Synthesis, characterization, thermolysis and performance evaluation of mercuric-5-nitrotetrazole (MNT)

Mercuric-5-nitrotetrazole (MNT) was synthesized on using a reported method. The product having bulk density of 1.5 g/cm3, was obtained during this work using mercuric nitrate doped with additives such as cephol/dextrin in the process. Synthesized MNT was characterized by metal content analysis, IR and ESCA. The DTA profile indicated the thermal stability of MNT up to 200 degrees C. It revealed its higher thermally sensitive [thermal sensitive figure (S) approximately 0.8] in comparison to that of service lead azide (SLA) [S approximately 0.4]. Percussion sensitivity data also showed higher sensitivity of MNT. However, it was found less friction sensitive than SLA. The chemical stability of MNT in a carbon dioxide environment was evaluated in comparison to SLA by determining mercury (gravimetrically) and lead azide (volumetrically) contents respectively. Results obtained indicated that no discernable changes occurred in MNT, even after storage for 90 days while in case of SLA, drastic change in lead azide content was observed. IR spectra of MNT sample stored in a closed aluminum dish for 5-10 years could be superimposed on that of the freshly prepared MNT sample. The performance of MNT filled detonator no. 27 assessed in terms of extent of damage on a witness plate was found equivalent to that of the standard ASA (azide, styphynate and aluminium) composition filled detonator.     

Synthesis and characterisation of 4-picrylamino-2,6-dinitrotoluene (PADNT): a new insensitive explosive

A chemoselective reductive method has been achieved for the preparation of 4-picrylamino-2,6-dinitrotoluene (PADNT), a new insensitive energetic material which has been characterised by spectral data and elemental analysis. Some explosive properties of the compound have also been determined and the results indicate that PANDT is quite safe to impact and friction.     

Strengthening of alumina by cerium-zirconate (Ce2Zr2O7)

Composite powders of Al₂O₃ and 0 to 30 vol% Ce₂Zr₂O₇ are prepared by a hybrid sol-gel method using Al₂O₃ powders and a sol formed from Zr-alkoxide and cerium nitrate. All the Zr from the sol goes to form the cerium zirconate phase when the powders are calcined in N₂. Pressureless sintering in air at 1500°C yields composites with high density (98%). Maximum values of fracture toughness and strength, 6.5 MPa and 620 MPa respectively, (e.g. 3.5 MPa and 350 MPa for pure Al₂O₃) are obtained in 10 vol% Ce₂Zr₂O₇ composite sintered in air. The dominant mechanism for enhancement in K _IC is believed to be crack bridging. Crack bridging activity in the 10 vol% composite is found to be maximum and extends upto 190 m from the crack tip.     

Study of Molten Salt Corrosion of High Velocity Oxy-Fuel Sprayed Cermet and Nickel-Based Coatings at 900 °C

Absract Samples of Cr₃C₂-NiCr cermet and NiCrBSi coatings formed by the high velocity oxy-fuel (HVOF) process on Superni 718 superalloy have been corroded in the Na₂SO₄-V₂O₅ molten salt environment at 900 °C under cyclic conditions. The hot corrosion behavior of the coatings has been investigated by means of thermogravimetric analysis, X-ray diffraction, scanning electron microscopy/energy dispersive spectroscopy, and electron probe microanalyzer techniques. Efforts have been made to formulate the mode of corrosion attack. Both the coatings protected the substrate superalloy Superni 718 completely. While protecting the superalloy, the Cr₃C₂-NiCr cermet coating partially oxidized along the splat boundaries up to the coating substrate interface, whereas only the upper part of the coating, to about 100 μm from the surface, oxidized in the case of the NiCrBSi coating. The hot corrosion resistance of both the coatings has been attributed to the formation of protective oxides of chromium/silicon at the surface and at the splat boundaries of the coatings.     

Fast computation of spatial selections and joins using graphics hardware

Spatial database operations are typically performed in two steps. In the filtering step, indexes and the minimum bounding rectangles (MBRs) of the objects are used to quickly determine a set of candidate objects. In the refinement step, the actual geometries of the objects are retrieved and compared to the query geometry or each other. Because of the complexity of the computational geometry algorithms involved, the CPU cost of the refinement step is usually the dominant cost of the operation for complex geometries such as polygons. Although many run-time and pre-processing-based heuristics have been proposed to alleviate this problem, the CPU cost still remains the bottleneck. In this paper, we propose a novel approach to address this problem using the efficient rendering and searching capabilities of modern graphics hardware. This approach does not require expensive pre-processing of the data or changes to existing storage and index structures, and is applicable to both intersection and distance predicates. We evaluate this approach by comparing the performance with leading software solutions. The results show that by combining hardware and software methods, the overall computational cost can be reduced substantially for both spatial selections and joins. We integrated this hardware/software co-processing technique into a popular database to evaluate its performance in the presence of indexes, pre-processing and other proprietary optimizations. Extensive experimentation with real-world data sets show that the hardware-accelerated technique not only outperforms the run-time software solutions but also performs as well if not better than pre-processing-assisted techniques.     

Optimal Design of Level 1 Redundant Water Distribution Networks Considering Nodal Storage

A water distribution network (WDN) is designed to meet time-varying demands with sufficient pressure, taking into consideration an appropriate demand during peak hours. Therefore, a network has inherent redundancy in the sense that under abnormal conditions such as those arising due to pipe breaks or pump failures, deficiency in supply during peak hours can be met through additional supply during off-peak periods. However, this necessitates a storage facility at the consumer end of the network, which is normally available in the form of a sump or an overhead tank in developing countries. Such a storage enables the consumer to store water during the off-peak period and then use it during the peak period. Reliability of a WDN is assessed herein considering nodal storage, and an iterative method is proposed for the optimal design of Level 1 redundant WDNs, i.e., networks that can sustain a single pipe failure without affecting consumer services either in part or in full. The method is illustrated through an example and the designs of a network with and without storage are compared. Provision of a nodal storage is found to reduce the total cost of the network.     

Particle Characterization and Settling Velocities for a Water Supply Reservoir during a Turbidity Event

Characterization of the particle population for a location in a water supply reservoir, Kensico Reservoir, N.Y., is documented for a high turbidity event, from its onset, through alum treatment and its waning. Supporting in situ measurements included the beam attenuation coefficient at 670?nm (c670) and 660?nm (c660) [surrogates of turbidity (Tn)], particle concentrations (N) and size distributions (PSDs), and size class specific settling velocities (SVs). Laboratory measurements included chemical and morphometric analyses of individual particles, and routine measurements of Tn. The turbidity is shown to be primarily derived from clay minerals, mostly in the size range of 1.5–6?μm. An initial high c670 level (40?m?1;Tn ～ 100?NTU) decreased sevenfold in less than 1?week in response to alum treatment that largely eliminated the particle size classes responsible for the elevated turbidity. Successful SV experiments, made using a laser in situ scattering and transmissometry (LISST) instrument, for seven particle size classes in the range of 1.25–129?μm yielded SV values of 0.17–69.4?m?day?1. Size classes larger than ～ 5?μm settled much slower than Stokes law predictions, before alum treatment, indicating that these classes existed as porous flocs or aggregates. Decreases in SVs following treatment suggest changes in floc character consistent with increased porosity. In situ measurements of c670, N, PSDs, and SVs can contribute to the development and testing of a multiple particle size class model to simulate fate, transport, and impacts of suspended particles.     

Effect of different polypropylenes and compatibilizers on the rheological,mechanical and morphological properties of nylon 6/PP blends

In this work, the rheological, mechanical and morphological properties of nylon 6/polypropylene compatibilized blends were investigated. Two types of polypropylene were used. One with MFI of 40 g/10 min (PP H103) and the other with MFI of 3.5 g/10 min (PP H503). The compatibilizers used were polypropylene grafted with 6% of acrylic acid (PPgAA) and polypropylene grafted with 1% of maleic anhydride (PPgMA). The blends composition was 80/20 (wt%) for the PA6/PP binary blends and 80/10/10(wt%) for the nylon 6/PPgAA/polypropylene and nylon 6/PPgMA/polypropylene ternary blends. Torque rheometry analysis showed that when PPgAA and PPgMA were added to nylon 6/polypropylene blends, there was an increase in the torque, indicating that reactive compatibilization has occurred. There is no influence of the polypropylene MFI on the mechanical properties of the uncompatibilized and compatibilized blends. The impact strength of the blends containing PPgMA were greater than those of the blends containing PPgAA. The blends containing PPgAA are unstable. SEM analysis showed that PPgMA improves considerably the adhesion between PA6/PP phases, leading to good mechanical properties.