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Investigation of the Hybrid Structures based on Carbon Materials for Solar Steam Generation

Simayee, Maedeh | 2023

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 56044 (48)
  4. University: Sharif University of Technology
  5. Department: Institute for Nanoscience and Nanotechnology
  6. Advisor(s): Irajizad, Azam; Esfandiar, Ali
  7. Abstract:
  8. Two-dimensional nanostructures can significantly absorb solar irradiation, due to diverse energy levels, large effective surfaces, layered and porous structures with adjustable physical and chemical properties. Mono and multilayers of graphene, as the first isolated 2D materials with special band-structure of a zero-band gap, along with impressive optical properties, tunable light interaction, and adjustable optical properties by chemical doping or structural defects, have great potential for the next generation of nanophotonic devices. So, graphene is an appropriate candidate for absorption, frequent reflection, and energy conversion of electromagnetic waves at the frequency range of the solar spectrum for solar evaporation and water purification. The practical purpose of this project is to design and introduction of new hybrid nanostructures from photothermal absorbers for the acceleration of water evaporation through solar energy to achieve desalination applications. Therefore, in this research, finding new nanostructures based on carbon materials such as graphene and carbon black, relying on thermal vibrations mechanism for heat generation in organic molecules, is considered. To preserve the surface heat, polyurethane foam as a self-floating thermal insulator is used at the bottom of the absorber. Due to the hydrophobicity of the foam, continuous water supply to the evaporation surface is carried out by a fabric cover around it. Applied coatings on the fabric as a flexible, accessible, and washable substrate are exposed to saline water (3.5 wt%, NaCl) under irradiation for one hour. Next, to improve absorbency and light-to-heat conversion efficiency, other photothermal materials, including Cu and black TiO2 NPs, were used to study the plasmonic effect and non-radiative relaxation, respectively. In addition, the amount of surface water, to achieve a balance between mass and heat, was adjusted via stitched foam with cotton yarns (Jellyfish-like structure). The capillary forces in the yarns, with the suspended end in the container, enable continuous water transportation to the evaporation surface. Ordinary methods, such as SEM, EDX, XRD, FT-IR, Raman, XPS, and so on were employed for specimen characterization. The evaporation performance of the samples under natural and setup radiation was evaluated by recording the water weight loss, temperature fluctuations, and conversion efficiency along with the self-recovery property against salt aggregations. The best performance between carbon, metal, semiconductor, and metal/semiconductor-based materials with the increase of 2.28, 2.79, 2.95, and 3.13 times compared to the control sample belonged to the hybrid one with an efficiency of >98.5%. According to the ICP results on the collected vapors, the desalination performance of all samples has an optimal value of more than 99%. So, the hybrid coated sample with superior antifouling properties, through salt creeping on the container walls instead of fabric, and maximum evaporation enhancement promises a remarkable potential to address the global challenge of water limitation
  9. Keywords:
  10. Graphene ; Carbon Black ; Cotton Fabric ; Photothermal Material ; Solar Evaporation ; Black Titanium Oxide ; Plasmonic Effects ; Graphene Plasmonics Properties ; Two-Dimensional Nanomaterials

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