The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Michael R. Zachariah - One of the best experts on this subject based on the ideXlab platform.
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Ignition of Nanoscale Titanium/Potassium Perchlorate Pyrotechnic Powder: Reaction Mechanism Study
2018Co-Authors: Miles C. Rehwoldt, Yong Yang, Haiyang Wang, Scott Holdren, Michael R. ZachariahAbstract:The reaction mechanism and ignition characteristics of the pyrotechnic composite of titanium nanoparticles and micron-sized potassium perchlorate was investigated under Rapid Heating conditions (∼5 × 105 K/s) by temperature jump (T-Jump) time-of-flight mass spectrometry. X-ray photoelectron spectroscopy surface analysis and transmission electron microscopy (TEM) characterization of titanium nanoparticles show a reactive oxide layer (∼6 nm) composed of amorphous TiO2 and roughly 20% crystalline TiN and titanium oxynitride. The T-Jump and thermogravimetric analysis reveals the oxide layer to be responsible for catalysis of oxygen release from KClO4, resulting in ignition temperatures as low as 720 K in atmospheric pressure argon. Fast and slow in situ Heating TEM corroborate the findings of oxygen atmosphere ignition characteristics, which illustrate KClO4 melting and coating of titanium nanoparticles immediately before oxidizer decomposition and titanium oxidation. Unlike aluminum, which has been shown to have a Rapid loss of surface area before combustion as a result of sintering, Ti retained its high surface area. A combination of a reactive shell and the preservation of titanium nanostructure under Rapid Heating may lead to enhanced oxygen diffusion and increased potential for transient energy release
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ignition of nanoscale titanium potassium perchlorate pyrotechnic powder reaction mechanism study c
The Journal of Physical Chemistry, 2018Co-Authors: Miles C. Rehwoldt, Yong Yang, Haiyang Wang, Scott Holdren, Michael R. ZachariahAbstract:The reaction mechanism and ignition characteristics of the pyrotechnic composite of titanium nanoparticles and micron-sized potassium perchlorate was investigated under Rapid Heating conditions (∼5 × 10⁵ K/s) by temperature jump (T-Jump) time-of-flight mass spectrometry. X-ray photoelectron spectroscopy surface analysis and transmission electron microscopy (TEM) characterization of titanium nanoparticles show a reactive oxide layer (∼6 nm) composed of amorphous TiO₂ and roughly 20% crystalline TiN and titanium oxynitride. The T-Jump and thermogravimetric analysis reveals the oxide layer to be responsible for catalysis of oxygen release from KClO₄, resulting in ignition temperatures as low as 720 K in atmospheric pressure argon. Fast and slow in situ Heating TEM corroborate the findings of oxygen atmosphere ignition characteristics, which illustrate KClO₄ melting and coating of titanium nanoparticles immediately before oxidizer decomposition and titanium oxidation. Unlike aluminum, which has been shown to have a Rapid loss of surface area before combustion as a result of sintering, Ti retained its high surface area. A combination of a reactive shell and the preservation of titanium nanostructure under Rapid Heating may lead to enhanced oxygen diffusion and increased potential for transient energy release.
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time resolved mass spectrometry of nano al and nano al cuo thermite under Rapid Heating a mechanistic study
Journal of Physical Chemistry C, 2012Co-Authors: Guoqiang Jian, Nicholas W Piekiel, Michael R. ZachariahAbstract:Aluminum nanoparticles (Al-NPs) and nano- Al/CuO thermite were investigated in a Rapid Heating environment by temperature jump time-of-flight mass spectrometry. Upon Rapid Heating (10 5 to 10 6 K/s), Al- containing vapor species (Al and Al2O) are observed to slowly increase with increasing temperature, followed by a Rapid increase in concentration at ∼2030 K. The temporal evolution of Al, Al2O species observed in time-resolved mass spectra of Rapid heated Al-NPs supports the hypothesis that Al containing species diffuse outward through the oxide shell under high Heating rate conditions. The Rapid rise in Al- containing species above 2030 K, which is below the bulk melting point of Al2O3, implies that the penetration of Al into the shell probably decreases its melting point. The measurements lead to an effective overall diffusion coefficient of ∼10 −10 cm 2 / s. Time-resolved mass spectra of nano-Al/CuO thermite show for the first time the existence of Al, Al2O, AlO, and Al2O2 intermediate reaction products, with Al2O the main intermediate oxidation product, in agreement with thermochemical calculations.
Yanjin Guan - One of the best experts on this subject based on the ideXlab platform.
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optimal design of Heating channels for Rapid Heating cycle injection mold based on response surface and genetic algorithm
Materials & Design, 2009Co-Authors: Xiping Li, Yanjin Guan, Guoqun ZhaoAbstract:Rapid Heating cycle molding (RHCM) technology is a novel polymer injection molding method developed in recent years. In this paper, the principle of RHCM was introduced and a RHCM mold for producing a large-size LCD TV panel was presented. Aiming at achieving a uniform temperature distribution on the cavity surface of the stationary mold insert, the distances between the neighbor Heating channels were considered as the main design variables. An objective function for optimizing the temperature distribution uniformity was proposed. The experiment samples for calculating the objective function were selected by using the Latin Hypercube Design experiment method. A quadric response surface equation for calculating temperature distribution uniformity was established. The design variables were optimized by using genetic algorithm and the optimal solutions were obtained. The temperature distribution uniformity on the stationary mold insert cavity surface was greatly improved. The effectiveness of the optimization method presented in this paper was also demonstrated by industrial injection production of a LCD TV panel.
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research on thermal stress deformation and fatigue lifetime of the Rapid Heating cycle injection mold
The International Journal of Advanced Manufacturing Technology, 2009Co-Authors: Xiping Li, Yanjin Guan, Guoqun Zhao, Huiping LiAbstract:Rapid Heating cycle molding (RHCM) is a novel plastic injection molding process. It can be used effectively to prevent many defects of products produced in conventional injection molding process. In this paper, the panel of large-size liquid crystal display TV was taken as an example. Thermal, deformation, and fatigue analysis models for RHCM injection mold were established. Firstly, by analyzing the heat transfer process of the RHCM mold, the temperature distributions on the mold cavity surface were studied. Secondly, through numerical simulation, the tendency of the stress and deformation of the RHCM mold was obtained. It showed that the fixing mode between the stationary mold insert and the stationary mold plate had a great influence on the thermal stress and deformation of the mold. As a result, a new fixing mode for the stationary mold insert was proposed which could effectively decrease the deformation caused by the temperature changing. Lastly, the lifetime of the mold under different fixing modes was evaluated, and reasonable suggestions which could improve the lifetime of RHCM mold were also proposed. Application in engineering proved that it was a very effective way to improve the lifetime of RHCM mold by using the suggested fixing mode.
Bruno C De Cooman - One of the best experts on this subject based on the ideXlab platform.
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direct resistance joule Heating of al 10 pct si coated press hardening steel
Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2016Co-Authors: Won Seok Choi, Bruno C De CoomanAbstract:Various Rapid Heating methods have been developed to increase the productivity of press hardening steel. One of these methods is direct resistance Joule Heating. This Heating method results in the melting of the surface coating and the formation of a persistent liquid trail as a result of the high thermal conductivity and low melting temperature of the Al-10 pct Si alloy coating. This can be addressed by an alloying preHeating treatment prior to the press hardening process.
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microstructure evolution of a 55 wt al zn coating on press hardening steel during Rapid Heating
Surface & Coatings Technology, 2015Co-Authors: Changwook Lee, Won Seok Choi, Yeol Rae Cho, Bruno C De CoomanAbstract:Abstract The surface alloying of 55 wt.% Al–Zn coated press hardening steel during a press hardening heat treatment was evaluated. Austenitization resulted in the formation of a surface layer containing FeAl and Fe2Al5. The use of an increased Heating rate during the austenitization cycle resulted in a high volume fraction of Zn at FeAl grain boundaries, and the presence of Zn islands in Fe2Al5 grains. These microstructural features suppressed the high temperature oxidation and evaporation of Zn. Zn was found to provide a pronounced cathodic protection, and the alloyed coating did not cause liquid metal induced embrittlement.
Won Seok Choi - One of the best experts on this subject based on the ideXlab platform.
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direct resistance joule Heating of al 10 pct si coated press hardening steel
Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2016Co-Authors: Won Seok Choi, Bruno C De CoomanAbstract:Various Rapid Heating methods have been developed to increase the productivity of press hardening steel. One of these methods is direct resistance Joule Heating. This Heating method results in the melting of the surface coating and the formation of a persistent liquid trail as a result of the high thermal conductivity and low melting temperature of the Al-10 pct Si alloy coating. This can be addressed by an alloying preHeating treatment prior to the press hardening process.
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microstructure evolution of a 55 wt al zn coating on press hardening steel during Rapid Heating
Surface & Coatings Technology, 2015Co-Authors: Changwook Lee, Won Seok Choi, Yeol Rae Cho, Bruno C De CoomanAbstract:Abstract The surface alloying of 55 wt.% Al–Zn coated press hardening steel during a press hardening heat treatment was evaluated. Austenitization resulted in the formation of a surface layer containing FeAl and Fe2Al5. The use of an increased Heating rate during the austenitization cycle resulted in a high volume fraction of Zn at FeAl grain boundaries, and the presence of Zn islands in Fe2Al5 grains. These microstructural features suppressed the high temperature oxidation and evaporation of Zn. Zn was found to provide a pronounced cathodic protection, and the alloyed coating did not cause liquid metal induced embrittlement.
Miles C. Rehwoldt - One of the best experts on this subject based on the ideXlab platform.
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Ignition of Nanoscale Titanium/Potassium Perchlorate Pyrotechnic Powder: Reaction Mechanism Study
2018Co-Authors: Miles C. Rehwoldt, Yong Yang, Haiyang Wang, Scott Holdren, Michael R. ZachariahAbstract:The reaction mechanism and ignition characteristics of the pyrotechnic composite of titanium nanoparticles and micron-sized potassium perchlorate was investigated under Rapid Heating conditions (∼5 × 105 K/s) by temperature jump (T-Jump) time-of-flight mass spectrometry. X-ray photoelectron spectroscopy surface analysis and transmission electron microscopy (TEM) characterization of titanium nanoparticles show a reactive oxide layer (∼6 nm) composed of amorphous TiO2 and roughly 20% crystalline TiN and titanium oxynitride. The T-Jump and thermogravimetric analysis reveals the oxide layer to be responsible for catalysis of oxygen release from KClO4, resulting in ignition temperatures as low as 720 K in atmospheric pressure argon. Fast and slow in situ Heating TEM corroborate the findings of oxygen atmosphere ignition characteristics, which illustrate KClO4 melting and coating of titanium nanoparticles immediately before oxidizer decomposition and titanium oxidation. Unlike aluminum, which has been shown to have a Rapid loss of surface area before combustion as a result of sintering, Ti retained its high surface area. A combination of a reactive shell and the preservation of titanium nanostructure under Rapid Heating may lead to enhanced oxygen diffusion and increased potential for transient energy release
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ignition of nanoscale titanium potassium perchlorate pyrotechnic powder reaction mechanism study c
The Journal of Physical Chemistry, 2018Co-Authors: Miles C. Rehwoldt, Yong Yang, Haiyang Wang, Scott Holdren, Michael R. ZachariahAbstract:The reaction mechanism and ignition characteristics of the pyrotechnic composite of titanium nanoparticles and micron-sized potassium perchlorate was investigated under Rapid Heating conditions (∼5 × 10⁵ K/s) by temperature jump (T-Jump) time-of-flight mass spectrometry. X-ray photoelectron spectroscopy surface analysis and transmission electron microscopy (TEM) characterization of titanium nanoparticles show a reactive oxide layer (∼6 nm) composed of amorphous TiO₂ and roughly 20% crystalline TiN and titanium oxynitride. The T-Jump and thermogravimetric analysis reveals the oxide layer to be responsible for catalysis of oxygen release from KClO₄, resulting in ignition temperatures as low as 720 K in atmospheric pressure argon. Fast and slow in situ Heating TEM corroborate the findings of oxygen atmosphere ignition characteristics, which illustrate KClO₄ melting and coating of titanium nanoparticles immediately before oxidizer decomposition and titanium oxidation. Unlike aluminum, which has been shown to have a Rapid loss of surface area before combustion as a result of sintering, Ti retained its high surface area. A combination of a reactive shell and the preservation of titanium nanostructure under Rapid Heating may lead to enhanced oxygen diffusion and increased potential for transient energy release.
