The Experts below are selected from a list of 447 Experts worldwide ranked by ideXlab platform
Xiaolin Zheng - One of the best experts on this subject based on the ideXlab platform.
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experimental effective metal oxides to enhance boron combustion
Combustion and Flame, 2019Co-Authors: Sidi Huang, Sili Deng, Yue Jiang, Xiaolin ZhengAbstract:Abstract Thermite reactions between metal fuels and oxide oxidizers are highly exothermic and self-sustaining, so they find wide applications in the explosion, pyrotechnics, thermal batteries, micro-actuator, and material synthesis and process. Compared to the well-studied aluminum (Al)-based Thermites, boron (B)-based Thermites are thermodynamically attractive due to boron's higher volumetric and gravimetric energy densities and they received limited attention. Previous studies have compared the effect of metal oxide on the reaction onset temperature of B-based Thermites and identified that B/Bi2O3 and B/CuO Thermites have lower reaction onset temperatures than other B/metal oxides. Nevertheless, there is no systematic study on the effect of metal oxide on both ignition and combustion of B-based thermite. In addition, no study has investigated the effect of binary metal oxide mixtures for B-based thermite. Herein, we experimentally tested five common metal oxides (CuO, Bi2O3, MoO3, Co3O4, and Fe2O3) on the ignition and combustion characteristics of sub-micron sized B particles using Xenon flash ignition, constant-volume pressure vessel and bomb calorimeter experiments. We observed that Bi2O3 and CuO are the most effective oxidizer for ignition and combustion of boron, respectively. We further identified that the binary oxide mixture (75 wt% B–CuO + 25 wt% B–Bi2O3) is more effective than all the single metal oxide for the ignition and combustion of boron particles. The results suggest that mixed oxides are potentially beneficial for ignition and combustion of other metal fuels as well.
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tuning the morphological ignition and combustion properties of micron al cuo Thermites through different synthesis approaches
Combustion and Flame, 2018Co-Authors: Sili Deng, Yue Jiang, Sidi Huang, Xinjian Shi, Jiheng Zhao, Xiaolin ZhengAbstract:Abstract Aluminum (Al)-based thermite, due to its high energy density and low cost, has found wide applications in aerospace propulsion, explosion, pyrotechnics, thermal batteries, and power generations. Though significant efforts have been devoted to improving the ignition and combustion performance of Al-based Thermites by using nano-Al, micron-Al (m-Al) remains of practical importance over nano-Al due to its lower cost and smaller dead mass. For m-Al based thermite, the main approach to improve its ignition and combustion performance is to bring Al and metal oxide as close as possible to facilitate the oxidizer diffusion process. Herein, we demonstrated two simple synthesis methods, i.e., the precipitation (PC) method and displacement (DP) method, to prepare m-Al/CuO Thermites with the intention to bring Al and CuO to shorter diffusion distance and achieve better dispersion. The PC-Thermites have flocculent nanostructured CuO closely attached to the surface of m-Al, and the DP-Thermites have a dense shell of CuO coated on the surface of m-Al. Both PC- and DP-Thermites have reduced agglomeration and diffusion distance over the traditional mechanically mixed (MM)-Thermites that have randomly distributed and agglomerated CuO and m-Al. Consequently, both PC- and DP-Thermites exhibit shorter ignition delay time, lower reaction onset temperatures, higher heat release, larger pressure rise, and extended reactivity limits than MM-Thermites. Particularly, PC-Thermites, due to their flocculent structures, exhibit the shortest ignition delay time, lowest reaction onset temperature, and highest amount of heat release. Moreover, the superior ignition and combustion performance of PC- and DP-Thermites is more pronounced under high heating rates over low heating rates. Similar PC and DP methods are applicable to prepare diverse Thermites with reduced diffusion distance and improved dispersion to improve their ignition and combustion properties.
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electroless deposition and ignition properties of si fe2o3 core shell nanoThermites
ACS omega, 2017Co-Authors: Sidi Huang, Sili Deng, Yue Jiang, Jiheng Zhao, Xiaolin ZhengAbstract:Thermite, a composite of metal and metal oxide, finds wide applications in power and thermal generation systems that require high-energy density. Most of the researches on Thermites have focused on using aluminum (Al) particles as the fuel. However, Al particles are sensitive to electrostatic discharge, friction, and mechanical impact, imposing a challenge for the safe handling and storage of Al-based Thermites. Silicon (Si) is another attractive fuel for Thermites because of its high-energy content, thin native oxide layer, and facile surface functionality. Several studies showed that the combustion properties of Si-based Thermites are comparable to those of Al-based Thermites. However, little is known about the ignition properties of Si-based Thermites. In this work, we determined the reaction onset temperatures of mechanically mixed (MM) Si/Fe2O3 nanoThermites and Si/Fe2O3 core/shell (CS) nanoThermites using differential scanning calorimetry. The Si/Fe2O3 CS nanoThermites were prepared by an electroles...
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synthesis and ignition of energetic cuo al core shell nanowires
Proceedings of the Combustion Institute, 2011Co-Authors: Yuma Ohkura, Shihyu Liu, Pratap M Rao, Xiaolin ZhengAbstract:Abstract Energetic Thermites (mixtures of Al and metal oxides), due to their high energy densities, have broad applications in propulsion, thermal batteries, waste disposal, and power generation for micro systems. Reducing the sizes of Al and metal oxides down to the nanoscale has been shown to be effective in increasing their reaction rates and reducing their ignition delays. However, it remains a challenge to create mixtures of Al and metal oxides with nanoscale uniformity. Here we report synthesis and ignition studies on Thermites with a new nanostructure, i.e., CuO/Al core/shell nanowires (NWs). The CuO NW cores were synthesized by the thermal annealing of copper films and served as templates for the deposition of Al shells by subsequent sputtering. The advantage of such a core/shell NW structure is that CuO and Al are uniformly mixed at the nanoscale. The onset temperatures of the exothermic reaction of the core/shell NWs were similar to those of nanoparticle (NP)-based Thermites in terms of magnitude, insensitivity to equivalence ratios and sensitivity to heating rates. Moreover, the core/shell NW Thermites, compared to NP-based Thermites, exhibit greatly improved mixing uniformity and reduced activation energy for the thermite reaction.
William Edward Cloete - One of the best experts on this subject based on the ideXlab platform.
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Burn Rate of Calcium Sulfate Dihydrate-Aluminum Thermites.
ACS applied materials & interfaces, 2018Co-Authors: Desania R. Govender, Walter Wilhelm Focke, Shepherd Masimba Tichapondwa, William Edward CloeteAbstract:The energetics of cast calcium sulfate dihydrate–aluminum Thermites were investigated. The casts were prepared from water slurries with a solids content below 65 wt %. The base case thermite comprised 60 wt % calcium sulfate dihydrate as the oxidizer with 40 wt % aluminum as fuel. The heat of hydration of the base case was 83 ± 4 kJ·kg–1 (dihydrate basis) and the initial setting time was about 100 min. The compressive strength reached 2.9 ± 0.2 MPa after 3 days of drying in ambient air. The open air burn rate was 12.0 ± 1.6 mm· s–1 and a maximum surface temperature of 1370 ± 64 °C was recorded with a pyrometer. Bomb calorimetry indicated an energy output of 8.0 ± 1.1 MJ·kg–1, slightly lower than predicted by the Ekvi thermodynamic simulation. Substitution of 10 wt % of the oxidant with copper sulfate pentahydrate significantly decreased the initial setting time of the casts to less than 30 min but a secondary aluminum oxidation reaction commenced after 2 h. The density of the castings was varied by either...
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Burn Rate of Calcium Sulfate Dihydrate–Aluminum Thermites
2018Co-Authors: Desania R. Govender, Walter Wilhelm Focke, Shepherd Masimba Tichapondwa, William Edward CloeteAbstract:The energetics of cast calcium sulfate dihydrate–aluminum Thermites were investigated. The casts were prepared from water slurries with a solids content below 65 wt %. The base case thermite comprised 60 wt % calcium sulfate dihydrate as the oxidizer with 40 wt % aluminum as fuel. The heat of hydration of the base case was 83 ± 4 kJ·kg–1 (dihydrate basis) and the initial setting time was about 100 min. The compressive strength reached 2.9 ± 0.2 MPa after 3 days of drying in ambient air. The open air burn rate was 12.0 ± 1.6 mm· s–1 and a maximum surface temperature of 1370 ± 64 °C was recorded with a pyrometer. Bomb calorimetry indicated an energy output of 8.0 ± 1.1 MJ·kg–1, slightly lower than predicted by the Ekvi thermodynamic simulation. Substitution of 10 wt % of the oxidant with copper sulfate pentahydrate significantly decreased the initial setting time of the casts to less than 30 min but a secondary aluminum oxidation reaction commenced after 2 h. The density of the castings was varied by either adding hollow sodium borosilicate microspheres or by adding excess water during the casting process. The addition of the hollow glass microspheres caused a decrease in the burning rate. Dehydration of the casts by thermal treatments at either 155 or 200 °C led to significant increases in the burning rate
Edward L Dreizin - One of the best experts on this subject based on the ideXlab platform.
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effect of premilling al and cuo in acetonitrile on properties of al cuo Thermites prepared by arrested reactive milling
Combustion and Flame, 2020Co-Authors: Mehnaz Mursalat, Mirko Schoenitz, Edward L DreizinAbstract:Abstract Thermite powders with molar composition 8Al·3CuO were prepared in two stages by Arrested Reactive Milling (ARM). In the first stage, the starting materials Al and CuO were milled separately in acetonitrile. Composite powders were then prepared in the second milling stage with hexane as process control agent and in the four possible combinations of one, both, or neither starting material being premilled in acetonitrile. Composites were characterized for morphology, size distribution, surface area, and reactive properties at low heating rates (thermal analysis) and high heating rates (ignition). Whether or not CuO was premilled, dense composites formed without premilling of Al. If Al was premilled in acetonitrile, however, loose agglomerates of refined Al and CuO particles formed in the second milling stage. Premilling changed the low-temperature reactions leading to ignition in the 8Al·3CuO Thermites. These changes are attributed to increased porosity of the formed composites if aluminum is premilled with acetonitrile. It is shown that greater refinement and lower ignition temperatures are achievable using two-stage milling.
Sili Deng - One of the best experts on this subject based on the ideXlab platform.
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experimental effective metal oxides to enhance boron combustion
Combustion and Flame, 2019Co-Authors: Sidi Huang, Sili Deng, Yue Jiang, Xiaolin ZhengAbstract:Abstract Thermite reactions between metal fuels and oxide oxidizers are highly exothermic and self-sustaining, so they find wide applications in the explosion, pyrotechnics, thermal batteries, micro-actuator, and material synthesis and process. Compared to the well-studied aluminum (Al)-based Thermites, boron (B)-based Thermites are thermodynamically attractive due to boron's higher volumetric and gravimetric energy densities and they received limited attention. Previous studies have compared the effect of metal oxide on the reaction onset temperature of B-based Thermites and identified that B/Bi2O3 and B/CuO Thermites have lower reaction onset temperatures than other B/metal oxides. Nevertheless, there is no systematic study on the effect of metal oxide on both ignition and combustion of B-based thermite. In addition, no study has investigated the effect of binary metal oxide mixtures for B-based thermite. Herein, we experimentally tested five common metal oxides (CuO, Bi2O3, MoO3, Co3O4, and Fe2O3) on the ignition and combustion characteristics of sub-micron sized B particles using Xenon flash ignition, constant-volume pressure vessel and bomb calorimeter experiments. We observed that Bi2O3 and CuO are the most effective oxidizer for ignition and combustion of boron, respectively. We further identified that the binary oxide mixture (75 wt% B–CuO + 25 wt% B–Bi2O3) is more effective than all the single metal oxide for the ignition and combustion of boron particles. The results suggest that mixed oxides are potentially beneficial for ignition and combustion of other metal fuels as well.
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tuning the morphological ignition and combustion properties of micron al cuo Thermites through different synthesis approaches
Combustion and Flame, 2018Co-Authors: Sili Deng, Yue Jiang, Sidi Huang, Xinjian Shi, Jiheng Zhao, Xiaolin ZhengAbstract:Abstract Aluminum (Al)-based thermite, due to its high energy density and low cost, has found wide applications in aerospace propulsion, explosion, pyrotechnics, thermal batteries, and power generations. Though significant efforts have been devoted to improving the ignition and combustion performance of Al-based Thermites by using nano-Al, micron-Al (m-Al) remains of practical importance over nano-Al due to its lower cost and smaller dead mass. For m-Al based thermite, the main approach to improve its ignition and combustion performance is to bring Al and metal oxide as close as possible to facilitate the oxidizer diffusion process. Herein, we demonstrated two simple synthesis methods, i.e., the precipitation (PC) method and displacement (DP) method, to prepare m-Al/CuO Thermites with the intention to bring Al and CuO to shorter diffusion distance and achieve better dispersion. The PC-Thermites have flocculent nanostructured CuO closely attached to the surface of m-Al, and the DP-Thermites have a dense shell of CuO coated on the surface of m-Al. Both PC- and DP-Thermites have reduced agglomeration and diffusion distance over the traditional mechanically mixed (MM)-Thermites that have randomly distributed and agglomerated CuO and m-Al. Consequently, both PC- and DP-Thermites exhibit shorter ignition delay time, lower reaction onset temperatures, higher heat release, larger pressure rise, and extended reactivity limits than MM-Thermites. Particularly, PC-Thermites, due to their flocculent structures, exhibit the shortest ignition delay time, lowest reaction onset temperature, and highest amount of heat release. Moreover, the superior ignition and combustion performance of PC- and DP-Thermites is more pronounced under high heating rates over low heating rates. Similar PC and DP methods are applicable to prepare diverse Thermites with reduced diffusion distance and improved dispersion to improve their ignition and combustion properties.
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electroless deposition and ignition properties of si fe2o3 core shell nanoThermites
ACS omega, 2017Co-Authors: Sidi Huang, Sili Deng, Yue Jiang, Jiheng Zhao, Xiaolin ZhengAbstract:Thermite, a composite of metal and metal oxide, finds wide applications in power and thermal generation systems that require high-energy density. Most of the researches on Thermites have focused on using aluminum (Al) particles as the fuel. However, Al particles are sensitive to electrostatic discharge, friction, and mechanical impact, imposing a challenge for the safe handling and storage of Al-based Thermites. Silicon (Si) is another attractive fuel for Thermites because of its high-energy content, thin native oxide layer, and facile surface functionality. Several studies showed that the combustion properties of Si-based Thermites are comparable to those of Al-based Thermites. However, little is known about the ignition properties of Si-based Thermites. In this work, we determined the reaction onset temperatures of mechanically mixed (MM) Si/Fe2O3 nanoThermites and Si/Fe2O3 core/shell (CS) nanoThermites using differential scanning calorimetry. The Si/Fe2O3 CS nanoThermites were prepared by an electroles...
Desania R. Govender - One of the best experts on this subject based on the ideXlab platform.
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Burn Rate of Calcium Sulfate Dihydrate-Aluminum Thermites.
ACS applied materials & interfaces, 2018Co-Authors: Desania R. Govender, Walter Wilhelm Focke, Shepherd Masimba Tichapondwa, William Edward CloeteAbstract:The energetics of cast calcium sulfate dihydrate–aluminum Thermites were investigated. The casts were prepared from water slurries with a solids content below 65 wt %. The base case thermite comprised 60 wt % calcium sulfate dihydrate as the oxidizer with 40 wt % aluminum as fuel. The heat of hydration of the base case was 83 ± 4 kJ·kg–1 (dihydrate basis) and the initial setting time was about 100 min. The compressive strength reached 2.9 ± 0.2 MPa after 3 days of drying in ambient air. The open air burn rate was 12.0 ± 1.6 mm· s–1 and a maximum surface temperature of 1370 ± 64 °C was recorded with a pyrometer. Bomb calorimetry indicated an energy output of 8.0 ± 1.1 MJ·kg–1, slightly lower than predicted by the Ekvi thermodynamic simulation. Substitution of 10 wt % of the oxidant with copper sulfate pentahydrate significantly decreased the initial setting time of the casts to less than 30 min but a secondary aluminum oxidation reaction commenced after 2 h. The density of the castings was varied by either...
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Burn Rate of Calcium Sulfate Dihydrate–Aluminum Thermites
2018Co-Authors: Desania R. Govender, Walter Wilhelm Focke, Shepherd Masimba Tichapondwa, William Edward CloeteAbstract:The energetics of cast calcium sulfate dihydrate–aluminum Thermites were investigated. The casts were prepared from water slurries with a solids content below 65 wt %. The base case thermite comprised 60 wt % calcium sulfate dihydrate as the oxidizer with 40 wt % aluminum as fuel. The heat of hydration of the base case was 83 ± 4 kJ·kg–1 (dihydrate basis) and the initial setting time was about 100 min. The compressive strength reached 2.9 ± 0.2 MPa after 3 days of drying in ambient air. The open air burn rate was 12.0 ± 1.6 mm· s–1 and a maximum surface temperature of 1370 ± 64 °C was recorded with a pyrometer. Bomb calorimetry indicated an energy output of 8.0 ± 1.1 MJ·kg–1, slightly lower than predicted by the Ekvi thermodynamic simulation. Substitution of 10 wt % of the oxidant with copper sulfate pentahydrate significantly decreased the initial setting time of the casts to less than 30 min but a secondary aluminum oxidation reaction commenced after 2 h. The density of the castings was varied by either adding hollow sodium borosilicate microspheres or by adding excess water during the casting process. The addition of the hollow glass microspheres caused a decrease in the burning rate. Dehydration of the casts by thermal treatments at either 155 or 200 °C led to significant increases in the burning rate
