CN110885280A

CN110885280A - Composite solid propellant based on nitramine oxidant coated aluminum powder and preparation method thereof

Info

Publication number: CN110885280A
Application number: CN201911231169.7A
Authority: CN
Inventors: 严启龙; 吕杰尧; 齐晓飞; 何伟; 刘佩进; 何国强
Original assignee: Northwestern Polytechnical University
Current assignee: Northwestern Polytechnical University
Priority date: 2019-12-05
Filing date: 2019-12-05
Publication date: 2020-03-17
Anticipated expiration: 2039-12-05
Also published as: CN110885280B

Abstract

The invention relates to a composite solid propellant based on aluminum powder coated by a nitramine oxidant and a preparation method thereof. The composite microspheres with the metal aluminum powder and the nitramine oxidant in the interfacial interaction are adopted, so that the oxidant in the propellant can be in close contact with the aluminum powder, the aluminum powder and the oxidant can quickly react when the propellant is combusted, and the adverse effects of the diffusion of the decomposition product of the oxidant and the agglomeration process of the aluminum powder on the combustion of the propellant can be inhibited. The preparation is simple and convenient, and the spray granulation process is adopted, so that the industrial production is easy to realize; the preparation method of the composite solid propellant based on the nitramine oxidant coated aluminum powder is simple, and the content of each component in the formula can be accurately controlled.

Description

Composite solid propellant based on nitramine oxidant coated aluminum powder and preparation method thereof

Technical Field

The invention belongs to the technical field of composite solid propellant preparation, and relates to a composite solid propellant based on nitramine oxidizer coated aluminum powder and a preparation method thereof.

Background

The composite solid propellant is a composite energetic material capable of rapidly releasing energy and generating thrust through combustion, and generally consists of a binder system, a metal fuel, an oxidant, a catalyst and a process auxiliary agent. The regulation of the combustion performance of the composite propellant is a necessary way for realizing the engineering application of the composite propellant, and generally, a catalyst is adopted to improve the combustion speed of the composite propellant, reduce the pressure index of the composite propellant and improve the combustion efficiency (strictly kindling. shallow talk about the judgment standard of the solid propellant combustion catalyst [ J)]The energetic material, 2019,27(4): 266-. The traditional catalyst comprises ammonium salt and organic amine, transition metal oxide, transition metal fluoride, ferrocene and derivatives thereof, copper salt and chelates thereof, and the like. 0.5 wt% of Fe is added into PGN/AND composite propellant₂O₃Can reduce the pressure index by 18% (the combustion performance of the PGN/ADN propellant [ J ] of Shang Dong Qin, Huang Hong Yong)]Energetic material, 2010,18(04): 372-; addition of 9 wt.% ferrocene to the ammonium perchlorate complex propellant reduces the propellant pressure index to around zero (Sinditski V P, Chernyi A N, Marchenkov D. Mechanism of combustion catalysis by proton driver. 2. Comustion of ammonium perchlorate-based propellants with proton driver. J].Combustion,Explosion,and Shock Waves,2014,50(2):158-167.)。

Although these catalysts can control the combustion performance of the composite solid propellant, the effect is limited, and the excessive addition of the above inert components can significantly reduce the energy level of the propellant (Zhao Feng Ji, Yijianhua, Anting, etc., solid propellant combustion catalyst [ M ]. Beijing: national defense industry Press, 2016.). Nano-catalysts have high catalytic efficiency due to large specific surface area and many active sites, but the addition of nano-components presents a huge challenge to the composite propellant preparation process (Isert S, Groven L J, Lucht R P, et al. the effect of encapsulated nanosized catalysts on the composite fuels of composite solid catalysts [ J ]. Combustion and Flame 2015,162(5):1821 and 1828.). Furthermore, the addition of catalysts incompatible with the main components of the propellant accelerates the ageing of the propellant, destroying its mechanical properties and structural integrity.

Aluminum powder is widely used in composite solid propellant as common metal fuel. The addition of aluminum powder can effectively improve the energy density of the propellant and inhibit the unstable combustion of the engine (Xiaolong, Hezhong Qiang, Liu pei, etc.. analysis of influence factors of the unstable combustion of the solid rocket engine and the latest research progress [ J ] the solid rocket technology, 2009,32(6): 600-. However, some of the aluminum powder will agglomerate at the propellant combustion surface and form large-sized agglomerates, which will cause two-phase flow loss to the engine, reduce the combustion efficiency of the propellant, and aggravate erosion and ablation of the thermal insulation layer (Aowen, Liupei, Luxiang, etc. progress on aluminum agglomeration research in the solid propellant combustion process [ J ] astronavigation, 2016,37(4): 371-. Therefore, the method has great research significance and engineering application value for exploring a technical way capable of realizing efficient regulation of the combustion performance of the composite propellant and inhibition of the agglomeration process of the aluminum powder.

Disclosure of Invention

Technical problem to be solved

In order to avoid the defects of the prior art, the invention provides a composite solid propellant based on nitramine oxidant coated aluminum powder and a preparation method thereof, which are used for improving the burning speed of the propellant, reducing the pressure index and inhibiting the agglomeration of the aluminum powder in the burning process.

Technical scheme

A composite solid propellant based on aluminum powder coated by a nitramine oxidant is characterized by comprising hydroxyl-terminated polybutadiene serving as a binder, aluminum powder serving as a metal fuel and a nitramine oxidant; the structure is that the nitramine oxidant coats the aluminum powder to form compact core-shell microspheres; the components are calculated by the mass percentage, and the total mass of the composite solid propellant is 100 wt%: 10-20 wt% of binder, 60-70 wt% of nitramine oxidant, 15-20 wt% of aluminum powder, 0.5-4 wt% of plasticizer, 0.5-2 wt% of curing agent, 0.5-2 wt% of other process aids and catalyst.

The nitramine oxidant is the mixture of ammonium perchlorate and ammonium nitrate in any proportion.

The aluminum powder is micron aluminum powder, nano aluminum powder or any combination of aluminum powder with various particle sizes, and the particle size range of the aluminum powder is 0.030-300 mu m.

The nitramine oxidant is one or more of hexogen, HMX and hexanitrohexaazaisowurtzitane.

The plasticizer is one or more of dioctyl sebacate, dioctyl adipate, isodecyl pelargonate, dibutyl phthalate and dioctyl phthalate.

The curing agent is one or more of isophorone diisocyanate and toluene diisocyanate.

A preparation method of the composite solid propellant based on the nitramine oxidizer-coated aluminum powder is characterized by comprising the following steps:

step 1: drying all solid materials in an oven at the drying temperature of 50-80 ℃ for 96-120 h;

step 2: preparing a nitramine oxidant by a spray drying method to coat aluminum powder to form a compact core-shell microsphere, wherein polydopamine is used as an interface layer material to play a role in adhesion, or polydopamine is not used; in the microspheres formed by coating the aluminum powder with the nitramine oxidant, the mass ratio of the aluminum powder to the nitramine oxidant is 1:0 and 05-10;

and step 3: coating aluminum powder with a nitramine oxidant to form compact core-shell microspheres and other components, and fully stirring the core-shell microspheres and the other components in a water bath at 40-50 ℃ to prepare composite propellant slurry;

and 4, step 4: vacuum casting the propellant slurry into a mold or an engine shell for 1-2 h;

and 5: and curing the mold or the engine filled with the propellant slurry at 50-60 ℃ for 24-168 hours.

Advantageous effects

The invention provides a composite solid propellant based on aluminum powder coated by a nitramine oxidant and a preparation method thereof. The oxidizer and the metal fuel in the traditional composite propellant are directly dispersed and processed without further treatment, and the oxidizer and the metal fuel are not in interfacial contact in a binder system. Therefore, the metal fuel enters the gas phase zone and then is mixed with the oxidizer and the decomposition products thereof in a diffusion mode and starts to react, and part of the metal fuel is agglomerated on the combustion surface of the propellant, so that the combustion efficiency of the propellant is reduced and the performance of an engine is affected.

The composite microspheres with the metal aluminum powder and the nitramine oxidant in the interfacial interaction are adopted, so that the oxidant in the propellant can be in close contact with the aluminum powder, the aluminum powder and the oxidant can quickly react when the propellant is combusted, and the adverse effects of the diffusion of the decomposition product of the oxidant and the agglomeration process of the aluminum powder on the combustion of the propellant can be inhibited. Compared with the traditional composite solid propellant, the introduction of the interface interaction can obviously improve the burning rate of the propellant under low pressure, reduce the pressure index of the propellant, and play roles in catalyzing combustion and adjusting the burning rate without adding any catalyst; by the method, the content of the combustion catalyst in the formula can be reduced, and the overall energy level of the propellant is improved. In addition, the composite microspheres with the structure replace metal fuel and oxidant particles in the traditional composite propellant, so that the agglomeration of aluminum powder in the combustion process can be inhibited, and the combustion efficiency of the propellant is improved.

The preparation of the nitramine oxidant-coated aluminum powder is simple and convenient, and the spray granulation process is adopted, so that the industrial production is easy to realize; the preparation method of the composite solid propellant based on the nitramine oxidant coated aluminum powder is simple, and the content of each component in the formula can be accurately controlled.

Drawings

FIG. 1 is SEM and TEM images of aluminum powder microspheres coated with nitramine oxidizer used in propellant formulation;

FIG. 2 is a graph showing the particle size distribution of aluminum powder microspheres coated with nitramine oxidizer used in propellant formulations of examples 3-6 of the present invention;

FIG. 3 is a SEM image of the cross-section of the propellant of examples 1-6 of the present invention;

FIG. 4 is an SEM image of propellant condensed phase combustion products of examples 1, 4 and 5 of the present invention;

figure 5 is a particle size distribution of the propellant condensed phase combustion products of examples 1-6 of the present invention.

Detailed Description

The invention will now be further described with reference to the following examples and drawings:

the preparation process of the examples can be divided into the following three steps:

(1) preparing polydopamine surface modified aluminum powder: adding 0.36g of dopamine and 0.2g of TRIS buffer solution (PH 8.5) into 200ml of distilled water, stirring for 10min to enable dopamine molecules to be partially polymerized, adding 3.6g of mu-Al (1-2 mu m) and stirring for 1h to enable polydopamine to grow in situ on the surface of aluminum powder to form a polydopamine layer, and drying the solution to obtain the aluminum powder mu-Al @ PDA with the surface uniformly coated with the polydopamine; it should be noted that the content of PDA in μ -Al @ PDA is less than 0.5 wt%, so the mass is negligible for the entire propellant formulation, and it can be considered that the mass ratio of Al to RDX in the microspheres is 1: 1;

(2) preparing the nitramine oxidant-coated aluminum powder microspheres: dissolving 5.0g of RDX in 25ml of dimethyl sulfoxide (DMSO) solution, adding Al @ PDA with the same mass, and stirring for 1h to uniformly disperse the RDX in the RDX solution to obtain a spray-dried precursor solution; volatilizing DMSO in the precursor suspension by adopting a spray drying device (the air inlet temperature is between 160 ℃) to prepare Al @ PDA @ RDX microspheres with core-shell structures;

FIG. 1 is a SEM image of Al @ PDA @ RDX, and FIG. 2 is a particle size of Al @ PDA @ RDXAnd (4) distribution. The microspheres prepared by coating the aluminum powder with the nitramine oxidant have complete structures, and a single microsphere contains a plurality of Al particles; d of mu-Al and n-Al in the raw material₅₀D of μ -Al @ PDA @ RDX and n-Al @ PDA @ RDX, prepared by spray drying, 0.075 μm and 1.195 μm, respectively₅₀7.8 μm and 11.5 μm, respectively;

(3) preparation of the composite solid propellant: example 1 was obtained using a conventional composite solid propellant manufacturing process and examples 2-6 were obtained using a different type of Al @ PDA @ RDX instead of some or all of the Al and RDX in the formulation of example 1.

Example 1: a composite solid propellant contains no combustion rate catalyst. Wherein the binder adopts hydroxyl-terminated polybutadiene (HTPB), and the content is 12 wt%; the plasticizer is diisooctyl sebacate (DOS), and the content is 2 wt%; the curing agent adopts isophorone diisocyanate (IPDI), and the content is 1 wt%; the content of mu-Al is 18 wt%; RDX content 18 wt%; the Ammonium Perchlorate (AP) content is 49 wt%; the theoretical specific impulse of the formula is 2567 m.s^-1. The preparation method of the specific propellant comprises the following steps:

1) raw material treatment: drying the solid material in an oven at 60 ℃ for 96-120 h;

2) weighing and mixing: weighing 100g of each component according to the formula, and stirring for 120min under the water bath condition of 40-50 ℃ to prepare composite propellant slurry;

3) vacuum pouring: pouring the propellant slurry into a customized mould in vacuum, wherein the vacuum pouring time is not less than 2 h;

4) curing the pharmaceutical strip: heating and curing the propellant slurry at 70-80 ℃ for not less than 120h, demolding after complete curing, and processing the propellant into 5 x 25mm medicinal strips.

From FIG. 3 it can be seen that the AP, RDX and μ -Al particles in example 1 are randomly distributed in the binder system with no interfacial contact between the particles; example 1 has an apparent density of 1.70g cm^-3The heat of reaction was 5.34kJ · g^-1The energy density is 9.08kJ · cm^-3(Table 2); example 1 the propellant has a pressure index of 0.156 (table 3) in the range of 1-4 MPa; from FIG. 4, it can be seen that the condensed phase combustion product disorder of example 1Disorder and a large amount of sintering agglomeration exist; it can be seen from fig. 5 that the condensed phase combustion product particle size distribution of example 1 exhibits a trimodal distribution similar to that of other aluminum-containing composite propellants, with the rightmost peak representing the largest particle size agglomerate with an agglomerate size of 79.6 μm, 67 times the original μ -Al particle size.

Example 2: the rest is the same as the example 1, all the mu-Al is replaced by the same mass of dopamine surface modified aluminum powder mu-Al @ PDA;

it can be seen from FIG. 3 that the AP, RDX and μ -Al @ PDA particles of example 2 are also randomly distributed in the binder system and there is no interfacial contact between the components; example 2 has an apparent density of 1.69g cm^-3The heat of reaction was 5.42kJ · g^-1The energy density is 9.15kJ · cm^-3(Table 2). Example 2 has a pressure index of 0.236, a 51% increase compared to example 1 (table 3); it can be seen from FIG. 5 that the particle size distribution of the condensed phase combustion products also exhibits a trimodal distribution, with the maximum size of the agglomerates being 70.9 μm in size.

Example 3: otherwise as in example 1, 50 wt% of the μ -Al and RDX were replaced with μ -Al @ PDA @ RDX;

from FIG. 3, it can be seen that the four components of AP, RDX, μ -Al and μ -Al @ PDA @ RDX are present simultaneously in example 3; example 3 has an apparent density of 1.71g cm^-3The heat of reaction was 5.28 kJ.g^-1The energy density is 9.01kJ · cm^-3(Table 2). Example 3 has a pressure index of 0.096, which is significantly lower than example 1 (table 3); it can be seen from fig. 5 that the large-size agglomeration of the condensed phase combustion products is significantly reduced, indicating that the aluminum agglomeration phenomenon is suppressed during the propellant combustion.

Example 4: otherwise as in example 1, all μ -Al and RDX were replaced with μ -Al @ PDA @ RDX;

from FIG. 3 it can be seen that only two particles, AP and μ -Al @ PDA @ RDX, are present in example 4; example 4 has an apparent density of 1.67g cm^-3The heat of reaction was 4.93kJ · g^-1The energy density is 8.24kJ · cm^-3(Table 2). Example 4 has a pressure index of only 0.024, only 15% of example 1 (table 3); it can be seen from FIG. 4 that the condensed phase combustion products of example 4 are comparable to those of the condensed phase combustion productsOrdered, without significant sintered agglomerates; it can be seen from fig. 5 that the large-size agglomerates in the condensed phase combustion products completely disappeared, indicating that the aluminum agglomeration phenomenon was completely suppressed during the propellant combustion.

Example 5: otherwise as in example 1, all μ -Al and RDX were replaced with n-Al @ PDA @ RDX;

from FIG. 3 it can be seen that only two types of particles, AP and n-Al @ PDA @ RDX, are present in example 5; example 5 has an apparent density of 1.62g cm^-3The heat of reaction was 5.04 kJ.g^-1The energy density is 8.15kJ · cm^-3(Table 2); it can be seen that the condensed phase combustion product of example 5 is very ordered, completely free of sintered agglomerates; from fig. 5, it can be seen that the large-size agglomeration of the condensed phase combustion product completely disappeared, indicating that the aluminum agglomeration phenomenon is significantly suppressed during the propellant combustion process.

Example 6: otherwise as in example 1, 50 wt% of the μ -Al and RDX were replaced with n-Al @ PDA @ RDX;

from FIG. 3, it can be seen that the four components of AP, RDX, μ -Al and n-Al @ PDA @ RDX are present simultaneously in example 6; example 6 has an apparent density of 1.68g cm^-3The heat of reaction was 5.01 kJ.g^-1The energy density is 8.40kJ · cm^-3(Table 2); it can be seen from fig. 5 that the large-size agglomeration of the condensed phase combustion products is significantly reduced, indicating that the aluminum agglomeration phenomenon is suppressed during the propellant combustion.

TABLE 1 propellant formulations of examples 1-6 and their theoretical specific impact

Note: RDX content in Al @ PDA @ RDX is 50 wt%; the theoretical specific impulse is calculated by thermodynamic calculation software (CEA) according to the aerospace industry standard QJ 1953-90.

TABLE 2 Density, Heat of reaction and energy Density for examples 1-6

TABLE 3 burning rate and pressure index at 1-4MPa for examples 1-4, where p is pressure

Claims

1. A composite solid propellant based on aluminum powder coated by a nitramine oxidant is characterized by comprising hydroxyl-terminated polybutadiene serving as a binder, aluminum powder serving as a metal fuel and a nitramine oxidant; the structure is that the nitramine oxidant coats the aluminum powder to form compact core-shell microspheres; the components are calculated by the mass percentage, and the total mass of the composite solid propellant is 100 wt%: 10-20 wt% of binder, 60-70 wt% of nitramine oxidant, 15-20 wt% of aluminum powder, 0.5-4 wt% of plasticizer, 0.5-2 wt% of curing agent, 0.5-2 wt% of other process aids and catalyst.

2. The composite solid propellant based on nitramine oxidizer-coated aluminum powder as claimed in claim 1, is characterized in that: the nitramine oxidant is the mixture of ammonium perchlorate and ammonium nitrate in any proportion.

3. The composite solid propellant based on nitramine oxidizer-coated aluminum powder as claimed in claim 1, is characterized in that: the aluminum powder is micron aluminum powder, nano aluminum powder or any combination of aluminum powder with various particle sizes, and the particle size range of the aluminum powder is 0.030-300 mu m.

4. The composite solid propellant based on nitramine oxidizer-coated aluminum powder as claimed in claim 1, is characterized in that: the nitramine oxidant is one or more of hexogen, HMX and hexanitrohexaazaisowurtzitane.

5. The composite solid propellant based on nitramine oxidizer-coated aluminum powder as claimed in claim 1, is characterized in that: the plasticizer is one or more of dioctyl sebacate, dioctyl adipate, isodecyl pelargonate, dibutyl phthalate and dioctyl phthalate.

6. The composite solid propellant based on nitramine oxidizer-coated aluminum powder as claimed in claim 1, is characterized in that: the curing agent is one or more of isophorone diisocyanate and toluene diisocyanate.

7. A preparation method of the composite solid propellant based on nitramine oxidizer-coated aluminum powder, which is disclosed by any one of claims 1-6, is characterized by comprising the following steps: