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ABSTRACT: A complete theoretical model is presented for the thermal mirror technique under top-hat laser excitation. Considering the
attenuation of the top-hat excitation laser intensity along the thickness of a sample due to its optical absorption coefficient,
we calculate the laser-induced temperature and surface deformation profiles. Asimplified theoretical model for a high absorption
sample is also developed. The center intensity of a probe beam reflected from the thermal mirror at a detector plane is derived.
Numerical simulation shows that the thermal mirror under the top-hat laser excitation is as sensitive as that under Gaussian
laser excitation. With top-hat laser excitation, the experimental results of thermo-physical properties of opaque samples
are found to be well consistent with literature values, validating the theory.
Applied Physics B 04/2012; 94(3):473-481. · 2.19 Impact Factor
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ABSTRACT: Export Date: 18 July 2012, Source: Scopus, Art. No.: 091908, CODEN: APPLA, doi: 10.1063/1.3691253, Language of Original Document: English, Correspondence Address: Astrath, N.G.C.; Departamento de Física, Universidade Estadual de Maringá, Maringá, PR 87020-900, Brazil; email: astrathngc@pq.cnpq.br, References: Vargas, H., Miranda, L.C.M., (1988) Phys. Rep., 161, p. 43. , 10.1016/0370-1573(88)90100-7;
Applied Physics Letters 01/2012; 100(9). · 3.84 Impact Factor
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ABSTRACT: We report a theoretical model and experimental results for laser-induced local heating in liquids, and propose a method to detect and quantify the contributions of photochemical and Soret effects in several different situations. The time-dependent thermal and mass diffusion equations in the presence and absence of laser excitation are solved. The two effects can produce similar transients for the laser-on refractive index gradient, but very different laser-off behavior. The Soret effect, also called thermal diffusion, and photochemical reaction contributions in photochemically reacting aqueous Cr(VI)-diphenylcarbazide, Eosin Y, and Eosin Y-doped micellar solutions, are decoupled in this work. The extensive use of lasers in various optical techniques suggests that the results may have significance extending from physical-chemical to biological applications.
Optics Express 02/2011; 19(5):4047-58. · 3.59 Impact Factor
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ABSTRACT: Considering the time dependence of the absorption coefficient due to the photo-induced chemical reaction (PCR) and species diffusion, we calculate the temperature rise in the thermal lens (TL) effect and the TL signal at the detector plane. This theoretical approach removes the restriction that the PCR time constant is much greater than the characteristic TL time constant, which was assumed in a previously published model. Aqueous Cr(VI)-diphenylcarbazide solution is investigated, and quantitative experimental results for the thermal, optical and PCR properties of the sample are obtained. The relative difference between the parameters extracted from the same experimental data of the Cr(VI) solution using the previous and present models is found to be less than 5%, showing the present model can be used to study the PCR. Moreover the present model is more general than the previous one.
Journal of Physics Conference Series 04/2010; 214(1):012125.
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ABSTRACT: In this work, we present a short review of the recent development of the theoretical models for top-hat cw laser induced spectroscopies of thermal lens and thermal mirror. With the same probe and top-hat excitation lasers, an apparatus is set up to concurrently measure both thermal lens and thermal mirror effects of transparent samples. With the theoretical models and the experimental apparatus, not only optical and thermal properties are measured, but also the fluorescence quantum coefficient and the temperature coefficient of the optical path length of a fluorescent sample are simultaneously determined with no need of any reference sample. Mechanical properties also could be measured. Opaque samples are also studied using top-hat cw laser thermal mirror and top-hat photothermal deflection techniques to determine thermal properties (e.g., thermal conductivity and unit volume specific heat). This work shows that the combined top-hat cw laser photothermal techniques are useful for nondestructive evaluation of both transparent and opaque samples with a less expensive non-TEM00 Gaussian laser.
Journal of Physics Conference Series 04/2010; 214(1):012014.
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ABSTRACT: Cited By (since 1996): 1, Export Date: 18 July 2012, Source: Scopus, Art. No.: 012014, doi: 10.1088/1742-6596/214/1/012014, Language of Original Document: English, Correspondence Address: Shen, J.; National Research Council of Canada, Institute for Fuel Cell Innovation, 4250 Wesbrook Mall, Vancouver, BC V6T 1W5, Canada; email: Jun.Shen@nrc-cnrc.gc.ca, References: Mandelis, A., (1991) Progress in Photoacoustic and Photothermal Science and Technology, , New York: Elsevier;
Journal of Physics Conference Series 01/2010; 214.
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ABSTRACT: Cited By (since 1996): 1, Export Date: 18 July 2012, Source: Scopus, Art. No.: 012016, doi: 10.1088/1742-6596/214/1/012016, Language of Original Document: English, Correspondence Address: Malacarne, L. C.; Departamento de Física, Universidade Estadual de Maringá, Av. Colombo 5790, 87020-900, Maringá, Paraná, Brazil; email: lcmala@dfi.uem.br, References: Shen, J., Lowe, R.D., Snook, R.D., (1992) Chem. Phys., 165, p. 385;
Journal of Physics Conference Series 01/2010; 214.
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ABSTRACT: Export Date: 18 July 2012, Source: Scopus, Art. No.: 012125, doi: 10.1088/1742-6596/214/1/012125, Language of Original Document: English, Correspondence Address: Astrath, N. G. C.; National Research Council Canada, Institute for Fuel Cell Innovation, 4250 Wesbrook Mall, Vancouver, BC V6T 1W5, Canada; email: AstrathNGC@pq.cnpq.br, References: Bialkowski, S.E., (1996) Photothermal Spectroscopy Methods for Chemical Analysis, , Wiley, New York;
Journal of Physics Conference Series 01/2010; 214.
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ABSTRACT: Cited By (since 1996): 5, Export Date: 18 July 2012, Source: Scopus, Art. No.: 191902, CODEN: APPLA, doi: 10.1063/1.3258661, Language of Original Document: English, Correspondence Address: Astrath, N. G. C.; National Research Council Canada, IFCI, 4250 Wesbrook Mall, Vancouver, BC V6T 1W5, Canada; email: astrathngc@pq.cnpq.br, References: Bunting, B.G., Eaton, S.J., Storey, J., Fairbridge, C., Mitchell, K., Crawford, R.W., Gallant, T., Alnaijar, M., (2008), SAE International, 2008-01-2406Bialkowski, S.E., (1996) Photothermal Spectroscopy Methods for Chemical Analysis, , (Wiley, New York);
Applied Physics Letters 01/2009; 95(19). · 3.84 Impact Factor
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ABSTRACT: A general and complete theoretical model of the time-resolved thermal mirror method for the measurement of thermo-optical-mechanical properties of solid materials is developed. The laser-induced temperature profile in a sample and its thermoelastic surface displacement are derived. The center intensity of a probe beam at the detector plane is calculated using the Fresnel diffraction theory. Additionally, simplified models for high and low optical absorption samples are presented, and the suitability of the simplified models is also analyzed. The influence of experimental parameters on the sensitivity of the thermal mirror method is discussed for the optimization of the experimental apparatus. The presented model and the experimental technique can be used to quantitatively determine the physical properties of transparent and opaque solids.
Journal of Applied Physics 10/2008; · 2.17 Impact Factor
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ABSTRACT: Nanoscale surface displacement is used to determine thermo-optical–mechanical properties of high absorbing solids by means of the time-resolved thermal mirror method. The thermoelastic equation for the surface displacement and an expression for the probe beam intensity at the detector plane were derived. Experiments were performed in a high absorbing Ti O <sub>2</sub> -doped low silica calcium aluminosilicate glass, and obtained the valuable values of the fluorescence quantum efficiency and thermal properties. The results indicate that this method is reliable for the characterization of semitransparent, high absorbing, and opaque materials.
Applied Physics Letters 04/2008; · 3.84 Impact Factor
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ABSTRACT: Gas atomized pure Al powders were successfully consolidated into full density at room temperature by newly developed cold hydro-mechanical pressing (CHMP). The effects of the configuration of pressures on the relative density and microstructure of consolidated specimens were investigated. The full density consolidation of metal powders at room temperature resulted from severe shear deformation of the particles which ruptured the surface oxide layers. Our works demonstrate that the novel CHMP provides an economical approach to consolidate particulate material into high quality bulk preforms for engineering applications.Highlights► Gas atomized pure Al powders were consolidated at room temperature into full density body. ► The consolidated material shows significantly improved properties. ► This work demonstrates the reliability of a cold hydro-mechanical pressing apparatus.
Materials Science and Engineering: A. 528(18):5784-5789.
