polyvinyl alcohol (87% alcoholysis degree) is not suitable as a binder in sodium azide ink.

[0074] Comparative Example 2

[0075] Sodium dodecyl sulfate (SDS) was used as a surfactant instead of sodium dodecylbenzene sulfonate. The other conditions were the same as in Example 1. It was found that sodium azide produced precipitation after contact with sodium dodecyl sulfate, and it was impossible to prepare a full-liquid ink. Therefore, it was concluded that sodium dodecyl sulfate was not suitable as a surfactant in sodium azide ink.

[0076] Comparative Example 3

[0077] No surfactant was added to the sodium azide ink, and the other configurations were the same as those of the sodium azide ink in Example 1. The surface tension of the sodium azide ink was greater than 50 mN / m, and only a very small amount of sodium azide could be printed. The reason was that the surface tension was too large, and the applied voltage was insufficient to overcome the surface tension of the ink, so the ink could not break at the nozzle to form ink droplets, and thus could not be printed.

[0078] Comparative Example 4

[0079] When the solvent water in Example 1 is replaced with ethanol, the surface tension is less than 30 mN / m. At this time, the printing parameters cannot control the ink droplets, and the ink flows out continuously at the nozzle without forming droplets.

[0080] Comparative Example 5

[0081] Under the conditions of Example 1, when the printing voltage is lower than 15V, the ink cannot be ejected; when the printing voltage is higher than 16.5V, the ink droplets do not appear in the form of single ink droplets, but satellite droplets appear; in both cases, silver azide cannot be successfully printed.

[0082] The above content is a schematic description of the present invention and its implementation methods, which is not restrictive. What is shown in the embodiment is only one of the implementation methods of the present invention, and the actual implementation method is not limited thereto. Therefore, if a person of ordinary skill in the art is inspired by it and designs implementation methods and embodiments similar to the technical solution without creative design without departing from the purpose of the invention, they should all fall within the scope of protection of the present invention.

Claims

1. A method for in-situ charging of silver azide based on inkjet printing, characterized in that: The following steps are involved: S1 ink configuration: A sodium azide ink is prepared, wherein the sodium azide ink comprises sodium azide, water, polyvinyl pyrrolidone, sodium dodecylbenzene sulfonate and ethylene glycol, and the surface tension of the sodium azide ink is controlled to be 36.0 to 45.0 mN / m, and the viscosity is controlled to be 4.0 to 8.0 cps; and the content of sodium azide in the sodium azide ink is 0.1 to 0.3 g / mL; Prepare a silver salt ink, wherein the silver salt ink contains silver salt, water and ethylene glycol, and the surface tension of the silver salt ink is controlled to be 40.0-46.0 mN / m, and the viscosity is controlled to be 9.0-12.0 cPs; the content of silver salt in the silver salt ink is 0.1-1.0 g / ml; S2 inkjet printing: on the printing medium, firstly print a plurality of sodium azide layers with sodium azide ink, and then print silver salt on the sodium azide layer with silver salt ink; S3 vacuum dries the product obtained in step S2.

2. The method for in-situ charging of silver azide based on inkjet printing according to claim 1, characterized in that: The silver salt includes silver nitrate or silver perchlorate.

3. The silver azide in-situ charging method based on inkjet printing according to claim 1, characterized in that: The mass percentage of polyvinyl pyrrolidone in the sodium azide ink is 2.0% to 6.0%, the mass percentage of sodium dodecylbenzene sulfonate is 0.1% to 0.3%, and the mass percentage of ethylene glycol is 25.0% to 35.0%.

4. The silver azide in-situ charging method based on inkjet printing according to claim 2, characterized in that: The silver salt is silver nitrate, and the mass ratio of ethylene glycol to water in the silver nitrate ink is (2.2-3):

1.

5. The silver azide in-situ charging method based on inkjet printing according to claim 4, characterized in that: The surface tension of the sodium azide ink is controlled to be 38.0-42.0 mN / m, and the viscosity is controlled to be 6.0-8.0 cPs; the surface tension of the silver nitrate ink is controlled to be 40.0-45.0 mN / m, and the viscosity is controlled to be 9.0-10.0 cPs.

6. The method for in-situ charging of silver azide based on inkjet printing according to claim 5, characterized in that: When the printing areas are the same, the number of sodium azide printing layers and the number of silver nitrate printing layers in step S2 are controlled so that the molar number of printed sodium azide is equal to the molar number of printed silver nitrate.

7. The silver azide in-situ charging method based on inkjet printing according to claim 1, characterized in that: During inkjet printing in step S2, the volume of a single ink drop is 10 pL.

8. The silver azide in-situ charging method based on inkjet printing according to claim 1, characterized in that: Inkjet printing was performed using a Fujifilm Dimatix material printer DMP-2850.

9. The method for in-situ charging of silver azide based on inkjet printing according to claim 1, characterized in that: The printing nozzle diameter of the Fujifilm Dimatix material printer DMP-2850 is 21 μm.

10. An energetic explosive device prepared by the method as claimed in any one of claims 1 to 9.

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