Jinn-Shing Lee

A study on the thermal decomposition behaviors of PETN, RDX, HNS and HMX

Abstract Pentaerythritol tetranitrate (PETN), cyclotrimethylene trinitramine or octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (RDX), hexanitrostilbene or 2,2′,4,4′,6,6′-hexanitrostilbene (HNS) and cyclotetramethylene tetramine, hexahydro-1,3,5-trinitro-1,3,5-triazine (HMX) are very important high explosives. All are used in a wide variety of military and industrial formulations owing to their suitable properties. Many researchers have demonstrated the usefulness of the above four energetic materials in explosive components. In this work, the thermal decomposition characteristics of PETN, RDX, HNS and HMX were studied using thermal analytical techniques (TG and DSC). Their compatibility with silicone rubber and the kinetic parameters such as decomposition activation energies and the frequency factor of the reaction are also evaluated by non-isothermal differential scanning calorimetry (DSC) techniques.

Thermal properties and shelf life of HMX-HTPB based plastic-bonded explosives

Abstract Plastic-bonded explosives (PBXs) with different amounts of polymer and based on explosives with different particle size distributions have been compared for their thermal properties and shelf life. Chung Shan Institute of Science and Technology has extensive experience with the processing of hydroxyl terminated polybutadiene (HTPB)-based PBXs. The investigation showed that the shelf life of HMX-based formulations is longer than 60 years at ambient temperature. The thermal properties of three HMX-based formulations such as specific heat, linear thermal expansion coefficient, auto-ignition temperature and kinetic parameters concerning the explosion, explosion temperature, etc. are very close with the exception of glass transition temperature.

The devitrification behavior of calcium phosphate glass with TiO2 addition

Abstract The effects of TiO 2 addition on the devitrification behavior of the calcium phosphate glasses were investigated using thermal analysis techniques. Both the DTA traces of coarse powder and fine powder for calcium phosphate glasses indicated that the glass transition temperature ( T g ), gradually increased. To determine whether the devitrification begins at the surface or in the bulk of these glasses, we recorded DTA curves of coarse powder and fine powder. By comparing the exothermic peak temperature of coarse powder and fine powder, we found that the two exothermic peak temperatures tend to be nearer when the amount of TiO 2 in calcium phosphate is increased. This indicates that bulk devitrification or, more appropriately, devitrification at the internal interface is easier, i.e., TiO 2 is an effective nucleating agent in these glass systems.

The DSC studies on the phase transition, decomposition and melting of potassium perchlorate with additives

Abstract It has been shown that the addition of metal oxide to potassium perchlorate gives rise to change in the thermochemical behavior of the potassium perchlorate. Some investigations on the particle sizes and materials were examined, and given data for choosing optimum weight percentage to achieve certain firing characteristics of hot-wire pyrotechnic devices. In this study, the additives (Al 2 O 3 and Fe 2 O 3 ) are found to have no effect on the crystal structure transformation, the fusion of KClO 4 and the fusion of KCl. But both of the metal oxide powders exhibited a remarkable acceleration effect on the decomposition of KClO 4 , especially Fe 2 O 3 does.

The thermal behaviors and safety characteristics of composition B explosive

The explosive composition B is an old explosive. It was developed by Britishers during World War I and World War II. It was also used by the United States in World War II. The differential scanning calorimetry (DSC) curves of mixtures that of the explosive composition B show a significant change in recent manufacture batches. In order to understand the effect of the mixtures on DSC data, the thermal behaviors and safety characteristics were reevaluated in this work.

A study of zirconium/potassium perchlorate primer mixtures

Abstract The effect of varying the percentage of Zr in Zr/KClO 4 primer mixtures has been studied. The thermal properties of the mixtures were investigated by thermogravimetry (TG), differential thermal analysis (DTA); and adiabatic calorimetry. In TG analysis, the primer mixtures show abnormal behavior when the Zr content exceeds 70%. DTA of the two-component system shows one endotherm and two exotherms, the endothermic peak near 305°C being the characteristic crystalline transition of KClO 4 from a rhombic to a cubic lattice. The first exotherm is due to the reaction between Zr and KClO 4 and the second to decomposition of residual KClO 4 . KClO 4 is found to be essential to start the reaction of Zr/KClO 4 primer mixtures and the autoignition temperature of such mixtures was determined using DTA data extrapolated to a near-zero heating rate. A pilot scale process was developed for preparing pressure cartridges for the Bruceton test and the threshold firing current and No-Fire characteristics were obtained by statistical calculation. The results show that mixtures of Zr content 40–60 wt.% are suitable fuel/oxidizer primer mixtures for 1 A/1 W, 5 min, no-fire, electro-explosive devices (EEDs).

Thermal behaviour and firing characteristics of Zr/KClO4 primer mixture containing different particle sizes of zirconium

Abstract The effect of the particle size of zirconium on the thermal behaviour and firing characteristics of Zr/KClO4 primer mixtures was studied by thermoanalytical techniques. A pilot-scale process was developed for preparing pressure cartridges whose primer mixtures had different particle sizes of zirconium. The firing characteristics were evaluated by Brucetons method and its related calculation. It was found that the Zr/KClO4 primer mixture with average particle size of 3 or 5 μm is a suitable primer mixture for 1 A 1 W−1, 5 min, No-Fire pressure cartridges.

A Thermal Decomposition Study of Individual and Co-Precipitated Y, Ba and Cu Oxalates

Y-Ba-Cu oxalate powder with a presumed Y:Ba:Cu molar ratio of 1:2:4 was prepared by a modified co-precipitation method and its solid-phase thermal decomposition was studied from 25 to 1000°C, the major evolved gases being H2O and CO2. The air-dried powder contained residual moisture. It required isothermal heat treatment for elimination of the evolved gases. The melting point of the co-precipitation Y-Ba-Cu oxalate powder, determined by DSC at a heating rate of 10°C min−1 was approximately 882°C in N2, 949°C in air and about 979°C in O2. The dependence of the sintering properties of this material upon the atmosphere and the temperature is considered.

Kinetic study of Y, Ba, Cu oxalates and coprecipitated Y-Ba-Cu oxalate

The kinetics of the decomposition of Y, Ba and Cu oxalates and coprecipitanted Y-Ba-Cu oxalate was investigated under a nitrogen atmosphere on the basis of dynamic thermogravimetric data, the average activation energies of the decomposition of Y, Ba and Cu oxalates were obtained from the slopes of the T. Ozawa plot.The average activation energies for the dehydration of these oxalate and coprecipitated Y-Ba-Cu oxalate were also evaluated from the thermogravimetric curves.

Kinetic studies on crystallization of CaO · P2O5 glass by differential thermal analysis

Abstract The crystallization mechanism of CaO·P 2 O 5 glasses was studied using non-isothermal differential thermal analysis (DTA) by comparing the kinetic parameters of the fine and coarse glass powders. The effect of a small amount of TiO 2 on the nucleation and growth kinetics was also investigated. The kinetic parameters were evaluated from DTA curves by using the variation of heating rate method. Experimental results suggest that the devitrification behaviour has a tendency to promote a change from surface nucleation to bulk nucleation when the particle size of the glass and/or the TiO 2 content is increased.