| 1. |
- Amdani, Rima Zuriah, et al.
(author)
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Raman spectroscopy for characterizing porous carbon
- 2020
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In: Laser Applications to Chemical, Security and Environmental Analysis, LACSEA 2020. - 9781557528209
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Conference paper (peer-reviewed)abstract
- Raman spectroscopy is performed to disclose structural properties of porous carbon samples including lignocellulosic biomass. Analysis of spectral signatures of carbon, around 1350 cm-1 and 1580 cm-1, indicates higher porosity for the biomass sample.
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| 2. |
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| 3. |
- Bai, Xiao, et al.
(author)
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Absorption of formaldehyde (H2CO) in the (A)over-tilde(1)A(2)
- 2004
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In: Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy. - 1386-1425. ; 60:4, s. 821-828
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Journal article (peer-reviewed)abstract
- The electronic A(1)A(2) <-- X(1)A(1) absorption spectra of formaldehyde vapour were studied at temperatures varying from 423 to 770 K with variable pressures from less than 0.1 to 1 MPa. Broadband vibronic and partially rotationally resolved 4(n)(1) rovibronic spectra of formaldehyde showed considerable sensitivity to temperature. The high resolution spectra showed collision-induced broadening as the pressure was increased. The results show that the absorption efficiency of the laser radiation front the third harmonic of Nd:YAG lasers is sensitive to the spectral properties of the laser, such as line position and shape. Promising results were obtained from the comparison between theoretical and measured absorption spectra.
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| 4. |
- Bruno, Annalisa, et al.
(author)
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Detection of fluorescent nanoparticles in flame with femtosecond laser-induced fluorescence anisotropy
- 2008
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In: Optics Express. - 1094-4087. ; 16:8, s. 5623-5632
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Journal article (peer-reviewed)abstract
- The mean size of fluorescent nanoparticles produced in a propane flame has been measured with an in-situ technique employing a femtosecond laser to excite the sample and a streak camera for time-resolved detection of the fluorescence. The time profile of the fluorescence anisotropy showed a Gaussian behaviour, typical of free rotor reorientation. By measuring its width, we estimated an average carbon particle diameter of 3.3 nm, thus confirming the existence of combustion produced nanoparticles. The technique proves to be applicable to the study of gas-phase nanoparticles, both in combustion and environmental studies.
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| 5. |
- Bruno, A, et al.
(author)
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In situ detection of soot nanoparticles by time-resolved fluorescence analysis
- 2008
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In: Journal of Optics. A, Pure and Applied Optics. - : IOP Publishing. - 1741-3567 .- 1464-4258. ; 10:6, s. 5-064016
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Journal article (peer-reviewed)abstract
- We present a new implementation of the time-resolved fluorescence anisotropy technique for the analysis of carbon nanoparticles directly in a Bunsen-type propane flame. By exploiting femtosecond laser excitation, UV-visible laser-induced fluorescence and time resolution of the experimental set-up, small soot nanoparticles have been identified within the flame. From the measurement of the decay time of the anisotropy ratio, we determined an ensemble-averaged diameter of the carbon particles of approximately 10 nm, with a slightly larger value in the outer edge of the flame compared to its centre.
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| 6. |
- Kiefer, J., et al.
(author)
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Spectral interferences from formaldehyde in CH PLIF flame front imaging with broadband B-X excitation
- 2011
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In: Combustion and Flame. - : Elsevier BV. - 0010-2180. ; 158:3, s. 583-585
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Journal article (peer-reviewed)abstract
- In this letter we show that the use of slightly broadband laser sources like multimode alexandrite lasers for CH PLIF bears the danger of interferences from formaldehyde. Such interferences occur when the laser frequency is not carefully tuned to the B-X (0,0) R-branch band head at around 387.2 nm and manifest either in the appearance of an additional layer in the PLIF image or in a slight broadening of the actual CH layer. With careful frequency selection the formaldehyde signals were not observed. Suppression of the interferences is feasible by employing appropriate spectral filters. (C) 2010 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
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| 7. |
- Lynga, C, et al.
(author)
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A laser system providing tunable, narrow-band radiation from 35 nm to 2 mu m
- 2001
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In: Applied Physics B. - : Springer Science and Business Media LLC. - 0946-2171 .- 1432-0649. ; 72:8, s. 913-920
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Journal article (peer-reviewed)abstract
- We describe a laser system that readily provides radiation tunable from 2 mum in the infra-red to 35 nm in the extreme ultraviolet spectral range. The broad spectral range is covered through a range of non-linear processes such as Raman shifting and high-order harmonic generation. Pulses with duration of tens of picoseconds are obtained. The relative bandwidth of the radiation is delta lambda/lambda = 10(-4), comparable with what can be achieved by using high-resolution monochromators at state-of-the-art synchrotron beamlines. We discuss different methods for characterising the radiation in this wide wavelength regime. We also discuss the capabilities of the system from the measured parameters.
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| 8. |
- Metz, Thomas, et al.
(author)
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Fluorescence lifetimes of formaldehyde (H2CO) in the (A)over-tilde(1)A(2) -> (X)over-tilde(1)A(1) band system at elevated temperatures and pressures
- 2004
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In: Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy. - 1386-1425. ; 60:5, s. 1043-1053
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Journal article (peer-reviewed)abstract
- Fluorescence lifetimes of formaldehyde excited by picosecond laser radiation with a wavelength of 355 nm were determined in nitrogen gas in a cell using time-resolved laser-induced fluorescence spectroscopy. The measurements were conducted at temperatures between 295 and 770 K and pressures up to 10 bar (1 MPa). Detection was broadband in most cases. Temperature and pressure were found to have a quenching effect on the fluorescence. At 295 K and pressures between 1 and 5 bar, decay rates between 0.03 and 0.04 ns(-1) were observed. At 770 K, the decay rates increased from 0.11 to 0.17 ns(-1) as the pressure was raised from 1 to 10 bar. The dependence on pressure was not linear at 1 bar. At 10 bar the linearity is unclear. The dependence on temperature appeared to be exponential. (C) 2003 Elsevier B.V. All rights reserved.
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| 9. |
- Mousavi, Seyed Morteza, et al.
(author)
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Detailed modeling of hydrogen release and particle shrinkage during pyrolysis of inhomogeneous wood
- 2023
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In: Proceedings of the Combustion Institute. - : Elsevier BV. - 1540-7489. ; 39:3, s. 3323-3332
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Journal article (peer-reviewed)abstract
- Hydrogen release during pyrolysis of woody biomass is studied considering anisotropicity and inhomogeneity of wood structure. A new anisotropic shrinkage model is proposed based on the decomposition of main wood constituents, i.e., cellulose, hemicellulose, and lignin. The new shrinkage model can predict the temporal evolution of the wood structure, and the differences between axial and radial shrinkage during pyrolysis. The model agrees very well with several experimental data from the literature. Based on particle temperature during conversion, the pyrolysis is partitioned into four stages, and the hydrogen release and H2 formation from each stage are investigated. Stage (IV) of pyrolysis, from 1000 to 1273 K, is found to be efficient for H2 production owing to the production of considerable mass of H2 with a minimal amount of tar species. Furthermore, the char quality is found to be different at the end of stages (II), (III), and (IV), where around 67.7, 80.5, and 93.4% wt. of solid residue is made of carbon, respectively. The model is also used to explain how the heating rate affects the temperature distribution inside the particle and how it shifts the peak of hydrogen release. Finally, the pyrolysis of two inhomogeneous wood samples - a beech twig with bark and a beech dowel with growth rings - are investigated. The bark can affect the pyrolysis rate, products, and flow pattern inside the particle. The growth rings do not have a considerable effect on the pyrolysis rate and products, but they have a significant impact on the flow pattern. This has an important implication for char conversion studies where the internal surface area and porosity field distribution have a significant effect on the gasification and oxidation rates.
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| 10. |
- Omrane, Alaa, et al.
(author)
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Surface temperature measurement of flame spread using thermographic phosphors
- 2002
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In: Proceedings of 7th IAFSS Symposium on Fire Safety Science. ; , s. 141-152
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Conference paper (peer-reviewed)abstract
- A technique based on remote measurements of surface temperature in connection to fires is presented. Pulsed ultraviolet laser radiation at 266 nm and 7 ns duration was used to excite a thermographic phosphor, Mg4FGeO6: Mn, which was adapted on the surface of the investigated material. The laser-induced emission from the phosphor was recorded. A calibration of the phosphorescence lifetime and spectral properties against temperature allowed surface temperature measurements between 25°C and 500°C. The method was tested and compared with thermocouple measurements on burning materials such as lowdensity fiberboards and polymethylmethan acrylate.
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