Thermally switchable terahertz metasurface absorber composed of H-fractal and enabled by phase-change material of vanadium dioxide

Frequenz ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Hassan Divdel ◽  
Hamed Taghipour-Farshi ◽  
Hassan Rasooli Saghai ◽  
Mohammad-Ali Tavakoli Ghazi Jahani
Keyword(s):  
Phase Transition ◽  
Phase Change ◽  
Phase Change Material ◽  
Vanadium Dioxide ◽  
Ground Plane ◽  
Terahertz Range ◽  
Metallic State ◽  
Level 1 ◽  
Change Material ◽  
Level 2

Abstract A terahertz metasurface absorber with actively switchable bandwidth enabled by vanadium dioxide (VO2) is presented and investigated numerically. The VO2 is a phase-change material and its conductivity in the terahertz range changes by several orders of magnitude upon phase-transition. The metasurface consists of an H-shaped fractal resonator placed on top of a polyimide spacer and a ground-plane of gold. The resonator is composed of an H-shaped level-1 fractal of gold and VO2 strips that converts it to a level-2 fractal. At room temperatures, the VO2 is in the insulator state and the resonator reduces to a level-1 fractal offering narrowband absorption at 8.08 THz reaching 0.98 absorption. At higher temperatures, the VO2 is in the metallic state and the resonator is effectively a level-2 fractal with an absorption higher than 0.9 in a bandwidth of 6.63–9.89 THz.

Narrowband-to-broadband switchable and polarization-insensitive terahertz metasurface absorber enabled by phase-change material

2021 ◽  
Author(s):  
Seyed Hadi Badri ◽  
M. M. Gilarlue ◽  
Sanam SaeidNahaei ◽  
Jong Su KIM
Keyword(s):  
Phase Change ◽  
Phase Change Material ◽  
Ground Plane ◽  
Metallic State ◽  
Broadband Absorber ◽  
Broadband Absorption ◽  
Terahertz Absorber ◽  
Wide Range ◽  
Polarization Insensitive ◽  
Change Material

Abstract A terahertz absorber with controllable and switchable bandwidth and insensitive to polarization is of great interest. Here, we propose and demonstrate a metasurface absorber with switchable bandwidth based on a phase-change material of vanadium dioxide (VO2) and verify its performance by the finite element method simulations. The metasurface absorber is composed of a hybrid cross fractal as a resonator separated from a gold ground-plane by a polyimide spacer. Switching from narrowband to broadband absorber is achieved via connecting VO2 patches to the gold first-order cross fractal converting the resonator to a third-order cross fractal. In the insulator phase of VO2, the main narrowband absorption occurs at the frequency of 6.05 THz with a 0.99 absorption and a full-width half-maximum (FWHM) of 0.35 THz. Upon insulator-to-metal transition of VO2, the metasurface achieves a broadband absorption with the FWHM of 6.17 THz. The simulations indicate that by controlling the partial phase-transition of VO2, we can tune the bandwidth and absorption level of the absorber. Moreover, the designed absorber is insensitive to polarization due to symmetry and works well for a very wide range of incident angles. In the metallic state of VO2, the absorber has an absorption exceeding 0.5 in the 3.57-8.45 THz frequency range with incident angles up to 65°.

Tuning the optical response of a dielectric grating using vanadium-dioxide as a phase-change material

2021 ◽  
Author(s):  
Muhammad Fayyaz Kashif ◽  
Tiziana Stomeo ◽  
Francesco Guido ◽  
Maria A. Vincenti ◽  
Irene Vassalini ◽  
...  
Keyword(s):  
Phase Change ◽  
Phase Change Material ◽  
Vanadium Dioxide ◽  
Optical Response ◽  
Dielectric Grating ◽  
Change Material

Synthesis and Study of Microcapsules with Beeswax Core and Phenol-Formaldehyde Shell Using the Taguchi Method

2021 ◽  
Vol 7 (1) ◽  
pp. 1
Author(s):  
Tejashree Amberkar ◽  
Prakash Mahanwar
Keyword(s):  
Phase Transition ◽  
Transition Temperature ◽  
Taguchi Method ◽  
Phase Change ◽  
Phase Change Material ◽  
Surfactant Concentration ◽  
Phenol Formaldehyde ◽  
Processing Parameters ◽  
Agitation Speed ◽  
Change Material

Phenol-formaldehyde shelled phase change material microcapsules (MPCMs) were fabricated and their processing parameters were analyzed with the Taguchi method. Core to shell ratio, surfactant concentration and speed of mixing are the parameters that were optimized in five levels. The optimized values for the surfactant concentration, core to shell ratio and agitation speed were 3%, 1:1 and 800 rpm, respectively. The obtained microcapsules were spherical in shape. The melting enthalpy of the MPCMs synthesized with optimized processing parameters was 148.93 J/g in 35–62 °C. The obtained temperature range of phase transition temperature can be used for storing different food articles such as chocolate and hot served foods.

Fast electrical and optical activation of RF switches integrating vanadium dioxide (VO2) phase change material

2021 ◽  
Author(s):  
Crunteanu Aurelian ◽  
VK Thalakkatukalathil Vinod ◽  
Orlianges Jean-Christophe ◽  
Bessaudou Annie
Keyword(s):  
Phase Change ◽  
Phase Change Material ◽  
Vanadium Dioxide ◽  
Rf Switches ◽  
Optical Activation ◽  
Change Material

scholarly journals A Thermal Tuning Meta-Duplex-Lens (MDL): Design and Characterization

Nanomaterials ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 1135 ◽  
Author(s):  
Ning Xu ◽  
Yaoyao Liang ◽  
Yuan Hao ◽  
Min Mao ◽  
Jianping Guo ◽  
...  
Keyword(s):  
Phase Change ◽  
Phase Change Material ◽  
Electromagnetic Waves ◽  
Incident Light ◽  
Polarization State ◽  
Transmission Efficiency ◽  
Metallic State ◽  
Phase Gradient ◽  
Storage Devices ◽  
Change Material

Multifunctional metasurfaces play an important role in the development of integrated optical paths. However, some of the realizations of current multifunctional metasurface devices depend on polarization selectivity, and others change the polarization state of the outgoing light. Here, based on vanadium dioxide (VO2) phase change material, a strategy to design a meta-duplex-lens (MDL) is proposed and numerical simulation calculations demonstrate that at low temperature (about 300 K), VO2 behaves as a dielectric so that the MDL can act as a transmission lens (transmission efficiency of 87.6%). Conversely, when VO2 enters the metallic state (about 355 K), the MDL has the ability to reflect and polymerize electromagnetic waves and works as a reflection lens (reflection efficiency of 85.1%). The dielectric waveguide and gap-surface plasmon (GSP) theories are used in transmission and reflection directions, respectively. In order to satisfy the coverage of the phase gradient in the range of 2π in both cases, we set the antenna as a nanopillar with a high aspect ratio. It is notable that, via symmetrical antennas acting in concert with VO2 phase change material, the polarization states of both the incident light and the outgoing light are not changed. This reversible tuning will play a significant role in the fields of imaging, optical storage devices, communication, sensors, etc.

Preparation of RHA-Paraffin Phase Change Materials

2011 ◽  
Vol 399-401 ◽  
pp. 1156-1159
Author(s):  
Jun Wang ◽  
Bao Guo Ma ◽  
Jian Liang Zhang ◽  
Wen Yang
Keyword(s):  
Phase Transition ◽  
Phase Change ◽  
Phase Change Material ◽  
Rice Husk ◽  
Absorption Rate ◽  
Phase Change Materials ◽  
Rice Husk Ash ◽  
Dsc Analysis ◽  
Change Material ◽  
Enthalpy Of Phase Transition

In this paper, a kind of RHA-paraffin phase change material was prepared, and the SEM was used for observing its internal morphologies, DSC analysis was carried out for detecting its temperature and enthalpy of phase transition. The results showed that rice husk ash have a greater absorption rate for paraffin; a large number of pores of the RHA were filled by paraffin in the RHA-paraffin phase change material, and the absorption rate can reach 53.5%.

scholarly journals A Parametric Investigation on Energy-Saving Effect of Solar Building Based on Double Phase Change Material Layer Wallboard

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Xiaoxiao Tong ◽  
Xingyao Xiong
Keyword(s):  
Phase Transition ◽  
Phase Change ◽  
Phase Change Material ◽  
Wall Temperature ◽  
Parametric Investigation ◽  
Double Phase ◽  
Phase Transition Temperatures ◽  
Saving Effect ◽  
Change Material ◽  
Inside Wall

In order to further understand the thermal performance of the double phase change material (PCM) layer wallboard, the wallboard model was established and a comprehensively numerical parametric investigation was carried out. The variation laws of inner wall temperature rise and the heat flux transferred under different phase transition temperatures and thermal conductivities are presented in detail. The main results show that the temperature of the inside wall for case 2 can be reduced by about 1.5 K further compared to that for case 1. About 83% of the heat transferred from the outside is absorbed by the PCM layer in case 2. Reducing the phase transition temperature of the PCM layer can decrease the inside wall temperature to a certain extent in the period of high temperature. The utilization of double PCM layers shows much more performance compared to that of the single PCM layer case, and the temperature of the inside wall can be reduced by 2 K further.

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