In 1997, low-level perchlorate contamination (<50 ng mL -1 or parts per billion) was discovered in the western U.S. Since that time, it has been found in sites scattered around the nation. Although the Environmental Protection Agency... more
In 1997, low-level perchlorate contamination (<50 ng mL -1 or parts per billion) was discovered in the western U.S. Since that time, it has been found in sites scattered around the nation. Although the Environmental Protection Agency has not established a regulation for perchlorate in drinking water, it has placed perchlorate on the contaminant candidate list (CCL) and the unregulated
Two stoichiometrically different copper(II) complexes of curcumin (stoichiometry, 1:1 and 1:2 for copper:curcumin), were examined for their superoxide dismutase (SOD) activity, free radical-scavenging ability and antioxidant potential.... more
Two stoichiometrically different copper(II) complexes of curcumin (stoichiometry, 1:1 and 1:2 for copper:curcumin), were examined for their superoxide dismutase (SOD) activity, free radical-scavenging ability and antioxidant potential. Both the complexes are soluble in ...
This study aims to evaluate the dynamic mechanical properties of a binder, used in composite propellants, with increasing amount of different solid fillers. Dynamic Mechanical Analysis (DMA) is performed to determine the region of... more
This study aims to evaluate the dynamic mechanical properties of a binder, used in composite propellants, with increasing amount of different solid fillers. Dynamic Mechanical Analysis (DMA) is performed to determine the region of glass-rubber transition temperature (T g). Further parameters were obtained from the description of the loss factor curves (tanδ) with models based on exponentially modified Gauss (EMG) distribution function. Polyurethane binders employing the polyol HTPB and diisocyanate were filled with 20, 40, and 60 mass-% of ammonium perchlorate (AP), aluminum (Al) or cyclotrimethylene trinitramine (RDX) particles, using fine and coarse mean sizes. A special turning device manufactured by Fraunhofer ICT was installed inside the curing oven in order to avoid sedimentation during curing. The cured composites were characterized by DMA in torsion mode from-100 °C to 70 °C. The good homogeneous distribution of fillers in the samples was evaluated by computational X-ray micro-tomography. The data on tanδ showed a complex structure describable at first with 2 overlapping peaks. The peak at lower temperatures is due to mobility of unrestricted binder parts (T g unr) and the second broader peak at high temperature is due to mobility of restricted binder parts (T g res). Results of tanδ, calculated areas of EMG curves and apparent activation energies of the distinct relaxation processes indicate that Al particles have higher interaction with HTPB-based polyurethane than AP and RDX. Probably Al is bonded to the binder network via isocyanate coupling with OH groups present in the surface. Ammonium perchlorate and cyclotrimethylene trinitramine particle sizes and its morphology influenced the viscoelastic properties. AP and RDX cause more changes in intensity of first peak of loss factor than Al. Increasing amount of these both particles enhances storage (G') and loss (G ") shear moduli. As a whole tanδ intensity is lowered in the main peak and Al showed an intensity increase in the second apparent peak.
The utilization of sol-gel chemical methodology to prepare nanostructured energetic materials as well as the concepts of nanoenergetics is described. The preparation and characterization of two totally different compositions is detailed.... more
The utilization of sol-gel chemical methodology to prepare nanostructured energetic materials as well as the concepts of nanoenergetics is described. The preparation and characterization of two totally different compositions is detailed. In one example, nanostructured aerogel and xerogel composites of sol-gel iron (III) oxide and ultra fine grained aluminum (UFG Al) are prepared, characterized, and compared to a conventional micron-sized Fe2O3/Al thermite. The exquisite degree of mixing and intimate nanostructuring of this material is illustrated using transmission and scanning electron microscopies (TEM and SEM). The nanocomposite material has markedly different energy release (burn rate) and thermal properties compared to the conventional composite, results of which will be discussed. Small-scale safety characterization was performed on the nanostructured thermite. The second nanostructured energetic material consists of a nanostructured hydrocarbon resin fuel network with fine am...
The effects of supersaturation level, sodium chloride (NaCl) as impurity, and the suspension density of the crystallizer content on the crystallization kinetics of ammonium perchlorate (AP) were studied in a mixed-suspension mixed-product... more
The effects of supersaturation level, sodium chloride (NaCl) as impurity, and the suspension density of the crystallizer content on the crystallization kinetics of ammonium perchlorate (AP) were studied in a mixed-suspension mixed-product removal crystallizer. The product crystals have a plate-like morphology. The crystal size distribution is not affected by the supersaturation level. There was a deviation from the ideal population density where the growth rate of pure AP crystallization was size dependent with the order of 0.4 according to Abegg, Stevens and Larson (ASL) model. However, the ASL model was not found to be suitable to express the growth rate of the crystals in NaCl containing AP solution. Also when suspension density of the crystallizer increased, secondary nucleation was observed.
Compared to the conventional ammonium perchlorate based solid propellants, burning of ammonium nitrate (AN) based propellants produce environmentally innocuous combustion gases. However, the near room temperature phase transition limits... more
Compared to the conventional ammonium perchlorate based solid propellants, burning of ammonium nitrate (AN) based propellants produce environmentally innocuous combustion gases. However, the near room temperature phase transition limits the application of AN ...
Résumé/Abstract We present some of our initial experimental results from laser induced breakdown spectroscopy (LIBS) studies of few high energy materials such as a simple match stick (MS) and BKNO 3 (BPN), and ammonium perchlorate (AP)... more
Résumé/Abstract We present some of our initial experimental results from laser induced breakdown spectroscopy (LIBS) studies of few high energy materials such as a simple match stick (MS) and BKNO 3 (BPN), and ammonium perchlorate (AP) using nanosecond (ns), picosecond (ps), and femtosecond (fs) pulses. The characteristic peaks of each sample in different time domains are analyzed. The merits and de-merits of ultrashort pulses in LIBS experiments for discrimination of high energy materials are highlighted.
... Anuj A. Vargeese, Satyawati. S. Joshi* and VN Krishnamurthy. Department of Chemistry, University of Pune, Pune 411007, India. Cryst. Growth Des. , 2008, 8 (3), pp 1060–1066. DOI: 10.1021/cg070464+. Publication Date (Web ...
