Effect of Laser Irradiation on Emissivity of Flame-Generated Nanooxides
The application of pyrometry to retrieve particle temperature in particulate-generating flames strictly requires the knowledge of the spectral behavior of emissivity of light-emitting particles. Normally, this spectral behavior is considered time-independent. The current paper challenges this assump...
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MDPI AG
2021-04-01
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| Series: | Materials |
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| Online Access: | https://www.mdpi.com/1996-1944/14/9/2303 |
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| author | Silvana De Iuliis Roberto Dondè Igor Altman |
| author_facet | Silvana De Iuliis Roberto Dondè Igor Altman |
| author_sort | Silvana De Iuliis |
| collection | DOAJ |
| description | The application of pyrometry to retrieve particle temperature in particulate-generating flames strictly requires the knowledge of the spectral behavior of emissivity of light-emitting particles. Normally, this spectral behavior is considered time-independent. The current paper challenges this assumption and explains why the emissivity of oxide nanoparticles formed in flame can change with time. The suggested phenomenon is related to transitions of electrons between the valence and conduction energy bands in oxides that are wide-gap dielectrics. The emissivity change is particularly crucial for the interpretation of fast processes occurring during laser-induced experiments. In the present work, we compare the response of titania particles produced by a flame spray to the laser irradiation at two different excitation wavelengths. The difference in the temporal behavior of the corresponding light emission intensities is attributed to the different mechanisms of electron excitation during the laser pulse. Interband transitions that are possible only in the case of the laser photon energy exceeding the titania energy gap led to the increase of the electron density in the conduction band. Relaxation of those electrons back to the valence band is the origin of the observed emissivity drop after the UV laser irradiation. |
| first_indexed | 2024-03-10T11:50:11Z |
| format | Article |
| id | doaj.art-7271093aa4f4484a80627c316a9646a6 |
| institution | Directory Open Access Journal |
| issn | 1996-1944 |
| language | English |
| last_indexed | 2024-03-10T11:50:11Z |
| publishDate | 2021-04-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Materials |
| spelling | doaj.art-7271093aa4f4484a80627c316a9646a62023-11-21T17:45:23ZengMDPI AGMaterials1996-19442021-04-01149230310.3390/ma14092303Effect of Laser Irradiation on Emissivity of Flame-Generated NanooxidesSilvana De Iuliis0Roberto Dondè1Igor Altman2CNR-ICMATE, Institute of Condensed Matter Chemistry and Technologies for Energy, Via R. Cozzi 53, 20125 Milan, ItalyCNR-ICMATE, Institute of Condensed Matter Chemistry and Technologies for Energy, Via R. Cozzi 53, 20125 Milan, ItalyCombustion Sciences and Propulsion Research Branch, Naval Air Warfare Center Weapons Division, 1 Administration Circle, China Lake, CA 93555, USAThe application of pyrometry to retrieve particle temperature in particulate-generating flames strictly requires the knowledge of the spectral behavior of emissivity of light-emitting particles. Normally, this spectral behavior is considered time-independent. The current paper challenges this assumption and explains why the emissivity of oxide nanoparticles formed in flame can change with time. The suggested phenomenon is related to transitions of electrons between the valence and conduction energy bands in oxides that are wide-gap dielectrics. The emissivity change is particularly crucial for the interpretation of fast processes occurring during laser-induced experiments. In the present work, we compare the response of titania particles produced by a flame spray to the laser irradiation at two different excitation wavelengths. The difference in the temporal behavior of the corresponding light emission intensities is attributed to the different mechanisms of electron excitation during the laser pulse. Interband transitions that are possible only in the case of the laser photon energy exceeding the titania energy gap led to the increase of the electron density in the conduction band. Relaxation of those electrons back to the valence band is the origin of the observed emissivity drop after the UV laser irradiation.https://www.mdpi.com/1996-1944/14/9/2303pyrometryparticulate-generating flameemissivityenergy gapelectron transitions |
| spellingShingle | Silvana De Iuliis Roberto Dondè Igor Altman Effect of Laser Irradiation on Emissivity of Flame-Generated Nanooxides Materials pyrometry particulate-generating flame emissivity energy gap electron transitions |
| title | Effect of Laser Irradiation on Emissivity of Flame-Generated Nanooxides |
| title_full | Effect of Laser Irradiation on Emissivity of Flame-Generated Nanooxides |
| title_fullStr | Effect of Laser Irradiation on Emissivity of Flame-Generated Nanooxides |
| title_full_unstemmed | Effect of Laser Irradiation on Emissivity of Flame-Generated Nanooxides |
| title_short | Effect of Laser Irradiation on Emissivity of Flame-Generated Nanooxides |
| title_sort | effect of laser irradiation on emissivity of flame generated nanooxides |
| topic | pyrometry particulate-generating flame emissivity energy gap electron transitions |
| url | https://www.mdpi.com/1996-1944/14/9/2303 |
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