Nano-materials for Environmental Cleanup and Solar Energy Applications
Dr. Matiullah Khan,
Department of Physics, Kohat University of Science and Technology (KUST), Pakistan.
IAP Physics Seminar Series will occur on Tuesday 21 May 24, at 15:15 at the UM6P campus (Ryad 8, 1st floor).
Abstract:
Visible light photocatalysis have been considered to be an alternate solution for environmental pollution and energy crises. Nano-materials such as Titanium dioxide (TiO2) could be utilized due to its high electron-hole pair life time and oxidative power. With band gap engineering, its intrinsic band gap could be tailored to harvest the major part of solar spectrum. Different parameters were changed to investigate the effect of band gap on the photodegradation properties of Nano-materials. In the doping techniques, selection of proper dopant is a major step in this process. Dopant ionic radii, oxidation state, valences are the crucial factors that should be taken into account before synthesizing a doped sample. The synthesized nano-materials could be for photo-degradation of inorganic materials in air and water. Two parallel approaches are used to deal with this problem. The first deals with the synthesis and characterization of novel visible light active nan-materials for photoelectrochemical applications. The second field of interest is the ab-initio calculations for investigating the structural, electronic and optical properties of various semiconductors. Density Functional Theory (DFT) based calculations are widely used for band gap engineering of new materials for energy related applications. The used of calculations prior to experiment would reduce the cost of experiments and will predict the best possible materials for photoelectrochemical applications….To improve the efficiency and longevity of gas turbine engine, the metallic components of the gas turbine engine should be insulated from the hot gas stream. The current state of art material is the thermal barrier coatings (TBC) that are widely used to protect the metallic components of engine from the high temperature. It is useful for increasing the life time and operating temperature of the engine. Low thermal conductivity and good strain tolerance are basic prerequisite for the thermal barrier coatings. TBC mainly consists of four layers; metal substrate, bond coat, ceramic top coat, and thermally grown oxide (TGO) layer between the top and bond coat. Among the different materials, zirconia (ZrO2) is considered to be a suitable material for the top coat of TBC. The selection of ZrO2 is due to its excellent properties like low coefficient of thermal expansion, high thermal stability, low thermal conductivity and high erosion resistance. Fracture toughness and fracture strength of ZrO2 could be improved by tetragonal to monoclinic phase transformation. The reducing grain growth and stability of zirconia is improved by doping yttria (Y2O3) in ZrO2. Zirconia (ZrO2) stabilized by yttria (Y2O3) is widely utilized as a top coat material in the thermal barrier coatings (TBC). The excellent properties of yttria stabilized zirconia (YSZ) such as fracture toughness and relatively high thermal expansion coefficient widens its applications spectrum. The special arrangement of the metal substrate, bond coat, ceramic top coat, and the thermally grown oxide (TGO) layer in TBC reduces the components temperature by 100-300℃. Academia as well as industry is taking keen interest to understand the structure of YSZ and improve the thermal insulation capability. Engine with improved durability are possible to get YSZ coatings with lower thermal conductivity that provide higher temperature drop across the coatings. Both experimental and theoretical approaches are applied to understand the improved properties of the prepared coatings.
Biography:
Matiullah Khan, PhD in Materials Science and Engineering at the University of Science and Technology Beijing (USTB), China. his research interest moves around the synthesis of novel photoactive materials for photoelectrochemical applications. Currently, he’s an Associate Professor of Physics at Kohat University of Science and Technology where he’s teaching Physics to the graduate and undergraduate students.
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