Photothermal Characterization of Thermochromic Materials for Tunable Thermal Devices

Voti, R. Li; Leahu, Grigore; Larciprete, Maria Cristina; Sibilia, C.; Bertolotti, M.

doi:10.1007/s10765-014-1790-2

Cited by 15 publications

(4 citation statements)

References 57 publications

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“…It is a more suitable technique, if compared to conventional spectrophotometric ones, to measure the optical properties of nanomaterials and/or scattering media. Some of the authors of this manuscript have already applied PAS to investigate powders, due to its versatility and easy applicability with respect to other non-destructive acoustic [24][25][26][27], thermal and photothermal techniques [28][29][30][31][32] which use sophisticated laboratory instruments. In our analysis we used the Rosencwaig-Gersho (RG) theory [14], which was developed for non-scattering samples, and substantially modified for scattering samples by Helander et al [33] by using a diffusion equation for the photon distribution inside the sample.…”

Section: Optical Properties By Photoacoustic Spectroscopymentioning

confidence: 99%

Diatom frustules decorated with zinc oxide nanoparticles for enhanced optical properties

et al. 2017

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Zinc oxide (ZnO) nanoparticles were synthesized on diatomite (DE) surface by a low temperature sol gel technique, starting from zinc acetate dihydrate (Zn(CHCOO) · 2HO) solution in water/ethyl alcohol, in presence of triethanolamine (TEA) with functions of Zn chelating agent, catalyst and mediator of nanoparticle growth on DE surface. Microstructural features were investigated by field emission scanning electron microscopy and x-ray diffraction. ZnO crystalline nanoparticles, well distributed both on the surface and into the porous architecture of diatomite, were obtained just after the synthesis carried out at 80 °C without the need of calcination treatments. The optical properties of ZnO/DE hybrid powders were measured for the first time by means of photoacoustic spectroscopy (PAS). A new method to retrieve both the optical absorption and scattering coefficients from PAS is here discussed for powder aggregates. The fingerprint of the zinc oxide nanoparticles has been highlighted in the Mie scattering resonance in the UV-Vis range, and in the enhancement of the optical absorption with respect to diatomite.

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Section: Optical Properties By Photoacoustic Spectroscopymentioning

confidence: 99%

Diatom frustules decorated with zinc oxide nanoparticles for enhanced optical properties

et al. 2017

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“…(i) To act as antireflection coating so as to minimize the sample reflectance in the visible [49,50]; (ii) To maximize the absorbance in the metallic layers; (iii) To guarantee a low thermal emissivity in the mid-infrared thanks to the metal layers.…”

Section: Design Of the Multilayer Coatingmentioning

confidence: 99%

Optimization of Perfect Absorbers with Multilayer Structures

Voti

2018

Int J Thermophys

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We study wide-angle and broadband perfect absorbers with compact multilayer structures made of a sequence of ITO and TiN layers deposited onto a silver thick layer. An optimization procedure is introduced for searching the optimal thicknesses of the layers so as to design a perfect broadband absorber from 400 nm to 750 nm, for a wide range of angles of incidence from 0 • to 50 • , for both polarizations and with a low emissivity in the mid-infrared. We eventually compare the performances of several optimal structures that can be very promising for solar thermal energy harvesting and collectors.

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“…The thermal hysteresis intrinsic to the phase transition has been widely investigated and was found to be affected by several factors such as the film deposition temperature 17 , the use of different substrates 18 – 20 , the wavelength range 21 , the introduction of metallic dopants 22 and the dimensions of metallic grains 23 . In particular, if metallic grain size is smaller than the wavelength of excitation, diffraction effects result in enhanced transmitted signal.…”

Section: Introductionmentioning

confidence: 99%

Adaptive tuning of infrared emission using VO2 thin films

Larciprete

Centini

Paoloni

et al. 2020

Sci Rep

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Phase-transition materials provide exciting opportunities for controlling optical properties of photonic devices dynamically. Here, we systematically investigate the infrared emission from a thin film of vanadium dioxide (VO 2). We experimentally demonstrate that such thin films are promising candidates to tune and control the thermal radiation of an underlying hot body with different emissivity features. In particular, we studied two different heat sources with completely different emissivity features, i.e. a black body-like and a mirror-like heated body. The infrared emission characteristics were investigated in the 3.5-5.1 μm spectral range using the infrared thermography technique which included heating the sample, and then cooling back. Experimental results were theoretically analyzed by modelling the VO 2 film as a metamaterial for a temperature range close to its critical temperature. Our systematic study reveals that VO 2 thin films with just one layer 80 nm thick has the potential to develop completely different dynamic tuning of infrared radiation, enabling both black-body emission suppression and as well as mirror emissivity boosting, in the same single layer device. Understanding the dynamics and effects of thermal tuning on infrared emission will benefit wide range of infrared technologies including thermal emitters, sensors, active IR filters and detectors. The possibility to tune the spectral features of a device, triggered by a thermal, electrical or optical stimulation, paves the way for many applications such as perfect infrared absorbers 1-4 , smart intelligent window coatings 5,6 , thermal rectification devices 7 or diodes/rectifiers 8. Thermochromic materials, such as niobium dioxide (NbO 2), vanadium sesquioxide (V 2 O 3), and vanadium dioxide (VO 2) undergo an abrupt phase transition from semiconductor to metallic state at a specific phase transition temperature 9-11. This phase change transition, from insulating monoclinic phase into a metallic tetragonal (rutile) phase, is accompanied by drastic changes in electrical, optical and magnetic properties as a function of the temperature. Among them, VO 2 is widely employed since it pertains the lowest phase transition temperature, T c = 341 K (68 °C) 12. The strong and reproducible changes in optical properties due to phase transition, have generated a burgeoning amount of theoretical and experimental studies focusing on the thermal emissivity variation activated by temperature in VO 2 13,14 in the IR 15 and THz radiation ranges 16. The thermal hysteresis intrinsic to the phase transition has been widely investigated and was found to be affected by several factors such as the film deposition temperature 17 , the use of different substrates 18-20 , the wavelength range 21 , the introduction of metallic dopants 22 and the dimensions of metallic grains 23. In particular, if metallic grain size is smaller than the wavelength of excitation, diffraction effects result in enhanced transmitted signal. When temperature increases, the grain sizes of exp...

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Photothermal Characterization of Thermochromic Materials for Tunable Thermal Devices

Cited by 15 publications

References 57 publications

Diatom frustules decorated with zinc oxide nanoparticles for enhanced optical properties

Diatom frustules decorated with zinc oxide nanoparticles for enhanced optical properties

Optimization of Perfect Absorbers with Multilayer Structures

Adaptive tuning of infrared emission using VO2 thin films

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