The Experts below are selected from a list of 1764 Experts worldwide ranked by ideXlab platform
Jack J. Yoh - One of the best experts on this subject based on the ideXlab platform.
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chemical kinetics of multi component Pyrotechnics and mechanistic deconvolution of variable activation energy
Proceedings of the Combustion Institute, 2019Co-Authors: Anirudha Ambekar, Jack J. YohAbstract:This study reports an experimental investigation into the chemical kinetics of several commercial pyrotechnic compositions. Differential Scanning Calorimetry (DSC) was utilized to elucidate the thermo-kinetic characteristics of four multicomponent pyrotechnic compositions. The combustion process of typical Pyrotechnics is primarily driven by condensed phase reactions including processes such as phase change, decomposition, and oxidation. The multicomponent nature of practical Pyrotechnics results in a particularly complex interaction between the components when heated. A thermo-kinetic study was performed to simulate the heating experienced by the Pyrotechnics before the combustion zone. The physical processes occurring within these temperature limits provide important insight into the overall combustion rate. The non-isothermal DSC experimental technique combined with isoconversional methods, such as Friedman and Starink methods were utilized to evaluate the apparent chemical kinetics parameters for these propellants. The observations from the DSC study and isoconversional kinetic analysis provided an insight into the phenomenology of the combustion process of Pyrotechnics. The problem of highly variable activation energy due to the presence of multiple reactions was addressed through a mechanistic deconvolution using nonlinear regression technique. The study confirmed the prominence of oxidizer decomposition on overall combustion reaction kinetics.
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kinetics deconvolution study of multi component Pyrotechnics
Thermochimica Acta, 2018Co-Authors: Anirudha Ambekar, Jack J. YohAbstract:Abstract This study reports an experimental investigation into the chemical kinetics of several commercial pyrotechnic compositions. A differential scanning calorimeter was utilized to elucidate the thermo-kinetic characteristics of five multicomponent pyrotechnic compositions. The multicomponent nature of practical Pyrotechnics results in a complex interaction between the various components as well as condensed phase reactions. The thermo-kinetic study was carried out to approximate the heating experienced by the Pyrotechnics before the combustion zone. The chemical kinetic parameters such as overall activation energy (Ea) and pre-exponential factor (A) corresponding to these reactions were estimated using Friedman and Starink method. The large variation in Ea attributed to multiple parallel reactions was addressed through the application of deconvolution techniques utilizing the Frazer-Suzuki function as well as nonlinear mechanistic modelling. The observations from the DSC data and the comparison between the deconvolution techniques provided an insight into the phenomenology of the combustion process of energetic Pyrotechnics.
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The hygrothermal aging effects of titanium hydride potassium perchlorate for pyrotechnic combustion
Thermochimica Acta, 2018Co-Authors: Anirudha Ambekar, Jack J. YohAbstract:Abstract Titanium hydride potassium perchlorate (THPP) is a well-known pyrotechnic initiator commonly utilized in the field of aerospace propulsion. The current study experimentally elucidates the effects of hygrothermal aging on the pyrotechnic combustion of THPP and proposes two methodologies for analysis. The first technique implements a two-step isoconversional method to analyse the hygrothermally aged THPP with Differential Scanning Calorimetry (DSC), and the second method offers a novel aging prediction methodology by comparing the experimental heat of reaction values against idealized equilibrium values. As the heat of reaction plays a major role on determining propellant’s performance, NASA Chemical Equilibrium with Applications (CEA) was used to predict its value. The knowledge of the combined aging effects is directly connected to the performance, lifetime, and safety of a pyrotechnic initiator that utilizes the THPP. The values of heat of reactions for different samples with different aging duration were estimated based on their composition extracted from the X-ray Photoelectron Spectroscopy (XPS) study.
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analysis on shock attenuation in gap test configuration for characterizing energetic materials
Journal of Applied Physics, 2016Co-Authors: Bohoon Kim, Jungsu Park, Jack J. YohAbstract:A pyrotechnic system consisting of donor/acceptor pair separated by a gap relies on shock attenuationcharacteristics of the gap material and shock sensitivity of the donor and the acceptor charges. Despite of its common use, a numerical study of such a pyrotechnic train configuration is seldom reported because proper modeling of the full process requires precise capturing of the shock wave attenuation in the gap prior to triggering a full detonation of a high explosive and accurate description of the high strain rate dynamics of the explosively loaded inert confinements. We apply a hybrid particle level-set based multimaterial hydrocode with reactive flow models for pentolite donor and heavily aluminized cyclotrimethylene-trinitramine as the acceptor charge. The complex shock interaction, a critical gap thickness, an acoustic impedance, and go/no-go characteristics of the pyrotechnic system are quantitatively investigated.
Thomas M Klapotke - One of the best experts on this subject based on the ideXlab platform.
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fine tuning advances in chlorine free blue light generating Pyrotechnics
European Journal of Inorganic Chemistry, 2020Co-Authors: Johann Gluck, Thomas M Klapotke, Teresa KublbockAbstract:One of the most challenging tasks in the field of light‐producing Pyrotechnics is the generation of saturated blue light with high spectral purity. Only copper salts in combination with chlorine seem to be high‐performing blue light emitters. However, in modern Pyrotechnics the application of chlorine should be avoided. Different strategies are presented to further fine‐tune literature‐known chlorine‐free blue‐light‐emitting pyrotechnical compositions. The copper iodate as well as the copper bromate systems have been studied by using small amounts of nitrogen‐rich compounds like 1,2,4‐triazole, 5‐amino‐1H‐tetrazole or 3‐nitro‐1H‐1,2,4‐triazole. To overcome sensitivity issues, a two‐component epoxy binder system was introduced. The application of both copper(I) iodide and copper(I) bromide in the same pyrotechnical formulation were considered as blue‐light‐emitting species. Further, a quite new approach by using copper(I) nitrogen‐rich coordination compounds was investigated to give a blue flame color. All relevant formulations were characterized with respect to their dominant wavelength and spectral purity as well as impact and friction sensitivity.
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a strontium and chlorine free pyrotechnic illuminant of high color purity
Angewandte Chemie, 2017Co-Authors: Johann Gluck, Jesse J Sabatini, Thomas M Klapotke, Magdalena Rusan, Jorg StierstorferAbstract:The development of a red-light-emitting pyrotechnic illuminant has garnered interest from the Pyrotechnics community owing to potential regulations by the United States Environmental Protection Agency (U.S. EPA) regarding the use of strontium and chlorinated organic materials. To address these environmental regulatory concerns, the development of lithium-based red-light-emitting pyrotechnic compositions of high purity and color quality is described. These formulations do not contain strontium or chlorinated organic materials. Rather, the disclosed formulations are based on a non-hygroscopic dilithium nitrogen-rich salt that serves as both oxidizer and red colorant. These formulations are likely to draw interest from the civilian fireworks and military Pyrotechnics communities for further development as they both have a vested interest in the development of environmentally conscious formulations.
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study of pyrotechnic blue strobe compositions based on ammonium perchlorate and tetramethylammonium nitrate
European Journal of Inorganic Chemistry, 2017Co-Authors: Dominykas Juknelevicius, Thomas M Klapotke, Magdalena Rusan, Alicia M W Dufter, Arunas RamanaviciusAbstract:Pyrotechnic strobes, both colorless and colorful, are compositions that burn in an oscillatory manner. They are used in military illumination devices and in fireworks as one of the most attractive pyrotechnic effects. Most colored strobes contain magnesium (Mg) or magnesium-aluminum (MgAl) alloy as a fuel. However, this is an issue for blue strobes since the choice of stable blue-flame emitters is extremely limited. In fact, copper halides have been observed to produce blue emissions in pyrotechnic flames exclusively at temperatures ranging from 1200 to 1500 degrees C. At higher temperatures, the emitter is destroyed, or more specifically, a preferred trimer Cu3Cl3 species is converted into monomers. As a result, the flame color fades and a whitish-blue flame is observed. Therefore, it was interesting to see whether blue pyrotechnic strobes can be made without using conventional high-temperature fuels, such as Mg or Al, in order to conserve a deep flame color. The formulation called the Jennings-White blue strobe No. 5 [55 % ammonium perchlorate (AP), 30 % tetramethylammonium nitrate (TMAN), and 15 % copper] is considered the top-of-the-line formulation, which is described as being capable of producing an intense blue strobe. However, its mechanism is not well-understood, and the formulation is not chemically compatible. This paper presents research focused on improving the blue strobe formulation by Jennings-White.
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copper i bromide an alternative emitter for blue colored flame Pyrotechnics
Chemistry: A European Journal, 2015Co-Authors: Thomas M Klapotke, Dominykas Juknelevicius, Eero Karvinen, Rytis Kubilius, Arunas Ramanavicius, Magdalena RusanAbstract:Copper(I) bromide was evaluated as an alternative emitter for blue flame pyrotechnic compositions. CuBr and CuCl emission spectra were recorded from a butane torch flame and compared. Cu(BrO3 )2 was synthesized and used in pyrotechnic compositions as an oxidizer and the source for the generation of CuBr species. Pyrotechnic compositions, which contained copper and potassium bromates as oxidizers, were optimized for the generation of blue flames. The experimental data, including emission spectra of the flames, chromaticity coordinates, burning rates, luminous intensities, and sensitivity tests, were analyzed and compared.
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high nitrogen based Pyrotechnics longer and brighter burning perchlorate free red light illuminants for military and civilian applications
Chemistry: A European Journal, 2012Co-Authors: Jesse J Sabatini, Reddy Damavarapu, Amita V Nagori, Gary Chen, Phillip Chu, Thomas M KlapotkeAbstract:The full-up prototype testing of perchlorate-free, hand-held, signal illuminants for the US Army's M126A1 red star parachute hand-held signal is described. Compared to the perchlorate-containing control, the disclosed illuminants yielded excellent stabilities toward various ignition stimuli while offering superior pyrotechnic performance. Militarily, the illuminants provided further evidence that development of smaller hand-held signal items in an environmentally conscious way is a realistic and obtainable goal. The results are also important from the perspective of civilian fireworks, as the development of brighter, longer-burning, and environmentally compatible red-light-emitting Pyrotechnics is now possible. Language: en
Trevor T Griffiths - One of the best experts on this subject based on the ideXlab platform.
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pyrotechnic and thermal studies on the magnesium strontium nitrate pyrotechnic system
Propellants Explosives Pyrotechnics, 2006Co-Authors: Irmeli M Tuukkanen, Edward L Charsley, James J Rooney, Trevor T Griffiths, Peter G Laye, Helge LemmetyinenAbstract:The pyrotechnic and thermal properties of a range of binary magnesium-strontium nitrate compositions containing from 10% to 90% by mass of magnesium have been determined. The burning rate and light output were measured after consolidating the compositions into cardboard tubes. The exothermicity, temperature of ignition and time to ignition of the compositions were also determined and the products of combustion were characterized
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studies on the ageing of a magnesium strontium nitrate pyrotechnic composition using isothermal microcalorimetry and thermal analysis techniques
Thermochimica Acta, 2004Co-Authors: Irmeli M Tuukkanen, S D Brown, Edward L Charsley, S J Goodall, James J Rooney, Trevor T Griffiths, Helge LemmetyinenAbstract:The ageing behaviour of a pyrotechnic composition containing equal parts by mass of magnesium and strontium nitrate has been followed by isothermal microcalorimetry. The measurements were carried out on the samples at 50 °C and 65% relative humidity in air using closed ampoules. The results have been compared to those obtained for magnesium powder under the same conditions. Following an initial induction period, the pyrotechnic compositions reacted at a much faster rate than magnesium powder alone. The main reaction products were found to be magnesium hydroxide and strontium nitrite; the amounts formed have been correlated with the cumulative heats of ageing. In addition, the influence of the ageing process on the pyrotechnic reaction has been studied by high temperature differential scanning calorimetry (DSC) and by modulated temperature DSC.
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studies on the ageing of a magnesium potassium nitrate pyrotechnic composition using isothermal heat flow calorimetry and thermal analysis techniques
Thermochimica Acta, 2003Co-Authors: S D Brown, Edward L Charsley, S J Goodall, James J Rooney, Peter G Laye, Trevor T GriffithsAbstract:The ageing behaviour of a pyrotechnic mixture of magnesium and potassium nitrate has been followed at 50 °C and 65% relative humidity by isothermal heat flow calorimetry. Measurements have been carried out with samples in air and in an inert atmosphere. The main reaction product was found to be magnesium hydroxide. This has been determined quantitatively by thermogravimetry and the amount formed correlated with the measured cumulative heat of ageing. The results have been compared with those obtained for magnesium powder studied under the same conditions. In addition the influence of the ageing process on the pyrotechnic reaction has been studied by high temperature differential scanning calorimetry under ignition conditions and modulated temperature differential scanning calorimetry.
Helge Lemmetyinen - One of the best experts on this subject based on the ideXlab platform.
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pyrotechnic and thermal studies on the magnesium strontium nitrate pyrotechnic system
Propellants Explosives Pyrotechnics, 2006Co-Authors: Irmeli M Tuukkanen, Edward L Charsley, James J Rooney, Trevor T Griffiths, Peter G Laye, Helge LemmetyinenAbstract:The pyrotechnic and thermal properties of a range of binary magnesium-strontium nitrate compositions containing from 10% to 90% by mass of magnesium have been determined. The burning rate and light output were measured after consolidating the compositions into cardboard tubes. The exothermicity, temperature of ignition and time to ignition of the compositions were also determined and the products of combustion were characterized
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studies on the ageing of a magnesium strontium nitrate pyrotechnic composition using isothermal microcalorimetry and thermal analysis techniques
Thermochimica Acta, 2004Co-Authors: Irmeli M Tuukkanen, S D Brown, Edward L Charsley, S J Goodall, James J Rooney, Trevor T Griffiths, Helge LemmetyinenAbstract:The ageing behaviour of a pyrotechnic composition containing equal parts by mass of magnesium and strontium nitrate has been followed by isothermal microcalorimetry. The measurements were carried out on the samples at 50 °C and 65% relative humidity in air using closed ampoules. The results have been compared to those obtained for magnesium powder under the same conditions. Following an initial induction period, the pyrotechnic compositions reacted at a much faster rate than magnesium powder alone. The main reaction products were found to be magnesium hydroxide and strontium nitrite; the amounts formed have been correlated with the cumulative heats of ageing. In addition, the influence of the ageing process on the pyrotechnic reaction has been studied by high temperature differential scanning calorimetry (DSC) and by modulated temperature DSC.
Anirudha Ambekar - One of the best experts on this subject based on the ideXlab platform.
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chemical kinetics of multi component Pyrotechnics and mechanistic deconvolution of variable activation energy
Proceedings of the Combustion Institute, 2019Co-Authors: Anirudha Ambekar, Jack J. YohAbstract:This study reports an experimental investigation into the chemical kinetics of several commercial pyrotechnic compositions. Differential Scanning Calorimetry (DSC) was utilized to elucidate the thermo-kinetic characteristics of four multicomponent pyrotechnic compositions. The combustion process of typical Pyrotechnics is primarily driven by condensed phase reactions including processes such as phase change, decomposition, and oxidation. The multicomponent nature of practical Pyrotechnics results in a particularly complex interaction between the components when heated. A thermo-kinetic study was performed to simulate the heating experienced by the Pyrotechnics before the combustion zone. The physical processes occurring within these temperature limits provide important insight into the overall combustion rate. The non-isothermal DSC experimental technique combined with isoconversional methods, such as Friedman and Starink methods were utilized to evaluate the apparent chemical kinetics parameters for these propellants. The observations from the DSC study and isoconversional kinetic analysis provided an insight into the phenomenology of the combustion process of Pyrotechnics. The problem of highly variable activation energy due to the presence of multiple reactions was addressed through a mechanistic deconvolution using nonlinear regression technique. The study confirmed the prominence of oxidizer decomposition on overall combustion reaction kinetics.
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kinetics deconvolution study of multi component Pyrotechnics
Thermochimica Acta, 2018Co-Authors: Anirudha Ambekar, Jack J. YohAbstract:Abstract This study reports an experimental investigation into the chemical kinetics of several commercial pyrotechnic compositions. A differential scanning calorimeter was utilized to elucidate the thermo-kinetic characteristics of five multicomponent pyrotechnic compositions. The multicomponent nature of practical Pyrotechnics results in a complex interaction between the various components as well as condensed phase reactions. The thermo-kinetic study was carried out to approximate the heating experienced by the Pyrotechnics before the combustion zone. The chemical kinetic parameters such as overall activation energy (Ea) and pre-exponential factor (A) corresponding to these reactions were estimated using Friedman and Starink method. The large variation in Ea attributed to multiple parallel reactions was addressed through the application of deconvolution techniques utilizing the Frazer-Suzuki function as well as nonlinear mechanistic modelling. The observations from the DSC data and the comparison between the deconvolution techniques provided an insight into the phenomenology of the combustion process of energetic Pyrotechnics.
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The hygrothermal aging effects of titanium hydride potassium perchlorate for pyrotechnic combustion
Thermochimica Acta, 2018Co-Authors: Anirudha Ambekar, Jack J. YohAbstract:Abstract Titanium hydride potassium perchlorate (THPP) is a well-known pyrotechnic initiator commonly utilized in the field of aerospace propulsion. The current study experimentally elucidates the effects of hygrothermal aging on the pyrotechnic combustion of THPP and proposes two methodologies for analysis. The first technique implements a two-step isoconversional method to analyse the hygrothermally aged THPP with Differential Scanning Calorimetry (DSC), and the second method offers a novel aging prediction methodology by comparing the experimental heat of reaction values against idealized equilibrium values. As the heat of reaction plays a major role on determining propellant’s performance, NASA Chemical Equilibrium with Applications (CEA) was used to predict its value. The knowledge of the combined aging effects is directly connected to the performance, lifetime, and safety of a pyrotechnic initiator that utilizes the THPP. The values of heat of reactions for different samples with different aging duration were estimated based on their composition extracted from the X-ray Photoelectron Spectroscopy (XPS) study.
