Browsing by Author "Pantoya, Michelle (TTU)"
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Item Fireball symmetry and its influence on perspective error from thermography data(2024) Cagle, Colton (TTU); Pantoya, Michelle (TTU)Thermography uses high-speed color cameras to perform two-color pyrometry for measuring spatially resolved surface temperatures of condensed phases. One application is to investigate the thermal evolution of particles within fireballs, but data analysis is affected by emissivity and optical density. Fireball dynamics exhibit large variations in both properties across space and time, while diagnostics measure the line-of-sight radius of a maturing fireball, raising the question: does thermography accurately represent temperature distributions regardless of spatial perspective? Here, fireballs are observed at two 90° perspectives. Every frame of data is categorized based on symmetry, then compared using the median temperature difference. Symmetric flame profiles show higher congruity in global median temperature, whereas asymmetric flames produce varying optical density profiles leading to larger differences between perspectives. Methods to correct perspective errors are discussed.Item Pre-stressing micron-scale aluminum core-shell particles to improve reactivity(2015) Levitas, Valery I.; McCollum, Jena (TTU); Pantoya, Michelle (TTU)The main direction in increasing reactivity of aluminum (Al) particles for energetic applications is reduction in their size down to nanoscale. However, Al nanoparticles are 30-50 times more expensive than micron scale particles and possess safety and environmental issues. Here, we improved reactivity of Al micron scale particles by synthesizing pre-stressed core-shell structures. Al particles were annealed and quenched to induce compressive stresses in the alumina passivation shell surrounding Al core. This thermal treatment was designed based on predictions of the melt-dispersion mechanism (MDM); a theory describing Al particle reaction under high heating rate. For all anneal treatment temperatures, experimental flame propagation rates for Al combined with nanoscale copper oxide (CuO) are in quantitative agreement with the theoretical predictions based on the MDM. The best treatment increases flame rate by 36% and achieves 68% of that for the best Al nanoparticles.Item Thermal-recoverable tough hydrogels enhanced by porphyrin decorated graphene oxide(2019) Wang, Jilong; Wei, Junhua (TTU); Su, Siheng; Qiu, Jingjing (TTU); Hu, Zhonglue; Hasan, Molla; Vargas, Evan (TTU); Pantoya, Michelle (TTU); Wang, ShirenArtificial tissue materials usually suffer properties and structure loss over time. As a usual strategy, a new substitution is required to replace the worn one to maintain the functions. Although several approaches have been developed to restore the mechanical properties of hydrogels, they require direct heating or touching, which cannot be processed within the body. In this manuscript, a photothermal method was developed to restore the mechanical properties of the tough hydrogels by using near infrared (NIR) laser irradiation. By adding the porphyrin decorated graphene oxide (PGO) as the nanoreinforcer and photothermal agent into carrageenan/polyacrylamide double network hydrogels (PDN), the compressive strength of the PDN was greatly improved by 104%. Under a short time of NIR laser irradiation, the PGO effectively converts light energy to thermal energy to heat the PDN hydrogels. The damaged carrageenan network was rebuilt, and a 90% compressive strength recovery was achieved. The PGO not only significantly improves the mechanical performance of PDN, but also restores the compressive property of PDN via a photothermal method. These tough hydrogels with superior photothermal recovery may work as promising substitutes for load-bearing tissues.