فهرست مطالب sajjad damiri

In this study, some granulated and pressable formulations based on coating of pentaerythritol tetranitrate (PETN) explosives with high impact polystyrene polymer (HIPS), Viton fluoroelestomer and paraffin wax were developed. Thereafter, mechanical strength of pressed formulations and transition temperature of binders were evaluated using uniaxial compressive strength test and differential scanning calorimetric (DSC) method, respectively. Also, the effect of PETN particle size distribution on compressibility, mechanical strength, density and particle size of pressed samples based on HIPS binder were statistically studied and optimized using mixture design of experiments by Minitab software. In the optimized experimental conditions, the compressive strength and elastic modulus for PETN/HIPS mixture at ambient temperature and at the concentration of 4.0 wt.% of the binder, were 15.0 and 91.1 MPa, which is better than formulations based on expensive Viton polymer and paraffine wax. By using HIPS binder, increasing the amount of PETN particle size <150 μm, mechanical strength of pressed samples decrease, and also particle size distribution in the range of 150-300 μm , leads to production of better formulations.

An efficient electrocatalyst was developed based on silver nanoparticles/multi walled carbon nanotubes nanocomposite modified glassy carbon electrode (AgNPs/MWCNTs/GCE) by controlled electrodeposition and continuous double-potential pulses to test the high explosive cyclotetramethylene-tetranitramine (HMX) using cyclic voltammetry method. The electrochemical behavior of the system in various pHs was studied by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), chronoamperometry and chronocoulometry; and some reduction parameters, including the transfer coefficient (α), electron transfer number, apparent electron transfer rate, and diffusion coefficient constants of HMX were estimated. The results demonstrated that reduction of HMX by adsorptive stripping voltammetry on AgNPs/MWCNTs film could remarkably be enhanced and catalyzed compared to bare carbon nanotubes electrode, and the reduction potential could be facilitated from -0.7 V (vs. SCE) to -0.3 V, with electron exchange rate constant of 1.12±0.1 s-1 and 0.17 ±0.1 s-1 for AgNPs/MWCNTs and bare MWCNTs electrodes. Chronoamperometry studies showed a diffusion-controlled process with an apparent diffusion coefficient of 2.01×10−4 cm2 s−1 and a catalytic rate constant of 7.48 times higher than that of bare MWCNTs electrode. Also, chronocoulometric studies showed that the number of electrons transferred for electrochemical reduction of HMX was near 1.98. Under optimized conditions, the reduction peak had two linear dynamic ranges of 2.0-30.0 and 30.0-120.0 mM with the experimental detection limit of 0.2 mM and precision of <2.5% (RSD for five analyses). This modified electrode can be properly used to determine HMX in soil and groundwater samples with satisfactory results.

Aging of a sheet explosive contain RDX explosive and HTPB binder is studied at temperatures of 50, 60 and 70 oC in times 60, 120 and 180 days. Dynamic-mechanical analysis (DMA), sol – gel analysis (SGA) and hardness measurements methods are used in this research.  The changes of tan_delta in DMA, hardness amounts and soluble fraction in SGA are measured for unaged and aged samples. The obtained results showed the samples are aged with increasing of temperature and time of aging process. The pseudo-first order kinetic equation and obtained data are used for calculation of kinetic rate constants of measured properties changes. The changes in tan_delta in DMA, hardness amounts and soluble fraction in SGA indicated kinetic rate constants, respectively, 0.9-2.3´10-3, 1.9-4.8´10-3 and 1.5-5.5´10-3 per day at temperatures of 50, 60 and 70 oC. The Arrhenius equation is used for calculation of activation energy of each changes and calculation of kinetic rate constants at temperature 25 oC. Kinetic rate constant at room temperature showed a reduction 50% in measured properties of the product after 3300 days (~9 years).

A4 explosive, containing 96.5 wt. % RDX and 3.5 wt. % paraffin wax, is one of the main components in the ammunitions, and warheads of military rockets and missiles. In this work, the thermal behavior and the decomposition kinetics of this explosive has been studied experimentally by non-isothermal differential thermal analysis technique (DTA) and thermal gravimetric (TG) methods, under various heating rates (2.0-8.0 °C/min). Kinetic parameters such as activation energy and frequency factor and critical ignition temperatures for thermal decomposition of these explosives have been evaluated via the fitting-model and free-model methods, proposed by International Confederation for Thermal Analysis and Calorimetry (ICTAC). The results show a single thermal decomposition process for A4, with the integral fitting- model of [-Ln(1-α)]1/3, indicating an autocatalytic degradation with 3-dimensional diffusion mechanism. The mean kinetic parameters of activation energy (Ea) and A of exothermic decomposition of these explosives, calculated by Kissinger, Ozawa, Friedman and KAS methods, are near to 190.397 kJ/mol and 1.89E min-1. The kinetics results were used for the estimation of mass loss prediction of mentioned explosives and were statistically compared to experimental accelerated ageing consequences. By using this method, it is possible to be predicted the lifetime of explosives in the temperatures near to decompositions regions.