Imaging the combustion characteristics of Al, B, and Ti composites

Wang, Yujie; Hagen, Erik; Biswas, Prithwish; Wang, Haiyang; Zachariah, Michael R.

doi:10.1016/j.combustflame.2023.112747

Cited by 17 publications

(14 citation statements)

References 47 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For the composite with bare Al, main body of the droplets have an average temperature of ∼2350 K, which is significantly higher than the melting point of Al at 930 K. It is noteworthy that this measured temperature is approximately equal to the melting point of Al 2 O 3 at 2345 K. 37 At this temperature Al 2 O 3 melts and retracts, forming a distinct lobe due to surface tension. 16,47 With the introduction of Si to the composite, the average temperature of the main body of the droplets is ∼2450 K for 90% Al−10% Si and ∼2500 K for 75% Al−25% Si, respectively. The droplet temperature difference between bare Al and 75% Al−25% Si is within the uncertainty of the measurement (200−300 K), 27,31 therefore we conclude that the addition of Si has minimal effect on the droplet temperature.…”

Section: Resultsmentioning

confidence: 99%

“…Cone-shaped flame front is observed for all three composites and is attributed to a higher porosity on the edge of the composites that arises from a higher solvent evaporation rate during printing. 16 For the composite of bare Al, molten droplets with dark caps form on the burning surface. The main (bright) body of these droplets is almost pure Al while the dark cap consists of Al 2 O 3 .…”

Section: Resultsmentioning

confidence: 99%

“…10−15 However, agglomeration becomes prevalent with the replacement of micron scale Al with nanoscale Al. 16,17 This is because of the tendency of Al nanoparticles to aggregate, sinter, and coalesce due to either solid state diffusion or viscous flow. 1,18 The agglomeration mitigates the advantages of utilizing Al nanoparticles and decreases the energy release rate.…”

Section: Introductionmentioning

confidence: 99%

“…35−38 Here we employ high-speed microscopic imaging to study the reaction front and postflame with high temporal (μs) and spatial (μm) resolution. 16,24,39 This enables us to track the agglomerate size and surface residence time to provide information about the evolution process of agglomerates. Three-color imaging pyrometry is used to measure the temperature of the agglomerates.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Role of Surface Tension on Heat Feedback and Power from Energetic Composites

Wang,

Xu,

Issac Paul

et al. 2024

ACS Appl. Mater. Interfaces

Self Cite

View full text Add to dashboard Cite

Heat feedback to the unburned reaction interface is an important controlling factor of the velocity of the reaction front and power delivery. In this paper, we investigate the effect of agglomerate surface tension and its relationship to surface residence time and heat feedback on the combustion characteristics by Si addition to an Al/KClO 4 composite. Macroscopic imaging demonstrates a significant increase in burn rate with the addition of Si despite the fact that Si/ KClO 4 has a slightly lower energy density than Al/KClO 4 . Microscopic imaging coupled with three-color pyrometry reveals that molten liquid forms and evolves into spherical droplets on the burning surface, which are subsequently ejected from the surface. We find that the addition of Si results in a small increase in droplet size and a negligible impact on droplet temperature. However, the droplet formation rate on the surface is slower, leading to a significantly longer surface residence time. This leads to enhanced conductive heat feedback to the unburnt materials, thereby increasing the burn rate and energy release rate. We attribute the decreased droplet growth rate to the lowered surface tension of the liquid mixture with Si addition. This study highlights the crucial role of agglomerate physical property (e.g., surface tension) in influencing the combustion behavior of energetic composites.

show abstract

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Role of Surface Tension on Heat Feedback and Power from Energetic Composites

Wang,

Xu,

Issac Paul

et al. 2024

ACS Appl. Mater. Interfaces

Self Cite

View full text Add to dashboard Cite

show abstract

“…Both experimental and theoretical studies suggest that boron possesses an extremely high volumetric heat value (137.45 kJ/cm 3 ) and gravimetric heat value (58.74 kJ/g) among metal fuels (such as Mg, Li, Al, Zr, etc.). The volumetric heat value is 1.9 times that of Al, and the gravimetric heat value is 1.6 times that of Al. − Consequently, boron has emerged as one of the most promising metal fuel additives in propellants and explosives. − Despite this, the application of boron is not as extensive as Al. − The most important factor is the pre-existing boron oxide (B 2 O 3 ) layer with 2–5 nm thickness that forms on the surface of boron powder . This coating leads to compatibility issues with commonly used binder components in propellant formulas, specifically hydroxy-terminated polybutadiene (HTPB). , Furthermore, the low melting point (450 °C) of B 2 O 3 leads to the formation of a viscous liquid during combustion, hindering the transfer of oxygen to inner boron.…”

Section: Introductionmentioning

confidence: 99%

Synergistic Enhancement on Ignition and Combustion Properties of Boron via Viton Core–Shell Coating

Liu,

Wang,

Zhao

et al. 2024

Langmuir

View full text Add to dashboard Cite

The high gravimetric (58.74 kJ/g) and volumetric (137.45 kJ/cm3) heat values loaded in boron (B) offer significant potential for application in solid propellants and explosives. However, the high melting (2076 °C) and boiling (3927 °C) points of boron powder and the low melting point (450 °C) of oxidation products affect the energy performance and application of boron. Fluorine-containing polymers have high oxidation potential and excellent mechanical properties and can produce expectant gaseous products through the combustion reaction with boron oxide, but research examining the interaction between purified boron powder and fluoropolymers and the optimal selection of the fluoropolymer remains scarce. Herein, the binding energy between typical fluoropolymers [Viton, polyvinylidene fluoride, poly(vinylidene fluoride-co-chlorotrifluoroethylene), and vinylidene fluoride] and boron was calculated via molecular dynamics simulations, which shows that Viton is an appropriate candidate for coating boron powder. In the experiment, The Bw@Viton core–shell composites were prepared using Viton as the coating layer, and boron powder was pre-purified with acetonitrile. Its structure, thermal properties, ignition, and combustion characteristics were then characterized. The results revealed successful removal of the oxide layer, and the hydrophobicity was significantly improved after Viton coating. Purification and coating synergistically enhance the energy release of boron powder, and the composites demonstrated excellent thermal, ignition, and combustion performances. In particular, the heat of oxidation and heat of combustion were increased by 26.6 and 32.7%, respectively. The ignition delay time was reduced by 53.2% compared to raw boron. A prospective reaction mechanism between boron and Viton is thus proposed.

show abstract

Oscillating‐to‐Continuous Combustion Transition in Mesoparticle Composites Through Manipulation of Heat Feedback

Wang,

Chowdhury,

Zhou

et al. 2024

Adv Funct Materials

View full text Add to dashboard Cite

In this study, free‐standing composites consisting of 90 wt% nanoenergetic mesoparticles are fabricated and their combustion characteristics are investigated. The findings reveal that the integrity of the mesoparticles remains intact during the printing process and a reduction in sintering is observed for the composite of mesoparticles compared to the physical mixture. However, the composite of mesoparticles exhibits noncontinuous and oscillating propagation behavior at a steady frequency of ≈5 Hz. This is attributed to insufficient heat feedback from the flame to the unburnt material. To address this issue, carbon fiber (C.F.) is introduced into the composite to enhance heat feedback to the reaction front by intercepting hot agglomerates near the burning surface. Incorporating C.F. leads to steady propagation of the composite. Agglomerate residence time and characteristic heat transfer time analysis near the burning surface indicate that while the composite without C.F. has agglomerate residence time on the same order of magnitude as the characteristic heat transfer time, the composite with C.F. has significantly increased overall agglomerate residence time compared to the characteristic heat transfer time. This confirms the enhanced heat feedback through C.F. inclusion. This study demonstrates the crucial role of heat feedback in the combustion behavior of energetic composites.

show abstract

Imaging the combustion characteristics of Al, B, and Ti composites

Cited by 17 publications

References 47 publications

Role of Surface Tension on Heat Feedback and Power from Energetic Composites

Role of Surface Tension on Heat Feedback and Power from Energetic Composites

Synergistic Enhancement on Ignition and Combustion Properties of Boron via Viton Core–Shell Coating

Oscillating‐to‐Continuous Combustion Transition in Mesoparticle Composites Through Manipulation of Heat Feedback

Contact Info

Product

Resources

About