This study explores the development of environmentally friendly aerosol forming composites (AFCs) for use in condensed aerosol-based fire extinguishing systems (CAFES). Traditional fire suppressants often pose environmental hazards; thus, a novel approach using maltose as a combustible binder combined with potassium nitrate as an oxidant was examined. To modify the burn rate and improve combustion efficiency, calcium carbonate (CaCO3) and iron (III) oxide (Fe2O3) were incorporated as burn rate modifiers. AFCs demonstrated high combustion efficiencies (>= 95%) and variable burn rates (3.3-13.8 mm/s). The fire extinguishing concentration of AFC was found <= 53 g/m3. Comprehensive analyses including thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray diffraction, and Fourier transform infrared spectroscopy (FTIR) confirmed the formation of potassium carbonate, potassium bicarbonate, and potassium hydroxide in aerosols. Aerosol distribution within the fire test chamber was homogeneous, as evidenced by pH measurements at various locations. These findings suggest that maltose-based AFCs are promising candidates for the development of eco-friendly fire extinguishing systems.

The binder melt on the surface of aluminized composite propellants with RDX has been quantified using experimental and computational approaches. A scanning electron microscope in conjunction with energy dispersive spectroscopy was used to analyze the surface of unburnt and extinguished propellant samples. Rapid depressurization technique was used to obtain the extinguished propellants. Five propellants were prepared, keeping the aluminum and binder fraction constant at 4 % and 16 %, respectively. The RDX fraction in the propellants was varied from 3 % to 12 %. It was found that the melt on the surface of the propellant increased from 36.7 % to 43.9 % when the RDX fraction was changed from 3 % to 12 % in the propellant. For propellants containing 3 % to 9 % RDX, a region of plateau burning was observed in the pressure range of 5-7 MPa, while propellants containing 12 % RDX showed plateau burning between 7-10 MPa. image

In the present study, organically modified Montmorillonite clay with polar moiety, the Cloisite 30B, is used for preparation of Hydroxyl terminated polybutadiene (HTPB)-clay nanocomposites (HCN) by dispersion of nanoclay in polymer matrix under high shear mixing. The nanocomposites thus prepared are evaluated in composite propellants as inhibitor material for their functional utility. Several inhibition formulations containing 5 wt%-15 wt% of nanoclay, with or without the conventional filler Sb2O3, were prepared. All these formulations were evaluated for their physical, mechanical, thermal, and ablative properties. Ablation rate and density of the compositions containing Cloisite 30B is around 23% and 5% lower respectively in comparison of the base composition. Strain capability of these compositions is twofold higher than that of base composition. These compositions have also been evaluated for their smoke generation tendency by measuring infra red (IR) attenuation in the wavelength range 1.3 μm–5.6 μm and 8 μm–13 μm and thereby compared with the base composition. The corresponding results confirmed that the compositions containing Cloisite 30B as filler have much lower IR attenuation than compositions with conventional filler, Sb2O3. Replacement of 5% Sb2O3 by nanoclay showed 8% reduction in IR attenuation rate which further reduced to 16% on replacement of 15% of Sb2O3. Interfacial bonding of HCN based inhibitors is also comparable or even better than conventional inhibitors. Precisely, the nanoclay composites with Cloisite 30B as filler exhibit all desirable properties of an inhibitor.

The present work is a step towards design and fabrication of conformable temperature sensor for the prosthetic gloves/hand in the temperature range of 70 degrees C to 175 degrees C. HCl doped thin film of poly-o-methyl aniline (POMANI)-Mn3O4 nanocomposite has been used to realization of temperature sensors on glass and fire retardant glass cloth substrates. The effect of various concentrations of these nanocomposites on thin film based fabricated thermistors were experimentally investigated. The nonlinear property of NTC thermistors restricts the utility of these thermistors as temperature sensor, although they have high sensitivity for temperature sensing. Keeping above point in view, seven methods of linearization techniques have been analysed to linearise the thin film based fabricated thermistors (on glass substrate) and investigated for best results. All these methods were first designed and simulated on ORCAD P-SPICE tool. Further, shunt with log amplifier this method was used to linearise all the flexible thin film based fabricated thermistors to analyse the linearization error and temperature sensing range. The desirable temperature sensor from poly-o-methyl aniline (POMANI)-Mn3O4 nanocomposites based thermistors were investigated and fabricated for four different temperature zone points and surface temperature sensing in prosthetic gloves/hand. The zone-I was taken up to 90 degrees C, zone-II upto 120 degrees C, zone-III upto 150 degrees C and zone-IV above 150 degrees C. The contact surface can be tailored according to the requirement. The fabricated temperature sensor displayed thermistor constant (beta O-(100-170(C))) as 8080 K, activation energy 0.696eV and the dissipation constant 0.202 mu watt/degrees C. (C) 2018 Published by Elsevier B.V.

The present study n.ports on the methods of preparation for HTPB-clay nanocomposites and their mechanical, thermal and Theological properties for their functional utility as an improved binder system for composite propellants. HTPB-clay nanocomposites were prepared by dispersing organoclay Cloisite 30B (1-3 wt.%) in the polymer matrix by magnetic stirring and high shear mixing. Critical parameters like time, temperature and RPM were optimized. These nanocomposites were cured with toluene diisocyanate in the presence of the cure catalyst DBTDL. The dispersion of the nanoclay was evaluated by using small angle X-ray scattering (SAXS) and energy dispersive X-ray (EDX) spectroscopy. EDX suggested homogeneous distribution while SAXS revealed partial exfoliation of the clay particles in the polymer matrix. Superior dispersion of the nanoclay was obtained by high shear mixing. The tensile properties of the nanocomposites prepared by high shear mixing showed 10-20% more strength and elastic modulus. The nanocomposites showed thermal stability higher than the pristine HTPB. Swelling behavior revealed increased cross linking, and the theological behavior exhibited higher viscosity of the nanocomposites. In addition, the clay amount was increased up to 10 wt.% and its effect on the mechanical, thermal and swelling behavior was observed. Theoretical performance predictions of composite propellants with nanocomposites revealed their possible functional utility.

Modification in burn rate of composite solid propellant has become a necessity of a mission. Burn rate can be modified by various mean viz. (i) tailoring the ammonium perchlorate (AP) particle size, (ii) use of nano-sized particles and (iii) incorporating burn rate modifiers. Literature discusses about various burn rate modifiers. Out of these, Iron oxide (Fe2O3)/IO is the well known burn rate enhancer. Here a systematic study was carried out by undertaking experiments at varying levels of IO in composite propellant compositions. This paper attempts to understand the effect of IO content and its specific surface area on burn rate characteristics of composite propellant. This study also attempts to find out alternative to ultrafine AP and nano burn rate enhancer to account for high burning rate of composite propellant along with reduced slurry viscosity and longer pot life for easy processing. As ultrafine AP and nano burn rate enhancers have their limitations in terms of (i) high end of mix (EOM) propellant slurry viscosity, (ii) difficulty in propellant processing, (iii) less reproducibility in attaining the similar particle size in each batch results in lesser repeatability in ballistic properties of propellant, (iv) hazards involved in size reduction, (v) limitations in handling, storage and shelf life and also (vi) the higher cost of nano particles. Therefore an extensive experimental study was performed to achieve this objective. In this study, we incorporated two different grades of IO(A) and IO (B) in composite propellant compositions. The average particle size of both grades of IO i.e., A and B are of similar to 1 mu m. But the specific surface area of IO (B) was about 15 times more than IO (A). The large difference in specific surface area of both IO was due to difference in the manufacturing process. During the manufacturing of IO, the calcination temperature plays very important role in deciding the specific surface area. High specific surface area is obtained if calcination is done at very high temperature (>1773 K). Burning rate measurements were carried out. It was observed that IO is a good burn rate enhancer. Initially, the burn rate increased with the increase in % of IO. But after that only a marginal enhancement in burn rate was observed. It was noticed that though both grades of IO are effective burn rate enhancer but IO(B) was 30% more effective than IO(A). Also it was found that IO(B) is an alternative to ultrafine AP and nano burn rate modifiers. This IO(B) was further used to develop the propellant compositions with high burn rate without incorporating ultrafine AP and nano particles. Viscosity measurement and mechanical properties determination revealed that both the IOs did not much adversely alter the processing characteristics and mechanical properties of propellant. (C) 2019 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

In this article, the isothermal phase change of pure metal is studied by using an opensource CFD tool. The single-domain mass, momentum and energy conservation equations are implemented in OpenFOAM to study the solidifica-tion behavior of the pure metal. The Darcy drag source term was used in momentum conservation equation for accounting the fluid flow in mushy region and enthalpy-porosity method was used to update the liquid fraction in each cell. The developed solver is well validated with the existing experimental results. The validated solver is used to simulate the isothermal phase change behavior of the pure tin (Sn). The results are presented for the evolution of flow field, temperature field and the solid/liquid interface. Results showed that the numerical simulation predictions are in good agreement with experimental measurements.

AbstractIn present study, two types of montmorillonite clay, organically modified with polar and apolar moieties, are used, for preparation of HTPB‐clay nanocomposites (HCN) by dispersion of nanoclay in polymer matrix with high shear mixing. These nanocomposites are evaluated in composite propellants for their catalytic effect on decomposition of ammonium perchlorate a work horse oxidizer. Several composite propellant formulations containing 1–3 weight % of nanoclays over binder, were prepared. Along with this, formulations with conventional burning rate catalyst like iron oxide in 1–3 weight % over binder, and formulation without any burning rate catalyst as base composition were also processed. All these formulations were evaluated by means of theoretical prediction, end of mix viscosity, ballistic properties, mechanical properties, sensitivity parameters and thermophysical properties. Experimental results showed that HCN based compositions have lower or comparable end of mix viscosity than base compositions. Further characterization revealed that formulations with 3 weight % of nanoclays over binder have 70 % higher burning rate than base composition as well as 20–25 % higher burning rate than compositions having 3 weight % of iron oxide over binder. Pressure exponent values are determined for 3 to 11 MPa of pressure range and were found to be significantly higher for HCN based compositions (0.33 to 0.7) in comparison to the base composition. Mechanical properties and sensitivity data of HCN based compositions are comparable with base composition. Thermal studies revealed decrease in onset temperature of decomposition of AP with presence of nanoclay which may be the probable cause for enhancement in burning rate.

The fourth P. J. Paul memorial combustion science workshop was held recently in Pune, following the three previous successful meetings. A summary of the last two meetings is available in Current Science . The tradition of inviting faculty and scientists in R&D institutions to discuss work-in-progress of combustion science practised in the academic environment and problems of development in defence and aerospace industry was continued this year with the focus of problems related to propellants, propulsion and combustion in engines. Participation of a number of young researchers from some laboratories of DRDO and students from academic institutions provided a vibrant environment.

Combustion instability (CI) is a major concern during design and development of propulsion system for various rockets & missiles. This work aims to investigate effect of nitramine on combustion response of low alumunised composite propellant. To study the CI, two different propellant compositions with and without RDX were analysed for their response to ejecta using ejecta pulser. The ejecta pulser injects the teflon ball or ejecta in solid rocket motor which may trigger CI in the motor or in worst case may result in catastrophic motor failure. Both the motors were pulsed at 65% of burn time. The response of the motor to this pressure pulse was analyzed and quantified in terms of rate of change of acoustic energy (αM) which determines the stability of motor. The αM values for propellant compositions with RDX and without RDX were found to be +17.69 and +31.47 respectively which shows that the nitramine based composite propellant are less susceptible to combustion instability as compared to non-nitramine composite propellant.

A novel realisation of high gain and compact slotted planar patch antenna for the radio frequency identification (RFID) application is presented here. The antenna was printed on a dielectric Flame Retardant FR-4 Epoxy substrate of dielectric constant (εr=4.3). Simulated results obtained for this antenna exhibits resonant frequency of 5.8 GHz, better return loss of -36.91 dB, high gain of 8.308 dBi, consistent omnidirectional radiation pattern and 43 MHz impedance bandwidth within the RFID frequency range. Further parametric analysis of dimension of slots and feed line was done to acquire the required reflection coefficient, gain and 50Ω impedance of feed line. The simulation tool ZELAND IE3D version 15.20, which is based on method of moment was used to analyze and optimize the proposed antenna.

Zirconium substituted zinc–nickel ferrite nanoparticles with chemical composition of ZrxZn0.5−xNi0.5Fe2O4 (0≤x≤0.25) have been synthesized successfully by solution combustion method using high purity nitrates and fueling agent urea. Powder XRD study confirms the single phase formation of composite ferrite which belongs to cubic spinel structure. TEM further reveals the morphology of well dispersed Zn–Ni ferrite nanoparticles to be spherical. Effect of change of doping concentration of Zirconium is observed using FTIR. The saturation magnetization gradually decreases with the increase in Zr substitution and reaches minimum when x=0.25 whereas the coercivity value reaches minimum when x=0.15. DC electrical resistivity has been found to vary with increasing Zr content. The good electrical resistivity (>107Ωcm) qualify the ceramic for high frequency transformer applications.

Diamond detectors have been fabricated using commercially available detector grade polycrystalline CVD substrates for fast neutron measurement in the Indian TBM Experiment at the upcoming ITER facility. Subsequent to fabrication, the detectors were characterized for leakage current and for response to alpha particles from 238+239Pu source. The detectors were observed to have low leakage currents at a field of 1Vµm−1. The stability of the alpha response and improvement in the count rate were achieved by β-irradiation using 90Sr β source. The fast neutron response of the detectors was studied using a D–T fast neutron source in India. The detectors showed linear response in the measured neutron flux of 2.86×105–8.76×106ncm−2s−1. The neutron response of detectors of 100µm and 300µm thicknesses was compared experimentally to study the neutron response dependence on detector thickness. Experimental results show that the detector of 100µm thickness has better performance compared to the detector of thickness of 300µm. The results presented in this paper confirm the suitability of commercially available films from Diamond Materials, GmbH, Germany for detector fabrication for fast neutron monitoring. The details of detector fabrication and results of characterization are presented in this paper.

Hydrochloric acid doped thin film of poly-o-methyl aniline (POMANI)-Mn3O4 nanocomposites have been fabricated on glass substrate. The nanocomposite films showed RT-NTC characteristics in the temperature range of 35-185 degrees C with repeatability in the temperature range of 75-185 degrees C. The cut off temperature of the thermistor fabricated from the nanocomposite material was found to be between 165 and 170 degrees C. Synthesised nanocomposite material has been characterized using FT-IR, XRD, TEM for structure, morphology and TGA/DTC for thermal stability. Thermistor constant (beta) observed from RT characteristics are in the range of 7363 K-10,188 K and activation energy (Delta E) was calculated which was in the range 0.634 eV-0.878 eV. Further linearization of thin film based NTC thermistors was carried out using an low cost analog circuit by adding parallel (R-P), series resistance (R-S) and operational amplifier (OP-AMP). It has been observed that these thin film based temperature sensors have repeatable temperature sensing behavior on linearization with high sensitivity and low power dissipation (P-diss)2015 (C) Elsevier B.V. All rights reserved.

In a systematic study to compare the effects of the values of burning rate and pressure exponent in RDX-AP based composite propellant, various compositions with varying percentages of zirconium carbide (ZrC) and zirconium silicate (ZrSiO4) were formulated to select a suitable candidate. Various rocket parameters of each formulation were theoretically predicted by the NASA CEC-71 program and the burning rate was evaluated in pressure range of 3-11MPa. In addition, density, sensitivity, and thermal properties of compositions having maximum effects on pressure exponent's values were also evaluated. It was concluded that ZrSiO4 enhances the pressure exponent n value substantially, whereas ZrC doesn't have significant effects on it as compared to base composition and also provides higher density values of composite propellant formulated.

Flexible and conformable Hydrochloric acid/Camphor sulphonic acid doped thin film of poly-o-toluidine-Mn3O4 nanocomposites has been fabricated on fire retardant glass cloth substrate. These films were found to have RT-NTC characteristics in the temperature range of 30–185 °C. The thermistor cut off has been found in the temperature range of 140–185 ± 5 °C depending upon the type of dopant. The material has been characterized using FT-IR, XRD, TEM for structure and morphology and TGA/DTA/DTG for thermal stability. Thermistor constant (β) obtained from RT characteristics are in the range of 6,210–8,080 K and 6,736–8,824 K for HCl doped and CSA doped thin films respectively. The activation energies (ΔE) are obtained in the range 0.535–0.697 eV for HCl doped and 0.580–0.760 eV for CSA doped thin films. Further the linearization of thin film based NTC thermistors was carried out by using low cost analog circuit. The same can be evaluated for point and surface temperature sensing in gloves for prosthetic hands.

This paper reports cure kinetics of poly nitratomethyl oxetane (PLN) with different isocyanates like isophorane di-isocyanate (IPDI) and hexamethylene di-isocyanate (HMDI). Reactions were monitored by differential scanning calorimetry (DSC) in the presence of two different cure catalysts namely di butyl tin di laurate (DBTDL) and ferric tris acetyl acetonate (FeAA) and their effect on the cure reaction was studied. Cure kinetics was evaluated using the multiple heating rate Ozawa method. The reactivity of two isocyanates and catalytic efficiencies were determined based on DSC reaction temperature, activation energy, and rate constants. Based on cure temperatures, FeAA catalyzed reactions have lower cure temperature than DBTDL catalyzed reactions, inferring that FeAA is a more active catalyst for PLN cure reactions. Rate constants (k) of FeAA catalyzed PLN cure reactions were higher than of DBTDL catalyzed reactions. The values of activation energies (Ea), pre-exponential factor, and rate constant also support the same trend. Completion of the curing process was monitored with the help of Fourier transform infrared. Viscosity buildup was measured with the help of rheometer by taking curing profiles for each system at 30 degrees C and it followed the similar trend as determined by DSC.

This paper report on a Butacene (R) based composite propellant with high burning rate. The effect of replacing HTPB with Butacene (R) on the physical, mechanical and ballistic properties, and sensitivity towards impact and friction, has been studied. The ballistic properties were evaluated as burning rates at various pressures (7-11 MPa), pressure exponents, ignition temperatures etc. As expected, a remarkable enhancement in burning rate at low pressures was observed with increasing percentage of Butacene (R). Comparatively lower n-values were observed for compositions containing Butacene (R) than for HTPB based propellants. The sensitivity of Butacene (R) based compositions, in terms of impact and friction, was found to be increased with an increasing percentage of Butacene (R).

Polymer nanocomposites are now a days an area of increasing scientific as well as technical interest. The addition of variable percents of nano sized materials creates change in their property (ies). Polymer nanocomposites exhibit superior properties as compared to micro- or macrocomposites. The improved combinations of electrical, mechanical and thermal properties of nanocomposites have resulted in major interest in various electronic applications. Polymer nanocomposites can be synthesized for various applications by proper selection of matrix, nano reinforcement material, synthesis method and surface modification of either the reinforcement or polymer (if required). Many polymer nanocomposites based products have been commercialized. This chapter has tried to highlight various types of polymer nanocomposites, their unique properties, various electronic applications for sensors with some specific examples. Though it is not a comprehensive one, this chapter could give a basic idea about polymer nanocomposites for sensor technology to a beginner.