铝热剂中铝粉保护膜受热失效的实验研究

Experimental Study on the Thermal Damage Mechanisms of Aluminum-Particle Protective Film in Thermite

对铝热剂中铝粉保护膜受热失效机制进行了实验研究.在空气中加热铝粉,铝粉柱电阻由无穷大降至金属级,500℃和600℃附近点为2个突降域;温度430℃时铝粉形貌变化微小,670℃时已完全破裂;铝热剂粉末在600℃加热后仍为粉末,700℃加热后凝结为坚固的块体.实验结果表明,铝热剂中粒径约30μm铝粉的保护膜在约100℃时已被胀裂,500℃时因膜的相变收缩使开裂程度陡然加剧而部分失效;铝熔化后保护膜完全失效,铝液流动铺展到相邻铝粉和氧化铁粉表面.

An important issue to study ignition of thermite is the investigation into the damage mechanism of aluminum particles protective film under heat. Experiments have found the following rules. When the aluminum powder was heated in air, its weight decreased at first and then increased. The electrical resistance of an aluminum powder column decreased with the increase of its temperature. The resistance dropped abruptly at approximate temperatures of 500 ℃ and 600 ℃, and finally its value reached to metal level. The aluminum particles were disrupted completely at temperature of 670 ℃. The thermite powder heated at temperature of 700 ℃ was condensed into solid state. The conclusion can be inferred from above experiments that the protective film of aluminum particles partly loses its effectiveness at about 500 ℃ and no longer has any effect after the melting point of aluminum.