Abdul Qadeer Malik

Hydrocode Simulation with Modified Johnson-Cook Model and Experimental Analysis of Explosively Formed Projectiles

The formation of mild steel (MS) and copper (Cu) explosively formed projectiles (EFPs) was simulated in AUTODYN using both the Johnson-Cook (JC) and modified Johnson-Cook (JCM) constitutive models. The JC model was modified by increasing the hardening constant by 10%. The previously established semi-empirical equations for diameter, length, velocity, and depth of penetration were used to verify the design of the EFP. The length-to-diameter (L/D) ratio of the warhead used in the simulation varied between 1 < L/D < 2. To avoid projectile distortion or breakup for large standoff applications, the design of the EFP warhead was modified to obtain a lower L/D ratio. Simulations from the JC model underestimated the EFP diameter, resulting in an unrealistically elongated projectile. This shortcoming was resolved by employing the JCM model, giving good agreement with the experimental results. The projectile velocity and hole characteristics in 10-mm-thick aluminum target plates were studied for both models. The semi-empirical equations and the JC model overestimated the projectile velocity, whereas the JCM model underestimated the velocity slightly when compared to the experimental results. The depths of penetration calculated by the semi-empirical equations in the aluminum (Al) target plate were 55 and 52 mm for Cu and MS EFPs, respectively.

Effect of concentration of Surfactant on the Exfoliation of Graphite to Graphene in Aqueous Media

Graphite was exfoliated to graphene by tip sonic using sodium cholate as a surfactant in the presence of Millipore water as a medium. The use of water as a solvent for exfoliation purposes is very important due to its environmentally friendly nature and almost no cost, contrary to organic media. Two different concentration ratios of surfactants are used in the present work. As a result, graphene dispersions with two different concentrations of 5 mg/ml and about 7 mg/ml respectively were obtained in aqueous media. It was observed that the optimum concentration of surfactant has an effective role in the exfoliation of graphite to graphene. Concentrations of graphene dispersions were studied through UV spectroscopy, while Raman spectroscopy, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) were used to study the quality of the exfoliated graphene flakes.

Correction: AACVD of Cu2−xS, In2S3 and CuInS2 thin films from [Cu(iBu2PS2)(PPh3)2] and [In(iBu2PS2)3] as single source precursors

Correction for ‘AACVD of Cu2−xS, In2S3 and CuInS2 thin films from [Cu(iBu2PS2)(PPh3)2] and [In(iBu2PS2)3] as single source precursors’ by Sajid N. Malik et al., New J. Chem., 2015, 39, 4047–4054.

An Investigation of Thermal Decomposition Kinetics of Nano Zinc Oxide Catalyzed Composite Propellant

Thermal decomposition and the combustion mechanism of ammonium perchlorate/hydroxyl-terminated polybutadiene propellant has been widely investigated during the past decades. The focus in the present work is to investigate the catalytic effect of zinc oxide (ZnO) nano particles on the decomposition mechanism and kinetic behavior of composite solid propellant. Thermal cum kinetic evaluation of the catalyzed and non-catalyzed version of composite propellant has been carried out by four different kinetic methods, including Kissinger method, Flynn–Wall–Ozawa method, Friedman method, and Kissinger–Akahira–Sunose method. Differential scanning calorimetry and thermogravimetry have been used to identify the changes in the thermal and kinetic behavior of the catalyzed composite propellant. The major effect in the catalyzed propellant was lowering of the decomposition temperature by nearly 52°C. The activation energy also decreased, whereas the rate constant increased by the addition of nano zinc oxide confirming the catalytic activity in the composite solid propellant. The activation energy graphs for both versions of the propellant have shown variations with respect to different degrees of conversion.

Analytical performance study of explosively formed projectiles

Hydrocode simulations are carried out using Ansys Autodyn (version 11.0) to study the effects of the liner material (mild steel, copper, armco iron, tantalum, and aluminum) on the shape, velocity, traveled distance, pressure, internal energy, temperature, divergence or stability, density, compression, and length-to-diameter ratio of explosively formed projectiles. These parameters are determined at the instants of the maximum as well as stable velocity during the flight towards the target. The results of these parameters present the potential capability of each liner material used to fabricate explosively formed projectiles. An experimental analysis is performed to study the velocity status and the length-to-diameter ratio of explosively formed projectiles.

Dialkyldiselenophosphinato-metal complexes – a new class of single source precursors for deposition of metal selenide thin films and nanoparticles

We report here a new synthetic approach for convenient and high yield synthesis of dialkyldiselenophosphinato-metal complexes. A number of diphenyldiselenophosphinato-metal as well as diisopropyldiselenophosphinato-metal complexes have been synthesized and used as precursors for deposition of semiconductor thin films and nanoparticles. Cubic Cu2-xSe and tetragonal CuInSe2 thin films have been deposited by AACVD at 400, 450 and 500 °C whereas cubic PbSe and tetragonal CZTSe thin films have been deposited through doctor blade method followed by annealing. SEM investigations revealed significant differences in morphology of the films deposited at different temperatures. Preparation of Cu2-xSe and In2Se3 nanoparticles using diisopropyldiselenophosphinato-metal precursors has been carried out by colloidal method in HDA/TOP system. Cu2-xSe nanoparticles (grown at 250 °C) and In2Se3 nanoparticles (grown at 270 °C) have a mean diameter of 5.0 ± 1.2 nm and 13 ± 2.5 nm, respectively.

Liner Material's Output Characteristics of Explosively Formed Projectiles (EFPs)

The output considerations: velocity, pressure, density, internal energy, temperature and L/D ratio of explosively formed projectiles (EFPs) were investigated. The internal energy of the EFPs was inversely proportional to the density of the liner material. The shock pressure generated and its fluctuations were highest for Fe and Ta liner materials respectively. The least pressure variations were observed for Cu along its axial direction with highest length to diameter (L/D) ratio to supports deeper penetration. The maximum difference between numerical simulation and experiment was 9.7 % for Cu EFP.

The Explosively Formed Projectile (EFP) as a Standoff Sea Mine Neutralization Device

There are many methods that can be used for the clearance of underwater ammunition; for example, sea mines. In all such techniques, the primary aim is to defuse underwater ammunition without detonation. Explosively formed projectiles (EFPs) have great potential to cleanly and safely defuse underwater ammunition. Underwater simulations and experiments were conducted to highlight the use of EFPs for safe destruction of sea mines. The copper liner configuration was used to study the penetration performance of the EFPs in water. ANSYS AUTODYN-2D hydrocode was used to simulate copper EFP penetration, passage, and impact with a target immersed in water. Simulation results were obtained by making use of Lagrangian and Euler formulations. The results indicated that the velocity of an EFP reduces sharply as it enters the water. However, the velocity of an EFP is stable in the later part of its flight through the water. The results further indicated that after covering five cone diameters (CDs) in water, the velocity of the EFP was reduced below critical and it failed to perforate an aluminum target plate of 5 mm thickness. Nevertheless, it perforated the target plate at 4 CDs in water. A known quantity of high explosive sandwiched between two plates, just like explosive reactive armor (ERA), was used as a target to simulate the sea mine. Flash X-ray was also used to record the flight and penetration of the EFP through the target plate. Simulation results matched reasonably well with the experimental results.

Study of effect of binders and loading pressures on the performance of the time delay pyrotechnic compositions

ABSTRACT An experimental investigation was carried out to determine the effect of binders and loading pressures on burning performance of B/BaCrO4 and Si/PbO/Pb3O4 delay compositions. The consolidated density and percent theoretical maximum density (%TMD) of these compositions were also studied with different binders and at multiple loading pressures. Carboxyl methyl cellulose (CMC), dextrin, and fish glue with varying wt. % were used as binders. It was observed that the burning rate of these delay compositions was inversely proportional to the binder content. The burning rate of B/BaCrO4 delay composition was 71.0 mm/s without binder. The burning rate decreased to 38.1 mm/s by adding 3.0 % fish glue. When 1.0 % CMC was added to the mixture, the burning rate decreased to 61.8 mm/s. By adding 3.0 % dextrin to the delay composition, the burning rate decreased to 38.2 mm/s. The burning rate of Si/PbO/Pb3O4 delay mixture was 38.6 mm/s without binder. The burning of this mixture decreased to 16.4 mm/s by adding 1.0 % fish glue. The loading pressures were varied from 103 to 414 MPa. The effect of loading pressures on the burning rate of both the delay compositions was marginal. The burning rate of B/BaCrO4 delay mixture decreased with the increase in loading pressure. On contrary, the change in burning rate of Si/PbO/Pb3O4 pyrotechnic delay composition was minimal by varying the loading pressures. Results also revealed that loading pressures of 345 and 348 MPa produced the minimum standard deviation in burning rate of B/BaCrO4 and Si/PbO/Pb3O4 compositions. The consolidated density and %TMD of both mixtures increased by adding binders and increasing the loading pressures.

Development and Parametric Study of B/BaCrO4/FG Pyrotechnic Delay Composition

ABSTRACT Studies were undertaken to develop and experimentally investigate the effect of Boron content, Fish Glue (binder) and ambient temperature on the charge consumption and burning rate of Boron/Barium chromate/Fish Glue (B/BaCrO4/FG) pyrotechnic delay composition in short delay devices together with measurement of exothermicity of delay composition at different fuel/oxidizer ratios. The Boron content was varied from 5% to 45%, while Fish Glue content varied from 0% to 3.0%. The measured burning rate and charge consumption increased with increasing in Boron content until maximum values of burning rate and charge consumption were recorded at 18% boron. Similarly, both burning rate and charge consumption decreased with an increase in binder content and minimum values of these parameters were recorded at 3.0% Fish Glue. The calorific value of this delay mixture also increased with an increase in Boron content until maximum calorific value recorded at about 15% Boron. The composition failed to ignite by the calorimeter as well as by the igniter at Boron contents above 40%. The delay composition filled in delay tubes was then subjected to functional tests after conditioning at a temperature of +70°C, +21°C, and –40°C. The burning rate decreased with decreasing the ambient temperature.