摘要
为了研究铝粉/锆粉/高氯酸钾(Al/Zr/KClO4)点火药的低湿热老化机制,将Al/Zr/KClO4点火药在85,71,60 ℃和50 ℃下分别进行加速老化,利用热分析技术、X射线光电子能谱(XPS)、扫描电镜‑X射线能谱(SEM‑EDS)分析了低湿条件下Al/Zr/KClO4点火药热分解性能和表面元素与形貌随着温度和时间的变化。结果表明,在加速老化时,随着老化时间的增加,KClO4晶体表面部分分子降解生成KClO3和KCl,Zr表面在热的作用下进一步氧化生成ZrO2,Al未见明显变化,同时,各组分表面形貌未发生变化。Al/Zr/KClO4点火药热分解活化能和热焓值随着老化时间的增加呈现下降趋势,与未老化的点火药相比,85 ℃老化160 d活化能降低了29.57 kJ·mo
图文摘要
The accelerated thermal aging of Al/Zr/KClO4 ignition agent was carried out under the condition of relative humidity less than 10%. The thermal decomposition properties before and after aging were investigated. The surface element analysis of ignition agent was carried out by XPS, and the change of chemical composition during aging was characterized. The aging kinetics was fitted with the change of the content of each component and the thermal decomposition performance of Al/Zr/KClO4 ignition agent as parameters. The aging mechanism of Al/Zr/KClO4 was found and the aging process was fitted.
电爆管作为一类重要的火工品,电热桥丝通电后产生热量,诱导点火药分解和燃烧,并迅速产生大量的热量和气体,实现起爆、点火和分离等功能,广泛地应用于航天领域及武器装备系
电爆管的储存时间长,因环境因素的影响点火药不可避免地会发生老化。物理化学性质的改变导致点火药的性能下降甚至发生点火失
为此,本研究在相对湿度(RH)<10%下,对Al/Zr/KClO4点火药进行了85,71,60 ℃和50 ℃不同时间的老化,利用热分析、XPS及SEM‑EDS等技术手段,通过考察低湿热老化后Al/Zr/KClO4点火药的热分解性能、表面形貌和元素含量,研究其老化中的化学机理,并进一步通过反应速率、热焓值、各组分元素等参量的变化拟合热老化动力学模型,获得了活化能等相关参数,从及动力学角度进一步阐述了老化过程。
铝粉,纯度≥99.8%,平均粒径5 μm,阿拉丁试剂公司;锆粉,阿拉丁试剂公司;KClO4,分析纯,纯度≥99.8%,成都科隆化学有限责任公司。
同步热分析仪(TG/DSC),NETZSCH STA 449F3,德国耐驰公司;扫描电子显微镜(SEM),TM4000日立公司,X‑射线能谱仪(EDS),Quantax75型, BRUKER公司;X‑射线光电子能谱仪(XPS),赛默飞公司。
将Al,Zr,KClO4混合置于密封罐中,在室温条件下控制相对湿度低于10%,85 ℃加速老化至28,70,145 d和160 d,71 ℃下老化至63,130,160 d和258 d,在60 ℃老化96,130,258、399、438 d和469 d,50 ℃老化96、130、258、539、578 d和609 d。
由于85 ℃老化后的点火药性能变化最明显,因此研究对老化前的Al/Zr/KClO4点火药及85 ℃下不同老化时间(28,70,145 d和160 d)的Al/Zr/KClO4点火药进行了热分析、表面形貌和元素研究。
用同步热分析仪以5,10,15 ℃·mi
利用XPS检测点火药老化的化学组分变化XPS真空压力1
对老化前的Al/Zr/KClO4点火药及85 ℃下不同老化时间(28,70,145 d和160 d,升温速率为10 ℃·mi
a. DSC curves at 10 ℃·mi
b. heat of reaction
图1 老化前的Al/Zr/KClO4点火药及85 ℃下不同老化时间(28,70,145 d和160 d)的Al/Zr/KClO4点火药的热分解
Fig.1 Thermal decomposition of unaged and aged Al/Zr/KClO4 ignition agent with different aging time (28, 70, 145 d and 160 d) at 85 ℃
由
研究由
进一步研究老化后Al/Zr/KClO4点火药的热分解动力学,将DSC曲线的分解峰温代入Kissinger方程和Ozawa方程进行拟
system | EK /kJ·mo | lg(AK/ | EO /kJ·mo | ||
---|---|---|---|---|---|
Unaged | 287.64 | 18.60 | 0.9931 | 286.12 | 0.9937 |
85 ℃‑28 d | 280.45 | 18.12 | 0.9969 | 279.27 | 0.9981 |
85 ℃‑70 d | 265.11 | 17.07 | 0.9965 | 264.71 | 0.9979 |
85 ℃‑145 d | 258.78 | 16.64 | 0.9993 | 258.70 | 0.9993 |
85 ℃‑160 d | 258.07 | 16.59 | 0.9962 | 257.52 | 0.9962 |
Note: Subscript EK, AK, ,data obtained by Kissinger method; subscript EO, data obtained by Ozawa method.
为了进一步考察老化对Al/Zr/KClO4热分解速率的影响,将
(1) |
式中,α为反应深度;为时间,s;为反应速率,
计算结果如
图2 不同老化时间老化前后的Al/Zr/KClO4点火药在1000 ℃下的反应速率(α=0.5)
Fig.2 The reaction rate of Al/Zr/KClO4 ignition agent before and after aging at different aging time at 1000 ℃(α=0.5)
为了研究老化对Al/Zr/KClO4点火药化学组分的变化,利用XPS对老化前及85℃下老化不同时间的Al/Zr/KClO4点火药进行表征,结果如
a. Cl element peak fitting
b. Zr element peak fitting
c. Al element peak fitting
d. atomic ratio of Cl element
e. atomic ratio of Zr element
f. atomic ratio of Zr element
图3 不同老化时间老化前后的Al/Zr/KClO4点火药的XPS分峰拟合
Fig.3 XPS peak fitting of unaged and aged Al/Zr/KClO4 ignition agent at the different aging time
由
由
从
为了进一步考察老化对Al/Zr/KClO4点火药的结构变化的影响,研究利用SEM‑EDS观察KClO4、Zr及Al表面形貌及元素含量,结果如
a. element distribution of KClO4 particles
b. element distribution of Zr particles
c. element distribution of Al particles
d. energy spectrum of KClO4 particles
e. energy spectrum of Zr particles
f. energy spectrum of Al particles
图4 未老化Al/Zr/KClO4的SEM‑EDS分析
Fig.4 SEM‑EDS analysis of unaged Al/Zr/KClO4
研究首先利用EDS识别每种颗粒的物质,
将SEM放大倍数调至2000倍,对85℃下不同老化时间老化前后的Al/Zr/KClO4点火药进行了表面形貌表征,结果如
a. unaged
b. aging 28 d
c. aging 70 d
d. aging 145 d
e. aging 160 d
图5 不同老化时间老化前后Al/Zr/KClO4点火药的SEM形貌表征
Fig.5 SEM morphology characterization of Al/Zr/KClO4 ignition agent before and after aging with different aging time
由XPS分析结果可知,Al在热老化过程中组分相对比较稳定,有效活性组分没有明显改变,因此对
sample | O | Al | Cl | K | Zr |
---|---|---|---|---|---|
P1‑unaged | 78.85 | 0.41 | 11.83 | 8.55 | 0.36 |
P2‑28 d | 62.58 | 1.57 | 17.95 | 17.7 | 0.2 |
P3‑70 d | 71.32 | 2.51 | 14.36 | 10.51 | 1.3 |
P4‑145 d | 58.96 | 2.15 | 16.02 | 12.22 | 10.65 |
P5‑160 d | 62.36 | 5.39 | 18.13 | 13.48 | 0.64 |
Z1‑ unaged | 55.67 | 4.93 | 1.16 | 1.07 | 37.17 |
Z2‑28 d | 59.82 | 13.74 | 2.15 | 1.45 | 22.84 |
Z3‑70 d | 80.53 | 5.93 | 7.16 | 5.25 | 1.13 |
Z4‑145 d | 57.44 | 6.89 | 16.35 | 7.95 | 11.37 |
Z5‑160 d | 68.92 | 12.72 | 0.62 | 0.52 | 17.22 |
Note: Spots P1, P2, P3, P4 and P5 were the domains of KClO4 particles; spots Z1, Z2, Z3, Z4 and Z5 were the domains of Zr particles
以上研究表明,Al/Zr/KClO4点火药在低湿热老化时,组分中的KClO4和Zr会发生变化,但对于点火药的老化需要进一步明确其老化中温度和时间效应,才能支撑产品老化评估和性能提升。通过考察Al/Zr/KClO4点火药在85 ℃下老化不同时间后的热分解和表面形貌及元素变化,发现在85 ℃老化的Al/Zr/KClO4点火药的分解热焓、高温下分解速率(1000 ℃)、KClO4的降解原子百分比随老化时间增加而下降,Zr的氧化程度随老化时间增加而增加。为了进一步研究Al/Zr/KClO4点火药的老化温度和时间效应,使用非线性拟合方法,对老化过程中某物理量的随时间的变化进行拟合求得反应速率常数,用不同老化温度下的速率常数对Arrhenius方
a. decomposition rate of Al/Zr/KClO4 (1000 ℃)
b. decomposition enthalpy of Al/Zr/KClO4
b. KClO4 degradation
d. Zr oxidation
e. KClO3 formation
f. KCl formation
图6 Al/Zr/KClO4分解速率(1000 ℃),分解热焓,KClO4老化降解,Zr氧化,KClO3和KCl生成等参量热老化动力学拟合曲线
Fig.6 Thermal aging kinetic fitting curves of Al/Zr/KClO4 decomposition rate ( 1000 ℃), decomposition enthalpy, aging degradation of KClO4, oxidation of Zr, formation of KClO3 and KCl
type | Ea / kJ·mo | lg(A/ | f(α) | |
---|---|---|---|---|
reaction rate (T=1000 ℃) | 95.86 | 18.80 | 1‑α | 0.90 |
heat of reaction | 44.96 |
2.94×1 |
(1‑α | 0.34 |
KClO4 | 128.90 | 31.13 |
(1‑α | 0.94 |
Zr | 117.80 | 29.45 | (1‑α)4 | 0.93 |
KClO3 | 102.60 | 18.66 |
(1‑α | 0.24 |
KCl | 144.27 | 27.85 |
(1‑α | 0.37 |
Note: Ea, A, f(α),
由
由
(2) |
Zr老化动力学方程为:
(3) |
式中,α为反应深度;为反应速率,
老化过程如
图7 Al/Zr/KClO4点火药表面的KClO4,Zr组分在不同温度下的老化反应进程
Fig.7 The reaction process of KClO4 and Zr components on the surface of Al/Zr/KClO4 ignition agent at different aging temperatures
在GJB 736.8-90火工品试验方法中,加速老化试验温度为71 ℃。此温度(71 ℃)下Al/Zr/KClO4的老化机理如
图8 Al/Zr/KClO4点火药老化机理示意图
Fig.8 Schematic diagram of the aging mechanism of Al/Zr/KClO4 ignition agent
利用GJB 736.8-90火工品试验方法,进一步评估加速老化所对应常温下的贮存时间。在GJB 736.8-90火工品试验方法中,71 ℃法中采用2.7的温度系数对应的活化能在92.36 kJ·mo
(4) |
式中,γ为温度系数,A为温度增量,取10 ℃,R为普适气体常数,T1为加速试验温度,T2为贮存温度。
(1)低湿加速热老化过程中,随着老化时间的增加,Al/Zr/KClO4点火药热分解活化能和热焓值下降。KClO4降解生成KClO3和KCl,Zr在热的作用下,表面进一步氧化生成ZrO2,导致有效活性组分降低。老化机理函数为n级反应。
(2)在Al/Zr/KClO4老化过程中,Zr的氧化速率高于KClO4的降解速率,老化早期二者的速率较快,随着老化的进行,老化速率减缓,老化时间超过5年,老化趋于稳定,Zr的氧化反应程度大于KClO4降解的幅度。
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