Yazar "Ashraf, Humza" seçeneğine göre listele

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    Biowaste valorization into valuable nanomaterials: Synthesis of green carbon nanodots and anode material for lithium-ion batteries from watermelon seeds
    (Elsevier Ltd, 2024) Ashraf, Humza; Karahan, Billur Deniz
    In this study, a solid biowaste watermelon seed is introduced for the first time as an alternative precursor for the production of fluorescent carbon nanodots and nanostructured activated carbon. Firstly, the seeds are carburized and then activated by using KOH after the ball milling process. The activated carbon is used as anode material in lithium-ion batteries and exhibits ?360 mAh g ? 1 capacity after the 200th cycle, with a coulombic efficiency of 98%. Additionally, carbon dots are fabricated by hydrothermally treating carburized seeds at different conditions. The obtained carbon dots show a remarkable fluorescence effect at 458 nm (when excited at 365 nm) and have the potential to be used in biomedical applications. The results show that by means of proper material selection and process design, low carbon footprint nanomaterials suitable for use in various applications can be synthesized successfully from organic wastes.
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    Cryo-assisted nitrogen treatment for the fabrication of nanoengineered, mixed transition metal oxide anode from ınorganic domestic waste, for lithium-ion batteries
    (2024) Ashraf, Humza; Karahan, Billur Deniz
    A novel method for the fabrication of nanoengineered, mixed transition metal oxide anode active material is proposed based on implementing liquid nitrogen treatment during the chemical precipitation process, for the first time in open literature. Such interference in the precipitation is believed to change the surface energy of the nuclei leading to differentiation in the growth process. To exemplify this hypothesis with an environmentally friendly approach, kitchen scourer pads, an existing waste, are used as a starting material instead of using a mixture of primary quality metals’ salts. Therefore, in this study, firstly, an optimization is realized to leach the scouring pad with 100% efficiency. Then, by applying a conventional chemical precipitation to this leachate at pH 5.5, Sample 1-P is produced. Herein, innovatively liquid nitrogen treatment is carried out during the chemical precipitation to produce Sample 2-P. Lastly, these precipitates (Samples 1-P, 2-P) are calcinated in the air to form mixed transition metal oxide powders: Samples 1 and 2, respectively. Structural, chemical, and morphological characterizations are carried out to examine the effect of liquid nitrogen treatment on the powders’ properties. To discuss the effect of nitrogen treatment on the electrochemical performances of the anode active materials (Sample 1 and Sample 2), galvanostatic tests are realized. The results show that Sample 2 demonstrates a higher 1st discharge capacity (1352 mAh/g) and retains 62% of its performance after 200 cycles when 50 mA/g current load is applied. Moreover, this electrode delivers around 500 mAh/g at 1 A/g current load. The remarkable cycle performance of Sample 2 is believed to be related to the superior chemical, structural, and physical properties of the electrode active material. Graphical Abstract: (Figure presented.)
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    Electroless nickel-plated ferrochromium flue dust as anode material for lithium-ion batteries
    (Springer, 2023) Ashraf, Humza; Karahan, Billur Deniz
    The flue dust of the electric arc furnace is a waste product generated in the production of ferrochromium alloy. It consists of various transition metal oxides and silicates. In this study, innovatively, it is proposed to apply electroless nickel plating and then high-energy ball milling to evaluate the waste in question as electrode material in battery technology. Therefore, the flue dust (sample 1), the electroless nickel-plated (sample 2), and the electroless nickel-plated then high-energy ball-milled (sample 3) flue dust are characterized morphologically, structurally, and chemically. Cyclic voltammetry is performed to investigate their lithiation mechanisms. Negative symmetric cells are assembled to record their impedances. The SEM, XRD, and XPS results of sample 3 show that a nickel layer is successfully deposited on the flue dust. Electrochemical test results reveal that due to the catalytic effect and electrochemically inactive behavior (versus lithium) of nickel, the electrode/electrolyte interface reactions are modified, electron transfer along the electrode is facilitated and electrochemical induced agglomeration in cycling is prevented. Moreover, decreasing the particle size by ball milling increases the stress accommodation ability of the electrode. Hence, crack formation and delamination of sample 3 are also restricted.
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    Synthesis of green anode material for lithium-ion battery from orthodontic waste by fuzzy logic
    (2025) Ashraf, Humza; Karahan, Billur Deniz; Şen, Zekai
    For the fabrication of green batteries, instead of synthesizing the electrode materials from high-purity metal powders via primary production methods, it is of great importance to design and produce an electrode material by recovering valuable elements from existing wastes. In this article, for the first time in open literature, an electrode active material was fabricated from biomedical waste by using a combination of leaching and hydrothermal methods. Once 100% leaching efficiency was achieved, an optimization was realized in the hydrothermal parameters (filling ratios, time, and temperatures) to fabricate spherically shaped metal oxide powders with 150 nm particle size. Innovatively, fuzzy logic modeling was used for refinement of parameters. Subsequently, three verification experiments were realized at optimum conditions, defined by fuzzy logic. The repeatability as well as the accuracy of the model was confirmed. In the meantime, analysis of variance (ANOVA) technique was applied for identification of the most effective parameter for the fabrication of powders in hydrothermal conditions. A detailed mechanistic analysis about the formation of particles was also realized. Finally, the possible use of this metal oxide powder as an anode material was evaluated galvanostatically and potentiostatically. The electrode delivered a higher capacity than graphite and achieved 100-cycle tests with success. The presented approach was anticipated to constitute an example for the future, as it brought an effective perspective to material scientists about the valorization of biomedical waste in high value-added applications such as energy storage devices.