Researcher:
Jahangiri, Hadi

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Hadi

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Jahangiri

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Jahangiri, Hadi

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2021 - 20233

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Researcher Of Publications: search.filters.isAuthorOfPublication.ff03305e-c327-4ddc-b4cc-9525d3b9cba6

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    Femtosecond laser-mediated preparation of HfNbTaTiZr refractory high-entropy alloy nanoparticles for photothermal therapy applications: influence of solvent and fluence
    (Elsevier, 2023) Guo, Sheng; Department of Physics; Department of Physics; N/A; Department of Chemistry; Department of Chemistry; N/A; N/A; Sennaroğlu, Alphan; Morova, Yağız; Alamdari, Armin Asghari; Eroğlu, Zafer; Metin, Önder; Motallebzadeh, Amir; Jahangiri, Hadi; Faculty Member; Researcher; PhD Student; Researcher; Faculty Member; Researcher; Researcher; Department of Physics; Department of Chemistry; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); College of Sciences; College of Sciences; Graduate School of Sciences and Engineering; College of Sciences; College of Sciences; N/A; N/A; 23851; N/A; N/A; N/A; 46962; N/A; N/A
    Nanoparticles (NPs) have become popular photothermal therapy (PTT) photosensitizers because they can be targeted to cancer tissues and deliver a chemotherapeutic medication. Pulsed laser ablation in liquid media (PLAL) can produce stable colloidal NPs without any stabilizing agents. The stability, size distribution, and morphology of the produced colloids are influenced by the nature of NPs, laser parameters such as laser power, laser frequency repetition, ablation rate, and the specific ionic effects from the solvent. In this work, HfNbTaTiZr refractory high entropy alloy (RHEA) NPs were prepared by PLAL method in different solvents, including distilled water, ethanol, and n-hexane. The experiments were performed by irradiating a HfNbTaTiZr target with a femtosecond laser outputting 120-fs pulse at varying levels of ablation fluence (0.1, 0.16, 0.23 mJ/cm2). The elemental and structural characteristics of the prepared HfNbTaTiZr NPs were elucidated by using several advanced analytical techniques. The XRD pattern of NPs revealed that the liquid medium significantly affects the type of crystallized phases and the surface composition. The surface composition was studied by XPS, indicating that the fabricated NPs were oxidized. SEM and TEM analysis have evidenced the generation of NPs with an average diameter of less than 50 nm. The results revealed that the higher ablation fluence resulted in the formation of NPs with a larger average diameter. The highest intrinsic photothermal conversion efficiency and 12 °C time-dependent solvent heating produced in ethanol at 640 nm irradiation after 20 min were demonstrated.
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    Femtosecond laser written continuous-wave Nd3+:BaY2F8 waveguide laser at 1.3 mu m
    (Elsevier, 2022) Di Lieto, Alberto; Cittadino, Giovanni; Damiano, Eugenio; Tonelli, Mauro; Department of Physics; N/A; N/A; N/A; Department of Physics; Morova, Yağız; Morova, Berna; Jahangiri, Hadi; Toker, Işınsu Baylam; Sennaroğlu, Alphan; Researcher; Researcher; Researcher; PhD Student; Faculty Member; Department of Physics; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); College of Sciences; N/A; N/A; Graduate School of Sciences and Engineering; College of Sciences; N/A; N/A; N/A; N/A; 23851
    We experimentally demonstrate, for the first time to our knowledge, robust operation of a Nd3(+:)BaY(2)F(8) waveguide laser at 1.3 mu m without any parasitic lasing at any other wavelength. The best power performance was obtained with a depressed cladding waveguide, having a diameter of 70 mu m, which was fabricated by employing femtosecond laser writing. The propagation loss of the waveguide was measured as 0.33 dB/cm at the wavelength of 761 nm. The power performance of the waveguide laser was investigated for E//z and E//y pumping polarizations by using butt-coupled flat resonator mirrors. Higher power performance was obtained for E//z pumping, where the resonator with the 6.2% transmitting output coupler produced 157 mW of continuous-wave output power at 1318 nm with 882 mW of pump power at 800 nm. The measured power slope efficiency was 19% with respect to the incident pump power. By using a different set of cavity optics, 1050-nm lasing performance was also studied, where E//z pumping at 800 nm with the 12% transmitting output coupler yielded 307 mW of output power with 31% slope efficiency. Use of a host medium with relatively low refractive index around 1.5 was instrumental in reducing the facet reflectivity and eliminating the possibility of parasitic lasing at 1.05 mu m during 1.3-mu m lasing.
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    Microstructure development and mechanical performance of Al2CrFeMnTi light-weight high entropy alloy
    (Elsevier, 2021) Yilmaz, Rifat; Bayrak, Kubra Gurcan; Yu, Feng; Ghadbeigi, Hassan; Ayas, Erhan; N/A; Jahangiri, Hadi; Alamdari, Armin Asghari; Motallebzadeh, Amir; Researcher; PhD Student; Researcher; N/A; Graduate School of Sciences and Engineering; N/A; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştirmalari Merkezi (KUYTAM); N/A; N/A; N/A
    Light-weight high entropy alloys (LWHEAs) are considered equiatomic or near-equiatomic alloys consisting of at least five elements. Low-density elements, like Al and Ti, are the key constituents in designing these alloys so that features such as reduced overall density and improved mechanical properties are achieved. A new LWHEAs (Al2CrFeMnTi) is designed, where mechanical alloying followed by subsequent casting is carried out for a successful synthesis. As a result, chemically homogenous samples are fabricated that possess a multiphase microstructure of BCC solid solution, C-14 Laves phase, and L-21 precipitates in the as-cast state. Although the presence of intermetallic phases results in high hardness characterized by nanoindentation tests, the produced alloy demonstrates some level of ductility before failure. This behavior could be linked to the minimal strain hardening of the BCC phase. Additionally, the formation of ultra-fine L-21 precipitates within the BCC phase is contributed to the high strength and the modified strain observed in the alloy.