摘要
为研究药型尺寸对单基发射药分子裁剪反应过程的影响,以水合肼为脱硝试剂,对七孔、单孔和无孔单基发射药进行表层分子裁剪,制备了3种梯度硝基单基发射药。基于Avrami模型对不同药型单基发射药分子裁剪反应过程的动力学进行了研究,结果表明:Avrami模型可以用于描述3种药型单基发射药的分子裁剪反应过程;七孔单基发射药的Avrami指数,在70~75 ℃范围内n>1,分子裁剪反应过程受化学反应过程控制;在75~80 ℃范围内n<1,分子裁剪反应过程受内扩散和化学反应共同控制。单孔和无孔单基发射药的Avrami指数n<1,分子裁剪反应过程受内扩散和化学反应共同控制。依据Fick定律求得单孔和无孔单基发射药的扩散系数D,单孔单基发射药的扩散系数为3.8×1
图文摘要
Based on the Avrami model, the kinetic process of molecular tailoring reaction of three different shapes of single‑base propellants (seven‑holes, one‑hole and non‑hole single‑base propellant) was studied.
提高发射药燃烧渐增性是改善身管武器弹道性能的方法之
梯度硝基单基发射药的制备过程是脱硝试剂与发射药之间的固液非均相反应过程,包括脱硝试剂在发射药颗粒中的扩散过程和脱硝试剂与发射药表层硝酸酯基的化学反应过程。单基发射药颗粒的药型尺寸会影响脱硝试剂与发射药颗粒之间的非均相反应过程。因此,研究不同药型尺寸单基发射药表层硝酸酯基分子裁剪反应过程动力学,对寻求找到较佳的生产工艺条件具有重要的意义。目前,研究固液非均相反应动力学过程的模型主要有收缩未反应芯模
由于收缩未反应芯模型适用于无孔圆柱形颗粒的固液非均相反应,对于单孔和多孔单基发射药来说收缩未反应芯模型不太适
试剂:七孔单基发射药、单孔单基发射药和无孔单基发射药为泸州北方化学工业有限公司提供,3种单基发射药的具体尺寸参数如
original material | web thickness / mm | d1 / mm | d2 / mm | h / mm | specific surface area / m |
---|---|---|---|---|---|
seven‑holes single‑base propellant | 0.6 | 1.596 | 0.135 | 4.145 | 0.166 |
one‑hole single‑base propellant | 1.1 | 1.276 | 0.176 | 3.897 | 0.115 |
non‑hole single‑base propellant | - | 0.761 | - | 2.077 | 0.224 |
Note: d1 is the radius of the propellants,mm. d2 is the radius of the hole,mm. h is the length of the propellants, mm.
仪器:超景深三维显微镜,VHX‑2000C,KEYENCE公司;RF‑C7000爆热型自动热量计,长沙瑞方能源科技有限公司。
采用一步绿色脱硝工艺制备梯度硝基单基发射
type | sample | reaction condition | ||
---|---|---|---|---|
C / % | T / ℃ | t / min | ||
seven‑holes single‑base propellant | sample 1 | - | - | - |
sample 1‑60 | 12 | 75 | 60 | |
sample 1‑90 | 12 | 75 | 90 | |
sample 1‑120 | 12 | 75 | 120 | |
sample 1‑150 | 12 | 75 | 150 | |
one‑hole single‑base propellant | sample 2 | - | - | - |
sample 2‑60 | 12 | 75 | 60 | |
sample 2‑90 | 12 | 75 | 90 | |
sample 2‑120 | 12 | 75 | 120 | |
sample 2‑150 | 12 | 75 | 150 | |
non‑hole single‑base propellant | sample 3 | - | - | - |
sample 3‑60 | 12 | 75 | 60 | |
sample 3‑90 | 12 | 75 | 90 | |
sample 3‑120 | 12 | 75 | 120 | |
sample 3‑150 | 12 | 75 | 150 |
Note: C is the concentration of denitration reagent ,%. T is the denitration reaction temperature ,℃. t is the denitration reaction time, min.

图1 梯度硝基单基发射药制备过程示意图
Fig.1 Process schematic for the preparing gradiently denitrated single‑base propellants
(1)超景深测试:将测试样品sample 1‑120、sample 2‑120、sample 3‑120纵向剖切,采用超景深三维显微镜测试样品反应层厚度,放大倍数为100×。
(2)密度试验:依据GJB 770B-2005方法,采用液体静力称量法测定梯度硝基单基发射药的密度,测试温度为(20±0.5) ℃。以去离子水为介质,取梯度硝基单基发射药样品(8±0.0002) g,每个样品平行测试2次,两次测试结果差值小于0.01 g·c
(3)直径表征:依据GJB 770B-2005方法412.1小型药药性尺寸测量法,采用ISO‑9001型数显游标卡尺测定梯度硝基单基发射药样品的直径d,每个样品测试50个,计算50次直径结果的平均值。
(4)爆热试验:依据GJB 770B-2005方法701.1绝热法,采用氧弹量热仪测定单基发射药样品分子裁剪反应前后的能量变化。称取单基发射药样品(6±0.0001) g,在容积为5.8 L的爆热氧弹内引爆,测试样品的爆热值,每个样品测试一
由于发射药颗粒的分子裁剪反应过程是利用脱硝试剂将发射药颗粒表层硝酸酯基转变为羟基,而单基发射药中含能基团硝酸酯基的含量与其能量成正比,因此本研究利用分子裁剪反应前后单基发射药样品能量的变化来反映发射药颗粒表层中硝酸酯基被分子裁剪的程度,即脱硝率。
(1) |
式中,α为脱硝率,%;Q0为单基发射药的爆热值,kJ·k
为探究药型对单基发射药分子裁剪产物反应层厚度的影响,采用超景深三维显微镜,对sample 1‑120、sample 2‑120、sample 3‑120的剖切表面有明显的白色脱硝区域的反应层厚度进行了测量,结果见

a. sample 1‑120

b. sample 2‑120

c. sample 3‑120
图2 3种梯度硝基单基发射药的超景深图
Fig.2 Ultra‑depth of field images of the three gradiently denitrated single⁃base propellants
type | sample | ρ / g·c | Δρ / g·c | d / mm | Δd / mm |
---|---|---|---|---|---|
seven‑holes single‑base propellant | sample 1 | 1.609 | 0 | 1.596 | 0 |
sample 1‑60 | 1.604 | -0.005 | 1.607 | 0.011 | |
sample 1‑90 | 1.603 | -0.006 | 1.602 | 0.006 | |
sample 1‑120 | 1.607 | -0.002 | 1.596 | 0 | |
sample 1‑150 | 1.599 | -0.010 | 1.591 | -0.005 | |
one‑hole single‑base propellant | sample 2 | 1.618 | 0 | 2.552 | 0 |
sample 2‑60 | 1.619 | 0.001 | 2.566 | 0.014 | |
sample 2‑90 | 1.617 | -0.001 | 2.554 | 0.002 | |
sample 2‑120 | 1.615 | -0.003 | 2.559 | 0.007 | |
sample 2‑150 | 1.620 | 0.002 | 2.523 | -0.029 | |
non‑hole single‑base propellant | sample 3 | 1.602 | 0 | 1.522 | 0 |
sample 3‑60 | 1.585 | -0.017 | 1.512 | -0.010 | |
sample 3‑90 | 1.591 | -0.011 | 1.531 | 0.009 | |
sample 3‑120 | 1.597 | -0.005 | 1.534 | 0.012 | |
sample 3‑150 | 1.596 | -0.006 | 1.542 | 0.020 |
Note: ρ is the density of the propellant sample, g·c

图3 3种药型单基发射药的脱硝率随时间变化图
Fig.3 The denitration rates of the three single⁃base propellants with time
为探究药型尺寸对3种单基发射药分子裁剪反应过程动力学的影响,将不同工艺条件下单基发射药的脱硝率α带入到Avrami模
Avrami模型方程为:
(2) |
Avrami模型方程对数形式为:
(3) |
式中,α为单基发射药的脱硝率,%;k为反应速率常数,mi
绘制ln[-ln(1-α)]与lnt的拟合曲线,拟合的相关参数如
T / ℃ | seven‑holes single‑base propellant | one‑hole single‑base propellant | non‑hole single‑base propellant | |||
---|---|---|---|---|---|---|
n | n | n | ||||
70 | 1.292 | 0.9811 | 0.885 | 0.9679 | 0.834 | 0.9969 |
75 | 1.330 | 0.9898 | 0.791 | 0.9269 | 0.765 | 0.9972 |
80 | 0.956 | 0.9445 | 0.884 | 0.9967 | 0.608 | 0.9847 |
Note: n is Avrami model index.
由上
(1) 扩散系数的计算
3种梯度硝基单基发射药为圆柱体,假设圆柱体由若干个平面组成,每个都平面符合Fick定律的稳态扩散。水合肼作为扩散物质从发射药表面向内部扩散,假设界面处水合肼与硝酸酯基反应速率远大于水合肼通过反应层的扩散速率。如
(4) |
式中,dm为时间dt后通过反应层迁移的水合肼的质量,g;S为平板间接触面积,m

图4 水合肼在单基发射药中的稳态扩散示意图
Fig.4 Schematic diagram of steady⁃state diffusion of hydrazine hydrate in the single⁃base propellants
由于dm的水合肼流扩散到发射药未反应界面后,会与发射药中的硝酸酯基反应,形成体积为Sdδ的产物层,因此水合肼迁移过来的量dm正比于Sdδ,即:
(5) |
对
(6) |
根据文献[
(7) |
式中,D为扩散系数,
(2) 反应层厚度的计算
假设单基发射药分子裁剪反应的产物层中只有纤维素且纤维素的能量忽略不计,对于硝酸酯基分布均匀的单基发射药进行分子裁剪反应过程前后单颗发射药颗粒的能量与未反应芯的体积成正比。
(8) |
式中,为单颗单基发射药的能量,J;为单颗梯度硝基单基发射药样品的能量,J;为单颗单基发射药的体积,m
已知单基发射药分子裁剪反应过程前后的爆热值和密度,计算单颗梯度硝基单基发射药中未反应芯的体积:
(9) |
式中,为单颗单基发射药的质量,g;为单颗梯度硝基单基发射药样品的质量,g。
由
(10) |
式中,为单基发射药的密度g·c
根据圆柱体积与半径的关系,此时可得梯度硝基单基发射药未反应芯的半径ri:
(11) |
单基发射药颗粒半径r0与梯度硝基单基发射药未反应芯半径ri 之差即为反应层厚度δ:
(12) |
式中,δ为反应层厚度,mm;r0为单基发射药颗粒半径,mm;ri为梯度硝基单基发射药未反应芯半径,mm。
通过不同工艺条件下分子裁剪反应前后单基发射药的爆热值和密度,可得不同工艺条件下单基发射药分子裁剪反应过程的反应层厚度。将不同工艺条件下的反应层厚度代入

a. seven‑holes single‑base propellant

b. one‑hole single‑base propellant

c. non‑hole single‑base propellant
图5 3种单基发射药的δ与
Fig.5 Fitting diagrams of δ and
type | T / ℃ | D×1 |
---|---|---|
seven‑holes single‑base propellant | 80 | 3.190 |
one‑hole single‑base propellant | 70 | 3.811 |
75 | 6.641 | |
80 | 10.226 | |
non‑hole single‑base propellant | 70 | 3.715 |
75 | 5.063 | |
80 | 4.200 |
Note: D is the diffusion coefficient,
将七孔、单孔和无孔单基发射药的Avrami指数n值的平均值1.193、0.853和0.736,带入到Avrami方程
(13) |
(14) |
(15) |
为了获得七孔、单孔和无孔单基发射药分子裁剪反应过程的速率常数,将不同工艺条件下3种单基发射药的脱硝率α分别带入Avrami方程式(

a. seven‑holes single‑base propellant

b. one‑hole single‑base propellant

c. non‑hole single‑base propellant
图6 -ln(1-α)-
Fig.6 Fitting curves of -ln(1-α)-
type | T / ℃ | k / mi |
---|---|---|
seven‑holes single‑base propellant | 70 |
2.34×1 |
75 |
3.04×1 | |
80 |
3.68×1 | |
one‑hole single‑base propellant | 70 |
1.19×1 |
75 |
1.67×1 | |
80 |
2.01×1 | |
non‑hole single‑base propellant | 70 |
3.49×1 |
75 |
4.41×1 | |
80 |
5.10×1 |
Note: k is the reaction rate constant, mi
在化学反应中,反应速率常数与温度的关系式可用Arrhenius公
(16) |
式中,A为指前因子;T为温度,K;Ea为分子裁剪反应过程的表观活化能,kJ·mo
将求得的反应速率常数k带入到Arrhenius

a. seven‑holes single‑base propellant

b. one‑hole single‑base propellant

c. non‑hole single‑base propellant
图7 3种单基发射药在不同温度下的Arrhenius拟合曲线
Fig.7 Arrhenius fitting curves of the three single⁃base propellants at different temperatures
以3种不同的圆柱粒状单基发射发射药为研究对象,进行表层硝酸酯基分子裁剪反应,制备出3种梯度硝基单基发射药。借助Avrami模型,探究了药型对单基发射药表层硝酸酯基分子裁剪反应过程动力学的影响,得出了以下结论:
1)在相同的工艺条件下,不同药型的单基发射药的反应层厚度和脱硝率不同,其中比表面积最大的无孔单基发射药具有最大的反应层厚度和脱硝率。对于七孔和单孔单基发射药,孔道的反应层厚度均大于发射药粒表层的反应层厚度。
2)Avrami模型适用于描述3种不同药型的单基发射药表层硝酸酯基分子裁剪反应过程,根据3种单基发射药的Avrami指数n值可以得出,在70~80 ℃温度范围内,单孔单基发射药与无孔单基发射药的分子裁剪反应过程受内扩散和界面化学反应共同控制;而七孔单基发射药的分子裁剪反应过程在70~75 ℃受界面化学反应过程控制,在80 ℃时受内扩散和界面化学反应共同控制;
3)根据Fick第一定律,借助不同工艺条件下单基发射药的反应层厚度计算得到不同温度下水合肼在3种单基发射药中的扩散系数,且扩散系数均随反应温度的增大而增大。
4)根据Arrhenius公式获得在70~80 ℃温度范围内七孔、单孔和无孔单基发射药分子裁剪反应过程的表观活化能分别为45.84、52.88 kJ·mo
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