Initiation of some energetic materials by microwave heating

Abstract

Ziindung einiger energiereicher Verbindungen durch Autheizen mit Mikrowellen Das Autheizen mit Mikrowellen von Ammoniumnitrdt (AN). Tetryl. PETN, RDX, HMX.TNT, Emulsionssprengstoff, Composition C-4 und Amnioiiiumperchlorat (AP) wurde durchgefuhrt bei einer Frequenz von 2450 +-SO MHz. Die Energietrager wurden in Kalknatron-Glasrohrc eingeschlossen und rnit Teflonund Siliconkautschukstopfcn verschlossen. Dic Zundvcrzugszeit nahm zu in dcr Rcihenfolge AN,'l'etryl, PETN, RDX. HMX und TNT. Auch die Reihenfolge fur die Ziindenergie der Energietrager war dieselbe. wenn der Anodenstrom der Mikrowcllcnquelle 1,l A und 0,s A betrug. Dcr Ziiiidvorgang der Energietrager wurde aufgezcichnct auf Videoband, wobei sich zeigte, daR die Verbiiidungen generell vor der Ziindung schmolzen. Die Temperatur der Energietrager wurde gemessen mil Thermoelementen vom K-Typ (Chromel-Alumel) und mit einem Infrarotthermometer. Die Tempcratur jeder Verbindung stieg schnell an, sobald sic sich dcm Schmelzpunkt naherte. Die Ziindung erfolgte nahe der Zundtemperatur mit einer Verziigerung. die zwischen 6 und 109 Sekunden schwankte. Amorcage de dilrercntcs cnmyositions tr&s knergbtiques suite a un Gchauffement par hyperfrequences Dcs Cchantillons de nitratc d'ammonium, dc tktryl. cle pentrite. d'hexogene, d'octogcue. de tolite. d'kmulsion explosivc. de composition C-4 et de perchlorate d'ammoniuni oiit ete soumis a un Cchaulfement par micro-odes 2 une frequence de 2450 t 50 MHz. Ces echantillons Ctaient places dans des tubes en verre ordinaire. fernies par des bouchons cn tkflon o u en caoutchouc B la silicone.Les substances presentent un retard a l'amorpgc qui va croissant dans I'ordre nitrate d'ammonium, tetryl. pentrite, hexogkne. octogCnc et tolitc. Lorsquc I'intensitC du courant applique i I'anode de la sourcc d'hypcrfrequcnces se situe entre 1,l A et 0,s A, leur energie d'amorpge s'echelonnc dans le m h e ordrc. Lenregistrement de la reaction d'amorpge par camera vidco rnontre que. d'une manikre geiierale. I'amorpge de ces substances cst prCcCdC d'une fusion. On a mesurk lcur temperature au moyen de thcrmocouplcs du type K (chromel-alumel) el de thermomktres a infrarougc. Des quc I'm s'approche du point de fusion, la temperature monte rapidement. L'amorqagc se produit au voisinage de la tenipkrature d'intlammation avec un retardvariant entre 6 et 109 secondes. SummaryMicrowavc heating of ammonium nitrate (AN), tetryl, PETN, RDX, HMX. TNT. emulsion explosive, Composition (2-4. and ammonium perchlorate (AP) was carried out at the frequency of 2450 ? SO MHz. The energetic materials were confined in sodalime glass tubes with teflon and silicon rubber plugs.The order of increasing initiation delay time was AN. tctryl, PETN, RDX. HMX, and TNT. Also. the order of the initiation energy of energetic materials was the same when the anode currents of microwave power source were 1.1 A and 0.8 A. The initiation processes of energetic materials were recorded on videotapes which showed that thc energctic materials generally melted before initiation. The tcm...

X‐Band Microwave Properties and Ignition Predictions of Neat Explosives

“…As demonstrated by the early work of Hasue et al [1] any practical microwave heating experiment requires a sample holder for the explosive material of interest. This poses some complications to understanding the response of explosives to electromagnetic energy, as heating of the sample holder may dominate and lead to conductive heating in high field applicators.…”

“…The role of the sample holder on the dominant mode of heating -direct microwave heating of the explosive vs. conductive heating by the sample holder is explored by computationally modeling the cavity reported in Ref. [1]. The given geometric, material, and operating parameters were used.…”

“…A complete knowledge of electromagnetic properties is necessary -specifically the frequency-, temperature-, and density-dependent complex permittivity (a measure of the polarizability and absorptivity of a material). Complex permittivities of a limited number of explosive materials (AN, Comp B, HMX, Octol, PBX9502, PETN, RDX, TATB, and TNT) have been reported since the 1950's [1,[7][8][9][10][11][12]. However, different measurement techniques, frequencies (primarily in the kHz-MHz or THz ranges), densities, and humidity levels, all of which were frequently unspecified, lead to inconsistencies and uncertainties in the reported properties that are difficult to reconcile for use in applicator design and prediction.…”

“…Some of the first applied microwave work by Hasue et al [1] in 1990 demonstrated ignition of small samples (0.2 g) of ammonium nitrate (AN), tetryl, PETN, RDX, HMX, and TNT placed in a high electric field microwave applicator operating at a frequency of 2.45 GHz and applied powers up to 3.6 kW. Ignition was observed in tens of seconds and was shown to be dependent on the reported dielectric properties of the material under study.…”

“…In recent years there has been significant interest in using microwave energy as a means for ignition of explosives and propellants, enhanced/controlled burning of propellants, and detection or defeat of improvised explosive devices (IEDs) [1][2][3][4][5][6]. However, the lack of reported microwave frequency electromagnetic properties has limited predictions and understanding of the response of such materials to electromagnetic energy.…”