INFLUENCE DE LA GRANULOMETRIE DU FER SUR LE SEUIL D'INITATION DU CHAUFFAGE LASER DU MELANGE PYROTECHNIQUE Fe/KClO_4

摘要

This paper deals with a work on the ignition of explosive reactions of pyrotechnic mixtures by means of a laser diode. An experimental set up, containing a 7 W power laser diode is described. This apparatus is based on a deposit of energy concentrated by means of two lenses. The size of laser spot is 186μm. The amount of energy is calibrated by means of a joulemeter and this parameter varies from some J.cm~(-2) to more than 1000 J.cm~(-2). The ignition is marked, in the time, by a photodiode joined to a system of fast acquirement. The tests were achieved for a 2.37 W power. The pyrotechnic is a mixture of iron and of potassium perchlorate (62/38 in mass percentage).In this work, iron granulometry varies in the interval of 1 to 50μm. It was therefore possible to correlate the energy threshold of initiation and the delay of ignition with the different granulometries. The distribution size distribution of the different shares of iron was achieved by analysis of pictures obtained by means of a scanning electronic microscope. We showed a very strong influence of the grain size of iron on the threshold of ignition and on the ignition delays. When the granulometry of iron increases from 1.6 to 52μm. the energy threshold changed from 4 J.cm~(-2) to 1074 J.cm~(-2).