Numerical Study of Thermo-Chromic Properties of VO2-Polymer Composites Coatings Applied to Building Thermal Insulation

Iken, Omar; Agounoun, Rachid; Rahmoune, Miloud; Sbai, K.; Zoubir, Amine; Saadani, Rachid; Rahmani, Abdelali

doi:10.21817/ijet/2017/v9i2/170902148

Cited by 4 publications

(4 citation statements)

References 17 publications

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“…This interaction leads to expansion and compression of the spring and sets the electron at oscillating motion. The oscillations are regarding the electronic arrangement and the density of states at the levels of atomic orbitals [14,24]. The complex permittivity and the complex refractive index are given in [13,25] as.…”

Section: The Modelmentioning

confidence: 99%

Thermochromic and opacity behaviors in vanadium dioxide nanofilms: a theoretical study

Shallal

Abdul-Ameer

Abdul-Hasan

et al. 2022

Mater. Res. Express

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Vanadium dioxide nanofilms are one of the most essential materials in electronic applications like smart windows. Therefore, studying and understanding the optical properties of such films is crucial to modifying the parameters that control these properties. To this end, this work focuses on investigating the opacity as a function of the energy directed at the nanofilms with different thicknesses (1 – 100) nm. Effective mediator theories (EMTs), which are considered as the application of Bruggeman's formalism and the Looyenga mixing rule, have been used to estimate the dielectric constant of VO2 nanofilms. The results show different opacity behaviors at different wavelength ranges (ultraviolet, visible, and infrared). The results depict that the highest opacity of the insulating phase is achieved at the ultraviolet region and it reduces for the metal phase. Besides, the results demonstrate that the opacity possesses a redshift during the changes at the three phases. Regarding the infrared region, the lowest opacity value is achieved at the insulator phase and it increases to the highest value at the metal phase. In the visible region, the opacity behavior remains similar in the three phases. It is worth noting that the lowest opacity is found for thinner nanofilm. Since both the refractive index and the extinction index are among the most essential optical constants, hence, both of them were compared with the experiment results, and an excellent agreement is achieved between them.

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Section: The Modelmentioning

confidence: 99%

Thermochromic and opacity behaviors in vanadium dioxide nanofilms: a theoretical study

Shallal

Abdul-Ameer

Abdul-Hasan

et al. 2022

Mater. Res. Express

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“…The interaction leads to stretching and compression to the spring and sets the electron into oscillating motion. These oscillations are regarding the electronic configuration and the density of states at the levels of atomic orbitals [14,21]. The complex permittivity and the complex refractive index are related in [14, 21 , 22]:…”

Section: The Modelmentioning

confidence: 99%

The Crystallite Size Dependence of the Transmittance Property of Vanadium Dioxide Nano Films

Abdul-Ameer

Shallal

Abdul-Hasan

et al. 2022

MSF

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Bruggeman's symmetric effective-medium model of vanadium oxide is introduced, in which the transmittance was studied because of its importance in the subject of smart windows, it was studied from ( 5 nm-1000 nm) for each of the regions of the electromagnetic spectrum, the ultraviolet and visible region, and the near and medium sub-regions of the infrared and the results showed that the importance of studying the transmittance of vanadium oxide as a good candidate For this kind of industries. Our results showed that the small sizes of the material guarantee an almost constant and high transmittance to the visible region; this is due to the agreement of the direction of the dipoles in the material with the direction of the internal electric field, which leads to an increase in the value of the refractive index. The refractive index represents the gain in the permittivity of the material presented by Bruggeman's model. For the other regions where the transmittance is not desirable, it can be controlled by the film’s size of the transmittance on the one hand and the wavelength on the other hand.

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“…The second limitation is related to high absorption in the visible part of solar spectrum, this phenomenon was noticed experimentally by C.G. Granqvist et al [6] and Y. Gao et al [7], and numerically O. Iken et al [8] using the kubelka Munk method.The study of thermo-chromic properties of VO 2 requires data of optical constants (refractive index n (T, λ) and extinction coefficient k (T, λ)) for different temperatures above and under transition. The determination of those two properties is purely experimental, thus it requires simple fabrication and characterization by ellipsometry [9].…”

mentioning

confidence: 94%

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confidence: 94%

Numerical Characterization of Vanadium Dioxide Thin Films Applied to Thermal Building Insulation: Determination of Dielectric Constant Using PSO Algorithm

Iken¹,

Bouyghf²,

Bouazaoui³

et al. 2017

IJET

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Abstract-Radiative rectification is one of the newest solutions for thermal building insulation. It is a phenomenon which has good analogy with electronic diode principle. It consists on being blocking for solar radiations in summer and passing radiations in winter. Among materials which have rectification capacity, Vanadium dioxide (VO 2 ) offers good applicability to building insulation with quite good rectification efficiency. VO 2 has a transition temperature around 68°C. Under this temperature, the material has a semiconductor crystallographic structure; therefore it becomes transparent to visible and infrared solar spectra. Above 68°C, the crystallographic structure of VO 2 changes to a metallic state for which it becomes more reflective to the same spectra. This semiconductor/metallic transition influences the optical properties of VO 2 which are highly dependent to temperature and wavelength. These properties are refractive index n(T,λ) and extinction coefficient k(T,λ), they are necessary in the optical study of VO 2 insulation capacities. Determination of these properties is purely experimental using ellipsometry techniques. In this work we suggest a method for numerical determination of these optical properties. This method uses the Particle Swarm Optimization (PSO) algorithm and it is based on the theoretical model of Lorentz oscillators at VO 2 nanoparticles scale. We calculated n(T,λ) and k(T,λ) for 3 temperatures and compared them with experimental results. This comparison showed good agreement between numerical and experimental results.Vanadium-dioxide, radiative rectification, building insulation, optical properties, optimization algorithms. I. INTRODUCTION Vanadium dioxide is a metal oxide that attracts many research teams over the world. It offers thermo-chromic properties depending on its semiconductor/metallic phase transition around 68°C [1,2]. VO 2 has many potential applications as a photonic device. In our case, we are trying to use VO 2 as a smart solution for radiative rectification applied to thermal building insulation, a smart solution because of its thermo-chromic properties highly dependent to temperature. At temperatures less than 68°C, VO 2 has a semiconductor crystallographic structure, with inter-atomic distances which allow high radiative transmission. Above 68°C, VO 2 switches to a metallic structure with small inter-atomic distances, thus VO 2 become more reflective to solar radiations. VO 2 is proposed for application to building glazing as smart window coatings by C.G. Granqvist et al [3]. The transition temperature too high compared with the comfort temperature is one of the limitations for smart windows application. G.V. Jorgenson et al [4] and W. Burkhardt et al [5] proposed a solution to decrease the VO 2 transition temperature by doping with some materials such as tungsten (W), Fluoride (F) and Molybdenum (Mo) with calculated concentrations to adjust the transition temperature around 25°C. The second limitation is related to high absorption in the visible part of sol...

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Numerical Study of Thermo-Chromic Properties of VO2-Polymer Composites Coatings Applied to Building Thermal Insulation

Cited by 4 publications

References 17 publications

Thermochromic and opacity behaviors in vanadium dioxide nanofilms: a theoretical study

Thermochromic and opacity behaviors in vanadium dioxide nanofilms: a theoretical study

The Crystallite Size Dependence of the Transmittance Property of Vanadium Dioxide Nano Films

Numerical Characterization of Vanadium Dioxide Thin Films Applied to Thermal Building Insulation: Determination of Dielectric Constant Using PSO Algorithm

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