The Experts below are selected from a list of 327 Experts worldwide ranked by ideXlab platform
Chorng Haur Sow - One of the best experts on this subject based on the ideXlab platform.
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Electrically driven Incandescence of carbon nanotubes in controlled gaseous environments
Scripta Materialia, 2011Co-Authors: Srinivasan Natarajan, Zhi Han Lim, G. Wee, Subodh Mhaisalkar, Chorng Haur SowAbstract:Carbon nanotube buckypaper was electrically driven to Incandescence in controlled environments of air composition vacuum, argon and helium. The optical spectrum of the blackbody radiation was analyzed to characterize the emission at different pressures in the various environments. The Incandescence intensity and temperature were found to be lower at higher pressures, with the observations attributed to increased heat loss by conduction and convection to the ambient. A modified thermal conduction equation is suggested to explain the experimental results.
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Systematic investigation of sustained laser-induced Incandescence in carbon nanotubes
Journal of Applied Physics, 2010Co-Authors: Zhi Han Lim, Andrielle Lee, Yanwu Zhu, Kassandra Yu Yan Lim, Chorng Haur SowAbstract:A focused laser beam irradiating on aligned carbon nanotubes (CNTs) in moderate vacuum results in bright and sustained laser-induced Incandescence (LII) in CNTs. The Incandescence corresponds to blackbody radiation from laser-heated CNTs at ∼2400 K. Post-LII craters with well-defined ring boundaries in the CNT array were observed and examined with scanning electron microscopy and Raman spectroscopy. The enhanced purity of CNTs after LII as indicated by Raman spectroscopy studies was attributed to the removal of amorphous carbons on the as-grown CNTs during LII. A dynamic study of the crater formation further elucidates the nature of such craters. Through a systematic study of the effect of vacuum level and gaseous environment on LII, we discovered the process of thermal runaway during LII in CNTs. Thermal runaway is a threat to a sustained LII and can be prevented in nitrogen and argon environments. Oxygen was found to be responsible for thermal runaway reactions.
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sustained laser induced Incandescence in carbon nanotubes for rapid localized heating
Applied Physics Letters, 2009Co-Authors: Zhi Han Lim, Andrielle Lee, Yanwu Zhu, Kim Yong Lim, Chorng Haur SowAbstract:Sustained laser-induced Incandescence (LII) was observed when a continuous wave laser beam was focused on aligned multiwalled carbon nanotubes (CNTs) in vacuum. The sustained Incandescence originated from radiative dissipation of heated CNTs due to laser-CNT interactions. Sustainability of the LII up to 2 h was achieved. Fittings of the LII intensity spectrum with Planck blackbody distribution indicate a rise of temperature from room temperature to ∼2500 K in less than 0.1 s. This provides an effective way of achieving rapid high temperature heating at specific localized positions within CNT arrays.
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Sustained laser induced Incandescence in carbon nanotubes for rapid localized heating
Applied Physics Letters, 2009Co-Authors: Zhi Han Lim, Andrielle Lee, Yanwu Zhu, Kim Yong Lim, Chorng Haur SowAbstract:Sustained laser-induced Incandescence (LII) was observed when a continuous wave laser beam was focused on aligned multiwalled carbon nanotubes (CNTs) in vacuum. The sustained Incandescence originated from radiative dissipation of heated CNTs due to laser-CNT interactions. Sustainability of the LII up to 2 h was achieved. Fittings of the LII intensity spectrum with Planck blackbody distribution indicate a rise of temperature from room temperature to ∼2500 K in less than 0.1 s. This provides an effective way of achieving rapid high temperature heating at specific localized positions within CNT arrays.Sustained laser-induced Incandescence (LII) was observed when a continuous wave laser beam was focused on aligned multiwalled carbon nanotubes (CNTs) in vacuum. The sustained Incandescence originated from radiative dissipation of heated CNTs due to laser-CNT interactions. Sustainability of the LII up to 2 h was achieved. Fittings of the LII intensity spectrum with Planck blackbody distribution indicate a rise of temperature from room temperature to ∼2500 K in less than 0.1 s. This provides an effective way of achieving rapid high temperature heating at specific localized positions within CNT arrays.
Zhi Han Lim - One of the best experts on this subject based on the ideXlab platform.
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Electrically driven Incandescence of carbon nanotubes in controlled gaseous environments
Scripta Materialia, 2011Co-Authors: Srinivasan Natarajan, Zhi Han Lim, G. Wee, Subodh Mhaisalkar, Chorng Haur SowAbstract:Carbon nanotube buckypaper was electrically driven to Incandescence in controlled environments of air composition vacuum, argon and helium. The optical spectrum of the blackbody radiation was analyzed to characterize the emission at different pressures in the various environments. The Incandescence intensity and temperature were found to be lower at higher pressures, with the observations attributed to increased heat loss by conduction and convection to the ambient. A modified thermal conduction equation is suggested to explain the experimental results.
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Systematic investigation of sustained laser-induced Incandescence in carbon nanotubes
Journal of Applied Physics, 2010Co-Authors: Zhi Han Lim, Andrielle Lee, Yanwu Zhu, Kassandra Yu Yan Lim, Chorng Haur SowAbstract:A focused laser beam irradiating on aligned carbon nanotubes (CNTs) in moderate vacuum results in bright and sustained laser-induced Incandescence (LII) in CNTs. The Incandescence corresponds to blackbody radiation from laser-heated CNTs at ∼2400 K. Post-LII craters with well-defined ring boundaries in the CNT array were observed and examined with scanning electron microscopy and Raman spectroscopy. The enhanced purity of CNTs after LII as indicated by Raman spectroscopy studies was attributed to the removal of amorphous carbons on the as-grown CNTs during LII. A dynamic study of the crater formation further elucidates the nature of such craters. Through a systematic study of the effect of vacuum level and gaseous environment on LII, we discovered the process of thermal runaway during LII in CNTs. Thermal runaway is a threat to a sustained LII and can be prevented in nitrogen and argon environments. Oxygen was found to be responsible for thermal runaway reactions.
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sustained laser induced Incandescence in carbon nanotubes for rapid localized heating
Applied Physics Letters, 2009Co-Authors: Zhi Han Lim, Andrielle Lee, Yanwu Zhu, Kim Yong Lim, Chorng Haur SowAbstract:Sustained laser-induced Incandescence (LII) was observed when a continuous wave laser beam was focused on aligned multiwalled carbon nanotubes (CNTs) in vacuum. The sustained Incandescence originated from radiative dissipation of heated CNTs due to laser-CNT interactions. Sustainability of the LII up to 2 h was achieved. Fittings of the LII intensity spectrum with Planck blackbody distribution indicate a rise of temperature from room temperature to ∼2500 K in less than 0.1 s. This provides an effective way of achieving rapid high temperature heating at specific localized positions within CNT arrays.
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Sustained laser induced Incandescence in carbon nanotubes for rapid localized heating
Applied Physics Letters, 2009Co-Authors: Zhi Han Lim, Andrielle Lee, Yanwu Zhu, Kim Yong Lim, Chorng Haur SowAbstract:Sustained laser-induced Incandescence (LII) was observed when a continuous wave laser beam was focused on aligned multiwalled carbon nanotubes (CNTs) in vacuum. The sustained Incandescence originated from radiative dissipation of heated CNTs due to laser-CNT interactions. Sustainability of the LII up to 2 h was achieved. Fittings of the LII intensity spectrum with Planck blackbody distribution indicate a rise of temperature from room temperature to ∼2500 K in less than 0.1 s. This provides an effective way of achieving rapid high temperature heating at specific localized positions within CNT arrays.Sustained laser-induced Incandescence (LII) was observed when a continuous wave laser beam was focused on aligned multiwalled carbon nanotubes (CNTs) in vacuum. The sustained Incandescence originated from radiative dissipation of heated CNTs due to laser-CNT interactions. Sustainability of the LII up to 2 h was achieved. Fittings of the LII intensity spectrum with Planck blackbody distribution indicate a rise of temperature from room temperature to ∼2500 K in less than 0.1 s. This provides an effective way of achieving rapid high temperature heating at specific localized positions within CNT arrays.
Xiaodong Cui - One of the best experts on this subject based on the ideXlab platform.
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Light-Induced Incandescence of Single-Walled Carbon Nanotubes
The Journal of Physical Chemistry C, 2008Co-Authors: Hualing Zeng, Chunlei Yang, Junfeng Dai, Xiaodong CuiAbstract:We report the light-induced Incandescence of single-walled carbon nanotubes excited by weak visible and infrared laser beams. The phenomenon does not occur on bulk graphite and amorphous carbon under the same conditions. The intensity of the Incandescence is exponentially proportional to the incident laser power and the inverse of the gas pressure. After switching off the laser, the Incandescence follows a simple exponential decay with a time constant of 160 μs which is independent of the initial intensity. The temperature derived from the blackbody radiation approximation agrees with the result from the Raman spectra. We attribute the Incandescence of carbon nanotubes to the less thermal dissipation channels and low heat capacitance.
G. Zizak - One of the best experts on this subject based on the ideXlab platform.
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Saturation curves of two-color laser-induced Incandescence measurements for the investigation of soot optical properties
Applied Physics B, 2015Co-Authors: F. Migliorini, S. Maffi, S De Iuliis, G. ZizakAbstract:Two-color laser-induced Incandescence (LII) measurements are carried out in diffusion flames and at the exhaust of a homemade soot generator, both fueled with ethylene and methane. Two-color prompt LII signals, their ratio and the corresponding temperature have been analyzed as a function of laser fluence. In particular, the effect of fuel, soot load and gas/particle initial temperature on LII measurements have been investigated. LII spectral measurements have also been performed in all conditions for validation. The results suggest that the Incandescence is sensitive to both optical and non-optical physical properties of the particles. Moreover, soot volume fraction measurements are dependent on the laser fluence used, indicating that the soot temperature influences the refractive index absorption function. Such issues can be overcome by working at high laser fluences, where the saturation curves are independent from the experimental conditions if the soot absorption function near soot sublimation threshold is known.
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Special Issue: Laser-Induced Incandescence
Applied Physics B, 2011Co-Authors: G. ZizakAbstract:Detection of nanoparticles is an area of particular interest for the scientific community. Nanoparticles are ubiquitous, i.e. carbonaceous nanoparticles, or soot, originating from a variety of anthropogenic combustion sources and biomass burning; they greatly reduce the air quality and affect the public health. On the other side innovative materials are obtained in new industrial processes based upon flame synthesis of nanoparticles with highly specific functionalities. Several techniques are commonly used for the measurement and characterization of nanoparticles. Laser-Induced Incandescence (LII) is a diagnostic technique that offers numerous advantages. It is an optical, nonintrusive technique that gives a measure of both the concentration and the size of nanoparticles, with the possibility of 2D imaging, thus allowing for the study of the nanoparticle formation processes. Moreover, it is highly sensitive, which is relevant for environmental applications. The LII technique basically involves a fast heating of the nanoparticles by absorption of laser light on a nanosecond scale and a time-resolved detection of the induced Incandescence signal. Depending on the experimental conditions many physical processes are involved that are not completely understood. This was well illustrated in the first workshop on LII held in Duisburg, Germany in 2005 and in the Special issue on Laser-Induced Incandescence of Applied Physics B in 2006. Scientists interested in the develop-
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investigation on thermal accommodation coefficient and soot absorption function with two color tire lii technique in rich premixed flames
Applied Physics B, 2011Co-Authors: S. Maffi, F. Cignoli, S De Iuliis, G. ZizakAbstract:Although the two-color laser-induced Incandescence technique (2C-LII) has proved to be a significant tool for soot diagnostics, many efforts are still required to gain a whole understanding of the chemical and physical processes involved.
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Laser-induced Incandescence of titania nanoparticles synthesized in a flame
Applied Physics B, 2009Co-Authors: F. Cignoli, C. Bellomunno, S. Maffi, G. ZizakAbstract:Laser induced Incandescence experiments were carried out in a flame reactor during titania nanoparticle synthesis. The structure of the reactor employed allowed for a rather smooth particle growth along the flame axis, with limited mixing of different size particles. Particle Incandescence was excited by the 4th harmonic of a Nd:YAG laser. The radiation emitted from the particles was recorded in time and checked by spectral analysis. Results were compared with measurements from transmission electron microscopy of samples taken at the same locations probed by Incandescence. This was done covering a portion of the flame length within which a particle size growth of a factor of about four was detected . The Incandescence decay time was found to increase monotonically with particle size. The attainment of a process control tool in nanoparticle flame synthesis appears to be realistic.
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Spectral effects in laser induced Incandescence application to flame-made titania nanoparticles
Spectrochimica Acta Part B: Atomic Spectroscopy, 2008Co-Authors: S. Maffi, F. Cignoli, C. Bellomunno, S De Iuliis, G. ZizakAbstract:Abstract Particle size is a crucial parameter in nanopowder use and production. A method to obtain information about this during the particle synthesis would be very valuable in order to optimize the process. In the field of nanoparticles flame synthesis, an extension of the techniques used in soot diagnostics sounds rather obvious, but it is far from being easily accomplished. In this paper investigations on the application of the laser induced Incandescence to TiO 2 nanoparticles in a flame reactor are reported. The work basically concerns the effects of laser fluence on the spectral structure of the laser-excited radiation emitted from the particles. It will be shown that in many cases such a radiation cannot be plainly assumed as an Incandescence signal. Measurements of the signal time decay are reported and interpreted in the light of the spectral indications. Finally, the dependence of such a time decay on the particle size is experimentally demonstrated.
Andrielle Lee - One of the best experts on this subject based on the ideXlab platform.
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Systematic investigation of sustained laser-induced Incandescence in carbon nanotubes
Journal of Applied Physics, 2010Co-Authors: Zhi Han Lim, Andrielle Lee, Yanwu Zhu, Kassandra Yu Yan Lim, Chorng Haur SowAbstract:A focused laser beam irradiating on aligned carbon nanotubes (CNTs) in moderate vacuum results in bright and sustained laser-induced Incandescence (LII) in CNTs. The Incandescence corresponds to blackbody radiation from laser-heated CNTs at ∼2400 K. Post-LII craters with well-defined ring boundaries in the CNT array were observed and examined with scanning electron microscopy and Raman spectroscopy. The enhanced purity of CNTs after LII as indicated by Raman spectroscopy studies was attributed to the removal of amorphous carbons on the as-grown CNTs during LII. A dynamic study of the crater formation further elucidates the nature of such craters. Through a systematic study of the effect of vacuum level and gaseous environment on LII, we discovered the process of thermal runaway during LII in CNTs. Thermal runaway is a threat to a sustained LII and can be prevented in nitrogen and argon environments. Oxygen was found to be responsible for thermal runaway reactions.
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sustained laser induced Incandescence in carbon nanotubes for rapid localized heating
Applied Physics Letters, 2009Co-Authors: Zhi Han Lim, Andrielle Lee, Yanwu Zhu, Kim Yong Lim, Chorng Haur SowAbstract:Sustained laser-induced Incandescence (LII) was observed when a continuous wave laser beam was focused on aligned multiwalled carbon nanotubes (CNTs) in vacuum. The sustained Incandescence originated from radiative dissipation of heated CNTs due to laser-CNT interactions. Sustainability of the LII up to 2 h was achieved. Fittings of the LII intensity spectrum with Planck blackbody distribution indicate a rise of temperature from room temperature to ∼2500 K in less than 0.1 s. This provides an effective way of achieving rapid high temperature heating at specific localized positions within CNT arrays.
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Sustained laser induced Incandescence in carbon nanotubes for rapid localized heating
Applied Physics Letters, 2009Co-Authors: Zhi Han Lim, Andrielle Lee, Yanwu Zhu, Kim Yong Lim, Chorng Haur SowAbstract:Sustained laser-induced Incandescence (LII) was observed when a continuous wave laser beam was focused on aligned multiwalled carbon nanotubes (CNTs) in vacuum. The sustained Incandescence originated from radiative dissipation of heated CNTs due to laser-CNT interactions. Sustainability of the LII up to 2 h was achieved. Fittings of the LII intensity spectrum with Planck blackbody distribution indicate a rise of temperature from room temperature to ∼2500 K in less than 0.1 s. This provides an effective way of achieving rapid high temperature heating at specific localized positions within CNT arrays.Sustained laser-induced Incandescence (LII) was observed when a continuous wave laser beam was focused on aligned multiwalled carbon nanotubes (CNTs) in vacuum. The sustained Incandescence originated from radiative dissipation of heated CNTs due to laser-CNT interactions. Sustainability of the LII up to 2 h was achieved. Fittings of the LII intensity spectrum with Planck blackbody distribution indicate a rise of temperature from room temperature to ∼2500 K in less than 0.1 s. This provides an effective way of achieving rapid high temperature heating at specific localized positions within CNT arrays.
