同步热分析法研究超级铝热剂Al/MnO_2的热安定性

Study on thermal stability of superthermite Al/MnO_2 by simultaneous thermal analysis

为研究超级铝热剂Al/MnO_2的热安定性,利用水热法制备纳米级MnO_2,采用透射电子显微镜(TEM)对纳米Al粉的氧化层厚度进行表征,计算出Al粉中纯Al的质量分数,从而确定更优配比.采用超声共混法制备得到超级铝热剂Al/MnO_2,利用X射线衍射技术(XRD)和场发射扫描电子显微镜(FE-SEM)对超级铝热剂Al/MnO_2的晶型和形貌进行表征,采用热重-差示扫描同步热分析技术(TG-DSC)在不同升温速率条件下研究了超级铝热剂Al/MnO_2的非等温热行为,通过微分Kissinger法和积分Ozawa法计算样品的活化能,对活化能计算结果进行对比.结果表明:水热法制备得到的纳米级MnO_2呈短棒状,晶型为α型,球状Al粉氧化层厚度约5 nm,纯Al质量分数约64.5%,超级铝热剂Al/MnO_2铝热反应的温度区间为540～570℃,放热量约930 J/g;利用Kissinger法和Ozawa法拟合相关性较高,计算得到的活化能分别为429.1和421.9 kJ/mol.两种方法计算得到的活化能结果相近且数值较高,表明超级铝热剂Al/MnO_2具有较好的热安定性,安全性能良好.

For the study of the thermal stability of superthermite Al/MnO2,nano-MnO2 was prepared by hydrothermal method.In order to determine optimal matching,oxide layer thickness of nano-Al powder was characterized through Transmission electronic microscopy(TEM).Then,superthermite Al/MnO2 was obtained by using ultrasonic method.The superthermite was characterized through X-ray diffraction(XRD)and Field emission scanning electron microscope(FE-SEM),and the nonisothermal behavior of the superthermite was studied by using thermogravimetric-differential scanning thermal analysis(TG-DSC)at different heating rates.The activation energy of the superthermite was comparatively calculated by Kissinger method and integral Ozawa method.Results show that the microstructure of nano-MnO2 was short rod and the crystal wasα.Oxide layer thickness of spherical nano-Al powder was about 5 nm,namely,the content of pure Al was about 64.5%.The temperature range of the thermite reaction was between 540~570℃and the heat release was about 930 J/g.Both methods had high fitting correlation that the activation energies obtained by Kissinger method and Ozawa method were 429.1 kJ/mol and 421.9 kJ/mol,respectively.The similar calculation results proved that the supertherimite Al/MnO2 has good thermal stability and safety performance.